Sample records for warm dust component

  1. Common Warm Dust Temperatures Around Main Sequence Stars

    NASA Technical Reports Server (NTRS)

    Morales, Farisa; Rieke, George; Werner, Michael; Stapelfeldt, Karl; Bryden, Geoffrey; Su, Kate

    2011-01-01

    We compare the properties of warm dust emission from a sample of main-sequence A-type stars (B8-A7) to those of dust around solar-type stars (F5-KO) with similar Spitzer Space Telescope Infrared Spectrograph/MIPS data and similar ages. Both samples include stars with sources with infrared spectral energy distributions that show evidence of multiple components. Over the range of stellar types considered, we obtain nearly the same characteristic dust temperatures (∼ 190 K and ∼60 K for the inner and outer dust components, respectively)-slightly above the ice evaporation temperature for the inner belts. The warm inner dust temperature is readily explained if populations of small grains are being released by sublimation of ice from icy planetesimals. Evaporation of low-eccentricity icy bodies at ∼ 150 K can deposit particles into an inner/warm belt, where the small grains are heated to dust Temperatures of -190 K. Alternatively, enhanced collisional processing of an asteroid belt-like system of parent planetesimals just interior to the snow line may account for the observed uniformity in dust temperature. The similarity in temperature of the warmer dust across our B8-KO stellar sample strongly suggests that dust-producing planetesimals are not found at similar radial locations around all stars, but that dust production is favored at a characteristic temperature horizon.

  2. Does warm debris dust stem from asteroid belts?

    NASA Astrophysics Data System (ADS)

    Geiler, Fabian; Krivov, Alexander V.

    2017-06-01

    Many debris discs reveal a two-component structure, with a cold outer and a warm inner component. While the former are likely massive analogues of the Kuiper belt, the origin of the latter is still a matter of debate. In this work, we investigate whether the warm dust may be a signature of asteroid belt analogues. In the scenario tested here, the current two-belt architecture stems from an originally extended protoplanetary disc, in which planets have opened a gap separating it into the outer and inner discs which, after the gas dispersal, experience a steady-state collisional decay. This idea is explored with an analytic collisional evolution model for a sample of 225 debris discs from a Spitzer/IRS catalogue that are likely to possess a two-component structure. We find that the vast majority of systems (220 out of 225, or 98 per cent) are compatible with this scenario. For their progenitors, original protoplanetary discs, we find an average surface density slope of -0.93 ± 0.06 and an average initial mass of (3.3^{+0.4}_{-0.3})× 10^{-3} solar masses, both of which are in agreement with the values inferred from submillimetre surveys. However, dust production by short-period comets and - more rarely - inward transport from the outer belts may be viable, and not mutually excluding, alternatives to the asteroid belt scenario. The remaining five discs (2 per cent of the sample: HIP 11486, HIP 23497, HIP 57971, HIP 85790, HIP 89770) harbour inner components that appear inconsistent with dust production in an 'asteroid belt.' Warm dust in these systems must either be replenished from cometary sources or represent an aftermath of a recent rare event, such as a major collision or planetary system instability.

  3. Exozodiacal clouds: hot and warm dust around main sequence stars

    NASA Astrophysics Data System (ADS)

    Kral, Quentin; Krivov, Alexander V.; Defrère, Denis; van Lieshout, Rik; Bonsor, Amy; Augereau, Jean-Charles; Thébault, Philippe; Ertel, Steve; Lebreton, Jérémy; Absil, Olivier

    2017-04-01

    A warm/hot dust component (at temperature $>$ 300K) has been detected around $\\sim$ 20% of stars. This component is called "exozodiacal dust" as it presents similarities with the zodiacal dust detected in our Solar System, even though its physical properties and spatial distribution can be significantly different. Understanding the origin and evolution of this dust is of crucial importance, not only because its presence could hamper future detections of Earth-like planets in their habitable zones, but also because it can provide invaluable information about the inner regions of planetary systems. In this review, we present a detailed overview of the observational techniques used in the detection and characterisation of exozodiacal dust clouds ("exozodis") and the results they have yielded so far, in particular regarding the incidence rate of exozodis as a function of crucial parameters such as stellar type and age, or the presence of an outer cold debris disc. We also present the important constraints that have been obtained, on dust size distribution and spatial location, by using state-of-the-art radiation transfer models on some of these systems. Finally, we investigate the crucial issue of how to explain the presence of exozodiacal dust around so many stars (regardless of their ages) despite the fact that such dust so close to its host star should disappear rapidly due to the coupled effect of collisions and stellar radiation pressure. Several potential mechanisms have been proposed to solve this paradox and are reviewed in detail in this paper. The review finishes by presenting the future of this growing field.

  4. Some Coolness on Martian Global Warming and Reflections on the Role of Surface Dust

    NASA Astrophysics Data System (ADS)

    Richardson, M. I.; Vasavada, A. R.

    2007-12-01

    Recent comparisons of global snap-shots of Mars' surface taken by the Viking and Mars Global Surveyor (MGS) cameras have been used to suggest that Mars has darkened, and hence has warmed, between the 1970's and 1990's. While this conclusion is not supported by more quantitative analysis of albedo data, the idea of Martian darkening and warming has found its way into the terrestrial climate change debate. Through blogs and other opinion pieces it has been used, both amusingly and disturbingly, to argue that Mars' apparent natural warming should alleviate our concerns about anthropomorphic climate change on Earth. Relating planetary research results to terrestrial analogs is instructive and promotes public understanding, but this example provides a cautionary tale of misinterpretation in this age of politicized science. The dust cycle is the dominant short-term component of the Martian climate. The atmosphere is strongly forced via dust's modification of atmospheric radiative heating rates, while dust loading displays dramatic interannual variability, from background opacity to aperiodic global dust storms. Until recently, the atmospheric component of the dust cycle was better documented than the surface component (which on Mars can be gauged via albedo). But now thanks to the combination of regional imaging, spot thermal infrared spectra, and spot short-wavelength photometry sampled at synoptic time and length scales by MGS, a rich new view of the relationship between specific meteorological phenomena and the patterns of surface dust is emerging. Seasonal cap winds, local, regional, and global dust storms, and monsoonal circulations all redistribute surface dust on large spatial scales, while dust devils are surprisingly shown to be insignificant. Rapid and widespread albedo modification is accomplished by storms that darken relatively bright regions through dust removal, and deposit dust upon largely dust free areas, brightening them. (It is not possible with

  5. What Sets the Radial Locations of Warm Debris Disks?

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ballering, Nicholas P.; Rieke, George H.; Su, Kate Y. L.

    The architectures of debris disks encode the history of planet formation in these systems. Studies of debris disks via their spectral energy distributions (SEDs) have found infrared excesses arising from cold dust, warm dust, or a combination of the two. The cold outer belts of many systems have been imaged, facilitating their study in great detail. Far less is known about the warm components, including the origin of the dust. The regularity of the disk temperatures indicates an underlying structure that may be linked to the water snow line. If the dust is generated from collisions in an exo-asteroid belt,more » the dust will likely trace the location of the water snow line in the primordial protoplanetary disk where planetesimal growth was enhanced. If instead the warm dust arises from the inward transport from a reservoir of icy material farther out in the system, the dust location is expected to be set by the current snow line. We analyze the SEDs of a large sample of debris disks with warm components. We find that warm components in single-component systems (those without detectable cold components) follow the primordial snow line rather than the current snow line, so they likely arise from exo-asteroid belts. While the locations of many warm components in two-component systems are also consistent with the primordial snow line, there is more diversity among these systems, suggesting additional effects play a role.« less

  6. Lunar Dust Simulant in Mechanical Component Testing - Paradigm and Practicality

    NASA Technical Reports Server (NTRS)

    Jett, T.; Street, K.; Abel, P.; Richmond, R.

    2008-01-01

    Due to the uniquely harsh lunar surface environment, terrestrial test activities may not adequately represent abrasive wear by lunar dust likely to be experienced in mechanical systems used in lunar exploration. Testing to identify potential moving mechanism problems has recently begun within the NASA Engineering and Safety Center Mechanical Systems Lunar Dust Assessment activity in coordination with the Exploration Technology and Development Program Dust Management Project, and these complimentary efforts will be described. Specific concerns about differences between simulant and lunar dust, and procedures for mechanical component testing with lunar simulant will be considered. In preparing for long term operations within a dusty lunar environment, the three fundamental approaches to keeping mechanical equipment functioning are dust avoidance, dust removal, and dust tolerance, with some combination of the three likely to be found in most engineering designs. Methods to exclude dust from contact with mechanical components would constitute mitigation by dust avoidance, so testing seals for dust exclusion efficacy as a function of particle size provides useful information for mechanism design. Dust of particle size less than a micron is not well documented for impact on lunar mechanical components. Therefore, creating a standardized lunar dust simulant in the particulate size range of ca. 0.1 to 1.0 micrometer is useful for testing effects on mechanical components such as bearings, gears, seals, bushings, and other moving mechanical assemblies. Approaching actual wear testing of mechanical components, it is beneficial to first establish relative wear rates caused by dust on commonly used mechanical component materials. The wear mode due to dust within mechanical components, such as abrasion caused by dust in grease(s), needs to be considered, as well as the effects of vacuum, lunar thermal cycle, and electrostatics on wear rate.

  7. Integrated approach towards understanding interactions of mineral dust aerosol with warm clouds

    NASA Astrophysics Data System (ADS)

    Kumar, Prashant

    2011-12-01

    Mineral dust is ubiquitous in the atmosphere and represents a dominant type of particulate matter by mass. Dust particles can serve as cloud condensation nuclei (CCN), giant CCN (GCCN), or ice nuclei (IN), thereby, affecting cloud microphysics, albedo, and lifetime. Despite its well-recognized importance, assessments of dust impacts on clouds and climate remain highly uncertain. This thesis addresses the role of dust as CCN and GCCN with the goal of improving our understanding of dust-warm cloud interactions and their representation in climate models. Most studies to date focus on the soluble fraction of aerosol particles when describing cloud droplet nucleation, and overlook the interactions of the hydrophilic insoluble fraction with water vapor. A new approach to include such interactions (expressed by the process of water vapor adsorption) is explored, by combining multilayer Frenkel-Halsey-Hill (FHH) physical adsorption isotherm and curvature (Kelvin) effects. The importance of adsorption activation theory (FHH-AT) is corroborated by measurements of CCN activity of mineral aerosols generated from clays, calcite, quartz, and desert soil samples from Northern Africa, East Asia/China, and Northern America. A new aerosol generation setup for CCN measurements was developed based on a dry generation technique capable of reproducing natural dust aerosol emission. Based on the dependence of critical supersaturation with particle dry diameter, it is found that the FHH-AT is a better framework for describing fresh (and unprocessed) dust CCN activity than the classical Kohler theory (KT). Ion Chromatography (IC) measurements performed on fresh regional dust samples indicate negligible soluble fraction, and support that water vapor adsorption is the prime source of CCN activity in the dust. CCN measurements with the commonly used wet generated mineral aerosol (from atomization of a dust aqueous suspension) are also carried out. Results indicate that the method is subject

  8. KP Equation in a Three-Dimensional Unmagnetized Warm Dusty Plasma with Variable Dust Charge

    NASA Astrophysics Data System (ADS)

    El-Shorbagy, Kh. H.; Mahassen, Hania; El-Bendary, Atef Ahmed

    2017-12-01

    In this work, we investigate the propagation of three-dimensional nonlinear dust-acoustic and dust-Coulomb waves in an unmagnetized warm dusty plasma consisting of electrons, ions, and charged dust particles. The grain charge fluctuation is incorporated through the current balance equation. Using the perturbation method, a Kadomtsev-Petviashvili (KP) equation is obtained. It has been shown that the charge fluctuation would modify the wave structures, and the waves in such systems are unstable due to high-order long wave perturbations.

  9. A Submillimeter Continuum Survey of Local Dust-obscured Galaxies

    NASA Astrophysics Data System (ADS)

    Lee, Jong Chul; Hwang, Ho Seong; Lee, Gwang-Ho

    2016-12-01

    We conduct a 350 μm dust continuum emission survey of 17 dust-obscured galaxies (DOGs) at z = 0.05-0.08 with the Caltech Submillimeter Observatory (CSO). We detect 14 DOGs with S 350 μm = 114-650 mJy and signal-to-noise > 3. By including two additional DOGs with submillimeter data in the literature, we are able to study dust content for a sample of 16 local DOGs, which consist of 12 bump and four power-law types. We determine their physical parameters with a two-component modified blackbody function model. The derived dust temperatures are in the range 57-122 K and 22-35 K for the warm and cold dust components, respectively. The total dust mass and the mass fraction of the warm dust component are 3-34 × 107 M ⊙ and 0.03%-2.52%, respectively. We compare these results with those of other submillimeter-detected infrared luminous galaxies. The bump DOGs, the majority of the DOG sample, show similar distributions of dust temperatures and total dust mass to the comparison sample. The power-law DOGs show a hint of smaller dust masses than other samples, but need to be tested with a larger sample. These findings support that the reason DOGs show heavy dust obscuration is not an overall amount of dust content, but probably the spatial distribution of dust therein.

  10. A SUBMILLIMETER CONTINUUM SURVEY OF LOCAL DUST-OBSCURED GALAXIES

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Lee, Jong Chul; Hwang, Ho Seong; Lee, Gwang-Ho, E-mail: jclee@kasi.re.kr

    We conduct a 350 μ m dust continuum emission survey of 17 dust-obscured galaxies (DOGs) at z = 0.05–0.08 with the Caltech Submillimeter Observatory (CSO). We detect 14 DOGs with S{sub 350μm} = 114–650 mJy and signal-to-noise > 3. By including two additional DOGs with submillimeter data in the literature, we are able to study dust content for a sample of 16 local DOGs, which consist of 12 bump and four power-law types. We determine their physical parameters with a two-component modified blackbody function model. The derived dust temperatures are in the range 57–122 K and 22–35 K for themore » warm and cold dust components, respectively. The total dust mass and the mass fraction of the warm dust component are 3–34 × 10{sup 7} M {sub ⊙} and 0.03%–2.52%, respectively. We compare these results with those of other submillimeter-detected infrared luminous galaxies. The bump DOGs, the majority of the DOG sample, show similar distributions of dust temperatures and total dust mass to the comparison sample. The power-law DOGs show a hint of smaller dust masses than other samples, but need to be tested with a larger sample. These findings support that the reason DOGs show heavy dust obscuration is not an overall amount of dust content, but probably the spatial distribution of dust therein.« less

  11. Dust Properties of Local Dust-obscured Galaxies with the Submillimeter Array

    NASA Astrophysics Data System (ADS)

    Hwang, Ho Seong; Andrews, Sean M.; Geller, Margaret J.

    2013-11-01

    We report Submillimeter Array observations of the 880 μm dust continuum emission for four dust-obscured galaxies (DOGs) in the local universe. Two DOGs are clearly detected with S ν(880 μm) =10-13 mJy and S/N > 5, but the other two are not detected with 3σ upper limits of S ν(880 μm) =5-9 mJy. Including an additional two local DOGs with submillimeter data from the literature, we determine the dust masses and temperatures for six local DOGs. The infrared luminosities and dust masses for these DOGs are in the ranges of 1.2-4.9 × 1011(L ⊙) and 4-14 × 107(M ⊙), respectively. The dust temperatures derived from a two-component modified blackbody function are 23-26 K and 60-124 K for the cold and warm dust components, respectively. Comparison of local DOGs with other infrared luminous galaxies with submillimeter detections shows that the dust temperatures and masses do not differ significantly among these objects. Thus, as argued previously, local DOGs are not a distinctive population among dusty galaxies, but simply represent the high-end tail of the dust obscuration distribution.

  12. Lunar dust transport and potential interactions with power system components

    NASA Technical Reports Server (NTRS)

    Katzan, Cynthia M.; Edwards, Jonathan L.

    1991-01-01

    The lunar surface is covered by a thick blanket of fine dust. This dust may be readily suspended from the surface and transported by a variety of mechanisms. As a consequence, lunar dust can accumulate on sensitive power components, such as photovoltaic arrays and radiator surfaces, reducing their performance. In addition to natural mechanisms, human activities on the Moon will disturb significant amounts of lunar dust. Of all the mechanisms identified, the most serious is rocket launch and landing. The return of components from the Surveyor 3 provided a rare opportunity to observe the effects of the nearby landing of the Apollo 12 Lunar Module. The evidence proved that significant dust accumulation occurred on the Surveyor at a distance of 155 m. From available information on particle suspension and transport mechanisms, a series of models was developed to predict dust accumulation as a function of distance from the lunar module. The accumulation distribution was extrapolated to a future Lunar Lander scenario. These models indicate that accumulation is expected to be substantial even as far as 2 km from the landing site. Estimates of the performance penalties associated with lunar dust coverage and photovoltaic arrays are presented. Because of the lunar dust adhesive and cohesive properties, the most practical dust defensive strategy appears to be the protection of sensitive components from the arrival of lunar dust by location, orientation, or barriers.

  13. Principle Component Analysis of the Evolution of the Saharan Air Layer and Dust Transport: Comparisons between a Model Simulation and MODIS Retrievals

    NASA Technical Reports Server (NTRS)

    Wong, S.; Colarco, P. R.; Dessler, A.

    2006-01-01

    The onset and evolution of Saharan Air Layer (SAL) episodes during June-September 2002 are diagnosed by applying principal component analysis to the NCEP reanalysis temperature anomalies at 850 hPa, where the largest SAL-induced temperature anomalies are located. The first principal component (PC) represents the onset of SAL episodes, which are associated with large warm anomalies located at the west coast of Africa. The second PC represents two opposite phases of the evolution of the SAL. The positive phase of the second PC corresponds to the southwestward extension of the warm anomalies into the tropical-subtropical North Atlantic Ocean, and the negative phase corresponds to the northwestward extension into the subtropical to mid-latitude North Atlantic Ocean and the southwest Europe. A dust transport model (CARMA) and the MODIS retrievals are used to study the associated effects on dust distribution and deposition. The positive (negative) phase of the second PC corresponds to a strengthening (weakening) of the offshore flows in the lower troposphere around 10deg - 20degN, causing more (less) dust being transported along the tropical to subtropical North Atlantic Ocean. The variation of the offshore flow indicates that the subseasonal variation of African Easterly Jet is associated with the evolution of the SAL. Significant correlation is found between the second PC time series and the daily West African monsoon index, implying a dynamical linkage between West African monsoon and the evolution of the SAL and Saharan dust transport.

  14. DUST PROPERTIES OF LOCAL DUST-OBSCURED GALAXIES WITH THE SUBMILLIMETER ARRAY

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hwang, Ho Seong; Andrews, Sean M.; Geller, Margaret J., E-mail: hhwang@cfa.harvard.edu, E-mail: sandrews@cfa.harvard.edu, E-mail: mgeller@cfa.harvard.edu

    We report Submillimeter Array observations of the 880 μm dust continuum emission for four dust-obscured galaxies (DOGs) in the local universe. Two DOGs are clearly detected with S{sub ν}(880 μm) =10-13 mJy and S/N > 5, but the other two are not detected with 3σ upper limits of S{sub ν}(880 μm) =5-9 mJy. Including an additional two local DOGs with submillimeter data from the literature, we determine the dust masses and temperatures for six local DOGs. The infrared luminosities and dust masses for these DOGs are in the ranges of 1.2-4.9 × 10{sup 11}(L{sub ☉}) and 4-14 × 10{sup 7}(M{submore » ☉}), respectively. The dust temperatures derived from a two-component modified blackbody function are 23-26 K and 60-124 K for the cold and warm dust components, respectively. Comparison of local DOGs with other infrared luminous galaxies with submillimeter detections shows that the dust temperatures and masses do not differ significantly among these objects. Thus, as argued previously, local DOGs are not a distinctive population among dusty galaxies, but simply represent the high-end tail of the dust obscuration distribution.« less

  15. Enrichment of Inorganic Martian Dust Simulant with Carbon Component can Provoke Neurotoxicity

    NASA Astrophysics Data System (ADS)

    Pozdnyakova, Natalia; Pastukhov, Artem; Dudarenko, Marina; Borysov, Arsenii; Krisanova, Natalia; Nazarova, Anastasia; Borisova, Tatiana

    2017-02-01

    Carbon is the most abundant dust-forming element in the interstellar medium. Tremendous amount of meteorites containing plentiful carbon and carbon-enriched dust particles have reached the Earth daily. National Institute of Health panel accumulates evidences that nano-sized air pollution components may have a significant impact on the central nervous system (CNS) in health and disease. During inhalation, nano-/microsized particles are efficiently deposited in nasal, tracheobronchial, and alveolar regions and can be transported to the CNS. Based on above facts, here we present the study, the aims of which were: 1) to upgrade inorganic Martian dust simulant derived from volcanic ash (JSC-1a/JSC, ORBITEC Orbital Technologies Corporation, Madison, Wisconsin) by the addition of carbon components, that is, nanodiamonds and carbon dots; 2) to analyse acute effects of upgraded simulant on key characteristics of synaptic neurotransmission; and 3) to compare above effects with those of inorganic dust and carbon components per se. Acute administration of carbon-containing Martian dust analogues resulted in a significant decrease in transporter-mediated uptake of L-[14C]glutamate (the major excitatory neurotransmitter) and [3H]GABA (the main inhibitory neurotransmitter) by isolated rat brain nerve terminals. The extracellular level of both neurotransmitters increased in the presence of carbon-containing Martian dust analogues. These effects were associated with action of carbon components of upgraded Martian dust simulant, but not with its inorganic constituent. This fact indicates that carbon component of native Martian dust can have deleterious effects on extracellular glutamate and GABA homeostasis in the CNS, and so glutamate- and GABA-ergic neurotransmission disballansing exitation and inhibition.

  16. util_2comp: Planck-based two-component dust model utilities

    NASA Astrophysics Data System (ADS)

    Meisner, Aaron

    2014-11-01

    The util_2comp software utilities generate predictions of far-infrared Galactic dust emission and reddening based on a two-component dust emission model fit to Planck HFI, DIRBE and IRAS data from 100 GHz to 3000 GHz. These predictions and the associated dust temperature map have angular resolution of 6.1 arcminutes and are available over the entire sky. Implementations in IDL and Python are included.

  17. Carbonaceous Components in the Comet Halley Dust

    NASA Technical Reports Server (NTRS)

    Fomenkova, M. N.; Chang, S.; Mukhin, L. M.

    1994-01-01

    Cometary grains containing large amounts of carbon and/or organic matter (CHON) were discovered by in situ measurements of comet Halley dust composition during VEGA and GIOTTO flyby missions. In this paper, we report the classification of these cometary, grains by means of cluster analysis, discuss the resulting compositional groups, and compare them with substances observed or hypothesized in meteorites, interplanetary dust particles, and the interstellar medium. Grains dominated by carbon and/or organic matter (CHON grains) represent approx. 22% of the total population of measured cometary dust particles. They, usually contain a minor abundance of rock-forming elements as well. Grains having organic material are relatively more abundant in the vicinity of the nucleus than in the outer regions of the coma, which suggests decomposition of the organics in the coma environment. The majority of comet Halley organic particles are multicomponent mixtures of carbon phases and organic compounds. Possibly, the cometary CHON grains may be related to kerogen material of an interstellar origin in carbonaceous meteorites. Pure carbon grains, hydrocarbons and polymers of cyanopolyynes, and multi-carbon monoxides are present in cometary dust as compositionally simple and distinctive components among a variety of others. There is no clear evidence of significant presence of pure formaldehyde or HCN polymers in Halley dust particles. The diversity of types of cometary organic compounds is consistent with the inter-stellar dust model of comets and probably reflects differences in composition of precursor dust. Preservation of this heterogeneity among submicron particles suggest the gentle formation of cometary, nucleus by aggregation of interstellar dust in the protosolar nebula without complete mixing or chemical homogenization at the submicron level.

  18. Integrative Analysis of Desert Dust Size and Abundance Suggests Less Dust Climate Cooling

    NASA Technical Reports Server (NTRS)

    Kok, Jasper F.; Ridley, David A.; Zhou, Qing; Miller, Ron L.; Zhao, Chun; Heald, Colette L.; Ward, Daniel S.; Albani, Samuel; Haustein, Karsten

    2017-01-01

    Desert dust aerosols affect Earths global energy balance through interactions with radiation, clouds, and ecosystems. But the magnitudes of these effects are so uncertain that it remains unclear whether atmospheric dust has a net warming or cooling effect on global climate. Consequently, it is still uncertain whether large changes in atmospheric dust loading over the past century have slowed or accelerated anthropogenic climate change, and the climate impact of possible future alterations in dust loading is similarly disputed. Here we use an integrative analysis of dust aerosol sizes and abundance to constrain the climatic impact of dust through direct interactions with radiation. Using a combination of observational, experimental, and model data, we find that atmospheric dust is substantially coarser than represented in current climate models. Since coarse dust warms global climate, the dust direct radiative effect (DRE) is likely less cooling than the 0.4 W m superscript 2 estimated by models in a current ensemble. We constrain the dust DRE to -0.20 (-0.48 to +0.20) W m superscript 2, which suggests that the dust DRE produces only about half the cooling that current models estimate, and raises the possibility that dust DRE is actually net warming the planet.

  19. Evaluating the Dominant Components of Warming in Pliocene Climate Simulations

    NASA Technical Reports Server (NTRS)

    Hill, D. J.; Haywood, A. M.; Lunt, D. J.; Hunter, S. J.; Bragg, F. J.; Contoux, C.; Stepanek, C.; Sohl, L.; Rosenbloom, N. A.; Chan, W.-L.; hide

    2014-01-01

    The Pliocene Model Intercomparison Project (PlioMIP) is the first coordinated climate model comparison for a warmer palaeoclimate with atmospheric CO2 significantly higher than pre-industrial concentrations. The simulations of the mid-Pliocene warm period show global warming of between 1.8 and 3.6 C above pre-industrial surface air temperatures, with significant polar amplification. Here we perform energy balance calculations on all eight of the coupled ocean-atmosphere simulations within PlioMIP Experiment 2 to evaluate the causes of the increased temperatures and differences between the models. In the tropics simulated warming is dominated by greenhouse gas increases, with the cloud component of planetary albedo enhancing the warming in most of the models, but by widely varying amounts. The responses to mid-Pliocene climate forcing in the Northern Hemisphere midlatitudes are substantially different between the climate models, with the only consistent response being a warming due to increased greenhouse gases. In the high latitudes all the energy balance components become important, but the dominant warming influence comes from the clear sky albedo, only partially offset by the increases in the cooling impact of cloud albedo. This demonstrates the importance of specified ice sheet and high latitude vegetation boundary conditions and simulated sea ice and snow albedo feedbacks. The largest components in the overall uncertainty are associated with clouds in the tropics and polar clear sky albedo, particularly in sea ice regions. These simulations show that albedo feedbacks, particularly those of sea ice and ice sheets, provide the most significant enhancements to high latitude warming in the Pliocene.

  20. "CHON" particles: The interstellar component of cometary dust

    NASA Technical Reports Server (NTRS)

    Lien, David J.

    1998-01-01

    Interstellar dust is characterized by strong absorption in the ultraviolet and the mid-IR. Current models of interstellar dust are based on three chemically distinct components: a form of carbon (usually graphite), a silicate, and a blend of polycyclic aromatic hydrocarbons or other carbonaceous material. Previous work using effective medium theories to understand the optical properties of cometary dust suggested that an amalgam of materials could reproduce the observed interstellar and cometary dust features. Recently, Lawler and Brownlee (1992) re-analyzed the PIA and PUMA-1 data sets from the Giotto flyby of P/Halley and discovered that the so-called "CHON" particles were actually composed of a blend of carbon-bearing and silicon-bearing materials. Based on effective medium theories, the absorption spectrum of such a material would display the spectral features of each of the components - strong UV absorption from the carbonaceous component and strong absorption in the IR from the silicate component. To test this idea, vapor-deposited samples were created using two different deposition techniques: sputtering with an argon RF magnetron and deposition from an argon plasma torch. Two different compositions were tested: a blend of graphite and silica in a 7:1 ratio and an amalgam of materials whose approximate composition matches the "CHON"-silicate abundances for the uncompressed PIA data set of Lawler and Brownlee: graphite, iron oxide, magnesium oxide, ammonium sulfate, calcium carbonate, and silica in mass ratios of 6:4.3:4:2.2:1:9. The samples were finely ground and pressed into 2" diameter disks using a 40 ton press. In all, four different experiments were performed: one with each of the compositions (C:SiO and "CHON") in both the RF magnetron and the plasma torch chambers. The RF magnetron created a uniform dark thin film on the substrate surface, and the plasma torch created a coating of small (<100 micron) diameter grey particles. The spectra of all four

  1. Dust Acoustic Wave Excitation in a Plasma with Warm Dust

    NASA Astrophysics Data System (ADS)

    Rosenberg, M.; Thomas, E., Jr.; Marcus, L.; Fisher, R.; Williams, J. D.; Merlino, R. L.

    2008-11-01

    Measurements of the dust acoustic wave dispersion relation in dusty plasmas formed in glow discharges at the University of Iowa [1] and Auburn University [2] have shown the importance of finite dust temperature effects. The effect of dust grains with large thermal speeds was taken into account using kinetic theory of the ion-dust streaming instability [3]. The results of analytic and numerical calculations of the dispersion relation based on the kinetic theory will be presented and compared with the experimental results. [1] E. Thomas, Jr., R. Fisher, and R. L. Merlino, Phys. Plasmas 14, 123701 (2007). [2] J. D. Williams, E. Thomas Jr., and L. Marcus, Phys. Plasmas 15, 043704 (2008). [3] M. Rosenberg, E. Thomas Jr., and R. L. Merlino, Phys. Plasmas 15, 073701 (2008).

  2. Dust around the Cool Component of D-Type Symbiotic Binaries

    NASA Astrophysics Data System (ADS)

    Jurkic, Tomislav; Kotnik-Karuza, Dubravka

    2018-04-01

    D type symbiotic binaries are an excellent astrophysical laboratory for investigation of the dust properties and dust formation under the influence of theMira stellar wind and nova activity and of the mass loss and mass transfer between components in such a widely separated system. We present a study of the properties of circumstellar dust in symbiotic Miras by use of long-term near-IR photometry and colour indices. The published JHKL magnitudes of o Ceti, RX Pup, KM Vel, V366 Car, V835 Cen, RR Tel, HM Sge and R Aqr have been collected, analyzed and corrected for short-term variations caused by Mira pulsations. Assuming spherical temperature distribution of the dust in the close neighbourhood of the Mira, the DUSTY code was used to solve the radiative transfer in order to determine the dust temperature and its properties in each particular case. Common dust properties of the symbiotic Miras have been found, suggesting similar conditions in the condensation region of the studied symbiotic Miras. Silicate dust with the inner dust shell radius determined by the dust condensation and with the dust temperature of 900-1200 K can fully explain the observed colour indices. R Aqr is an exception and showed lower dust temperature of 650 K. Obscuration events visible in light curves can be explained by variable dust optical depth with minimal variations of other dust properties. More active symbioticMiras that underwent recent nova outbursts showed higher dust optical depths and larger maximum grain sizes of the order of μm, which means that the post-nova activity could stimulate the dust formation and the grain growth. Optically thicker dust shells and higher dust condensation temperatures have been found in symbiotic Miras compared to their single counterparts, suggesting different conditions for dust production.

  3. Two-component Thermal Dust Emission Model: Application to the Planck HFI Maps

    NASA Astrophysics Data System (ADS)

    Meisner, Aaron M.; Finkbeiner, Douglas P.

    2014-06-01

    We present full-sky, 6.1 arcminute resolution maps of dust optical depth and temperature derived by fitting the Finkbeiner et al. (1999) two-component dust emission model to the Planck HFI and IRAS 100 micron maps. This parametrization of the far infrared thermal dust SED as the sum of two modified blackbodies serves as an important alternative to the commonly adopted single modified blackbody dust emission model. We expect our Planck-based maps of dust temperature and optical depth to form the basis for a next-generation, high-resolution extinction map which will additionally incorporate small-scale detail from WISE imaging.

  4. The twofold debris disk around HD 113766 A. Warm and cold dust as seen with VLTI/MIDI and Herschel/PACS

    NASA Astrophysics Data System (ADS)

    Olofsson, J.; Henning, Th.; Nielbock, M.; Augereau, J.-C.; Juhàsz, A.; Oliveira, I.; Absil, O.; Tamanai, A.

    2013-03-01

    Context. Warm debris disks are a sub-sample of the large population of debris disks, and display excess emission in the mid-infrared. Around solar-type stars, very few objects (~2% of all debris disks) show emission features in mid-IR spectroscopic observations that are attributed to small, warm silicate dust grains. The origin of this warm dust could be explained either by a recent catastrophic collision between several bodies or by transport from an outer belt similar to the Kuiper belt in the solar system. Aims: We present and analyze new far-IR Herschel/PACS photometric observations, supplemented by new and archival ground-based data in the mid-IR (VLTI/MIDI and VLT/VISIR), for one of these rare systems: the 10-16 Myr old debris disk around HD 113766 A. We improve an existing model to account for these new observations. Methods: We implemented the contribution of an outer planetesimal belt in the Debra code, and successfully used it to model the spectral energy distribution (SED) as well as complementary observations, notably MIDI data. We better constrain the spatial distribution of the dust and its composition. Results: We underline the limitations of SED modeling and the need for spatially resolved observations. We improve existing models and increase our understanding of the disk around HD 113766 A. We find that the system is best described by an inner disk located within the first AU, well constrained by the MIDI data, and an outer disk located between 9-13 AU. In the inner dust belt, our previous finding of Fe-rich crystalline olivine grains still holds. We do not observe time variability of the emission features over at least an eight-year time span in an environment subjected to strong radiation pressure. Conclusions: The time stability of the emission features indicates that μm-sized dust grains are constantly replenished from the same reservoir, with a possible depletion of sub- μm-sized grains. We suggest that the emission features may arise from

  5. Dust devils on Mars

    NASA Technical Reports Server (NTRS)

    Thomas, P. G.; Gierasch, P.

    1985-01-01

    Large columns of dust have been discovered rising above plains on Mars. The storms are probably analogous to terrestrial dust devils, but their size indicates that they are more similar to tornadoes in intensity. They occur at locations where the soil has been strongly warmed by the Sun, and there the surface is smooth and fine grained. These are the same conditions that favor dust devils on Earth. Warm gas from the lowest atmospheric layer converges and rises in a thin column, with intense swirl developing at the edge of the column. In one area a mosaic of Viking images shows 97 vortices in a three day period. This represents a density of vortices of about one in each 900 square kilometers. Thus, these dust devils may be important in moving dust or starting over dust storms.

  6. Heterogeneous chemistry of atmospheric mineral dust particles and their resulting cloud-nucleation properties

    NASA Astrophysics Data System (ADS)

    Sullivan, Ryan Christopher

    Mineral dust particles are a major component of tropospheric aerosol mass and affect regional and global atmospheric chemistry and climate. Dust particles experience heterogeneous reactions with atmospheric gases that alter the gas and particle-phase chemistry. These in turn influence the warm and cold cloud nucleation ability and optical properties of the dust particles. This dissertation investigates the atmospheric chemistry of mineral dust particles and their role in warm cloud nucleation through a combination of synergistic field measurements, laboratory experiments, and theoretical modeling. In-situ measurements made with a single-particle mass spectrometer during the ACE-Asia field campaign in 2001 provide the motivation for this work. The observed mixing state of the individual ambient particles with secondary organic and inorganic components is described in Chapter 2. A large Asian dust storm occurred during the campaign and produced dramatic changes in the aerosol's composition and mixing state. The effect of particle size and mineralogy on the atmospheric processing of individual dust particles is explored in Chapters 3 & 4. Sulfate was found to accumulate preferentially in submicron iron and aluminosilicate-rich dust particles, while nitrate and chloride were enriched in supermicron calcite-rich dust. The mineral dust (and sea salt particles) were also enriched in oxalic acid, the dominant component of water soluble organic carbon. Chapter 5 explores the roles of gas-phase photochemistry and partitioning of the diacids to the alkaline particles in producing this unique behavior. The effect of the dust's mixing state with secondary organic and inorganic components on the dust particles' solubility, hygroscopicity, and thus warm cloud nucleation properties is explored experimentally and theoretically in Chapter 6. Cloud condensation nucleation (CCN) activation curves revealed that while calcium nitrate and calcium chloride particles were very hygroscopic

  7. Exposure to grain dust and microbial components in the Norwegian grain and compound feed industry.

    PubMed

    Halstensen, Anne Straumfors; Heldal, Kari Kulvik; Wouters, Inge M; Skogstad, Marit; Ellingsen, Dag G; Eduard, Wijnand

    2013-11-01

    The aim of this study was to extensively characterize grain workers' personal exposure during work in Norwegian grain elevators and compound feed mills, to identify differences in exposures between the workplaces and seasons, and to study the correlations between different microbial components. Samples of airborne dust (n = 166) were collected by full-shift personal sampling during work in 20 grain elevators and compound feed mills during one autumn season and two winter seasons. The personal exposure to grain dust, endotoxins, β-1→3-glucans, bacteria, and fungal spores was quantified. Correlations between dust and microbial components and differences between workplaces and seasons were investigated. Determinants of endotoxin and β-1→3-glucan exposure were evaluated by linear mixed-effect regression modeling. The workers were exposed to an overall geometric mean of 1.0mg m(-3) inhalable grain dust [geometric standard deviation (GSD) = 3.7], 628 endotoxin units m(-3) (GSD = 5.9), 7.4 µg m(-3) of β-1→3-glucan (GSD = 5.6), 21 × 10(4) bacteria m(-3) (GSD = 7.9) and 3.6 × 10(4) fungal spores m(-3) (GSD = 3.4). The grain dust exposure levels were similar across workplaces and seasons, but the microbial content of the grain dust varied substantially between workplaces. Exposure levels of all microbial components were significantly higher in grain elevators compared with all other workplaces. The grain dust exposure was significantly correlated (Pearson's r) with endotoxin (rp = 0.65), β-1→3-glucan (rp = 0.72), bacteria (rp = 0.44) and fungal spore (rp = 0.48) exposure, whereas the explained variances were strongly dependent on the workplace. Bacteria, grain dust, and workplace were important determinants for endotoxin exposure, whereas fungal spores, grain dust, and workplace were important determinants for β-1→3-glucan exposure. Although the workers were exposed to a relatively low mean dust level, the microbial exposure was high. Furthermore, the

  8. ALMA Maps of Dust and Warm Dense Gas Emission in the Starburst Galaxy IC 5179

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zhao Yinghe; Lu, Nanyao; Xu, C. Kevin

    We present our high-resolution (0.″15 × 0.″13, ∼34 pc) observations of the CO (6−5) line emission, which probes the warm and dense molecular gas, and the 434 μ m dust continuum emission in the nuclear region of the starburst galaxy IC 5179, conducted with the Atacama Large Millimeter Array (ALMA). The CO (6−5) emission is spatially distributed in filamentary structures with many dense cores and shows a velocity field that is characteristic of a circumnuclear rotating gas disk, with 90% of the rotation speed arising within a radius of ≲150 pc. At the scale of our spatial resolution, the COmore » (6−5) and dust emission peaks do not always coincide, with their surface brightness ratio varying by a factor of ∼10. This result suggests that their excitation mechanisms are likely different, as further evidenced by the southwest to northeast spatial gradient of both CO-to-dust continuum ratio and Pa- α equivalent width. Within the nuclear region (radius ∼ 300 pc) and with a resolution of ∼34 pc, the CO line flux (dust flux density) detected in our ALMA observations is 180 ± 18 Jy km s{sup −1} (71 ± 7 mJy), which accounts for 22% (2.4%) of the total value measured by Herschel .« less

  9. Eolian Dust and the Origin of Sedimentary Chert

    USGS Publications Warehouse

    Cecil, C. Blaine

    2004-01-01

    This paper proposes an alternative model for the primary source of silica contained in bedded sedimentary chert. The proposed model is derived from three principal observations as follows: (1) eolian processes in warm-arid climates produce copious amounts of highly reactive fine-grained quartz particles (dust), (2) eolian processes in warm-arid climates export enormous quantities of quartzose dust to marine environments, and (3) bedded sedimentary cherts generally occur in marine strata that were deposited in warm-arid paleoclimates where dust was a potential source of silica. An empirical integration of these observations suggests that eolian dust best explains both the primary and predominant source of silica for most bedded sedimentary cherts.

  10. ALMA Maps of Dust and Warm Dense Gas Emission in the Starburst Galaxy IC 5179

    NASA Astrophysics Data System (ADS)

    Zhao, Yinghe; Lu, Nanyao; Díaz-Santos, Tanio; Xu, C. Kevin; Gao, Yu; Charmandaris, Vassilis; van der Werf, Paul; Zhang, Zhi-Yu; Cao, Chen

    2017-08-01

    We present our high-resolution (0.″15 × 0.″13, ˜34 pc) observations of the CO (6-5) line emission, which probes the warm and dense molecular gas, and the 434 μm dust continuum emission in the nuclear region of the starburst galaxy IC 5179, conducted with the Atacama Large Millimeter Array (ALMA). The CO (6-5) emission is spatially distributed in filamentary structures with many dense cores and shows a velocity field that is characteristic of a circumnuclear rotating gas disk, with 90% of the rotation speed arising within a radius of ≲150 pc. At the scale of our spatial resolution, the CO (6-5) and dust emission peaks do not always coincide, with their surface brightness ratio varying by a factor of ˜10. This result suggests that their excitation mechanisms are likely different, as further evidenced by the southwest to northeast spatial gradient of both CO-to-dust continuum ratio and Pa-α equivalent width. Within the nuclear region (radius ˜ 300 pc) and with a resolution of ˜34 pc, the CO line flux (dust flux density) detected in our ALMA observations is 180 ± 18 Jy km s-1 (71 ± 7 mJy), which accounts for 22% (2.4%) of the total value measured by Herschel. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.

  11. Computer Simulation of Material Flow in Warm-forming Bimetallic Components

    NASA Astrophysics Data System (ADS)

    Kong, T. F.; Chan, L. C.; Lee, T. C.

    2007-05-01

    Bimetallic components take advantage of two different metals or alloys so that their applicable performance, weight and cost can be optimized. However, since each material has its own flow properties and mechanical behaviour, heterogeneous material flows will occur during the bimetal forming process. Those controls of process parameters are relatively more complicated than forming single metals. Most previous studies in bimetal forming have focused mainly on cold forming, and less relevant information about the warm forming has been provided. Indeed, changes of temperature and heat transfer between two materials are the significant factors which can highly influence the success of the process. Therefore, this paper presents a study of the material flow in warm-forming bimetallic components using finite-element (FE) simulation in order to determine the suitable process parameters for attaining the complete die filling. A watch-case-like component made of stainless steel (AISI-316L) and aluminium alloy (AL-6063) was used as the example. The warm-forming processes were simulated with the punch speeds V of 40, 80, and 120 mm/s and the initial temperatures of the stainless steel TiSS of 625, 675, 725, 775, 825, 875, 925, 975, and 1025 °C. The results showed that the AL-6063 flowed faster than the AISI-316L and so the incomplete die filling was only found in the AISI-316L region. A higher TiSS was recommended to avoid incomplete die filling. The reduction of V is also suggested because this can save the forming energy and prevent the damage of tooling. Eventually, with the experimental verification, the results from the simulation were in agreement with those of the experiments. On the basis of the results of this study, engineers can gain a better understanding of the material flow in warm-forming bimetallic components, and be able to determine more efficiently the punch speed and initial material temperature for the process.

  12. Tracing ram-pressure stripping with warm molecular hydrogen emission

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sivanandam, Suresh; Rieke, Marcia J.; Rieke, George H., E-mail: sivanandam@dunlap.utoronto.ca

    We use the Spitzer Infrared Spectrograph to study four infalling cluster galaxies with signatures of ongoing ram-pressure stripping. H{sub 2} emission is detected in all four, and two show extraplanar H{sub 2} emission. The emission usually has a warm (T ∼ 115-160 K) and a hot (T ∼ 400-600 K) component that is approximately two orders of magnitude less massive than the warm one. The warm component column densities are typically 10{sup 19} to 10{sup 20} cm{sup –2} with masses of 10{sup 6} to 10{sup 8} M {sub ☉}. The warm H{sub 2} is anomalously bright compared with normal star-formingmore » galaxies and therefore may be excited by ram-pressure. In the case of CGCG 97-073, the H{sub 2} is offset from the majority of star formation along the direction of the galaxy's motion in the cluster, suggesting that it is forming in the ram-pressure wake of the galaxy. Another galaxy, NGC 4522, exhibits a warm H{sub 2} tail approximately 4 kpc in length. These results support the hypothesis that H{sub 2} within these galaxies is shock-heated from the interaction with the intracluster medium. Stripping of dust is also a common feature of the galaxies. For NGC 4522, where the distribution of dust at 8 μm is well resolved, knots and ripples demonstrate the turbulent nature of the stripping process. The Hα and 24 μm luminosities show that most of the galaxies have star-formation rates comparable to similar mass counterparts in the field. Finally, we suggest a possible evolutionary sequence primarily related to the strength of ram-pressure that a galaxy experiences to explain the varied results observed in our sample.« less

  13. Isolating the anthropogenic component of Arctic warming

    DOE PAGES

    Chylek, Petr; Hengartner, Nicholas; Lesins, Glen; ...

    2014-05-28

    Structural equation modeling is used in statistical applications as both confirmatory and exploratory modeling to test models and to suggest the most plausible explanation for a relationship between the independent and the dependent variables. Although structural analysis cannot prove causation, it can suggest the most plausible set of factors that influence the observed variable. Here, we apply structural model analysis to the annual mean Arctic surface air temperature from 1900 to 2012 to find the most effective set of predictors and to isolate the anthropogenic component of the recent Arctic warming by subtracting the effects of natural forcing and variabilitymore » from the observed temperature. We also find that anthropogenic greenhouse gases and aerosols radiative forcing and the Atlantic Multidecadal Oscillation internal mode dominate Arctic temperature variability. Finally, our structural model analysis of observational data suggests that about half of the recent Arctic warming of 0.64 K/decade may have anthropogenic causes.« less

  14. AN INVESTIGATION OF THE DUST CONTENT IN THE GALAXY PAIR NGC 1512/1510 FROM NEAR-INFRARED TO MILLIMETER WAVELENGTHS

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Liu Guilin; Calzetti, Daniela; Yun, Min S.

    2010-03-15

    We combine new ASTE/AzTEC 1.1 mm maps of the galaxy pair NGC 1512/1510 with archival Spitzer IRAC and MIPS images covering the wavelength range 3.6-160 {mu}m from the SINGS project. The availability of the 1.1 mm map enables us to measure the long-wavelength tail of the dust emission in each galaxy, and in sub-galactic regions in NGC 1512, and to derive accurate dust masses. The two galaxies form a pair consisting of a large, high-metallicity spiral (NGC 1512) and a low-metallicity, blue compact dwarf (NGC 1510), which we use to compare similarities and contrast differences. Using the models of Drainemore » and Li, the derived total dust masses are (2.4 {+-} 0.6) x 10{sup 7} M {sub sun} and (1.7 {+-} 3.6) x 10{sup 5} M {sub sun} for NGC 1512 and NGC 1510, respectively. The derived ratio of dust mass to H I gas mass for the galaxy pair, M{sub d}/M{sub H{sub 1}}{approx}0.0034, is much lower (by at least a factor of 3) than expected, as previously found by Draine et al. In contrast, regions within NGC 1512, specifically the central region and the arms, do not show such unusually low M{sub d}/M{sub H{sub 1}} ratios; furthermore, the dust-to-gas ratio is within expectations for NGC 1510. These results suggest that a fraction of the H I included in the determination of the M{sub d}/M{sub H{sub 1}} ratio of the NGC 1512/NGC 1510 pair is not associated with the star-forming disks/regions of either galaxy. Using the dust masses derived from the models of Draine and Li as references, we perform simple two-temperature modified blackbody fits to the far-infrared/millimeter data of the two galaxies and the sub-regions of NGC 1512, in order to derive and compare the dust masses associated with warm and cool dust temperature components. As generally expected, the warm dust temperature of the low-metallicity, low-mass NGC 1510 (T{sub w} {approx} 36 K) is substantially higher than the corresponding warm temperature of the high-metallicity spiral NGC 1512 (T{sub w} {approx} 24 K

  15. Interstellar and Ejecta Dust in the Cas A Supernova Remnant

    NASA Technical Reports Server (NTRS)

    Arendt, Richard G.; Dwek, Eli; Kober, Gladys; Rho, Jonghee; Hwang, Una

    2013-01-01

    The ejecta of the Cas A supernova remnant has a complex morphology, consisting of dense fast-moving line emitting knots and diffuse X-ray emitting regions that have encountered the reverse shock, as well as more slowly expanding, unshocked regions of the ejecta. Using the Spitzer 5-35 micron IRS data cube, and Herschel 70, 100, and 160 micron PACS data, we decompose the infrared emission from the remnant into distinct spectral components associated with the different regions of the ejecta. Such decomposition allows the association of different dust species with ejecta layers that underwent distinct nuclear burning histories, and determination of the dust heating mechanisms. Our decomposition identified three characteristic dust spectra. The first, most luminous one, exhibits strong emission features at approx. 9 and 21 micron, and a weaker 12 micron feature, and is closely associated with the ejecta knots that have strong [Ar II] 6.99 micron and [Ar III] 8.99 micron emission lines. The dust features can be reproduced by magnesium silicate grains with relatively low MgO-to-SiO2 ratios. A second, very different dust spectrum that has no indication of any silicate features, is best fit by Al2O3 dust and is found in association with ejecta having strong [Ne II] 12.8 micron and [Ne III] 15.6 micron emission lines. A third characteristic dust spectrum shows features that best matched by magnesium silicates with relatively high MgO-to-SiO2 ratio. This dust is primarily associated with the X-ray emitting shocked ejecta and the shocked interstellar/circumstellar material. All three spectral components include an additional featureless cold dust component of unknown composition. Colder dust of indeterminate composition is associated with [Si II] 34.8 micron emission from the interior of the SNR, where the reverse shock has not yet swept up and heated the ejecta. The dust mass giving rise to the warm dust component is about approx. 0.1solar M. However, most of the dust mass

  16. Infrared Luminosities and Dust Properties of z ≈ 2 Dust-obscured Galaxies

    NASA Astrophysics Data System (ADS)

    Bussmann, R. S.; Dey, Arjun; Borys, C.; Desai, V.; Jannuzi, B. T.; Le Floc'h, E.; Melbourne, J.; Sheth, K.; Soifer, B. T.

    2009-11-01

    We present SHARC-II 350 μm imaging of twelve 24 μm bright (F 24 μm > 0.8 mJy) Dust-Obscured Galaxies (DOGs) and Combined Array for Research in Millimeter-wave Astronomy (CARMA) 1 mm imaging of a subset of two DOGs. These objects are selected from the Boötes field of the NOAO Deep Wide-Field Survey. Detections of four DOGs at 350 μm imply infrared (IR) luminosities which are consistent to within a factor of 2 of expectations based on a warm-dust spectral energy distribution (SED) scaled to the observed 24 μm flux density. The 350 μm upper limits for the 8 non-detected DOGs are consistent with both Mrk 231 and M82 (warm-dust SEDs), but exclude cold dust (Arp 220) SEDs. The two DOGs targeted at 1 mm were not detected in our CARMA observations, placing strong constraints on the dust temperature: T dust > 35-60 K. Assuming these dust properties apply to the entire sample, we find dust masses of ≈3 × 108 M sun. In comparison to other dusty z ~ 2 galaxy populations such as submillimeter galaxies (SMGs) and other Spitzer-selected high-redshift sources, this sample of DOGs has higher IR luminosities (2 × 1013 L sun versus 6 × 1012 L sun for the other galaxy populations) that are driven by warmer dust temperatures (>35-60 K versus ~30 K) and lower inferred dust masses (3 × 108 M sun versus 3 × 109 M sun). Wide-field Herschel and Submillimeter Common-User Bolometer Array-2 surveys should be able to detect hundreds of these power-law-dominated DOGs. We use the existing Hubble Space Telescope and Spitzer/InfraRed Array Camera data to estimate stellar masses of these sources and find that the stellar to gas mass ratio may be higher in our 24 μm bright sample of DOGs than in SMGs and other Spitzer-selected sources. Although much larger sample sizes are needed to provide a definitive conclusion, the data are consistent with an evolutionary trend in which the formation of massive galaxies at z ~ 2 involves a submillimeter bright, cold-dust, and star

  17. INFRARED LUMINOSITIES AND DUST PROPERTIES OF z approx 2 DUST-OBSCURED GALAXIES

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Bussmann, R. S.; Dey, Arjun; Jannuzi, B. T.

    We present SHARC-II 350 mum imaging of twelve 24 mum bright (F{sub 24m}u{sub m} > 0.8 mJy) Dust-Obscured Galaxies (DOGs) and Combined Array for Research in Millimeter-wave Astronomy (CARMA) 1 mm imaging of a subset of two DOGs. These objects are selected from the Booetes field of the NOAO Deep Wide-Field Survey. Detections of four DOGs at 350 mum imply infrared (IR) luminosities which are consistent to within a factor of 2 of expectations based on a warm-dust spectral energy distribution (SED) scaled to the observed 24 mum flux density. The 350 mum upper limits for the 8 non-detected DOGsmore » are consistent with both Mrk 231 and M82 (warm-dust SEDs), but exclude cold dust (Arp 220) SEDs. The two DOGs targeted at 1 mm were not detected in our CARMA observations, placing strong constraints on the dust temperature: T{sub dust} > 35-60 K. Assuming these dust properties apply to the entire sample, we find dust masses of approx3 x 10{sup 8} M{sub sun}. In comparison to other dusty z approx 2 galaxy populations such as submillimeter galaxies (SMGs) and other Spitzer-selected high-redshift sources, this sample of DOGs has higher IR luminosities (2 x 10{sup 13} L{sub sun} versus 6 x 10{sup 12} L{sub sun} for the other galaxy populations) that are driven by warmer dust temperatures (>35-60 K versus approx30 K) and lower inferred dust masses (3 x 10{sup 8} M{sub sun} versus 3 x 10{sup 9} M{sub sun}). Wide-field Herschel and Submillimeter Common-User Bolometer Array-2 surveys should be able to detect hundreds of these power-law-dominated DOGs. We use the existing Hubble Space Telescope and Spitzer/InfraRed Array Camera data to estimate stellar masses of these sources and find that the stellar to gas mass ratio may be higher in our 24 mum bright sample of DOGs than in SMGs and other Spitzer-selected sources. Although much larger sample sizes are needed to provide a definitive conclusion, the data are consistent with an evolutionary trend in which the formation of massive

  18. The Dust Content and Opacity of Actively Star-Forming Galaxies

    NASA Technical Reports Server (NTRS)

    Calzetti, Daniela; Armus, Lee; Bohlin, Ralph C.; Kinney, Anne L.; Koornneef, Jan; Storchi-Bergmann, Thaisa

    2000-01-01

    We present far-infrared (FIR) photometry at 150 and 205 micron(s) of eight low-redshift starburst galaxies obtained with the Infrared Space Observatory (ISO) ISOPHOT. Five of the eight galaxies are detected in both wave bands, and these data are used, in conjunction with IRAS archival photometry, to model the dust emission at lambda approximately greater than 40 microns. The FIR spectral energy distributions (SEDs) are best fitted by a combination of two modified Planck functions, with T approx. 40 - 55 K (warm dust) and T approx. 20-23 K (cool dust) and with a dust emissivity index epsilon = 2. The cool dust can be a major contributor to the FIR emission of starburst galaxies, representing up to 60% of the total flux. This component is heated not only by the general interstellar radiation field, but also by the starburst itself. The cool dust mass is up to approx. 150 times larger than the warm dust mass, bringing the gas-to-dust ratios of the starbursts in our sample close to Milky Way values, once resealed for the appropriate metallicity. The ratio between the total dust FIR emission in the range 1-1000 microns and the IRAS FIR emission in the range 40 - 120 microns is approx. 1.75, with small variations from galaxy to galaxy. This ratio is about 40% larger than previously inferred from data at millimeter wavelengths. Although the galaxies in our sample are generally classified as "UV bright," for four of them the UV energy emerging shortward of 0.2 microns is less than 15% of the FIR energy. On average, about 30% of the bolometric flux is coming out in the UV-to-near-IR wavelength range; the rest is emitted in the FIR. Energy balance calculations show that the FIR emission predicted by the dust reddening of the UV-to-near-IR stellar emission is within a factor of approx. 2 of the observed value in individual galaxies and within 20% when averaged over a large sample. If our sample of local starbursts is representative of high-redshift (z approx. greater than 1

  19. Cosmic dust

    NASA Technical Reports Server (NTRS)

    Brownlee, Donald E.; Sandford, Scott A.

    1992-01-01

    Dust is a ubiquitous component of our galaxy and the solar system. The collection and analysis of extraterrestrial dust particles is important to exobiology because it provides information about the sources of biogenically significant elements and compounds that accumulated in distant regions of the solar nebula and that were later accreted on the planets. The topics discussed include the following: general properties of interplanetary dust; the carbonaceous component of interplanetary dust particles; and the presence of an interstellar component.

  20. Identifying sources of aeolian mineral dust: Present and past

    USGS Publications Warehouse

    Muhs, Daniel R; Prospero, Joseph M; Baddock, Matthew C; Gill, Thomas E

    2014-01-01

    Aeolian mineral dust is an important component of the Earth’s environmental systems, playing roles in the planetary radiation balance, as a source of fertilizer for biota in both terrestrial and marine realms and as an archive for understanding atmospheric circulation and paleoclimate in the geologic past. Crucial to understanding all of these roles of dust is the identification of dust sources. Here we review the methods used to identify dust sources active at present and in the past. Contemporary dust sources, produced by both glaciogenic and non-glaciogenic processes, can be readily identified by the use of Earth-orbiting satellites. These data show that present dust sources are concentrated in a global dust belt that encompasses large topographic basins in low-latitude arid and semiarid regions. Geomorphic studies indicate that specific point sources for dust in this zone include dry or ephemeral lakes, intermittent stream courses, dune fields, and some bedrock surfaces. Back-trajectory analyses are also used to identify dust sources, through modeling of wind fields and the movement of air parcels over periods of several days. Identification of dust sources from the past requires novel approaches that are part of the geologic toolbox of provenance studies. Identification of most dust sources of the past requires the use of physical, mineralogical, geochemical, and isotopic analyses of dust deposits. Physical properties include systematic spatial changes in dust deposit thickness and particle size away from a source. Mineralogy and geochemistry can pinpoint dust sources by clay mineral ratios and Sc-Th-La abundances, respectively. The most commonly used isotopic methods utilize isotopes of Nd, Sr, and Pb and have been applied extensively in dust archives of deep-sea cores, ice cores, and loess. All these methods have shown that dust sources have changed over time, with far more abundant dust supplies existing during glacial periods. Greater dust supplies in

  1. THE COVERING FACTOR OF WARM DUST IN WEAK EMISSION-LINE ACTIVE GALACTIC NUCLEI

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zhang, Xudong; Liu, Yuan, E-mail: zhangxd@ihep.ac.cn, E-mail: liuyuan@ihep.ac.cn

    2016-10-20

    Weak emission-line active galactic nuclei (WLAGNs) are radio-quiet active galactic nuclei (AGNs) that have nearly featureless optical spectra. We investigate the ultraviolet to mid-infrared spectral energy distributions of 73 WLAGNs (0.4 < z < 3) and find that most of them are similar to normal AGNs. We also calculate the covering factor of warm dust of these 73 WLAGNs. No significant difference is indicated by a KS test between the covering factor of WLAGNs and normal AGNs in the common range of bolometric luminosity. The implication for several models of WLAGNs is discussed. The super-Eddington accretion is unlikely to bemore » the dominant reason for the featureless spectrum of a WLAGN. The present results are still consistent with the evolution scenario, i.e., WLAGNs are in a special stage of AGNs.« less

  2. Disentangling the Origin and Heating Mechanism of Supernova Dust: Late-Time Spitzer Spectroscopy of the Type IIn SN 2005ip

    NASA Technical Reports Server (NTRS)

    Fox, Ori D.; Chevalier, Roger A.; Dwek, Eli; Skrutskie, Michael F.; Sugerman, Ben E. K.; Leisenring, Jarron M.

    2010-01-01

    This paper presents late-time near-infrared and Spitzer mid-infrared photometric and spectroscopic observations of warm dust in the Type IIn SN 2005ip in NGC 2906. The spectra show evidence for two dust components with different temperatures. Spanning the peak of the thermal emission, these observations provide strong constraints on the dust mass, temperature, and luminosity, which serve as critical diagnostics for disentangling the origin and heating mechanism of each component. The results suggest the warmer dust has a mass of approx. 5 x 10(exp -4) Solar Mass and originates from newly formed dust in the ejecta, continuously heated by the circumstellar interaction. By contrast, the cooler component likely originates from a circumstellar shock echo that forms from the heating of a large, pre-existing dust shell approx. 0.01 - 0.05 Solar Mass by the late-time circumstellar interaction. The progenitor wind velocity derived from the blue edge of the He I 1.083 micro P Cygni profile indicates a progenitor eruption likely formed this dust shell approx.100 years prior to the supernova explosion, which is consistent with a Luminous Blue Variable (LBV) progenitor star. Subject

  3. Interstellar matter in Shapley-Ames elliptical galaxies. IV. A diffusely distributed component of dust and its effect on colour gradients.

    NASA Astrophysics Data System (ADS)

    Goudfrooij, P.; de Jong, T.

    1995-06-01

    We have investigated IRAS far-infrared observations of a complete, blue magnitude limited sample of 56 elliptical galaxies selected from the Revised Shapley-Ames Catalog. Data from a homogeneous optical CCD imaging survey as well as published X-ray data from the EINSTEIN satellite are used to constrain the infrared data. Dust masses as determined from the IRAS flux densities are found to be roughly an order of magnitude higher than those determined from optical extinction values of dust lanes and patches, in strong contrast with the situation in spiral galaxies. This "mass discrepancy" is found to be independent of the (apparent) inclination of the dust lanes. To resolve this dilemma we postulate that the majority of the dust in elliptical galaxies exists as a diffusely distributed component of dust which is undetectable at optical wavelengths. Using observed radial optical surface brightness profiles, we have systematically investigated possible heating mechanisms for the dust within elliptical galaxies. We find that heating of the dust in elliptical galaxies by the interstellar radiation field is generally sufficient to account for the dust temperatures as indicated by the IRAS flux densities. Collisions of dust grains with hot electrons in elliptical galaxies which are embedded in a hot, X-ray-emitting gas is found to be another effective heating mechanism for the dust. Employing model calculations which involve the transfer of stellar radiation in a spherical distribution of stars mixed with a diffuse distribution of dust, we show that the observed infrared luminosities imply total dust optical depths of the postulated diffusely distributed dust component in the range 0.1<~τ_V_<~0.7 and radial colour gradients 0.03<~{DELTA}(B-I)/{DELTA}log r<~0.25. The observed IRAS flux densities can be reproduced within the 1σ uncertainties in virtually all ellipticals in this sample by this newly postulated dust component, diffusely distributed over the inner few kpc of

  4. Potential climate effect of mineral aerosols over West Africa: Part II—contribution of dust and land cover to future climate change

    NASA Astrophysics Data System (ADS)

    Ji, Zhenming; Wang, Guiling; Yu, Miao; Pal, Jeremy S.

    2018-04-01

    Mineral dust aerosols are an essential component of climate over West Africa, however, little work has been performed to investigate their contributions to potential climate change. A set of regional climate model experiments with and without mineral dust processes and land cover changes is performed to evaluate their climatic effects under the Representative Concentration Pathway 8.5 for two global climate models. Results suggest surface warming to be in the range of 4-8 °C by the end of the century (2081-2100) over West Africa with respect to the present day (1981-2000). The presence of mineral dusts dampens the warming by 0.1-1 °C in all seasons. Accounting for changes in land cover enhances the warming over the north of Sahel and dampens it to the south in spring and summer; however, the magnitudes are smaller than those resulting from dusts. Overall dust loadings are projected to increase, with the greatest increase occurring over the Sahara and Sahel in summer. Accounting for land cover changes tends to reduce dust loadings over the southern Sahel. Future precipitation is projected to decrease by 5-40 % in the western Sahara and Sahel and increase by 10-150 % over the eastern Sahel and Guinea Coast in JJA. A dipole pattern of future precipitation changes is attributed to dust effects, with decrease in the north by 5-20 % and increase by 5-20 % in the south. Future changes in land cover result in a noisy non-significant response with a tendency for slight wetting in MAM, JJA, and SON and drying in DJF.

  5. VizieR Online Data Catalog: Spitzer obs. of warm dust in 83 debris disks (Ballering+, 2017)

    NASA Astrophysics Data System (ADS)

    Ballering, N. P.; Rieke, G. H.; Su, K. Y. L.; Gaspar, A.

    2018-04-01

    For our sample, we used the systems with a warm component found by Ballering+ (2013, J/ApJ/775/55), where "warm" was defined as warmer than 130K. All of these systems have data available from the Multiband Imaging Photometer for Spitzer (MIPS) at 24 and 70um and from the Spitzer Infrared Spectrograph (IRS). The selected 83 targets used for our analysis are listed in Table 1. (5 data files).

  6. Measuring Changes in the Distribution, Mass, and Composition of Dust in the Eruptive LBV Eta Carinae

    NASA Astrophysics Data System (ADS)

    Morris, Patrick

    The luminous, massive binary system eta Carinae is both one of the nearest and most unstable objects in a class of evolved massive stars, near the end of its lifetime before expected destruction in a supernova. It experienced a major outburst in 1843, producing the well-known Homunculus nebula, containing some 15 to 40 Msun in warm ( 170 K) and cool (90-110 K) dust and gas, according to mid-infrared ISO spectroscopy. The location of these thermal components has been uncertain due to large apertures. In Cycle 3 we were approved for 10 hours to use the FORCAST imager with long wavelength filters to better locate and estimate the mass in thermal components of this material that may be resolved, constraining it to the interior regions or bipolar lobes of the Homunculus nebula, or in outer ejecta that would support the hypothesis of a major event prior to the 1843 eruption. About 40% of the program is planned for completion in Cycle 4. We are proposing in Cycle 5 to carry out spectroscopy of the dusty Homunculus nebula at two positions and one reference sky position, using the FORCAST grism with all four filters, in order to characterize changes in mass, composition, and grain properties of especially the cool dust containing >80% of the dust mass, and comparing the results to our spatially integrated ISO spectra taken in 1996/1997, and to 8-13.5 micron data of the warm dust obtained with VLTI/MIDI in 2002/2003 by Chesneau et al. (2005) . These changes may result from the ongoing production of dust in the colliding winds of the 5.5 year period eccentric binary system, particularly during periastron which has occurred three times since 1997. The proposed spectroscopy of especially the cool dust cannot be accomplished from the ground.

  7. Simultaneous UV and X-ray Spectroscopy of the Seyfert 1 Galaxy NGC 5548. I. Evidence for Dust in the UV Absorbers

    NASA Astrophysics Data System (ADS)

    Kraemer, S. B.; Crenshaw, D. M.; Gabel, J. R.; Kaastra, J. S.; Steenbrugge, K.; George, I. M.; Turner, T. J.; Yaqoob, T.; Dunn, J. P.

    2002-12-01

    We present new UV spectra of the nucleus of the Seyfert 1 galaxy NGC 5548, obtained with the Space Telescope Imaging Spectrograph at high spectral resolution (λ /Δ λ = 30,000 - 46,000), simultaneously with Chandra X-ray Observatory spectra. Taking advantage of the low UV continuum and broad emission-line fluxes, we have determined that the deepest UV absorption component covers at least a portion of the inner high-ionization narrow-line region (NLR). Assuming the NLR is fully covered, we find nonunity covering factors in the cores of several components, which increase the column density measurements of N V and C IV by factors of 1.2 to 1.9; however, the revised columns have only a minor effect on the parameters derived from our photoionization models. For the first time, we have simultaneous C IV and N V columns for component 1 (at -1040 km s-1), and find that this component cannot be an X-ray warm absorber, contrary to our previous claim (based on nonsimultaneous observations of N V and C IV). We find that dust-free models of the absorbers severely overpredict the O VI columns previously obtained with the Far Ultraviolet Spectrograph, and present arguments that this is not likely due to variability. However, models that include dust (and thereby heavily deplete carbon) are successful in matching all of the observed ionic columns, and result in substantially lower ionization parameters and total column densities compared to dust-free models. Interestingly, these models yield the exact amount of dust needed to produce the observed reddening of the inner NLR, assuming a Galactic dust to gas ratio. The models produce little O VII and O VIII, indicating that none of the dusty UV absorbers is associated with a classic X-ray warm absorber.

  8. Dust emission in simulated dwarf galaxies using GRASIL-3D

    NASA Astrophysics Data System (ADS)

    Santos-Santos, I. M.; Domínguez-Tenreiro, R.; Granato, G. L.; Brook, C. B.; Obreja, A.

    2017-03-01

    Recent Herschel observations of dwarf galaxies have shown a wide diversity in the shapes of their IR-submm spectral energy distributions as compared to more massive galaxies, presenting features that cannot be explained with the current models. In order to understand the physics driving these differences, we have computed the emission of a sample of simulated dwarf galaxies using the radiative transfer code GRASIL-3D. This code separately treats the radiative transfer in dust grains from molecular clouds and cirri. The simulated galaxies have masses ranging from 10^6-10^9 M_⊙ and have evolved within a Local Group environment by using CLUES initial conditions. We show that their IR band luminosities are in agreement with observations, with their SEDs reproducing naturally the particular spectral features observed. We conclude that the GRASIL-3D two-component model gives a physical interpretation to the emission of dwarf galaxies, with molecular clouds (cirri) as the warm (cold) dust components needed to recover observational data.

  9. A Mid-Summer's Dust Devil

    NASA Technical Reports Server (NTRS)

    2001-01-01

    One objective for the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) in the Extended Mission is to continue looking for changes and dynamic events taking place on the red planet. The feature shown here elicited gasps of excitement among the MOC Operations Staff when it was received in early April 2001.

    The feature is a dust devil. Dust devils are spinning, columnar vortices of wind that move across the landscape, pick up dust, and look somewhat like miniature tornadoes. Dust devils are a common occurrence in dry and desert landscapes on Earth as well as Mars. When this dust devil was spied in Amazonis Planitia on April 10th, the MOC was looking straight down. Usually when the camera is looking down the dust devil will appear as a circular, fuzzy patch with a straight shadow indicating its columnar shape. In this case, however, the dust devil is somewhat curved and kinked--its shape is best seen in the shadow it casts to the right. A thin, light-toned track has been left by the dust devil as it moved eastward across the landscape. Usually, such tracks are darker than the surroundings, in this case the light tone might indicate that the dust being removed by the passing dust devil is darker than the surface underneath the thin veneer of dust.

    Dust devils most typically form when the ground heats up during the day, warming the air immediately above the surface. As the warmed air nearest the surface begins to rise, it spins. The spinning column begins to move across the surface and picks up loose dust (if any is present). The dust makes the vortex visible and gives it the 'dust devil' or tornado-like appearance. This dust devil occurred at an optimal time for dust devils whether on Earth or Mars--around 2 p.m. local time in the middle of Northern Hemisphere Summer. North is up, sunlight illuminates the scene from the left (west), and 500 meters is about 547 yards. The shadow cast by the dust devil goes off the edge of the image, but the length shown

  10. The turbulent life of dust grains in the supernova-driven, multiphase interstellar medium

    NASA Astrophysics Data System (ADS)

    Peters, Thomas; Zhukovska, Svitlana; Naab, Thorsten; Girichidis, Philipp; Walch, Stefanie; Glover, Simon C. O.; Klessen, Ralf S.; Clark, Paul C.; Seifried, Daniel

    2017-06-01

    Dust grains are an important component of the interstellar medium (ISM) of galaxies. We present the first direct measurement of the residence times of interstellar dust in the different ISM phases, and of the transition rates between these phases, in realistic hydrodynamical simulations of the multiphase ISM. Our simulations include a time-dependent chemical network that follows the abundances of H+, H, H2, C+ and CO and take into account self-shielding by gas and dust using a tree-based radiation transfer method. Supernova explosions are injected either at random locations, at density peaks, or as a mixture of the two. For each simulation, we investigate how matter circulates between the ISM phases and find more sizeable transitions than considered in simple mass exchange schemes in the literature. The derived residence times in the ISM phases are characterized by broad distributions, in particular for the molecular, warm and hot medium. The most realistic simulations with random and mixed driving have median residence times in the molecular, cold, warm and hot phase around 17, 7, 44 and 1 Myr, respectively. The transition rates measured in the random driving run are in good agreement with observations of Ti gas-phase depletion in the warm and cold phases in a simple depletion model. ISM phase definitions based on chemical abundance rather than temperature cuts are physically more meaningful, but lead to significantly different transition rates and residence times because there is no direct correspondence between the two definitions.

  11. Niamey Dust Observations

    DOE Data Explorer

    Flynn, Connor

    2008-10-01

    Niamey aerosol are composed of two main components: dust due to the proximity of the Sahara Desert, and soot from local and regional biomass burning. The purpose of this data product is to identify when the local conditions are dominated by the dust component so that the properties of the dust events can be further studied.

  12. Dust Storm Covers Opportunity

    NASA Image and Video Library

    2018-06-10

    This global map of Mars shows a growing dust storm as of June 6, 2018. The map was produced by the Mars Color Imager (MARCI) camera on NASA's Mars Reconnaissance Orbiter spacecraft. The blue dot shows the approximate location of Opportunity. The storm was first detected on June 1. The MARCI camera has been used to monitor the storm ever since. Full dust storms like this one are not surprising, but are infrequent. They can crop up suddenly but last weeks, even months. During southern summer, sunlight warms dust particles, lifting them higher into the atmosphere and creating more wind. That wind kicks up yet more dust, creating a feedback loop that NASA scientists still seek to understand. https://photojournal.jpl.nasa.gov/catalog/PIA22329

  13. Dust Devils Seen by Spirit

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site] Figure 1 Annotated

    At the Gusev site recently, skies have been very dusty, and on its 421st sol (March 10, 2005) NASA's Mars Exploration Rover Spirit spied two dust devils in action. This pair of images is from the rover's rear hazard-avoidance camera. Views of the Gusev landing region from orbit show many dark streaks across the landscape -- tracks where dust devils have removed surface dust to show relatively darker soil below -- but this is the first time Spirit has photographed an active dust devil.

    Scientists are considering several causes of these small phenomena. Dust devils often occur when the Sun heats the surface of Mars. Warmed soil and rocks heat the layer of atmosphere closest to the surface, and the warm air rises in a whirling motion, stirring dust up from the surface like a miniature tornado. Another possibility is that a flow structure might develop over craters as wind speeds increase. As winds pick up, turbulence eddies and rotating columns of air form. As these columns grow in diameter they become taller and gain rotational speed. Eventually they become self-sustaining and the wind blows them down range.

    One sol before this image was taken, power output from Spirit's solar panels went up by about 50 percent when the amount of dust on the panels decreased. Was this a coincidence, or did a helpful dust devil pass over Spirit and lift off some of the dust?

    By comparing the separate images from the rover's different cameras, team members estimate that the dust devils moved about 500 meters (1,640 feet) in the 155 seconds between the navigation camera and hazard-avoidance camera frames; that equates to about 3 meters per second (7 miles per hour). The dust devils appear to be about 1,100 meters (almost three-quarters of a mile) from the rover.

  14. [Characteristics of Chemical Components in PM₂.₅ from the Coal Dust of Power Plants].

    PubMed

    Wang, Yu-xiu; Peng, Lin; Wang, Yan; Zhang, Teng; Liu, Hai-li; Mu, Ling

    2016-01-15

    The ashes under dust catcher of typical power plants in Yangquan was collected and the contents of elements, irons, EC (elemental carbon) and OC (organic carbon) were measured in PM₂. The characteristics of its chemical composition was studied and the degree of similarity of coal dust's source profiles of PM₂.₅ between Yangquan and other cities were compared using the coefficient of divergence method. The result indicated that the main chemical components of PM₂.₅ from the coal dust were SO₄²⁻,Ca, NO₃⁻, OC, EC, Al, Si, Na, Fe, Mg and Cl⁻, accounting for 57.22% of the total mass. The enrichment factor of Pb in PM₂.₅ of coal dust was the largest with a significant enrichment condition, reaching 10.66-15.91. The coefficient of divergence of source profiles of PM₂.₅ between blind coal and fault coal was 0.072, so it was believed that they must be similar. Compared with other cities, the chemical composition of coal dust in Yangquan had specificity, in particular, the content of Ca was obviously higher than those in other domestic cities.

  15. Principal components - Petrology and chemistry of polyphase units in chondritic porous interplanetary dust particles

    NASA Astrophysics Data System (ADS)

    Rietmeijer, Frans J. M.

    1997-03-01

    Chondritic porous (CP) interplanetary dust particles (IDPs) can be described as 'cosmic sediments'. It should be possible to recognize in these IDPs the 4500 Myrs old solar nebula dusts. The studies of unaltered chondritic IDPs show that their matrices are a mixture of three different principal components (PCs) that also describe variable C/Si ratios of chondritic IDPs. Among others, PCs include polyphase units (PUs) that are amorphous to holocrystalline, both ultrafine- and coarse-grained, ferromagnesiosilica(te) materials with minor Al and Ca. The properties of PCs and their alteration products define the physical and chemical processes that produced and altered these components. PCs are also cornerstones of IDP classification. For example, the bulk composition of ultrafine-grained PCs can be reconstructed using the 'butterfly method' and also allows an evaluation of the metamorphic signatures, (e.g., dynamic pyrometamorphism), in chondritic IDPs.

  16. Probing Pre-Supernova Mass Loss With Circumstellar Dust Shells

    NASA Astrophysics Data System (ADS)

    Fox, Ori; Filippenko, Alex; Skrutskie, Mike; van Dyk, Schuyler; Kelly, Pat

    2014-12-01

    Late-time (>100 day) mid-infrared (mid-IR) observations of supernovae (SNe) offer a valuable probe of the progenitor system's mass-loss. Already, this technique has been demonstrated with the Type IIn subclass, which often have large, dusty, pre-existing shells formed in pre-SN eruptions. While other SN subclasses are thought of having relatively low density circumstellar environments, a growing number of objects in other subclasses now show evidence for significant pre-SN mass loss and similar mid-IR characteristics. Long after the SN radioactive tail fades, warm dust can stay bright at mid-IR wavelengths due to alternative heating mechanisms, such as shocks. Here we propose a SNAPSHOT survey of a well-studied and high-profile SN sample, extending over a range of subclasses, including both recent and historical events with evidence of a dense CSM and/or dust. This program will (a) discover new SNe with warm dust and (b) monitor the evolution of warm dust in previously detected SNe. Harnessing the success of our previous Spitzer programs, these observations will expand upon that work by probing the similarities in and differences between the subclasses' circumstellar environments, pre-SN mass-loss, and ultimately, the progenitors themselves.

  17. Enhancement of inorganic Martian dust simulant with carbon component and its effects on key characteristics of glutamatergic neurotransmission

    NASA Astrophysics Data System (ADS)

    Borisova, Tatiana; Krisanova, Natalia; Nazarova, Anastasiya; Borysov, Arseniy; Pastukhov, Artem; Pozdnyakova, Natalia; Dudarenko, Marina

    2016-07-01

    Evidence on the past existence of subsurface organic-bearing fluids on Mars was recently achieved basing on the investigation of organic carbon from the Tissint Martian meteorite (Lin et al., 2014). Tremendous amount of meteorites containing abundant carbon and carbon-enriched dust particles have reached the Earth daily (Pizzarello and Shock 2010). National Institute of Environmental Health Sciences/National Institute of Health panel of research scientists revealed recently that accumulating evidences suggest that nano-sized air pollution may have a significant impact on central nervous system in health and disease (Block et al., Neurotoxicology, 2012). During inhalation, nano-/microsized particles are efficiently deposited in nasal, tracheobronchial, and alveolar regions and can be transported to the central nervous system (Oberdorster et al., 2004). Based on above facts, the aims of this study were: 1) to upgrade inorganic Martian dust stimulant derived from volcanic ash (JSC-1a/JSC, ORBITEC Orbital Technologies Corporation, Madison, Wisconsin) by the addition of carbon components, that is, nanodiamonds; 2) to analyse acute effects of upgraded stimulant on the key characteristic of synaptic neurotransmission and to compare its effects with those of inorganic dust and carbon components per se. Acute administration of carbon-containing Martian dust analogue resulted in a significant decrease in Na+-dependent uptake of L-[14C]glutamate that is the major excitatory neurotransmitter in the central nervous system (CNS). The ambient level of the neurotransmitter in the preparation of isolated rat brain nerve terminals increased in the presence of carbon-contained Martian dust analogue. This fact indicated that carbon component of native Martian dust can have deleterious effects on extracellular glutamate homeostasis in the CNS, and so glutamatergic neurtransmission.

  18. Infrared to millimetre photometry of ultra-luminous IR galaxies: New evidence favouring a 3-stage dust model

    NASA Astrophysics Data System (ADS)

    Klaas, U.; Haas, M.; Müller, S. A. H.; Chini, R.; Schulz, B.; Coulson, I.; Hippelein, H.; Wilke, K.; Albrecht, M.; Lemke, D.

    2001-12-01

    Infrared to millimetre spectral energy distributions (SEDs) have been obtained for 41 bright ultra-luminous infrared galaxies (ULIRGs). The observations were carried out with ISOPHOT between 10 and 200 mu m and supplemented for 16 sources with JCMT/SCUBA at 450 and 850 mu m and with SEST at 1.3 mm. In addition, seven sources were observed at 1.2 and 2.2 mu m with the 2.2 m telescope on Calar Alto. These new SEDs represent the most complete set of infrared photometric templates obtained so far on ULIRGs in the local universe. The SEDs peak at 60-100 mu m and show often a quite shallow Rayleigh-Jeans tail. Fits with one single modified blackbody yield a high FIR opacity and small dust emissivity exponent beta < 2. However, this concept leads to conflicts with several other observational constraints, like the low PAH extinction or the extended filamentary optical morphology. A more consistent picture is obtained using several dust components with beta = 2, low to moderate FIR opacity and cool (50 K > T > 30 K) to cold (30 K > T > 10 K) temperatures. This provides evidence for two dust stages, the cool starburst dominated one and the cold cirrus-like one. The third stage with several hundred Kelvin warm dust is identified in the AGN dominated ULIRGs, showing up as a NIR-MIR power-law flux increase. While AGNs and SBs appear indistinguishable at FIR and submm wavelengths, they differ in the NIR-MIR. This suggests that the cool FIR emitting dust is not related to the AGN, and that the AGN only powers the warm and hot dust. In comparison with optical and MIR spectroscopy, a criterion based on the SED shapes and the NIR colours is established to reveal AGNs among ULIRGs. Also the possibility of recognising evolutionary trends among the ULIRGs via the relative amounts of cold, cool and warm dust components is investigated. Based on observations with the Infrared Space Observatory ISO, the James Clerk Maxwell Telescope JCMT, the Swedish ESO Submillimetre Telescope SEST and

  19. A tunnel and a traffic jam: How transition disks maintain a detectable warm dust component despite the presence of a large planet-carved gap

    NASA Astrophysics Data System (ADS)

    Pinilla, P.; Klarmann, L.; Birnstiel, T.; Benisty, M.; Dominik, C.; Dullemond, C. P.

    2016-01-01

    Context. Transition disks are circumstellar disks that show evidence of a dust cavity, which may be related to dynamical clearing by embedded planet(s). Most of these objects show signs of significant accretion, indicating that the inner disks are not truly empty, but that gas is still streaming through to the star. A subset of transition disks, sometimes called pre-transition disks, also shows a strong near-infrared excess, interpreted as an optically thick dusty belt located close to the dust sublimation radius within the first astronomical unit. Aims: We study the conditions for the survival and maintenance of such an inner disk in the case where a massive planet opens a gap in the disk. In this scenario, the planet filters out large dust grains that are trapped at the outer edge of the gap, while the inner regions of the disk may or may not be replenished with small grains. Methods: We combined hydrodynamical simulations of planet-disk interactions with dust evolution models that include coagulation and fragmentation of dust grains over a large range of radii and derived observational properties using radiative transfer calculations. We studied the role of the snow line in the survival of the inner disk of transition disks. Results: Inside the snow line, the lack of ice mantles in dust particles decreases the sticking efficiency between grains. As a consequence, particles fragment at lower collision velocities than in regions beyond the snow line. This effect allows small particles to be maintained for up to a few Myr within the first astronomical unit. These particles are closely coupled to the gas and do not drift significantly with respect to the gas. For lower mass planets (1 MJup), the pre-transition appearance can be maintained even longer because dust still trickles through the gap created by the planet, moves invisibly and quickly in the form of relatively large grains through the gap, and becomes visible again as it fragments and gets slowed down

  20. Onset of frequent dust storms in northern China at ~AD 1100.

    PubMed

    He, Yuxin; Zhao, Cheng; Song, Mu; Liu, Weiguo; Chen, Fahu; Zhang, Dian; Liu, Zhonghui

    2015-11-26

    Dust storms in northern China strongly affect the living and health of people there and the dusts could travel a full circle of the globe in a short time. Historically, more frequent dust storms occurred during cool periods, particularly the Little Ice Age (LIA), generally attributed to the strengthened Siberian High. However, limited by chronological uncertainties in proxy records, this mechanism may not fully reveal the causes of dust storm frequency changes. Here we present a late Holocene dust record from the Qaidam Basin, where hydrological changes were previously reconstructed, and examine dust records from northern China, including the ones from historical documents. The records, being broadly consistent, indicate the onset of frequent dust storms at ~AD 1100. Further, peaked dust storm events occurred at episodes of high total solar irradiance or warm-dry conditions in source regions, superimposed on the high background of frequent dust storms within the cool LIA period. We thus suggest that besides strong wind activities, the centennial-scale dust storm events over the last 1000 years appear to be linked to the increased availability of dust source. With the anticipated global warming and deteriorating vegetation coverage, frequent occurrence of dust storms in northern China would be expected to persist.

  1. A Spitzer Survey for Dust in Type IIn Supernovae

    NASA Technical Reports Server (NTRS)

    Fox, Ori D.; Chevalier, Roger A.; Skrutskie, Michael F.; Soderberg, Alicia M.; Filippenko, Alexei V.; Ganeshalingam, Mohan; Silverman, Jeffrey M.; Smith, Nathan; Steele, Thea N.

    2011-01-01

    Recent observations suggest that Type IIn supernovae (SNe IIn) may exhibit late-time (greater than 100 days) infrared (IR) emission from warm dust more than other types of core-collapse SNe. Mid-IR observations, which span the peak of the thermal spectral energy distribution, provide useful constraints on the properties of the dust and, ultimately, the circumstellar environment, explosion mechanism, and progenitor system. Due to the low SN IIn rate (less than 10% of all core-collapse SNe), few IR observations exist for this subclass. The handful of isolated studies, however, show late-time IR emission from warm dust that, in some cases, extends for five or six years post-discovery. While previous Spitzer/IRAC surveys have searched for dust in SNe, none have targeted the Type IIn subclass. This article presents results from a warm Spitzer/IRAC survey of the positions of all 68 known SNe IIn within a distance of 250 Mpc between 1999 and 2008 that have remained unobserved by Spitzer more than 100 days postdiscovery. The detection of late-time emission from ten targets (approximately 15%) nearly doubles the database of existing mid-IR observations of SNe IIn. Although optical spectra show evidence for new dust formation in some cases, the data show that in most cases the likely origin of the mid-IR emission is pre-existing dust, which is continuously heated by optical emission generated by ongoing circumstellar interaction between the forward shock and circumstellar medium. Furthermore, an emerging trend suggests that these SNe decline at approximately 1000-2000 days post-discovery once the forward shock overruns the dust shell. The mass-loss rates associated with these dust shells are consistent with luminous blue variable (LBV) progenitors.

  2. A Spitzer Survey for Dust in Type IIn Supernovae

    NASA Technical Reports Server (NTRS)

    Fox, Ori D.; Chevalier, Roger A.; Skrutskie, Michael F.; Soderberg, Alicia M.; Filippenko, Alexei V.; Ganeshalingam, Mohan; Silverman, Jeffrey M.; Smith, Nathan; Steele, Thea N

    2011-01-01

    Recent observations suggest that Type IIn supernovae (SNe IIn) may exhibit late-time (>100 days) infrared (IR) emission from warm dust more than other types of core-collapse SNe. Mid-IR observations, which span the peak of the thermal spectral energy distribution, provide useful constraints on the properties of the dust and, ultimately, the circumstellar environment, explosion mechanism, and progenitor system. Due to the low Type IIn rate (<10% of all core-collapse SNe), few IR observations exist for this subclass. The handful of isolated studies, however, show late-time IR emission from warm dust that, in some cases, extends for five or six years post-discovery. vVhile previous Spitzer/IRAC surveys have searched for dust in SNe, none have targeted the Type IIn subclass. This article presents results from a warm Spitzer/IRAC survey of the positions of all 68 known SNe IIn within a distance of 250 Mpc between 1999 and 2008 that have remained unobserved by Spitzer more than 100 days post-discovery. The detection of late-time emission from ten targets (approx. 15 %) nearly doubles the database of existing mid-IR observations of SNe IIn. Although optical spectra show evidence for new dust formation in some cases, the data show that in most cases the likely origin of the mid-IR emission is pre-existing dust, which is continuously heated by optical emission generated by ongoing circumstellar interaction between the forward shock and circumstellar medium. Furthermore, an emerging trend suggests these SNe "turn off" at " approx. 1000-2000 days post-discovery once the forward shock overruns the dust shell. The mass-loss rates associated with these dust shells are consistent with luminous blue variable (LBV) progenitors having similar mass-loss histories.

  3. Exploring the dust content of galactic winds with Herschel - II. Nearby dwarf galaxies

    NASA Astrophysics Data System (ADS)

    McCormick, Alexander; Veilleux, Sylvain; Meléndez, Marcio; Martin, Crystal L.; Bland-Hawthorn, Joss; Cecil, Gerald; Heitsch, Fabian; Müller, Thomas; Rupke, David S. N.; Engelbracht, Chad

    2018-06-01

    We present the results from an analysis of deep Herschel Space Observatory observations of six nearby dwarf galaxies known to host galactic-scale winds. The superior far-infrared sensitivity and angular resolution of Herschel have allowed detection of cold circumgalactic dust features beyond the stellar components of the host galaxies traced by Spitzer 4.5 μm images. Comparisons of these cold dust features with ancillary data reveal an imperfect spatial correlation with the ionized gas and warm dust wind components. We find that typically ˜10-20 per cent of the total dust mass in these galaxies resides outside of their stellar discs, but this fraction reaches ˜60 per cent in the case of NGC 1569. This galaxy also has the largest metallicity (O/H) deficit in our sample for its stellar mass. Overall, the small number of objects in our sample precludes drawing strong conclusions on the origin of the circumgalactic dust. We detect no statistically significant trends with star formation properties of the host galaxies, as might be expected if the dust were lifted above the disc by energy inputs from ongoing star formation activity. Although a case for dust entrained in a galactic wind is seen in NGC 1569, in all cases, we cannot rule out the possibility that some of the circumgalactic dust might be associated instead with gas accreted or removed from the disc by recent galaxy interaction events, or that it is part of the outer gas-rich portion of the disc that lies below the sensitivity limit of the Spitzer 4.5 μm data.

  4. Respirable dust measured downwind during rock dust application.

    PubMed

    Harris, M L; Organiscak, J; Klima, S; Perera, I E

    2017-05-01

    The Pittsburgh Mining Research Division of the U.S. National Institute for Occupational Safety and Health (NIOSH) conducted underground evaluations in an attempt to quantify respirable rock dust generation when using untreated rock dust and rock dust treated with an anticaking additive. Using personal dust monitors, these evaluations measured respirable rock dust levels arising from a flinger-type application of rock dust on rib and roof surfaces. Rock dust with a majority of the respirable component removed was also applied in NIOSH's Bruceton Experimental Mine using a bantam duster. The respirable dust measurements obtained downwind from both of these tests are presented and discussed. This testing did not measure miners' exposure to respirable coal mine dust under acceptable mining practices, but indicates the need for effective continuous administrative controls to be exercised when rock dusting to minimize the measured amount of rock dust in the sampling device.

  5. Martian Arctic Dust Devil, Phoenix Sol 104

    NASA Technical Reports Server (NTRS)

    2008-01-01

    The Surface Stereo Imager on NASA's Phoenix Mars Lander caught this dust devil in action west-southwest of the lander at 11:16 a.m. local Mars time on Sol 104, or the 104th Martian day of the mission, Sept. 9, 2008.

    Dust devils have not been detected in any Phoenix images from earlier in the mission, but at least six were observed in a dozen images taken on Sol 104.

    Dust devils are whirlwinds that often occur when the Sun heats the surface of Mars, or some areas on Earth. The warmed surface heats the layer of atmosphere closest to it, and the warm air rises in a whirling motion, stirring dust up from the surface like a miniature tornado.

    The dust devil visible in the center of this image just below the horizon is estimated to be about 400 meters (about 1,300 feet) from Phoenix, and 4 meters (13 feet) in diameter. It is much smaller than dust devils that have been observed by NASA's Mars Exploration Rover Spirit much closer to the equator. It is closer in size to dust devils seen from orbit in the Phoenix landing region, though still smaller than those.

    The image has been enhanced to make the dust devil easier to see.

    The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

  6. ALMA Reveals Metals yet No Dust within Multiple Components in CR7

    NASA Astrophysics Data System (ADS)

    Matthee, J.; Sobral, D.; Boone, F.; Röttgering, H.; Schaerer, D.; Girard, M.; Pallottini, A.; Vallini, L.; Ferrara, A.; Darvish, B.; Mobasher, B.

    2017-12-01

    We present spectroscopic follow-up observations of CR7 with ALMA, targeted at constraining the infrared (IR) continuum and [C II]{}158μ {{m}} line-emission at high spatial resolution matched to the HST/WFC3 imaging. CR7 is a luminous Lyα emitting galaxy at z = 6.6 that consists of three separated UV-continuum components. Our observations reveal several well-separated components of [C II] emission. The two most luminous components in [C II] coincide with the brightest UV components (A and B), blueshifted by ≈ 150 km s‑1 with respect to the peak of Lyα emission. Other [C II] components are observed close to UV clumps B and C and are blueshifted by ≈ 300 and ≈80 km s‑1 with respect to the systemic redshift. We do not detect FIR continuum emission due to dust with a 3σ limiting luminosity {L}{IR}({T}d=35 {{K}})< 3.1× {10}10 {L}ȯ . This allows us to mitigate uncertainties in the dust-corrected SFR and derive SFRs for the three UV clumps A, B, and C of 28, 5, and 7 {M}ȯ yr‑1. All clumps have [C II] luminosities consistent within the scatter observed in the local relation between SFR and {L}[{{C}{{II}}]}, implying that strong Lyα emission does not necessarily anti-correlate with [C II] luminosity. Combining our measurements with the literature, we show that galaxies with blue UV slopes have weaker [C II] emission at fixed SFR, potentially due to their lower metallicities and/or higher photoionization. Comparison with hydrodynamical simulations suggests that CR7's clumps have metallicities of 0.1< {{Z}}/{{{Z}}}ȯ < 0.2. The observed ISM structure of CR7 indicates that we are likely witnessing the build up of a central galaxy in the early universe through complex accretion of satellites.

  7. The heating of dust in starburst galaxies: The contribution of the nonionizing radiation

    NASA Technical Reports Server (NTRS)

    Calzetti, D.; Bohlin, R. C.; Kinney, Anne L.; Storchi-Bergmann, T.; Heckman, Timothy M.

    1995-01-01

    The IUE UV and optical spectra and the far-infrared (FIR) IRAS flux densities of a sample of starburst and blue compact galaxies are used to investigate the relationship between dust obscuration and dust emission. The amount of dust obscuration at UV wavelengths correlates with the FIR-to-blue ratio; and an analysis of the correlation indicates that not only the ionizing but also the nonionizing radiation contribute to the FIR emission. The amount of UV and optical energy lost to dust obscuration accounts for most of the cool dust FIUR emission and for about 70% of the warm dust FIR emission. The remaining 30% of the warm dust FIR flux is probably due to dust emission from regions of star formation which are embedded in opaque giant molecular clouds and do not contribute to the integrated UV and optical spectrum. The use of the FIR emission as an indicator of high-mass star formation rate in star-forming galaxies can be problematic, since the contribution to the FIR flux from cool dust emission heated by relatively old stars is nonnegligible.

  8. The Umov effect in application to an optically thin two-component cloud of cosmic dust

    NASA Astrophysics Data System (ADS)

    Zubko, Evgenij; Videen, Gorden; Zubko, Nataliya; Shkuratov, Yuriy

    2018-04-01

    The Umov effect is an inverse correlation between linear polarization of the sunlight scattered by an object and its geometric albedo. The Umov effect has been observed in particulate surfaces, such as planetary regoliths, and recently it also was found in single-scattering small dust particles. Using numerical modeling, we study the Umov effect in a two-component mixture of small irregularly shaped particles. Such a complex chemical composition is suggested in cometary comae and other types of optically thin clouds of cosmic dust. We find that the two-component mixtures of small particles also reveal the Umov effect regardless of the chemical composition of their end-member components. The interrelation between log(Pmax) and log(A) in a two-component mixture of small irregularly shaped particles appears either in a straight linear form or in a slightly curved form. This curvature tends to decrease while the index n in a power-law size distribution r-n grows; at n > 2.5, the log(Pmax)-log(A) diagrams are almost straight linear in appearance. The curvature also noticeably decreases with the packing density of constituent material in irregularly shaped particles forming the mixture. That such a relation exists suggest the Umov effect may also be observed in more complex mixtures.

  9. The Umov effect in application to an optically thin two-component cloud of cosmic dust

    NASA Astrophysics Data System (ADS)

    Zubko, Evgenij; Videen, Gorden; Zubko, Nataliya; Shkuratov, Yuriy

    2018-07-01

    The Umov effect is an inverse correlation between linear polarization of the sunlight scattered by an object and its geometric albedo. The Umov effect has been observed in particulate surfaces, such as planetary regoliths, and recently it also was found in single-scattering small dust particles. Using numerical modelling, we study the Umov effect in a two-component mixture of small irregularly shaped particles. Such a complex chemical composition is suggested in cometary comae and other types of optically thin clouds of cosmic dust. We find that the two-component mixtures of small particles also reveal the Umov effect regardless of the chemical composition of their end-member components. The interrelation between log(Pmax) and log(A) in a two-component mixture of small irregularly shaped particles appears either in a straight linear form or in a slightly curved form. This curvature tends to decrease while the index n in a power-law size distribution r-n grows; at n > 2.5, the log(Pmax)-log(A) diagrams are almost straight linear in appearance. The curvature also noticeably decreases with the packing density of constituent material in irregularly shaped particles forming the mixture. That such a relation exists suggests the Umov effect may also be observed in more complex mixtures.

  10. Near-Infrared Spectroscopic Study of Supernova Ejecta and Supernova Dust in Cassiopeia A

    NASA Astrophysics Data System (ADS)

    Lee, Yong-Hyun; Koo, Bon-Chul; Moon, Dae-Sik; Lee, Jae-Joon; Burton, Michael G.

    2016-06-01

    We have carried out near-infrared (NIR) spectroscopic observations of the Cassiopeia A supernova (SN) remnant. We obtained medium-resolution, JHK (0.95 - 2.46 µm) spectra around the main ejecta shell. Using a clump-finding algorithm, we identified 63 'knots' in the two-dimensional dispersed images, and derived their spectroscopic properties. We first present the result of spectral classification of the knots using Principal Component (PC) Analysis. We found that the NIR spectral characteristics of the knots can be mostly (85%) represented by three PCs composed of different sets of emission lines: (1) recombination lines of H and He together with [N I] lines, (2) forbidden lines of Si, P, and S lines, and (3) forbidden Fe lines. The distribution of the knots in the PC planes matches well with the above spectral groups, and we classified the knots into the three corresponding groups, i.e., He-rich, S-rich, and Fe-rich knots. The kinematic and chemical properties of the former two groups match well with those of Quasi-Stationary Flocculi and Fast-Moving Knots known from optical studies. The Fe-rich knots show intermediate characteristics between the former two groups, and we suggest that they are the SN ejecta material from the innermost layer of the progenitor. We also present the results of extinction measurements using the flux ratios between the two NIR [Fe II] lines at 1.257 and 1.644 µm. We have found a clear correlation between the NIR extinction and the radial velocity of ejecta knots, indicating the presence of a large amount of SN dust inside and around the main ejecta shell. In a southern part of the ejecta shell, by analyzing the NIR extinction together with far-infrared thermal dust emission, we show that there are warm (˜100 K) and cool (˜40 K) SN dust components and that the former needs to be silicate grains while the latter, which is responsible for the observed NIR extinction, could be either small (.0.01 µm) Fe or large (&0.1 µm) Si grains. We

  11. Dust Storms and Mortality in the United States, 1995-2005

    EPA Science Inventory

    Extreme weather events, such as dust storms, are predicted to become more frequent as the global climate warms through the 21st century. The impact of dust storms on human health has been studied extensively in the context of Asian, Saharan, Arabian, and Australian storms, but t...

  12. A Coupled Ice-Atmosphere-Dust Model for a Neoproterozoic "Mudball Earth"

    NASA Astrophysics Data System (ADS)

    Goodman, J. C.; Strom, D.

    2010-12-01

    The Neoproterozoic "Snowball Earth" glaciations remain a subject of intense debate. While many have used field data to argue for either a totally or partially ice-covered Earth, fewer efforts have been made to establish the basic physical climate state and internal dynamics of these alternatives. Description of feedbacks is especially important: how does a globally ice-covered Earth reinforce itself as a stable climate system, and/or sow the seeds for its own destruction? In previous work, we investigated the flow properties of thick floating global ice sheets, and found that flow from pole to equator tends to eliminate regions of thin ice in the tropics. We briefly mentioned that ice flow and sublimation could lead to a "lag deposit" of dust on top of the tropical ice. The consequences of this were explored in detail by Dorian Abbott and others, who found that the accumulation of dust atop tropical ice causes a strong warming effect, which strongly promotes deglaciation of a Snowball climate. However, Abbott et al specified a dust layer ab initio in their GCM simulations, leaving aside the processes which produce it. Here, we present the results of our efforts to add dust processes to an earlier coupled atmosphere/ocean/ice model originally developed by David Pollard and Jim Kasting. Their model includes energy balance equations for the atmosphere and an ice mechanics model for glacial flow. To this we have added variables tracking the fraction of dust incorporated into snow and ice; the transport and accumulation of this dust through ice flow; the effects of dust on albedo and penetration of sunlight into the ice; restriction of evaporation from dust-covered surfaces; and density and buoyancy effects of dusty ice. Dust is added to the surface globally at a fixed rate, and is removed by meltwater runoff. We find that ice in tropical regions of net evaporation quickly develops a surface dust layer which drastically lowers its albedo. This dust layer develops

  13. Combined impacts of current and future dust deposition and regional warming on Colorado River Basin snow dynamics and hydrology

    USGS Publications Warehouse

    Deems, Jeffrey S.; Painter, Thomas H.; Barsugli, Joseph J.; Belnap, Jayne; Udall, Bradley

    2013-01-01

    with increased climate forcing. These results have implications for water management and suggest that dust abatement efforts could be an important component of any climate adaptation strategies in the UCRB.

  14. Super-soliton dust-acoustic waves in four-component dusty plasma using non-extensive electrons and ions distributions

    NASA Astrophysics Data System (ADS)

    El-Wakil, S. A.; Abulwafa, Essam M.; Elhanbaly, Atalla A.

    2017-07-01

    Based on Sagdeev pseudo-potential and phase-portrait, the dynamics of four-component dust plasma with non-extensively distributed electrons and ions are investigated. Three distinct types of nonlinear waves, namely, soliton, double layer, and super-soliton, have been found. The basic features of such waves are high sensitivity to Mach number, non-extensive parameter, and dust temperature ratio. It is found that the multi-component plasma is a necessary condition for super-soliton's existence, having a wider amplitude and a larger width than the regular soliton. Super-solitons may also exist when the Sagdeev pseudo-potential curves admit at least four extrema and two roots. In our multi-component plasma system, the super-solitons can be found by increasing the Mach number and the non-extensive parameter beyond those of double-layers. On the contrary, the super-soliton can be produced by decreasing the dust temperature ratio. The conditions of the onset of such nonlinear waves and its merging to regular solitons have been studied. This work shows that the obtained nonlinear waves are found to exist only in the super-sonic Mach number regime. The obtained results may be of wide relevance in the field of space plasma and may also be helpful to better understand the nonlinear fluctuations in the Auroral-zone of the Earth's magnetosphere.

  15. Infrared and X-Ray Spectroscopy of the Kes 75 Supernova Shell Characterizing the Dust and Gas Properties

    NASA Technical Reports Server (NTRS)

    Temim, Tea; Arendt, Richard G.; Dwek, Eli; Slane, Patrick

    2012-01-01

    We present deep Chandra observations and Spitzer Space Telescope infrared (IR) spectroscopy of the shell in the composite supernova remnant (SNR) Kes 75 (G29.7-0.3). The remnant is composed of a central pulsar wind nebula and a bright partial shell in the south that is visible at radio, IR, and X-ray wavelengths. The X-ray emission can be modeled by either a single thermal component with a temperature of approx 1.5 keV, or with two thermal components with temperatures of 1.5 and 0.2 keY. Previous studies suggest that the hot component may originate from reverse-shocked SN ejecta. However, our new analysis shows no definitive evidence for enhanced abundances of Si, S, Ar, Mg, and Fe, as expected from supernova (SN) ejecta, or for the IR spectral signatures characteristic of confirmed SN condensed dust, thus favoring a circumstellar or interstellar origin for the X-ray and IR emission. The X-ray and IR emission in the shell are spatially correlated, suggesting that the dust particles are collisionally heated by the X-ray emitting gas. The IR spectrum of the shell is dominated by continuum emission from dust with little, or no line emission. Modeling the IR spectrum shows that the dust is heated to a temperature of approx 140 K by a relatively dense, hot plasma, that also gives rise to the hot X-ray emission component. The density inferred from the IR emission is significantly higher than the density inferred from the X-ray models, suggesting a low filling factor for this X-ray emitting gas. The total mass of the warm dust component is at least 1.3 x 10(exp -2) Solar Mass, assuming no significant dust destruction has occurred in the shell. The IR data also reveal the presence of an additional plasma component with a cooler temperature, consistent with the 0.2 keV gas component. Our IR analysis therefore provides an independent verification of the cooler component of the X-ray emission. The complementary analyses of the X-ray and IR emission provide quantitative

  16. Spirit Captures Two Dust Devils On the Move

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site] Figure 1 Annotated

    At the Gusev site recently, skies have been very dusty, and on its 421st sol (March 10, 2005) NASA's Mars Exploration Rover Spirit spied two dust devils in action. This is an image from the rover's navigation camera.

    Views of the Gusev landing region from orbit show many dark streaks across the landscape -- tracks where dust devils have removed surface dust to show relatively darker soil below -- but this is the first time Spirit has photographed an active dust devil.

    Scientists are considering several causes of these small phenomena. Dust devils often occur when the Sun heats the surface of Mars. Warmed soil and rocks heat the layer of atmosphere closest to the surface, and the warm air rises in a whirling motion, stirring dust up from the surface like a miniature tornado. Another possibility is that a flow structure might develop over craters as wind speeds increase. As winds pick up, turbulence eddies and rotating columns of air form. As these columns grow in diameter they become taller and gain rotational speed. Eventually they become self-sustaining and the wind blows them down range.

    One sol before this image was taken, power output from Spirit's solar panels went up by about 50 percent when the amount of dust on the panels decreased. Was this a coincidence, or did a helpful dust devil pass over Spirit and lift off some of the dust?

    By comparing the separate images from the rover's different cameras, team members estimate that the dust devils moved about 500 meters (1,640 feet) in the 155 seconds between the navigation camera and hazard-avoidance camera frames; that equates to about 3 meters per second (7 miles per hour). The dust devils appear to be about 1,100 meters (almost three-quarters of a mile) from the rover.

  17. House-Dust Allergy

    PubMed Central

    Johnson, C. A.

    1982-01-01

    House-dust allergy is a common cause of perennial allergic rhinitis and extrinsic asthma. Symptoms tend to be worse when the patient is in bed. A positive skin test properly performed and interpreted confirms the diagnosis. The house-dust mite is the most important antigenic component of house-dust. Treatment consists of environmental control directed at reducing the mite content of bedroom dust, plus control of symptoms with drugs. Immunotherapy is controversial. ImagesFig. 1 PMID:21286201

  18. Ice nucleation by soil dust compared to desert dust aerosols

    NASA Astrophysics Data System (ADS)

    Moehler, O.; Steinke, I.; Ullrich, R.; Höhler, K.; Schiebel, T.; Hoose, C.; Funk, R.

    2015-12-01

    A minor fraction of atmospheric aerosol particles, so-called ice-nucleating particles (INPs), initiates the formation of the ice phase in tropospheric clouds and thereby markedly influences the Earth's weather and climate systems. Whether an aerosol particle acts as an INP depends on its size, morphology and chemical compositions. The INP fraction of certain aerosol types also strongly depends on the temperature and the relative humidity. Because both desert dust and soil dust aerosols typically comprise a variety of different particles, it is difficult to assess and predict their contribution to the atmospheric INP abundance. This requires both accurate modelling of the sources and atmospheric distribution of atmospheric dust components and detailed investigations of their ice nucleation activities. The latter can be achieved in laboratory experiments and parameterized for use in weather and climate models as a function of temperature and particle surface area, a parameter called ice-nucleation active site (INAS) density. Concerning ice nucleation activity studies, the soil dust is of particular interest because it contains a significant fraction of organics and biological components, both with the potential for contributing to the atmospheric INP abundance at relatively high temperatures compared to mineral components. First laboratory ice nucleation experiments with a few soil dust samples indicated their INP fraction to be comparable or slightly enhanced to that of desert dust. We have used the AIDA (Aerosol Interaction and Dynamics in the Atmosphere) cloud simulation chamber to study the immersion freezing ability of four different arable soil dusts, sampled in Germany, China and Argentina. For temperatures higher than about -20°C, we found the INP fraction of aerosols generated from these samples by a dry dispersion technique to be significantly higher compared to various desert dust aerosols also investigated in AIDA experiments. In this contribution, we

  19. Dust Storms in the United States are Associated with Increased Cardiovascular Mortality

    EPA Science Inventory

    Background: Extreme weather events such as dust storms are predicted to become more frequent as the global climate warms through the 21st century. Studies of Asian, Saharan, Arabian, and Australian dust storms have found associations with cardiovascular and total non-accidental...

  20. Biological consequences of earlier snowmelt from desert dust deposition in alpine landscapes.

    PubMed

    Steltzer, Heidi; Landry, Chris; Painter, Thomas H; Anderson, Justin; Ayres, Edward

    2009-07-14

    Dust deposition to mountain snow cover, which has increased since the late 19(th) century, accelerates the rate of snowmelt by increasing the solar radiation absorbed by the snowpack. Snowmelt occurs earlier, but is decoupled from seasonal warming. Climate warming advances the timing of snowmelt and early season phenological events (e.g., the onset of greening and flowering); however, earlier snowmelt without warmer temperatures may have a different effect on phenology. Here, we report the results of a set of snowmelt manipulations in which radiation-absorbing fabric and the addition and removal of dust from the surface of the snowpack advanced or delayed snowmelt in the alpine tundra. These changes in the timing of snowmelt were superimposed on a system where the timing of snowmelt varies with topography and has been affected by increased dust loading. At the community level, phenology exhibited a threshold response to the timing of snowmelt. Greening and flowering were delayed before seasonal warming, after which there was a linear relationship between the date of snowmelt and the timing of phenological events. Consequently, the effects of earlier snowmelt on phenology differed in relation to topography, which resulted in increasing synchronicity in phenology across the alpine landscape with increasingly earlier snowmelt. The consequences of earlier snowmelt from increased dust deposition differ from climate warming and include delayed phenology, leading to synchronized growth and flowering across the landscape and the opportunity for altered species interactions, landscape-scale gene flow via pollination, and nutrient cycling.

  1. OT2_dardila_2: PACS Photometry of Transiting-Planet Systems with Warm Debris Disks

    NASA Astrophysics Data System (ADS)

    Ardila, D.

    2011-09-01

    Dust in debris disks is produced by colliding or evaporating planetesimals, the remnant of the planet formation process. Warm dust disks, known by their emission at =<24 mic, are rare (4% of FGK main-sequence stars), and specially interesting because they trace material in the region likely to host terrestrial planets, where the dust has very short dynamical lifetimes. Dust in this region comes from very recent asteroidal collisions, migrating Kuiper Belt planetesimals, or migrating dust. NASA's Kepler mission has just released a list of 1235 candidate transiting planets, and in parallel, the Wide-Field Infrared Survey Explorer (WISE) has just completed a sensitive all-sky mapping in the 3.4, 4.6, 12, and 22 micron bands. By cross-identifying the WISE sources with Kepler candidates as well as with other transiting planetary systems we have identified 21 transiting planet hosts with previously unknown warm debris disks. We propose Herschel/PACS 100 and 160 micron photometry of this sample, to determine whether the warm dust in these systems represents stochastic outbursts of local dust production, or simply the Wien side of emission from a cold outer dust belt. These data will allow us to put constraints in the dust temperature and infrared luminosity of these systems, allowing them to be understood in the context of other debris disks and disk evolution theory. This program represents a unique opportunity to exploit the synergy between three great space facilities: Herschel, Kepler, and WISE. The transiting planet sample hosts will remain among the most studied group of stars for the years to come, and our knowledge of their planetary architecture will remain incomplete if we do not understand the characteristics of their debris disks.

  2. Martian Arctic Dust Devil and Phoenix Meteorology Mast

    NASA Technical Reports Server (NTRS)

    2008-01-01

    The Surface Stereo Imager on NASA's Phoenix Mars Lander caught this dust devil in action west-southwest of the lander at 11:16 a.m. local Mars time on Sol 104, or the 104th Martian day of the mission, Sept. 9, 2008.

    Dust devils have not been detected in any Phoenix images from earlier in the mission, but at least six were observed in a dozen images taken on Sol 104.

    Dust devils are whirlwinds that often occur when the Sun heats the surface of Mars, or some areas on Earth. The warmed surface heats the layer of atmosphere closest to it, and the warm air rises in a whirling motion, stirring dust up from the surface like a miniature tornado.

    The vertical post near the left edge of this image is the mast of the Meteorological Station on Phoenix. The dust devil visible at the horizon just to the right of the mast is estimated to be 600 to 700 meters (about 2,000 to 2,300 feet) from Phoenix, and 4 to 5 meters (10 to 13 feet) in diameter. It is much smaller than dust devils that have been observed by NASA's Mars Exploration Rover Spirit much closer to the equator. It is closer in size to dust devils seen from orbit in the Phoenix landing region, though still smaller than those.

    The image has been enhanced to make the dust devil easier to see.

    The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

  3. Infrared and X-Ray Spectroscopy of the KES 75 Supernova Remnant Shell: Characterizing the Dust and Gas Properties

    NASA Technical Reports Server (NTRS)

    Temim, Tea; Dwek, Eli; Slane, Patrick; Arendt, Richard G.

    2009-01-01

    We present deep Chandra observations and Spitzer Space Telescope infrared (IR) spectroscopy of the shell in the composite supernova remnant (SNR) Kes 75 (G29.7-0.3). The remnant is composed of a central pulsar wind nebula and a bright partial shell in the south that is visible at radio, IR, and X-ray wavelengths. The X-ray emission can be modeled by either a single thermal component with a temperature of 1.5 keV, or with two thermal components with temperatures of 1.5 and 0.2 keV. Previous studies suggest that the hot component may originate from reverse-shocked SN ejecta. However, our new analysis shows no definitive evidence for enhanced abundances of Si, S, Ar, Mg, and Fe, as expected from supernova (SN) ejecta, or for the IR spectral signatures characteristic of confirmed SN condensed dust, thus favoring a circumstellar or interstellar origin for the X-ray and IR emission. The X-ray and ill emission in the shell are spatially correlated, suggesting that the dust particles are collisionally heated by the X-ray emitting gas. The IR spectrum of the shell is dominated by continuum emission from dust with little, or no line emission. Modeling the IR spectrum shows that the dust is heated to a temperature of 140 K by a relatively dense, hot plasma, that also gives rise to the hot X-ray emission component. The density inferred from the IR emission is significantly higher than the density inferred from the X-ray models, suggesting a low filling factor for this X-ray emitting gas. The total mass of the warm dust component is at least 1.3 x 10(exp -2) solar mass, assuming no significant dust destruction has occurred in the shell. The IR data also reveal the presence of an additional plasma component with a cooler temperature, consistent with the 0.2 keV gas component. Our IR analysis therefore provides an independent verification of the cooler component of the X-ray emission. The complementary analyses of the X-ray and IR emission provide quantitative estimates of

  4. Infrared and X-Ray Spectroscopy of the Kes 75 Supernova Remnant Shell: Characterizing the Dust and Gas Properties

    NASA Technical Reports Server (NTRS)

    Temim, Tea; Slane, Patrick; Arendt, Richard G.; Dwek, Eli

    2011-01-01

    We present deep Chandra observations and Spitzer Space Telescope infrared (IR) spectroscopy of the shell in the composite supernova remnant (SNR) Kes 75 (G29.7-0.3). The remnant is composed of a central pulsar wind nebula and a bright partial shell in the south that is visible at radio, IR, and X-ray wavelengths. The X-ray emission can be modeled by either a single thermal component with a temperature of approximately 1.5 keY, or with two thermal components with temperatures of 1.5 and 0.2 keY. Previous studies suggest that the hot component may originate from reverse-shocked supernova (SN) ejecta. However, our new analysis shows no definitive evidence for enhanced abundances of Si, S, Ar, Mg, and Fe, as expected from SN ejecta, or for the IR spectral signatures characteristic of confirmed SN condensed dust, thus favoring a circumstellar or interstellar origin for the X-ray and IR emission. The X-ray and IR emission in the shell are spatially correlated, suggesting that the dust particles are collisionally heated by the X-ray emitting gas. The IR spectrum of the shell is dominated by continuum emission from dust with little, or no line emission. Modeling the IR spectrum shows that the dust is heated to a temperature of approximately 140 K by a relatively dense, hot plasma that also gives rise to the hot X-my emission component. The density inferred from the IR emission is significantly higher than the density inferred from the X-ray models, suggesting a low filling factor for this X-my emitting gas. The total mass of the warm dust component is at least 1.3 x 10(exp -2) x solar mass, assuming no significant dust destruction has occurred in the shell. The IR data also reveal the presence of an additional plasma component with a cooler temperature, consistent with the 0.2 keV gas component. Our IR analysis therefore provides an independent verification of the cooler component of the X-ray emission. The complementary analyses of the X-ray and IR emission provide

  5. Infrared and X-Ray Spectroscopy of the Kes 75 Supernova Remnant Shell: Characterizing the Dust and Gas Properties

    NASA Astrophysics Data System (ADS)

    Temim, Tea; Slane, Patrick; Arendt, Richard G.; Dwek, Eli

    2012-01-01

    We present deep Chandra observations and Spitzer Space Telescope infrared (IR) spectroscopy of the shell in the composite supernova remnant (SNR) Kes 75 (G29.7-0.3). The remnant is composed of a central pulsar wind nebula and a bright partial shell in the south that is visible at radio, IR, and X-ray wavelengths. The X-ray emission can be modeled by either a single thermal component with a temperature of ~1.5 keV, or with two thermal components with temperatures of 1.5 and 0.2 keV. Previous studies suggest that the hot component may originate from reverse-shocked supernova (SN) ejecta. However, our new analysis shows no definitive evidence for enhanced abundances of Si, S, Ar, Mg, and Fe, as expected from SN ejecta, or for the IR spectral signatures characteristic of confirmed SN condensed dust, thus favoring a circumstellar or interstellar origin for the X-ray and IR emission. The X-ray and IR emission in the shell are spatially correlated, suggesting that the dust particles are collisionally heated by the X-ray emitting gas. The IR spectrum of the shell is dominated by continuum emission from dust with little, or no line emission. Modeling the IR spectrum shows that the dust is heated to a temperature of ~140 K by a relatively dense, hot plasma that also gives rise to the hot X-ray emission component. The density inferred from the IR emission is significantly higher than the density inferred from the X-ray models, suggesting a low filling factor for this X-ray emitting gas. The total mass of the warm dust component is at least 1.3 × 10-2 M ⊙, assuming no significant dust destruction has occurred in the shell. The IR data also reveal the presence of an additional plasma component with a cooler temperature, consistent with the 0.2 keV gas component. Our IR analysis therefore provides an independent verification of the cooler component of the X-ray emission. The complementary analyses of the X-ray and IR emission provide quantitative estimates of density and

  6. Ecosystem recharge by volcanic dust drives broad-scale variation in bird abundance.

    PubMed

    Gunnarsson, Tómas Grétar; Arnalds, Ólafur; Appleton, Graham; Méndez, Verónica; Gill, Jennifer A

    2015-06-01

    Across the globe, deserts and volcanic eruptions produce large volumes of atmospheric dust, and the amount of dust is predicted to increase with global warming. The effects of long-distance airborne dust inputs on ecosystem productivity are potentially far-reaching but have primarily been measured in soil and plants. Airborne dust could also drive distribution and abundance at higher trophic levels, but opportunities to explore these relationships are rare. Here we use Iceland's steep dust deposition gradients to assess the influence of dust on the distribution and abundance of internationally important ground-nesting bird populations. Surveys of the abundance of breeding birds at 729 locations throughout lowland Iceland were used to explore the influence of dust deposition on bird abundance in agricultural, dry, and wet habitats. Dust deposition had a strong positive effect on bird abundance across Iceland in dry and wet habitats, but not in agricultural land where nutrient levels are managed. The abundance of breeding waders, the dominant group of terrestrial birds in Iceland, tripled on average between the lowest and highest dust deposition classes in both wet and dry habitats. The deposition and redistribution of volcanic materials can have powerful impacts in terrestrial ecosystems and can be a major driver of the abundance of higher trophic-level organisms at broad spatial scales. The impacts of volcanic ash deposition during eruptions and subsequent redistribution of unstable volcanic materials are strong enough to override effects of underlying variation in organic matter and clay content on ecosystem fertility. Global rates of atmospheric dust deposition are likely to increase with increasing desertification and glacier retreat, and this study demonstrates that the effects on ecosystems are likely to be far-reaching, both in terms of spatial scales and ecosystem components.

  7. Dust Modeling with GEOS-Chem: Evidence for Acidic Uptake on Dust Surfaces during INTEX-B

    NASA Technical Reports Server (NTRS)

    Fairlie, T. Duncan

    2007-01-01

    We use measurements of aerosol ion composition and size made from the DC8 aircraft during the 2006 INTEX-B airborne campaign to identify mineral dust signatures, and look for evidence for interaction of dust with acidic components. Coating of dust with sulfate or nitrate favors the role of dust particles as cloud condensation nucleii, can promote further uptake of SO2 and N2O5, can impact NOx/HNO3 partitioning, and can shift sulfate or nitrate towards larger sizes, affecting atmospheric lifetimes for both aerosol and gas components. Mineral dust had a pervasive presence on flights made during the Northern Pacific deployment of the INTEX-B mission. We use scatter plots of ion mixing ratios with Na+ and Ca(2+) to distinguish sea salt and mineral components of the aerosol distribution, respectively. Positive correlations of non-sea-salt sulfate and nitrate with calcium indicate that the dusty air stream is associated with polluted air masses. Sulfate-ammonium scatter plots indicate sulfate to be primarily in the form of (NH4)2SO4. A positive correlation between Ca(2+) and NO-, but little evidence of NH4NO3, suggests that NO3- may be associated with mineral dust surfaces. 3-d model simulations conducted with the GEOS-Chem chemical transport model indicate that transpacific transport from East Asia was principally responsible for the dust observed from the aircraft over the Pacific. We compare the aerosol component relationships in the model with those observed. Uptake of sulfate and nitrate on the dust is not yet represented in the model.

  8. Martian Dust Devil Movie, Phoenix Sol 104

    NASA Technical Reports Server (NTRS)

    2008-01-01

    The Surface Stereo Imager on NASA's Phoenix Mars Lander caught this dust devil in action west of the lander in four frames shot about 50 seconds apart from each other between 11:53 a.m. and 11:56 a.m. local Mars time on Sol 104, or the 104th Martian day of the mission, Sept. 9, 2008.

    Dust devils have not been detected in any Phoenix images from earlier in the mission, but at least six were observed in a dozen images taken on Sol 104.

    Dust devils are whirlwinds that often occur when the Sun heats the surface of Mars, or some areas on Earth. The warmed surface heats the layer of atmosphere closest to it, and the warm air rises in a whirling motion, stirring dust up from the surface like a miniature tornado.

    The dust devil visible in this sequence was about 1,000 meters (about 3,300 feet) from the lander when the first frame was taken, and had moved to about 1,700 meters (about 5,600 feet) away by the time the last frame was taken about two and a half minutes later. The dust devil was moving westward at an estimated speed of 5 meters per second (11 miles per hour), which is similar to typical late-morning wind speed and direction indicated by the telltale wind gauge on Phoenix.

    This dust devil is about 5 meters (16 feet) in diameter. This is much smaller than dust devils that have been observed by NASA's Mars Exploration Rover Spirit much closer to the equator. It is closer in size to dust devils seen from orbit in the Phoenix landing region, though still smaller than those..

    The image has been enhanced to make the dust devil easier to see. Some of the frame-to-frame differences in the appearance of foreground rocks is because each frame was taken through a different color filter.

    The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

  9. Matrix and fine-grained rims in the unequilibrated CO3 chondrite, ALHA77307 - Origins and evidence for diverse, primitive nebular dust components

    NASA Technical Reports Server (NTRS)

    Brearley, Adrian J.

    1993-01-01

    SEM, TEM, and electron microprobe analysis were used to investigate in detail the mineralogical and chemical characteristics of dark matrix and fine-grained rims in the unequilibrated CO3 chondrite ALHA77307. Data obtained revealed that there was a remarkable diversity of distinct mineralogical components, which can be identified using their chemical and textural characteristics. The matrix and rim components in ALHA77307 formed by disequilibrium condensation process as fine-grained amorphous dust that is represented by the abundant amorphous component in the matrix. Subsequent thermal processing of this condensate material, in a variety of environments in the nebula, caused partial or complete recrystallization of the fine-grained dust.

  10. Herschel/PACS photometry of transiting-planet host stars with candidate warm debris disks

    NASA Astrophysics Data System (ADS)

    Ardila, David R.; Merin, Bruno; Ribas, Alvaro; Bouy, Herve; Bryden, Geoffrey; Stapelfeldt, Karl R.; Padgett, Deborah

    2015-01-01

    Dust in debris disks is produced by colliding or evaporating planetesimals, which are remnants of the planet formation process. Warm dust disks, known by their emission at ≤24 μm, are rare (4% of FGK main sequence stars) and especially interesting because they trace material in the region likely to host terrestrial planets, where the dust has a very short dynamical lifetime. Statistical analyses of the source counts of excesses as found with the mid-IR Wide Field Infrared Survey Explorer (WISE) suggest that warm-dust candidates found for the Kepler transiting-planet host-star candidates can be explained by extragalactic or galactic background emission aligned by chance with the target stars. These statistical analyses do not exclude the possibility that a given WISE excess could be due to a transient dust population associated with the target. Here we report Herschel/PACS 100 and 160 micron follow-up observations of a sample of Kepler and non-Kepler transiting-planet candidates' host stars, with candidate WISE warm debris disks, aimed at detecting a possible cold debris disk in any one of them. No clear detections were found in any one of the objects at either wavelength. Our upper limits confirm that most objects in the sample do not have a massive debris disk like that in beta Pic. We also show that the planet-hosting star WASP-33 does not have a debris disk comparable to the one around eta Crv. Although the data cannot be used to rule out rare warm disks around the Kepler planet-hosting candidates, the lack of detections and the characteristics of neighboring emission found at far-IR wavelengths support an earlier result suggesting that most of the WISE-selected IR excesses around Kepler candidate host stars are likely due to either chance alignment with background IR-bright galaxies and/or to interstellar emission.

  11. Cooling of the North Atlantic by Saharan Dust

    NASA Technical Reports Server (NTRS)

    Lau, K. M.; Kim, K. M.

    2007-01-01

    Using aerosol optical depth, sea surface temperature, top-of-the-atmosphere solar radiation flux, and oceanic mixed-layer depth from diverse data sources that include NASA satellites, NCEP reanalysis, in situ observations, as well as long-term dust records from Barbados, we examine the possible relationships between Saharan dust and Atlantic sea surface temperature. Results show that the estimated anomalous cooling pattern of the Atlantic during June 2006 relative to June 2005 due to attenuation of surface solar radiation by Saharan dust remarkably resemble observations, accounting for approximately 30-40% of the observed change in sea surface temperature. Historical data analysis show that there is a robust negative correlation between atmospheric dust loading and Atlantic SST consistent with the notion that increased (decreased) Saharan dust is associated with cooling (warming) of the Atlantic during the early hurricane season (July- August-September).

  12. Diamond, aromatic, aliphatic components of interstellar dust grains: Random covalent networks in carbonaceous grains

    NASA Astrophysics Data System (ADS)

    Duley, W. W.

    1995-05-01

    A formalism based on the theory of random covalent networks (RCNs) in amorphous solids is developed for carbonaceous dust grains. RCN solutions provide optimized structures and relative compositions for amorphous materials. By inclusion of aliphatic, aromatic, and diamond clusters, solutions specific to interstellar materials can be obtained and compared with infrared spectral data. It is found that distinct RCN solutions corresponding to diffuse cloud and molecular cloud materials are possible. Specific solutions are derived for three representative objects: VI Cyg No. 12, NGC 7538 (IRS 9), and GC IRS 7. While diffuse cloud conditions with a preponderance of sp2 and sp3 bonded aliphatic CH species can be reproduced under a variety of RCN conditions, the presence of an abundant tertiary CH or diamond component is highly constrained. These solutions are related quantitatively to carbon depletions and can be used to provide a quantitative estimate of carbon in these various dust components. Despite the abundance of C6 aromatic rings in many RCN solutions, the infrared absorption due to the aromatic stretch at approximately 3.3 micrometers is weak under all conditions. The RCN formalism is shown to provide a useful method for tracing the evolutionary properties of interstellar carbonaceous grains.

  13. Global warming and climate forcing by recent albedo changes on Mars

    USGS Publications Warehouse

    Fenton, L.K.; Geissler, P.E.; Haberle, R.M.

    2007-01-01

    For hundreds of years, scientists have tracked the changing appearance of Mars, first by hand drawings and later by photographs. Because of this historical record, many classical albedo patterns have long been known to shift in appearance over time. Decadal variations of the martian surface albedo are generally attributed to removal and deposition of small amounts of relatively bright dust on the surface. Large swaths of the surface (up to 56 million km2) have been observed to darken or brighten by 10 per cent or more. It is unknown, however, how these albedo changes affect wind circulation, dust transport and the feedback between these processes and the martian climate. Here we present predictions from a Mars general circulation model, indicating that the observed interannual albedo alterations strongly influence the martian environment. Results indicate enhanced wind stress in recently darkened areas and decreased wind stress in brightened areas, producing a positive feedback system in which the albedo changes strengthen the winds that generate the changes. The simulations also predict a net annual global warming of surface air temperatures by ???0.65 K, enhancing dust lifting by increasing the likelihood of dust devil generation. The increase in global dust lifting by both wind stress and dust devils may affect the mechanisms that trigger large dust storm initiation, a poorly understood phenomenon, unique to Mars. In addition, predicted increases in summertime air temperatures at high southern latitudes would contribute to the rapid and steady scarp retreat that has been observed in the south polar residual ice for the past four Mars years. Our results suggest that documented albedo changes affect recent climate change and large-scale weather patterns on Mars, and thus albedo variations are a necessary component of future atmospheric and climate studies. ??2007 Nature Publishing Group.

  14. Global warming and climate forcing by recent albedo changes on Mars.

    PubMed

    Fenton, Lori K; Geissler, Paul E; Haberle, Robert M

    2007-04-05

    For hundreds of years, scientists have tracked the changing appearance of Mars, first by hand drawings and later by photographs. Because of this historical record, many classical albedo patterns have long been known to shift in appearance over time. Decadal variations of the martian surface albedo are generally attributed to removal and deposition of small amounts of relatively bright dust on the surface. Large swaths of the surface (up to 56 million km2) have been observed to darken or brighten by 10 per cent or more. It is unknown, however, how these albedo changes affect wind circulation, dust transport and the feedback between these processes and the martian climate. Here we present predictions from a Mars general circulation model, indicating that the observed interannual albedo alterations strongly influence the martian environment. Results indicate enhanced wind stress in recently darkened areas and decreased wind stress in brightened areas, producing a positive feedback system in which the albedo changes strengthen the winds that generate the changes. The simulations also predict a net annual global warming of surface air temperatures by approximately 0.65 K, enhancing dust lifting by increasing the likelihood of dust devil generation. The increase in global dust lifting by both wind stress and dust devils may affect the mechanisms that trigger large dust storm initiation, a poorly understood phenomenon, unique to Mars. In addition, predicted increases in summertime air temperatures at high southern latitudes would contribute to the rapid and steady scarp retreat that has been observed in the south polar residual ice for the past four Mars years. Our results suggest that documented albedo changes affect recent climate change and large-scale weather patterns on Mars, and thus albedo variations are a necessary component of future atmospheric and climate studies.

  15. Marching Dust Devils

    NASA Image and Video Library

    2015-11-05

    On an early fall afternoon in Ganges Chasma Valles Marineris, NASA Mars Reconnaissance Orbiter spacecraft managed to capture a cluster of eight dust devils, five of them in the enhanced color strip. They're together on a dark sandy surface that tilts slightly to the north, towards the Sun. Both of these factors help warm the surface and generate convection in the air above. The surface is streaked with the faint tracks of earlier dust devils. A pair of dust devils appears together at top right, spaced only 250 meters apart. These two have quite different morphologies. The bigger one (on the right) is about 100 meters in diameter and is shaped like a doughnut with a hole in the middle. Its smaller companion is more compact and plume-like, but it too has a small hole in the center, where the air pressure is lowest. It may be that the smaller dust devil is younger than the larger one. A row of four dust devils are in the middle of the color strip, separated by about 900 meters from one another. This image might answer some interesting questions about the behavior of dust devils. Dust devils are theoretically expected to migrate uphill on a sloping surface, or migrate downwind when there is a breeze. Where they are found close together in pairs, they are expected to rotate in opposite directions. HiRISE color observations can be used to determine the direction of rotation and-for fast moving dust devils-the direction of their travel. This is because the different color observations (infrared, red, and blue) are taken at slightly different times. The differences between the earliest color observation and the last tell us about the changes that took place during that time interval. All this requires careful analysis, but if these dust devils are moving fast enough, and spaced closely enough, these here might display some interesting "social dynamics," possibly marching together and rotating in alternating directions. http://photojournal.jpl.nasa.gov/catalog/PIA20045

  16. Properties of Dust Obscured Galaxies in the Nep-Deep Field

    NASA Astrophysics Data System (ADS)

    Oi, Nagisa; Matsuhara, Hideo; Pearson, Chris; Buat, Veronique; Burgarella, Denis; Malkan, Matt; Miyaji, Takamitsu; AKARI-NEP Team

    2017-03-01

    We selected 47 DOGs at z∼1.5 using optical R (or r^{'}), AKARI 18 μm, and 24 μm color in the AKARI North Ecliptic Pole (NEP) Deep survey field. Using the colors among 3, 4, 7, and 9μm, we classified them into 3 groups; bump DOGs (23 sources), power-law DOGs (16 sources), and unknown DOGs (8 sources). We built spectral energy distributions (SEDs) with optical to far-infrared photometric data and investigated their properties using SED fitting method. We found that AGN activity such as a AGN contribution to the infrared luminosity and a Chandra detection rate for bump and power-law DOGs are significantly different, while stellar component properties like a stellar mass and a star-formation rate are similar to each other. A specific star-formation rate range of power-law DOGs is slightly higher than that of bump DOGs with wide overlap. Herschel/PACS detection rates are almost the same between bump and power-law DOGs. On the other hand SPIRE detection rates show large differences between bump and power-law DOGs. These results might be explained by differences in dust temperatures. Both groups of DOGs host hot and/or warm dust (∼ 50 Kelvin), and many bump DOGs contain cooler dust (≤ 30 Kelvin)

  17. Dust Devils in Gusev Crater, Sol 463

    NASA Technical Reports Server (NTRS)

    2005-01-01

    This movie clip shows a several dust devils -- whirlwinds that loft dust into the air -- moving across a plain below the hillside vantage point of NASA's Mars Exploration Rover Spirit. Several of the dust devils are visible at once in some of the frames in this sequence. The local solar time was about 2 p.m., when the ground temperature was high enough to cause turbulence that kicks up dust devils as the wind blows across the plain. The number of seconds elapsed since the first frame is indicated at lower left of the images, typically 20 seconds between frames. Spirit's navigation camera took these images on the rover's 463rd martian day, or sol (April 22, 2005.) Contrast has been enhanced for anything in the images that changes from frame to frame, that is, for the dust devil.

    Scientists expected dust devils since before Spirit landed. The landing area inside Gusev Crater is filled with dark streaks left behind when dust devils pick dust up from an area. It is also filled with bright 'hollows,' which are dust-filled miniature craters. Dust covers most of the terrain. Winds flow into and out of Gusev crater every day. The Sun heats the surface so that the surface is warm to the touch even though the atmosphere at 2 meters (6 feet) above the surface would be chilly. That temperature contrast causes convection. Mixing the dust, winds, and convection can trigger dust devils.

  18. Heliotropic dust rings for Earth climate engineering

    NASA Astrophysics Data System (ADS)

    Bewick, R.; Lücking, C.; Colombo, C.; Sanchez, J. P.; McInnes, C. R.

    2013-04-01

    This paper examines the concept of a Sun-pointing elliptical Earth ring comprised of dust grains to offset global warming. A new family of non-Keplerian periodic orbits, under the effects of solar radiation pressure and the Earth's J2 oblateness perturbation, is used to increase the lifetime of the passive cloud of particles and, thus, increase the efficiency of this geoengineering strategy. An analytical model is used to predict the orbit evolution of the dust ring due to solar-radiation pressure and the J2 effect. The attenuation of the solar radiation can then be calculated from the ring model. In comparison to circular orbits, eccentric orbits yield a more stable environment for small grain sizes and therefore achieve higher efficiencies when the orbit decay of the material is considered. Moreover, the novel orbital dynamics experienced by high area-to-mass ratio objects, influenced by solar radiation pressure and the J2 effect, ensure the ring will maintain a permanent heliotropic shape, with dust spending the largest portion of time on the Sun facing side of the orbit. It is envisaged that small dust grains can be released from a circular generator orbit with an initial impulse to enter an eccentric orbit with Sun-facing apogee. Finally, a lowest estimate of 1 × 1012 kg of material is computed as the total mass required to offset the effects of global warming.

  19. The Effect of Dust on the Martian Polar Vortices

    NASA Technical Reports Server (NTRS)

    Guzewich, Scott D.; Toigo, A. D.; Waugh, D. W.

    2016-01-01

    The influence of atmospheric dust on the dynamics and stability of the martian polar vortices is examined, through analysis of Mars Climate Sounder observations and MarsWRF general circulation model simulations. We show that regional and global dust storms produce transient vortex warming events that partially or fully disrupt the northern winter polar vortex for brief periods. Increased atmospheric dust heating alters the Hadley circulation and shifts the downwelling branch of the circulation poleward, leading to a disruption of the polar vortex for a period of days to weeks. Through our simulations, we find this effect is dependent on the atmospheric heating rate, which can be changed by increasing the amount of dust in the atmosphere or by altering the dust optical properties (e.g., single scattering albedo). Despite this, our simulations show that some level of atmospheric dust is necessary to produce a distinct northern hemisphere winter polar vortex.

  20. The effect of dust on the martian polar vortices

    NASA Astrophysics Data System (ADS)

    Guzewich, Scott D.; Toigo, A. D.; Waugh, D. W.

    2016-11-01

    The influence of atmospheric dust on the dynamics and stability of the martian polar vortices is examined, through analysis of Mars Climate Sounder observations and MarsWRF general circulation model simulations. We show that regional and global dust storms produce ;transient vortex warming; events that partially or fully disrupt the northern winter polar vortex for brief periods. Increased atmospheric dust heating alters the Hadley circulation and shifts the downwelling branch of the circulation poleward, leading to a disruption of the polar vortex for a period of days to weeks. Through our simulations, we find this effect is dependent on the atmospheric heating rate, which can be changed by increasing the amount of dust in the atmosphere or by altering the dust optical properties (e.g., single scattering albedo). Despite this, our simulations show that some level of atmospheric dust is necessary to produce a distinct northern hemisphere winter polar vortex.

  1. Short-term variability of mineral dust, metals and carbon emission from road dust resuspension

    NASA Astrophysics Data System (ADS)

    Amato, Fulvio; Schaap, Martijn; Denier van der Gon, Hugo A. C.; Pandolfi, Marco; Alastuey, Andrés; Keuken, Menno; Querol, Xavier

    2013-08-01

    Particulate matter (PM) pollution in cities has severe impact on morbidity and mortality of their population. In these cities, road dust resuspension contributes largely to PM and airborne heavy metals concentrations. However, the short-term variation of emission through resuspension is not well described in the air quality models, hampering a reliable description of air pollution and related health effects. In this study we experimentally show that the emission strength of resuspension varies widely among road dust components/sources. Our results offer the first experimental evidence of different emission rates for mineral dust, heavy metals and carbon fractions due to traffic-induced resuspension. Also, the same component (or source) recovers differently in a road in Barcelona (Spain) and a road in Utrecht (The Netherlands). This finding has important implications on atmospheric pollution modelling, mostly for mineral dust, heavy metals and carbon species. After rain events, recoveries were generally faster in Barcelona rather than in Utrecht. The largest difference was found for the mineral dust (Al, Si, Ca). Tyre wear particles (organic carbon and zinc) recovered faster than other road dust particles in both cities. The source apportionment of road dust mass provides useful information for air quality management.

  2. Re-Evaluation of Dust Radiative Forcing Using Remote Measurements of Dust Absorption

    NASA Technical Reports Server (NTRS)

    Kaufman, Yoram J.; Tanre, Didier; Karnieli, Arnon; Remer, Lorraine A.

    1998-01-01

    Spectral remote observations of dust properties from space and from the ground creates a powerful tool for determination of dust absorption of solar radiation with an unprecedented accuracy. Absorption is a key component in understanding dust impact on climate. We use Landsat spaceborne measurements at 0.47 to 2.2 microns over Senegal with ground based sunphotometers to find that Saharan dust absorption of solar radiation is two to four times smaller than in models. Though dust absorbs in the blue, almost no absorption was found for wavelengths greater 0.6 microns. The new finding increases by 50% recent estimated solar radiative forcing by dust and decreases the estimated dust heating of the lower troposphere. Dust transported from Asia shows slightly higher absorption probably due to the presence of black carbon from populated regions. Large scale application of this method to satellite data from the Earth Observing System can reduce significantly the uncertainty in the dust radiative effects.

  3. Langmuir wave phase-mixing in warm electron-positron-dusty plasmas

    NASA Astrophysics Data System (ADS)

    Pramanik, Sourav; Maity, Chandan

    2018-04-01

    An analytical study on nonlinear evolution of Langmuir waves in warm electron-positron-dusty plasmas is presented. The massive dust grains of either positively or negatively charged are assumed to form a fixed charge neutralizing background. A perturbative analysis of the fluid-Maxwell's equations confirms that the excited Langmuir waves phase-mix and eventually break, even at arbitrarily low amplitudes. It is shown that the nature of the dust-charge as well as the amount of dust grains can significantly influence the Langmuir wave phase-mixing process. The phase-mixing time is also found to increase with the temperature.

  4. Response of the Water Cycle of West Africa and Atlantic to Radiative Forcing by Saharan Dust

    NASA Technical Reports Server (NTRS)

    Lau, K. M.; Kim, Kyu-Myong; Sud, Yogesh C.; Walker, Gregory L.

    2010-01-01

    The responses of the atmospheric water cycle and climate of West Africa and the Atlantic to radiative forcing of Saharan dust are studied using the NASA finite volume general circulation model (fvGCM), coupled to a mixed layer ocean. We find evidence in support of the "elevated heat pump" (EHP) mechanism that underlines the responses of the atmospheric water cycle to dust forcing as follow. During the boreal summer, as a result of large-scale atmospheric feed back triggered by absorbing dust aerosols, rainfall and cloudiness are enhanced over the West Africa/Easter Atlantic ITCZ, and suppressed over the West Atlantic and Caribbean. region. Shortwave radiation absorption by dust warms the atmosphere and cools the surface, while long wave has the opposite response. The elevated dust layer warms the air over Nest Africa and the eastern Atlantic. The condensation heating associated with the induced deep convection drives and maintains an anomalous large-scale east-west overturning circulation with rising motion over West Africa/eastern Atlantic, and sinking motion over the Caribbean region. The response also includes a strengthening of the West African monsoon, manifested in northward shift of the West Africa precipitation over land, increased low-level westerlies flow over West Africa at the southern edge of the dust layer, and a near surface energy fluxes, resulting in cooling of the Nest African land and the eastern Atlantic, and a warming in the West Atlantic and Caribbean. The EHP effect is most effective for moderate to highly absorbing dusts, and becomes minimized for reflecting dust with single scattering albedo at 0.95 or higher.

  5. Dust Processing in Supernova Remnants: Spitzer MIPS SED and IRS Observations

    NASA Technical Reports Server (NTRS)

    Hewitt, John W.; Petre, Robert; Katsuda Satoru; Andersen, M.; Rho, J.; Reach, W. T.; Bernard, J. P.

    2011-01-01

    We present Spitzer MIPS SED and IRS observations of 14 Galactic Supernova Remnants previously identified in the GLIMPSE survey. We find evidence for SNR/molecular cloud interaction through detection of [OI] emission, ionic lines, and emission from molecular hydrogen. Through black-body fitting of the MIPS SEDs we find the large grains to be warm, 29-66 K. The dust emission is modeled using the DUSTEM code and a three component dust model composed of populations of big grains, very small grains, and polycyclic aromatic hydrocarbons. We find the dust to be moderately heated, typically by 30-100 times the interstellar radiation field. The source of the radiation is likely hydrogen recombination, where the excitation of hydrogen occurred in the shock front. The ratio of very small grains to big grains is found for most of the molecular interacting SNRs to be higher than that found in the plane of the Milky Way, typically by a factor of 2--3. We suggest that dust shattering is responsible for the relative over-abundance of small grains, in agreement with prediction from dust destruction models. However, two of the SNRs are best fit with a very low abundance of carbon grains to silicate grains and with a very high radiation field. A likely reason for the low abundance of small carbon grains is sputtering. We find evidence for silicate emission at 20 $\\mu$m in their SEDs, indicating that they are young SNRs based on the strong radiation field necessary to reproduce the observed SEDs.

  6. Interannual similarity in the Martian atmosphere during the dust storm season

    NASA Astrophysics Data System (ADS)

    Kass, D. M.; Kleinböhl, A.; McCleese, D. J.; Schofield, J. T.; Smith, M. D.

    2016-06-01

    We find that during the dusty season on Mars (southern spring and summer) of years without a global dust storm there are three large regional-scale dust storms. The storms are labeled A, B, and C in seasonal order. This classification is based on examining the zonal mean 50 Pa (˜25 km) daytime temperature retrievals from TES/MGS and MCS/MRO over 6 Mars Years. Regional-scale storms are defined as events where the temperature exceeds 200 K. Examining the MCS dust field at 50 Pa indicates that warming in the Southern Hemisphere is dominated by direct heating, while northern high latitude warming is a dynamical response. A storms are springtime planet encircling Southern Hemisphere events. B storms are southern polar events that begin near perihelion and last through the solstice. C storms are southern summertime events starting well after the end of the B storm. C storms show the most interannual variability.

  7. Interannual Similarity in the Martian Atmosphere During the Dust Storm Season

    NASA Technical Reports Server (NTRS)

    Kass, D. M.; Kleinboehl, A.; McCleese, D. J.; Schofield, J. T.; Smith, M. D.

    2016-01-01

    We find that during the dusty season on Mars (southern spring and summer) of years without a global dust storm there are three large regional-scale dust storms. The storms are labeled A, B, and C in seasonal order. This classification is based on examining the zonal mean 50 Pa (approximately 25 km) daytime temperature retrievals from TES/MGS and MCS/MRO over 6 Mars Years. Regional-scale storms are defined as events where the temperature exceeds 200 K. Examining the MCS dust field at 50 Pa indicates that warming in the Southern Hemisphere is dominated by direct heating, while northern high latitude warming is a dynamical response. A storms are springtime planet encircling Southern Hemisphere events. B storms are southern polar events that begin near perihelion and last through the solstice. C storms are southern summertime events starting well after the end of the B storm. C storms show the most interannual variability.

  8. Herschel/PACS photometry of transiting-planet host stars with candidate warm debris disks

    NASA Astrophysics Data System (ADS)

    Merín, Bruno; Ardila, David R.; Ribas, Álvaro; Bouy, Hervé; Bryden, Geoffrey; Stapelfeldt, Karl; Padgett, Deborah

    2014-09-01

    Dust in debris disks is produced by colliding or evaporating planetesimals, which are remnants of the planet formation process. Warm dust disks, known by their emission at ≤24 μm, are rare (4% of FGK main sequence stars) and especially interesting because they trace material in the region likely to host terrestrial planets, where the dust has a very short dynamical lifetime. Statistical analyses of the source counts of excesses as found with the mid-IR Wide Field Infrared Survey Explorer (WISE) suggest that warm-dust candidates found for the Kepler transiting-planet host-star candidates can be explained by extragalactic or galactic background emission aligned by chance with the target stars. These statistical analyses do not exclude the possibility that a given WISE excess could be due to a transient dust population associated with the target. Here we report Herschel/PACS 100 and 160 micron follow-up observations of a sample of Kepler and non-Kepler transiting-planet candidates' host stars, with candidate WISE warm debris disks, aimed at detecting a possible cold debris disk in any one of them. No clear detections were found in any one of the objects at either wavelength. Our upper limits confirm that most objects in the sample do not have a massive debris disk like that in β Pic. We also show that the planet-hosting star WASP-33 does not have a debris disk comparable to the one around η Crv. Although the data cannot be used to rule out rare warm disks around the Kepler planet-hosting candidates, the lack of detections and the characteristics of neighboring emission found at far-IR wavelengths support an earlier result suggesting that most of the WISE-selected IR excesses around Kepler candidate host stars are likely due to either chance alignment with background IR-bright galaxies and/or to interstellar emission. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important

  9. Vulnerability Assessment of Dust Storms in the United States under a Changing Climate Scenario

    EPA Science Inventory

    Severe weather events, such as flooding, drought, forest fires, and dust storms can have a serious impact on human health. Dust storm events are not well predicted in the United States, however they are expected to become more frequent as global climate warms through the 21st cen...

  10. THE AKARI 2.5-5.0 μm SPECTRAL ATLAS OF TYPE-1 ACTIVE GALACTIC NUCLEI: BLACK HOLE MASS ESTIMATOR, LINE RATIO, AND HOT DUST TEMPERATURE

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kim, Dohyeong; Im, Myungshin; Kim, Ji Hoon

    2015-01-01

    We present 2.5-5.0 μm spectra of 83 nearby (0.002 < z < 0.48) and bright (K < 14 mag) type-1 active galactic nuclei (AGNs) taken with the Infrared Camera on board AKARI. The 2.5-5.0 μm spectral region contains emission lines such as Brβ (2.63 μm), Brα (4.05 μm), and polycyclic aromatic hydrocarbons (3.3 μm), which can be used for studying the black hole (BH) masses and star formation activity in the host galaxies of AGNs. The spectral region also suffers less dust extinction than in the ultra violet (UV) or optical wavelengths, which may provide an unobscured view of dusty AGNs. Our sample is selectedmore » from bright quasar surveys of Palomar-Green and SNUQSO, and AGNs with reverberation-mapped BH masses from Peterson et al. Using 11 AGNs with reliable detection of Brackett lines, we derive the Brackett-line-based BH mass estimators. We also find that the observed Brackett line ratios can be explained with the commonly adopted physical conditions of the broad line region. Moreover, we fit the hot and warm dust components of the dust torus by adding photometric data of SDSS, 2MASS, WISE, and ISO to the AKARI spectra, finding hot and warm dust temperatures of ∼1100 K and ∼220 K, respectively, rather than the commonly cited hot dust temperature of 1500 K.« less

  11. Increasing aeolian dust deposition to snowpacks in the Rocky Mountains inferred from snowpack, wet deposition, and aerosol chemistry

    USGS Publications Warehouse

    Clow, David W.; Williams, Mark W.; Schuster, Paul F.

    2016-01-01

    Mountain snowpacks are a vital natural resource for ∼1.5 billion people in the northern Hemisphere, helping to meet human and ecological demand for water in excess of that provided by summer rain. Springtime warming and aeolian dust deposition accelerate snowmelt, increasing the risk of water shortages during late summer, when demand is greatest. While climate networks provide data that can be used to evaluate the effect of warming on snowpack resources, there are no established regional networks for monitoring aeolian dust deposition to snow. In this study, we test the hypothesis that chemistry of snow, wet deposition, and aerosols can be used as a surrogate for dust deposition to snow. We then analyze spatial patterns and temporal trends in inferred springtime dust deposition to snow across the Rocky Mountains, USA, for 1993–2014. Geochemical evidence, including strong correlations (r2 ≥ 0.94) between Ca2+, alkalinity, and dust concentrations in snow deposited during dust events, indicate that carbonate minerals in dust impart a strong chemical signature that can be used to track dust deposition to snow. Spatial patterns in chemistry of snow, wet deposition, and aerosols indicate that dust deposition increases from north to south in the Rocky Mountains, and temporal trends indicate that winter/spring dust deposition increased by 81% in the southern Rockies during 1993–2014. Using a multivariate modeling approach, we determined that increases in dust deposition and decreases in springtime snowfall combined to accelerate snowmelt timing in the southern Rockies by approximately 7–18 days between 1993 and 2014. Previous studies have shown that aeolian dust emissions may have doubled globally during the 20th century, possibly due to drought and land-use change. Climate projections for increased aridity in the southwestern U.S., northern Africa, and other mid-latitude regions of the northern Hemisphere suggest that aeolian dust emissions may continue to

  12. Several Dust Devils in Gusev Crater, Sol 461

    NASA Technical Reports Server (NTRS)

    2005-01-01

    This movie clip shows a several dust devils -- whirlwinds that loft dust into the air -- moving across a plain below the hillside vantage point of NASA's Mars Exploration Rover Spirit. Several of the dust devils are visible at once in some of the 21 frames in this sequence. The local solar time was about 2 p.m., when the ground temperature was high enough to cause turbulence that kicks up dust devils as the wind blows across the plain. The number of seconds elapsed since the first frame is indicated at lower left of the images, typically 20 seconds between frames. Spirit's navigation camera took these images on the rover's 461st martian day, or sol (April 20, 2005.) Contrast has been enhanced for anything in the images that changes from frame to frame, that is, for the dust devil.

    Scientists expected dust devils since before Spirit landed. The landing area inside Gusev Crater is filled with dark streaks left behind when dust devils pick dust up from an area. It is also filled with bright 'hollows,' which are dust-filled miniature craters. Dust covers most of the terrain. Winds flow into and out of Gusev crater every day. The Sun heats the surface so that the surface is warm to the touch even though the atmosphere at 2 meters (6 feet) above the surface would be chilly. That temperature contrast causes convection. Mixing the dust, winds, and convection can trigger dust devils.

  13. Weather and Large-Scale Dust Activity during Martian Northern Spring and Summer

    NASA Astrophysics Data System (ADS)

    Kass, David M.; Kleinboehl, Armin; McCleese, Daniel J.; Schofield, John Tim; Smith, Michael D.; Heavens, Nicholas

    2016-10-01

    Observations from MCS, TES and THEMIS now span the northern spring and summer seasons (Ls 0° to 180°) of 10 consecutive Mars Years (MY 24 through MY 33). These observations show very similar behavior each year. However, there are also noticeable differences and clear signs of inter-annual variability. To best study the three datasets, we examine zonal mean observations of the lower atmosphere (50 Pa, or ~25 km). This region was selected to provide the best quality from all three instruments. We separate the daytime (afternoon) and nighttime (early morning) data in the analysis.The climate at these seasons is dominated by the aphelion cloud belt, and 50 Pa is often close to the peak opacities in the clouds. There is also a strong diurnal thermal tide signature throughout the season at this altitude. The overall behavior is a rapid cooling at the start of the year (as the dust from the dusty season sediments out of the atmosphere) over the the first ~30° of Ls. The coldest temperatures then last until about the solstice and are followed by a slow warming trend through most of the rest of the season. The last ~30° prior to the fall equinox show a more rapid warming trend and significant inter-annual variability. In about half of the years, there is a warming event of the 50 Pa temperatures in the second half of northern summer. The warming is the signature of dust being lofted above the boundary layer, into the lower atmosphere. Due to the relatively clear atmosphere overall, even modest amounts of dust will create noticeable temperature changes. The temperature signature of the dust is more pronounced in the northern hemisphere.

  14. Dust-wall and dust-plasma interaction in the MIGRAINe code

    NASA Astrophysics Data System (ADS)

    Vignitchouk, L.; Tolias, P.; Ratynskaia, S.

    2014-09-01

    The physical models implemented in the recently developed dust dynamics code MIGRAINe are described. A major update of the treatment of secondary electron emission, stemming from models adapted to typical scrape-off layer temperatures, is reported. Sputtering and plasma species backscattering are introduced from fits of available experimental data and their relative importance to dust charging and heating is assessed in fusion-relevant scenarios. Moreover, the description of collisions between dust particles and plasma-facing components, based on the approximation of elastic-perfectly plastic adhesive spheres, has been upgraded to take into account the effects of particle size and temperature.

  15. Some Pharmacological Actions of Cotton Dust and Other Vegetable Dusts

    PubMed Central

    Nicholls, P. J.

    1962-01-01

    Aqueous extracts of cotton and other vegetable dusts cause contraction of the isolated ileum and tracheal muscle of the guinea-pig, and of isolated human bronchial muscle. The levels of this contractor activity place the dusts of cotton, flax, and jute in the order of the probable incidence of byssinosis occurring in the mills spinning these fibres. Extracts of cotton dust possess a histamine-liberating activity and contain a permeability-increasing component. These actions are of plant origin and are found in the pericarp and bracts of the cotton boll. Histamine and 5-hydroxytryptamine have also been found in some cotton dust samples. The formation of histamine by bacterial action in cotton dust does not take place under conditions found in cotton mills. The smooth muscle contractor substance is organic in nature, relatively heat-stable, and dialysable. The relevance of these results to the symptoms of byssinosis is discussed. PMID:14479451

  16. The global transport of dust: An intercontinental river of dust, microorganisms and toxic chemicals flows through the Earth's atmosphere

    USGS Publications Warehouse

    Griffin, Dale; Kellogg, Christina; Garrison, Virginia; Shinn, Eugene

    2002-01-01

    The coral reefs in the Caribbean have been deteriorating since the 1970s, and no one is quite sure why. Such environmental devastation is usually blamed on Homo sapiens, but that doesn’t seem to be what’s going on here. Recently, some scientists at the USGS think they’ve solved the puzzle: Bacteria and fungi have been hitching trans-Atlantic rides on dust from the Sahara desert and settling into the warm waters of the Caribbean. Microbiologist Dale Griffin and his colleagues make the case for this hypothesis and explore the dangers of dust and microbe transport across the globe.

  17. A GCM Study of Responses of the Atmospheric Water Cycle of West Africa and the Atlantic to Saharan Dust Radiative Forcing

    NASA Technical Reports Server (NTRS)

    Lau, K. M.; Kim, K. M.; Sud, Y. C.; Walker, G. K.

    2009-01-01

    The responses of the atmospheric water cycle and climate of West Africa and the Atlantic to radiative forcing of Saharan dust are studied using the NASA finite volume general circulation model (fvGCM), coupled to a mixed layer ocean. We find evidence of an "elevated heat pump" (EHP) mechanism that underlines the responses of the atmospheric water cycle to dust forcing as follow. During the boreal summerr, as a result of large-scale atmospheric feedback triggered by absorbing dust aerosols, rainfall and cloudiness are ehanIed over the West Africa/Eastern Atlantic ITCZ, and suppressed over the West Atlantic and Caribbean region. Shortwave radiation absorption by dust warms the atmosphere and cools the surface, while longwave has the opposite response. The elevated dust layer warms the air over West Africa and the eastern Atlantic. As the warm air rises, it spawns a large-scale onshore flow carrying the moist air from the eastern Atlantic and the Gulf of Guinea. The onshore flow in turn enhances the deep convection over West Africa land, and the eastern Atlantic. The condensation heating associated with the ensuing deep convection drives and maintains an anomalous large-scale east-west overturning circulation with rising motion over West Africa/eastern Atlantic, and sinking motion over the Caribbean region. The response also includes a strengthening of the West African monsoon, manifested in a northward shift of the West Africa precipitation over land, increased low-level westerlies flow over West Africa at the southern edge of the dust layer, and a near surface westerly jet underneath the dust layer overr the Sahara. The dust radiative forcing also leads to significant changes in surface energy fluxes, resulting in cooling of the West African land and the eastern Atlantic, and warming in the West Atlantic and Caribbean. The EHP effect is most effective for moderate to highly absorbing dusts, and becomes minimized for reflecting dust with single scattering albedo at0

  18. WISE Detections of Dust in the Habitable Zones of Planet-Bearing Stars

    NASA Technical Reports Server (NTRS)

    Morales, Farisa Y.; Padgett, Deborah L.; Bryden, Geoffrey; Werner, M. W.; Furlan, E.

    2012-01-01

    We use data from the Wide-field Infrared Survey Explorer (WISE) all-sky release to explore the incidence of warm dust in the habitable zones around exoplanet-host stars. Dust emission at 12 and/or 22 microns (T(sub dust) approx.300 and/or approx.150 K) traces events in the terrestrial planet zones; its existence implies replenishment by evaporation of comets or collisions of asteroids, possibly stirred by larger planets. Of the 591 planetary systems (728 extrasolar planets) in the Exoplanet Encyclopedia as of 2012 January 31, 350 are robustly detected by WISE at > or = 5(sigma) level. We perform detailed photosphere subtraction using tools developed for Spitzer data and visually inspect all the WISE images to confirm bona fide point sources. We find nine planet-bearing stars show dust excess emission at 12 and/or 22 microns at > or = 3(sigma) level around young, main-sequence, or evolved giant stars. Overall, our results yield an excess incidence of approx.2.6% for stars of all evolutionary stages, but approx.1% for planetary debris disks around main-sequence stars. Besides recovering previously known warm systems, we identify one new excess candidate around the young star UScoCTIO 108.

  19. Reconstructing transport pathways for late Quaternary dust from eastern Australia using the composition of trace elements of long traveled dusts

    NASA Astrophysics Data System (ADS)

    Petherick, Lynda M.; McGowan, Hamish A.; Kamber, Balz S.

    2009-04-01

    The southeast Australian dust transport corridor is the principal pathway through which continental emissions of dust from central and eastern Australia are carried to the oceans by the prevailing mid-latitude westerly circulation. The analysis of trace elements of aeolian dust, preserved in lake sediment on North Stradbroke Island, southeast Queensland, is used to reconstruct variation in the intensity and position of dust transport to the island over the past 25,000 yrs. Separation of local and long traveled dust content of lake sediments is achieved using a unique, four-element (Ga, Ni, Tl and Sc) separation method. The local and continental chronologies of aeolian deposition developed by this study show markedly different records, and indicate varied responses to climate variability on North Stradbroke Island (local aeolian sediment component) and in eastern and central Australia (long traveled dust component). The provenance of the continental component of the record to sub-geologic catchment scales was accomplished using a ternary mixing model in which the chemical identification of dusts extracted, from the lake sediments, was compared to potential chemical characteristics of surface dust from the source areas using 16 trace elements. The results indicate that the position and intensity of dust transport pathways during the late Quaternary varied considerably in response to changing atmospheric circulation patterns as well as to variations in sediment supply to dust source areas, which include the large anabranching river systems of the Lake Eyre and Murray-Darling Basins.

  20. Environmental Sequencing of Biotic Components of Dust in the Chihuahuan Desert

    NASA Astrophysics Data System (ADS)

    Walsh, E.; Gill, T. E.; Rivas, J. A., Jr.; Leung, M. Y.; Mohl, J.

    2015-12-01

    A growing number of studies mark the role of wind in dispersing biota. Most of these approaches have used traditional methods to assess taxonomic diversity. Here we used next generation sequencing to characterize microbiota in dust collected from the Chihuahuan Desert. Atmospheric dust was collected during events during 2011-2014 using dry deposition collectors placed at two sites in El Paso Co., TX. In parallel experiments, we rehydrated subsamples of dust and conducted PCR amplifications using conserved primers for 16S and 18S ribosomal genes. Sequenced reads were de-multiplexed, quality filtered, and processed using QIIME. Taxonomy was assigned based on pairwise identity using BLAST for microbial eukaryotes. All samples were rarefied to a set number of sequences per sample prior to downstream analyses. Bioinformatic analysis of four of the dust samples yielded a diversity of biota, including zooplankton, bacteria, fungi, algae, and protists, but fungi predominate (>90% of both 10K and 3K reads). In our rehydrations of dust samples from the U.S. southwest nematodes, gastrotrichs, tardigrades, monogonont and bdelloid rotifers, branchiopods and numerous ciliates have been recovered. Variability in genetic diversity among samples is based, in part, on the source and extent of the particular dust event. We anticipate the same patterns will be seen in the complete data set. These preliminary results indicate that wind is a major transporter of not only fungi, bacteria and other unicellular organisms but may also be important in shaping the distribution patterns of multi-cellular organisms such as those that inhabit aquatic environments in the arid southwestern US.

  1. Earlier vegetation green-up has reduced spring dust storms

    PubMed Central

    Fan, Bihang; Guo, Li; Li, Ning; Chen, Jin; Lin, Henry; Zhang, Xiaoyang; Shen, Miaogen; Rao, Yuhan; Wang, Cong; Ma, Lei

    2014-01-01

    The observed decline of spring dust storms in Northeast Asia since the 1950s has been attributed to surface wind stilling. However, spring vegetation growth could also restrain dust storms through accumulating aboveground biomass and increasing surface roughness. To investigate the impacts of vegetation spring growth on dust storms, we examine the relationships between recorded spring dust storm outbreaks and satellite-derived vegetation green-up date in Inner Mongolia, Northern China from 1982 to 2008. We find a significant dampening effect of advanced vegetation growth on spring dust storms (r = 0.49, p = 0.01), with a one-day earlier green-up date corresponding to a decrease in annual spring dust storm outbreaks by 3%. Moreover, the higher correlation (r = 0.55, p < 0.01) between green-up date and dust storm outbreak ratio (the ratio of dust storm outbreaks to times of strong wind events) indicates that such effect is independent of changes in surface wind. Spatially, a negative correlation is detected between areas with advanced green-up dates and regional annual spring dust storms (r = −0.49, p = 0.01). This new insight is valuable for understanding dust storms dynamics under the changing climate. Our findings suggest that dust storms in Inner Mongolia will be further mitigated by the projected earlier vegetation green-up in the warming world. PMID:25343265

  2. Earlier vegetation green-up has reduced spring dust storms.

    PubMed

    Fan, Bihang; Guo, Li; Li, Ning; Chen, Jin; Lin, Henry; Zhang, Xiaoyang; Shen, Miaogen; Rao, Yuhan; Wang, Cong; Ma, Lei

    2014-10-24

    The observed decline of spring dust storms in Northeast Asia since the 1950s has been attributed to surface wind stilling. However, spring vegetation growth could also restrain dust storms through accumulating aboveground biomass and increasing surface roughness. To investigate the impacts of vegetation spring growth on dust storms, we examine the relationships between recorded spring dust storm outbreaks and satellite-derived vegetation green-up date in Inner Mongolia, Northern China from 1982 to 2008. We find a significant dampening effect of advanced vegetation growth on spring dust storms (r = 0.49, p = 0.01), with a one-day earlier green-up date corresponding to a decrease in annual spring dust storm outbreaks by 3%. Moreover, the higher correlation (r = 0.55, p < 0.01) between green-up date and dust storm outbreak ratio (the ratio of dust storm outbreaks to times of strong wind events) indicates that such effect is independent of changes in surface wind. Spatially, a negative correlation is detected between areas with advanced green-up dates and regional annual spring dust storms (r = -0.49, p = 0.01). This new insight is valuable for understanding dust storms dynamics under the changing climate. Our findings suggest that dust storms in Inner Mongolia will be further mitigated by the projected earlier vegetation green-up in the warming world.

  3. Planetesimal Formation in the Warm, Inner Disk: Experiments with Tempered Dust

    NASA Astrophysics Data System (ADS)

    de Beule, Caroline; Landers, Joachim; Salamon, Soma; Wende, Heiko; Wurm, Gerhard

    2017-03-01

    It is an open question how elevated temperatures in the inner parts of protoplanetary disks influence the formation of planetesimals. We approach this problem here by studying the tensile strength of granular beds with dust samples tempered at different temperatures. We find via laboratory experiments that tempering at increasing temperatures is correlated with an increase in cohesive forces. We studied dust samples of palagonite (JSC Mars-1a) which were tempered for up to 200 hr at temperatures between 600 and 1200 K, and measured the relative tensile strengths of highly porous dust layers once the samples cooled to room temperature. Tempering increases the tensile strength from 800 K upwards. This change is accompanied by mineral transformations, the formation of iron oxide crystallites as analyzed by Mössbauer spectroscopy, changes in the number size distribution, and the morphology of the surface visible as cracks in larger grains. These results suggest a difference in the collisional evolution toward larger bodies with increasing temperature as collisional growth is fundamentally based on cohesion. While high temperatures might also increase sticking (not studied here), compositional evolution will already enhance the cohesion and the possibility of growing larger aggregates on the way toward planetesimals. This might lead to a preferred in situ formation of inner planets and explain the observed presence of dense inner planetary systems.

  4. Planetesimal Formation in the Warm, Inner Disk: Experiments with Tempered Dust

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    De Beule, Caroline; Landers, Joachim; Salamon, Soma

    2017-03-01

    It is an open question how elevated temperatures in the inner parts of protoplanetary disks influence the formation of planetesimals. We approach this problem here by studying the tensile strength of granular beds with dust samples tempered at different temperatures. We find via laboratory experiments that tempering at increasing temperatures is correlated with an increase in cohesive forces. We studied dust samples of palagonite (JSC Mars-1a) which were tempered for up to 200 hr at temperatures between 600 and 1200 K, and measured the relative tensile strengths of highly porous dust layers once the samples cooled to room temperature. Temperingmore » increases the tensile strength from 800 K upwards. This change is accompanied by mineral transformations, the formation of iron oxide crystallites as analyzed by Mössbauer spectroscopy, changes in the number size distribution, and the morphology of the surface visible as cracks in larger grains. These results suggest a difference in the collisional evolution toward larger bodies with increasing temperature as collisional growth is fundamentally based on cohesion. While high temperatures might also increase sticking (not studied here), compositional evolution will already enhance the cohesion and the possibility of growing larger aggregates on the way toward planetesimals. This might lead to a preferred in situ formation of inner planets and explain the observed presence of dense inner planetary systems.« less

  5. Climatic controls of the interannual to decadal variability in Saudi Arabian dust activity: Towards the development of a seasonal prediction tool

    NASA Astrophysics Data System (ADS)

    Yu, Y.; Notaro, M.; Liu, Z.; Alkolibi, F.; Fadda, E.; Bakhrjy, F.

    2013-12-01

    Atmospheric dust significantly influences the climate system, as well as human life in Saudi Arabia. Skillful seasonal prediction of dust activity with climatic variables will help prevent some negative social impacts of dust storms. Yet, the climatic regulators on Saudi Arabian dust activity remain largely unaddressed. Remote sensing and station observations show consistent seasonal cycles in Saudi Arabian dust activity, which peaks in spring and summer. The climatic controls on springtime and summertime Saudi Arabian dust activity during 1975-2010 are studied using observational and reanalysis data. Empirical Orthogonal Function (EOF) of the observed Saudi Arabian dust storm frequency shows a dominant homogeneous pattern across the country, which has distinct interannual and decadal variations, as revealed by the power spectrum. Regression and correlation analyses reveal that Saudi Arabian dust activity is largely tied to precipitation on the Arabian Peninsula in spring and northwesterly (Shamal) wind in summer. On the seasonal-interannual time scale, warm El Niño-Southern Oscillation (ENSO) phase (El Niño) in winter-to-spring inhibits spring dust activity by increasing the precipitation over the Rub'al Khali Desert, a major dust source region on the southern Arabian Peninsula; warm ENSO and warm Indian Ocean Basin Mode (IOBM) in winter-to-spring favor less summer dust activity by producing anomalously low sea-level pressure over eastern north Africa and Arabian Peninsula, which leads to the reduced Shamal wind speed. The decadal variation in dust activity is likely associated with the Atlantic Multidecadal Oscillation (AMO), which impacts Sahel rainfall and North African dust, and likely dust transport to Saudi Arabia. The Pacific Decadal Oscillation (PDO) and tropical Indian Ocean SST also have influence on the decadal variation in Saudi Arabian dust activity, by altering precipitation over the Arabian Peninsula and summer Shamal wind speed. Using eastern

  6. Full-sky, High-resolution Maps of Interstellar Dust

    NASA Astrophysics Data System (ADS)

    Meisner, Aaron Michael

    We present full-sky, high-resolution maps of interstellar dust based on data from the Wide-field Infrared Survey Explorer (WISE) and Planck missions. We describe our custom processing of the entire WISE 12 micron All-Sky imaging data set, and present the resulting 15 arcsecond resolution, full-sky map of diffuse Galactic dust emission, free of compact sources and other contaminating artifacts. Our derived 12 micron dust map offers angular resolution far superior to that of all other existing full-sky, infrared dust emission maps, revealing a wealth of small-scale filamentary structure. We also apply the Finkbeiner et al. (1999) two-component thermal dust emission model to the Planck HFI maps. We derive full-sky 6.1 arcminute resolution maps of dust optical depth and temperature by fitting this two-component model to Planck 217-857 GHz along with DIRBE/IRAS 100 micron data. In doing so, we obtain the first ever full-sky 100-3000 GHz Planck-based thermal dust emission model, as well as a dust temperature correction with ~10 times enhanced angular resolution relative to DIRBE-based temperature maps. Analyzing the joint Planck/DIRBE dust spectrum, we show that two-component models provide a better fit to the 100-3000 GHz emission than do single-MBB models, though by a lesser margin than found by Finkbeiner et al. (1999) based on FIRAS and DIRBE. We find that, in diffuse sky regions, our two-component 100-217 GHz predictions are on average accurate to within 2.2%, while extrapolating the Planck Collaboration (2013) single-MBB model systematically underpredicts emission by 18.8% at 100 GHz, 12.6% at 143 GHz and 7.9% at 217 GHz. We calibrate our two-component optical depth to reddening, and compare with reddening estimates based on stellar spectra. We find the dominant systematic problems in our temperature/reddening maps to be zodiacal light on large angular scales and the cosmic infrared background anisotropy on small angular scales. Future work will focus on combining

  7. Constraining the Origin and Heating Mechanism of Dust in Type IIn Supernovae

    NASA Astrophysics Data System (ADS)

    Fox, Ori; Skrutskie, Michael; Chevalier, Roger; Moseley, Samuel Harvey

    2011-05-01

    More than any other supernova subclass, Type IIn supernovae tend to exhibit late-time (>100 days) infrared emission from warm dust. Identifying the origin and heating mechanism of the dust provides an important probe of the supernova explosion, circumstellar environment, and progenitor system. Yet mid-infrared observations, which span the peak of the thermal emission, are rare. Two years ago, we executed a warm Spitzer survey (P60122) of sixty-eight Type IIn events from the past ten years. The survey uncovered nine supernovae with unreported late-time infrared excesses, in some cases more than 5 years post-explosion. From this single epoch of data, and ground-based optical data, we have determined the likely origin of the mid-infrared emission to be pre-existing dust that is continuously heated by optical emission generated by ongoing circumstellar interaction between the forward shock and circumstellar medium. Furthermore, we noticed an emerging trend suggests these supernovae ``turn off'' at ~1000-2000 days post-discovery once the forward shock overruns the dust shell. Now is the ideal time to build upon this work with a second epoch of observations, which will be necessary to constrain our models. If we catch even a single supernova turning off between the first and second epochs of observation, we will be able to both measure the size of the circumstellar dust shell and characterize of the supernova progenitor system. We can obtain all the necessary data in only 9.3 hours of observation. Our team has extensive experience in infrared supernovae observations. We have already published two papers on one Type IIn supernovae (SN 2005ip) and authored two successful proposal for Spitzer observations of this subclass. This is an ideal application for the Spitzer warm mission, as the 3.6 and 4.5 micron bands span the peak of the thermal emission and provide the necessary constraints on the dust temperature, mass, and luminosity.

  8. Dust in a Type Ia Supernova Progenitor: Spitzer Spectroscopy of Kepler's Supernova Remnant

    NASA Technical Reports Server (NTRS)

    Williams, Brian J.; Borkowski, Kazimierz; Reynolds, Stephen P.; Ghavamian, Parviz; Blair, William P.; Long, Knox S.; Sankrit, Ravi

    2012-01-01

    Characterization of the relatively poorly-understood progenitor systems of Type Ia supernovae is of great importance in astrophysics, particularly given the important cosmological role that these supernovae play. Kepler's Supernova Remnant, the result of a Type Ia supernova, shows evidence for an interaction with a dense circumstellar medium (CSM), suggesting a single-degenerate progenitor system. We present 7.5-38 micron IR spectra of the remnant, obtained with the Spitzer Space Telescope, dominated by emission from warm dust. Broad spectral features at 10 and 18 micron, consistent with various silicate particles, are seen throughout. These silicates were likely formed in the stellar outflow from the progenitor system during the AGB stage of evolution, and imply an oxygen-rich chemistry. In addition to silicate dust, a second component, possibly carbonaceous dust, is necessary to account for the short-wavelength IRS and IRAC data. This could imply a mixed chemistry in the atmosphere of the progenitor system. However, non-spherical metallic iron inclusions within silicate grains provide an alternative solution. Models of collisionally-heated dust emission from fast shocks (> 1000 km/s) propagating into the CSM can reproduce the majority of the emission associated with non-radiative filaments, where dust temperatures are approx 80-100 K, but fail to account for the highest temperatures detected, in excess of 150 K. We find that slower shocks (a few hundred km/s) into moderate density material (n(sub o) approx 50-100 / cubic cm) are the only viable source of heating for this hottest dust. We confirm the finding of an overall density gradient, with densities in the north being an order of magnitude greater than those in the south.

  9. House dust mites, our intimate associates.

    PubMed

    Nadchatram, M

    2005-06-01

    House dust mites have lived in human contact from time immemorial. Human dander or dead skin constitutes the major organic component of the house dust ecosystem. Because the mites feed on dander, dust mites and human association will continue to co-exist as part of our environment. Efficient house-keeping practice is the best form of control to reduce infestation. However, special precautions are important when individuals are susceptible or sensitive to dust mites. House dust mites are responsible for causing asthma, rhinitis and contact dermatitis. The respiratory allergies are caused by the inhalation of dead or live mites, their faecal matter or other byproducts. Immune factors are of paramount importance in the development of dust related or mite induced respiratory diseases. House dust mites were found in some 1,000 samples of dust taken from approximately 330 dwellings in Peninsular Malaysia and Singapore. Mattresses, carpets, corners of a bedroom, and floor beneath the bed are favourable dust mite habitats. The incriminating species based on studies here and elsewhere, as well as many other species of dust mites of unknown etiological importance are widely distributed in Malaysian homes. Density of dust mites in Malaysia and Singapore is greater than in temperate countries. Prevention and control measures with reference to subjects sensitive to dust mite allergies, including chemical control described in studies conducted in Europe and America are discussed. However, a cost free and most practical way to remove mites, their faecal matter and other products is to resort to sunning the bedding and carpets to kill the living mites, and then beaten and brushed to remove the dust and other components.

  10. Circumstellar dust in symbiotic novae

    NASA Astrophysics Data System (ADS)

    Jurkic, Tomislav; Kotnik-Karuza, Dubravka

    2015-08-01

    Physical properties of the circumstellar dust and associated physical mechanisms play an important role in understanding evolution of symbiotic binaries. We present a model of inner dust regions around the cool Mira component of the two symbiotic novae, RR Tel and HM Sge, based on the long-term near-IR photometry, infrared ISO spectra and mid-IR interferometry. Pulsation properties and long-term variabilities were found from the near-IR light curves. The dust properties were determined using the DUSTY code which solves the radiative transfer. No changes in pulsational parameters were found, but a long-term variations with periods of 20-25 years have been detected which cannot be attributed to orbital motion.Circumstellar silicate dust shell with inner dust shell temperatures between 900 K and 1300 K and of moderate optical depth can explain all the observations. RR Tel showed the presence of an optically thin CS dust envelope and an optically thick dust region outside the line of sight, which was further supported by the detailed modelling using the 2D LELUYA code. Obscuration events in RR Tel were explained by an increase in optical depth caused by the newly condensed dust leading to the formation of a compact dust shell. HM Sge showed permanent obscuration and a presence of a compact dust shell with a variable optical depth. Scattering of the near-IR colours can be understood by a change in sublimation temperature caused by the Mira variability. Presence of large dust grains (up to 4 µm) suggests an increased grain growth in conditions of increased mass loss. The mass loss rates of up to 17·10-6 MSun/yr were significantly higher than in intermediate-period single Miras and in agreement with longer-period O-rich AGB stars.Despite the nova outburst, HM Sge remained enshrouded in dust with no significant dust destruction. The existence of unperturbed dust shell suggests a small influence of the hot component and strong dust shielding from the UV flux. By the use

  11. Circumstellar Dust in Symbiotic Novae

    NASA Astrophysics Data System (ADS)

    Jurkic, T.; Kotnik-Karuza, D.

    2015-12-01

    We present a model of inner dust regions around the cool Mira component of the two symbiotic novae, RR Tel and HM Sge, based on the near-IR photometry, ISO spectra and mid-IR interferometry. The dust properties were determined using the DUSTY code. A compact circumstellar silicate dust shell with inner dust shell temperatures between 900 K and 1300 K and of moderate optical depth can explain all the observations. RR Tel shows the presence of an equatorially enhanced dust density during minimum obscuration. Obscuration events are explained by an increase in optical depth caused by the newly condensed dust. The mass loss rates are significantly higher than in intermediate-period single Miras but in agreement with longer-period O-rich AGB stars.

  12. Long-term variability of dust events in Iceland (1949-2011)

    NASA Astrophysics Data System (ADS)

    Dagsson-Waldhauserova, P.; Arnalds, O.; Olafsson, H.

    2014-06-01

    Long-term frequency of atmospheric dust observations was investigated for the southern part of Iceland and merged with results obtained from the Northeast Iceland (Dagsson-Waldhauserova et al., 2013). In total, over 34 dust days per year on average occurred in Iceland based on conventionally used synoptic codes for dust. Including codes 04-06 into the criteria for dust observations, the frequency was 135 dust days annually. The Sea Level Pressure (SLP) oscillation controlled whether dust events occurred in NE (16.4 dust days annually) or in southern part of Iceland (about 18 dust days annually). The most dust-frequent decade in S Iceland was the 1960s while the most frequent decade in NE Iceland was the 2000s. A total of 32 severe dust storms (visibility < 500 m) was observed in Iceland with the highest frequency during the 2000s in S Iceland. The Arctic dust events (NE Iceland) were typically warm and during summer/autumn (May-September) while the Sub-Arctic dust events (S Iceland) were mainly cold and during winter/spring (March-May). About half of dust events in S Iceland occurred in winter or at sub-zero temperatures. A good correlation was found between PM10 concentrations and visibility during dust observations at the stations Vik and Storhofdi. This study shows that Iceland is among the dustiest areas of the world and dust is emitted the year-round.

  13. On large-scale transport of dust storms and anthropogenic dust-falls over east Asia observed in central Korea in 2009

    NASA Astrophysics Data System (ADS)

    Chung, Y. S.; Kim, Hak-Sung; Chun, Youngsin

    2014-05-01

    Dust air pollution has been routinely monitored in central Korea for the last two decades. In 2009, there were eight typical episodes of significant dust loadings in the air: four were caused by dust storms from deserts in Mongolia and Northern China, while the remaining were typical cases of anthropogenic air pollution masses arriving from the Yellow Sea and East China. These natural dust loadings occurred with cool northwesterly airflows in the forward side of an intense anticyclone coming from Mongolia and Siberia. The mean concentrations of the four natural dustfall cases for TSP, PM10 and PM2.5 were 632, 480 and 100 μg m-3, respectively. In contrast, the anthropogenic dust-pollution episodes occurred with the warm westerly and southwesterly airflows in the rear side of an anticyclone. This produced a favorable atmospheric and chemical condition for the build-up of anthropogenic dust air pollution in the Yellow Sea. The mean concentrations of the four anthropogenic dust loadings for TSP, PM10 and PM2.5 were 224, 187 and 137 μg m-3, respectively. The contents of fine dust loadings of PM2.5 were comparatively high in the cases of anthropogenic air pollution. High atmospheric concentrations of fine particles in the atmosphere cause poor visibility and constitute a health hazard. Satellite observations clearly showed the movement of dust-pollution masses from Mongolia and Northern China and from the Yellow Sea and East China that caused these dust pollution episodes in Korea.

  14. Particle atlas of World Trade Center dust

    USGS Publications Warehouse

    Lowers, Heather; Meeker, Gregory P.

    2005-01-01

    The United States Environmental Protection Agency (EPA) has begun a reassessment of the presence of World Trade Center (WTC) dust in residences, public buildings, and office spaces in New York City, New York. Background dust samples collected from residences, public buildings, and office spaces will be analyzed by multiple laboratories for the presence of WTC dust. Other laboratories are currently studying WTC dust for other purposes, such as health effects studies. To assist in inter-laboratory consistency for identification of WTC dust components, this particle atlas of phases in WTC dust has been compiled.

  15. Silicate Dust in Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Xie, Yanxia; Li, Aigen; Hao, Lei

    2017-01-01

    The unification theory of active galactic nuclei (AGNs) hypothesizes that all AGNs are surrounded by an anisotropic dust torus and are essentially the same objects but viewed from different angles. However, little is known about the dust that plays a central role in the unification theory. There are suggestions that the AGN dust extinction law appreciably differs from that of the Galaxy. Also, the silicate emission features observed in type 1 AGNs appear anomalous (I.e., their peak wavelengths and widths differ considerably from that of the Galaxy). In this work, we explore the dust properties of 147 AGNs of various types at redshifts z≲ 0.5, with special attention paid to 93 AGNs that exhibit the 9.7 and 18 μm silicate emission features. We model their silicate emission spectra obtained with the Infrared Spectrograph aboard the Spitzer Space Telescope. We find that 60/93 of the observed spectra can be well explained with “astronomical silicate,” while the remaining sources favor amorphous olivine or pyroxene. Most notably, all sources require the dust to be micron-sized (with a typical size of ˜1.5 ± 0.1 μm), much larger than submicron-sized Galactic interstellar grains, implying a flat or “gray” extinction law for AGNs. We also find that, while the 9.7 μm emission feature arises predominantly from warm silicate dust of temperature T ˜ 270 K, the ˜5-8 μm continuum emission is mostly from carbon dust of T ˜ 640 K. Finally, the correlations between the dust properties (e.g., mass, temperature) and the AGN properties (e.g., luminosity, black hole mass) have also been investigated.

  16. Effects of mineral dust on global atmospheric nitrate concentrations

    NASA Astrophysics Data System (ADS)

    Karydis, V. A.; Tsimpidi, A. P.; Pozzer, A.; Astitha, M.; Lelieveld, J.

    2016-02-01

    This study assesses the chemical composition and global aerosol load of the major inorganic aerosol components, focusing on mineral dust and aerosol nitrate. The mineral dust aerosol components (i.e., Ca2+, Mg2+, K+, Na+) and their emissions are included in the ECHAM5/MESSy Atmospheric Chemistry model (EMAC). Gas/aerosol partitioning is simulated using the ISORROPIA-II thermodynamic equilibrium model that considers K+, Ca2+, Mg2+, NH4+, Na+, SO42-, NO3-, Cl-, and H2O aerosol components. Emissions of mineral dust are calculated online by taking into account the soil particle size distribution and chemical composition of different deserts worldwide. Presence of metallic ions can substantially affect the nitrate partitioning into the aerosol phase due to thermodynamic interactions. The model simulates highest fine aerosol nitrate concentration over urban and industrialized areas (1-3 µg m-3), while coarse aerosol nitrate is highest close to deserts (1-4 µg m-3). The influence of mineral dust on nitrate formation extends across southern Europe, western USA, and northeastern China. The tropospheric burden of aerosol nitrate increases by 44 % when considering interactions of nitrate with mineral dust. The calculated global average nitrate aerosol concentration near the surface increases by 36 %, while the coarse- and fine-mode concentrations of nitrate increase by 53 and 21 %, respectively. Other inorganic aerosol components are affected by reactive dust components as well (e.g., the tropospheric burden of chloride increases by 9 %, ammonium decreases by 41 %, and sulfate increases by 7 %). Sensitivity tests show that nitrate aerosol is most sensitive to the chemical composition of the emitted mineral dust, followed by the soil size distribution of dust particles, the magnitude of the mineral dust emissions, and the aerosol state assumption.

  17. Guilt by Association: The 13 Micron Dust Emission Feature and Its Correlation to Other Gas and Dust Features

    NASA Astrophysics Data System (ADS)

    Sloan, G. C.; Kraemer, Kathleen E.; Goebel, J. H.; Price, Stephan D.

    2003-09-01

    A study of all full-scan spectra of optically thin oxygen-rich circumstellar dust shells in the database produced by the Short Wavelength Spectrometer on ISO reveals that the strength of several infrared spectral features correlates with the strength of the 13 μm dust feature. These correlated features include dust features at 19.8 and 28.1 μm and the bands produced by warm carbon dioxide molecules (the strongest of which are at 13.9, 15.0, and 16.2 μm). The database does not provide any evidence for a correlation of the 13 μm feature with a dust feature at 32 μm, and it is more likely that a weak emission feature at 16.8 μm arises from carbon dioxide gas rather than dust. The correlated dust features at 13, 20, and 28 μm tend to be stronger with respect to the total dust emission in semiregular and irregular variables associated with the asymptotic giant branch than in Mira variables or supergiants. This family of dust features also tends to be stronger in systems with lower infrared excesses and thus lower mass-loss rates. We hypothesize that the dust features arise from crystalline forms of alumina (13 μm) and silicates (20 and 28 μm). Based on observations with the ISO, a European Space Agency (ESA) project with instruments funded by ESA member states (especially the Principal Investigator countries: France, Germany, the Netherlands, and the United Kingdom) and with the participation of the Institute of Space and Astronautical Science (ISAS) and the National Aeronautics and Space Administration (NASA).

  18. Inference of dust opacities for the 1977 Martian great dust storms from Viking Lander 1 pressure data

    NASA Technical Reports Server (NTRS)

    Zurek, R. W.

    1981-01-01

    The tidal heating components for the dusty Martian atmosphere are computed based on dust optical parameters estimated from Viking Lander imaging data, and used to compute the variation of the tidal surface pressure components at the Viking Lander sites as a function of season and the total vertical extinction optical depth of the atmosphere. An atmospheric tidal model is used which is based on the inviscid, hydrostatic primitive equations linearized about a motionless basic state the temperature of which varies only with height, and the profiles of the tidal forcing components are computed using a delta-Eddington approximation to the radiative transfer equations. Comparison of the model results with the observed variations of surface pressure and overhead dust opacity at the Viking Lander 1 site reveal that the dust opacities and optical parameters derived from imaging data are roughly representative of the global dust haze necessary to reproduce the observed surface pressure amplitudes, with the exception of the model-inferred asymmetry parameter, which is smaller during the onset of a great storm. The observed preferential enhancement of the semidiurnal tide with respect to the diurnal tide during dust storm onset is shown to be due primarily to the elevation of the tidal heating source in a very dusty atmosphere.

  19. Mars' Annular Polar Vortices and their Response to Atmospheric Dust Opacity

    NASA Astrophysics Data System (ADS)

    Guzewich, S.; Waugh, D.; Toigo, A. D.

    2016-12-01

    The potential vorticity structure of the martian polar vortices is distinct from Earth's stratospheric or tropospheric vortices. Rather than exhibiting monotonically increasing potential vorticity toward the geographic pole, as on Earth, the martian fall and winter polar vortices are annular with the potential vorticity maximum situated off the pole and a local minimum in potential vorticity at the pole. Using the MarsWRF general circulation model (GCM), we perform a series of simulations to examine the source of this annular structure. We find that latent heat exchange from the formation of CO2 ice aerosols within the vortex, in a region very near the geographic pole, destroys potential vorticity and creates the annular structure. Furthermore, we describe Mars Climate Sounder and Thermal Emission Spectrometer observations of "transient vortex warming" events, where the air inside the northern hemisphere winter polar vortex is briefly warmed. During the Mars Year 28 (2007) global dust storm, the temperature inside the vortex increased by 70 K and dust directly entered the vortex. Using additional GCM simulations, we diagnose the dynamical changes associated with these transient vortex warming events and find that poleward expansion of the descending branch of the meridional overturning circulation during periods of increased dust opacity disrupts the northern hemisphere winter polar vortex. These increased temperatures also suppress CO2 condensation at the pole, creating a more Earth-like polar vortex where potential vorticity is maximized near the geographic pole.

  20. Dust evolution from comets

    NASA Technical Reports Server (NTRS)

    Sekanina, Z.

    1977-01-01

    The studies of the evolution of cometary debris are reviewed. The subject is divided into three major sections: (1) the developments in the immediate vicinity of the cometary nucleus, which is the source of the dust; (2) the formation of the dust tail; and (3) the blending of the debris with the dust component of interplanetary matter. The importance of the physical theory of comets is emphasized for the understanding of the early phase of the evolution of cometary dust. A physico-dynamical model designed to analyze the particle-emission mechanism from the distribution of light in the dust tails is described and the results are presented. Increased attention is paid to large particles because of their importance for the evolution of the zodiacal cloud. Finally, implications are discussed for the future in situ investigations of comets.

  1. Inhaled endotoxin and organic dust particulates have synergistic proinflammatory effects in equine heaves (organic dust-induced asthma).

    PubMed

    Pirie, R S; Collie, D D S; Dixon, P M; McGorum, B C

    2003-05-01

    Equine heaves is a naturally occurring organic dust-induced asthma characterized by airway neutrophilia, mucus hypersecretion and obstructive lung dysfunction. However, the relative role of different dust components in disease severity remains unclear. This study investigated the relative contribution of inhaled endotoxin and organic dust particulates (mainly mould spores) in inducing heaves in heaves-susceptible horses. Control and heaves-susceptible horses received inhalation challenges with hay dust suspension (HDS) before and after lipopolysaccharide (LPS) depletion. Heaves-susceptible horses also received inhalation challenge with HDS particulates with and without the addition of LPS and were housed in two separate dusty environments during which mould and endotoxin exposure was measured. The airway inflammatory and functional response to each challenge was measured. Depletion of endotoxin from HDS attenuated the airway neutrophilia and abrogated the airway dysfunction induced in heaves horses by inhaled HDS. The airway response was re-established by adding back LPS to the depleted HDS, confirming that the attenuation in airway response was due specifically to endotoxin depletion. Interestingly, the magnitude of alteration in airway response following endotoxin depletion and add-back was greater than that which could be attributed solely to endotoxin per se, indicating that the LPS activity was enhanced by the other dust components. Consistent with this possibility, washed particulates harvested from HDS enhanced the airway response to inhaled LPS in heaves horses. Heaves horses given two different hay/straw challenges had a significantly different severity of airway inflammation and dysfunction, despite airborne dust and endotoxin concentrations in the horses' breathing zones being similar. Although inhaled endotoxin appears not to be the only determinant of disease severity in heaves, it does contribute significantly to the induction of airway inflammation

  2. Climatic factors contributing to long-term variations in surface fine dust concentration in the United States

    NASA Astrophysics Data System (ADS)

    Pu, Bing; Ginoux, Paul

    2018-03-01

    High concentrations of dust particles can cause respiratory problems and increase non-accidental mortality. Studies found fine dust (with an aerodynamic diameter of less than 2.5 µm) is an important component of the total PM2.5 mass in the western and central US in spring and summer and has positive trends. This work examines climatic factors influencing long-term variations in surface fine dust concentration in the US using station data from the Interagency Monitoring Protected Visual Environments (IMPROVE) network during 1990-2015. The variations in the fine dust concentration can be largely explained by the variations in precipitation, surface bareness, and 10 m wind speed. Moreover, including convective parameters such as convective inhibition (CIN) and convective available potential energy (CAPE) that reveal the stability of the atmosphere better explains the variations and trends over the Great Plains from spring to fall.While the positive trend of fine dust concentration in the southwestern US in spring is associated with precipitation deficit, the increase in fine dust over the central Great Plains in summer is largely associated with enhanced CIN and weakened CAPE, which are caused by increased atmospheric stability due to surface drying and lower-troposphere warming. The strengthening of the Great Plains low-level jet also contributes to the increase in fine dust concentration in the central Great Plains in summer via its positive correlation with surface winds and negative correlation with CIN.Summer dusty days in the central Great Plains are usually associated with a westward extension of the North Atlantic subtropical high that intensifies the Great Plains low-level jet and also results in a stable atmosphere with subsidence and reduced precipitation.

  3. Particle Lifting Processes in Dust Devils

    NASA Astrophysics Data System (ADS)

    Neakrase, L. D. V.; Balme, M. R.; Esposito, F.; Kelling, T.; Klose, M.; Kok, J. F.; Marticorena, B.; Merrison, J.; Patel, M.; Wurm, G.

    2016-11-01

    Particle lifting in dust devils on both Earth and Mars has been studied from many different perspectives, including how dust devils could influence the dust cycles of both planets. Here we review our current understanding of particle entrainment by dust devils by examining results from field observations on Earth and Mars, laboratory experiments (at terrestrial ambient and Mars-analog conditions), and analytical modeling. By combining insights obtained from these three methodologies, we provide a detailed overview on interactions between particle lifting processes due to mechanical, thermal, electrodynamical and pressure effects, and how these processes apply to dust devils on Earth and Mars. Experiments and observations have shown dust devils to be effective lifters of dust given the proper conditions on Earth and Mars. However, dust devil studies have yet to determine the individual roles of each of the component processes acting at any given time in dust devils.

  4. Herschel Observations of Gas and Dust in the Unusual 49 Ceti Debris Disk

    NASA Technical Reports Server (NTRS)

    Roberge, A.; Kamp, I.; Montesinos, B.; Dent, W. R. F.; Meeus, G.; Donaldson, J. K.; Olofsson, J.; Moor, A.; Augereau, J.-C.; Howard, C.; hide

    2013-01-01

    We present far-IR/sub-mm imaging and spectroscopy of 49 Ceti, an unusual circumstellar disk around a nearby young A1V star. The system is famous for showing the dust properties of a debris disk, but the gas properties of a low-mass protoplanetary disk. The data were acquired with the Herschel Space Observatory PACS and SPIRE instruments, largely as part of the “Gas in Protoplanetary Systems” (GASPS) Open Time Key Programme. Disk dust emission is detected in images at 70, 160, 250, 350, and 500 micron; 49 Cet is significantly extended in the 70 micron image, spatially resolving the outer dust disk for the first time. Spectra covering small wavelength ranges centered on eight atomic and molecular emission lines were obtained, including [O i] 63 micron and [C ii] 158 micron. The C ii line was detected at the 5 sigma level—the first detection of atomic emission from the disk. No other emission lines were seen, despite the fact that the Oi line is the brightest one observed in Herschel protoplanetary disk spectra. We present an estimate of the amount of circumstellar atomic gas implied by the C ii emission. The new far-IR/sub-mm data fills in a large gap in the previous spectral energy distribution (SED) of 49 Cet. A simple model of the new SED confirms the two-component structure of the disk: warm inner dust and cold outer dust that produces most of the observed excess. Finally, we discuss preliminary thermochemical modeling of the 49 Cet gas/dust disk and our attempts to match several observational results simultaneously. Although we are not yet successful in doing so, our investigations shed light on the evolutionary status of the 49 Cet gas, which might not be primordial gas but rather secondary gas coming from comets.

  5. Herschel Observations of Gas and Dust in the Unusual 49 Ceti Debris Disk

    NASA Astrophysics Data System (ADS)

    Roberge, A.; Kamp, I.; Montesinos, B.; Dent, W. R. F.; Meeus, G.; Donaldson, J. K.; Olofsson, J.; Moór, A.; Augereau, J.-C.; Howard, C.; Eiroa, C.; Thi, W.-F.; Ardila, D. R.; Sandell, G.; Woitke, P.

    2013-07-01

    We present far-IR/sub-mm imaging and spectroscopy of 49 Ceti, an unusual circumstellar disk around a nearby young A1V star. The system is famous for showing the dust properties of a debris disk, but the gas properties of a low-mass protoplanetary disk. The data were acquired with the Herschel Space Observatory PACS and SPIRE instruments, largely as part of the "Gas in Protoplanetary Systems" (GASPS) Open Time Key Programme. Disk dust emission is detected in images at 70, 160, 250, 350, and 500 μm 49 Cet is significantly extended in the 70 μm image, spatially resolving the outer dust disk for the first time. Spectra covering small wavelength ranges centered on eight atomic and molecular emission lines were obtained, including [O I] 63 μm and [C II] 158 μm. The C II line was detected at the 5σ level—the first detection of atomic emission from the disk. No other emission lines were seen, despite the fact that the O I line is the brightest one observed in Herschel protoplanetary disk spectra. We present an estimate of the amount of circumstellar atomic gas implied by the C II emission. The new far-IR/sub-mm data fills in a large gap in the previous spectral energy distribution (SED) of 49 Cet. A simple model of the new SED confirms the two-component structure of the disk: warm inner dust and cold outer dust that produces most of the observed excess. Finally, we discuss preliminary thermochemical modeling of the 49 Cet gas/dust disk and our attempts to match several observational results simultaneously. Although we are not yet successful in doing so, our investigations shed light on the evolutionary status of the 49 Cet gas, which might not be primordial gas but rather secondary gas coming from comets.

  6. Bacterial and fungal components in house dust of farm children, Rudolf Steiner school children and reference children--the PARSIFAL Study.

    PubMed

    Schram, D; Doekes, G; Boeve, M; Douwes, J; Riedler, J; Ublagger, E; von Mutius, E; Budde, J; Pershagen, G; Nyberg, F; Alm, J; Braun-Fahrländer, C; Waser, M; Brunekreef, B

    2005-05-01

    Growing up on a farm and an anthroposophic lifestyle are associated with a lower prevalence of allergic diseases in childhood. It has been suggested that the enhanced exposure to endotoxin is an important protective factor of farm environments. Little is known about exposure to other microbial components on farms and exposure in anthroposophic families. To assess the levels and determinants of bacterial endotoxin, mould beta(1,3)-glucans and fungal extracellular polysaccharides (EPS) in house dust of farm children, Steiner school children and reference children. Mattress and living room dust was collected in the homes of 229 farm children, 122 Steiner children and 60 and 67 of their respective reference children in five European countries. Stable dust was collected as well. All samples were analysed in one central laboratory. Determinants were assessed by questionnaire. Levels of endotoxin, EPS and glucans per gram of house dust in farm homes were 1.2- to 3.2-fold higher than levels in reference homes. For Steiner children, 1.1- to 1.6-fold higher levels were observed compared with their reference children. These differences were consistently found across countries, although mean levels varied considerably. Differences between groups and between countries were also significant after adjustment for home and family characteristics. Farm children are not only consistently exposed to higher levels of endotoxin, but also to higher levels of mould components. Steiner school children may also be exposed to higher levels of microbial agents, but differences with reference children are much less pronounced than for farm children. Further analyses are, however, required to assess the association between exposure to these various microbial agents and allergic and airway diseases in the PARSIFAL population.

  7. Climate Effects and Efficacy of Dust and Soot in Snow

    NASA Astrophysics Data System (ADS)

    Zender, C. S.; Flanner, M. G.; Randerson, J. T.; Mahowald, N. M.; Rasch, P. J.; Yoshioka, M.; Painter, T.

    2006-12-01

    Dust and industrial and biomass burning emissions from low and mid-latitudes dominate the absorbing impurities trapped in snow at mid- and high-latitudes. We study the effects of dust and smoke on global and regional climate using a general circulation model driven by observed and predicted aerosol emissions determined from satellite and in situ observations. The model has sophisticated treatments of aerosol and snowpack radiative and thermodynamic processes that compare well with observations of snow albedo evolution and impurity concentration. This presentation focuses on the individual and combined contributions of present day dust and soot to snow-albedo forcing and on the global temperature and snowpack responses. Results are emphasized near India and East Asia, where the anthropogenic aerosol forcing of surface albedo and hydrology is greatest. We find that dust and black carbon (BC) aerosols have climate change efficacies (surface temperature change per unit forcing) about 3--4 times greater than CO2, making them the most efficacious forcing agents known. We estimate present day dust and soot snowpack-forcing of ~ 0.050 W m-2 warms global climate by ~ 0.16 °K. Anthropogenic soot from fossil fuel sources causes more than 50% of this warming, and biomass burning can account for up to 30% in strong tropical or boreal burn years. The greatest forcings occur in the Tarim/Mongol region (due to dust), northeastern China (due to soot), and the Tibetan Plateau (both). Dirty springtime snow in these regions can darken albedo by more than 0.1 and increase surface absorption by more than 20 W m-2. These results have implications for the strength of the Asian Monsoon, which is negatively correlated with antecedent snow cover in non-ENSO years. Dust and soot have such strong efficacies because they increase spring melt rates thus reduce summer snow cover. In some regions and seasons, dirty snow reduces snowpack depth and cover by 50%, triggering strong snow and sea

  8. Interstellar and Cometary Dust

    NASA Technical Reports Server (NTRS)

    Mathis, John S.

    1997-01-01

    /carbonaceous matrix, without organic refractory mantles, in between the ices. Unfortunately, they may be significantly processed by chemical processes accompanying the warming (over the 10 K of the dark cloud cores) which occurs in the outer solar system. Evidence of this processing is the chemical anomalies present in interplanetary dust particles collected in the stratosphere, which may be the most primitive materials we have obtained to date. The comet return mission would greatly clarify the situation, and probably provide samples of genuine interstellar grains.

  9. Development of a high resolution interstellar dust engineering model - overview of the project

    NASA Astrophysics Data System (ADS)

    Sterken, V. J.; Strub, P.; Soja, R. H.; Srama, R.; Krüger, H.; Grün, E.

    2013-09-01

    Beyond 3 AU heliocentric distance, the flow of interstellar dust through the solar system is a dominant component of the total dust population. The modulation of this flux with the solar cycle and the position in the solar system has been predicted by theoretical studies since the seventies. The modulation was proven to exist by matching dust trajectory simulations with real spacecraft data from Ulysses in 1998. The modulations were further analyzed and studies in detail in 2012. The current ESA interplanetary meteoroid model IMEM includes an interstellar dust component, but this component was modelled only with straight line trajectories through the solar system. For the new ESA IMEX model, a high-resolution interstellar dust component is implemented separately from a dust streams module. The dust streams module focuses on dust in streams that was released from comets (cf. Abstract R. Soja). Parallel processing techniques are used to improve computation time (cf. Abstract P. Strub). The goal is to make predictions for the interstellar dust flux as close to the Sun as 1 AU or closer, for future space mission design.

  10. Investigating the size, shape and surface roughness dependence of polarization lidars with light-scattering computations on real mineral dust particles: Application to dust particles' external mixtures and dust mass concentration retrievals

    NASA Astrophysics Data System (ADS)

    Mehri, Tahar; Kemppinen, Osku; David, Grégory; Lindqvist, Hannakaisa; Tyynelä, Jani; Nousiainen, Timo; Rairoux, Patrick; Miffre, Alain

    2018-05-01

    Our understanding of the contribution of mineral dust to the Earth's radiative budget is limited by the complexity of these particles, which present a wide range of sizes, are highly-irregularly shaped, and are present in the atmosphere in the form of particle mixtures. To address the spatial distribution of mineral dust and atmospheric dust mass concentrations, polarization lidars are nowadays frequently used, with partitioning algorithms allowing to discern the contribution of mineral dust in two or three-component particle external mixtures. In this paper, we investigate the dependence of the retrieved dust backscattering (βd) vertical profiles with the dust particle size and shape. For that, new light-scattering numerical simulations are performed on real atmospheric mineral dust particles, having determined mineralogy (CAL, DOL, AGG, SIL), derived from stereogrammetry (stereo-particles), with potential surface roughness, which are compared to the widely-used spheroidal mathematical shape model. For each dust shape model (smooth stereo-particles, rough stereo-particles, spheroids), the dust depolarization, backscattering Ångström exponent, lidar ratio are computed for two size distributions representative of mineral dust after long-range transport. As an output, two Saharan dust outbreaks involving mineral dust in two, then three-component particle mixtures are studied with Lyon (France) UV-VIS polarization lidar. If the dust size matters most, under certain circumstances, βd can vary by approximately 67% when real dust stereo-particles are used instead of spheroids, corresponding to variations in the dust backscattering coefficient as large as 2 Mm- 1·sr- 1. Moreover, the influence of surface roughness in polarization lidar retrievals is for the first time discussed. Finally, dust mass-extinction conversion factors (ηd) are evaluated for each assigned shape model and dust mass concentrations are retrieved from polarization lidar measurements. From

  11. The implementation of NEMS GFS Aerosol Component (NGAC) Version 1.0 for global dust forecasting at NOAA/NCEP

    PubMed Central

    Lu, Cheng-Hsuan; da Silva, Arlindo; Wang, Jun; Moorthi, Shrinivas; Chin, Mian; Colarco, Peter; Tang, Youhua; Bhattacharjee, Partha S.; Chen, Shen-Po; Chuang, Hui-Ya; Juang, Hann-Ming Henry; McQueen, Jeffery; Iredell, Mark

    2018-01-01

    The NOAA National Centers for Environmental Prediction (NCEP) implemented NEMS GFS Aerosol Component (NGAC) for global dust forecasting in collaboration with NASA Goddard Space Flight Center (GSFC). NGAC Version 1.0 has been providing 5 day dust forecasts at 1°×1° resolution on a global scale, once per day at 00:00 Coordinated Universal Time (UTC), since September 2012. This is the first global system capable of interactive atmosphere aerosol forecasting at NCEP. The implementation of NGAC V1.0 reflects an effective and efficient transitioning of NASA research advances to NCEP operations, paving the way for NCEP to provide global aerosol products serving a wide range of stakeholders as well as to allow the effects of aerosols on weather forecasts and climate prediction to be considered. PMID:29652411

  12. The implementation of NEMS GFS Aerosol Component (NGAC) Version 1.0 for global dust forecasting at NOAA/NCEP.

    PubMed

    Lu, Cheng-Hsuan; da Silva, Arlindo; Wang, Jun; Moorthi, Shrinivas; Chin, Mian; Colarco, Peter; Tang, Youhua; Bhattacharjee, Partha S; Chen, Shen-Po; Chuang, Hui-Ya; Juang, Hann-Ming Henry; McQueen, Jeffery; Iredell, Mark

    2016-01-01

    The NOAA National Centers for Environmental Prediction (NCEP) implemented NEMS GFS Aerosol Component (NGAC) for global dust forecasting in collaboration with NASA Goddard Space Flight Center (GSFC). NGAC Version 1.0 has been providing 5 day dust forecasts at 1°×1° resolution on a global scale, once per day at 00:00 Coordinated Universal Time (UTC), since September 2012. This is the first global system capable of interactive atmosphere aerosol forecasting at NCEP. The implementation of NGAC V1.0 reflects an effective and efficient transitioning of NASA research advances to NCEP operations, paving the way for NCEP to provide global aerosol products serving a wide range of stakeholders as well as to allow the effects of aerosols on weather forecasts and climate prediction to be considered.

  13. Dust-deficient Palomar-Green Quasars and the Diversity of AGN Intrinsic IR Emission

    NASA Astrophysics Data System (ADS)

    Lyu, Jianwei; Rieke, G. H.; Shi, Yong

    2017-02-01

    To elucidate the intrinsic broadband infrared (IR) emission properties of active galactic nuclei (AGNs), we analyze the spectral energy distributions (SEDs) of 87 z ≲ 0.5 Palomar-Green (PG) quasars. While the Elvis AGN template with a moderate far-IR correction can reasonably match the SEDs of the AGN components in ˜60% of the sample (and is superior to alternatives such as that by Assef), it fails on two quasar populations: (1) hot-dust-deficient (HDD) quasars that show very weak emission thoroughly from the near-IR to the far-IR, and (2) warm-dust-deficient (WDD) quasars that have similar hot dust emission as normal quasars but are relatively faint in the mid- and far-IR. After building composite AGN templates for these dust-deficient quasars, we successfully fit the 0.3-500 μm SEDs of the PG sample with the appropriate AGN template, an infrared template of a star-forming galaxy, and a host galaxy stellar template. 20 HDD and 12 WDD quasars are identified from the SED decomposition, including seven ambiguous cases. Compared with normal quasars, the HDD quasars have AGNs with relatively low Eddington ratios and the fraction of WDD quasars increases with AGN luminosity. Moreover, both the HDD and WDD quasar populations show relatively stronger mid-IR silicate emission. Virtually identical SED properties are also found in some quasars from z = 0.5 to 6. We propose a conceptual model to demonstrate that the observed dust deficiency of quasars can result from a change of structures of the circumnuclear tori that can occur at any cosmic epoch.

  14. 20th-Century doubling in dust archived in an Antarctic Peninsula ice core parallels climate change and desertification in South America

    PubMed Central

    McConnell, Joseph R.; Aristarain, Alberto J.; Banta, J. Ryan; Edwards, P. Ross; Simões, Jefferson C.

    2007-01-01

    Crustal dust in the atmosphere impacts Earth's radiative forcing directly by modifying the radiation budget and affecting cloud nucleation and optical properties, and indirectly through ocean fertilization, which alters carbon sequestration. Increased dust in the atmosphere has been linked to decreased global air temperature in past ice core studies of glacial to interglacial transitions. We present a continuous ice core record of aluminum deposition during recent centuries in the northern Antarctic Peninsula, the most rapidly warming region of the Southern Hemisphere; such a record has not been reported previously. This record shows that aluminosilicate dust deposition more than doubled during the 20th century, coincident with the ≈1°C Southern Hemisphere warming: a pattern in parallel with increasing air temperatures, decreasing relative humidity, and widespread desertification in Patagonia and northern Argentina. These results have far-reaching implications for understanding the forces driving dust generation and impacts of changing dust levels on climate both in the recent past and future. PMID:17389397

  15. Long-term variability of dust events in Iceland (1949-2011)

    NASA Astrophysics Data System (ADS)

    Dagsson-Waldhauserova, P.; Arnalds, O.; Olafsson, H.

    2014-12-01

    The long-term frequency of atmospheric dust observations was investigated for the southern part of Iceland and interpreted together with earlier results obtained from northeastern (NE) Iceland (Dagsson-Waldhauserova et al., 2013). In total, over 34 dust days per year on average occurred in Iceland based on conventionally used synoptic codes for dust observations. However, frequent volcanic eruptions, with the re-suspension of volcanic materials and dust haze, increased the number of dust events fourfold (135 dust days annually). The position of the Icelandic Low determined whether dust events occurred in the NE (16.4 dust days annually) or in the southern (S) part of Iceland (about 18 dust days annually). The decade with the most frequent dust days in S Iceland was the 1960s, but the 2000s in NE Iceland. A total of 32 severe dust storms (visibility < 500 m) were observed in Iceland with the highest frequency of events during the 2000s in S Iceland. The Arctic dust events (NE Iceland) were typically warm, occurring during summer/autumn (May-September) and during mild southwesterly winds, while the subarctic dust events (S Iceland) were mainly cold, occurring during winter/spring (March-May) and during strong northeasterly winds. About half of the dust events in S Iceland occurred in winter or at sub-zero temperatures. A good correlation was found between particulate matter (PM10) concentrations and visibility during dust observations at the stations Vík and Stórhöfði. This study shows that Iceland is among the dustiest areas of the world and that dust is emitted year-round.

  16. Impacts of interactive dust and its direct radiative forcing on interannual variations of temperature and precipitation in winter over East Asia: Impacts of Dust on IAVs of Temperature

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Lou, Sijia; Russell, Lynn M.; Yang, Yang

    We used 150-year pre-industrial simulations of the Community Earth System Model (CESM) to quantify the impacts of interactively-modeled dust emissions on the interannual variations of temperature and precipitation over East Asia during the East Asian Winter Monsoon (EAWM) season. The simulated December-January-February dust column burden and dust optical depth are lower over northern China in the strongest EAWM years than those of the weakest years, with regional mean values lower by 38.3% and 37.2%, respectively. The decrease in dust over the dust source regions (the Taklamakan and Gobi Deserts) and the downwind region (such as the North China Plain) leadsmore » to an increase in direct radiative forcing (RF) both at the surface and top of atmosphere by up to 1.5 and 0.75 W m-2, respectively. The effects of EAWM-related variations in surface winds, precipitation and their effects on dust emissions and wet removal contribute about 67% to the total dust-induced variations of direct RF at the surface and partly offset the cooling that occurs with the EAWM strengthening by heating the surface. The variations of surface air temperature induced by the changes in wind and dust emissions increase by 0.4-0.6 K over eastern coastal China, northeastern China, and Japan, which weakens the impact of EAWM on surface air temperature by 3–18% in these regions. The warming results from the combined effects of changes in direct RF and easterly wind anomalies that bring warm air from the ocean to these regions. Moreover, the feedback of the changes in wind on dust emissions weakens the variations of the sea level pressure gradient on the Siberian High while enhancing the Maritime Continent Low. Therefore, cold air is prevented from being transported from Siberia, Kazakhstan, western and central China to the western Pacific Ocean and decreases surface air temperature by 0.6 K and 2 K over central China and the Tibetan Plateau, respectively. Over eastern coastal China, the

  17. Constraining the Origin and Heating Mechanism of Dust in Type IIn Supernovae

    NASA Astrophysics Data System (ADS)

    Fox, Ori; Skrutskie, Michael; Filippenko, Alex

    2012-12-01

    More than any other supernova subclass, Type IIn supernovae tend to exhibit late-time (>1 year) infrared emission from warm dust. Identifying the origin and heating mechanism of the dust provides an important probe of the supernova explosion, circumstellar environment, and progenitor system. Yet mid-infrared observations, which span the peak of the thermal emission, are rare. Three years ago, we executed a warm Spitzer survey (P60122) that uncovered a unique sample of ten supernovae with unreported late-time infrared excesses, in some cases more than 5 years post-explosion. The data from this single epoch are most consistent with a pre-existing dust shell that is continuously heated by visible and/or X-ray emission generated by ongoing shock interaction. Furthermore, the lack of any detections beyond ~2000 days suggests the dust is destroyed once the forward shock overruns the pre-existing shell. The actual shell sizes remain unknown, however, since the derived blackbody radii offer only lower limits. Last year, we obtained second epoch observations of these ten re-discovered SNe IIn (plus the well-studied Type IIn SN 2010jl). The project aimed for non-detections to constrain the light-curve ``turn-off'' times and, thereby, the shell sizes and progenitor mass-loss models. Only two SNe (2005gn and 2008J), however, went undetected. The other nine SNe remain bright at mid-IR wavelengths, which means the dust shell radii are larger than expected. Here we propose continued monitoring of these nine SNe IIn to constrain the size of the circumstellar dust shell and characterize the supernova progenitor system. We can obtain all the necessary data in only 6.1 hours of observation.

  18. Possible influence of dust on hurricane genesis

    NASA Astrophysics Data System (ADS)

    Bretl, Sebastian; Reutter, Philipp; Raible, Christoph C.; Ferrachat, Sylvaine; Lohmann, Ulrike

    2014-05-01

    Tropical Cyclones (TCs) belong to the most extreme events in nature. In the past decade, the possible impact of dust on Atlantic hurricanes receives growing interest. As mineral dust is able to absorb incoming solar radiation and therefore warm the surrounding air, the presence of dust can lead to a reduction of sea surface temperature (SST) and an increase in atmospheric stability. Furthermore, resulting baroclinic effects and the dry Saharan easterly jet lead to an enhanced vertical shear of the horizontal winds. SST, stability, moisture and vertical wind shear are known to potentially impact hurricane activity. But how Saharan dust influences these prerequisites for hurricane formation is not yet clear. Some dynamical mechanisms induced by the SAL might even strengthen hurricanes. An adequate framework for investigating the possible impact of dust on hurricanes is comparing high resolution simulations (~0.5°x0.5°, 31 vertical levels) with and without radiatively active dust aerosols. To accomplish this task, we are using the general circulation model ECHAM6 coupled to a modified version of the aerosol model HAM, ECHAM6-HAM-Dust. Instead of the five aerosol species HAM normally contains, the modified version takes only insoluble dust into account, but modifies the scavenging parameters in order to have a similar lifetime of dust as in the full ECHAM6-HAM. All remaining aerosols are prescribed. To evaluate the effects of dust on hurricanes, a TC detection and tracking method is applied on the results. ECHAM6-HAM-Dust was used in two configurations, one with radiatively active dust aerosols and one with dust being not radiatively active. For both set-ups, 10 Monte-Carlo simulations of the year 2005 were performed. A statistical method which identifies controlling parameters of hurricane genesis was applied on North Atlantic developing and non-developing disturbances in all simulations, comparing storms in the two sets of simulations. Hereby, dust can be assigned

  19. Dust evolution from comets

    NASA Technical Reports Server (NTRS)

    Sekanina, Z.

    1976-01-01

    The studies of the evolution of cometary debris are reviewed. The subject is divided into three major sections: (1) the developments in the immediate vicinity of the cometary nucleus, which is the source of the dust; (2) the formation of the dust tail; and (3) the blending of the debris with the dust component of interplanetary matter. The importance of the physical theory of comets is emphasized for the understanding of the early phase of evolution. A physico-dynamical model designed to analyze the particle-emission mechanism from the distribution of light in the dust tail is described and the results are presented. Increased attention is paid to large particles because of their importance for the evolution of the zodiacal cloud. Finally, implications are discussed for the future in situ investigations of comets.

  20. MECA Workshop on Dust on Mars 3

    NASA Technical Reports Server (NTRS)

    Lee, Steven (Editor)

    1989-01-01

    Articles and abstracts of articles presented at this workshop are given. It was the goal of the workshop to stimulate cooperative research on, and discussion of, dust related processes on Mars, and to provide background information and help in planning of the Mars Observer mission. These topics are considered: How is dust ejected from the Martian surface into the atmosphere; How does the global atmospheric circulation affect the redistribution of dust on Mars; Are there sources and sinks of dust on Mars, if so, where are they and how do they vary in time; and How many components of dust are there on Mars, and what are their properties. There were four primary discussion sessions: (1) Dust in the atmosphere; (2) Dust on the surface; (3) Dust properties; and (4) Dust observations from future spacecraft missions.

  1. The Implementation of NEMS GFS Aerosol Component (NGAC) Version 1.0 for Global Dust Forecasting at NOAA NCEP

    NASA Technical Reports Server (NTRS)

    Lu, Cheng-Hsuan; Da Silva, Arlindo M.; Wang, Jun; Moorthi, Shrinivas; Chin, Mian; Colarco, Peter; Tang, Youhua; Bhattacharjee, Partha S.; Chen, Shen-Po; Chuang, Hui-Ya; hide

    2016-01-01

    The NOAA National Centers for Environmental Prediction (NCEP) implemented the NOAA Environmental Modeling System (NEMS) Global Forecast System (GFS) Aerosol Component (NGAC) for global dust forecasting in collaboration with NASA Goddard Space Flight Center (GSFC). NGAC Version 1.0 has been providing 5-day dust forecasts at 1deg x 1deg resolution on a global scale, once per day at 00:00 Coordinated Universal Time (UTC), since September 2012. This is the first global system capable of interactive atmosphere aerosol forecasting at NCEP. The implementation of NGAC V1.0 reflects an effective and efficient transitioning of NASA research advances to NCEP operations, paving the way for NCEP to provide global aerosol products serving a wide range of stakeholders, as well as to allow the effects of aerosols on weather forecasts and climate prediction to be considered.

  2. New directions: Mineral dust and ozone - Heterogeneous chemistry

    NASA Astrophysics Data System (ADS)

    Ramachandran, S.

    2015-04-01

    Aerosols, the tiny solid or liquid particles suspended in air and produced from natural sources and anthropogenic activities, continue to contribute the largest uncertainty to radiative forcing (IPCC, 2013). Aerosol particles give rise to radiative forcing directly through scattering and absorption of solar and infrared radiation in the atmosphere. Aerosols also give rise to indirect radiative forcing by modifying the cloud optical properties and lifetimes. Among the aerosol species mineral dust and black carbon cause a warming (positive forcing) while sulphate and sea salt cause a cooling (negative forcing) of the Earth-atmosphere system. In tropics and sub-tropics mineral dust is a major contributor to aerosol loading and optical thickness. The global source strength of dust aerosol varies significantly on spatial and temporal scales. The source regions of dust are mainly deserts, dry lake beds, and semi-arid regions, in addition to drier regions where vegetation has been reduced or soil surfaces that are disturbed by man made activities. Anthropogenic activities mainly related to agriculture such as harvesting, ploughing, overgrazing, and cement production and transport also produce mineral dust. An estimated 2500 terragram (Tg, 1012 g) of mineral dust is emitted into the atmosphere per year, and dominates the aerosol mass over continental regions in south Asia and China accounting for ∼35% of the total aerosol mass (IPCC, 2013). In India, dust is prevalent throughout the north and western India during the year and peaks during premonsoon season.

  3. Ubiquitous Instabilities of Dust Moving in Magnetized Gas

    NASA Astrophysics Data System (ADS)

    Hopkins, Philip F.; Squire, Jonathan

    2018-06-01

    Squire & Hopkins (2017) showed that coupled dust-gas mixtures are generically subject to "resonant drag instabilities" (RDIs), which drive violently-growing fluctuations in both. But the role of magnetic fields and charged dust has not yet been studied. We therefore explore the RDI in gas which obeys ideal MHD and is coupled to dust via both Lorentz forces and drag, with an external acceleration (e.g., gravity, radiation) driving dust drift through gas. We show this is always unstable, at all wavelengths and non-zero values of dust-to-gas ratio, drift velocity, dust charge, "stopping time" or drag coefficient (for any drag law), or field strength; moreover growth rates depend only weakly (sub-linearly) on these parameters. Dust charge and magnetic fields do not suppress instabilities, but give rise to a large number of new instability "families," each with distinct behavior. The "MHD-wave" (magnetosonic or Alfvén) RDIs exhibit maximal growth along "resonant" angles where the modes have a phase velocity matching the corresponding MHD wave, and growth rates increase without limit with wavenumber. The "gyro" RDIs are driven by resonances between drift and Larmor frequencies, giving growth rates sharply peaked at specific wavelengths. Other instabilities include "acoustic" and "pressure-free" modes (previously studied), and a family akin to cosmic ray instabilities which appear when Lorentz forces are strong and dust streams super-Alfvénically along field lines. We discuss astrophysical applications in the warm ISM, CGM/IGM, HII regions, SNe ejecta/remnants, Solar corona, cool-star winds, GMCs, and AGN.

  4. Dust Generation Resulting from Desiccation of Playa Systems: Studies on Mono and Owens Lakes, California

    NASA Astrophysics Data System (ADS)

    Gill, Thomas Edward

    1995-01-01

    Playas, evaporites, and aeolian sediments frequently are linked components within the Earth system. Anthropogenic water diversions from terminal lakes form playas that release fugitive dust. These actions, documented worldwide, simulate aeolian processes activated during palaeoclimatic pluvial/interpluvial transitions, and have significant environmental impacts. Pluvial lakes Russell and Owens in North America's Great Basin preceded historic Mono and Owens Lakes, now desiccated by water diversions into dust-generating, evaporite -encrusted playas. Geochemical and hydrologic cycles acting on the Owens (Dry) Lake playa form three distinct crust types each year. Although initial dust production results from deflation of surface efflorescences after the playa dries, most aerosols are created by saltation abrasion of salt/silt/clay crusts at crust/ sand sheet contacts. The warm-season, clastic "cemented" crust is slowest to degrade into dust. If the playa surface is stabilized by an unbroken, non-efflorescent crust, dust formation is discouraged. When Mono Lake's surFace elevation does not exceed 1951 meters (6400 feet), similar processes will also generate dust from its saline lower playa. Six factors--related to wind, topography, groundwater, and sediments--control dust formation at both playas. These factors were combined into a statistical model relating suspended dust concentrations to playa/lake morphometry. The model shows the extent and severity of Mono Lake dust storms expands significantly below the surface level 6376 feet (1943.5 meters). X-ray diffraction analysis of Mono Basin soils, playa sediments, and aerosols demonstrates geochemical cycling of materials through land, air and water during Mono Lake's 1982 low stand. Soils and clastic playa sediments contain silicate minerals and tephra. Saline groundwater deposited calcite, halite, thenardite, gaylussite, burkeite and glauberite onto the lower playa. Aerosols contained silicate minerals (especially

  5. [Effects of Loquat-Branch Dust Substitution on Ganoderma lucidum Cultivation in Its Main Active Components].

    PubMed

    Zhang, Ping; Chen, Feng; Lai, Teng-qiang; Jin, Ling-yun; Li, Ye

    2015-12-01

    To select the best Ganoderma lucidum cultivation medium of replacing sawdust into loquat-branch dust, in order to realize high output and high quality production of Ganoderma lucidum. Loquat-branch dust was added as substitution in Ganoderma lucidum cultivation, its effects on the biomass and the content of Ganoderma polysaccharides, triterpenoids and flavonoids were analyzed. By using loquat-branch dust in culture, Ganoderma lucidum grew well with normal fruiting body obtained and spores released. Compared with control group, the biological efficiency was increased by 11.34%, when the addition of the loquat-branch dust was 80%, while the amount of spore had little difference. When the addition of the loquat-branch dust was 90%, the content of Ganoderma polysaccharides and triterpenoids was increased by 32.29% and 30.58% respectively, while the efficiency of flavonoids had little difference. Using loquat-branch dust cultivation can improve the quality of Ganoderma lucidum. According to the comprehensive score, 80% loquat-branch dust is the most suitable cultivation medium.

  6. Swirling Dust in Gale Crater, Mars, Sol 1613

    NASA Image and Video Library

    2017-02-27

    This frame from a sequence of images shows a dust-carrying whirlwind, called a dust devil, on lower Mount Sharp inside Gale Crater, as viewed by NASA's Curiosity Mars Rover during the summer afternoon of the rover's 1,613rd Martian day, or sol (Feb. 18, 2017). Set within a broader southward view from the rover's Navigation Camera, the rectangular area outlined in black was imaged multiple times over a span of several minutes to check for dust devils. Images from the period with most activity are shown in the inset area. The images are in pairs that were taken about 12 seconds apart, with an interval of about 90 seconds between pairs. Timing is accelerated and not fully proportional in this animation. Contrast has been modified to make frame-to-frame changes easier to see. A black frame provides a marker between repeats of the sequence. On Mars as on Earth, dust devils result from sunshine warming the ground, prompting convective rising of air that has gained heat from the ground. Observations of dust devils provide information about wind directions and interaction between the surface and the atmosphere. An animation is available at http://photojournal.jpl.nasa.gov/catalog/PIA21483

  7. Gusev Dust Devil Movie, Sol 459 (Enhanced)

    NASA Technical Reports Server (NTRS)

    2005-01-01

    This movie clip shows a dust devil scooting across a plain inside Gusev Crater on Mars as seen from the NASA rover Spirit's hillside vantage point during the rover's 459th martian day, or sol (April 18, 2005). The individual images were taken about 20 seconds apart by Spirit's navigation camera, and the contrast has been enhanced for anything in the images that changes from frame to frame, that is, for the dust devil.

    The movie results from a new way of watching for dust devils, which are whirlwinds that hoist dust from the surface into the air. Spirit began seeing dust devils in isolated images in March 2005. At first, the rover team relied on luck. It might catch a dust devil in an image or it might miss by a few minutes. Using the new detection strategy, the rover takes a series of 21 images. Spirit sends a few of them to Earth, as well as little thumbnail images of all of them. Team members use the 3 big images and all the small images to decide whether the additional big images have dust devils. For this movie, they specifically told Spirit to send back frames that they knew had dust devils.

    The images were processed in three steps. All images were calibrated to remove known camera artifacts. The images were then processed to remove stationary objects. The result is a gray scene showing only features that change with time. The final step combined the original image with the image that shows only moving features, showing the martian scene and the enhanced dust devils.

    Scientists expected dust devils since before Spirit landed. The landing area inside Gusev Crater is filled with dark streaks left behind when dust devils pick dust up from an area. It is also filled with bright 'hollows,' which are dust-filled miniature craters. Dust covers most of the terrain. Winds flow into and out of Gusev crater every day. The Sun heats the surface so that the surface is warm to the touch even though the atmosphere at 2 meters (6 feet) above the surface

  8. Gusev Dust Devil Movie, Sol 456 (Enhanced)

    NASA Technical Reports Server (NTRS)

    2005-01-01

    This movie clip shows a dust devil scooting across a plain inside Gusev Crater on Mars as seen from the NASA rover Spirit's hillside vantage point during the rover's 456th martian day, or sol (April 15, 2005). The individual images were taken about 20 seconds apart by Spirit's navigation camera, and the contrast has been enhanced for anything in the images that changes from frame to frame, that is, for the dust devil.

    The movie results from a new way of watching for dust devils, which are whirlwinds that hoist dust from the surface into the air. Spirit began seeing dust devils in isolated images in March 2005. At first, the rover team relied on luck. It might catch a dust devil in an image or it might miss by a few minutes. Using the new detection strategy, the rover takes a series of 21 images. Spirit sends a few of them to Earth, as well as little thumbnail images of all of them. Team members use the 3 big images and all the small images to decide whether the additional big images have dust devils. For this movie, they specifically told Spirit to send back frames that they knew had dust devils.

    The images were processed in three steps. All images were calibrated to remove known camera artifacts. The images were then processed to remove stationary objects. The result is a gray scene showing only features that change with time. The final step combined the original image with the image that shows only moving features, showing the martian scene and the enhanced dust devils.

    Scientists expected dust devils since before Spirit landed. The landing area inside Gusev Crater is filled with dark streaks left behind when dust devils pick dust up from an area. It is also filled with bright 'hollows,' which are dust-filled miniature craters. Dust covers most of the terrain. Winds flow into and out of Gusev crater every day. The Sun heats the surface so that the surface is warm to the touch even though the atmosphere at 2 meters (6 feet) above the surface

  9. Warm Debris Disks from WISE

    NASA Technical Reports Server (NTRS)

    Padgett, Deborah L.

    2011-01-01

    "The Wide Field Infrared Survey Explorer (WISE) has just completed a sensitive all-sky survey in photometric bands at 3.4, 4.6, 12, and 22 microns. We report on a preliminary investigation of main sequence Hipparcos and Tycho catalog stars with 22 micron emission in excess of photospheric levels. This warm excess emission traces material in the circumstellar region likely to host terrestrial planets and is preferentially found in young systems with ages < 1 Gyr. Nearly a hundred new warm debris disk candidates are detected among FGK stars and a similar number of A stars within 120 pc. We are in the process of obtaining spectra to determine spectral types and activity level of these stars and are using HST, Herschel and Keck to characterize the dust, multiplicity, and substellar companions of these systems. In this contribution, we will discuss source selection methods and individual examples from among the WISE debris disk candidates. "

  10. Warm fresh whole blood and thoracic traumain iraq and afghanistan.

    PubMed

    Keneally, Ryan J; Parsons, Andrew M; Willett, Peter B

    2015-01-01

    Thoracic trauma occurred in 10% of the patients seen at US military treatment facilities in Iraq and Afghanistan and 52% of those patients were transfused. Among those transfused, 281 patients received warm fresh whole blood. A previous report documented improved survival with warm fresh whole blood in patients injured in combat without stratification by injury pattern. A later report described an increase in acute lung injuries after its administration. Survivorship and warm fresh whole blood have never been analyzed in a subpopulation at highest risk for lung injuries, such as patients with thoracic trauma. There may be a heterogeneous relationship between whole blood and survival based on likelihood of a concomitant pulmonary injury. In this report, the relationship between warm fresh whole blood and survivorship was analyzed among patients at highest risk for concomitant pulmonary injuries. Patients with thoracic trauma who received a transfusion were identified in the Joint Theater Trauma Registry. Gross mortality rates were compared between whole blood recipients and patients transfused with component therapy only. The association between each blood component and mortality was determined in a regression model. The overall mortality risk was compared between warm fresh whole blood recipients and non-recipients. Patients transfused with warm fresh whole blood in addition to component therapy had a higher mortality rate than patients transfused only separated blood components (21.3% vs. 12.8%, P < 0.001). When controlling for covariates, transfusion of warm fresh whole blood in addition to component therapy was not associated with increased mortality risk compared with the transfusion of component therapy only (OR 1.247 [95% CI 0.760-2.048], P = 0.382). Patients with combat related thoracic trauma transfused with warm fresh whole blood were not at increased risk for mortality compared to those who received component therapy alone when controlling for covariates.

  11. Simulating southwestern U.S. desert dust influences on supercell thunderstorms

    NASA Astrophysics Data System (ADS)

    Lerach, David G.; Cotton, William R.

    2018-05-01

    Three-dimensional numerical simulations were performed to evaluate potential southwestern U.S. dust indirect microphysical and direct radiative impacts on a real severe storms outbreak. Increased solar absorption within the dust plume led to modest increases in pre-storm atmospheric stability at low levels, resulting in weaker convective updrafts and less widespread precipitation. Dust microphysical impacts on convection were minor in comparison, due in part to the lofted dust concentrations being relatively few in number when compared to the background (non-dust) aerosol population. While dust preferentially serving as cloud condensation nuclei (CCN) versus giant CCN had opposing effects on warm rain production, both scenarios resulted in ample supercooled water and subsequent glaciation aloft, yielding larger graupel and hail. Associated latent heating from condensation and freezing contributed little to overall updraft invigoration. With reduced rain production overall, the simulations that included dust effects experienced slightly reduced grid-cumulative precipitation and notably warmer and spatially smaller cold pools. Dust serving as ice nucleating particles did not appear to play a significant role. The presence of dust ultimately reduced the number of supercells produced but allowed for supercell evolution characterized by consistently higher values of relative vertical vorticity within simulated mesocyclones. Dust radiative and microphysical effects were relatively small in magnitude when compared to those from altering the background convective available potential energy and vertical wind shear. It is difficult to generalize such findings from a single event, however, due to a number of case-specific environmental factors. These include the nature of the low-level moisture advection and characteristics of the background aerosol distribution.

  12. Dust: Small-scale processes with global consequences

    USGS Publications Warehouse

    Okin, G.S.; Bullard, J.E.; Reynolds, R.L.; Ballantine, J.-A.C.; Schepanski, K.; Todd, M.C.; Belnap, J.; Baddock, M.C.; Gill, T.E.; Miller, M.E.

    2011-01-01

    Desert dust, both modern and ancient, is a critical component of the Earth system. Atmospheric dust has important effects on climate by changing the atmospheric radiation budget, while deposited dust influences biogeochemical cycles in the oceans and on land. Dust deposited on snow and ice decreases its albedo, allowing more light to be trapped at the surface, thus increasing the rate of melt and influencing energy budgets and river discharge. In the human realm, dust contributes to the transport of allergens and pathogens and when inhaled can cause or aggravate respiratory diseases. Dust storms also represent a significant hazard to road and air travel. Because it affects so many Earth processes, dust is studied from a variety of perspectives and at multiple scales, with various disciplines examining emissions for different purposes using disparate strategies. Thus, the range of objectives in studying dust, as well as experimental approaches and results, has not yet been systematically integrated. Key research questions surrounding the production and sources of dust could benefit from improved collaboration among different research communities. These questions involve the origins of dust, factors that influence dust production and emission, and methods through which dust can be monitored. ?? Author(s) 2011.

  13. Dust particle radial confinement in a dc glow discharge.

    PubMed

    Sukhinin, G I; Fedoseev, A V; Antipov, S N; Petrov, O F; Fortov, V E

    2013-01-01

    A self-consistent nonlocal model of the positive column of a dc glow discharge with dust particles is presented. Radial distributions of plasma parameters and the dust component in an axially homogeneous glow discharge are considered. The model is based on the solution of a nonlocal Boltzmann equation for the electron energy distribution function, drift-diffusion equations for ions, and the Poisson equation for a self-consistent electric field. The radial distribution of dust particle density in a dust cloud was fixed as a given steplike function or was chosen according to an equilibrium Boltzmann distribution. The balance of electron and ion production in argon ionization by an electron impact and their losses on the dust particle surface and on the discharge tube walls is taken into account. The interrelation of discharge plasma and the dust cloud is studied in a self-consistent way, and the radial distributions of the discharge plasma and dust particle parameters are obtained. It is shown that the influence of the dust cloud on the discharge plasma has a nonlocal behavior, e.g., density and charge distributions in the dust cloud substantially depend on the plasma parameters outside the dust cloud. As a result of a self-consistent evolution of plasma parameters to equilibrium steady-state conditions, ionization and recombination rates become equal to each other, electron and ion radial fluxes become equal to zero, and the radial component of electric field is expelled from the dust cloud.

  14. Dust trap formation in a non-self-sustained discharge with external gas ionization

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Filippov, A. V., E-mail: fav@triniti.ru; Babichev, V. N.; Pal’, A. F.

    2015-11-15

    Results from numerical studies of a non-self-sustained gas discharge containing micrometer dust grains are presented. The non-self-sustained discharge (NSSD) was controlled by a stationary fast electron beam. The numerical model of an NSSD is based on the diffusion drift approximation for electrons and ions and self-consistently takes into account the influence of the dust component on the electron and ion densities. The dust component is described by the balance equation for the number of dust grains and the equation of motion for dust grains with allowance for the Stokes force, gravity force, and electric force in the cathode sheath. Themore » interaction between dust grains is described in the self-consistent field approximation. The height of dust grain levitation over the cathode is determined and compared with experimental results. It is established that, at a given gas ionization rate and given applied voltage, there is a critical dust grain size above which the levitation condition in the cathode sheath cannot be satisfied. Simulations performed for the dust component consisting of dust grains of two different sizes shows that such grains levitate at different heights, i.e., size separation of dust drains levitating in the cathode sheath of an NSSD takes place.« less

  15. Heating of Porous Icy Dust Aggregates

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sirono, Sin-iti

    At the beginning of planetary formation, highly porous dust aggregates are formed through coagulation of dust grains. Outside the snowline, the main component of an aggregate is H{sub 2}O ice. Because H{sub 2}O ice is formed in amorphous form, its thermal conductivity is extremely small. Therefore, the thermal conductivity of an icy dust aggregate is low. There is a possibility of heating inside an aggregate owing to the decay of radionuclides. It is shown that the temperature increases substantially inside an aggregate, leading to crystallization of amorphous ice. During the crystallization, the temperature further increases sufficiently to continue sintering. Themore » mechanical properties of icy dust aggregates change, and the collisional evolution of dust aggregates is affected by the sintering.« less

  16. Martian Dust Devil Action in Gale Crater, Sol 1597

    NASA Image and Video Library

    2017-02-27

    This frame from a sequence of images shows a dust-carrying whirlwind, called a dust devil, scooting across the ground inside Gale Crater, as observed on the local summer afternoon of NASA's Curiosity Mars Rover's 1,597th Martian day, or sol (Feb. 1, 2017). Set within a broader southward view from the rover's Navigation Camera, the rectangular area outlined in black was imaged multiple times over a span of several minutes to check for dust devils. Images from the period with most activity are shown in the inset area. The images are in pairs that were taken about 12 seconds apart, with an interval of about 90 seconds between pairs. Timing is accelerated and not fully proportional in this animation. A dust devil is most evident in the 10th, 11th and 12th frames. In the first and fifth frames, dust blowing across the ground appears as pale horizontal streak. Contrast has been modified to make frame-to-frame changes easier to see. A black frame is added between repeats of the sequence. On Mars as on Earth, dust devils are whirlwinds that result from sunshine warming the ground, prompting convective rising of air that has gained heat from the ground. Observations of Martian dust devils provide information about wind directions and interaction between the surface and the atmosphere. An animation is available at http://photojournal.jpl.nasa.gov/catalog/PIA21270

  17. The past, present and future of African dust.

    PubMed

    Evan, Amato T; Flamant, Cyrille; Gaetani, Marco; Guichard, Françoise

    2016-03-24

    African dust emission and transport exhibits variability on diurnal to decadal timescales and is known to influence processes such as Amazon productivity, Atlantic climate modes, regional atmospheric composition and radiative balance and precipitation in the Sahel. To elucidate the role of African dust in the climate system, it is necessary to understand the factors governing its emission and transport. However, African dust is correlated with seemingly disparate atmospheric phenomena, including the El Niño/Southern Oscillation, the North Atlantic Oscillation, the meridional position of the intertropical convergence zone, Sahelian rainfall and surface temperatures over the Sahara Desert, all of which obfuscate the connection between dust and climate. Here we show that the surface wind field responsible for most of the variability in North African dust emission reflects the topography of the Sahara, owing to orographic acceleration of the surface flow. As such, the correlations between dust and various climate phenomena probably arise from the projection of the winds associated with these phenomena onto an orographically controlled pattern of wind variability. A 161-year time series of dust from 1851 to 2011, created by projecting this wind field pattern onto surface winds from a historical reanalysis, suggests that the highest concentrations of dust occurred from the 1910s to the 1940s and the 1970s to the 1980s, and that there have been three periods of persistent anomalously low dust concentrations--in the 1860s, 1950s and 2000s. Projections of the wind pattern onto climate models give a statistically significant downward trend in African dust emission and transport as greenhouse gas concentrations increase over the twenty-first century, potentially associated with a slow-down of the tropical circulation. Such a dust feedback, which is not represented in climate models, may be of benefit to human and ecosystem health in West Africa via improved air quality and

  18. Warm Debris Disk Candidates from WISE

    NASA Technical Reports Server (NTRS)

    Padgett, Deborah; Stapelfeldt, Karl; Liu, Wilson; Leisawitz, David

    2011-01-01

    The Wide Field Infrared Survey Explorer (WISE) has just completed a sensitive all-sky survey in photometric bands at 3.4, 4.6, 12, and 22 microns. We report on a preliminary investigation of main sequence Hipparcos and Tycho catalog stars with 22 micron emission in excess of photospheric levels. This warm excess emission traces material in the circumstellar region likely to host terrestrial planets and is preferentially found in young systems with ages < 1 Gyr. Nearly a hundred new warm debris disk candidates are detected among FGK stars and 150 A stars within 120 pc. We are in the process of obtaining spectra to determine spectral types and activity level of these stars and are using HST, Herschel and Keck to characterize the dust, multiplicity, and substellar companions of these systems. In this contribution, we will discuss source selection methods and individual examples from among the WISE debris disk candidates.

  19. HERSCHEL OBSERVATIONS OF GAS AND DUST IN THE UNUSUAL 49 Ceti DEBRIS DISK

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Roberge, A.; Kamp, I.; Montesinos, B.

    2013-07-01

    We present far-IR/sub-mm imaging and spectroscopy of 49 Ceti, an unusual circumstellar disk around a nearby young A1V star. The system is famous for showing the dust properties of a debris disk, but the gas properties of a low-mass protoplanetary disk. The data were acquired with the Herschel Space Observatory PACS and SPIRE instruments, largely as part of the ''Gas in Protoplanetary Systems'' (GASPS) Open Time Key Programme. Disk dust emission is detected in images at 70, 160, 250, 350, and 500 {mu}m; 49 Cet is significantly extended in the 70 {mu}m image, spatially resolving the outer dust disk formore » the first time. Spectra covering small wavelength ranges centered on eight atomic and molecular emission lines were obtained, including [O I] 63 {mu}m and [C II] 158 {mu}m. The C II line was detected at the 5{sigma} level-the first detection of atomic emission from the disk. No other emission lines were seen, despite the fact that the O I line is the brightest one observed in Herschel protoplanetary disk spectra. We present an estimate of the amount of circumstellar atomic gas implied by the C II emission. The new far-IR/sub-mm data fills in a large gap in the previous spectral energy distribution (SED) of 49 Cet. A simple model of the new SED confirms the two-component structure of the disk: warm inner dust and cold outer dust that produces most of the observed excess. Finally, we discuss preliminary thermochemical modeling of the 49 Cet gas/dust disk and our attempts to match several observational results simultaneously. Although we are not yet successful in doing so, our investigations shed light on the evolutionary status of the 49 Cet gas, which might not be primordial gas but rather secondary gas coming from comets.« less

  20. Aliphatic Hydrocarbon Content of Interstellar Dust

    NASA Astrophysics Data System (ADS)

    Günay, B.; Schmidt, T. W.; Burton, M. G.; Afşar, M.; Krechkivska, O.; Nauta, K.; Kable, S. H.; Rawal, A.

    2018-06-01

    There is considerable uncertainty as to the amount of carbon incorporated in interstellar dust. The aliphatic component of the carbonaceous dust is of particular interest because it produces a significant 3.4 μm absorption feature when viewed against a background radiation source. The optical depth of the 3.4 μm absorption feature is related to the number of aliphatic carbon C-H bonds along the line of sight. It is possible to estimate the column density of carbon locked up in the aliphatic hydrocarbon component of interstellar dust from quantitative analysis of the 3.4 μm interstellar absorption feature providing that the absorption coefficient of aliphatic hydrocarbons incorporated in the interstellar dust is known. We report laboratory analogues of interstellar dust by experimentally mimicking interstellar/circumstellar conditions. The resultant spectra of these dust analogues closely match those from astronomical observations. Measurements of the absorption coefficient of aliphatic hydrocarbons incorporated in the analogues were carried out by a procedure combining FTIR and 13C NMR spectroscopies. The absorption coefficients obtained for both interstellar analogues were found to be in close agreement (4.76(8) × 10-18 cm group-1 and 4.69(14) × 10-18 cm group-1), less than half those obtained in studies using small aliphatic molecules. The results thus obtained permit direct calibration of the astronomical observations, providing rigorous estimates of the amount of aliphatic carbon in the interstellar medium.

  1. Meteorological Situations Favouring the Development of Dust Plumes over Iceland

    NASA Astrophysics Data System (ADS)

    Schepanski, K.; Szodry, K.

    2017-12-01

    The knowledge on mineral dust emitted at high latitudes is limited, but its impact on the polar environments is divers. Within a warming climate, dust emitted from regions in cold climates is expected to increase due to the retreat of the ice sheet and increasing melting rates. Therefore, and for its extensive impacts on different aspects of the climate system, a better understanding of the atmospheric dust life-cycle at high latitudes/cold climates in general, and the spatio-temporal distribution of dust sources in particular, are essential. At high-latitudes, glacio-fluvial sediments as found on river flood plains e.g. supplied by glaciers are prone to wind erosion when dry and bare. In case of the occurrence of strong winds, sediments are blown out and dust plumes develop. As dust uplift is controlled by soil surface characteristics, the availability of suitable sediments, and atmospheric conditions, an interannual variability in dust source activity is expected. We investigated atmospheric circulation patterns that favour the development of dust plumes over Iceland, which presents a well-known dust source at high latitudes. Using the atmosphere model COSMO (COnsortium for Small-scale MOdeling), we analysed the wind speed distribution over the Iceland region for identified and documented dust cases. As one outcome of the study, the position of the Icelandic low, the anticyclones located over Northern Europe, and the resulting pressure gradients are of particular relevance. The interaction of the synoptic-scale winds with the Icelandic orography may locally enhance the wind speeds and thus foster local dust emission. Results from this study suggest that the atmospheric circulation determined by the pressure pattern is of particular relevance for the formation of dust plumes entering the North Atlantic.

  2. The role of atmospheric nuclear explosions on the stagnation of global warming in the mid 20th century

    NASA Astrophysics Data System (ADS)

    Fujii, Yoshiaki

    2011-04-01

    This study suggests that the cause of the stagnation in global warming in the mid 20th century was the atmospheric nuclear explosions detonated between 1945 and 1980. The estimated GST drop due to fine dust from the actual atmospheric nuclear explosions based on the published simulation results by other researchers (a single column model and Atmosphere-Ocean General Circulation Model) has served to explain the stagnation in global warming. Atmospheric nuclear explosions can be regarded as full-scale in situ tests for nuclear winter. The non-negligible amount of GST drop from the actual atmospheric explosions suggests that nuclear winter is not just a theory but has actually occurred, albeit on a small scale. The accuracy of the simulations of GST by IPCC would also be improved significantly by introducing the influence of fine dust from the actual atmospheric nuclear explosions into their climate models; thus, global warming behavior could be more accurately predicted.

  3. Dust Devils Seen Streaking Across Mars: PART II--They're the Work of the Devil!

    NASA Technical Reports Server (NTRS)

    2000-01-01

    [figure removed for brevity, see original site]

    [figure removed for brevity, see original site]

    In December 1999, the MOC team finally had an answer! A dust devil, shown in the above left figure, was caught in the act of creating a swirly, dark streak! An eerie sensation washed over the first team members who saw this picture--here was an event on Mars 'caught in the act' just hours before the picture was played back to Earth. A 'smoking gun.'

    The first dust devil seen making a streak--located in Promethei Terra (above, left)--was traveling from right (east) to left (west). A columnar shadow was cast by sunlight coming from the upper left. This shadow indicates the true shape of the dust devil. The bright dust devil itself does not look like a column because the picture was taken from a camera looking straight down on it. The dust devil is less than 100 meters (less than 100 yards) wide and the picture covers an area approximately 1.5 by 1.7 kilometers (about 1 by 1 mile).

    Dust devils are spinning, columnar vortices of wind that move across the landscape, pick up dust, and look somewhat like miniature tornadoes. Dust devils are a common occurrence in dry and desert landscapes on Earth as well as Mars. They form when the ground heats up during the day, warming the air immediately above the surface. As the warmed air nearest the surface begins to rise, it spins. The spinning column begins to move across the surface and picks up loose dust (if any is present). The dust makes the vortex visible and gives it the 'dust devil' or tornado-like appearance. On Earth, dust devils typically last for only a few minutes.

    The fourth picture (above, right) shows a surface in southwestern Terra Sirenum near 63oS, 168oW, that has seen the activity of so many dust devils that it looks like a plate of dark gray spaghetti. This image, taken in early summer during February 2000, covers an area 3 km wide and 30 km long (1.9 by 19 miles). In fact, a dust devil

  4. The Lunar Dust Pendulum

    NASA Technical Reports Server (NTRS)

    Kuntz, Kip; Collier, Michael R.; Stubbs, Timothy J.; Farrell, William M.

    2011-01-01

    Shadowed regions on the lunar surface acquire a negative potential. In particular, shadowed craters can have a negative potential with respect to the surrounding lunar regolith in sunlight, especially near the terminator regions. Here we analyze the motion of a positively charged lnnar dust grain in the presence of a shadowed crater at a negative potential in vacuum. Previous models describing the transport of charged lunar dust close to the surface have typically been limited to one-dimensional motion in the vertical direction, e.g. electrostatic levitation; however. the electric fields in the vicinity of shadowed craters will also have significant components in the horizontal directions. We propose a model that includes both the horizontal and vertical motion of charged dust grains near shadowed craters. We show that the dust grains execute oscillatory trajectories and present an expression for the period of oscillation drawing an analogy to the motion of a pendulum.

  5. The Lunar Dust Pendulum

    NASA Technical Reports Server (NTRS)

    Collier, Michael R.; Stubbs, Timothy J.; Farrell, William M.

    2011-01-01

    Shadowed regions on the lunar surface acquire a negative potential. In particular, shadowed craters can have a negative potential with respect to the surrounding lunar regolith in sunlight, especially near the terminator regions. Here we analyze the motion of a positively charged lunar dust grain in the presence of a shadowed crater at a negative potential in vacuum. Previous models describing the transport of charged lunar dust close to the surface have typically been limited to one-dimensional motion in the vertical direction, e.g. electrostatic levitation; however, the electric fields in the vicinity of shadowed craters will also have significant components in the horizontal directions. We propose a model that includes both the horizontal and vertical motion of charged dust grains near shadowed craters. We show that the dust grains execute oscillatory trajectories and present an expression for the period of oscillation drawing an analogy to the motion of a pendulum.

  6. [Asthma due to grain dust].

    PubMed

    Baur, X; Preisser, A; Wegner, R

    2003-06-01

    The actual literature as well as two case reports described in detail show that grain dust induces asthmatic reactions and ODTS which are obviously not of allergic origin. For diagnosis occupational-type exposure tests are decisive whereas allergological testing usually is not. Endotoxins which are present in the grain dust samples in high concentrations have to be regarded as the major causative components. To avoid irreversible lung function impairment a comprehensive early diagnosis is necessary. Generally, a remarkable reduction of exposure to dust with high levels of airborne endotoxin in agriculture has to be achieved since in many workplaces corresponding exposures are still rather high.

  7. Application of aerosol speciation data as an in situ dust proxy for validation of the Dust Regional Atmospheric Model (DREAM)

    NASA Astrophysics Data System (ADS)

    Shaw, Patrick

    The Dust REgional Atmospheric Model (DREAM) predicts concentrations of mineral dust aerosols in time and space, but validation is challenging with current in situ particulate matter (PM) concentration measurements. Measured levels of ambient PM often contain anthropogenic components as well as windblown mineral dust. In this study, two approaches to model validation were performed with data from preexisting air quality monitoring networks: using hourly concentrations of total PM with aerodynamic diameter less than 2.5 μm (PM 2.5); and using a daily averaged speciation-derived soil component. Validation analyses were performed for point locations within the cities of El Paso (TX), Austin (TX), Phoenix (AZ), Salt Lake City (UT) and Bakersfield (CA) for most of 2006. Hourly modeled PM 2.5 did not validate at all with hourly observations among the sites (combined R < 0.00, N = 24,302 hourly values). Aerosol chemical speciation data distinguished between mineral (soil) dust from anthropogenic ambient PM. As expected, statistically significant improvements in correlation among all stations (combined R = 0.16, N = 343 daily values) were found when the soil component alone was used to validate DREAM. The validation biases that result from anthropogenic aerosols were also reduced using the soil component. This is seen in the reduction of the root mean square error between hourly in situ versus hourly modeled (RMSE hourly = 18.6 μg m -3) and 24-h in situ speciation values versus daily averaged observed (RMSE soil = 12.0 μg m -3). However, the lack of a total reduction in RMSE indicates there is still room for improvement in the model. While the soil component is the theoretical proxy of choice for a dust transport model, the current sparse and infrequent sampling is not ideal for routine hourly air quality forecast validation.

  8. More on the dynamics of dust generation: the effects of mixing and sanding chrysotile, calcium carbonate, and other components on the characteristics of joint-compound dusts.

    PubMed

    Berman, D Wayne; Brorby, Gregory P; Sheehan, Patrick J; Bogen, Kenneth T; Holm, Stewart E

    2012-08-01

    An ongoing research effort designed to reconstruct the character of historical exposures associated with use of chrysotile-containing joint compounds naturally raised questions concerning how the character (e.g. particle size distributions) of dusts generated from use of recreated materials compares to dusts from similar materials manufactured historically. This also provided an opportunity to further explore the relative degree that the characteristics of dusts generated from a bulk material are mediated by the properties of the bulk material versus the mechanical processes applied to the bulk material by which the dust is generated. In the current study, the characteristics of dusts generated from a recreated ready mix and recreated dry mix were compared to each other, to dusts from a historical dry mix, and to dusts from the commercial chrysotile fiber (JM 7RF3) used in the recreated materials. The effect of sanding on the character of dusts generated from these materials was also explored. Dusts from the dry materials studied were generated and captured for analysis in a dust generator-elutriator. The recreated and historical joint compounds were also prepared, applied to drywall, and sanded inside sealed bags so that the particles produced from sanding could be introduced into the elutriator and captured for analysis. Comparisons of fiber size distributions in dusts from these materials suggest that dust from commercial fiber is different from dusts generated from the joint compounds, which are mixtures, and the differences persist whether the materials are sanded or not. Differences were also observed between sanded recreated ready mix and either the recreated dry mix or a historical dry mix, again whether sanded or not. In all cases, however, such differences disappeared when variances obtained from surrogate data were used to better represent the 'irreducible variation' of these materials. Even using the smaller study-specific variances, no differences were

  9. Improving dust emission characterization in dust models using dynamic high-resolution geomorphic erodibility map

    NASA Astrophysics Data System (ADS)

    Parajuli, S. P.; Yang, Z.; Kocurek, G.

    2013-12-01

    dust models associated with poor characterization of dust sources. The baseline dust scheme used in this study is the Dust Entrainment and Deposition (DEAD) model, which is also a component of the community land model (CLM). Proposed improvements in the dust emission representation will help to better understand the accurate effect of dust on climate processes.

  10. The Cosmic Dust Analyzer for Cassini

    NASA Technical Reports Server (NTRS)

    Bradley, James G.; Gruen, Eberhard; Srama, Ralf

    1996-01-01

    The Cosmic Dust Analyzer (CDA) is designed to characterize the dust environment in interplanetary space, in the Jovian and in the Saturnian systems. The instrument consists of two major components, the Dust Analyzer (DA) and the High Rate Detector (HRD). The DA has a large aperture to provide a large cross section for detection in low flux environments. The DA has the capability of determining dust particle mass, velocity, flight direction, charge, and chemical composition. The chemical composition is determined by the Chemical Analyzer system based on a time-of-flight mass spectrometer. The DA is capable of making full measurements up to one impact/second. The HRD contains two smaller PVDF detectors and electronics designed to characterize dust particle masses at impact rates up to 10(exp 4) impacts/second. These high impact rates are expected during Saturn ring, plane crossings.

  11. High Resolution IRAS Maps and IR Emission of M31 -- II. Diffuse Component and Interstellar Dust

    NASA Technical Reports Server (NTRS)

    Xu, C.; Helou, G.

    1995-01-01

    Large-scale dust heating and cooling in the diffuse medium of M31 is studied using the high resolution (HiRes) IRAS maps in conjunction with UV, optical (UBV), and the HI maps. A dust heating/cooling model is developed based on a radiative transfer model which assumes a 'Sandwich' configuration of dust and stars takes account of the effect of dust grain scattering.

  12. Nonlinear screening of dust grains and structurization of dusty plasma: II. formation and stability of dust structures

    NASA Astrophysics Data System (ADS)

    Tsytovich, V. N.; Gusein-zade, N. G.; Ignatov, A. M.

    2017-10-01

    The second part of the review on dust structures (the first part was published in Plasma Phys. Rep. 39, 515 (2013)) is devoted to experimental and theoretical studies on the stability of structures and their formation from the initially uniform dusty plasma components. The applicability limits of theoretical results and the role played by nonlinearity in the screening of dust grains are considered. The importance of nonlinearity is demonstrated by using numerous laboratory observations of planar clusters and volumetric dust structures. The simplest compact agglomerates of dust grains in the form of stable planar clusters are discussed. The universal character of instability resulting in the structurization of an initially uniform dusty plasma is shown. The fundamental correlations described in the first part of the review, supplemented with effects of dust inertia and dust friction by the neutral gas, are use to analyze structurization instability. The history of the development of theoretical ideas on the physics of the cluster formation for different types of interaction between dust grains is described.

  13. Foreground Bias from Parametric Models of Far-IR Dust Emission

    NASA Technical Reports Server (NTRS)

    Kogut, A.; Fixsen, D. J.

    2016-01-01

    We use simple toy models of far-IR dust emission to estimate the accuracy to which the polarization of the cosmic microwave background can be recovered using multi-frequency fits, if the parametric form chosen for the fitted dust model differs from the actual dust emission. Commonly used approximations to the far-IR dust spectrum yield CMB residuals comparable to or larger than the sensitivities expected for the next generation of CMB missions, despite fitting the combined CMB plus foreground emission to precision 0.1 percent or better. The Rayleigh-Jeans approximation to the dust spectrum biases the fitted dust spectral index by (Delta)(Beta)(sub d) = 0.2 and the inflationary B-mode amplitude by (Delta)(r) = 0.03. Fitting the dust to a modified blackbody at a single temperature biases the best-fit CMB by (Delta)(r) greater than 0.003 if the true dust spectrum contains multiple temperature components. A 13-parameter model fitting two temperature components reduces this bias by an order of magnitude if the true dust spectrum is in fact a simple superposition of emission at different temperatures, but fails at the level (Delta)(r) = 0.006 for dust whose spectral index varies with frequency. Restricting the observing frequencies to a narrow region near the foreground minimum reduces these biases for some dust spectra but can increase the bias for others. Data at THz frequencies surrounding the peak of the dust emission can mitigate these biases while providing a direct determination of the dust temperature profile.

  14. Testing of a Plasmadynamic Hypervelocity Dust Accelerator

    NASA Astrophysics Data System (ADS)

    Ticos, Catalin M.; Wang, Zhehui; Dorf, Leonid A.; Wurden, G. A.

    2006-10-01

    A plasmadynamic accelerator for microparticles (or dust grains) has been designed, built and tested at Los Alamos National laboratory. The dust grains are expected to be accelerated to hypervelocities on the order of 1-30 km/s, depending on their size. The key components of the plasmadynamic accelerator are a coaxial plasma gun operated at 10 kV, a dust dispenser activated by a piezoelectric transducer, and power and remote-control systems. The coaxial plasma gun produces a high density (10^18 cm-3) and low temperature (˜ 1 eV) plasma in deuterium ejected by J x B forces, which provides drag on the dust particles in its path. Carbon dust particles will be used, with diameters from 1 to 50 μm. The plasma parameters produced in the coaxial gun are presented and their implication to dust acceleration is discussed. High speed dust will be injected in the National Spherical Torus Experiment to measure the pitch angle of magnetic field lines.

  15. The Role of African Easterly Wave on Dust Transport and the Interaction Between Saharan Dust Layer and Atlantic ITCZ During Boreal Summer

    NASA Technical Reports Server (NTRS)

    Lau, William K. M.; Kim, Kyu-Myong

    2012-01-01

    In this paper, we investigate the relationships among Saharan dust outbreak and transport, African easterly waves (AEW), African easterly jet (AEJ) and associated convective activities of Atlantic Intertropical Convergence Zone (ITCZ) using Cloudsat-Calipso, MODIS and MERRA data. We find that a major Saharan dust outbreak is associated with the formation of a westward propagating strong cyclone around 15-25N over the western part northern Saharan. The strong cyclonic flow mobilizes and lifts the dust from the desert surface to a high elevation. As the cyclone propagate westward, it transports a thick elevated dust layer between 900 -500 hPa from the African continent to the eastern Atlantic. Cloudiness is reduced within the warm, dry dusty layer, but enhanced underneath it, possibly due to the presence of a shallow inversion layer over the marine boundary layer. The dust outbreak is linked to enhanced deep convection in the northern part of Atlantic ITCZ, abutting the southern flank of the dust layer, and a strengthening of the northward flank of the AEJ. As the dust layer spreads westward, it loses elevation and becomes increasing diffused as it reaches the central and western Atlantic. Using band pass filtered EOF analysis of MERRA winds, we find that AEWs propagating westward along two principal tracks, centered at 15-25N and 5-10N respectively. The easterly waves in the northern track are highly correlated with major dust outbreak over North Africa and associated with slower moving systems, with a quasi-periodicity of 6-9 day. On the other hand, easterly waves along the southern track are faster, with quasi-periodicity of 3-5 days. These faster easterly waves are closely tied to rainfall/cloud variations along the Atlantic ITCZ. Dust transport along the southern track by the faster waves generally leads rainfall/cloud anomalies in the same region by one or two days, suggesting the southern tracks of dust outbreak are regions of strong interaction between

  16. Global warming potential of pavements

    NASA Astrophysics Data System (ADS)

    Santero, Nicholas J.; Horvath, Arpad

    2009-09-01

    Pavements comprise an essential and vast infrastructure system supporting our transportation network, yet their impact on the environment is largely unquantified. Previous life-cycle assessments have only included a limited number of the applicable life-cycle components in their analysis. This research expands the current view to include eight different components: materials extraction and production, transportation, onsite equipment, traffic delay, carbonation, lighting, albedo, and rolling resistance. Using global warming potential as the environmental indicator, ranges of potential impact for each component are calculated and compared based on the information uncovered in the existing research. The relative impacts between components are found to be orders of magnitude different in some cases. Context-related factors, such as traffic level and location, are also important elements affecting the impacts of a given component. A strategic method for lowering the global warming potential of a pavement is developed based on the concept that environmental performance is improved most effectively by focusing on components with high impact potentials. This system takes advantage of the fact that small changes in high-impact components will have more effect than large changes in low-impact components.

  17. Understanding the dust properties in nearby galaxies

    NASA Astrophysics Data System (ADS)

    Decleir, Marjorie; Baes, Maarten; De Looze, Ilse; Camps, Peter

    2018-04-01

    Dust is a crucial component in the interstellar medium of galaxies. It regulates several physical and chemical processes. Dust grains are also efficient at absorbing and scattering ultraviolet/optical photons and then re-radiating the absorbed energy in the infrared/submm wavelength range. The spatial distribution and properties of dust in galaxies can hence be investigated in two complementary ways: by its attenuation effects at short wavelengths, and by its thermal emission at long wavelengths. Both approaches have their advantages and challenges. In this contribution, we discuss a number of recent interesting results on interstellar dust in nearby galaxies, obtained by our research group at Ghent University.

  18. Warming ancient Mars with water clouds

    NASA Astrophysics Data System (ADS)

    Hartwick, V.; Toon, B.

    2017-12-01

    High clouds in the present day Mars atmosphere nucleate on interplanetary dust particles (IDPs) that burn up on entry into the Mars atmosphere. Clouds form when superstaturated water vapor condenses on suspended aerosols. Radiatively active water ice clouds may play a crucial role in warming the early Mars climate. Urata and Toon (2011) simulate a stable warm paleo-climate for Mars if clouds form high in the atmosphere and if particles are sufficiently large (r > 10 μm). The annual fluence of micrometeoroids at Mars was larger early on in the evolution of our solar system. Additionally, the water vapor budget throughout the middle and high atmosphere was likely heightened . Both factors should contribute to enhanced nucleation and growth of water ice cloud particles at high altitudes. Here, we use the MarsCAM-CARMA general circulation model (GCM) to examine the radiative impact of high altitude water ice clouds on the early Mars climate and as a possible solution to the faint young sun problem for Mars.

  19. Dust emission: small-scale processes with global consequences

    USGS Publications Warehouse

    Okin, Gregory S.; Bullard, Joanna E.; Reynolds, Richard L.; Ballantine, John-Andrew C.; Schepanski, Kerstin; Todd, Martin C.; Belnap, Jayne; Baddock, Matthew C.; Gill, Thomas E.; Miller, Mark E.

    2011-01-01

    Desert dust, both modern and ancient, is a critical component of the Earth system. Atmospheric dust has important effects on climate by changing the atmospheric radiation budget, while deposited dust influences biogeochemical cycles in the oceans and on land. Dust deposited on snow and ice decreases its albedo, allowing more light to be trapped at the surface, thus increasing the rate of melt and influencing energy budgets and river discharge. In the human realm, dust contributes to the transport of allergens and pathogens and when inhaled can cause or aggravate respiratory diseases. Dust storms also represent a significant hazard to road and air travel. Because it affects so many Earth processes, dust is studied from a variety of perspectives and at multiple scales, with various disciplines examining emissions for different purposes using disparate strategies. Thus, the range of objectives in studying dust, as well as experimental approaches and results, has not yet been systematically integrated. Key research questions surrounding the production and sources of dust could benefit from improved collaboration among different research communities. These questions involve the origins of dust, factors that influence dust production and emission, and methods through which dust can be monitored.

  20. Infrared Study of Supernova Ejecta and Dust

    NASA Astrophysics Data System (ADS)

    Meikle, W. Peter; Farrah, Duncan; Fesen, Robert; Fransson, Claes; Gerardy, Christopher; Hoeflich, Peter; Kotak, Rubina; Kozma, Cecilia; Lucy, Leon; Lundqvist, Peter; Mattila, Seppo; Pozzo, Monica; Sollerman, Jesper; van Dyk, Schuyler; Wheeler, Craig

    2004-09-01

    We propose to use IRAC and IRS to gain powerful new insights on the nature of supernova (SN) explosions and test the hypothesis that SNe are major sources of cosmic dust. One of our two aims is to carry out robust tests of SN explosion models through the measurement of fine-structure (FS) lines and, where possible, their evolution. The important molecule, SiO, will also be measured. By comparison with our spectral synthesis models, we shall test the explosion model-sensitive predictions of abundances and their distribution. Most of the FS lines arise from ground state transitions and so, in comparison with optical or near-IR spectra, are much less sensitive to temperature and density uncertainties. However, the FS lines are only accessible in the MIR and the most useful abundance measurements can only be achieved at late times when the ejecta are optically thin. Consequently, ground-based MIR observations at the necessary late epochs are difficult if not impossible for nearly all SNe. Observation with the Spitzer Space Telescope is therefore essential. Our second goal is to test the proposal that core-collapse SNe (CCSNe) are, or have been, the major source of dust in the universe. Direct evidence in support of this is still very sparse. Warm dust emits most strongly in the MIR region, and so is the ideal wavelength range for following the condensation of dust within the ejecta or, in the case of Type IIn SNe, in a cool, dense shell formed at the ejecta/progenitor wind interface. Alternatively, such radiation may arise from IR light echo emission from dust in the progenitor wind. Discrimination between condensing dust and pre-existing circumstellar dust can be achieved by measurement of its MIR spectral energy distribution and evolution. Such measurements can also provide dust mass estimates and give clues about the nature of the grain material. To achieve our two goals, we propose to use IRAC and IRS to observe up to 17 SNe at epochs ranging from about 100 days to

  1. Coupling Mars' Dust and Water Cycles: Effects on Dust Lifting Vigor, Spatial Extent and Seasonality

    NASA Technical Reports Server (NTRS)

    Kahre, M. A.; Hollingsworth, J. L.; Haberle, R. M.; Montmessin, F.

    2012-01-01

    The dust cycle is an important component of Mars' current climate system. Airborne dust affects the radiative balance of the atmosphere, thus greatly influencing the thermal and dynamical state of the atmosphere. Dust raising events on Mars occur at spatial scales ranging from meters to planet-wide. Although the occurrence and season of large regional and global dust storms are highly variable from one year to the next, there are many features of the dust cycle that occur year after year. Generally, a low-level dust haze is maintained during northern spring and summer, while elevated levels of atmospheric dust occur during northern autumn and winter. During years without global-scale dust storms, two peaks in total dust loading were observed by MGS/TES: one peak occurred before northern winter solstice at Ls 200-240, and one peak occurred after northern winter solstice at L(sub s) 305-340. These maxima in dust loading are thought to be associated with transient eddy activity in the northern hemisphere, which has been observed to maximize pre- and post-solstice. Interactive dust cycle studies with Mars General Circulation Models (MGCMs) have included the lifting, transport, and sedimentation of radiatively active dust. Although the predicted global dust loadings from these simulations capture some aspects of the observed dust cycle, there are marked differences between the simulated and observed dust cycles. Most notably, the maximum dust loading is robustly predicted by models to occur near northern winter solstice and is due to dust lifting associated with down slope flows on the flanks of the Hellas basin. Thus far, models have had difficulty simulating the observed pre- and post- solstice peaks in dust loading. Interactive dust cycle studies typically have not included the formation of water ice clouds or their radiative effects. Water ice clouds can influence the dust cycle by scavenging dust from atmosphere and by interacting with solar and infrared radiation

  2. Nonlinear properties of small amplitude dust ion acoustic solitary waves

    NASA Astrophysics Data System (ADS)

    Ghosh, Samiran; Sarkar, S.; Khan, Manoranjan; Gupta, M. R.

    2000-09-01

    In this paper some nonlinear characteristics of small amplitude dust ion acoustic solitary wave in three component dusty plasma consisting of electrons, ions, and dust grains have been studied. Simultaneously, the charge fluctuation dynamics of the dust grains under the assumption that the dust charging time scale is much smaller than the dust hydrodynamic time scale has been considered here. The ion dust collision has also been incorporated. It has been seen that a damped Korteweg-de Vries (KdV) equation governs the nonlinear dust ion acoustic wave. The damping arises due to ion dust collision, under the assumption that the ion hydrodynamical time scale is much smaller than that of the ion dust collision. Numerical investigations reveal that the dust ion acoustic wave admits only a positive potential, i.e., compressive soliton.

  3. Dust as a versatile matter for high-temperature plasma diagnostic.

    PubMed

    Wang, Zhehui; Ticos, Catalin M

    2008-10-01

    Dust varies from a few nanometers to a fraction of a millimeter in size. Dust also offers essentially unlimited choices in material composition and structure. The potential of dust for high-temperature plasma diagnostic is largely unfulfilled yet. The principles of dust spectroscopy to measure internal magnetic field, microparticle tracer velocimetry to measure plasma flow, and dust photometry to measure heat flux are described. Two main components of the different dust diagnostics are a dust injector and a dust imaging system. The dust injector delivers a certain number of dust grains into a plasma. The imaging system collects and selectively detects certain photons resulted from dust-plasma interaction. One piece of dust gives the local plasma quantity, a collection of dust grains together reveals either two-dimensional (using only one or two imaging cameras) or three-dimensional (using two or more imaging cameras) structures of the measured quantity. A generic conceptual design suitable for all three types of dust diagnostics is presented.

  4. A 100-3000 GHz model of thermal dust emission observed by Planck, DIRBE and IRAS

    NASA Astrophysics Data System (ADS)

    Meisner, Aaron M.; Finkbeiner, Douglas P.

    2015-01-01

    We apply the Finkbeiner et al. (1999) two-component thermal dust emission model to the Planck HFI maps. This parametrization of the far-infrared dust spectrum as the sum of two modified blackbodies serves as an important alternative to the commonly adopted single modified blackbody (MBB) dust emission model. Analyzing the joint Planck/DIRBE dust spectrum, we show that two-component models provide a better fit to the 100-3000 GHz emission than do single-MBB models, though by a lesser margin than found by Finkbeiner et al. (1999) based on FIRAS and DIRBE. We also derive full-sky 6.1' resolution maps of dust optical depth and temperature by fitting the two-component model to Planck 217-857 GHz along with DIRBE/IRAS 100μm data. Because our two-component model matches the dust spectrum near its peak, accounts for the spectrum's flattening at millimeter wavelengths, and specifies dust temperature at 6.1' FWHM, our model provides reliable, high-resolution thermal dust emission foreground predictions from 100 to 3000 GHz. We find that, in diffuse sky regions, our two-component 100-217 GHz predictions are on average accurate to within 2.2%, while extrapolating the Planck Collaboration (2013) single-MBB model systematically underpredicts emission by 18.8% at 100 GHz, 12.6% at 143 GHz and 7.9% at 217 GHz. We calibrate our two-component optical depth to reddening, and compare with reddening estimates based on stellar spectra. We find the dominant systematic problems in our temperature/reddening maps to be zodiacal light on large angular scales and the cosmic infrared background anistropy on small angular scales. We have recently released maps and associated software utilities for obtaining thermal dust emission and reddening predictions using our Planck-based two-component model.

  5. Decadal-scale progression of Dansgaard-Oeschger warming events - Are warmings at the end of Heinrich-Stadials different from others?

    NASA Astrophysics Data System (ADS)

    Erhardt, T.; Capron, E.; Rasmussen, S.; Schuepbach, S.; Bigler, M.; Fischer, H.

    2017-12-01

    During the last glacial period proxy records throughout the Northern Hemisphere document a succession of rapid millennial-scale warming events, called Dansgaard Oeschger (DO) events. Marine proxy records from the Atlantic also reveal, that some of the warming events where preceded by large ice rafting events, referred to as Heinrich events. Different mechanisms have been proposed, that can produce DO-like warming in model experiments, however the progression and plausible trigger of the events and their possible interplay with the Heinrich events is still unknown. Because of their fast nature, the progression is challenging to reconstruct from paleoclimate data due to the temporal resolution achievable in many archives and cross-dating uncertainties between records. We use new high-resolution multi-proxy records of sea-salt and terrestrial aerosol concentrations over the period 10-60 ka from two Greenland deep ice cores in conjunction with local precipitation and temperature proxy records from one of the cores to investigate the progression of environmental changes at the onset of the individual warming events. The timing differences are then used to explore whether the DO warming events that terminate Heinrich-Stadials progressed differently in comparison to those after Non-Heinrich-Stadials. Our analysis indicates no difference in the progression of the warming terminating Heinrich-Stadials and Non-Heinrich-Stadials. Combining the evidence from all warming events in the period, our analysis shows a consistent lead of the changes in both local precipitation and terrestrial dust aerosol concentrations over the change in sea-salt aerosol concentrations and local temperature by approximately one decade. This implies that both the moisture transport to Greenland and the intensity of the Asian winter monsoon changed before the sea-ice cover in the North Atlantic was reduced, rendering a collapse of the sea-ice cover as a trigger for the DO events unlikely.

  6. Active Lifting During Martian Dust Storm

    NASA Image and Video Library

    2017-03-09

    This false-color scene from the panoramic camera (Pancam) on NASA's Mars Exploration Rover Opportunity documents movement of dust as a regional dust storm approached the rover's location on Feb. 24, 2017, during the 4,653rd Martian day, or sol, of the rover's work on Mars. Key to detecting the movement is that Pancam color images are combinations of different images taken a short time apart through different color filters. Note that along the horizon, the left portion of the image has a bluish band (with label and arrow in Figure 1). The component image admitting blue light was taken about 150 seconds after the component image admitting red light. A layer of dust-carrying wind hadn't reached this location by the earlier exposure, but had by the later one. This Sol 4653 Opportunity view is toward the north from the rover's location on the western rim of Endeavour Crater in the Meridiani Planum region of Mars. http://photojournal.jpl.nasa.gov/catalog/PIA21485

  7. Lunar Dust-Tolerant Electrical Connector

    NASA Technical Reports Server (NTRS)

    Herman, Jason; Sadick, Shazad; Roberts, Dustyn

    2010-01-01

    An electrical connector was developed that is tolerant of the presence of lunar dust. Novel features of the connector include the use of a permeable membrane to act both as a dust barrier and as a wiper to limit the amount of dust that makes its way into the internal chamber of the connector. The development focused on the Constellation lunar extravehicular activity (EVA) spacesuit s portable life support system (PLSS) battery recharge connector; however, continued research is applying this technology to other lunar surface systems such as lunar rover subsystems and cryogenic fluid transfer connections for in-situ resource utilization (ISRU) applications. Lunar dust has been identified as a significant and present challenge in future exploration missions. In addition to posing contamination and health risks for human explorers, the interlocking, angular nature of lunar dust and its broad grain size distribution make it particularly harmful to mechanisms with which it may come into contact. All Apollo lunar missions experienced some degree of equipment failure because of dust, and it appears that dust accumulation on exposed material is unavoidable and difficult to reverse. Both human EVA and ISRU activities are on the mission horizon and are paramount to the establishment of a permanent human base on the Moon. Reusable and dust-tolerant connection mechanisms are a critical component for mission success. The need for dust-tolerant solutions is also seen in utility work and repair, mass transit applications, construction, mining, arctic and marine environments, diving (search and rescue), and various operations in deserts, where dust or sand clogging and coating different mechanisms and connections may render them difficult to operate or entirely inoperable.

  8. Organic Matter in Cosmic Dust

    PubMed Central

    Sandford, Scott A.; Engrand, Cecile; Rotundi, Alessandra

    2018-01-01

    Organics are observed to be a significant component of cosmic dust in nearly all environments were dust is observed. In many cases only remote telescope observations of these materials are obtainable and our knowledge of the nature of these materials is very basic. However, it is possible to obtain actual samples of extraterrestrial dust in the Earth’s stratosphere, in Antarctic ice and snow, in near-Earth orbit, and via spacecraft missions to asteroids and comets. It is clear that cosmic dust contains a diverse population of organic materials that owe their origins to a variety of chemical processes occurring in many different environments. The presence of isotopic enrichments of D and 15N suggests that many of these organic materials have an interstellar/protosolar heritage. The study of these samples is of considerable importance since they are the best preserved materials of the early Solar System available. PMID:29422977

  9. Gusev Dust Devil Movie, Sol 456 (Plain and Isolated)

    NASA Technical Reports Server (NTRS)

    2005-01-01

    This movie clip shows a dust devil scooting across a plain inside Gusev Crater on Mars as seen from the NASA rover Spirit's hillside vantage point during the rover's 456th martian day, or sol (April 15, 2005). The individual images were taken about 20 seconds apart by Spirit's navigation camera. Each frame in this movie has the raw image on the top half and a processed version in the lower half that enhances contrast and removes stationary objects, producing an image that is uniformly gray except for features that change from frame to frame.

    The movie results from a new way of watching for dust devils, which are whirlwinds that hoist dust from the surface into the air. Spirit began seeing dust devils in isolated images in March 2005. At first, the rover team relied on luck. It might catch a dust devil in an image or it might miss by a few minutes. Using the new detection strategy, the rover takes a series of 21 images. Spirit sends a few of them to Earth, as well as little thumbnail images of all of them. Team members use the 3 big images and all the small images to decide whether the additional big images have dust devils. For this movie, they specifically told Spirit to send back frames that they knew had dust devils.

    Scientists expected dust devils since before Spirit landed. The landing area inside Gusev Crater is filled with dark streaks left behind when dust devils pick dust up from an area. It is also filled with bright 'hollows,' which are dust-filled miniature craters. Dust covers most of the terrain. Winds flow into and out of Gusev crater every day. The Sun heats the surface so that the surface is warm to the touch even though the atmosphere at 2 meters (6 feet) above the surface would be chilly. That temperature contrast causes convection. Mixing the dust, winds, and convection should trigger dust devils.

    Scientists will use the images to study several things. Tracking the dust devils tells which way the wind blows at different times

  10. Gusev Dust Devil Movie, Sol 459 (Plain and Isolated)

    NASA Technical Reports Server (NTRS)

    2005-01-01

    This movie clip shows a dust devil scooting across a plain inside Gusev Crater on Mars as seen from the NASA rover Spirit's hillside vantage point during the rover's 459th martian day, or sol (April 18, 2005). The individual images were taken about 20 seconds apart by Spirit's navigation camera. Each frame in this movie has the raw image on the top half and a processed version in the lower half that enhances contrast and removes stationary objects, producing an image that is uniformly gray except for features that change from frame to frame.

    The movie results from a new way of watching for dust devils, which are whirlwinds that hoist dust from the surface into the air. Spirit began seeing dust devils in isolated images in March 2005. At first, the rover team relied on luck. It might catch a dust devil in an image or it might miss by a few minutes. Using the new detection strategy, the rover takes a series of 21 images. Spirit sends a few of them to Earth, as well as little thumbnail images of all of them. Team members use the 3 big images and all the small images to decide whether the additional big images have dust devils. For this movie, they specifically told Spirit to send back frames that they knew had dust devils.

    Scientists expected dust devils since before Spirit landed. The landing area inside Gusev Crater is filled with dark streaks left behind when dust devils pick dust up from an area. It is also filled with bright 'hollows,' which are dust-filled miniature craters. Dust covers most of the terrain. Winds flow into and out of Gusev crater every day. The Sun heats the surface so that the surface is warm to the touch even though the atmosphere at 2 meters (6 feet) above the surface would be chilly. That temperature contrast causes convection. Mixing the dust, winds, and convection should trigger dust devils.

    Scientists will use the images to study several things. Tracking the dust devils tells which way the wind blows at different times

  11. Tracking Intercontinental Dust Transport With Radiogenic Isotopes: Hefei, China to California, Spring 2002

    NASA Astrophysics Data System (ADS)

    Christensen, J. N.; Cliff, S. S.; Vancuren, R. A.; Perry, K. D.; Depaolo, D. J.

    2006-12-01

    Research over the past decade has highlighted the importance of intercontinental transport and exchange of atmospheric aerosols, including soil-derived dust and industrial pollutants. Far-traveled aerosols can affect air quality, atmospheric radiative forcing and cloud formation and can be an important component in soils. Principal component analysis of elemental data for aerosols collected over California has identified a persistent Asian soil dust component that peaks with Asian dust storm events [1]. Isotopic fingerprinting can provide an additional and potentially more discriminating tool for tracing sources of dust. For example, the naturally variable isotopic compositions of Sr and Nd reflect both the geochemistry of the dust source and its pre- weathering geologic history. Sr and Nd isotopic data and chemical data have been collected for a time series of PM2.5 filter samples from Hefei, China taken from eraly April into early May, 2002. This period encompassed a series of dust storms. The sampling time frame overlapped with the 2002 Intercontinental Transport and Chemical Transformation (ITCT-2K2) experiment along the Pacific coast of North America and inland California. Highs in 87Sr/86Sr in the Hefei time series coincide with peaks in Ca and Si representing peaks in mineral particulate loading resulting from passing dust storms. Mixing diagrams combining isotopic data with chemical data identify several components; a high 87Sr/86Sr component that we identify with mineral dust (loess), and two different low 87Sr/86Sr components (local sources and marine aerosol). Using our measured isotopic composition of the "loess" standard CJ-1 [2] as representative of the pure high 87Sr/86Sr component, we calculate 24 hour average loess particulate concentrations in air which range up to 35 micrograms per cubic meter. Marine aerosol was a major component on at least one of the sampled days. The results for the Hefei samples provide a basis for our isotopic study of

  12. Statistical simulations of the dust foreground to cosmic microwave background polarization

    NASA Astrophysics Data System (ADS)

    Vansyngel, F.; Boulanger, F.; Ghosh, T.; Wandelt, B.; Aumont, J.; Bracco, A.; Levrier, F.; Martin, P. G.; Montier, L.

    2017-07-01

    The characterization of the dust polarization foreground to the cosmic microwave background (CMB) is a necessary step toward the detection of the B-mode signal associated with primordial gravitational waves. We present a method to simulate maps of polarized dust emission on the sphere that is similar to the approach used for CMB anisotropies. This method builds on the understanding of Galactic polarization stemming from the analysis of Planck data. It relates the dust polarization sky to the structure of the Galactic magnetic field and its coupling with interstellar matter and turbulence. The Galactic magnetic field is modeled as a superposition of a mean uniform field and a Gaussian random (turbulent) component with a power-law power spectrum of exponent αM. The integration along the line of sight carried out to compute Stokes maps is approximated by a sum over a small number of emitting layers with different realizations of the random component of the magnetic field. The model parameters are constrained to fit the power spectra of dust polarization EE, BB, and TE measured using Planck data. We find that the slopes of the E and B power spectra of dust polarization are matched for αM = -2.5, an exponent close to that measured for total dust intensity but larger than the Kolmogorov exponent - 11/3. The model allows us to compute multiple realizations of the Stokes Q and U maps for different realizations of the random component of the magnetic field, and to quantify the variance of dust polarization spectra for any given sky area outside of the Galactic plane. The simulations reproduce the scaling relation between the dust polarization power and the mean total dust intensity including the observed dispersion around the mean relation. We also propose a method to carry out multifrequency simulations, including the decorrelation measured recently by Planck, using a given covariance matrix of the polarization maps. These simulations are well suited to optimize

  13. Climatology of atmospheric circulation patterns of Arabian dust in western Iran.

    PubMed

    Najafi, Mohammad Saeed; Sarraf, B S; Zarrin, A; Rasouli, A A

    2017-08-28

    Being in vicinity of vast deserts, the west and southwest of Iran are characterized by high levels of dust events, which have adverse consequences on human health, ecosystems, and environment. Using ground based dataset of dust events in western Iran and NCEP/NCAR reanalysis data, the atmospheric circulation patterns of dust events in the Arabian region and west of Iran are identified. The atmospheric circulation patterns which lead to dust events in the Arabian region and western Iran were classified into two main categories: the Shamal dust events that occurs in warm period of year and the frontal dust events as cold period pattern. In frontal dust events, the western trough or blocking pattern at mid-level leads to frontogenesis, instability, and air uplift at lower levels of troposphere in the southwest of Asia. Non-frontal is other pattern of dust event in the cold period and dust generation are due to the regional circulation systems at the lower level of troposphere. In Shamal wind pattern, the Saudi Arabian anticyclone, Turkmenistan anticyclone, and Zagros thermal low play the key roles in formation of this pattern. Summer and transitional patterns are two sub-categories of summer Shamal wind pattern. In summer trough pattern, the mid-tropospheric trough leads to intensify the surface thermal systems in the Middle East and causes instability and rising of wind speed in the region. In synthetic pattern of Shamal wind and summer trough, dust is created by the impact of a trough in mid-levels of troposphere as well as existing the mentioned regional systems which are contributed in formation of summer Shamal wind pattern.

  14. Dust grains from the heart of supernovae

    NASA Astrophysics Data System (ADS)

    Bocchio, M.; Marassi, S.; Schneider, R.; Bianchi, S.; Limongi, M.; Chieffi, A.

    2016-03-01

    Dust grains are classically thought to form in the winds of asymptotic giant branch (AGB) stars. However, there is increasing evidence today for dust formation in supernovae (SNe). To establish the relative importance of these two classes of stellar sources of dust, it is important to know the fraction of freshly formed dust in SN ejecta that is able to survive the passage of the reverse shock and be injected in the interstellar medium. With this aim, we have developed a new code, GRASH_Rev, that allows following the dynamics of dust grains in the shocked SN ejecta and computing the time evolution of the mass, composition, and size distribution of the grains. We considered four well-studied SNe in the Milky Way and Large Magellanic Cloud: SN 1987A, CasA, the Crab nebula, and N49. These sources have been observed with both Spitzer and Herschel, and the multiwavelength data allow a better assessment the mass of warm and cold dust associated with the ejecta. For each SN, we first identified the best explosion model, using the mass and metallicity of the progenitor star, the mass of 56Ni, the explosion energy, and the circumstellar medium density inferred from the data. We then ran a recently developed dust formation model to compute the properties of freshly formed dust. Starting from these input models, GRASH_Rev self-consistently follows the dynamics of the grains, considering the effects of the forward and reverse shock, and allows predicting the time evolution of the dust mass, composition, and size distribution in the shocked and unshocked regions of the ejecta. All the simulated models aagree well with observations. Our study suggests that SN 1987A is too young for the reverse shock to have affected the dust mass. Hence the observed dust mass of 0.7-0.9 M⊙ in this source can be safely considered as indicative of the mass of freshly formed dust in SN ejecta. Conversely, in the other three SNe, the reverse shock has already destroyed between 10-40% of the

  15. The Effect of Asian Dust Aerosols on Cloud Properties and Radiative Forcing from MODIS and CERES

    NASA Technical Reports Server (NTRS)

    Huang, Jianping; Minnis, Patrick; Lin, Bing; Wang, Tianhe; Yi, Yuhong; Hu, Yongxiang; Sun-Mack, Sunny; Ayers, Kirk

    2005-01-01

    The effects of dust storms on cloud properties and radiative forcing are analyzed over northwestern China from April 2001 to June 2004 using data collected by the Moderate Resolution Imaging Spectroradiometer (MODIS) and Clouds and the Earth's Radiant Energy System (CERES) instruments on the Aqua and Terra satellites. On average, ice cloud effective particle diameter, optical depth and ice water path of the cirrus clouds under dust polluted conditions are 11%, 32.8%, and 42% less, respectively, than those derived from ice clouds in dust-free atmospheric environments. The humidity differences are larger in the dusty region than in the dust-free region, and may be caused by removal of moisture by wet dust precipitation. Due to changes in cloud microphysics, the instantaneous net radiative forcing is reduced from -71.2 W/m2 for dust contaminated clouds to -182.7 W/m2 for dust-free clouds. The reduced cooling effects of dusts may lead to a net warming of 1 W/m2, which, if confirmed, would be the strongest aerosol forcing during later winter and early spring dust storm seasons over the studied region.

  16. The effects of dust on Colorado mountain snow cover albedo and compositional links to dust-source areas

    NASA Astrophysics Data System (ADS)

    Goldstein, H. L.; Reynolds, R. L.; Landry, C.; Derry, J. E.; Kokaly, R. F.; Breit, G. N.

    2016-12-01

    Dust deposited on mountain snow cover (DOS) changes snow albedo, enhances absorption of solar radiation, and effectively increases rates of snow melt, leading to earlier-than-normal runoff and overall smaller late-season water supplies for tens of millions of people and industries in the American West. Visible-spectrum reflectance of DOS samples is on the order of 0.2 (80% absorption), in stark contrast to the high reflectivity of pure snow which approaches 1.0. Samples of DOS were collected from 12 high-elevation Colorado mountain sites near the end of spring from 2013 through 2016 prior to complete snow melt, when most dust layers had merged into one layer. These samples were analyzed to measure dust properties that affect snow albedo and to link DOS to dust-source areas. Dust mass loadings to snow during water year 2014 varied from 5 to 30 g/m2. Median particle sizes centered around 20 micrometers with more than 80% of the dust <63 micrometers. Dark minerals, carbonaceous matter, and iron oxides, including nano-sized hematite and goethite, together diminished reflectance according to their variable concentrations. Documenting variations in dust-particle masses, sizes, and compositions helps determine their influences on snow-melt and may be useful for modeling snow-melt effects from future dust. Furthermore, variations in dust components and particle sizes lead to new ways to recognize sources of dust by comparison with properties of fine-grained sediments in dust-source areas. Much of the DOS in the San Juan Mountains, Colorado can be linked to southern Colorado Plateau source areas by compositional similarities and satellite imagery. Understanding dust properties that affect snow albedo and recognizing the sources of dust deposited on snow cover may guide mitigation of dust emission that affects water resources of the Colorado River basin.

  17. Lidar network observation of dust layer evolution over the Gobi Desert in MAY 2013

    NASA Astrophysics Data System (ADS)

    Kawai, Kei; Kai, Kenji; Jin, Yoshitaka; Sugimoto, Nobuo; Batdorj, Dashdondog

    2018-04-01

    A lidar network captured the evolution of a dust layer in the Gobi Desert on 22-23 May 2013. The lidar network consists of a ceilometer and two AD-Net lidars in Mongolia. The dust layer was generated by a strong wind due to a cold front and elevated over the surface of the cold front by an updraft of the warm air in the cold-front system. It was evolving from the atmospheric boundary layer to the free troposphere while moving 600 km through the desert with the cold front.

  18. Influence of the Latitudinal Temperature Gradient on Soil Dust Concentration and Deposition in Greenland

    NASA Technical Reports Server (NTRS)

    Tegen, Ina; Rind, David

    2000-01-01

    To investigate the effects of changes in the latitudinal temperature gradient and the global mean temperature on dust concentration in the Northern Hemisphere, experiments with the Goddard Institute for Space Studies General Circulation Model (GISS GCM) are performed. The dust concentration over Greenland is calculated from sources in central and eastern Asia, which are integrated on-line in the model. The results show that an increase in the latitudinal temperature gradient increases both the Asian dust source strength and the concentration over Greenland. The source increase is the result of increased surface winds, and to a minor extent, the increase in Greenland dust is also associated with increased northward transport. Cooling the climate in addition to this increased gradient leads to a decrease in precipitation scavenging, which helps produce a further (slight) increase in Greenland dust in this experiment. Reducing the latitudinal gradient reduces the surface wind and hence the dust source, with a subsequent reduction in Greenland dust concentrations. Warming the climate in addition to this reduced gradient leads to a further reduction in Greenland dust due to enhanced precipitation scavenging. These results can be used to evaluate the relationship of Greenland ice core temperature changes to changes in the latitudinal and global temperatures.

  19. Interannual variability of global dust storms on Mars.

    PubMed

    Haberle, R M

    1986-10-24

    Global dust storms on Mars occur in some years but not in others. If the four Mars years of Viking data are representative, some distinguishing characteristics can be inferred. In years with global dust storms, dust is raised in the southern hemisphere and spread over much of the planet by an intensified Hadley circulation. In years without global dust storms, dust is raised in the northern hemisphere by relatively active mid-latitude storm systems but does not spread globally. In both cases the dusty season is winter in the north. Assuming that the cross-equatorial Hadley circulation plays a key role in the onset of global dust storms, it is shown from numerical simulations that a northen hemisphere dust haze weakens its intensity and, hence, its contribution to the surface stress in the southern hemisphere. This, in turn, reduces the possibility of global dust storm development. The interannual variability is therefore the result either of a competition between circulations in opposite hemispheres, in which case the variability has a random component, or it is the result of the cycling of dust between hemispheres, in which case the variability is related to the characteristics of global dust storms themselves.

  20. Positive low cloud and dust feedbacks amplify tropical North Atlantic Multidecadal Oscillation

    DOE PAGES

    Yuan, Tianle; Oreopoulos, Lazaros; Zelinka, Mark; ...

    2016-02-04

    The Atlantic Multidecadal Oscillation (AMO) is characterized by a horseshoe pattern of sea surface temperature (SST) anomalies and has a wide range of climatic impacts. While the tropical arm of AMO is responsible for many of these impacts, it is either too weak or completely absent in many climate model simulations. Here we show, using both observational and model evidence, that the radiative effect of positive low cloud and dust feedbacks is strong enough to generate the tropical arm of AMO, with the low cloud feedback more dominant. The feedbacks can be understood in a consistent dynamical framework: weakened tropicalmore » trade wind speed in response to a warm middle latitude SST anomaly reduces dust loading and low cloud fraction over the tropical Atlantic, which warms the tropical North Atlantic SST. Together they contribute to the appearance of the tropical arm of AMO. Most current climate models miss both the critical wind speed response and two positive feedbacks though realistic simulations of them may be essential for many climatic studies related to the AMO.« less

  1. Positive Low Cloud and Dust Feedbacks Amplify Tropical North Atlantic Multidecadal Variability

    NASA Technical Reports Server (NTRS)

    Yuan, Tianle; Oraiopoulos, Lazaros; Zelinka, Mark; Yu, Hongbin; Norris, Joel R.; Chin, Mian; Platnick, Steven; Meyer, Kerry

    2016-01-01

    The Atlantic Multidecadal Oscillation (AMO) is characterized by a horseshoe pattern of sea surface temperature (SST) anomalies and has a wide range of climatic impacts. While the tropical arm of AMO is responsible for many of these impacts, it is either too weak or completely absent in many climate model simulations. Here we show, using both observational and model evidence, that the radiative effect of positive low cloud and dust feedbacks is strong enough to generate the tropical arm of AMO, with the low cloud feedback more dominant. The feedbacks can be understood in a consistent dynamical framework: weakened tropical trade wind speed in response to a warm middle latitude SST anomaly reduces dust loading and low cloud fraction over the tropical Atlantic, which warms the tropical North Atlantic SST. Together they contribute to appearance of the tropical arm of AMO. Most current climate models miss both the critical wind speed response and two positive feedbacks though realistic simulations of them may be essential for many climatic studies related to the AMO.

  2. The potential influence of Asian and African mineral dust on ice, mixed-phase and liquid water clouds

    NASA Astrophysics Data System (ADS)

    Wiacek, A.; Peter, T.; Lohmann, U.

    2010-02-01

    This modelling study explores the availability of mineral dust particles as ice nuclei for interactions with ice, mixed-phase and liquid water clouds, also tracking the particles' history of cloud-processing. We performed 61 320 one-week forward trajectory calculations originating near the surface of major dust emitting regions in Africa and Asia using high-resolution meteorological analysis fields for the year 2007. Without explicitly modelling dust emission and deposition processes, dust-bearing trajectories were assumed to be those coinciding with known dust emission seasons. We found that dust emissions from Asian deserts lead to a higher potential for interactions with high clouds, despite being the climatologically much smaller dust emission source. This is due to Asian regions experiencing significantly more ascent than African regions, with strongest ascent in the Asian Taklimakan desert at ~25%, ~40% and 10% of trajectories ascending to 300 hPa in spring, summer and fall, respectively. The specific humidity at each trajectory's starting point was transported in a Lagrangian manner and relative humidities with respect to water and ice were calculated in 6-h steps downstream, allowing us to estimate the formation of liquid, mixed-phase and ice clouds. Practically none of the simulated air parcels reached regions where homogeneous ice nucleation can take place (T≲-40 °C) along trajectories that have not experienced water saturation first. By far the largest fraction of cloud forming trajectories entered conditions of mixed-phase clouds, where mineral dust will potentially exert the biggest influence. The majority of trajectories also passed through regions supersaturated with respect to ice but subsaturated with respect to water, where "warm" (T≳-40 °C) ice clouds may form prior to supercooled water or mixed-phase clouds. The importance of "warm" ice clouds and the general influence of dust in the mixed-phase cloud region are highly uncertain due to

  3. A Northward Shift of the North Atlantic Ocean Intertropical Convergence Zone in Response to Summertime Saharan Dust Outbreaks

    NASA Technical Reports Server (NTRS)

    Wilcox, Eric M.; Lau, K. M.; Kim, Kyu-Myong

    2010-01-01

    The influence on the summertime North Atlantic Ocean inter-tropical convergence zone (ITCZ) of Saharan dust outbreaks is explored using nine years of continuous satellite observations and atmospheric reanalysis products. During dust outbreak events rainfall along the ITCZ shifts northward by 1 to 4 degrees latitude. Dust outbreaks coincide with warmer lower-tropospheric temperatures compared to low dust conditions, which is attributable to advection of the warm Saharan Air Layer, enhanced subtropical subsidence, and radiative heating of dust. The enhanced positive meridional temperature gradient coincident with dust outbreaks is accompanied by an acceleration of the easterly winds on the n011h side of the African Easterly Jet (AEJ). The center of the positive vorticity region south of the AEJ moves north drawing the center of low-level convergence and ITCZ rainfall northward with it. The enhanced precipitation on the north side of the ITCZ occurs in spite of widespread sea surface temperature cooling north of the ITCZ owing to reduced surface solar insolation by dust scattering.

  4. Photochemical oxidant processes in the presence of dust: An evaluation of the impact of dust on particulate nitrate and ozone formation

    NASA Technical Reports Server (NTRS)

    Zhang, Yang; Sunwoo, Young; Kotamarthi, Veerabhadra; Carmichael, Gregory R.

    1994-01-01

    The influence of dust on the tropospheric photochemical oxidant cycle is studied through the use of a detailed coupled aerosol and gas-phase chemistry model. Dust is a significant component of the troposphere throughout Asia and provides a surface for a variety of heterogeneous reactions. Dust is found to be an important surface for particulate nitrate formation. For dust loading and ambient concentrations representative of conditions in East Asia, particulate nitrate levels of 1.5-11.5 micrograms/cubic meter are predicted, consistent with measured levels in this region. Dust is also found to reduce NO(x) levels by up to 50%, HO2 concentrations by 20%-80%, and ozone production rates by up to 25%. The magnitude of the influence of dust is sensitive to mass concentration of the aerosol, relative humidity, and the value of the accommodation coefficient.

  5. Preliminary measurements of kinetic dust temperature using stereoscopic particle image velocimetry

    NASA Astrophysics Data System (ADS)

    Williams, Jeremiah; Thomas, Edward

    2004-11-01

    A dusty (or complex) plasma is a four-component system composed of ions, electrons, neutral particles and charged microparticles. The presence of the microparticle (i.e., dust) component alters the plasma environment, giving rise to a wide variety of new plasma phenomena. Recently, the Auburn Plasma Sciences Laboratory (PSL) has acquired and installed a stereoscopic PIV (stereo-PIV) diagnostic tool for dusty plasma investigations [Thomas, et. al., Phys. Plasmas, 11, L37 (2004)]. This presentation discusses the use of the stereo-PIV technique for determining the velocity space distribution function of the microparticle component of a dc glow discharge dusty plasma. These distribution functions are then used to make preliminary estimates of the kinetic temperature of the dust component. The data is compared to a simple energy balance model that relates the dust temperature to the electric field and neutral pressure.

  6. Asteroid Belts in Debris Disk Twins: Vega and Fomalhaut

    NASA Technical Reports Server (NTRS)

    Su, Kate Y. L.; Rieke, George H.; Malhortra, Renu; Stapelfeldt, Karl R.; Hughes, A. Meredith; Bonsor, Amy; Wilner, David J.; Balog, Zoltan; Watson, Dan M.; Werner, Michael W.; hide

    2013-01-01

    Vega and Fomalhaut are similar in terms of mass, ages, and global debris disk properties; therefore, they are often referred to as debris disk twins. We present Spitzer 10-35 micrometers spectroscopic data centered at both stars and identify warm, unresolved excess emission in the close vicinity of Vega for the first time. The properties of the warm excess in Vega are further characterized with ancillary photometry in the mid-infrared and resolved images in the far-infrared and submillimeter wavelengths. The Vega warm excess shares many similar properties with the one found around Fomalhaut. The emission shortward of approximately 30 micrometers from both warm components is well described as a blackbody emission of approximately 170 K. Interestingly, two other systems, Eri and HR 8799, also show such an unresolved warm dust using the same approach. These warm components may be analogous to the solar system s zodiacal dust cloud, but of far greater mass (fractional luminosity of approximately 10(exp-5) to 10(exp-6) compared to 10(exp-8) to 10(exp-7). The dust temperature and tentative detections in the submillimeter suggest that the warm excess arises from dust associated with a planetesimal ring located near the water-frost line and presumably created by processes occurring at similar locations in other debris systems as well. We also review the properties of the 2 micrometers hot excess around Vega and Fomalhaut, showing that the dust responsible for the hot excess is not spatially associated with the dust we detected in the warm belt.We suggest it may arise from hot nano grains trapped in the magnetic field of the star. Finally, the separation between the warm and cold belt is rather large with an orbital ratio greater than or approximately 10 in all four systems. In light of the current upper limits on the masses of planetary objects and the large gap, we discuss the possible implications for their underlying planetary architecture and suggest that multiple, low

  7. Detection of Dermatophagoides farinae in the dust of air conditioning filters.

    PubMed

    Liu, Zhigang; Bai, Yu; Ji, Kunmei; Liu, Xiaoyu; Cai, Chengyu; Yu, Haiqiong; Li, Meng; Bao, Ying; Lian, Yuyin; Gao, Bo

    2007-01-01

    The allergenic dust mite species Dermatophagoides pteronyssinus and Dermatophagoides farinae generally inhabit warm moist environments. This study tested the hypothesis that these allergenic species may thrive in air conditioner filters. A year-long investigation of the dust mite population densities and species identities living in air conditioner filters in Shenzhen City in Southern China was performed. Additional data describing the levels of major dust mite allergen proteins from samples collected in July and August 2004 were analyzed. Genetic polymorphism analysis of Der f 1 and Der f 2 genes in the collected animals was also conducted. Our investigation revealed that larval dust mites started to grow in March, from which time their populations proceeded to steadily increase until reaching their population zenith in July and August. The dust mite populations decreased sharply in October and live dust mites were no longer observed in the winter. Among the mites collected in July and August, 30.1 and 25.8% were of the species D. farinae. The concentration of Der f 1 was 3.04 +/- 1.75 and 3.21 +/- 1.84 microg/g dust in July and August, respectively, and that of Der f 2 was 2.15 +/- 0.82 and 2.04 +/- 1.15 microg/g dust. Four types of Der f 1 and 5 types of Der f 2 cDNA sequences were cloned from collected Der f mites. Their sequences were highly homologous with those previously published in GenBank (No. AB034946.1 and No. AB195580.1). This research demonstrated that Der f allergens exist in the dust of air conditioner filters in this area.

  8. "Kicking Up Some Dust": An Experimental Investigation Relating Lunar Dust Erosive Wear to Solar Power Loss

    NASA Technical Reports Server (NTRS)

    Mpagazehe, Jeremiah N.; Street, Kenneth W., Jr.; Delgado, Irebert R.; Higgs, C. Fred, III

    2013-01-01

    The exhaust from retrograde rockets fired by spacecraft landing on the Moon can accelerate lunar dust particles to high velocities. Information obtained from NASA's Apollo 12 mission confirmed that these high-speed dust particles can erode nearby structures. This erosive wear damage can affect the performance of optical components such as solar concentrators. Solar concentrators are objects which collect sunlight over large areas and focus the light into smaller areas for purposes such as heating and energy production. In this work, laboratory-scale solar concentrators were constructed and subjected to erosive wear by the JSC-1AF lunar dust simulant. The concentrators were focused on a photovoltaic cell and the degradation in electrical power due to the erosive wear was measured. It was observed that even moderate exposure to erosive wear from lunar dust simulant resulted in a 40 percent reduction in power production from the solar concentrators.

  9. Testing the sensitivity of past climates to the indirect effects of dust

    NASA Astrophysics Data System (ADS)

    Sagoo, Navjit; Storelvmo, Trude

    2017-06-01

    Mineral dust particles are important ice nuclei (IN) and as such indirectly impact Earth's radiative balance via the properties of cold clouds. Using the Community Earth System Model version 1.0.6, and Community Atmosphere Model version 5.1, and a new empirical parameterization for ice nucleation on dust particles, we investigate the radiative forcing induced by dust IN for different dust loadings. Dust emissions are representative of global conditions for the Last Glacial Maximum and the mid-Pliocene Warm Period. Increased dust leads to smaller and more numerous ice crystals in mixed phase clouds, impacting cloud opacity, lifetime, and precipitation. This increases the shortwave cloud radiative forcing, resulting in significant surface temperature cooling and polar amplification—which is underestimated in existing studies relative to paleoclimate archives. Large hydrological changes occur and are linked to an enhanced dynamical response. We conclude that dust indirect effects could potentially have a significant impact on the model-data mismatch that exists for paleoclimates.Plain Language SummaryMineral <span class="hlt">dust</span> and climate are closely linked, with large fluctuations in <span class="hlt">dust</span> deposition recorded in geological archives. Dusty conditions are generally associated with cold, glacial periods and low <span class="hlt">dust</span> with warmer climates. The direct effects of <span class="hlt">dust</span> on the climate (absorbing and reflecting radiation) are well understood; however, the indirect effects of <span class="hlt">dust</span> on climate have been overlooked. <span class="hlt">Dust</span> indirectly impacts the climate through its role as ice nuclei; the presence of <span class="hlt">dust</span> makes it easier for ice to form in a cloud. We explore the indirect effects of <span class="hlt">dust</span> in climates with different <span class="hlt">dust</span> loading from the present by conducting a climate modeling study in which <span class="hlt">dust</span> are able to act as ice nuclei. Including <span class="hlt">dust</span> indirect effects increases the sensitivity of our model to changes in <span class="hlt">dust</span> emission. Increasing <span class="hlt">dust</span> impacts ice</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/21251230-nonlinear-dust-lattice-waves-modified-toda-lattice','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/21251230-nonlinear-dust-lattice-waves-modified-toda-lattice"><span>Nonlinear <span class="hlt">dust</span>-lattice waves: a modified Toda lattice</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Cramer, N. F.</p> <p></p> <p>Charged <span class="hlt">dust</span> grains in a plasma interact with a Coulomb potential, but also with an exponential <span class="hlt">component</span> to the potential, due to Debye shielding in the background plasma. Here we investigate large-amplitude oscillations and waves in <span class="hlt">dust</span>-lattices, employing techniques used in Toda lattice analysis. The lattice consists of a linear chain of particles, or a periodic ring as occurs in experimentally observed <span class="hlt">dust</span> particle clusters. The particle motion has a triangular waveform, and chaotic motion for large amplitude motion of a grain.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AtmEn.160..142P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AtmEn.160..142P"><span>Heating rate profiles and radiative forcing due to a <span class="hlt">dust</span> storm in the Western Mediterranean using satellite observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Peris-Ferrús, C.; Gómez-Amo, J. L.; Marcos, C.; Freile-Aranda, M. D.; Utrillas, M. P.; Martínez-Lozano, J. A.</p> <p>2017-07-01</p> <p>We analyze the vertically-resolved radiative impact due to a <span class="hlt">dust</span> storm in the Western Mediterranean. The <span class="hlt">dust</span> plume travels around 3-5 km altitude and the aerosol optical depth derived by MODIS at 550 nm ranges from 0.33 to 0.52 at the overpass time (13:05 UT). The aerosol radiative forcing (ARF), forcing efficiency (FE) and heating rate profile (AHR) are determined throughout the <span class="hlt">dust</span> trajectory in shortwave (SW) and longwave (LW) ranges. To do this, we integrate different satellite observations (CALIPSO and MODIS) and detailed radiative transfer modeling. The combined (SW + LW) effect of the <span class="hlt">dust</span> event induces a net cooling in the studied region. On average, the FE at 22.4° solar zenith angle is -190.3 W m-2 and -38.1 W m-2, at surface and TOA, respectively. The corresponding LW/SW offset is 14% and 38% at surface and TOA, respectively. Our results at TOA are sensitive to the surface albedo in the SW and surface temperature in the LW. The absolute value of FE decrease (increase) in the SW (LW) with the surface albedo, resulting in an increasing LW/SW offset, up to 76%. The AHR profiles show a net <span class="hlt">warming</span> within the <span class="hlt">dust</span> layer, with a maximum value of 3.3 Kd-1. The ARF, FE and AHR are also highly sensitive to the <span class="hlt">dust</span> optical properties in SW and LW. We evaluate this sensitivity by comparing the results obtained using two set of <span class="hlt">dust</span> properties as input in our simulations: a) the prescribed <span class="hlt">dust</span> model by Optical Properties of Aerosols and Clouds (OPAC) and; b) the <span class="hlt">dust</span> optical properties derived from measurements of the size distribution and refractive index. Experimentally derived <span class="hlt">dust</span> properties present larger SSA and asymmetry parameter in the SW than OPAC <span class="hlt">dust</span>. Conversely, OPAC <span class="hlt">dust</span> presents higher AOD in the LW range. These parameters drive the FE and AHR sensitivities in the SW and LW ranges, respectively. Therefore, when measured <span class="hlt">dust</span> properties are used in our simulations: the ARF in the LW substantially reduces at surface and TOA (up to 57%); the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AeoRe...9..153E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AeoRe...9..153E"><span>Assessing sources of airborne mineral <span class="hlt">dust</span> and other aerosols, in Iraq</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Engelbrecht, Johann P.; Jayanty, R. K. M.</p> <p>2013-06-01</p> <p>Most airborne particulate matter in Iraq comes from mineral <span class="hlt">dust</span> sources. This paper describes the statistics and modeling of chemical results, specifically those from Teflon® filter samples collected at Tikrit, Balad, Taji, Baghdad, Tallil and Al Asad, in Iraq, in 2006/2007. Methodologies applied to the analytical results include calculation of correlation coefficients, Principal <span class="hlt">Components</span> Analysis (PCA), and Positive Matrix Factorization (PMF) modeling. PCA provided a measure of the covariance within the data set, thereby identifying likely point sources and events. These include airborne mineral <span class="hlt">dusts</span> of silicate and carbonate minerals, gypsum and salts, as well as anthropogenic sources of metallic fumes, possibly from battery smelting operations, and emissions of leaded gasoline vehicles. Five individual PMF factors (source categories) were modeled, four of which being assigned to <span class="hlt">components</span> of geological <span class="hlt">dust</span>, and the fifth to gasoline vehicle emissions together with battery smelting operations. The four modeled geological <span class="hlt">components</span>, <span class="hlt">dust</span>-siliceous, <span class="hlt">dust</span>-calcic, <span class="hlt">dust</span>-gypsum, and evaporate occur in variable ratios for each site and size fraction (TSP, PM10, and PM2.5), and also vary by season. In general, Tikrit and Taji have the largest and Al Asad the smallest percentages of siliceous <span class="hlt">dust</span>. In contrast, Al Asad has the largest proportion of gypsum, in part representing the gypsiferous soils in that region. Baghdad has the highest proportions of evaporite in both size fractions, ascribed to the highly salinized agricultural soils, following millennia of irrigation along the Tigris River valley. Although <span class="hlt">dust</span> storms along the Tigris and Euphrates River valleys originate from distal sources, the mineralogy bears signatures of local soils and air pollutants.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMAE31B0438Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMAE31B0438Y"><span>An electrified <span class="hlt">dust</span> storm over the Negev desert, Israel</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yair, Y.; Price, C. G.; Yaniv, R.; Katz, S.</p> <p>2015-12-01</p> <p>We report on atmospheric electrical measurements conducted at the Wise Observatory in Mitzpe-Ramon, Israel (30035'N, 34045'E) during a massive <span class="hlt">dust</span> storm that occurred over the Eastern Mediterranean region on 10-11 February 2015. The event transported Saharan <span class="hlt">dust</span> from Egypt and the Sinai Peninsula in advance of the <span class="hlt">warm</span> front of a Cyprus low pressure system. Satellite images show the <span class="hlt">dust</span> plume covering the Negev desert and Southern Israel and moving north. The concentrations of PM10 particles measured by the air-quality monitoring network of the Israeli Ministry of the Environment in Beer-Sheba reached values > 450 μg m-3 and AOT from the AERONET station in Sde-Boker was 1.5 on the 10th. The gradual intensification of the event reached peak values on February 11th of over 1200 μg m-3 and AOT of 1.8. This was the most severe <span class="hlt">dust</span> event in a decade. Continuous measurements of the fair weather vertical electric field (Ez) and vertical current density (Jz) were conducted with 1 minute temporal resolution. Meteorological data was also recorded at the site. As the <span class="hlt">dust</span> was advected over the observation site, we noted very large fluctuations in the electrical parameters. Since the onset of the <span class="hlt">dust</span> storm, the Ez values changed between +1000 and +8000 V m-1 while the Jz fluctuated between -10 pA m2 and +20 pA m2, both on time-scales of a few minutes. These values are a significant departures from the mean fair-weather values measured at the site, which are -~200 V m-1 and ~2 pA m2. The disturbed episodes lasted for several hours on the 10th and 11th and coincided with local meteorological conditions related to the wind direction, which carried large amounts of <span class="hlt">dust</span> particles. We interpret the rapid changes as caused by the transport of electrically charged <span class="hlt">dust</span>. Calculation of the total electrical charge during the <span class="hlt">dust</span> storm will be presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMPP21C1281K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMPP21C1281K"><span>Characterization of <span class="hlt">Dust</span> Emissions from an Actively Retreating Glacier</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>King, J.</p> <p>2017-12-01</p> <p>The Kaskawulsh glacier in Yukon, Canada, part of the St. Elias Mountain Glacier system, is experiencing increased ablation from rising air temperatures and in 2016 changed its main fluvial outlet (the Slims River and Kluane Lake) for the first time in over 300 years to drain into the Gulf of Alaska. In the recent earth history, changes in temperature within glaciated valleys have produced large amounts of wind-blown <span class="hlt">dust</span>, evident in layers of loess within surrounding soils. Mineral aerosols in the atmosphere affect the environment of the earth through their direct effect on solar radiation, modifying cloud processes, and ground insolation, while the deposition of mineral aerosols can provide essential nutrients for ocean and terrestrial productivity. This potential drastic reduction in fluvial inputs into Kluane Lake will result in the rapid exposure of deltaic sediments and extended periods of <span class="hlt">dust</span> emissions, similar to those suggested to occur during the rapid <span class="hlt">warming</span> in the early Holocene. This drastic change already starting to occur makes this system an excellent natural laboratory for investigating the impact of <span class="hlt">dust</span> storms under past and future climates. This research is focused on analyzing the connections between proglacial valley <span class="hlt">dust</span> emissions and glacier dynamics, within ancient and modern climates. Measurements made directly in the valley of <span class="hlt">dust</span> emission frequency, local climatological data analysis, and a remote sensing analysis approach in 2016 and 2017, have been combined to provide an insight into the effects that rapid changes in proglacial systems can have on <span class="hlt">dust</span> dynamics. Strong interdependencies exist between glacier mass and diurnal winds, as well as air temperature and river levels, that combine to control the magnitude and frequency of <span class="hlt">dust</span> emissions. The methodology utilized in this study could be applied to similar regions to produce estimates of <span class="hlt">dust</span> emissions where direct measurements are minimal or difficult to attain, and can be fed</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015A%26A...580A..68K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015A%26A...580A..68K"><span>Temperatures of <span class="hlt">dust</span> and gas in S 140</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Koumpia, E.; Harvey, P. M.; Ossenkopf, V.; van der Tak, F. F. S.; Mookerjea, B.; Fuente, A.; Kramer, C.</p> <p>2015-08-01</p> <p>Context. In dense parts of interstellar clouds (≥105 cm-3), <span class="hlt">dust</span> and gas are expected to be in thermal equilibrium, being coupled via collisions. However, previous studies have shown that in the presence of intense radiation fields, the temperatures of the <span class="hlt">dust</span> and gas may remain decoupled even at higher densities. Aims: The objective of this work is to study in detail the temperatures of <span class="hlt">dust</span> and gas in the photon-dominated region S 140, especially around the deeply embedded infrared sources IRS 1-3 and at the ionization front. Methods: We derive the <span class="hlt">dust</span> temperature and column density by combining Herschel-PACS continuum observations with SOFIA observations at 37 μm and SCUBA data at 450 μm. We model these observations using simple greybody fits and the DUSTY radiative transfer code. For the gas analysis we use RADEX to model the CO 1-0, CO 2-1, 13CO 1-0 and C18O 1-0 emission lines mapped with the IRAM-30 m telescope over a 4' field. Around IRS 1-3, we use HIFI observations of single-points and cuts in CO 9-8, 13CO 10-9 and C18O 9-8 to constrain the amount of <span class="hlt">warm</span> gas, using the best fitting <span class="hlt">dust</span> model derived with DUSTY as input to the non-local radiative transfer model RATRAN. The velocity information in the lines allows us to separate the quiescent <span class="hlt">component</span> from outflows when deriving the gas temperature and column density. Results: We find that the gas temperature around the infrared sources varies between ~35 and ~55 K. In contrast to expectation, the gas is systematically warmer than the <span class="hlt">dust</span> by ~5-15 K despite the high gas density. In addition we observe an increase of the gas temperature from 30-35 K in the surrounding up to 40-45 K towards the ionization front, most likely due to the UV radiation from the external star. Furthermore, detailed models of the temperature structure close to IRS 1 which take the known density gradient into account show that the gas is warmer and/or denser than what we model. Finally, modelling of the <span class="hlt">dust</span> emission from</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.C24A..08P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.C24A..08P"><span>Global mountain snow and ice loss driven by <span class="hlt">dust</span> and black carbon radiative forcing</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Painter, T. H.</p> <p>2014-12-01</p> <p>Changes in mountain snow and glaciers have been our strongest indicators of the effects of changing climate. Earlier melt of snow and losses of glacier mass have perturbed regional water cycling, regional climate, and ecosystem dynamics, and contributed strongly to sea level rise. Recent studies however have revealed that in some regions, the reduction of albedo by light absorbing impurities in snow and ice such as <span class="hlt">dust</span> and black carbon can be distinctly more powerful than regional <span class="hlt">warming</span> at melting snow and ice. In the Rocky Mountains, <span class="hlt">dust</span> deposition has increased 5 to 7 fold in the last 150 years, leading to ~3 weeks earlier loss of snow cover from forced melt. In absolute terms, in some years <span class="hlt">dust</span> radiative forcing there can shorten snow cover duration by nearly two months. Remote sensing retrievals are beginning to reveal powerful <span class="hlt">dust</span> and black carbon radiative forcing in the Hindu Kush through Himalaya. In light of recent ice cores that show pronounced increases in loading of <span class="hlt">dust</span> and BC during the Anthropocene, these forcings may have contributed far more to glacier retreat than previously thought. For example, we have shown that the paradoxical end of the Little Ice Age in the European Alps beginning around 1850 (when glaciers began to retreat but temperatures continued to decline and precipitation was unchanged) very likely was driven by the massive increases in deposition to snow and ice of black carbon from industrialization in surrounding nations. A more robust understanding of changes in mountain snow and ice during the Anthropocene requires that we move past simplistic treatments (e.g. temperature-index modeling) to energy balance approaches that assess changes in the individual forcings such as the most powerful <span class="hlt">component</span> for melt - net solar radiation. Remote sensing retrievals from imaging spectrometers and multispectral sensors are giving us more powerful insights into the time-space variation of snow and ice albedo.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ACP....17.2401C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ACP....17.2401C"><span>Emission, transport, and radiative effects of mineral <span class="hlt">dust</span> from the Taklimakan and Gobi deserts: comparison of measurements and model results</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chen, Siyu; Huang, Jianping; Kang, Litai; Wang, Hao; Ma, Xiaojun; He, Yongli; Yuan, Tiangang; Yang, Ben; Huang, Zhongwei; Zhang, Guolong</p> <p>2017-02-01</p> <p>The Weather Research and Forecasting Model with chemistry (WRF-Chem model) was used to investigate a typical <span class="hlt">dust</span> storm event that occurred from 18 to 23 March 2010 and swept across almost all of China, Japan, and Korea. The spatial and temporal variations in <span class="hlt">dust</span> aerosols and the meteorological conditions over East Asia were well reproduced by the WRF-Chem model. The simulation results were used to further investigate the details of processes related to <span class="hlt">dust</span> emission, long-range transport, and radiative effects of <span class="hlt">dust</span> aerosols over the Taklimakan Desert (TD) and Gobi Desert (GD). The results indicated that weather conditions, topography, and surface types in <span class="hlt">dust</span> source regions may influence <span class="hlt">dust</span> emission, uplift height, and transport at the regional scale. The GD was located in the <span class="hlt">warm</span> zone in advance of the cold front in this case. Rapidly <span class="hlt">warming</span> surface temperatures and cold air advection at high levels caused strong instability in the atmosphere, which strengthened the downward momentum transported from the middle and low troposphere and caused strong surface winds. Moreover, the GD is located in a relatively flat, high-altitude region influenced by the confluence of the northern and southern westerly jets. Therefore, the GD <span class="hlt">dust</span> particles were easily lofted to 4 km and were the primary contributor to the <span class="hlt">dust</span> concentration over East Asia. In the <span class="hlt">dust</span> budget analysis, the <span class="hlt">dust</span> emission flux over the TD was 27.2 ± 4.1 µg m-2 s-1, which was similar to that over the GD (29 ± 3.6 µg m-2 s-1). However, the transport contribution of the TD <span class="hlt">dust</span> (up to 0.8 ton d-1) to the <span class="hlt">dust</span> sink was much smaller than that of the GD <span class="hlt">dust</span> (up to 3.7 ton d-1) because of the complex terrain and the prevailing wind in the TD. Notably, a small amount of the TD <span class="hlt">dust</span> (PM2.5 <span class="hlt">dust</span> concentration of approximately 8.7 µg m-3) was lofted to above 5 km and transported over greater distances under the influence of the westerly jets. Moreover, the direct radiative forcing induced by <span class="hlt">dust</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.A33G0323T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.A33G0323T"><span>Development of A <span class="hlt">Dust</span> Climate Indicator for the US National Climate Assessment</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tong, D.; Wang, J. X. L.; Gill, T. E.; Van Pelt, S.; Kim, D.</p> <p>2016-12-01</p> <p><span class="hlt">Dust</span> activity is a relatively simple but practical indicator to document the response of dryland ecosystems to climate change, making it an integral part of the National Climate Assessment (NCA). We present here a multi-agency collaboration that aims at developing a suite of <span class="hlt">dust</span> climate indicators to document and monitor the long-term variability and trend of <span class="hlt">dust</span> storm activity in the western United States. Recent <span class="hlt">dust</span> observations have revealed rapid intensification of <span class="hlt">dust</span> storm activity in the western United States. This trend is also closely correlated with a rapid increase in <span class="hlt">dust</span> deposition in rainwater and "valley fever" hospitalization in southwestern states. It remains unclear, however, if such a trend, when enhanced by predicted <span class="hlt">warming</span> and rainfall oscillation in the Southwest, will result in irreversible environmental development such as desertification or even another "<span class="hlt">Dust</span> Bowl". Based on continuous ground aerosol monitoring, we have reconstructed a long-term <span class="hlt">dust</span> storm climatology in the western United States. We report here direct evidence of rapid intensification of <span class="hlt">dust</span> storm activity over US deserts in the past decades (1990 to 2013), in contrast to the decreasing trends in Asia and Africa. The US trend is spatially and temporally correlated with incidences of valley fever, an infectious disease caused by soil-dwelling fungus that has increased eight-fold in the past decade. We further investigate the linkage between <span class="hlt">dust</span> variations and possible climate drivers and find that the regional <span class="hlt">dust</span> trends are likely driven by large-scale variations of sea surface temperature in the Pacific Ocean, with the strongest correlation with the Pacific Decadal Oscillation (PDO). Future study will explore the link between the temporal and spatial trends of increase in dustiness and vegetation change in southwestern semi-arid and arid ecosystems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=34633','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=34633"><span>Aeolian <span class="hlt">dust</span> in Colorado Plateau soils: Nutrient inputs and recent change in source</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Reynolds, Richard; Belnap, Jayne; Reheis, Marith; Lamothe, Paul; Luiszer, Fred</p> <p>2001-01-01</p> <p>Aeolian <span class="hlt">dust</span> (windblown silt and clay) is an important <span class="hlt">component</span> in arid-land ecosystems because it may contribute to soil formation and furnish essential nutrients. Few geologic surfaces, however, have been characterized with respect to <span class="hlt">dust</span>-accumulation history and resultant nutrient enrichment. We have developed a combination of methods to identify the presence of aeolian <span class="hlt">dust</span> in arid regions and to evaluate the roles of this <span class="hlt">dust</span> in ecosystem processes. Unconsolidated sandy sediment on isolated surfaces in the Canyonlands region of the Colorado Plateau differs greatly in mineralogical and chemical composition from associated bedrock, mainly aeolian sandstone. Detrital magnetite in the surficial deposits produces moderately high values of magnetic susceptibility, but magnetite is absent in nearby bedrock. A <span class="hlt">component</span> of the surficial deposits must be aeolian to account for the abundance of magnetite, which formed originally in far-distant igneous rocks. Particle-size analysis suggests that the aeolian <span class="hlt">dust</span> <span class="hlt">component</span> is typically as much as 20–30%. <span class="hlt">Dust</span> inputs have enriched the sediments in many elements, including P, Mg, Na, K, and Mo, as well as Ca, at sites where bedrock lacks calcite cement. Soil-surface biologic crusts are effective <span class="hlt">dust</span> traps that apparently record a change in <span class="hlt">dust</span> sources over the past several decades. Some of the recently fallen <span class="hlt">dust</span> may result from human disturbance of land surfaces that are far from the Canyonlands, such as the Mojave Desert. Some land-use practices in the study area have the potential to deplete soil fertility by means of wind-erosion removal of aeolian silt. PMID:11390965</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/1016204','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/1016204"><span>Aeolian <span class="hlt">dust</span> in Colorado Plateau soils: Nutrient inputs and recent change in source</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Reynolds, R.; Belnap, Jayne; Lamothe, Paul; Luiszer, Fred</p> <p>2001-01-01</p> <p>Aeolian <span class="hlt">dust</span> (windblown silt and clay) is an important <span class="hlt">component</span> in arid-land ecosystems because it may contribute to soil formation and furnish essential nutrients. Few geologic surfaces, however, have been characterized with respect to <span class="hlt">dust</span>-accumulation history and resultant nutrient enrichment. We have developed a combination of methods to identify the presence of aeolian <span class="hlt">dust</span> in arid regions and to evaluate the roles of this <span class="hlt">dust</span> in ecosystem processes. Unconsolidated sandy sediment on isolated surfaces in the Canyonlands region of the Colorado Plateau differs greatly in mineralogical and chemical composition from associated bedrock, mainly aeolian sandstone. Detrital magnetite in the surficial deposits produces moderately high values of magnetic susceptibility, but magnetite is absent in nearby bedrock. A <span class="hlt">component</span> of the surficial deposits must be aeolian to account for the abundance of magnetite, which formed originally in far-distant igneous rocks. Particle-size analysis suggests that the aeolian <span class="hlt">dust</span> <span class="hlt">component</span> is typically as much as 20a??30%. <span class="hlt">Dust</span> inputs have enriched the sediments in many elements, including P, Mg, Na, K, and Mo, as well as Ca, at sites where bedrock lacks calcite cement. Soil-surface biologic crusts are effective <span class="hlt">dust</span> traps that apparently record a change in <span class="hlt">dust</span> sources over the past several decades. Some of the recently fallen <span class="hlt">dust</span> may result from human disturbance of land surfaces that are far from the Canyonlands, such as the Mojave Desert. Some land-use practices in the study area have the potential to deplete soil fertility by means of wind-erosion removal of aeolian silt.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_12 --> <div id="page_13" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="241"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/16482974','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16482974"><span><span class="hlt">Dust</span> in the underground railway tunnels of an Italian town.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ripanucci, G; Grana, M; Vicentini, L; Magrini, A; Bergamaschi, A</p> <p>2006-01-01</p> <p>This article assesses hazards associated with exposure to <span class="hlt">dust</span> in tunnels and platforms of the A and B lines of Rome's underground railway and provides an informed opinion on the risks to workers and the travelling public of exposure to tunnel <span class="hlt">dust</span>. The study focused on the analysis and measurement of <span class="hlt">dust</span> granulometric classes PM10, respirable fraction, respirable combustible <span class="hlt">dust</span>, and the organic, metallic, siliceous, and fibrous <span class="hlt">components</span>. Comparing the measurement values from the tunnels and platforms with those found at the entrances to the underground railway stations, it emerges that <span class="hlt">dust</span> concentration in the tunnels and platforms is three times higher, with a maximum PM10 value of 479 microg/m3. Averaged over 24 hours, in relation to the above ground levels, drivers and station staff are exposed to an additional value of 11 microg/m3 and 10 microg/m3, respectively. If commuters were to remain in the trains or on the station platforms, the 24-hour average exposure would increase by 3 microg/m3. Iron and silica were the major <span class="hlt">components</span> found in the <span class="hlt">dust</span>. The use of silica sand in the emergency braking system of the carriages is capable of causing a dispersion of quartz in the air in percentages varying from 5% to 14%. Methods are suggested in this article for the reduction of <span class="hlt">dust</span> dispersion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012A%26A...541A..38R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012A%26A...541A..38R"><span><span class="hlt">Warm</span> debris disks candidates in transiting planets systems</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ribas, Á.; Merín, B.; Ardila, D. R.; Bouy, H.</p> <p>2012-05-01</p> <p>We have bandmerged candidate transiting planetary systems (from the Kepler satellite) and confirmed transiting planetary systems (from the literature) with the recent Wide-field Infrared Survey Explorer (WISE) preliminary release catalog. We have found 13 stars showing infrared excesses at either 12 μm and/or 22 μm. Without longer wavelength observations it is not possible to conclusively determine the nature of the excesses, although we argue that they are likely due to debris disks around the stars. If confirmed, our sample ~doubles the number of currently known <span class="hlt">warm</span> excess disks around old main sequence stars. The ratios between the measured fluxes and the stellar photospheres are generally larger than expected for Gyr-old stars, such as these planetary hosts. Assuming temperature limits for the <span class="hlt">dust</span> and emission from large <span class="hlt">dust</span> particles, we derive estimates for the disk radii. These values are comparable to the planet's semi-major axis, suggesting that the planets may be stirring the planetesimals in the system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009EGUGA..1111357A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EGUGA..1111357A"><span>Mineral <span class="hlt">dust</span> transport and deposition to Antarctica: a climate model perspective</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Albani, S.; Mahowald, N. M.; Maggi, V.; Delmonte, B.</p> <p>2009-04-01</p> <p>Windblown mineral <span class="hlt">dust</span> is a useful proxy for paleoclimates. Its life cycle is determined by climate conditions in the source areas, and following the hydrological cycle, and the intensity and dynamics of the atmospheric circulation. In addition aeolian <span class="hlt">dust</span> itself is an active <span class="hlt">component</span> of the climate system, influencing the radiative balance of the atmosphere through its interaction with incoming solar radiation and outgoing planetary radiation. The mineral aerosols also have indirect effects on climate, and are linked to interactions with cloud microphysics and atmospheric chemistry as well as to <span class="hlt">dust</span>'s role of carrier of iron and other elements that constitute limitating nutrients for phytoplancton to remote ocean areas. We use climate model (CCSM) simulations that include a scheme for <span class="hlt">dust</span> mobilization, transport and deposition in order to describe the evolution of <span class="hlt">dust</span> deposition in some Antarctic ice cores sites where mineral <span class="hlt">dust</span> records are available. Our focus is to determine the source apportionment for <span class="hlt">dust</span> deposited to Antarctica under current and Last Glacial Maximum climate conditions, as well as to give an insight in the spatial features of transport patterns. The understanding of spatial and temporal representativeness of an ice core record is crucial to determine its value as a proxy of past climates and a necessary step in order to produce a global picture of how the <span class="hlt">dust</span> <span class="hlt">component</span> of the climate system has changed through time.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018E%26PSL.481...30S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018E%26PSL.481...30S"><span>Early-Holocene greening of the Afro-Asian <span class="hlt">dust</span> belt changed sources of mineral <span class="hlt">dust</span> in West Asia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sharifi, Arash; Murphy, Lisa N.; Pourmand, Ali; Clement, Amy C.; Canuel, Elizabeth A.; Naderi Beni, Abdolmajid; Lahijani, Hamid A. K.; Delanghe, Doriane; Ahmady-Birgani, Hesam</p> <p>2018-01-01</p> <p>Production, transport and deposition of mineral <span class="hlt">dust</span> have significant impacts on different <span class="hlt">components</span> of the Earth systems through time and space. In modern times, <span class="hlt">dust</span> plumes are associated with their source region(s) using satellite and land-based measurements and trajectory analysis of air masses through time. Reconstruction of past changes in the sources of mineral <span class="hlt">dust</span> as related to changes in climate, however, must rely on the knowledge of the geochemical and mineralogical composition of modern and paleo-<span class="hlt">dust</span>, and that of their potential source origins. In this contribution, we present a 13,000-yr record of variations in radiogenic Sr-Nd-Hf isotopes and Rare Earth Element (REE) anomalies as well as <span class="hlt">dust</span> grain size from an ombrotrophic (rain fed) peat core in NW Iran as proxies of past changes in the sources of <span class="hlt">dust</span> over the interior of West Asia. Our data shows that although the grain size of <span class="hlt">dust</span> varies in a narrow range through the entire record, the geochemical fingerprint of <span class="hlt">dust</span> particles deposited during the low-flux, early Holocene period (11,700-6,000 yr BP) is distinctly different from aerosols deposited during high <span class="hlt">dust</span> flux periods of the Younger Dryas and the mid-late Holocene (6,000-present). Our findings indicate that the composition of mineral <span class="hlt">dust</span> deposited at the study site changed as a function of prevailing atmospheric circulation regimes and land exposure throughout the last deglacial period and the Holocene. Simulations of atmospheric circulation over the region show the Northern Hemisphere Summer Westerly Jet was displaced poleward across the study area during the early Holocene when Northern Hemisphere insolation was higher due to the Earth's orbital configuration. This shift, coupled with lower <span class="hlt">dust</span> emissions simulated based on greening of the Afro-Asian <span class="hlt">Dust</span> Belt during the early Holocene likely led to potential sources in Central Asia dominating <span class="hlt">dust</span> export to West Asia during this period. In contrast, the dominant western and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018PhRvD..97f3516L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018PhRvD..97f3516L"><span>Gravitational waves from <span class="hlt">warm</span> inflation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Xi-Bin; Wang, He; Zhu, Jian-Yang</p> <p>2018-03-01</p> <p>A fundamental prediction of inflation is a nearly scale-invariant spectrum of gravitational wave. The features of such a signal provide extremely important information about the physics of the early universe. In this paper, we focus on several topics about <span class="hlt">warm</span> inflation. First, we discuss the stability property about <span class="hlt">warm</span> inflation based on nonequilibrium statistical mechanics, which gives more fundamental physical illustrations to thermal property of such model. Then, we calculate the power spectrum of gravitational waves generated during <span class="hlt">warm</span> inflation, in which there are three <span class="hlt">components</span> contributing to such spectrum: thermal term, quantum term, and cross term combining the both. We also discuss some interesting properties about these terms and illustrate them in different panels. As a model different from cold inflation, <span class="hlt">warm</span> inflation model has its individual properties in observational practice, so we finally give a discussion about the observational effect to distinguish it from cold inflation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018AeoRe..30...11A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018AeoRe..30...11A"><span>Characteristics of mineral <span class="hlt">dust</span> impacting the Persian Gulf</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ahmady-Birgani, Hesam; McQueen, Kenneth G.; Mirnejad, Hassan</p> <p>2018-02-01</p> <p>It is generally assumed that severe <span class="hlt">dust</span> events in western Iran could be responsible for elevated levels of toxic and radioactive elements in the region. Over a period of 5 months, from January 2012 to May 2012, <span class="hlt">dust</span> particles in the size range PM10 (i.e. <10 μm) were collected at Abadan, a site beside the Persian Gulf. The research aim was to compare chemical compositions of <span class="hlt">dust</span> and aerosol samples collected during the non-dusty periods and during two severe <span class="hlt">dust</span> events. Results of ICP-MS analysis of <span class="hlt">components</span> indicate that during <span class="hlt">dust</span> events the concentrations of major elements such as Ca, Mg, Al and K increase relative to ambient conditions when Fe and trace elements such as Cu, Cr, Ni, Pb and Zn are in higher proportions. Toxic trace elements that are generally ascribed to human activities, including industrial and urban pollution, are thus proportionately more abundant in the <span class="hlt">dust</span> under calm conditions than during <span class="hlt">dust</span> events, when their concentration is diluted by more abundant mineral particles of quartz, calcite and clay. The variability of chemical species during two <span class="hlt">dust</span> events, noted by tracking the <span class="hlt">dust</span> plumes in satellite images, was also assessed and the results relate to two different source areas, namely northern Iraq and northwestern Syria.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011A%26A...536A..17P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011A%26A...536A..17P"><span>Planck early results. XVII. Origin of the submillimetre excess <span class="hlt">dust</span> emission in the Magellanic Clouds</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Planck Collaboration; Ade, P. A. R.; Aghanim, N.; Arnaud, M.; Ashdown, M.; Aumont, J.; Baccigalupi, C.; Balbi, A.; Banday, A. J.; Barreiro, R. B.; Bartlett, J. G.; Battaner, E.; Benabed, K.; Benoît, A.; Bernard, J.-P.; Bersanelli, M.; Bhatia, R.; Bock, J. J.; Bonaldi, A.; Bond, J. R.; Borrill, J.; Bot, C.; Bouchet, F. R.; Boulanger, F.; Bucher, M.; Burigana, C.; Cabella, P.; Cardoso, J.-F.; Catalano, A.; Cayón, L.; Challinor, A.; Chamballu, A.; Chiang, L.-Y.; Chiang, C.; Christensen, P. R.; Clements, D. L.; Colombi, S.; Couchot, F.; Coulais, A.; Crill, B. P.; Cuttaia, F.; Danese, L.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; de Gasperis, G.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Delouis, J.-M.; Désert, F.-X.; Dickinson, C.; Dobashi, K.; Donzelli, S.; Doré, O.; Dörl, U.; Douspis, M.; Dupac, X.; Efstathiou, G.; Enßlin, T. A.; Finelli, F.; Forni, O.; Frailis, M.; Franceschi, E.; Fukui, Y.; Galeotta, S.; Ganga, K.; Giard, M.; Giardino, G.; Giraud-Héraud, Y.; González-Nuevo, J.; Górski, K. M.; Gratton, S.; Gregorio, A.; Gruppuso, A.; Harrison, D.; Helou, G.; Henrot-Versillé, S.; Herranz, D.; Hildebrandt, S. R.; Hivon, E.; Hobson, M.; Holmes, W. A.; Hovest, W.; Hoyland, R. J.; Huffenberger, K. M.; Jaffe, A. H.; Jones, W. C.; Juvela, M.; Kawamura, A.; Keihänen, E.; Keskitalo, R.; Kisner, T. S.; Kneissl, R.; Knox, L.; Kurki-Suonio, H.; Lagache, G.; Lähteenmäki, A.; Lamarre, J.-M.; Lasenby, A.; Laureijs, R. J.; Lawrence, C. R.; Leach, S.; Leonardi, R.; Leroy, C.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P. M.; Macías-Pérez, J. F.; MacTavish, C. J.; Madden, S.; Maffei, B.; Mandolesi, N.; Mann, R.; Maris, M.; Martínez-González, E.; Masi, S.; Matarrese, S.; Matthai, F.; Mazzotta, P.; Meinhold, P. R.; Melchiorri, A.; Mendes, L.; Mennella, A.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Munshi, D.; Murphy, A.; Naselsky, P.; Nati, F.; Natoli, P.; Netterfield, C. B.; Nørgaard-Nielsen, H. U.; Noviello, F.; Novikov, D.; Novikov, I.; Onishi, T.; Osborne, S.; Pajot, F.; Paladini, R.; Paradis, D.; Pasian, F.; Patanchon, G.; Perdereau, O.; Perotto, L.; Perrotta, F.; Piacentini, F.; Piat, M.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Ponthieu, N.; Poutanen, T.; Prézeau, G.; Prunet, S.; Puget, J.-L.; Reach, W. T.; Rebolo, R.; Reinecke, M.; Renault, C.; Ricciardi, S.; Riller, T.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Rowan-Robinson, M.; Rubiño-Martín, J. A.; Rusholme, B.; Sandri, M.; Savini, G.; Scott, D.; Seiffert, M. D.; Smoot, G. F.; Starck, J.-L.; Stivoli, F.; Stolyarov, V.; Sudiwala, R.; Sygnet, J.-F.; Tauber, J. A.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Torre, J.-P.; Tristram, M.; Tuovinen, J.; Umana, G.; Valenziano, L.; Varis, J.; Vielva, P.; Villa, F.; Vittorio, N.; Wade, L. A.; Wandelt, B. D.; Wilkinson, A.; Ysard, N.; Yvon, D.; Zacchei, A.; Zonca, A.</p> <p>2011-12-01</p> <p>The integrated spectral energy distributions (SED) of the Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC) appear significantly flatter than expected from <span class="hlt">dust</span> models based on their far-infrared and radio emission. The still unexplained origin of this millimetre excess is investigated here using the Planck data. The integrated SED of the two galaxies before subtraction of the foreground (Milky Way) and background (CMB fluctuations) emission are in good agreement with previous determinations, confirming the presence of the millimetre excess. In the context of this preliminary analysis we do not propose a full multi-<span class="hlt">component</span> fitting of the data, but instead subtract contributions unrelated to the galaxies and to <span class="hlt">dust</span> emission. The background CMB contribution is subtracted using an internal linear combination (ILC) method performed locally around the galaxies. The foreground emission from the Milky Way is subtracted as a Galactic Hi template, and the <span class="hlt">dust</span> emissivity is derived in a region surrounding the two galaxies and dominated by Milky Way emission. After subtraction, the remaining emission of both galaxies correlates closely with the atomic and molecular gas emission of the LMC and SMC. The millimetre excess in the LMC can be explained by CMB fluctuations, but a significant excess is still present in the SMC SED. The Planck and IRAS-IRIS data at 100 μm are combined to produce thermal <span class="hlt">dust</span> temperature and optical depth maps of the two galaxies. The LMC temperature map shows the presence of a <span class="hlt">warm</span> inner arm already found with the Spitzer data, but which also shows the existence of a previously unidentified cold outer arm. Several cold regions are found along this arm, some of which are associated with known molecular clouds. The <span class="hlt">dust</span> optical depth maps are used to constrain the thermal <span class="hlt">dust</span> emissivity power-law index (β). The average spectral index is found to be consistent with β = 1.5 and β = 1.2 below 500μm for the LMC and SMC respectively</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20130013116','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20130013116"><span>On the Effect of <span class="hlt">Dust</span> Particles on Global Cloud Condensation Nuclei and Cloud Droplet Number</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Karydis, V. A.; Kumar, P.; Barahona, D.; Sokolik, I. N.; Nenes, A.</p> <p>2011-01-01</p> <p>Aerosol-cloud interaction studies to date consider aerosol with a substantial fraction of soluble material as the sole source of cloud condensation nuclei (CCN). Emerging evidence suggests that mineral <span class="hlt">dust</span> can act as good CCN through water adsorption onto the surface of particles. This study provides a first assessment of the contribution of insoluble <span class="hlt">dust</span> to global CCN and cloud droplet number concentration (CDNC). Simulations are carried out with the NASA Global Modeling Initiative chemical transport model with an online aerosol simulation, considering emissions from fossil fuel, biomass burning, marine, and <span class="hlt">dust</span> sources. CDNC is calculated online and explicitly considers the competition of soluble and insoluble CCN for water vapor. The predicted annual average contribution of insoluble mineral <span class="hlt">dust</span> to CCN and CDNC in cloud-forming areas is up to 40 and 23.8%, respectively. Sensitivity tests suggest that uncertainties in <span class="hlt">dust</span> size distribution and water adsorption parameters modulate the contribution of mineral <span class="hlt">dust</span> to CDNC by 23 and 56%, respectively. Coating of <span class="hlt">dust</span> by hygroscopic salts during the atmospheric aging causes a twofold enhancement of the <span class="hlt">dust</span> contribution to CCN; the aged <span class="hlt">dust</span>, however, can substantially deplete in-cloud supersaturation during the initial stages of cloud formation and can eventually reduce CDNC. Considering the hydrophilicity from adsorption and hygroscopicity from solute is required to comprehensively capture the <span class="hlt">dust-warm</span> cloud interactions. The framework presented here addresses this need and can be easily integrated in atmospheric models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017MNRAS.468.2532J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017MNRAS.468.2532J"><span>Probing the interstellar <span class="hlt">dust</span> towards the Galactic Centre: <span class="hlt">dust</span>-scattering halo around AX J1745.6-2901</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jin, Chichuan; Ponti, Gabriele; Haberl, Frank; Smith, Randall</p> <p>2017-07-01</p> <p>AX J1745.6-2901 is an X-ray binary located at only 1.45 arcmin from Sgr A⋆, showcasing a strong X-ray <span class="hlt">dust</span>-scattering halo. We combine Chandra and XMM-Newton observations to study the halo around this X-ray binary. Our study shows two major thick <span class="hlt">dust</span> layers along the line of sight (LOS) towards AX J1745.6-2901. The LOS position and NH of these two layers depend on the <span class="hlt">dust</span> grain models with different grain size distributions and abundances. But for all the 19 <span class="hlt">dust</span> grain models considered, <span class="hlt">dust</span> layer-1 is consistently found to be within a fractional distance of 0.11 (mean value: 0.05) to AX J1745.6-2901 and contains only (19-34) per cent (mean value: 26 per cent) of the total LOS <span class="hlt">dust</span>. The remaining <span class="hlt">dust</span> is contained in layer-2, which is distributed from the Earth up to a mean fractional distance of 0.64. A significant separation between the two layers is found for all the <span class="hlt">dust</span> grain models, with a mean fractional distance of 0.31. Besides, an extended wing <span class="hlt">component</span> is discovered in the halo, which implies a higher fraction of <span class="hlt">dust</span> grains with typical sizes ≲590 Å than considered in current <span class="hlt">dust</span> grain models. Assuming AX J1745.6-2901 is 8 kpc away, <span class="hlt">dust</span> layer-2 would be located in the Galactic disc several kpc away from the Galactic Centre (GC). The <span class="hlt">dust</span> scattering halo biases the observed spectrum of AX J1745.6-2901 severely in both spectral shape and flux, and also introduces a strong dependence on the size of the instrumental point spread function and the source extraction region. We build xspec models to account for this spectral bias, which allow us to recover the intrinsic spectrum of AX J1745.6-2901 free from <span class="hlt">dust</span>-scattering opacity. If <span class="hlt">dust</span> layer-2 also intervenes along the LOS to Sgr A⋆ and other nearby GC sources, a significant spectral correction for the <span class="hlt">dust</span>-scattering opacity would be necessary for all these GC sources.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.7232J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.7232J"><span>Global potential of <span class="hlt">dust</span> devil occurrence</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jemmett-Smith, Bradley; Marsham, John; Knippertz, Peter; Gilkeson, Carl</p> <p>2014-05-01</p> <p>Mineral <span class="hlt">dust</span> is a key constituent in the climate system. Airborne mineral <span class="hlt">dust</span> forms the largest <span class="hlt">component</span> of the global aerosol budget by mass and subsequently affects climate, weather and biogeochemical processes. There remains large uncertainty in the quantitative estimates of the <span class="hlt">dust</span> cycle. Dry boundary-layer convection serves as an effective mechanism for <span class="hlt">dust</span> uplift, typically through a combination of rotating <span class="hlt">dust</span> devils and non-rotating larger and longer-lived convective plumes. These microscale dry-convective processes occur over length scales of several hundred metres or less. They are difficult to observe and model, and therefore their contribution to the global <span class="hlt">dust</span> budget is highly uncertain. Using an analytical approach to extrapolate limited observations, Koch and Renno (2006) suggest that <span class="hlt">dust</span> devils and plumes could contribute as much as 35%. Here, we use a new method for quantifying the potential of <span class="hlt">dust</span> devil occurrence to provide an alternative perspective on this estimate. Observations have shown that <span class="hlt">dust</span> devil and convective plume occurrence is favoured in hot arid regions under relatively weak background winds, large ground-to-air temperature gradients and deep dry convection. By applying such known constraints to operational analyses from the European Centre for Medium Range Weather Forecasts (ECMWF), we provide, to the best of the authors' knowledge, the first hourly estimates of <span class="hlt">dust</span> devil occurrence including an analysis of sensitivity to chosen threshold uplift. The results show the expected diurnal variation and allow an examination of the seasonal cycle and day-to-day variations in the conditions required for <span class="hlt">dust</span> devil formation. They confirm that desert regions are expected to have by far the highest frequency of dry convective vortices, with winds capable of <span class="hlt">dust</span> uplift. This approach is used to test the findings of Koch and Renno (2006). Koch J., Renno N. (2006). The role of convective plumes and vortices on the global aerosol</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JNuM..463..877R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JNuM..463..877R"><span>Elastic-plastic adhesive impacts of tungsten <span class="hlt">dust</span> with metal surfaces in plasma environments</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ratynskaia, S.; Tolias, P.; Shalpegin, A.; Vignitchouk, L.; De Angeli, M.; Bykov, I.; Bystrov, K.; Bardin, S.; Brochard, F.; Ripamonti, D.; den Harder, N.; De Temmerman, G.</p> <p>2015-08-01</p> <p><span class="hlt">Dust</span>-surface collisions impose size selectivity on the ability of <span class="hlt">dust</span> grains to migrate in scrape-off layer and divertor plasmas and to adhere to plasma-facing <span class="hlt">components</span>. Here, we report first experimental evidence of <span class="hlt">dust</span> impact phenomena in plasma environments concerning low-speed collisions of tungsten <span class="hlt">dust</span> with tungsten surfaces: re-bouncing, adhesion, sliding and rolling. The results comply with the predictions of the model of elastic-perfectly plastic adhesive spheres employed in the <span class="hlt">dust</span> dynamics code MIGRAINe for sub- to several meters per second impacts of micrometer-range metal <span class="hlt">dust</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017MNRAS.472.4750D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017MNRAS.472.4750D"><span>Infrared <span class="hlt">dust</span> bubble CS51 and its interaction with the surrounding interstellar medium</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Das, Swagat R.; Tej, Anandmayee; Vig, Sarita; Liu, Hong-Li; Liu, Tie; Ishwara Chandra, C. H.; Ghosh, Swarna K.</p> <p>2017-12-01</p> <p>A multiwavelength investigation of the southern infrared <span class="hlt">dust</span> bubble CS51 is presented in this paper. We probe the associated ionized, cold <span class="hlt">dust</span>, molecular and stellar <span class="hlt">components</span>. Radio continuum emission mapped at 610 and 1300 MHz, using the Giant Metrewave Radio Telescope, India, reveals the presence of three compact emission <span class="hlt">components</span> (A, B, and C) apart from large-scale diffuse emission within the bubble interior. Radio spectral index map shows the co-existence of thermal and non-thermal emission <span class="hlt">components</span>. Modified blackbody fits to the thermal <span class="hlt">dust</span> emission using Herschel Photodetector Array Camera and Spectrometer and Spectral and Photometric Imaging Receiver data is performed to generate <span class="hlt">dust</span> temperature and column density maps. We identify five <span class="hlt">dust</span> clumps associated with CS51 with masses and radius in the range 810-4600 M⊙ and 1.0-1.9 pc, respectively. We further construct the column density probability distribution functions of the surrounding cold <span class="hlt">dust</span> which display the impact of ionization feedback from high-mass stars. The estimated dynamical and fragmentation time-scales indicate the possibility of collect and collapse mechanism in play at the bubble border. Molecular line emission from the Millimeter Astronomy Legacy Team 90 GHz survey is used to understand the nature of two clumps which show signatures of expansion of CS51.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.A14C..06P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.A14C..06P"><span>How Early Holocene Greening of the Afro-Asian <span class="hlt">Dust</span> Belt Changed Sources of Mineral <span class="hlt">Dust</span> in West Asia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pourmand, A.; Sharifi, A.; Goes, L. M.; Clement, A. C.; Canuel, E. A.; Naderi Beni, A.; Ahmady-Birgani, H.</p> <p>2016-12-01</p> <p>Production, transport and deposition of mineral <span class="hlt">dust</span> have significant temporal and spatial impacts on different <span class="hlt">components</span> of the Earth systems. In modern times, <span class="hlt">dust</span> plumes can be associated with their source origin(s) using satellite and land-based measurements and back-trajectory reconstruction of air masses. Reconstructing past changes in the sources of mineral <span class="hlt">dust</span> as related to changes in climate, however, must rely on the knowledge of the geochemical and mineralogical composition of modern and paleo-<span class="hlt">dust</span>, and their potential source origins. In this contribution, we present a 13,000-year record of variations in radiogenic Sr-Nd-Hf isotopes and Rare Earth Element (REE) anomalies from an ombrotrophic (rain fed) peat core in NW Iran as proxies of past changes in sources of <span class="hlt">dust</span> over West Asia. The geochemical fingerprint of <span class="hlt">dust</span> particles deposited during the low-flux, early Holocene period (11,700-6,000 yr BP) is distinctly different from times of high <span class="hlt">dust</span> fluxes during the Younger Dryas, and that of the mid-late Holocene. This indicates that the composition of mineral <span class="hlt">dust</span> deposited at the receptor site changed as a function of prevailing atmospheric circulation regimes and land exposure. Simulations of atmospheric circulation over the region show the Northern Hemisphere Westerly Jet (NHWJ) was displaced poleward across the study area during the early Holocene when solar insolation was higher. This shift, coupled with lower <span class="hlt">dust</span> emissions simulated based on greening of the Afro-Asian <span class="hlt">Dust</span> Belt during the early Holocene likely led to potential sources in Central Asia to dominate <span class="hlt">dust</span> export to West Asia during this period, in contrast to the dominant western and southwest Asian and Eastern African sources that prevail during the modern period.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1474388','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1474388"><span>Vegetable <span class="hlt">dust</span> and airway disease: inflammatory mechanisms.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Cooper, J A; Buck, M G; Gee, J B</p> <p>1986-01-01</p> <p>Exposure to cotton or grain <span class="hlt">dust</span> causes an obstructive bronchitis in certain subjects, mechanisms of which are poorly understood. A difficulty encountered in discerning mechanisms of this airway disease is the lack of knowledge of the active <span class="hlt">components</span> of these <span class="hlt">dusts</span>. Clinical features suggest common but not exact mechanisms of the airway disease associated with these vegetable <span class="hlt">dusts</span>. Human and animal studies show evidence of acellular and cellular inflammatory mechanisms of the bronchoconstriction and inflammation associated with these disorders. Potential cellular sources include alveolar macrophages, polymorphonuclear leukocytes, mast cells, basophils, eosinophils and lymphocytes. Acellular origins include the complement and humoral antibody systems, both of which have been implicated, although their pathogenic role in grain or cotton <span class="hlt">dust</span> disorders is uncertain. In this review we critically address potential inflammatory mechanisms of airway alterations resulting from cotton or grain <span class="hlt">dust</span> exposure. General mechanisms of bronchoconstriction are first presented, then specific studies dealing with either of the two <span class="hlt">dusts</span> are discussed. We believe this area of research may be fruitful in dissecting mechanisms of bronchoconstriction and airway inflammation, especially as more human studies are undertaken. PMID:3519205</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1713093C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1713093C"><span>MicroMED: a <span class="hlt">dust</span> particle counter for the characterization of airborne <span class="hlt">dust</span> close to the surface of Mars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cozzolino, Fabio; Esposito, Francesca; Molfese, Cesare; Cortecchia, Fausto; Saggin, Bortolino; D'amato, Francesco</p> <p>2015-04-01</p> <p>Monitoring of airborne <span class="hlt">dust</span> is very important in planetary climatology. Indeed, <span class="hlt">dust</span> absorbs and scatter solar and thermal radiation, severely affecting atmospheric thermal structure, balance and dynamics (in terms of circulations). Wind-driven blowing of sand and <span class="hlt">dust</span> is also responsible for shaping planetary surfaces through the formation of sand dunes and ripples, the erosion of rocks, and the creation and transport of soil particles. <span class="hlt">Dust</span> is permanently present in the atmosphere of Mars and its amount varies with seasons. During regional or global <span class="hlt">dust</span> storms, more than 80% of the incoming sunlight is absorbed by <span class="hlt">dust</span> causing an intense atmospheric heating. Airborne <span class="hlt">dust</span> is therefore a crucial climate <span class="hlt">component</span> on Mars which impacts atmospheric circulations at all scales. Main <span class="hlt">dust</span> parameters influencing the atmosphere heating are size distribution, abundance, albedo, single scattering phase function, imaginary part of the index of refraction. Moreover, major improvements of Mars climate models require, in addition to the standard meteorological parameters, quantitative information about <span class="hlt">dust</span> lifting, transport and removal mechanisms. In this context, two major quantities need to be measured for the <span class="hlt">dust</span> source to be understood: surface flux and granulometry. While many observations have constrained the size distribution of the <span class="hlt">dust</span> haze seen from the orbit, it is still not known what the primary airborne <span class="hlt">dust</span> (e.g. the recently lifted <span class="hlt">dust</span>) is made of, size-wise. MicroMED has been designed to fill this gap. It will measure the abundance and size distribution of <span class="hlt">dust</span>, not in the atmospheric column, but close to the surface, where <span class="hlt">dust</span> is lifted, so to be able to monitor <span class="hlt">dust</span> injection into the atmosphere. This has never been performed in Mars and other planets exploration. MicroMED is an Optical Particle Counter, analyzing light scattered from single <span class="hlt">dust</span> particles to measure their size and abundance. A proper fluid-dynamic system, including a pump and a</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.A13M..04K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.A13M..04K"><span>The global impact of mineral <span class="hlt">dust</span> on cloud droplet number concentration</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Karydis, V.; Tsimpidi, A.; Bacer, S.; Pozzer, A.; Nenes, A.; Lelieveld, J.</p> <p>2016-12-01</p> <p>This study assesses the importance of mineral <span class="hlt">dust</span> for cloud droplet formation by taking into account i) the adsorption of water on the surface of insoluble <span class="hlt">dust</span> particles, ii) the coating of soluble material on the surface of mineral particles which augments their cloud condensation nuclei activity, and iii) the effect of <span class="hlt">dust</span> on the inorganic aerosol concentrations through thermodynamic interactions with mineral cations. Simulations are carried out with the EMAC chemistry climate model that calculates the global atmospheric aerosol composition using the ISORROPIA-II thermodynamic equilibrium model and considers the gas phase interactions with K+-Ca2+-Mg2+-NH4+-Na+-SO42-NO3-Cl-H2O particle <span class="hlt">components</span>. Emissions of the inert mineral <span class="hlt">dust</span> and the reactive <span class="hlt">dust</span> aerosol <span class="hlt">components</span> are calculated online by taking into account the soil particle size distribution and chemical composition of different deserts worldwide (Karydis et al., 2016). We have implemented the "unified <span class="hlt">dust</span> activation parameterization" (Kumar et al., 2011; Karydis et al., 2011) to calculate the droplet number concentration by taking into account the inherent hydrophilicity from adsorption and the acquired hygroscopicity from soluble salts by <span class="hlt">dust</span> particles. Our simulations suggest that mineral <span class="hlt">dust</span> significantly increases the cloud droplet number concentration (CDNC) over the main deserts and the adjacent oceans. However, over polluted areas the CDNC decreases significantly in the presence of <span class="hlt">dust</span>. Furthermore, we investigate the role of adsorption activation of insoluble aerosols and the mineral <span class="hlt">dust</span> thermodynamic interactions with inorganic anions on the cloud droplet formation. The CDNC sensitivity to the emission load, chemical composition, and inherent hydrophilicity of mineral <span class="hlt">dust</span> is also tested. ReferencesKarydis, et al. (2011). "On the effect of <span class="hlt">dust</span> particles on global cloud condensation nuclei and cloud droplet number." J. Geophys. Res. Atmos. 116. Karydis, et al. (2016). "Effects of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1813422S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1813422S"><span>Ice Nucleation Activity of Various Agricultural Soil <span class="hlt">Dust</span> Aerosol Particles</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schiebel, Thea; Höhler, Kristina; Funk, Roger; Hill, Thomas C. J.; Levin, Ezra J. T.; Nadolny, Jens; Steinke, Isabelle; Suski, Kaitlyn J.; Ullrich, Romy; Wagner, Robert; Weber, Ines; DeMott, Paul J.; Möhler, Ottmar</p> <p>2016-04-01</p> <p>Recent investigations at the cloud simulation chamber AIDA (Aerosol Interactions and Dynamics in the Atmosphere) suggest that agricultural soil <span class="hlt">dust</span> has an ice nucleation ability that is enhanced up to a factor of 10 compared to desert <span class="hlt">dust</span>, especially at temperatures above -26 °C (Steinke et al., in preparation for submission). This enhancement might be caused by the contribution of very ice-active biological particles. In addition, soil <span class="hlt">dust</span> aerosol particles often contain a considerably higher amount of organic matter compared to desert <span class="hlt">dust</span> particles. To test agricultural soil <span class="hlt">dust</span> as a source of ice nucleating particles, especially for ice formation in <span class="hlt">warm</span> clouds, we conducted a series of laboratory measurements with different soil <span class="hlt">dust</span> samples to extend the existing AIDA dataset. The AIDA has a volume of 84 m3 and operates under atmospherically relevant conditions over wide ranges of temperature, pressure and humidity. By controlled adiabatic expansions, the ascent of an air parcel in the troposphere can be simulated. As a supplement to the AIDA facility, we use the INKA (Ice Nucleation Instrument of the KArlsruhe Institute of Technology) continuous flow diffusion chamber based on the design by Rogers (1988) to expose the sampled aerosol particles to a continuously increasing saturation ratio by keeping the aerosol temperature constant. For our experiments, soil <span class="hlt">dust</span> was dry dispersed into the AIDA vessel. First, fast saturation ratio scans at different temperatures were performed with INKA, sampling soil <span class="hlt">dust</span> aerosol particles directly from the AIDA vessel. Then, we conducted the AIDA expansion experiment starting at a preset temperature. The combination of these two different methods provides a robust data set on the temperature-dependent ice activity of various agriculture soil <span class="hlt">dust</span> aerosol particles with a special focus on relatively high temperatures. In addition, to extend the data set, we investigated the role of biological and organic matter in more</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5968206','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5968206"><span>Road <span class="hlt">dust</span> and its effect on human health: a literature review</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p></p> <p>2018-01-01</p> <p>The purpose of this study was to determine the effects of road <span class="hlt">dust</span> on human health. A PubMed search was used to extract references that included the words “road dust” and “health” or “fugitive dust” and “health” in the title or abstract. A total of 46 references were extracted and selected for review after the primary screening of 949 articles. The respiratory system was found to be the most affected system in the human body. Lead, platinum-group elements (platinum, rhodium, and bohrium), aluminum, zinc, vanadium, and polycyclic aromatic hydrocarbons were the <span class="hlt">components</span> of road <span class="hlt">dust</span> that were most frequently referenced in the articles reviewed. Road <span class="hlt">dust</span> was found to have harmful effects on the human body, especially on the respiratory system. To determine the complex mechanism of action of various <span class="hlt">components</span> of road <span class="hlt">dust</span> on the human body and the results thereof, the authors recommend a further meta-analysis and extensive risk-assessment research into the health impacts of <span class="hlt">dust</span> exposure. PMID:29642653</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/15194923','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15194923"><span>Depleted uranium <span class="hlt">dust</span> from fired munitions: physical, chemical and biological properties.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mitchel, R E J; Sunder, S</p> <p>2004-07-01</p> <p>This paper reports physical, chemical and biological analyses of samples of <span class="hlt">dust</span> resulting from munitions containing depleted uranium (DU) that had been live-fired and had impacted an armored target. Mass spectroscopic analysis indicated that the average atom% of U was 0.198 +/- 0.10, consistent with depleted uranium. Other major elements present were iron, aluminum, and silicon. About 47% of the total mass was particles with diameters <300 microm, of which about 14% was <10 microm. X-ray diffraction analysis indicated that the uranium was present in the sample as uranium oxides-mainly U3O7 (47%), U3O8 (44%) and UO2 (9%). Depleted uranium <span class="hlt">dust</span>, instilled into the lungs or implanted into the muscle of rats, contained a rapidly soluble uranium <span class="hlt">component</span> and a more slowly soluble uranium <span class="hlt">component</span>. The fraction that underwent dissolution in 7 d declined exponentially with increasing initial burden. At the lower lung burdens tested (<15 microg DU <span class="hlt">dust</span>/lung) about 14% of the uranium appeared in urine within 7 d. At the higher lung burdens tested (~80-200 microg DU <span class="hlt">dust</span>/lung) about 5% of the DU appeared in urine within 7 d. In both cases about 50% of that total appeared in urine within the first day. DU implanted in muscle similarly showed that about half of the total excreted within 7 d appeared in the first day. At the lower muscle burdens tested (<15 microg DU <span class="hlt">dust</span>/injection site) about 9% was solubilized within 7 d. At muscle burdens >35 microg DU <span class="hlt">dust</span>/injection site about 2% appeared in urine within 7 d. Natural uranium (NU) ore <span class="hlt">dust</span> was instilled into rat lungs for comparison. The fraction dissolving in lung showed a pattern of exponential decline with increasing initial burden similar to DU. However, the decline was less steep, with about 14% appearing in urine for lung burdens up to about 200 microg NU <span class="hlt">dust</span>/lung and 5% at lung burdens >1,100 microg NU <span class="hlt">dust</span>/lung. NU also showed both a fast and a more slowly dissolving <span class="hlt">component</span>. At the higher lung burdens of both</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA21482.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA21482.html"><span>Curiosity Observes Whirlwinds Carrying Martian <span class="hlt">Dust</span></span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2017-02-27</p> <p><span class="hlt">Dust</span> devils dance in the distance in this frame from a sequence of images taken by the Navigation Camera on NASA's Curiosity Mars rover on Feb. 12, 2017, during the summer afternoon of the rover's 1,607th Martian day, or sol. Within a broader context view, the rectangular area outlined in black was imaged multiple times over a span of several minutes to check for <span class="hlt">dust</span> devils. Images from the period with most activity are shown in the inset area. The images are in pairs that were taken about 12 seconds apart, with an interval of about 90 seconds between pairs. Timing is accelerated and not fully proportional in this animation. One <span class="hlt">dust</span> devil appears at the right edge of the inset -- toward the south from the rover -- in the first few frames. Another appears on the left -- toward south-southeast -- later in the sequence. Contrast has been modified to make frame-to-frame changes easier to see. A black frame is added between repeats of the sequence. Portions of Curiosity are visible in the foreground. The cylindrical UHF (ultra-high frequency) antenna on the left is used for sending data to Mars orbiters, which relay the data to Earth. The angled planes to the right of this antenna are fins of the rover's radioisotope thermoelectric generator, which provides the vehicle's power. The post with a knob on top at right is a low-gain, non-directional antenna that can be used for receiving transmissions from Earth, as backup to the main high-gain antenna (not shown here) used for that purpose. On Mars as on Earth, <span class="hlt">dust</span> devils are whirlwinds that result from sunshine <span class="hlt">warming</span> the ground, prompting convective rising of air that has gained heat from the ground. Observations of Martian <span class="hlt">dust</span> devils provide information about wind directions and interaction between the surface and the atmosphere. An animation is available at http://photojournal.jpl.nasa.gov/catalog/PIA21482</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_13 --> <div id="page_14" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="261"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ApJ...788...86P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ApJ...788...86P"><span>Direct Measurements of <span class="hlt">Dust</span> Attenuation in z ~ 1.5 Star-forming Galaxies from 3D-HST: Implications for <span class="hlt">Dust</span> Geometry and Star Formation Rates</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Price, Sedona H.; Kriek, Mariska; Brammer, Gabriel B.; Conroy, Charlie; Förster Schreiber, Natascha M.; Franx, Marijn; Fumagalli, Mattia; Lundgren, Britt; Momcheva, Ivelina; Nelson, Erica J.; Skelton, Rosalind E.; van Dokkum, Pieter G.; Whitaker, Katherine E.; Wuyts, Stijn</p> <p>2014-06-01</p> <p>The nature of <span class="hlt">dust</span> in distant galaxies is not well understood, and until recently few direct <span class="hlt">dust</span> measurements have been possible. We investigate <span class="hlt">dust</span> in distant star-forming galaxies using near-infrared grism spectra of the 3D-HST survey combined with archival multi-wavelength photometry. These data allow us to make a direct comparison between <span class="hlt">dust</span> around star-forming regions (A V, H II ) and the integrated <span class="hlt">dust</span> content (A V, star). We select a sample of 163 galaxies between 1.36 <= z <= 1.5 with Hα signal-to-noise ratio >=5 and measure Balmer decrements from stacked spectra to calculate A V, H II . First, we stack spectra in bins of A V, star, and find that A V, H II = 1.86 A V, star, with a significance of σ = 1.7. Our result is consistent with the two-<span class="hlt">component</span> <span class="hlt">dust</span> model, in which galaxies contain both diffuse and stellar birth cloud <span class="hlt">dust</span>. Next, we stack spectra in bins of specific star formation rate (log SSFR), star formation rate (log SFR), and stellar mass (log M *). We find that on average A V, H II increases with SFR and mass, but decreases with increasing SSFR. Interestingly, the data hint that the amount of extra attenuation decreases with increasing SSFR. This trend is expected from the two-<span class="hlt">component</span> model, as the extra attenuation will increase once older stars outside the star-forming regions become more dominant in the galaxy spectrum. Finally, using Balmer decrements we derive <span class="hlt">dust</span>-corrected Hα SFRs, and find that stellar population modeling produces incorrect SFRs if rapidly declining star formation histories are included in the explored parameter space.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017A%26A...605A..93K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017A%26A...605A..93K"><span>Origin of <span class="hlt">warm</span> and hot gas emission from low-mass protostars: Herschel-HIFI observations of CO J = 16-15. I. Line profiles, physical conditions, and H2O abundance</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kristensen, L. E.; van Dishoeck, E. F.; Mottram, J. C.; Karska, A.; Yıldız, U. A.; Bergin, E. A.; Bjerkeli, P.; Cabrit, S.; Doty, S.; Evans, N. J.; Gusdorf, A.; Harsono, D.; Herczeg, G. J.; Johnstone, D.; Jørgensen, J. K.; van Kempen, T. A.; Lee, J.-E.; Maret, S.; Tafalla, M.; Visser, R.; Wampfler, S. F.</p> <p>2017-09-01</p> <p>Context. Through spectrally unresolved observations of high-J CO transitions, Herschel Photodetector Array Camera and Spectrometer (PACS) has revealed large reservoirs of <span class="hlt">warm</span> (300 K) and hot (700 K) molecular gas around low-mass protostars. The excitation and physical origin of this gas is still not understood. Aims: We aim to shed light on the excitation and origin of the CO ladder observed toward protostars, and on the water abundance in different physical <span class="hlt">components</span> within protostellar systems using spectrally resolved Herschel-HIFI data. Methods: Observations are presented of the highly excited CO line J = 16-15 (Eup/kB = 750 K) with the Herschel Heterodyne Instrument for the Far Infrared (HIFI) toward a sample of 24 low-mass protostellar objects. The sources were selected from the Herschel "Water in Star-forming regions with Herschel" (WISH) and "<span class="hlt">Dust</span>, Ice, and Gas in Time" (DIGIT) key programs. Results: The spectrally resolved line profiles typically show two distinct velocity <span class="hlt">components</span>: a broad Gaussian <span class="hlt">component</span> with an average FWHM of 20 km s-1 containing the bulk of the flux, and a narrower Gaussian <span class="hlt">component</span> with a FWHM of 5 km s-1 that is often offset from the source velocity. Some sources show other velocity <span class="hlt">components</span> such as extremely-high-velocity features or "bullets". All these velocity <span class="hlt">components</span> were first detected in H2O line profiles. The average rotational temperature over the entire profile, as measured from comparison between CO J = 16-15 and 10-9 emission, is 300 K. A radiative-transfer analysis shows that the average H2O/CO column-density ratio is 0.02, suggesting a total H2O abundance of 2 × 10-6, independent of velocity. Conclusions: Two distinct velocity profiles observed in the HIFI line profiles suggest that the high-J CO ladder observed with PACS consists of two excitation <span class="hlt">components</span>. The <span class="hlt">warm</span> PACS <span class="hlt">component</span> (300 K) is associated with the broad HIFI <span class="hlt">component</span>, and the hot PACS <span class="hlt">component</span> (700 K) is associated with the offset HIFI</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ISPAr.XL2..151X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ISPAr.XL2..151X"><span>An automated and integrated framework for <span class="hlt">dust</span> storm detection based on ogc web processing services</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xiao, F.; Shea, G. Y. K.; Wong, M. S.; Campbell, J.</p> <p>2014-11-01</p> <p><span class="hlt">Dust</span> storms are known to have adverse effects on public health. Atmospheric <span class="hlt">dust</span> loading is also one of the major uncertainties in global climatic modelling as it is known to have a significant impact on the radiation budget and atmospheric stability. The complexity of building scientific <span class="hlt">dust</span> storm models is coupled with the scientific computation advancement, ongoing computing platform development, and the development of heterogeneous Earth Observation (EO) networks. It is a challenging task to develop an integrated and automated scheme for <span class="hlt">dust</span> storm detection that combines Geo-Processing frameworks, scientific models and EO data together to enable the <span class="hlt">dust</span> storm detection and tracking processes in a dynamic and timely manner. This study develops an automated and integrated framework for <span class="hlt">dust</span> storm detection and tracking based on the Web Processing Services (WPS) initiated by Open Geospatial Consortium (OGC). The presented WPS framework consists of EO data retrieval <span class="hlt">components</span>, <span class="hlt">dust</span> storm detecting and tracking <span class="hlt">component</span>, and service chain orchestration engine. The EO data processing <span class="hlt">component</span> is implemented based on OPeNDAP standard. The <span class="hlt">dust</span> storm detecting and tracking <span class="hlt">component</span> combines three earth scientific models, which are SBDART model (for computing aerosol optical depth (AOT) of <span class="hlt">dust</span> particles), WRF model (for simulating meteorological parameters) and HYSPLIT model (for simulating the <span class="hlt">dust</span> storm transport processes). The service chain orchestration engine is implemented based on Business Process Execution Language for Web Service (BPEL4WS) using open-source software. The output results, including horizontal and vertical AOT distribution of <span class="hlt">dust</span> particles as well as their transport paths, were represented using KML/XML and displayed in Google Earth. A serious <span class="hlt">dust</span> storm, which occurred over East Asia from 26 to 28 Apr 2012, is used to test the applicability of the proposed WPS framework. Our aim here is to solve a specific instance of a complex EO data</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006cosp...36.2094H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006cosp...36.2094H"><span>Assessment of <span class="hlt">dust</span> aerosol effect on cloud properties over Northwest China using CERES SSF data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Huang, J.; Wang, X.; Wang, T.; Su, J.; Minnis, P.; Lin, B.; Hu, Y.; Yi, Y.</p> <p></p> <p><span class="hlt">Dust</span> aerosols not only have direct effects on the climate through reflection and absorption of the short and long wave radiation but also modify cloud properties such as the number concentration and size of cloud droplets indirect effect and contribute to diabatic heating in the atmosphere that often enhances cloud evaporation and reduces the cloud water path In this study indirect and semi-direct effects of <span class="hlt">dust</span> aerosols are analyzed over eastern Asia using two years June 2002 to June 2004 of CERES Clouds and the Earth s Radiant Energy Budget Scanner and MODIS MODerate Resolution Imaging Spectroradiometer Aqua Edition 1B SSF Single Scanner Footprint data sets The statistical analysis shows evidence for both indirect and semi-direct effect of Asia <span class="hlt">dust</span> aerosols The <span class="hlt">dust</span> appears to reduce the ice cloud effective particle diameter and increase high cloud amount On average ice cloud effective particle diameters of cirrus clouds under <span class="hlt">dust</span> polluted conditions dusty cloud are 11 smaller than those derived from ice clouds in <span class="hlt">dust</span>-free atmospheric environments The water paths of dusty clouds are also considerably smaller than those of <span class="hlt">dust</span>-free clouds <span class="hlt">Dust</span> aerosols could <span class="hlt">warm</span> clouds thereby increasing the evaporation of cloud droplets resulting in reduced cloud water path semi-direct effect The semi-direct effect may be dominated the interaction between <span class="hlt">dust</span> aerosols and clouds over arid and semi-arid areas and partly contribute to reduced precipitation</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA03917&hterms=tornadoes+form&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dtornadoes%2Bform','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA03917&hterms=tornadoes+form&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dtornadoes%2Bform"><span>A <span class="hlt">Dust</span> Devil Making a Streak and Climbing a Crater Wall</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2002-01-01</p> <p>MGS MOC Release No. MOC2-318, 8 August 2002 [figure removed for brevity, see original site] One of the key elements of the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) Extended Mission is to look for and monitor changes taking place on the planet over the course of a second--and, eventually, a third--martian year. MGS is now well into its second Mars year, which will draw to a close in December 2002. Among the changes the MOC has observed are streaks believed to be caused by the passage of <span class="hlt">dust</span> devils. Thousands of MOC images show these streaks, dozens show that they change over time, but far fewer images have actually captured a <span class="hlt">dust</span> devil in the act of creating a streak. At the center right of this image (above left) is a <span class="hlt">dust</span> devil that, on May 21, 2002, was seen climbing the wall of a crater at 4.1oS, 9.5oW. This crater (above right) is in western Terra Meridiani. The <span class="hlt">dust</span> devil was moving toward the northeast (upper right), leaving behind a dark trail where a thin coating of surficial <span class="hlt">dust</span> was removed or disrupted as the <span class="hlt">dust</span> devil advanced. <span class="hlt">Dust</span> devils most commonly form after noon on days when the martian air is still (that is, when there isn't even a faint breeze). On such days, the ground is better able to heat up the air immediately above the surface. As the <span class="hlt">warmed</span> near-surface air begins to rise, it also begins to spin, creating a vortex. The spinning column then moves across the surface and picks up loose <span class="hlt">dust</span> (if any is present). The <span class="hlt">dust</span> makes the vortex visible and gives it a tornado-like appearance. The <span class="hlt">dust</span> devil in this image has a very short, dark shadow cast to the right of the bright column; this shadow is short because the sun was nearly overhead.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUSM.A72B..01S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUSM.A72B..01S"><span>Hygroscopicity of mineral <span class="hlt">dust</span> particles: Roles of chemical mixing state and hygroscopic conversion timescale</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sullivan, R. C.; Moore, M. J.; Petters, M. D.; Laskin, A.; Roberts, G. C.; Kreidenweis, S. M.; Prather, K. A.</p> <p>2009-05-01</p> <p>Our laboratory investigations of mineral <span class="hlt">dust</span> particle hygroscopicity are motivated by field observations of the atmospheric processing of <span class="hlt">dust</span>. During ACE-Asia we observed sulphate and nitrate to be strongly segregated from each other in individual aged Asian <span class="hlt">dust</span> particles. CCN activation curves of pure calcium minerals as proxies for fresh (calcium carbonate) and aged (calcium sulphate, nitrate, chloride) <span class="hlt">dust</span> indicate that this mixing state would cause a large fraction of aged <span class="hlt">dust</span> particles to remain poor <span class="hlt">warm</span> cloud nucleation potential, contrary to previous assumptions. The enrichment of oxalic acid in calcium-rich <span class="hlt">dust</span> particles could have similar effects due to the formation of insoluble calcium oxalate. Soluble calcium nitrate and chloride reaction products are hygroscopic and will transform mineral <span class="hlt">dust</span> into excellent CCN. Generating insoluble mineral particles wet by atomization produced particles with much higher hygroscopicity then when resuspended dry. The atomized particles are likely composed of dissolved residuals and do not properly reflect the chemistry of dry mineral powders. Aerosol flow tube experiments were employed to study the conversion of calcium carbonate into calcium nitrate via heterogeneous reaction with nitric acid, with simultaneous measurements of the reacted particles' chemistry and hygroscopicity. The timescale for this hygroscopic conversion was found to occur on the order of a few hours under tropospheric conditions. This implies that the conversion of non-hygroscopic calcite- containing <span class="hlt">dust</span> into hygroscopic particles will be controlled by the availability of nitric acid, and not by the atmospheric residence time. Results from recent investigations of the effect of secondary coatings on the ice nucleation properties of <span class="hlt">dust</span> particles will also be presented. The cloud formation potential of aged <span class="hlt">dust</span> particles depends on both the quantity and form of the secondary species that have reacted or mixed with the <span class="hlt">dust</span>. These results</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120013322','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120013322"><span>All-Sky Observational Evidence for An Inverse Correlation Between <span class="hlt">Dust</span> Temperature and Emissivity Spectral Index</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Liang, Z.; Fixsen, D. J.; Gold, B.</p> <p>2012-01-01</p> <p>We show that a one-<span class="hlt">component</span> variable-emissivity-spectral-index model (the free- model) provides more physically motivated estimates of <span class="hlt">dust</span> temperature at the Galactic polar caps than one- or two-<span class="hlt">component</span> fixed-emissivity-spectral-index models (fixed- models) for interstellar <span class="hlt">dust</span> thermal emission at far-infrared and millimeter wavelengths. For the comparison we have fit all-sky one-<span class="hlt">component</span> <span class="hlt">dust</span> models with fixed or variable emissivity spectral index to a new and improved version of the 210-channel <span class="hlt">dust</span> spectra from the COBE-FIRAS, the 100-240 micrometer maps from the COBE-DIRBE and the 94 GHz <span class="hlt">dust</span> map from the WMAP. The best model, the free-alpha model, is well constrained by data at 60-3000 GHz over 86 per cent of the total sky area. It predicts <span class="hlt">dust</span> temperature (T(sub <span class="hlt">dust</span>)) to be 13.7-22.7 (plus or minus 1.3) K, the emissivity spectral index (alpha) to be 1.2-3.1 (plus or minus 0.3) and the optical depth (tau) to range 0.6-46 x 10(exp -5) with a 23 per cent uncertainty. Using these estimates, we present all-sky evidence for an inverse correlation between the emissivity spectral index and <span class="hlt">dust</span> temperature, which fits the relation alpha = 1/(delta + omega (raised dot) T(sub <span class="hlt">dust</span>) with delta = -.0.510 plus or minus 0.011 and omega = 0.059 plus or minus 0.001. This best model will be useful to cosmic microwave background experiments for removing foreground <span class="hlt">dust</span> contamination and it can serve as an all-sky extended-frequency reference for future higher resolution <span class="hlt">dust</span> models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018PhPl...25e3706S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018PhPl...25e3706S"><span>Drift <span class="hlt">dust</span> acoustic soliton in the presence of field-aligned sheared flow and nonextensivity effects</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shah, AttaUllah; Mushtaq, A.; Farooq, M.; Khan, Aurangzeb; Aman-ur-Rehman</p> <p>2018-05-01</p> <p>Low frequency electrostatic <span class="hlt">dust</span> drift acoustic (DDA) waves are studied in an inhomogeneous <span class="hlt">dust</span> magnetoplasma comprised of <span class="hlt">dust</span> <span class="hlt">components</span> of opposite polarity, Boltzmannian ions, and nonextensive distributed electrons. The magnetic-field-aligned <span class="hlt">dust</span> sheared flow drives the electrostatic drift waves in the presence of ions and electrons. The sheared flow decreases or increases the frequency of the DDA wave, mostly depending on its polarity. The conditions of instability for this mode, with nonextensivity and <span class="hlt">dust</span> streaming effects, are discussed. The nonlinear dynamics is then investigated for the DDA wave by deriving the Koeteweg-deVries (KdV) nonlinear equation. The KdV equation yields an electrostatic structure in the form of a DDA soliton. The relevancy of the work to laboratory four <span class="hlt">component</span> dusty plasmas is illustrated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22167116-asteroid-belts-debris-disk-twins-vega-fomalhaut','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22167116-asteroid-belts-debris-disk-twins-vega-fomalhaut"><span>ASTEROID BELTS IN DEBRIS DISK TWINS: VEGA AND FOMALHAUT</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Su, Kate Y. L.; Rieke, George H.; Misselt, Karl A.</p> <p>2013-02-15</p> <p>Vega and Fomalhaut are similar in terms of mass, ages, and global debris disk properties; therefore, they are often referred to as 'debris disk twins'. We present Spitzer 10-35 {mu}m spectroscopic data centered at both stars and identify <span class="hlt">warm</span>, unresolved excess emission in the close vicinity of Vega for the first time. The properties of the <span class="hlt">warm</span> excess in Vega are further characterized with ancillary photometry in the mid-infrared and resolved images in the far-infrared and submillimeter wavelengths. The Vega <span class="hlt">warm</span> excess shares many similar properties with the one found around Fomalhaut. The emission shortward of {approx}30 {mu}m from bothmore » <span class="hlt">warm</span> <span class="hlt">components</span> is well described as a blackbody emission of {approx}170 K. Interestingly, two other systems, {epsilon} Eri and HR 8799, also show such an unresolved <span class="hlt">warm</span> <span class="hlt">dust</span> using the same approach. These <span class="hlt">warm</span> <span class="hlt">components</span> may be analogous to the solar system's zodiacal <span class="hlt">dust</span> cloud, but of far greater mass (fractional luminosity of {approx}10{sup -5} to 10{sup -6} compared to 10{sup -8} to 10{sup -7}). The <span class="hlt">dust</span> temperature and tentative detections in the submillimeter suggest that the <span class="hlt">warm</span> excess arises from <span class="hlt">dust</span> associated with a planetesimal ring located near the water-frost line and presumably created by processes occurring at similar locations in other debris systems as well. We also review the properties of the 2 {mu}m hot excess around Vega and Fomalhaut, showing that the <span class="hlt">dust</span> responsible for the hot excess is not spatially associated with the <span class="hlt">dust</span> we detected in the <span class="hlt">warm</span> belt. We suggest it may arise from hot nano grains trapped in the magnetic field of the star. Finally, the separation between the <span class="hlt">warm</span> and cold belt is rather large with an orbital ratio {approx}>10 in all four systems. In light of the current upper limits on the masses of planetary objects and the large gap, we discuss the possible implications for their underlying planetary architecture and suggest that multiple, low-mass planets likely reside</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008sptz.prop50267C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008sptz.prop50267C"><span>Characterizing the <span class="hlt">Dust</span>-Correlated Anomalous Emission in LDN 1622</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cleary, Kieran; Casassus, Simon; Dickinson, Clive; Lawrence, Charles; Sakon, Itsuki</p> <p>2008-03-01</p> <p>The search for '<span class="hlt">dust</span>-correlated microwave emission' was started by the surprising excess correlation of COBE-DMR maps, at 31.5, 53 and 91GHz, with DIRBE <span class="hlt">dust</span> emission at 140 microns. It was first thought to be Galactic free-free emission from the <span class="hlt">Warm</span> Ionized Medium (WIM). However, Leitch et al. (1997) ruled out a link with free-free by comparing with Halpha templates and first confirmed the anomalous nature of this emission. Since then, this emission has been detected by a number of experiments in the frequency range 5-60 GHz. The most popular explanation is emission from ultra-small spinning <span class="hlt">dust</span> grains (first postulated by Erickson, 1957), which is expected to have a spectrum that is highly peaked at about 20 GHz. Spinning <span class="hlt">dust</span> models appear to be broadly consistent with microwave data at high latitudes, but the data have not been conclusive, mainly due to the difficulty of foreground separation in CMB data. LDN 1622 is a dark cloud that lies within the Orion East molecular cloud at a distance of 120 pc. Recent cm-wave observations, in combination with WMAP data, have verified the detection of anomalous <span class="hlt">dust</span>-correlated emission in LDN 1622. This mid-IR-cm correlation in LDN 1622 is currently the only observational evidence that very small grains VSG emit at GHz frequencies. We propose a programme of spectroscopic observations of LDN 1622 with Spitzer IRS to address the following questions: (i) Are the IRAS 12 and 25 microns bands tracing VSG emission in LDN 1622? (ii) What Mid-IR features and continuum bands best correlate with the cm-wave emission? and (iii) How do the <span class="hlt">dust</span> properties vary with the cm-wave emission? These questions have important implications for high-sensitivity CMB experiments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014A%26A...565A..29L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014A%26A...565A..29L"><span><span class="hlt">Warm</span> gas towards young stellar objects in Corona Australis. Herschel/PACS observations from the DIGIT key programme</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lindberg, Johan E.; Jørgensen, Jes K.; Green, Joel D.; Herczeg, Gregory J.; Dionatos, Odysseas; Evans, Neal J.; Karska, Agata; Wampfler, Susanne F.</p> <p>2014-05-01</p> <p>Context. The effects of external irradiation on the chemistry and physics in the protostellar envelope around low-mass young stellar objects are poorly understood. The Corona Australis star-forming region contains the R CrA dark cloud, comprising several low-mass protostellar cores irradiated by an intermediate-mass young star. Aims: We study the effects of the irradiation coming from the young luminous Herbig Be star R CrA on the <span class="hlt">warm</span> gas and <span class="hlt">dust</span> in a group of low-mass young stellar objects. Methods: Herschel/PACS far-infrared datacubes of two low-mass star-forming regions in the R CrA dark cloud are presented. The distributions of CO, OH, H2O, [C ii], [O i], and continuum emission are investigated. We have developed a deconvolution algorithm which we use to deconvolve the maps, separating the point-source emission from the extended emission. We also construct rotational diagrams of the molecular species. Results: By deconvolution of the Herschel data, we find large-scale (several thousand AU) <span class="hlt">dust</span> continuum and spectral line emission not associated with the point sources. Similar rotational temperatures are found for the <span class="hlt">warm</span> CO (282 ± 4 K), hot CO (890 ± 84 K), OH (79 ± 4 K), and H2O (197 ± 7 K) emission in the point sources and the extended emission. The rotational temperatures are also similar to those found in other more isolated cores. The extended <span class="hlt">dust</span> continuum emission is found in two ridges similar in extent and temperature to molecular millimetre emission, indicative of external heating from the Herbig Be star R CrA. Conclusions: Our results show that nearby luminous stars do not increase the molecular excitation temperatures of the <span class="hlt">warm</span> gas around young stellar objects (YSOs). However, the emission from photodissociation products of H2O, such as OH and O, is enhanced in the <span class="hlt">warm</span> gas associated with these protostars and their surroundings compared to similar objects not subjected to external irradiation. Table 9 and appendices are available in</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014PlST...16..433K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PlST...16..433K"><span>Inertia-Centric Stability Analysis of a Planar Uniform <span class="hlt">Dust</span> Molecular Cloud with Weak Neutral-Charged <span class="hlt">Dust</span> Frictional Coupling</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>K. Karmakar, P.; Borah, B.</p> <p>2014-05-01</p> <p>This paper adopts an inertia-centric evolutionary model to study the excitation mechanism of new gravito-electrostatic eigenmode structures in a one-dimensional (1-D) planar self-gravitating <span class="hlt">dust</span> molecular cloud (DMC) on the Jeans scale. A quasi-neutral multi-fluid consisting of <span class="hlt">warm</span> electrons, <span class="hlt">warm</span> ions, neutral gas and identical inertial cold <span class="hlt">dust</span> grains with partial ionization is considered. The grain-charge is assumed not to vary at the fluctuation evolution time scale. The neutral gas particles form the background, which is weakly coupled with the collapsing grainy plasma mass. The gravitational decoupling of the background neutral particles is justifiable for a higher inertial mass of the grains with higher neutral population density so that the Jeans mode frequency becomes reasonably large. Its physical basis is the Jeans assumption of a self-gravitating uniform medium adopted for fiducially analytical simplification by neglecting the zero-order field. So, the equilibrium is justifiably treated initially as “homogeneous”. The efficacious inertial role of the thermal species amidst weak collisions of the neutral-charged grains is taken into account. A standard multiscale technique over the gravito-electrostatic equilibrium yields a unique pair of Korteweg-de Vries (KdV) equations. It is integrated numerically by the fourth-order Runge-Kutta method with multi-parameter variation for exact shape analyses. Interestingly, the model is conducive for the propagation of new conservative solitary spectral patterns. Their basic physics, parametric features and unique characteristics are discussed. The results go qualitatively in good correspondence with the earlier observations made by others. Tentative applications relevant to space and astrophysical environments are concisely highlighted.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1394428-enhanced-decomposition-stable-soil-organic-carbon-microbial-catabolic-potentials-long-term-field-warming','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1394428-enhanced-decomposition-stable-soil-organic-carbon-microbial-catabolic-potentials-long-term-field-warming"><span>Enhanced decomposition of stable soil organic carbon and microbial catabolic potentials by long-term field <span class="hlt">warming</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Feng, Wenting; Liang, Junyi; Hale, Lauren E.; ...</p> <p>2017-06-09</p> <p>Quantifying soil organic carbon (SOC) decomposition under <span class="hlt">warming</span> is critical to predict carbon–climate feedbacks. According to the substrate regulating principle, SOC decomposition would decrease as labile SOC declines under field <span class="hlt">warming</span>, but observations of SOC decomposition under <span class="hlt">warming</span> do not always support this prediction. This discrepancy could result from varying changes in SOC <span class="hlt">components</span> and soil microbial communities under <span class="hlt">warming</span>. This study aimed to determine the decomposition of SOC <span class="hlt">components</span> with different turnover times after subjected to long-term field <span class="hlt">warming</span> and/or root exclusion to limit C input, and to test whether SOC decomposition is driven by substrate lability under <span class="hlt">warming</span>.more » Taking advantage of a 12-year field <span class="hlt">warming</span> experiment in a prairie, we assessed the decomposition of SOC <span class="hlt">components</span> by incubating soils from control and <span class="hlt">warmed</span> plots, with and without root exclusion for 3 years. We assayed SOC decomposition from these incubations by combining inverse modeling and microbial functional genes during decomposition with a metagenomic technique (GeoChip). The decomposition of SOC <span class="hlt">components</span> with turnover times of years and decades, which contributed to 95% of total cumulative CO 2 respiration, was greater in soils from <span class="hlt">warmed</span> plots. But the decomposition of labile SOC was similar in <span class="hlt">warmed</span> plots compared to the control. The diversity of C-degradation microbial genes generally declined with time during the incubation in all treatments, suggesting shifts of microbial functional groups as substrate composition was changing. Compared to the control, soils from <span class="hlt">warmed</span> plots showed significant increase in the signal intensities of microbial genes involved in degrading complex organic compounds, implying enhanced potential abilities of microbial catabolism. These are likely responsible for accelerated decomposition of SOC <span class="hlt">components</span> with slow turnover rates. Overall, the shifted microbial community induced by long-term <span class="hlt">warming</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1394428','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1394428"><span>Enhanced decomposition of stable soil organic carbon and microbial catabolic potentials by long-term field <span class="hlt">warming</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Feng, Wenting; Liang, Junyi; Hale, Lauren E.</p> <p></p> <p>Quantifying soil organic carbon (SOC) decomposition under <span class="hlt">warming</span> is critical to predict carbon–climate feedbacks. According to the substrate regulating principle, SOC decomposition would decrease as labile SOC declines under field <span class="hlt">warming</span>, but observations of SOC decomposition under <span class="hlt">warming</span> do not always support this prediction. This discrepancy could result from varying changes in SOC <span class="hlt">components</span> and soil microbial communities under <span class="hlt">warming</span>. This study aimed to determine the decomposition of SOC <span class="hlt">components</span> with different turnover times after subjected to long-term field <span class="hlt">warming</span> and/or root exclusion to limit C input, and to test whether SOC decomposition is driven by substrate lability under <span class="hlt">warming</span>.more » Taking advantage of a 12-year field <span class="hlt">warming</span> experiment in a prairie, we assessed the decomposition of SOC <span class="hlt">components</span> by incubating soils from control and <span class="hlt">warmed</span> plots, with and without root exclusion for 3 years. We assayed SOC decomposition from these incubations by combining inverse modeling and microbial functional genes during decomposition with a metagenomic technique (GeoChip). The decomposition of SOC <span class="hlt">components</span> with turnover times of years and decades, which contributed to 95% of total cumulative CO 2 respiration, was greater in soils from <span class="hlt">warmed</span> plots. But the decomposition of labile SOC was similar in <span class="hlt">warmed</span> plots compared to the control. The diversity of C-degradation microbial genes generally declined with time during the incubation in all treatments, suggesting shifts of microbial functional groups as substrate composition was changing. Compared to the control, soils from <span class="hlt">warmed</span> plots showed significant increase in the signal intensities of microbial genes involved in degrading complex organic compounds, implying enhanced potential abilities of microbial catabolism. These are likely responsible for accelerated decomposition of SOC <span class="hlt">components</span> with slow turnover rates. Overall, the shifted microbial community induced by long-term <span class="hlt">warming</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28597589','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28597589"><span>Enhanced decomposition of stable soil organic carbon and microbial catabolic potentials by long-term field <span class="hlt">warming</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Feng, Wenting; Liang, Junyi; Hale, Lauren E; Jung, Chang Gyo; Chen, Ji; Zhou, Jizhong; Xu, Minggang; Yuan, Mengting; Wu, Liyou; Bracho, Rosvel; Pegoraro, Elaine; Schuur, Edward A G; Luo, Yiqi</p> <p>2017-11-01</p> <p>Quantifying soil organic carbon (SOC) decomposition under <span class="hlt">warming</span> is critical to predict carbon-climate feedbacks. According to the substrate regulating principle, SOC decomposition would decrease as labile SOC declines under field <span class="hlt">warming</span>, but observations of SOC decomposition under <span class="hlt">warming</span> do not always support this prediction. This discrepancy could result from varying changes in SOC <span class="hlt">components</span> and soil microbial communities under <span class="hlt">warming</span>. This study aimed to determine the decomposition of SOC <span class="hlt">components</span> with different turnover times after subjected to long-term field <span class="hlt">warming</span> and/or root exclusion to limit C input, and to test whether SOC decomposition is driven by substrate lability under <span class="hlt">warming</span>. Taking advantage of a 12-year field <span class="hlt">warming</span> experiment in a prairie, we assessed the decomposition of SOC <span class="hlt">components</span> by incubating soils from control and <span class="hlt">warmed</span> plots, with and without root exclusion for 3 years. We assayed SOC decomposition from these incubations by combining inverse modeling and microbial functional genes during decomposition with a metagenomic technique (GeoChip). The decomposition of SOC <span class="hlt">components</span> with turnover times of years and decades, which contributed to 95% of total cumulative CO 2 respiration, was greater in soils from <span class="hlt">warmed</span> plots. But the decomposition of labile SOC was similar in <span class="hlt">warmed</span> plots compared to the control. The diversity of C-degradation microbial genes generally declined with time during the incubation in all treatments, suggesting shifts of microbial functional groups as substrate composition was changing. Compared to the control, soils from <span class="hlt">warmed</span> plots showed significant increase in the signal intensities of microbial genes involved in degrading complex organic compounds, implying enhanced potential abilities of microbial catabolism. These are likely responsible for accelerated decomposition of SOC <span class="hlt">components</span> with slow turnover rates. Overall, the shifted microbial community induced by long-term <span class="hlt">warming</span> accelerates the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29148823','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29148823"><span>Space <span class="hlt">Dust</span> Collisions as a Planetary Escape Mechanism.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Berera, Arjun</p> <p>2017-12-01</p> <p>It is observed that hypervelocity space <span class="hlt">dust</span>, which is continuously bombarding Earth, creates immense momentum flows in the atmosphere. Some of this fast space <span class="hlt">dust</span> inevitably will interact with the atmospheric system, transferring energy and moving particles around, with various possible consequences. This paper examines, with supporting estimates, the possibility that by way of collisions the Earth-grazing <span class="hlt">component</span> of space <span class="hlt">dust</span> can facilitate planetary escape of atmospheric particles, whether they are atoms and molecules that form the atmosphere or larger-sized particles. An interesting outcome of this collision scenario is that a variety of particles that contain telltale signs of Earth's organic story, including microbial life and life-essential molecules, may be "afloat" in Earth's atmosphere. The present study assesses the capability of this space <span class="hlt">dust</span> collision mechanism to propel some of these biological constituents into space. Key Words: Hypervelocity space <span class="hlt">dust</span>-Collision-Planetary escape-Atmospheric constituents-Microbial life. Astrobiology 17, 1274-1282.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24620406','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24620406"><span>Contribution of <span class="hlt">dust</span> storms to PM10 levels in an urban arid environment.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Krasnov, Helena; Katra, Itzhak; Koutrakis, Petros; Friger, Michael D</p> <p>2014-01-01</p> <p>Quantitative information on the contribution of <span class="hlt">dust</span> storms to atmospheric PM10 (particulate matter with an aerodynamic diameter < or = 10 microm) levels is still lacking, especially in urban environments with close proximity to <span class="hlt">dust</span> sources. The main objective of this study was to quantify the contribution of <span class="hlt">dust</span> storms to PM10 concentrations in a desert urban center, the city of Beer-Sheva, Negev, Israel, during the period of 2001-2012. Toward this end, a background value based on the "<span class="hlt">dust</span>-free" season was used as a threshold value to identify potentially "<span class="hlt">dust</span> days." Subsequently, the net contribution of <span class="hlt">dust</span> storms to PM10 was assessed. During the study period, daily PM10 concentrations ranged from 6 to over 2000 microg/m3. In each year, over 10% of the daily concentrations exceeded the calculated threshold (BVt) of 71 microg/m3. An average daily net contribution of <span class="hlt">dust</span> to PM10 of 122 microg/m3 was calculated for the entire study period based on this background value. Furthermore, a <span class="hlt">dust</span> storm intensity parameter (Ai) was used to analyze several storms with very high PM10 contributions (hourly averages of 1000-5197 microg/m3). This analysis revealed that the strongest storms occurred mainly in the last 3 yr of the study. Finally, these findings indicate that this arid urban environment experiences high PM10 levels whose origin lies in both local and regional <span class="hlt">dust</span> events. The findings indicate that over time, the urban arid environment experiences high PM10 levels whose origin lies in local and regional <span class="hlt">dust</span> events. It was noticed that the strongest storms have occurred mainly in the last 3 yr. It is believed that environmental changes such as global <span class="hlt">warming</span> and desertification may lead to an increased air pollution and risk exposure to human health.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24593535','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24593535"><span>X-ray spectroscopy of <span class="hlt">warm</span> and hot electron <span class="hlt">components</span> in the CAPRICE source plasma at EIS testbench at GSI.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mascali, D; Celona, L; Maimone, F; Maeder, J; Castro, G; Romano, F P; Musumarra, A; Altana, C; Caliri, C; Torrisi, G; Neri, L; Gammino, S; Tinschert, K; Spaedtke, K P; Rossbach, J; Lang, R; Ciavola, G</p> <p>2014-02-01</p> <p>An experimental campaign aiming to detect X radiation emitted by the plasma of the CAPRICE source - operating at GSI, Darmstadt - has been carried out. Two different detectors (a SDD - Silicon Drift Detector and a HpGe - hyper-pure Germanium detector) have been used to characterize the <span class="hlt">warm</span> (2-30 keV) and hot (30-500 keV) electrons in the plasma, collecting the emission intensity and the energy spectra for different pumping wave frequencies and then correlating them with the CSD of the extracted beam measured by means of a bending magnet. A plasma emissivity model has been used to extract the plasma density along the cone of sight of the SDD and HpGe detectors, which have been placed beyond specific collimators developed on purpose. Results show that the tuning of the pumping frequency considerably modifies the plasma density especially in the <span class="hlt">warm</span> electron population domain, which is the <span class="hlt">component</span> responsible for ionization processes: a strong variation of the plasma density near axis region has been detected. Potential correlations with the charge state distribution in the plasma are explored.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28725442','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28725442"><span>Identification of <span class="hlt">dust</span> storm origin in South -West of Iran.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Broomandi, Parya; Dabir, Bahram; Bonakdarpour, Babak; Rashidi, Yousef</p> <p>2017-01-01</p> <p>Deserts are the main sources of emitted <span class="hlt">dust</span>, and are highly responsive to wind erosion. Low content of soil moisture and lack of vegetation cover lead to fine particle's release. One of the semi-arid bare lands in Iran, located in the South-West of Iran in Khoozestan province, was selected to investigate Sand and <span class="hlt">Dust</span> storm potential. This paper focused on the metrological parameters of the sampling site, their changes and the relationship between these changes and <span class="hlt">dust</span> storm occurrence, estimation of Reconaissance Drought Index, the Atterberg limits of soil samples and their relation with soil erosion ability, the chemical composition, size distribution of soil and airborne <span class="hlt">dust</span> samples, and estimation of vertical mass flux by COMSALT through considering the effect of saffman force and interparticle cohesion forces during <span class="hlt">warm</span> period (April-September) in 2010. The chemical compositions are measured with X-ray fluorescence, Atomic absorption spectrophotometer and X-ray diffraction. The particle size distribution analysis was conducted by using Laser particle size and sieve techniques. There was a strong negative correlation between <span class="hlt">dust</span> storm occurrence and annual and seasonal rainfall and relative humidity. Positive strong correlation between annual and seasonal maximum temperature and <span class="hlt">dust</span> storm frequency was seen. Estimation of RDI st in the studied period showed an extremely dry condition. Using the results of particle size distribution and soil consistency, the weak structure of soil was represented. X-ray diffraction analyses of soil and <span class="hlt">dust</span> samples showed that soil mineralogy was dominated mainly by Quartz and calcite. X-ray fluorescence analyses of samples indicated that the most important major oxide compositions of the soil and airborne <span class="hlt">dust</span> samples were SiO 2 , Al 2 O 3 , CaO, MgO, Na 2 O, and Fe 2 O 3 , demonstrating similar percentages for soil and <span class="hlt">dust</span> samples. Estimation of Enrichment Factors for all studied trace elements in soil samples showed Br</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70023104','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70023104"><span>Techniques for identifying <span class="hlt">dust</span> devils in mars pathfinder images</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Metzger, S.M.; Carr, J.R.; Johnson, J. R.; Parker, T.J.; Lemmon, M.T.</p> <p>2000-01-01</p> <p>Image processing methods used to identify and enhance <span class="hlt">dust</span> devil features imaged by IMP (Imager for Mars Pathfinder) are reviewed. Spectral differences, visible red minus visible blue, were used for initial <span class="hlt">dust</span> devil searches, driven by the observation that Martian <span class="hlt">dust</span> has high red and low blue reflectance. The Martian sky proved to be more heavily <span class="hlt">dust</span>-laden than pre-Pathfinder predictions, based on analysis of images from the Hubble Space Telescope. As a result, these initial spectral difference methods failed to contrast <span class="hlt">dust</span> devils with background <span class="hlt">dust</span> haze. Imager artifacts (<span class="hlt">dust</span> motes on the camera lens, flat-field effects caused by imperfections in the CCD, and projection onto a flat sensor plane by a convex lens) further impeded the ability to resolve subtle <span class="hlt">dust</span> devil features. Consequently, reference images containing sky with a minimal horizon were first subtracted from each spectral filter image to remove camera artifacts and reduce the background <span class="hlt">dust</span> haze signal. Once the sky-flat preprocessing step was completed, the red-minus-blue spectral difference scheme was attempted again. <span class="hlt">Dust</span> devils then were successfully identified as bright plumes. False-color ratios using calibrated IMP images were found useful for visualizing <span class="hlt">dust</span> plumes, verifying initial discoveries as vortex-like features. Enhancement of monochromatic (especially blue filter) images revealed <span class="hlt">dust</span> devils as silhouettes against brighter background sky. Experiments with principal <span class="hlt">components</span> transformation identified <span class="hlt">dust</span> devils in raw, uncalibrated IMP images and further showed relative movement of <span class="hlt">dust</span> devils across the Martian surface. A variety of methods therefore served qualitative and quantitative goals for <span class="hlt">dust</span> plume identification and analysis in an environment where such features are obscure.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_14 --> <div id="page_15" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="281"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009ApJ...699.1822G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009ApJ...699.1822G"><span>Revealing the Structure of a Pre-Transitional Disk: The Case of the Herbig F Star SAO 206462 (HD 135344B)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Grady, C. A.; Schneider, G.; Sitko, M. L.; Williger, G. M.; Hamaguchi, K.; Brittain, S. D.; Ablordeppey, K.; Apai, D.; Beerman, L.; Carpenter, W. J.; Collins, K. A.; Fukagawa, M.; Hammel, H. B.; Henning, Th.; Hines, D.; Kimes, R.; Lynch, D. K.; Ménard, F.; Pearson, R.; Russell, R. W.; Silverstone, M.; Smith, P. S.; Troutman, M.; Wilner, D.; Woodgate, B.; Clampin, M.</p> <p>2009-07-01</p> <p>SAO 206462 (HD 135344B) has previously been identified as a Herbig F star with a circumstellar disk with a dip in its infrared excess near 10 μm. In combination with a low accretion rate estimated from Br γ, it may represent a gapped, but otherwise primordial or "pre-transitional" disk. We test this hypothesis with Hubble Space Telescope coronagraphic imagery, FUV spectroscopy and imagery and archival X-ray data, and spectral energy distribution (SED) modeling constrained by the observed system inclination, disk outer radius, and outer disk radial surface brightness (SB) profile using the Whitney Monte Carlo Radiative Transfer Code. The essentially face-on (i lsim 20°) disk is detected in scattered light from 0farcs4 to 1farcs15 (56-160 AU), with a steep (r -9.6) radial SB profile from 0farcs6 to 0farcs93. Fitting the SB data requires a concave upward or anti-flared outer disk, indicating substantial <span class="hlt">dust</span> grain growth and settling by 8 ± 4 Myr. The <span class="hlt">warm</span> <span class="hlt">dust</span> <span class="hlt">component</span> is significantly variable in near to mid-IR excess and in temperature. At its warmest, it appears confined to a narrow belt from 0.08 to 0.2 AU. The steep SED for this <span class="hlt">dust</span> <span class="hlt">component</span> is consistent with grains with a<= 2.5 μm. For cosmic carbon to silicate <span class="hlt">dust</span> composition, conspicuous 10 μm silicate emission would be expected and is not observed. This may indicate an elevated carbon to silicate ratio for the <span class="hlt">warm</span> <span class="hlt">dust</span>, which is not required to fit the outer disk. At its coolest, the <span class="hlt">warm</span> <span class="hlt">dust</span> can be fit with a disk from 0.14 to 0.31 AU, but with a higher inclination than either the outer disk or the gaseous disk, providing confirmation of the high inclination inferred from mid-IR interferometry. In tandem, the compositional and inclination difference between the <span class="hlt">warm</span> <span class="hlt">dust</span> and the outer <span class="hlt">dust</span> disk suggests that the <span class="hlt">warm</span> <span class="hlt">dust</span> may be of second-generation origin, rather than a remnant of a primordial disk <span class="hlt">component</span>. With its near face-on inclination, SAO 206462's disk is a prime location for planet</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29140634','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29140634"><span>Combustibility Determination for Cotton Gin <span class="hlt">Dust</span> and Almond Huller <span class="hlt">Dust</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hughs, Sidney E; Wakelyn, Phillip J</p> <p>2017-04-26</p> <p>It has been documented that some <span class="hlt">dusts</span> generated while processing agricultural products, such as grain and sugar, can constitute combustible <span class="hlt">dust</span> hazards. After a catastrophic <span class="hlt">dust</span> explosion in a sugar refinery in 2008, the Occupational Safety and Health Administration (OSHA) initiated action to develop a mandatory standard to comprehensively address the fire and explosion hazards of combustible <span class="hlt">dusts</span>. Cotton fiber and related materials from cotton ginning, in loose form, can support smoldering combustion if ignited by an outside source. However, <span class="hlt">dust</span> fires and other more hazardous events, such as <span class="hlt">dust</span> explosions, are unknown in the cotton ginning industry. <span class="hlt">Dust</span> material that accumulates inside cotton gins and almond huller plants during normal processing was collected for testing to determine combustibility. Cotton gin <span class="hlt">dust</span> is composed of greater than 50% inert inorganic mineral <span class="hlt">dust</span> (ash content), while almond huller <span class="hlt">dust</span> is composed of at least 7% inert inorganic material. Inorganic mineral <span class="hlt">dust</span> is not a combustible <span class="hlt">dust</span>. The collected samples of cotton gin <span class="hlt">dust</span> and almond huller <span class="hlt">dust</span> were sieved to a known particle size range for testing to determine combustibility potential. Combustibility testing was conducted on the cotton gin <span class="hlt">dust</span> and almond huller <span class="hlt">dust</span> samples using the UN test for combustibility suggested in NFPA 652.. This testing indicated that neither the cotton gin <span class="hlt">dust</span> nor the almond huller <span class="hlt">dust</span> should be considered combustible <span class="hlt">dusts</span> (i.e., not a Division 4.1 flammable hazard per 49 CFR 173.124). Copyright© by the American Society of Agricultural Engineers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018AtmEn.182..225T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018AtmEn.182..225T"><span>Temporal and spatial characteristics of <span class="hlt">dust</span> devils and their contribution to the aerosol budget in East Asia-An analysis using a new parameterization scheme for <span class="hlt">dust</span> devils</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tang, Yaoguo; Han, Yongxiang; Liu, Zhaohuan</p> <p>2018-06-01</p> <p><span class="hlt">Dust</span> aerosols are the main aerosol <span class="hlt">components</span> of the atmosphere that affect climate change, but the contribution of <span class="hlt">dust</span> devils to the atmospheric <span class="hlt">dust</span> aerosol budget is uncertain. In this study, a new parameterization scheme for <span class="hlt">dust</span> devils was established and coupled with WRF-Chem, and the diurnal and monthly variations and the contribution of <span class="hlt">dust</span> devils to the atmospheric <span class="hlt">dust</span> aerosol budget in East Asia was simulated. The results show that 1) both the diurnal and monthly variations in <span class="hlt">dust</span> devil emissions in East Asia had unimodal distributions, with peaks in the afternoon and the summer that were similar to the observations; 2) the simulated <span class="hlt">dust</span> devils occurred frequently in deserts, including the Gobi. The distributed area and the intensity center of the <span class="hlt">dust</span> devil moved from east to west during the day; 3) the ratio between the availability of convective buoyancy relative to the frictional dissipation was the main factor that limited the presence of <span class="hlt">dust</span> devils. The position of the <span class="hlt">dust</span> devil formation, the surface temperature, and the boundary layer height determined the <span class="hlt">dust</span> devil intensity; 4) the contribution of <span class="hlt">dust</span> devils to atmospheric <span class="hlt">dust</span> aerosols determined in East Asia was 30.4 ± 13%, thereby suggesting that <span class="hlt">dust</span> devils contribute significantly to the total amount of atmospheric <span class="hlt">dust</span> aerosols. Although the new parameterization scheme for <span class="hlt">dust</span> devils was rough, it was helpful for understanding the distribution of <span class="hlt">dust</span> devils and their contribution to the <span class="hlt">dust</span> aerosol budget.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20160006557','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20160006557"><span>Electrodynamic <span class="hlt">Dust</span> Shield for Space Applications</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mackey, Paul J.; Johansen, Michael R.; Olsen, Robert C.; Raines, Matthew G.; Phillips, James R., III; Cox, Rachel E.; Hogue, Michael D.; Pollard, Jacob R. S.; Calle, Carlos I.</p> <p>2016-01-01</p> <p><span class="hlt">Dust</span> mitigation technology has been highlighted by NASA and the International Space Exploration Coordination Group (ISECG) as a Global Exploration Roadmap (GER) critical technology need in order to reduce life cycle cost and risk, and increase the probability of mission success. The Electrostatics and Surface Physics Lab in Swamp Works at the Kennedy Space Center has developed an Electrodynamic <span class="hlt">Dust</span> Shield (EDS) to remove <span class="hlt">dust</span> from multiple surfaces, including glass shields and thermal radiators. Further development is underway to improve the operation and reliability of the EDS as well as to perform material and <span class="hlt">component</span> testing outside of the International Space Station (ISS) on the Materials on International Space Station Experiment (MISSE). This experiment is designed to verify that the EDS can withstand the harsh environment of space and will look to closely replicate the solar environment experienced on the Moon.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20110007787&hterms=Influence+clouds+climate&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DInfluence%2Bclouds%2Bclimate','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20110007787&hterms=Influence+clouds+climate&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DInfluence%2Bclouds%2Bclimate"><span>Premonsoon Aerosol Characterization and Radiative Effects Over the Indo-Gangetic Plains: Implications for Regional Climate <span class="hlt">Warming</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gautam, Ritesh; Hsu, N. Christina; Lau, K.-M.</p> <p>2010-01-01</p> <p>The Himalayas have a profound effect on the South Asian climate and the regional hydrological cycle, as it forms a barrier for the strong monsoon winds and serves as an elevated heat source, thus controlling the onset and distribution of precipitation during the Indian summer monsoon. Recent studies have suggested that radiative heating by absorbing aerosols, such as <span class="hlt">dust</span> and black carbon over the Indo-Gangetic Plains (IGP) and slopes of the Himalayas, may significantly accelerate the seasonal <span class="hlt">warming</span> of the Hindu Kush-Himalayas-Tibetan Plateau (HKHT) and influence the subsequent evolution of the summer monsoon. This paper presents a detailed characterization of aerosols over the IGP and their radiative effects during the premonsoon season (April-May-June) when <span class="hlt">dust</span> transport constitutes the bulk of the regional aerosol loading, using ground radiometric and spaceborne observations. During the <span class="hlt">dust</span>-laden period, there is a strong response of surface shortwave flux to aerosol absorption indicated by the diurnally averaged forcing efficiency of -70 W/sq m per unit optical depth. The simulated aerosol single-scattering albedo, constrained by surface flux and aerosol measurements, is estimated to be 0.89+/- 0.01 (at approx.550 nm) with diurnal mean surface and top-of-atmosphere forcing values ranging from -11 to -79.8 W/sq m and +1.4 to +12 W/sq m, respectively, for the premonsoon period. The model-simulated solar heating rate profile peaks in the lower troposphere with enhanced heating penetrating into the middle troposphere (5-6 km), caused by vertically extended aerosols over the IGP with peak altitude of approx.5 km as indicated by spaceborne Cloud-Aerosol Lidar with Orthogonal Polarization observations. On a long-term climate scale, our analysis, on the basis of microwave satellite measurements of tropospheric temperatures from 1979 to 2007, indicates accelerated annual mean <span class="hlt">warming</span> rates found over the Himalayan-Hindu Kush region (0.21 C/decade+/-0.08 C</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.P32A..08C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.P32A..08C"><span>Lunar Airborne <span class="hlt">Dust</span> Toxicity Hazard Assessments (Invited)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cooper, B. L.; McKay, D. S.; Taylor, L. A.; Wallace, W. T.; James, J.; Riofrio, L.; Gonzalez, C. P.</p> <p>2009-12-01</p> <p>The Lunar Airborne <span class="hlt">Dust</span> Toxicity Assessment Group (LADTAG) is developing data to set the permissible limits for human exposure to lunar <span class="hlt">dust</span>. This standard will guide the design of airlocks and ports for EVA, as well as the requirements for filtering and monitoring the atmosphere in habitable vehicles, rovers and other modules. LADTAG’s recommendation for permissible exposure limits will be delivered to the Constellation Program in late 2010. The current worst-case exposure limit of 0.05 mg/m3, estimated by LADTAG in 2006, reflects the concern that lunar <span class="hlt">dust</span> may be as toxic as quartz <span class="hlt">dust</span>. Freshly-ground quartz is known to be more toxic than un-ground quartz <span class="hlt">dust</span>. Our research has shown that the surfaces of lunar soil grains can be more readily activated by grinding than quartz. Activation was measured by the amount of free radicals generated—activated simulants generate Reactive Oxygen Species (ROS) i.e., production of hydroxyl free radicals. Of the various influences in the lunar environment, micrometeorite bombardment probably creates the most long-lasting reactivity on the surfaces of grains, although solar wind impingement and short-wavelength UV radiation also contribute. The comminution process creates fractured surfaces with unsatisfied bonds. When these grains are inhaled and carried into the lungs, they will react with lung surfactant and cells, potentially causing tissue damage and disease. Tests on lunar simulants have shown that dissolution and leaching of metals can occur when the grains are exposed to water—the primary <span class="hlt">component</span> of lung fluid. However, simulants may behave differently than actual lunar soils. Rodent toxicity testing will be done using the respirable fraction of actual lunar soils (particles with physical size of less than 2.5 micrometers). We are currently separating the fine material from the coarser material that comprises >95% of the mass of each soil sample. Dry sieving is not practical in this size range, so a new system</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018MNRAS.tmp.1185M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018MNRAS.tmp.1185M"><span>Simulating galactic <span class="hlt">dust</span> grain evolution on a moving mesh</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>McKinnon, Ryan; Vogelsberger, Mark; Torrey, Paul; Marinacci, Federico; Kannan, Rahul</p> <p>2018-05-01</p> <p>Interstellar <span class="hlt">dust</span> is an important <span class="hlt">component</span> of the galactic ecosystem, playing a key role in multiple galaxy formation processes. We present a novel numerical framework for the dynamics and size evolution of <span class="hlt">dust</span> grains implemented in the moving-mesh hydrodynamics code AREPO suited for cosmological galaxy formation simulations. We employ a particle-based method for <span class="hlt">dust</span> subject to dynamical forces including drag and gravity. The drag force is implemented using a second-order semi-implicit integrator and validated using several <span class="hlt">dust</span>-hydrodynamical test problems. Each <span class="hlt">dust</span> particle has a grain size distribution, describing the local abundance of grains of different sizes. The grain size distribution is discretised with a second-order piecewise linear method and evolves in time according to various <span class="hlt">dust</span> physical processes, including accretion, sputtering, shattering, and coagulation. We present a novel scheme for stochastically forming <span class="hlt">dust</span> during stellar evolution and new methods for sub-cycling of <span class="hlt">dust</span> physics time-steps. Using this model, we simulate an isolated disc galaxy to study the impact of <span class="hlt">dust</span> physical processes that shape the interstellar grain size distribution. We demonstrate, for example, how <span class="hlt">dust</span> shattering shifts the grain size distribution to smaller sizes resulting in a significant rise of radiation extinction from optical to near-ultraviolet wavelengths. Our framework for simulating <span class="hlt">dust</span> and gas mixtures can readily be extended to account for other dynamical processes relevant in galaxy formation, like magnetohydrodynamics, radiation pressure, and thermo-chemical processes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRD..120.2437A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRD..120.2437A"><span>Optical properties of selected <span class="hlt">components</span> of mineral <span class="hlt">dust</span> aerosol processed with organic acids and humic material</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Alexander, Jennifer M.; Grassian, V. H.; Young, M. A.; Kleiber, P. D.</p> <p>2015-03-01</p> <p>Visible light scattering phase function and linear polarization profiles of mineral <span class="hlt">dust</span> <span class="hlt">components</span> processed with organic acids and humic material are measured, and results are compared to T-matrix simulations of the scattering properties. Processed samples include quartz mixed with humic material, and calcite reacted with acetic and oxalic acids. Clear differences in light scattering properties are observed for all three processed samples when compared to the unprocessed <span class="hlt">dust</span> or organic salt products. Results for quartz processed with humic acid sodium salt (NaHA) indicate the presence of both internally mixed quartz-NaHA particles and externally mixed NaHA aerosol. Simulations of light scattering suggest that the processed quartz particles become more moderate in shape due to the formation of a coating of humic material over the mineral core. Experimental results for calcite reacted with acetic acid are consistent with an external mixture of calcite and the reaction product, calcium acetate. Modeling of the light scattering properties does not require any significant change to the calcite particle shape distribution although morphology changes cannot be ruled out by our data. It is expected that calcite reacted with oxalic acid will produce internally mixed particles of calcite and calcium oxalate due to the low solubility of the product salt. However, simulations of the scattering for the calcite-oxalic acid system result in rather poor fits to the data when compared to the other samples. The poor fit provides a less accurate picture of the impact of processing in the calcite-oxalic acid system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFMPP12A..08M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFMPP12A..08M"><span>'DIRTMAP2': <span class="hlt">Dust</span> and Palaeoclimate.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Maher, B.</p> <p>2008-12-01</p> <p>The influence of <span class="hlt">dust</span> on climate, through changes in the radiative properties of the atmosphere and/or the CO2 content of the oceans and atmosphere (through iron fertilisation of high nutrient, low chlorophyll, HNLC, regions of the world's oceans), remains a poorly quantified and actively changing element of the Earth's climate system. <span class="hlt">Dust</span>-cycle models presently employ a relatively simple representation of <span class="hlt">dust</span> properties; these simplifications may severely limit the realism of simulations of the impact of changes in <span class="hlt">dust</span> loading on either or both radiative forcing and biogeochemical cycling. Further, whilst state-of-the-art models achieve reasonable estimates of <span class="hlt">dust</span> deposition in the far-field (i.e. at ocean locations), they under-estimate - by an order of magnitude - levels of <span class="hlt">dust</span> deposition over the continents, unless glacigenic <span class="hlt">dust</span> production is explicitly and spatially represented. The 'DIRTMAP2' working group aims to address these problems directly, through a series of explicitly interacting contributions from the international modelling and palaeo-data communities. A key aim of the project is to produce an updated version of the DIRTMAP database ('DIRTMAP2'), incorporating (a) records and age models newly available since ~ 2001, (b) longer records, and especially high-resolution records, that will target time windows also focused on by other international research programs (e.g. DO8/9, MIS5), (c) metadata to allow quality-control issues to be dealt with objectively, (d) information on mineralogy and isotopes relevant to provenancing, radiative forcing and iron bioavailability, and (e) enhanced characterisation of the aeolian <span class="hlt">component</span> of existing records. This update will be coordinated with work (led by Karen Kohfeld) to expand the DIRTMAP database to incorporate information on marine productivity and improved sedimentation rate estimation techniques. It will also build upon a recently-developed <span class="hlt">dust</span> model evaluation tool for current climate (e</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19880002221','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19880002221"><span>Composition, structure and chemistry of interstellar <span class="hlt">dust</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Tielens, Alexander G. G. M.; Allamandola, Louis J.</p> <p>1986-01-01</p> <p>The observational constraints on the composition of the interstellar <span class="hlt">dust</span> are analyzed. The <span class="hlt">dust</span> in the diffuse interstellar medium consists of a mixture of stardust (amorphous silicates, amorphous carbon, polycyclic aromatic hydrocarbons, and graphite) and interstellar medium <span class="hlt">dust</span> (organic refractory material). Stardust seems to dominate in the local diffuse interstellar medium. Inside molecular clouds, however, icy grain mantles are also important. The structural differences between crystalline and amorphous materials, which lead to differences in the optical properties, are discussed. The astrophysical consequences are briefly examined. The physical principles of grain surface chemistry are discussed and applied to the formation of molecular hydrogen and icy grain mantles inside dense molecular clouds. Transformation of these icy grain mantles into the organic refractory <span class="hlt">dust</span> <span class="hlt">component</span> observed in the diffuse interstellar medium requires ultraviolet sources inside molecular clouds as well as radical diffusion promoted by transient heating of the mantle. The latter process also returns a considerable fraction of the molecules in the grain mantle to the gas phase.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AsBio..17.1274B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AsBio..17.1274B"><span>Space <span class="hlt">Dust</span> Collisions as a Planetary Escape Mechanism</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Berera, Arjun</p> <p>2017-12-01</p> <p>It is observed that hypervelocity space <span class="hlt">dust</span>, which is continuously bombarding Earth, creates immense momentum flows in the atmosphere. Some of this fast space <span class="hlt">dust</span> inevitably will interact with the atmospheric system, transferring energy and moving particles around, with various possible consequences. This paper examines, with supporting estimates, the possibility that by way of collisions the Earth-grazing <span class="hlt">component</span> of space <span class="hlt">dust</span> can facilitate planetary escape of atmospheric particles, whether they are atoms and molecules that form the atmosphere or larger-sized particles. An interesting outcome of this collision scenario is that a variety of particles that contain telltale signs of Earth's organic story, including microbial life and life-essential molecules, may be "afloat" in Earth's atmosphere. The present study assesses the capability of this space <span class="hlt">dust</span> collision mechanism to propel some of these biological constituents into space.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20080015630','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20080015630"><span>Satellite-Based Assessment of Possible <span class="hlt">Dust</span> Aerosols Semi-Direct Effect on Cloud Water Path over East Asia</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Huang, Jianping; Lin, Bing; Minnis, Patrick; Wang, Tainhe; Wang, Xin; Hu, Yongxiang; Yi, Yuhong; Ayers, J. Kirk</p> <p>2006-01-01</p> <p>The semi-direct effects of <span class="hlt">dust</span> aerosols are analyzed over eastern Asia using 2 years (June 2002 to June 2004) of data from the Clouds and the Earth s Radiant Energy System (CERES) scanning radiometer and MODerate Resolution Imaging Spectroradiometer (MODIS) on the Aqua satellite, and 18 years (1984 to 2001) of International Satellite Cloud Climatology Project (ISCCP) data. The results show that the water path of <span class="hlt">dust</span>-contaminated clouds is considerably smaller than that of <span class="hlt">dust</span>-free clouds. The mean ice water path (IWP) and liquid water path (LWP) of dusty clouds are less than their <span class="hlt">dust</span>-free counterparts by 23.7% and 49.8%, respectively. The long-term statistical relationship derived from ISCCP also confirms that there is significant negative correlation between <span class="hlt">dust</span> storm index and ISCCP cloud water path. These results suggest that <span class="hlt">dust</span> aerosols <span class="hlt">warm</span> clouds, increase the evaporation of cloud droplets and further reduce cloud water path, the so-called semi-direct effect. The semi-direct effect may play a role in cloud development over arid and semi-arid areas of East Asia and contribute to the reduction of precipitation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22522514-destruction-interstellar-dust-evolving-supernova-remnant-shock-waves','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22522514-destruction-interstellar-dust-evolving-supernova-remnant-shock-waves"><span>DESTRUCTION OF INTERSTELLAR <span class="hlt">DUST</span> IN EVOLVING SUPERNOVA REMNANT SHOCK WAVES</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Slavin, Jonathan D.; Dwek, Eli; Jones, Anthony P., E-mail: jslavin@cfa.harvard.edu</p> <p>2015-04-10</p> <p>Supernova generated shock waves are responsible for most of the destruction of <span class="hlt">dust</span> grains in the interstellar medium (ISM). Calculations of the <span class="hlt">dust</span> destruction timescale have so far been carried out using plane parallel steady shocks, however, that approximation breaks down when the destruction timescale becomes longer than that for the evolution of the supernova remnant (SNR) shock. In this paper we present new calculations of grain destruction in evolving, radiative SNRs. To facilitate comparison with the previous study by Jones et al., we adopt the same <span class="hlt">dust</span> properties as in that paper. We find that the efficiencies of grainmore » destruction are most divergent from those for a steady shock when the thermal history of a shocked gas parcel in the SNR differs significantly from that behind a steady shock. This occurs in shocks with velocities ≳200 km s{sup −1} for which the remnant is just beginning to go radiative. Assuming SNRs evolve in a <span class="hlt">warm</span> phase dominated ISM, we find <span class="hlt">dust</span> destruction timescales are increased by a factor of ∼2 compared to those of Jones et al., who assumed a hot gas dominated ISM. Recent estimates of supernova rates and ISM mass lead to another factor of ∼3 increase in the destruction timescales, resulting in a silicate grain destruction timescale of ∼2–3 Gyr. These increases, while not able to resolve the problem of the discrepant timescales for silicate grain destruction and creation, are an important step toward understanding the origin and evolution of <span class="hlt">dust</span> in the ISM.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150003513','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150003513"><span>Destruction of Interstellar <span class="hlt">Dust</span> in Evolving Supernova Remnant Shock Waves</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Slavin, Jonathan D.; Dwek, Eli; Jones, Anthony P.</p> <p>2015-01-01</p> <p>Supernova generated shock waves are responsible for most of the destruction of <span class="hlt">dust</span> grains in the interstellar medium (ISM). Calculations of the <span class="hlt">dust</span> destruction timescale have so far been carried out using plane parallel steady shocks, however that approximation breaks down when the destruction timescale becomes longer than that for the evolution of the supernova remnant (SNR) shock. In this paper we present new calculations of grain destruction in evolving, radiative SNRs. To facilitate comparison with the previous study by Jones et al. (1996), we adopt the same <span class="hlt">dust</span> properties as in that paper. We find that the efficiencies of grain destruction are most divergent from those for a steady shock when the thermal history of a shocked gas parcel in the SNR differs significantly from that behind a steady shock. This occurs in shocks with velocities 200 km s(exp -1) for which the remnant is just beginning to go radiative. Assuming SNRs evolve in a <span class="hlt">warm</span> phase dominated ISM, we find <span class="hlt">dust</span> destruction timescales are increased by a factor of approximately 2 compared to those of Jones et al. (1996), who assumed a hot gas dominated ISM. Recent estimates of supernova rates and ISM mass lead to another factor of approximately 3 increase in the destruction timescales, resulting in a silicate grain destruction timescale of approximately 2-3 Gyr. These increases, while not able resolve the problem of the discrepant timescales for silicate grain destruction and creation, are an important step towards understanding the origin, and evolution of <span class="hlt">dust</span> in the ISM.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JAMES..10..951R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JAMES..10..951R"><span>The Madden-Julian Oscillation and the Indo-Pacific <span class="hlt">Warm</span> Pool</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Raymond, David J.; Fuchs, Željka</p> <p>2018-04-01</p> <p>A minimal model of the interaction of the Madden-Julian oscillation (MJO) with the Indo-Pacific <span class="hlt">warm</span> pool is presented. This model is based on the linear superposition of the flow associated with a highly simplified treatment of the MJO plus the flow induced by the <span class="hlt">warm</span> pool itself. Both of these <span class="hlt">components</span> parameterize rainfall as proportional to the column water vapor, which in turn is governed by a linearized moisture equation in which WISHE (wind induced surface heat exchange) plays a governing role. The MJO <span class="hlt">component</span> has maximum growth rate for planetary wavenumber 1 and is equatorially trapped with purely zonal winds. The <span class="hlt">warm</span> pool <span class="hlt">component</span> exhibits a complex flow pattern, differing significantly from the classical Gill model as a result of the mean easterly flow. The combination of the two produce a flow that reproduces many aspects of the observed global flow associated with the MJO.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016A%26A...596A..96E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016A%26A...596A..96E"><span>On the properties of <span class="hlt">dust</span> and gas in the environs of V838 Monocerotis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Exter, K. M.; Cox, N. L. J.; Swinyard, B. M.; Matsuura, M.; Mayer, A.; De Beck, E.; Decin, L.</p> <p>2016-12-01</p> <p>Aims: We aim to probe the close and distant circumstellar environments of the stellar outburst object V838 Mon. Methods: Herschel far-infrared imaging and spectroscopy were taken at several epochs to probe the central point source and the extended environment of V838 Mon. PACS and SPIRE maps were used to obtain photometry of the <span class="hlt">dust</span> immediately around V838 Mon, and in the surrounding infrared-bright region. These maps were fitted in 1d and 2d to measure the temperature, mass, and β of the two <span class="hlt">dust</span> sources. PACS and SPIRE spectra were used to detect emission lines from the extended atmosphere of the star, which were then modelled to study the physical conditions in the emitting material. HIFI spectra were taken to measure the kinematics of the extended atmosphere but unfortunately yielded no detections. Results: Fitting of the far-infrared imaging of V838 Mon reveals 0.5-0.6 M⊙ of ≈19 K <span class="hlt">dust</span> in the environs (≈2.7 pc) surrounding V838 Mon. The surface-integrated infrared flux (signifying the thermal light echo), and derived <span class="hlt">dust</span> properties do not vary significantly between the different epochs. We measured the photometry of the point source. As the peak of the SED (Spectral Energy Distribution) lies outside the Herschel spectral range, it is only by incorporating data from other observatories and previous epochs that we can usefully fit the SED; with this we explicitly assume no evolution of the point source between the epochs. We find that <span class="hlt">warm</span> <span class="hlt">dust</span> with a temperature 300 K distributed over a radius of 150-200 AU. We fit the far-infrared lines of CO arising from the point source, from an extended environment around V838 Mon. Assuming a model of a spherical shell for this gas, we find that the CO appears to arise from two temperature zones: a cold zone (Tkin ≈ 18 K) that could be associated with the ISM or possibly with a cold layer in the outermost part of the shell, and a <span class="hlt">warm</span> (Tkin ≈ 400 K) zone that is associated with the extended environment of V838</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015A%26A...573L...1O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015A%26A...573L...1O"><span>ALMA observations of anisotropic <span class="hlt">dust</span> mass loss in the inner circumstellar environment of the red supergiant VY Canis Majoris</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>O'Gorman, E.; Vlemmings, W.; Richards, A. M. S.; Baudry, A.; De Beck, E.; Decin, L.; Harper, G. M.; Humphreys, E. M.; Kervella, P.; Khouri, T.; Muller, S.</p> <p>2015-01-01</p> <p>The processes leading to <span class="hlt">dust</span> formation and the subsequent role it plays in driving mass loss in cool evolved stars is an area of intense study. Here we present high resolution ALMA Science Verification data of the continuum emission around the highly evolved oxygen-rich red supergiant VY CMa. These data enable us to study the <span class="hlt">dust</span> in its inner circumstellar environment at a spatial resolution of 129 mas at 321 GHz and 59 mas at 658 GHz, thus allowing us to trace <span class="hlt">dust</span> on spatial scales down to 11 R⋆ (71 AU). Two prominent <span class="hlt">dust</span> <span class="hlt">components</span> are detected and resolved. The brightest <span class="hlt">dust</span> <span class="hlt">component</span>, C, is located 334 mas (61 R⋆) southeast of the star and has a <span class="hlt">dust</span> mass of at least 2.5 × 10-4 M⊙. It has a <span class="hlt">dust</span> emissivity spectral index of β = -0.1 at its peak, implying that it is optically thick at these frequencies with a cool core of Td ≲ 100 K. Interestingly, not a single molecule in the ALMA data has emission close to the peak of this massive <span class="hlt">dust</span> clump. The other main <span class="hlt">dust</span> <span class="hlt">component</span>, VY, is located at the position of the star and contains a total <span class="hlt">dust</span> mass of 4.0 × 10-5 M⊙. It also contains a weaker <span class="hlt">dust</span> feature extending over 60 R⋆ to the north with the total <span class="hlt">component</span> having a typical <span class="hlt">dust</span> emissivity spectral index of β = 0.7. We find that at least 17% of the <span class="hlt">dust</span> mass around VY CMa is located in clumps ejected within a more quiescent roughly spherical stellar wind, with a quiescent <span class="hlt">dust</span> mass loss rate of 5 × 10-6 M⊙yr-1. The anisotropic morphology of the <span class="hlt">dust</span> indicates a continuous, directed mass loss over a few decades, suggesting that this mass loss cannot be driven by large convection cells alone. Appendices are available in electronic form at http://www.aanda.org</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29808822','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29808822"><span>The effects of global <span class="hlt">warming</span> on allergic diseases.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chan, A W; Hon, K L; Leung, T F; Ho, M H; Rosa Duque, J S; Lee, T H</p> <p>2018-06-01</p> <p>Global <span class="hlt">warming</span> is a public health emergency. Substantial scientific evidence indicates an unequivocal rising trend in global surface temperature that has caused higher atmospheric levels of moisture retention leading to more frequent extreme weather conditions, shrinking ice volume, and gradually rising sea levels. The concomitant rise in the prevalence of allergic diseases is closely related to these environmental changes because <span class="hlt">warm</span> and moist environments favour the proliferation of common allergens such as pollens, <span class="hlt">dust</span> mites, molds, and fungi. Global <span class="hlt">warming</span> also stresses ecosystems, further accelerating critical biodiversity loss. Excessive carbon dioxide, together with the <span class="hlt">warming</span> of seawater, promotes ocean acidification and oxygen depletion. This results in a progressive decline of phytoplankton and fish growth that in turn promotes the formation of larger oceanic dead zones, disrupting the food chain and biodiversity. Poor environmental biodiversity and a reduction in the microbiome spectrum are risk factors for allergic diseases in human populations. While climate change and the existence of an allergy epidemic are closely linked according to robust international research, efforts to mitigate these have encountered strong resistance because of vested economic and political concerns in different countries. International collaboration to establish legally binding regulations should be mandatory for forest protection and energy saving. Lifestyle and behavioural changes should also be advocated at the individual level by focusing on low carbon living; avoiding food wastage; and implementing the 4Rs: reduce, reuse, recycle, and replace principles. These lifestyle measures are entirely consistent with the current recommendations for allergy prevention. Efforts to mitigate climate change, preserve biodiversity, and prevent chronic diseases are interdependent disciplines.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4030294','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4030294"><span>Summary of the development of a signature for detection of residual <span class="hlt">dust</span> from collapse of the World Trade Center buildings</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Lowers, Heather A; Meeker, Gregory P; Lioy, Paul J; Lippmann, Morton</p> <p>2014-01-01</p> <p>The collapse of the World Trade Center (WTC) towers on September 11, 2001, caused lower Manhattan and adjacent areas to be covered in millimeters to centimeters of <span class="hlt">dust</span>. WTC <span class="hlt">dust</span> penetrated into indoor spaces, and public health concerns remain regarding exposure to possible residual <span class="hlt">dust</span> in the affected areas. The goal of the studies outlined in this review was to determine which, if any, <span class="hlt">components</span> of the bulk WTC <span class="hlt">dust</span> are sufficiently above typical background <span class="hlt">dust</span> levels in New York City to develop an analytical method to screen for the <span class="hlt">component(s</span>). <span class="hlt">Components</span> of the <150-µm-size fraction of the <span class="hlt">dust</span> are gypsum, phases compatible with crushed concrete, man-made vitreous fibers (MMVFs), silica, lead, chrysotile asbestos, and other materials. Slag wool was the most common WTC MMVF, whereas soda-lime glass and rock wool were minor to trace constituents. Most background samples also contained gypsum, phases compatible with concrete, and MMVF. However, the proportions of the various MMVF in background samples are typically unlike those characteristic of bulk WTC <span class="hlt">dust</span>. Results indicate that slag wool can be used as a signature marker to identify areas that contain potential residual WTC <span class="hlt">dust</span> contamination at concentrations that are less than average background levels for the material. PMID:18478046</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5664528','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5664528"><span>Origin of the RNA world: The fate of nucleobases in <span class="hlt">warm</span> little ponds</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Pudritz, Ralph E.; Semenov, Dmitry A.; Henning, Thomas K.</p> <p>2017-01-01</p> <p>Before the origin of simple cellular life, the building blocks of RNA (nucleotides) had to form and polymerize in favorable environments on early Earth. At this time, meteorites and interplanetary <span class="hlt">dust</span> particles delivered organics such as nucleobases (the characteristic molecules of nucleotides) to <span class="hlt">warm</span> little ponds whose wet–dry cycles promoted rapid polymerization. We build a comprehensive numerical model for the evolution of nucleobases in <span class="hlt">warm</span> little ponds leading to the emergence of the first nucleotides and RNA. We couple Earth’s early evolution with complex prebiotic chemistry in these environments. We find that RNA polymers must have emerged very quickly after the deposition of meteorites (less than a few years). Their constituent nucleobases were primarily meteoritic in origin and not from interplanetary <span class="hlt">dust</span> particles. Ponds appeared as continents rose out of the early global ocean, but this increasing availability of “targets” for meteorites was offset by declining meteorite bombardment rates. Moreover, the rapid losses of nucleobases to pond seepage during wet periods, and to UV photodissociation during dry periods, mean that the synthesis of nucleotides and their polymerization into RNA occurred in just one to a few wet–dry cycles. Under these conditions, RNA polymers likely appeared before 4.17 billion years ago. PMID:28973920</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_15 --> <div id="page_16" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="301"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28973920','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28973920"><span>Origin of the RNA world: The fate of nucleobases in <span class="hlt">warm</span> little ponds.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Pearce, Ben K D; Pudritz, Ralph E; Semenov, Dmitry A; Henning, Thomas K</p> <p>2017-10-24</p> <p>Before the origin of simple cellular life, the building blocks of RNA (nucleotides) had to form and polymerize in favorable environments on early Earth. At this time, meteorites and interplanetary <span class="hlt">dust</span> particles delivered organics such as nucleobases (the characteristic molecules of nucleotides) to <span class="hlt">warm</span> little ponds whose wet-dry cycles promoted rapid polymerization. We build a comprehensive numerical model for the evolution of nucleobases in <span class="hlt">warm</span> little ponds leading to the emergence of the first nucleotides and RNA. We couple Earth's early evolution with complex prebiotic chemistry in these environments. We find that RNA polymers must have emerged very quickly after the deposition of meteorites (less than a few years). Their constituent nucleobases were primarily meteoritic in origin and not from interplanetary <span class="hlt">dust</span> particles. Ponds appeared as continents rose out of the early global ocean, but this increasing availability of "targets" for meteorites was offset by declining meteorite bombardment rates. Moreover, the rapid losses of nucleobases to pond seepage during wet periods, and to UV photodissociation during dry periods, mean that the synthesis of nucleotides and their polymerization into RNA occurred in just one to a few wet-dry cycles. Under these conditions, RNA polymers likely appeared before 4.17 billion years ago.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFMGC22A..06S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFMGC22A..06S"><span>Is Global <span class="hlt">Warming</span> Accelerating?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shukla, J.; Delsole, T. M.; Tippett, M. K.</p> <p>2009-12-01</p> <p>A global pattern that fluctuates naturally on decadal time scales is identified in climate simulations and observations. This newly discovered <span class="hlt">component</span>, called the Global Multidecadal Oscillation (GMO), is related to the Atlantic Meridional Oscillation and shown to account for a substantial fraction of decadal fluctuations in the observed global average sea surface temperature. IPCC-class climate models generally underestimate the variance of the GMO, and hence underestimate the decadal fluctuations due to this <span class="hlt">component</span> of natural variability. Decomposing observed sea surface temperature into a <span class="hlt">component</span> due to anthropogenic and natural radiative forcing plus the GMO, reveals that most multidecadal fluctuations in the observed global average sea surface temperature can be accounted for by these two <span class="hlt">components</span> alone. The fact that the GMO varies naturally on multidecadal time scales implies that it can be predicted with some skill on decadal time scales, which provides a scientific rationale for decadal predictions. Furthermore, the GMO is shown to account for about half of the <span class="hlt">warming</span> in the last 25 years and hence a substantial fraction of the recent acceleration in the rate of increase in global average sea surface temperature. Nevertheless, in terms of the global average “well-observed” sea surface temperature, the GMO can account for only about 0.1° C in transient, decadal-scale fluctuations, not the century-long 1° C <span class="hlt">warming</span> that has been observed during the twentieth century.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/866828','DOE-PATENT-XML'); return false;" href="https://www.osti.gov/servlets/purl/866828"><span>Determining inert content in coal <span class="hlt">dust</span>/rock <span class="hlt">dust</span> mixture</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Sapko, Michael J.; Ward, Jr., Jack A.</p> <p>1989-01-01</p> <p>A method and apparatus for determining the inert content of a coal <span class="hlt">dust</span> and rock <span class="hlt">dust</span> mixture uses a transparent window pressed against the mixture. An infrared light beam is directed through the window such that a portion of the infrared light beam is reflected from the mixture. The concentration of the reflected light is detected and a signal indicative of the reflected light is generated. A normalized value for the generated signal is determined according to the relationship .phi.=(log i.sub.c `log i.sub.co) / (log i.sub.c100 -log i.sub.co) where i.sub.co =measured signal at 0% rock <span class="hlt">dust</span> i.sub.c100 =measured signal at 100% rock <span class="hlt">dust</span> i.sub.c =measured signal of the mixture. This normalized value is then correlated to a predetermined relationship of .phi. to rock <span class="hlt">dust</span> percentage to determine the rock <span class="hlt">dust</span> content of the mixture. The rock <span class="hlt">dust</span> content is displayed where the percentage is between 30 and 100%, and an indication of out-of-range is displayed where the rock <span class="hlt">dust</span> percent is less than 30%. Preferably, the rock <span class="hlt">dust</span> percentage (RD%) is calculated from the predetermined relationship RD%=100+30 log .phi.. where the <span class="hlt">dust</span> mixture initially includes moisture, the <span class="hlt">dust</span> mixture is dried before measuring by use of 8 to 12 mesh molecular-sieves which are shaken with the <span class="hlt">dust</span> mixture and subsequently screened from the <span class="hlt">dust</span> mixture.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013ascl.soft07001C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013ascl.soft07001C"><span><span class="hlt">Dust</span>EM: <span class="hlt">Dust</span> extinction and emission modelling</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Compiègne, M.; Verstraete, L.; Jones, A.; Bernard, J.-P.; Boulanger, F.; Flagey, N.; Le Bourlot, J.; Paradis, D.; Ysard, N.</p> <p>2013-07-01</p> <p><span class="hlt">Dust</span>EM computes the extinction and the emission of interstellar <span class="hlt">dust</span> grains heated by photons. It is written in Fortran 95 and is jointly developed by IAS and CESR. The <span class="hlt">dust</span> emission is calculated in the optically thin limit (no radiative transfer) and the default spectral range is 40 to 108 nm. The code is designed so <span class="hlt">dust</span> properties can easily be changed and mixed and to allow for the inclusion of new grain physics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20010092222&hterms=Russell&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAuthor-Name%26Nf%3DPublication-Date%257CBTWN%2B20000101%2B20001231%26N%3D0%26No%3D10%26Ntt%3DRussell','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20010092222&hterms=Russell&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAuthor-Name%26Nf%3DPublication-Date%257CBTWN%2B20000101%2B20001231%26N%3D0%26No%3D10%26Ntt%3DRussell"><span>Solar Spectral Radiative Forcing Due to <span class="hlt">Dust</span> Aerosol During the Puerto Rico <span class="hlt">Dust</span> Experiment</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Pilewskie, P.; Bergstrom, R.; Rabbette, M.; Livingston, J.; Russell, P.; Gore, Warren J. (Technical Monitor)</p> <p>2000-01-01</p> <p>During the Puerto Rico <span class="hlt">Dust</span> Experiment (PRIDE) upwelling and downwelling solar spectral irradiance was measured on board the SPAWAR Navajo and downwelling solar spectral flux was measured at a surface site using the NASA Ames Solar Spectral Flux Radiometer. These data will be used to determine the net solar radiative forcing of <span class="hlt">dust</span> aerosol and to quantify the solar spectral radiative energy budget in the presence of elevated aerosol loading. We will assess the variability in spectral irradiance using formal principal <span class="hlt">component</span> analysis procedures and relate the radiative variability to aerosol microphysical properties. Finally, we will characterize the sea surface reflectance to improve aerosol optical depth retrievals from the AVHRR satellite and to validate SeaWiFS ocean color products.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010ACP....10.8649W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010ACP....10.8649W"><span>The potential influence of Asian and African mineral <span class="hlt">dust</span> on ice, mixed-phase and liquid water clouds</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wiacek, A.; Peter, T.; Lohmann, U.</p> <p>2010-09-01</p> <p>This modelling study explores the availability of mineral <span class="hlt">dust</span> particles as ice nuclei for interactions with ice, mixed-phase and liquid water clouds, also tracking the particles' history of cloud-processing. We performed 61 320 one-week forward trajectory calculations originating near the surface of major <span class="hlt">dust</span> emitting regions in Africa and Asia using high-resolution meteorological analysis fields for the year 2007. <span class="hlt">Dust</span>-bearing trajectories were assumed to be those coinciding with known <span class="hlt">dust</span> emission seasons, without explicitly modelling <span class="hlt">dust</span> emission and deposition processes. We found that <span class="hlt">dust</span> emissions from Asian deserts lead to a higher potential for interactions with high ice clouds, despite being the climatologically much smaller <span class="hlt">dust</span> emission source. This is due to Asian regions experiencing significantly more ascent than African regions, with strongest ascent in the Asian Taklimakan desert at ~25%, ~40% and 10% of trajectories ascending to 300 hPa in spring, summer and fall, respectively. The specific humidity at each trajectory's starting point was transported in a Lagrangian manner and relative humidities with respect to water and ice were calculated in 6-h steps downstream, allowing us to estimate the formation of liquid, mixed-phase and ice clouds. Downstream of the investigated <span class="hlt">dust</span> sources, practically none of the simulated air parcels reached conditions of homogeneous ice nucleation (T≲-40 °C) along trajectories that have not experienced water saturation first. By far the largest fraction of cloud forming trajectories entered conditions of mixed-phase clouds, where mineral <span class="hlt">dust</span> will potentially exert the biggest influence. The majority of trajectories also passed through atmospheric regions supersaturated with respect to ice but subsaturated with respect to water, where so-called "<span class="hlt">warm</span> ice clouds" (T≳-40 °C) theoretically may form prior to supercooled water or mixed-phase clouds. The importance of "<span class="hlt">warm</span> ice clouds" and the general influence</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017nova.pres.2839K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017nova.pres.2839K"><span>Trapping <span class="hlt">Dust</span> to Form Planets</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kohler, Susanna</p> <p>2017-10-01</p> <p>Growing a planet from a <span class="hlt">dust</span> grain is hard work! A new study explores how vortices in protoplanetary disks can assist this process.When <span class="hlt">Dust</span> Growth FailsTop: ALMA image of the protoplanetary disk of V1247 Orionis, with different emission <span class="hlt">components</span> labeled. Bottom: Synthetic image constructed from the best-fit model. [Kraus et al. 2017]Gradual accretion onto a seed particle seems like a reasonable way to grow a planet from a grain of <span class="hlt">dust</span>; after all, planetary embryos orbit within dusty protoplanetary disks, which provides them with plenty of fuel to accrete so they can grow. Theres a challenge to this picture, though: the radial drift problem.The radial drift problem acknowledges that, as growing <span class="hlt">dust</span> grains orbit within the disk, the drag force on them continues to grow as well. For large enough <span class="hlt">dust</span> grains perhaps around 1 millimeter the drag force will cause the grains orbits to decay, and the particles drift into the star before they are able to grow into planetesimals and planets.A Close-Up Look with ALMASo how do we overcome the radial drift problem in order to form planets? A commonly proposed mechanism is <span class="hlt">dust</span> trapping, in which long-lived vortices in the disk trap the <span class="hlt">dust</span> particles, preventing them from falling inwards. This allows the particles to persist for millions of years long enough to grow beyond the radial drift barrier.Observationally, these <span class="hlt">dust</span>-trapping vortices should have signatures: we would expect to see, at millimeter wavelengths, specific bright, asymmetric structures where the trapping occurs in protoplanetary disks. Such disk structures have been difficult to spot with past instrumentation, but the Atacama Large Millimeter/submillimeter Array (ALMA) has made some new observations of the disk V1247 Orionis that might be just what were looking for.Schematic of the authors model for the disk of V1247 Orionis. [Kraus et al. 2017]Trapped in a Vortex?ALMAs observations of V1247 Orionis are reported by a team of scientists led by Stefan</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4685600','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4685600"><span>Exposure to flour <span class="hlt">dust</span> in the occupational environment</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Stobnicka, Agata; Górny, Rafał L.</p> <p>2015-01-01</p> <p>Exposure to flour <span class="hlt">dust</span> can be found in the food industry and animal feed production. It may result in various adverse health outcomes from conjunctivitis to baker's asthma. In this paper, flour <span class="hlt">dust</span> exposure in the above-mentioned occupational environments is characterized and its health effects are discussed. A peer-reviewed literature search was carried out and all available published materials were included if they provided information on the above-mentioned elements. The hitherto conducted studies show that different <span class="hlt">components</span> of flour <span class="hlt">dust</span> like enzymes, proteins and baker's additives can cause both non-allergic and allergic reactions among exposed workers. Moreover, the problem of exposure to cereal allergens present in flour <span class="hlt">dust</span> can also be a concern for bakers’ family members. Appreciating the importance of all these issues, the exposure assessment methods, hygienic standards and preventive measures are also addressed in this paper. PMID:26414680</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMOS14A..02D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMOS14A..02D"><span>Some <span class="hlt">Dust</span>/Ocean Connections - Past, Present, and Future</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Duce, R. A.</p> <p>2015-12-01</p> <p>Atmospheric <span class="hlt">dust</span> has been the subject of communications for more than 3000 years, since the ancient Chinese book Chronicles Reported on Bamboo Shoots in 1150 BC. Similar reports of hwangsa and woo-tou in ancient Korean and kosa in ancient Japanese literature also indicated major Asian <span class="hlt">dust</span> events in those areas. Western observers noted <span class="hlt">dust</span> storms in India and Afghanistan in the early 1800s, while in the 1840s Darwin surmised that Sahara <span class="hlt">dust</span> could be an important <span class="hlt">component</span> of marine sedimentation in the North Atlantic. More recent interest has focused on the importance of <span class="hlt">dust</span> as a source of the nutrients iron and phosphorus in the global ocean and the role of iron as a limiting nutrient in many areas of the surface ocean. While significant progress has been made in the past 25 years in identifying important <span class="hlt">dust</span>/ocean connections, many issues remain. Included are the relative dearth of long-term measurements of atmospheric <span class="hlt">dust</span> (and iron and phosphorus) over and deposition to the ocean, especially in the southern hemisphere; comparisons between modeled and measured deposition of <span class="hlt">dust</span> to the ocean; and the solubility of iron and phosphorus (and thus their availability as nutrients) after the mineral matter enters the ocean. Addressing these problems will certainly help to provide more accurate estimates of the input of <span class="hlt">dust</span> to the ocean and its impacts. However, future changes in <span class="hlt">dust</span> emissions in a warmer world as well as changes in the acid/base environment that mineral <span class="hlt">dust</span> experiences during its transport and deposition as a result of emission controls on atmospheric NOx and SO2 are two facors that may change the input of these nutrients to the ocean and their impacts in the coming years. These and other issues will be reviewed in this paper.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/11399717','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/11399717"><span>Pharmacologic properties of brewery <span class="hlt">dust</span> extracts in vitro.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Schachter, E N; Zuskin, E; Rienzi, N; Goswami, S; Castranova, V; Whitmer, M; Siegel, P</p> <p>2001-06-01</p> <p>To study the effects of extracts of brewery <span class="hlt">dust</span> on isolated guinea pig tracheal smooth muscle in vitro. Parallel pharmacologic intervention on guinea pig tracheal rings that were obtained from the same animal. Mount Sinai School of Medicine, Department of Pulmonary Medicine. The isolated guinea pig tracheal tissue of 18 guinea pigs. Pretreatment of guinea pig rings by mediator-modifying agents before challenge with the brewery <span class="hlt">dust</span> extracts. The effect of brewery <span class="hlt">dust</span> extracts on isolated guinea pig tracheal smooth muscle was studied using water-soluble extracts of <span class="hlt">dust</span> obtained from brewery materials, including hops, barley, and brewery yeast. <span class="hlt">Dust</span> extracts were prepared as a 1:10 (wt/vol) aqueous solution. Dose-related contractions of nonsensitized guinea pig tracheas were demonstrated using these extracts. The <span class="hlt">dust</span> extracts contained significant quantities of bacterial <span class="hlt">components</span> (eg, endotoxin and n-formyl-methionyl-leucyl-phenylalanine), but these agents were not thought to contribute directly to the constrictor effect of the <span class="hlt">dusts</span>. Pharmacologic studies were performed by pretreating guinea pig tracheal tissue with the following drugs known to modulate smooth muscle contraction: atropine; indomethacin; pyrilamine; LY171883; nordihydroguaiaretic acid; captopril; thiorphan; verapamil; and TMB8. The constrictor effects of the <span class="hlt">dust</span> extracts were inhibited by a wide variety of agents, the patterns of which depended on the <span class="hlt">dust</span> extract. Atropine consistently and strikingly reduced the contractile effects of these extracts. These observations may suggest an interaction of the extracts with parasympathetic nerves or, more directly, with muscarinic receptors. The inhibition of contraction by the blocking of other mediators was less effective and varied with the <span class="hlt">dust</span> extract. We suggest that brewery <span class="hlt">dust</span> extracts cause a dose-related airway smooth muscle constriction by nonimmunologic mechanisms involving a variety of airway mediators and, possibly, cholinergic</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20010069260','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20010069260"><span><span class="hlt">Warm</span>-Core Intensification Through Horizontal Eddy Heat Transports into the Eye</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Braun, Scott A.; Montgomery, Michael T.; Fulton, John; Nolan, David S.; Starr, David OC (Technical Monitor)</p> <p>2001-01-01</p> <p>A simulation of Hurricane Bob (1991) using the PSU/NCAR MM5 mesoscale model with a finest mesh spacing of 1.3 km is used to diagnose the heat budget of the hurricane. Heat budget terms, including latent and radiative heating, boundary layer forcing, and advection terms were output directly from the model for a 6-h period with 2-min frequency. Previous studies of <span class="hlt">warm</span> core formation have emphasized the <span class="hlt">warming</span> associated with gentle subsidence within the eye. The simulation of Hurricane Bob confirms subsidence <span class="hlt">warming</span> as a major factor for eye <span class="hlt">warming</span>, but also shows a significant contribution from horizontal advective terms. When averaged over the area of the eye, subsidence is found to strongly <span class="hlt">warm</span> the mid-troposphere (2-9 km) while horizontal advection <span class="hlt">warms</span> the mid to upper troposphere (5-13 km) with about equal magnitude. Partitioning of the horizontal advective terms into azimuthal mean and eddy <span class="hlt">components</span> shows that the mean radial circulation does not, as expected, generally contribute to this <span class="hlt">warming</span>, but that it is produced almost entirely by the horizontal eddy transport of heat into the eye. A further breakdown of the eddy <span class="hlt">components</span> into azimuthal wave numbers 1, 2, and higher indicates that the <span class="hlt">warming</span> is dominated by wave number 1 asymmetries, with smaller coming from higher wave numbers. <span class="hlt">Warming</span> by horizontal eddy transport is consistent with idealized modeling of vortex Rossby waves and work is in progress to identify and clarify the role of vortex Rossby waves in <span class="hlt">warm</span>-core intensification in both the full-physics model and idealized models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/1107490-uncertainty-modeling-dust-mass-balance-radiative-forcing-from-size-parameterization','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1107490-uncertainty-modeling-dust-mass-balance-radiative-forcing-from-size-parameterization"><span>Uncertainty in Modeling <span class="hlt">Dust</span> Mass Balance and Radiative Forcing from Size Parameterization</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Zhao, Chun; Chen, Siyu; Leung, Lai-Yung R.</p> <p>2013-11-05</p> <p>-mode approach yields weaker <span class="hlt">dust</span> absorptivity. Overall, on quasi-global average, the three size parameterizations result in a significant difference of a factor of 2~3 in <span class="hlt">dust</span> surface cooling (-1.02~-2.87 W m-2) and atmospheric <span class="hlt">warming</span> (0.39~0.96 W m-2) and in a tremendous difference of a factor of ~10 in <span class="hlt">dust</span> TOA cooling (-0.24~-2.20 W m-2). An uncertainty of a factor of 2 is quantified in <span class="hlt">dust</span> emission estimation due to the different size parameterizations. This study also highlights the uncertainties in modeling <span class="hlt">dust</span> mass and number loading, deposition fluxes, and radiative forcing resulting from different size parameterizations, and motivates further investigation of the impact of size parameterizations on modeling <span class="hlt">dust</span> impacts on air quality, climate, and ecosystem.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29936683','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29936683"><span>The Role of <span class="hlt">Dust</span> Mites in Allergy.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Miller, Jeffrey D</p> <p>2018-06-23</p> <p>House <span class="hlt">dust</span> mites are an unsurpassed cause of atopic sensitization and allergic illness throughout the world. The major allergenic <span class="hlt">dust</span> mites Dermatophagoides pteronyssinus, Dermatophagoides farinae, Euroglyphus maynei, and Blomia tropicalis are eight-legged members of the Arachnid class. Their approximately 3-month lifespan comprises egg, larval, protonymph, tritonymph, and adult stages, with adults, about one fourth to one third of a millimeter in size, being at the threshold of visibility. The geographic and seasonal distributions of <span class="hlt">dust</span> mites are determined by their need for adequate humidity, while their distribution within substrates is further determined by their avoidance of light. By contacting the epithelium of the eyes, nose, lower airways, skin, and gut, the allergen-containing particles of <span class="hlt">dust</span> mites can induce sensitization and atopic symptoms in those organs. Various mite allergens, contained primarily in mite fecal particles but also in shed mite exoskeletons and decaying mite body fragments, have properties that include proteolytic activity, homology with the lipopolysaccharide-binding <span class="hlt">component</span> of Toll-like receptor 4, homology with other invertebrate tropomyosins, and chitin-cleaving and chitin-binding activity. Mite proteases have direct epithelial effects including the breaching of tight junctions and the stimulation of protease-activated receptors, the latter inducing pruritus, epithelial dysfunction, and cytokine release. Other <span class="hlt">components</span>, including chitin, unmethylated mite and bacterial DNA, and endotoxin, activate pattern recognition receptors of the innate immune system and act as adjuvants promoting sensitization to mite and other allergens. Clinical conditions resulting from mite sensitization and exposure include rhinitis, sinusitis, conjunctivitis, asthma, and atopic dermatitis. Systemic allergy symptoms can also occur from the ingestion of cross-reacting invertebrates, such as shrimp or snail, or from the accidental ingestion of mite</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20130001649','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20130001649"><span>Direct Radiative Effect of Mineral <span class="hlt">Dust</span> on the Development of African Easterly Wave in Late Summer, 2003-2007</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ma, Po-Lun; Zhang, Kai; Shi, Jainn Jong; Matsui, Toshihisa; Arking, Albert</p> <p>2012-01-01</p> <p>Episodic events of both Saharan <span class="hlt">dust</span> outbreaks and African Easterly Waves (AEWs) are observed to move westward over the eastern tropical Atlantic Ocean. The relationship between the <span class="hlt">warm</span>, dry, and dusty Saharan Air Layer (SAL) on the nearby storms has been the subject of considerable debate. In this study, the Weather Research and Forecasting (WRF) model is used to investigate the radiative effect of <span class="hlt">dust</span> on the development of AEWs during August and September, the months of maximum tropical cyclone activity, in years 2003-2007. The simulations show that <span class="hlt">dust</span> radiative forcing enhances the convective instability of the environment. As a result, most AEWs intensify in the presence of a <span class="hlt">dust</span> layer. The Lorenz energy cycle analysis reveals that the <span class="hlt">dust</span> radiative forcing enhances the condensational heating, which elevates the zonal and eddy available potential energy. In turn, available potential energy is effectively converted to eddy kinetic energy, in which local convective overturning plays the primary role. The magnitude of the intensification effect depends on the initial environmental conditions, including moisture, baroclinity, and the depth of the boundary layer. We conclude that <span class="hlt">dust</span> radiative forcing, albeit small, serves as a catalyst to promote local convection that facilitates AEW development.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22599094-shock-structures-strongly-coupled-self-gravitating-opposite-polarity-dust-plasma','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22599094-shock-structures-strongly-coupled-self-gravitating-opposite-polarity-dust-plasma"><span>Shock structures in a strongly coupled self-gravitating opposite-polarity <span class="hlt">dust</span> plasma</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Mamun, A. A.; Schlickeiser, R.</p> <p>2016-03-15</p> <p>A strongly coupled, self-gravitating, opposite-polarity <span class="hlt">dust</span> plasma (containing strongly coupled inertial positive and negative <span class="hlt">dust</span> fluids, and inertialess weakly coupled ions) is considered. The generalized hydrodynamic model and the reductive perturbation method are employed to examine the possibility for the formation of the <span class="hlt">dust</span>-acoustic (DA) shock structures in such an opposite-polarity <span class="hlt">dust</span> plasma. It has been shown that the strong correlation among charged <span class="hlt">dust</span> is a source of dissipation and is responsible for the formation of the DA shock structures in such the opposite-polarity <span class="hlt">dust</span> plasma medium. The parametric regimes for the existence of the DA shock structures (associated withmore » electrostatic and gravitational potentials) and their basic properties (viz., polarity, amplitude, width, and speed) are found to be significantly modified by the combined effects of positively charged <span class="hlt">dust</span> <span class="hlt">component</span>, self-gravitational field, and strong correlation among charged <span class="hlt">dust</span>. The implications of our results in different space plasma environments and laboratory plasma devices are briefly discussed.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23722090','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23722090"><span><span class="hlt">Dust</span> fallout in Kuwait city: deposition and characterization.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Al-Awadhi, Jasem M; Alshuaibi, Arafat A</p> <p>2013-09-01</p> <p><span class="hlt">Dust</span> fallouts in Kuwait city was monitored on monthly basis during the period from March 2011 to February 2012 at 10 locations. The results of this study reveal that: (1) monthly <span class="hlt">dust</span> deposition rates ranged from 0.002 to 0.32 kg/m(2) with average deposition rate of 0.053 kg/m(2) and annual average deposition rate of 0.59 kg/m(2), ranking the first out of 56 <span class="hlt">dust</span> deposition rates observed throughout the world; (2) on average, about 55.9% of the settled <span class="hlt">dust</span> have fine to very fine sand fraction sizes, while silt and clay comprise an average of 37.4 and 1.4% of the total sample, respectively; (3) the concentrations for Zn and Mo out of 15 other elements analyzed from the <span class="hlt">dust</span> were up to 11 times higher than their soil background values in Kuwait, while Pb and Ni were about seven times higher; (4) Mo, Ni, Pb and Zn show maximum enrichment relative to the upper continental crustal <span class="hlt">component</span> (Mn); (5) Sr, Zr and Zn show highest concretions among all collected samples; and (6) quartz and calcite were the dominant minerals in the <span class="hlt">dust</span> samples. The distribution of the heavy metals in <span class="hlt">dust</span> seems to be controlled mainly by the land uses and the volume of traffic emissions. Copyright © 2013 Elsevier B.V. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24275707','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24275707"><span>Desert <span class="hlt">dust</span> and human health disorders.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Goudie, Andrew S</p> <p>2014-02-01</p> <p><span class="hlt">Dust</span> storms may originate in many of the world's drylands and have an effect not only on human health in the drylands themselves but also in downwind environments, including some major urban centres, such as Phoenix, Kano, Athens, Madrid, Dubai, Jedda, Tehran, Jaipur, Beijing, Shanghai, Seoul, Taipei, Tokyo, Sydney, Brisbane and Melbourne. In some parts of the world <span class="hlt">dust</span> storms occur frequently throughout the year. They can transport particulate material, pollutants, and potential allergens over thousands of km from source. The main sources include the Sahara, central and eastern Asia, the Middle East, and parts of the western USA. In some parts of the world, though not all, the frequency of <span class="hlt">dust</span> storms is changing in response to land use and climatic changes, and in such locations the health implications may become more severe. Data on the PM10 and P2.5 loadings of <span class="hlt">dust</span> events are discussed, as are various pollutants (heavy metals, pesticides, etc.) and biological <span class="hlt">components</span> (spores, fungi, bacteria, etc.). Particulate loadings can far exceed healthy levels. Among the human health effects of <span class="hlt">dust</span> storms are respiratory disorders (including asthma, tracheitis, pneumonia, allergic rhinitis and silicosis) cardiovascular disorders (including stroke), conjunctivitis, skin irritations, meningococcal meningitis, valley fever, diseases associated with toxic algal blooms and mortality and injuries related to transport accidents. © 2013.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22253570-ray-spectroscopy-warm-hot-electron-components-caprice-source-plasma-eis-testbench-gsi','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22253570-ray-spectroscopy-warm-hot-electron-components-caprice-source-plasma-eis-testbench-gsi"><span>X-ray spectroscopy of <span class="hlt">warm</span> and hot electron <span class="hlt">components</span> in the CAPRICE source plasma at EIS testbench at GSI</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Mascali, D., E-mail: davidmascali@lns.infn.it; Celona, L.; Castro, G.</p> <p>2014-02-15</p> <p>An experimental campaign aiming to detect X radiation emitted by the plasma of the CAPRICE source – operating at GSI, Darmstadt – has been carried out. Two different detectors (a SDD – Silicon Drift Detector and a HpGe – hyper-pure Germanium detector) have been used to characterize the <span class="hlt">warm</span> (2–30 keV) and hot (30–500 keV) electrons in the plasma, collecting the emission intensity and the energy spectra for different pumping wave frequencies and then correlating them with the CSD of the extracted beam measured by means of a bending magnet. A plasma emissivity model has been used to extract themore » plasma density along the cone of sight of the SDD and HpGe detectors, which have been placed beyond specific collimators developed on purpose. Results show that the tuning of the pumping frequency considerably modifies the plasma density especially in the <span class="hlt">warm</span> electron population domain, which is the <span class="hlt">component</span> responsible for ionization processes: a strong variation of the plasma density near axis region has been detected. Potential correlations with the charge state distribution in the plasma are explored.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19324762','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19324762"><span>Why tropical forest lizards are vulnerable to climate <span class="hlt">warming</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Huey, Raymond B; Deutsch, Curtis A; Tewksbury, Joshua J; Vitt, Laurie J; Hertz, Paul E; Alvarez Pérez, Héctor J; Garland, Theodore</p> <p>2009-06-07</p> <p>Biological impacts of climate <span class="hlt">warming</span> are predicted to increase with latitude, paralleling increases in <span class="hlt">warming</span>. However, the magnitude of impacts depends not only on the degree of <span class="hlt">warming</span> but also on the number of species at risk, their physiological sensitivity to <span class="hlt">warming</span> and their options for behavioural and physiological compensation. Lizards are useful for evaluating risks of <span class="hlt">warming</span> because their thermal biology is well studied. We conducted macrophysiological analyses of diurnal lizards from diverse latitudes plus focal species analyses of Puerto Rican Anolis and Sphaerodactyus. Although tropical lowland lizards live in environments that are <span class="hlt">warm</span> all year, macrophysiological analyses indicate that some tropical lineages (thermoconformers that live in forests) are active at low body temperature and are intolerant of <span class="hlt">warm</span> temperatures. Focal species analyses show that some tropical forest lizards were already experiencing stressful body temperatures in summer when studied several decades ago. Simulations suggest that <span class="hlt">warming</span> will not only further depress their physiological performance in summer, but will also enable <span class="hlt">warm</span>-adapted, open-habitat competitors and predators to invade forests. Forest lizards are key <span class="hlt">components</span> of tropical ecosystems, but appear vulnerable to the cascading physiological and ecological effects of climate <span class="hlt">warming</span>, even though rates of tropical <span class="hlt">warming</span> may be relatively low.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2677251','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2677251"><span>Why tropical forest lizards are vulnerable to climate <span class="hlt">warming</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Huey, Raymond B.; Deutsch, Curtis A.; Tewksbury, Joshua J.; Vitt, Laurie J.; Hertz, Paul E.; Álvarez Pérez, Héctor J.; Garland, Theodore</p> <p>2009-01-01</p> <p>Biological impacts of climate <span class="hlt">warming</span> are predicted to increase with latitude, paralleling increases in <span class="hlt">warming</span>. However, the magnitude of impacts depends not only on the degree of <span class="hlt">warming</span> but also on the number of species at risk, their physiological sensitivity to <span class="hlt">warming</span> and their options for behavioural and physiological compensation. Lizards are useful for evaluating risks of <span class="hlt">warming</span> because their thermal biology is well studied. We conducted macrophysiological analyses of diurnal lizards from diverse latitudes plus focal species analyses of Puerto Rican Anolis and Sphaerodactyus. Although tropical lowland lizards live in environments that are <span class="hlt">warm</span> all year, macrophysiological analyses indicate that some tropical lineages (thermoconformers that live in forests) are active at low body temperature and are intolerant of <span class="hlt">warm</span> temperatures. Focal species analyses show that some tropical forest lizards were already experiencing stressful body temperatures in summer when studied several decades ago. Simulations suggest that <span class="hlt">warming</span> will not only further depress their physiological performance in summer, but will also enable <span class="hlt">warm</span>-adapted, open-habitat competitors and predators to invade forests. Forest lizards are key <span class="hlt">components</span> of tropical ecosystems, but appear vulnerable to the cascading physiological and ecological effects of climate <span class="hlt">warming</span>, even though rates of tropical <span class="hlt">warming</span> may be relatively low. PMID:19324762</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_16 --> <div id="page_17" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="321"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27117151','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27117151"><span><span class="hlt">Dust</span> aerosol properties and radiative forcing observed in spring during 2001-2014 over urban Beijing, China.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Yu, Xingna; Lü, Rui; Kumar, K Raghavendra; Ma, Jia; Zhang, Qiuju; Jiang, Yilun; Kang, Na; Yang, Suying; Wang, Jing; Li, Mei</p> <p>2016-08-01</p> <p>The ground-based characteristics (optical and radiative properties) of <span class="hlt">dust</span> aerosols measured during the springtime between 2001 and 2014 were investigated over urban Beijing, China. The seasonal averaged aerosol optical depth (AOD) during spring of 2001-2014 was about 0.78 at 440 nm. During <span class="hlt">dust</span> days, higher AOD occurred associated with lower Ångström exponent (AE). The mean AE440-870 in the springtime was about 1.0, indicating dominance of fine particles over the region. The back-trajectory analysis revealed that the <span class="hlt">dust</span> was transported from the deserts of Inner Mongolia and Mongolia arid regions to Beijing. The aerosol volume size distribution showed a bimodal distribution pattern, with its highest peak observed in coarse mode for all episodes (especially for <span class="hlt">dust</span> days with increased volume concentration). The single scattering albedo (SSA) increased with wavelength on <span class="hlt">dust</span> days, indicating the presence of more scattering particles. Furthermore, the complex parts (real and imaginary) of refractive index showed distinct characteristics with lower imaginary values (also scattering) on <span class="hlt">dust</span> days. The shortwave (SW; 0.2-4.0 μm) and longwave (LW; 4-100 μm) aerosol radiative forcing (ARF) values were computed from the Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART) model both at the top of atmosphere (TOA) and the bottom of atmosphere (BOA) during <span class="hlt">dust</span> and non-<span class="hlt">dust</span> (<span class="hlt">dust</span> free) days, and the corresponding heating rates and forcing efficiencies were also estimated. The SW (LW) ARF, therefore, produced significant cooling (<span class="hlt">warming</span>) effects at both the TOA and the BOA over Beijing.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5482553','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5482553"><span>High particulate iron(II) content in glacially sourced <span class="hlt">dusts</span> enhances productivity of a model diatom</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Shoenfelt, Elizabeth M.; Sun, Jing; Winckler, Gisela; Kaplan, Michael R.; Borunda, Alejandra L.; Farrell, Kayla R.; Moreno, Patricio I.; Gaiero, Diego M.; Recasens, Cristina; Sambrotto, Raymond N.; Bostick, Benjamin C.</p> <p>2017-01-01</p> <p>Little is known about the bioavailability of iron (Fe) in natural <span class="hlt">dusts</span> and the impact of <span class="hlt">dust</span> mineralogy on Fe utilization by photosynthetic organisms. Variation in the supply of bioavailable Fe to the ocean has the potential to influence the global carbon cycle by modulating primary production in the Southern Ocean. Much of the <span class="hlt">dust</span> deposited across the Southern Ocean is sourced from South America, particularly Patagonia, where the waxing and waning of past and present glaciers generate fresh glaciogenic material that contrasts with aged and chemically weathered nonglaciogenic sediments. We show that these two potential sources of modern-day <span class="hlt">dust</span> are mineralogically distinct, where glaciogenic <span class="hlt">dust</span> sources contain mostly Fe(II)-rich primary silicate minerals, and nearby nonglaciogenic <span class="hlt">dust</span> sources contain mostly Fe(III)-rich oxyhydroxide and Fe(III) silicate weathering products. In laboratory culture experiments, Phaeodactylum tricornutum, a well-studied coastal model diatom, grows more rapidly, and with higher photosynthetic efficiency, with input of glaciogenic particulates compared to that of nonglaciogenic particulates due to these differences in Fe mineralogy. Monod nutrient accessibility models fit to our data suggest that particulate Fe(II) content, rather than abiotic solubility, controls the Fe bioavailability in our Fe fertilization experiments. Thus, it is possible for this diatom to access particulate Fe in <span class="hlt">dusts</span> by another mechanism besides uptake of unchelated Fe (Fe′) dissolved from particles into the bulk solution. If this capability is widespread in the Southern Ocean, then <span class="hlt">dusts</span> deposited to the Southern Ocean in cold glacial periods are likely more bioavailable than those deposited in <span class="hlt">warm</span> interglacial periods. PMID:28691098</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000PhyS...61..485I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000PhyS...61..485I"><span>Parametric Excitation of Electrostatic <span class="hlt">Dust</span>-Modes by Ion-Cyclotron Waves in a Dusty Plasma</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Islam, M. K.; Salahuddin, M.; Ferdous, T.; Salimullah, M.</p> <p></p> <p>A large amplitude electrostatic ion-cyclotron wave propagating through a magnetized and collisional dusty plasma undergoes strong parametric instability off the low-frequency <span class="hlt">dust</span>-modes. The presence of the <span class="hlt">dust-component</span> has effect on the nonlinear coupling via the <span class="hlt">dust</span>-modes. The ion-neutral collisions are seen to have significant effect on the damping and consequent overall growth of the parametric excitation process.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/1176828-regional-modeling-dust-mass-balance-radiative-forcing-over-east-asia-using-wrf-chem','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1176828-regional-modeling-dust-mass-balance-radiative-forcing-over-east-asia-using-wrf-chem"><span>Regional Modeling of <span class="hlt">Dust</span> Mass Balance and Radiative Forcing over East Asia using WRF-Chem</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Chen, Siyu; Zhao, Chun; Qian, Yun</p> <p></p> <p>The Weather Research and Forecasting model with Chemistry (WRF-Chem) is used to investigate the seasonal and annual variations of mineral <span class="hlt">dust</span> over East Asia during 2007-2011, with a focus on the <span class="hlt">dust</span> mass balance and radiative forcing. A variety of measurements from in-stu and satellite observations have been used to evaluate simulation results. Generally, WRF-Chem reproduces not only the column variability but also the vertical profile and size distribution of mineral <span class="hlt">dust</span> over and near the <span class="hlt">dust</span> source regions of East Asia. We investigate the <span class="hlt">dust</span> lifecycle and the factors that control the seasonal and spatial variations of <span class="hlt">dust</span> massmore » balance and radiative forcing over the seven sub-regions of East Asia, i.e. source regions, the Tibetan Plateau, Northern China, Southern China, the ocean outflow region, and Korea-Japan regions. Results show that, over the source regions, transport and dry deposition are the two dominant sinks. Transport contributes to ~30% of the <span class="hlt">dust</span> sink over the source regions. <span class="hlt">Dust</span> results in a surface cooling of up to -14 and -10 W m-2, atmospheric <span class="hlt">warming</span> of up to 20 and 15 W m-2, and TOA cooling of -5 and -8 W m-2 over the two major <span class="hlt">dust</span> source regions of East Asia, respectively. Over the Tibetan Plateau, transport is the dominant source with a peak in summer. Over identified outflow regions, maximum <span class="hlt">dust</span> mass loading in spring is contributed by the transport. Dry and wet depositions are the comparably dominant sinks, but wet deposition is larger than dry deposition over the Korea-Japan region, particularly in spring (70% versus 30%). The WRF-Chem simulations can generally capture the measured features of <span class="hlt">dust</span> aerosols and its radaitve properties and <span class="hlt">dust</span> mass balance over East Asia, which provides confidence for use in further investigation of <span class="hlt">dust</span> impact on climate over East Asia.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016cm15.book...83C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016cm15.book...83C"><span>Characterization of Sintering <span class="hlt">Dust</span>, Blast Furnace <span class="hlt">Dust</span> and Carbon Steel Electric Arc Furnace <span class="hlt">Dust</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chang, Feng; Wu, Shengli; Zhang, Fengjie; Lu, Hua; Du, Kaiping</p> <p></p> <p>In order to make a complete understanding of steel plant metallurgical <span class="hlt">dusts</span> and to realize the goal of zero-waste, a study of their properties was undertaken. For these purposes, samples of two sintering <span class="hlt">dusts</span> (SD), two blast furnace <span class="hlt">dusts</span> (BFD), and one electric arc furnace <span class="hlt">dust</span> (EAFD) taken from the regular production process were subjected to a series of tests. The tests were carried out by using granulometry analysis, chemical analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy via SEM (EDS), and Fourier transform infrared spectroscopy (FTIR). The dominant elements having an advantage of reuse are Fe, K, Cl, Zn, C. The dominant mineralogical phases identified in sintering <span class="hlt">dust</span> are KCl, Fe2O3, CaCO3, CaMg(CO3)2, NaCl, SiO2. Mineralogical phases exist in blast furnace <span class="hlt">dust</span> are Fe2O3, Fe3O4, with small amount of KCl and kaolinite coexist. While in electric arc furnace <span class="hlt">dust</span>, Fe3O4, ZnFe2O4, CaCO3, CaO, Ca(OH)2 are detected.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..14.5802M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..14.5802M"><span>Does the presence of cosmic <span class="hlt">dust</span> influence the displacement of the Earth's Magnetopause?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mann, I.; Hamrin, M.</p> <p>2012-04-01</p> <p>In a recent paper Treumann and Baumjohann propose that <span class="hlt">dust</span> particles in interplanetary space occasionally cause large compressions of the magnetopause that, in the absence of coronal mass ejections, are difficult to explain by other mechanisms (R.A. Treumann and W. Baumjohann, Ann. Geophys. 30, 119-130, 2012). They suggest that enhanced <span class="hlt">dust</span> number density raises the contribution of the <span class="hlt">dust</span> <span class="hlt">component</span> to the solar wind dynamical pressure and hence to the pressure balance that determines the extension of the magnetopause. They quantify the influence of the <span class="hlt">dust</span> <span class="hlt">component</span> in terms of a variation of the magnetopause stagnation point distance. As a possible event to trigger the compressions they propose the encounters with meteoroid <span class="hlt">dust</span> streams along Earth's orbit. We investigate the conditions under which these compressions may occur. The estimate by Treumann and Baumjohann of the magnetopause variation presupposes that the <span class="hlt">dust</span> particles have reached solar wind speed. Acceleration by electromagnetic forces is efficient in the solar wind for <span class="hlt">dust</span> particles that have a sufficiently large ratio of surface charge to mass (Mann et al. Plasma Phys. Contr. Fusion, Vol. 52, 124012, 2010). This applies to small <span class="hlt">dust</span> particles that contribute little to the total <span class="hlt">dust</span> mass in meteoroid streams. The major fraction of <span class="hlt">dust</span> particles that reach high speed in the solar wind are nanometer-sized <span class="hlt">dust</span> particles that form and are accelerated in the inner solar system (Czechowski and Mann, ApJ, Vol. 714, 89, 2010). Observations suggest that the flux of these nanodust particles near 1 AU is highly time-variable (Meyer-Vernet, et al. Solar Physics, Vol. 256, 463, 2009). We estimate a possible variation of the magnetopause stagnation point distance caused by these nanodust fluxes and by the <span class="hlt">dust</span> associated to meteoroid streams. We conclude that the Earth's encounters with meteoroid <span class="hlt">dust</span> streams are not likely to strongly influence the magnetopause according to the proposed effect. We</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018AtmEn.173..265N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018AtmEn.173..265N"><span>Impacts of climate and synoptic fluctuations on <span class="hlt">dust</span> storm activity over the Middle East</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Namdari, Soodabeh; Karimi, Neamat; Sorooshian, Armin; Mohammadi, GholamHasan; Sehatkashani, Saviz</p> <p>2018-01-01</p> <p><span class="hlt">Dust</span> events in the Middle East are becoming more frequent and intense in recent years with impacts on air quality, climate, and public health. In this study, the relationship between <span class="hlt">dust</span>, as determined from Aerosol Optical Depth (AOD) and meteorological parameters (precipitation, temperature, pressure and wind field) are examined using monthly data from 2000 to 2015 for desert areas in two areas, Iraq-Syria and Saudi Arabia. Bivariate regression analysis between monthly temperature data and AOD reveals a high correlation for Saudi Arabia (R = 0.72) and Iraq-Syria (R = 0.64). Although AOD and precipitation are correlated in February, March and April, the relationship is more pronounced on annual timescales. The opposite is true for the relationship between temperature and AOD, which is evident more clearly on monthly time scales, with the highest temperatures and AOD typically between August and September. Precipitation data suggest that long-term reductions in rainfall promoted lower soil moisture and vegetative cover, leading to more intense <span class="hlt">dust</span> emissions. Superimposed on the latter effect are more short term variations in temperature exacerbating the influence on the <span class="hlt">dust</span> storm genesis in hot periods such as the late <span class="hlt">warm</span> season of the year. Case study analysis of March 2012 and March 2014 shows the impact of synoptic systems on <span class="hlt">dust</span> emissions and transport in the study region. <span class="hlt">Dust</span> storm activity was more intense in March 2012 as compared to March 2014 due to enhanced atmospheric turbulence intensifying surface winds.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A23K..06R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A23K..06R"><span>Origin-Dependent Variations in the Atmospheric Microbiome in Eastern Mediterranean <span class="hlt">Dust</span> Storms</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rudich, Y.; Gat, D.</p> <p>2017-12-01</p> <p>Microorganisms carried by <span class="hlt">dust</span> storms are transported through the atmosphere and may affect human health and the functionality of microbial communities in various environments. Characterizing the <span class="hlt">dust</span>-borne microbiome in <span class="hlt">dust</span> storms of different origins, or that followed different trajectories, provides valuable data to improve our understanding of global health and environmental impacts. We present a comparative study on the diversity of <span class="hlt">dust</span>- borne bacterial communities in <span class="hlt">dust</span> storms from three distinct origins—North Africa, Syria and Saudi Arabia—and compare them with local bacterial communities sampled on clear days, all collected at a single location, in Israel. Storms from different <span class="hlt">dust</span> origins exhibited distinct bacterial communities, with signature bacterial taxa for each source. <span class="hlt">Dust</span> storms were characterized by a lower abundance of selected antibiotic resistance genes (ARGs) compared with ambient <span class="hlt">dust</span>, asserting that the origin of these genes is local, possibly anthropogenic. With the progression of the storm, the storm-borne bacterial community showed increasing resemblance to ambient <span class="hlt">dust</span>, suggesting mixing with local <span class="hlt">dust</span>. We will also discuss how exposure to <span class="hlt">dust</span> containing biological <span class="hlt">components</span> affect lung epithelial cells. These results show, for the first time, that <span class="hlt">dust</span> storms from different sources display distinct bacterial communities, suggesting possible distinct effects on the environment and public health.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFMPP33C1575X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFMPP33C1575X"><span>Eastern Equatorial Pacific <span class="hlt">Dust</span> Provenance on Deglacial Timescales</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xie, R.; Marcantonio, F.</p> <p>2008-12-01</p> <p>Changing patterns of eolian <span class="hlt">dust</span> deposition preserved in deep-sea sediments have the potential to provide us with a better understanding of changes in past atmospheric circulation. One way in which to determine the provenance of <span class="hlt">dust</span> in deep-sea sediments is to use radiogenic isotopic tracers which can fingerprint potential <span class="hlt">dust</span> sources. Models (e.g., [1]) suggest that sources of <span class="hlt">dust</span> to the Eastern Equatorial Pacific (EEP) are from areas as diverse as Asia, North, Central, and South America, and, perhaps, even Africa. Here, we investigate spatial and temporal changes in the provenance of the eolian <span class="hlt">component</span> in the EEP by measuring Pb, Sr, and Nd isotope ratios in <span class="hlt">dust</span> extracted from sediments along a transect at 110oW from 7oN to 3oS (ODP sites 853 - 848). In this region, although fluxes of <span class="hlt">dust</span> were higher during the last glacial maximum (LGM) than those in the Holocene by up to 100%, the glacial flux of <span class="hlt">dust</span> displayed a shallower meridional gradient [2]. However, it is unclear whether this shallower gradient is due to a mean southerly displacement of the Intertropical Convergence Zone (ITCZ). Most of the <span class="hlt">dust</span> trying to pass through the ITCZ will be scavenged and rained out at the ITCZ. Along the meridional gradient, therefore, temporal variations in the Pb, Sr, and Nd isotopic fingerprints of the distinct <span class="hlt">dust</span> sources will determine the extent to which the position of the ITCZ changes on deglacial timescales. [1] Mahowald et al., 2005, Global Biogeochemical Cycles 19, GB4025. [2] McGee et al., 2007, EPSL 257, 215-230.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29061971','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29061971"><span>The implications of <span class="hlt">dust</span> ice nuclei effect on cloud top temperature in a complex mesoscale convective system.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Li, Rui; Dong, Xue; Guo, Jingchao; Fu, Yunfei; Zhao, Chun; Wang, Yu; Min, Qilong</p> <p>2017-10-23</p> <p>Mineral <span class="hlt">dust</span> is the most important natural source of atmospheric ice nuclei (IN) which may significantly mediate the properties of ice cloud through heterogeneous nucleation and lead to crucial impacts on hydrological and energy cycle. The potential <span class="hlt">dust</span> IN effect on cloud top temperature (CTT) in a well-developed mesoscale convective system (MCS) was studied using both satellite observations and cloud resolving model (CRM) simulations. We combined satellite observations from passive spectrometer, active cloud radar, lidar, and wind field simulations from CRM to identify the place where ice cloud mixed with <span class="hlt">dust</span> particles. For given ice water path, the CTT of <span class="hlt">dust</span>-mixed cloud is warmer than that in relatively pristine cloud. The probability distribution function (PDF) of CTT for <span class="hlt">dust</span>-mixed clouds shifted to the warmer end and showed two peaks at about -45 °C and -25 °C. The PDF for relatively pristine cloud only show one peak at -55 °C. Cloud simulations with different microphysical schemes agreed well with each other and showed better agreement with satellite observations in pristine clouds, but they showed large discrepancies in <span class="hlt">dust</span>-mixed clouds. Some microphysical schemes failed to predict the <span class="hlt">warm</span> peak of CTT related to heterogeneous ice formation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016Geomo.273..269D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016Geomo.273..269D"><span>Identification of debris-flow hazards in <span class="hlt">warm</span> deserts through analyzing past occurrences: Case study in South Mountain, Sonoran Desert, USA</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dorn, Ronald I.</p> <p>2016-11-01</p> <p>After recognition that debris flows co-occur with human activities, the next step in a hazards analysis involves estimating debris-flow probability. Prior research published in this journal in 2010 used varnish microlamination (VML) dating to determine a minimum occurrence of 5 flows per century over the last 8100 years in a small mountain range of South Mountain adjacent to neighborhoods of Phoenix, Arizona. This analysis led to the conclusion that debris flows originating in small mountain ranges in arid regions like the Sonoran Desert could pose a hazard. Two major precipitation events in the summer of 2014 generated 35 debris flows in the same study area of South Mountain-providing support for the importance of probability analysis as a key step in a hazards analysis in <span class="hlt">warm</span> desert settings. Two distinct mechanisms generated the 2014 debris flows: intense precipitation on steep slopes in the first storm; and a firehose effect whereby runoff from the second storm was funneled rapidly by cleaned-out debris-flow chutes to remobilize Pleistocene debris-flow deposits. When compared to a global database on debris flows, the 2014 storms were among the most intense to generate desert debris flows - indicating that storms of lesser intensity are capable of generating debris flows in <span class="hlt">warm</span> desert settings. The 87Sr/86Sr analyses of fines and clasts in South Mountain debris flows of different ages reveal that desert <span class="hlt">dust</span> supplies the fines. Thus, wetter climatic periods of intense rock decay are not needed to resupply desert slopes with fines; instead, a combination of <span class="hlt">dust</span> deposition supplying fines and dirt cracking generating coarse clasts can re-arm chutes in a <span class="hlt">warm</span> desert setting with abundant <span class="hlt">dust</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A33F2442Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A33F2442Z"><span><span class="hlt">Dust</span> input in the formation of rock varnish from the Dry Valleys (Antarctica)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zerboni, A.; Guglielmin, M.</p> <p>2017-12-01</p> <p>Rock varnish is a glossy, yellowish to dark brown coating that covers geomorphically stable, aerially exposed rock surfaces and landforms in <span class="hlt">warm</span> and cold arid lands. In <span class="hlt">warm</span> deserts, rock varnish consists of clay minerals, Mn-Fe oxides/hydroxides, and Si+alkalis <span class="hlt">dust</span>; it occasionally containis sulphates, phosphates, and organic remains. In Antarctica, rock varnish developed on a variety of bedrocks and has been described being mostly formed of Si, Al, Fe, and sulphates, suggesting a double process in its formation, including biomineralization alternated to <span class="hlt">dust</span> accretion. We investigated rock coatings developed on sandstones outcropping in the Dry Valleys of Antarctica and most of the samples highlithed an extremely complex varnish structure, alternating tihn layer of different chemical compostion. Optical microscope evidenced the occurrence of highly birefringent minerals, occasionally thinly laminated and consisitng of Si and Al-rich minerals (clays). These are interlayered by few micron-thick dark lenses and continous layers. The latter are well evident under the scanning electron microscope and chemical analysis confirmed that they consist of different kinds of sulphates; jarosite is the most represented species, but gypsum crystals were also found. Fe-rich hypocoatings and intergranula crusts were also detected, sometimes preserving the shape of the hyphae they have replaced. Moreover, small weathering pits on sandstone surface display the occurrence of an amorphous, dark Mn/Fe-rich rock varnish. The formation of rock varnish in the Dry Valleys is a complex process, which required the accretion of airborne <span class="hlt">dust</span> of variable composition and subsequent recrystallization of some constituent, possibly promoted by microorganisms. In particualr, the formation of sulphates seems to preserve the memory of S-rich <span class="hlt">dust</span> produced by volcanic eruptions. On the contrary, the formation of Mn-rich varnish should be in relation with the occurrence of higher environmental</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFM.A23D1566L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFM.A23D1566L"><span>Simulation of Asia <span class="hlt">Dust</span> and Cloud Interaction Over Pacific Ocean During Pacdex</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Long, X.; Huang, J.; Cheng, C.; Wang, W.</p> <p>2007-12-01</p> <p>The effect of <span class="hlt">dust</span> plume on the Pacific cloud systems and the associated radiative forcing is an outstanding problem for understanding climate change. Many studies showing that <span class="hlt">dust</span> aerosol might be a good absorber for solar radiation, at the same time <span class="hlt">dust</span> aerosols could affect the cloud's formation and precipitation by its capability as cloud condensation nuclei (CCN) and ice forming nuclei (IFN). But the role of aerosols in clouds and precipitation is very complex. Simulation of interaction between cloud and <span class="hlt">dust</span> aerosols requires recognition that the aerosol cloud system comprises coupled <span class="hlt">components</span> of dynamics, aerosol and cloud microphysics, radiation processes. In this study, we investigated the interaction between <span class="hlt">dust</span> aerosols and cloud with WRF which coupled with detailed cloud microphysics processes and <span class="hlt">dust</span> process. The observed data of SACOL (Semi-Arid Climate and Environment Observatory of Lanzhou University) and PACDEX (Pacific <span class="hlt">Dust</span> Experiment) is used as the initialization which include the vertical distributions and concentration of <span class="hlt">dust</span> particles. Our results show that <span class="hlt">dust</span> aerosol not only impacts cloud microphysical processes but also cloud microstructure; <span class="hlt">Dust</span> aerosols can act as effective ice nuclei and intensify the ice-forming processes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004cosp...35.4460C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004cosp...35.4460C"><span>Martian <span class="hlt">Dust</span> Cycle</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cantor, B. A.; James, P. B.</p> <p></p> <p>The Mars Observer Camera (MOC), aboard Mars Global Surveyor (MGS), has completed approximately 3 consecutive Martian years of global monitoring, since entering its mapping orbit on March 9, 1999. MOC observations have shown the important role that <span class="hlt">dust</span> devils and <span class="hlt">dust</span> storms play in the Martian <span class="hlt">dust</span> cycle on time scales ranging from semi-diurnally to interannually. These <span class="hlt">dust</span> events have been observed across much of the planet from the depths of Hellas basin to the summit of Arsia Mons and range in size from10s of meters across (<span class="hlt">dust</span> devils) to planet encircling (global <span class="hlt">dust</span> veils). Though <span class="hlt">dust</span> devils occur throughout most of the Martian year, each hemisphere has a "<span class="hlt">dust</span> devil season" that generally follows the subsolar latitude and appears to be repeatable from year-to-year. An exception is NW Amazonis, which has frequent, large <span class="hlt">dust</span> devils throughout northern spring and summer. MOC observations show no evidence that <span class="hlt">dust</span> devils cause or lead to <span class="hlt">dust</span> storms, however, observations do suggest that <span class="hlt">dust</span> storms can initiate <span class="hlt">dust</span> devil activity. <span class="hlt">Dust</span> devils also might play a role in maintaining the low background <span class="hlt">dust</span> opacity of the Martian atmosphere. <span class="hlt">Dust</span> storms occur almost daily with few exceptions, with 1000s occurring each year in the present Martian environment, dispelling the notion of a "Classical <span class="hlt">Dust</span> Storm Season". However, there does appear to be an annual <span class="hlt">dust</span> storm cycle, with storms developing in specific locations during certain seasons and that some individual storm events are repeatable from year-to-year. The majority of storms develop near the receding seasonal polar cap edge or along the corresponding polar hood boundaries in their respective hemispheres, but they also occur in the northern plains, the windward side of the large shield volcanoes, and in low laying regions such as Hellas, Argyre, and Chryse. The rarest of <span class="hlt">dust</span> events are the "Great Storms" or "Global Events", of which only 6 (4 "planet encircling" and 2 "global") have been observed</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22304082-dust-acoustic-solitary-shock-excitations-thomas-fermi-magnetoplasma','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22304082-dust-acoustic-solitary-shock-excitations-thomas-fermi-magnetoplasma"><span><span class="hlt">Dust</span> acoustic solitary and shock excitations in a Thomas-Fermi magnetoplasma</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Rahim, Z.; Qamar, A.; National Center for Physics</p> <p></p> <p>The linear and nonlinear properties of <span class="hlt">dust</span>-acoustic waves are investigated in a collisionless Thomas-Fermi magnetoplasma, whose constituents are electrons, ions, and negatively charged <span class="hlt">dust</span> particles. At <span class="hlt">dust</span> time scale, the electron and ion number densities follow the Thomas-Fermi distribution, whereas the <span class="hlt">dust</span> <span class="hlt">component</span> is described by the classical fluid equations. A linear dispersion relation is analyzed to show that the wave frequencies associated with the upper and lower modes are enhanced with the variation of <span class="hlt">dust</span> concentration. The effect of the latter is seen more strongly on the upper mode as compared to the lower mode. For nonlinear analysis, wemore » obtain magnetized Korteweg-de Vries (KdV) and Zakharov-Kuznetsov (ZK) equations involving the <span class="hlt">dust</span>-acoustic solitary waves in the framework of reductive perturbation technique. Furthermore, the shock wave excitations are also studied by allowing dissipation effects in the model, leading to the Korteweg-de Vries-Burgers (KdVB) and ZKB equations. The analysis reveals that the <span class="hlt">dust</span>-acoustic solitary and shock excitations in a Thomas-Fermi plasma are strongly influenced by the plasma parameters, e.g., <span class="hlt">dust</span> concentration, <span class="hlt">dust</span> temperature, obliqueness, magnetic field strength, and <span class="hlt">dust</span> fluid viscosity. The present results should be important for understanding the solitary and shock excitations in the environments of white dwarfs or supernova, where <span class="hlt">dust</span> particles can exist.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20070006527','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20070006527"><span>The Lunar Environment: Determining the Health Effects of Exposure to Moon <span class="hlt">Dusts</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Khan-Mayberry, Noreen</p> <p>2007-01-01</p> <p>The Earth s moon presents a hostile environment in which to live and work. There is no atmosphere to protect its surface from the ravages of solar wind and micrometeorite impacts. As a result, the moon s surface is covered with a thin layer of fine, charged, reactive <span class="hlt">dust</span> capable of entering habitats and vehicle compartments, where it can result in crewmember health problems. During the Apollo missions, lunar <span class="hlt">dusts</span> were introduced into the crew vehicle, resulting in direct exposure and occasional reports of respiratory, dermal and ocular irritation. In order to study the toxicological effects of lunar <span class="hlt">dust</span>, NASA formed the Lunar Airborne <span class="hlt">Dust</span> Toxicity Advisory Group (LADTAG). This interdisciplinary group is comprised of leading experts in space toxicology, lunar geology, space medicine and biomedical research. LADTAG has demonstrated that lunar soil contains several types of reactive <span class="hlt">dusts</span>, including an extremely fine respirable <span class="hlt">component</span>. These <span class="hlt">dusts</span> have highly reactive surfaces in the lunar environment; the grains contain surface coatings which are generated by vapor phases formed by hypervelocity impact of micrometeorites. This unique class of <span class="hlt">dusts</span> has surface properties that are unlike any Earth based analog. These distinctive properties are why lunar <span class="hlt">dusts</span> are of great toxicological interest. Understanding how these reactive <span class="hlt">components</span> behave "biochemically" in a moisture-rich pulmonary environment will aid in determining how toxic these particles are to humans. The data obtained from toxicological examination of lunar <span class="hlt">dusts</span> will determine the human risk criteria for lunar <span class="hlt">dust</span> exposure and produce a lunar health standard. LADTAG s analysis of lunar <span class="hlt">dusts</span> and lunar <span class="hlt">dust</span> simulants will include detailed lunar particle characterizations, determining the properties of particle activation, reactivation of lunar <span class="hlt">dust</span>, the process of <span class="hlt">dust</span> passivation and discerning the pathology of lunar <span class="hlt">dust</span> exposure via inhalation, intratracheal instillation, cell culture</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22663845-luminous-variable-stars-m31-m33-iv-luminous-blue-variables-candidate-lbvs-supergiants-warm-hypergiants-how-tell-them-apart','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22663845-luminous-variable-stars-m31-m33-iv-luminous-blue-variables-candidate-lbvs-supergiants-warm-hypergiants-how-tell-them-apart"><span>Luminous and Variable Stars in M31 and M33. IV. Luminous Blue Variables, Candidate LBVs, B[e] Supergiants, and the <span class="hlt">Warm</span> Hypergiants: How to Tell Them Apart</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Humphreys, Roberta M.; Gordon, Michael S.; Hahn, David</p> <p></p> <p>In this series of papers we have presented the results of a spectroscopic survey of luminous stars in the nearby spirals M31 and M33. Here, we present spectroscopy of 132 additional stars. Most have emission-line spectra, including luminous blue variables (LBVs) and candidate LBVs, Fe ii emission line stars, the B[e] supergiants, and the <span class="hlt">warm</span> hypergiants. Many of these objects are spectroscopically similar and are often confused with each other. We examine their similarities and differences and propose the following guidelines that can be used to help distinguish these stars in future work. (1) The B[e] supergiants have emission linesmore » of [O i] and [Fe ii] in their spectra. Most of the spectroscopically confirmed sgB[e] stars also have <span class="hlt">warm</span> circumstellar <span class="hlt">dust</span> in their spectral energy distributions (SEDs). (2) Confirmed LBVs do not have the [O i] emission lines in their spectra. Some LBVs have [Fe ii] emission lines, but not all. Their SEDs show free–free emission in the near-infrared but no evidence for <span class="hlt">warm</span> <span class="hlt">dust</span> . Their most important and defining characteristic is the S Dor-type variability. (3) The <span class="hlt">warm</span> hypergiants spectroscopically resemble the LBVs in their dense wind state and the B[e] supergiants. However, they are very dusty. Some have [Fe ii] and [O i] emission in their spectra like the sgB[e] stars, but are distinguished by their A- and F-type absorption-line spectra. In contrast, the B[e] supergiant spectra have strong continua and few if any apparent absorption lines. Candidate LBVs should share the spectral characteristics of the confirmed LBVs with low outflow velocities and the lack of <span class="hlt">warm</span> circumstellar <span class="hlt">dust</span>.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUSM.A31A..10B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUSM.A31A..10B"><span>Reactive organic species on natural <span class="hlt">dust</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Batsaikhan, A.; Schoeler, H.; Williams, J.</p> <p>2008-05-01</p> <p>Annually 1000-3000 Tg mineral <span class="hlt">dust</span> aerosol are emitted into the atmosphere, and transported over the oceans from one continent to the other. During the transport <span class="hlt">dust</span> particles interact with <span class="hlt">components</span> in the marine atmosphere and also with seawater as they fall into the ocean. Increased methyl iodide concentrations were observed during a field campaign on the Atlantic Ocean when <span class="hlt">dust</span> storms occurred. Volatile halogenated organic compounds (VHOC) are photolyzed to produce reactive halogen species which are responsible for ozone depletion. An abiotic production mechanism for VHOC, involving humic-like substance (HULIS), iron and halide, was supposed to produce methyl iodide through the interaction of <span class="hlt">dust</span> particles with seawater as all necessary ingredients were present. The main goal of this study was to test this hypothesis and to further elucidate the process. For this, simple <span class="hlt">dust</span>-seawater addition experiments in headspace glasses were conducted in the laboratory, following a purge-and-trap GC-MS analysis of the headspace gas. <span class="hlt">Dust</span> samples were collected in the source regions in southern Algeria and the Gobi Desert and, as representatives for aeolian <span class="hlt">dust</span>, samples from Cape Verde Island and Lanzarote Island were used. To exclude the biological contribution, sterilized samples were also employed in this study. As assumed, methyl iodide was produced abiotically and the concentration increased tenfold after addition of Fe (III) within half an hour. Methylene chloride was also produced abiotically along with methyl iodide. In contrast to methyl iodide and methylene chloride, methyl chloride and isoprene were produced biologically, provided the production occurred after at least 24 hours of interaction of only non-sterilized samples with seawater. If the microorganisms responsible for the production of isoprene are common soil organisms found everywhere in the world, this process can be the reason for a hitherto not fully explained increase in atmospheric isoprene</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AtmEn.159...83W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AtmEn.159...83W"><span>Significant impacts of heterogeneous reactions on the chemical composition and mixing state of <span class="hlt">dust</span> particles: A case study during <span class="hlt">dust</span> events over northern China</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Zhe; Pan, Xiaole; Uno, Itsushi; Li, Jie; Wang, Zifa; Chen, Xueshun; Fu, Pingqing; Yang, Ting; Kobayashi, Hiroshi; Shimizu, Atsushi; Sugimoto, Nobuo; Yamamoto, Shigekazu</p> <p>2017-06-01</p> <p>The impact of heterogeneous reactions on the chemical <span class="hlt">components</span> and mixing state of <span class="hlt">dust</span> particles are investigated by observations and an air quality model over northern China between March 27, 2015 and April 2, 2015. Synergetic observations were conducted using a polarization optical particle counter (POPC), a depolarized two-wavelength Lidar and filter samples in Beijing. During this period, <span class="hlt">dust</span> plume passed through Beijing on March 28, and flew back on March 29 because of synoptic weather changes. Mineral <span class="hlt">dust</span> mixed with anthropogenic pollutants was simulated using the Nested Air Quality Prediction Modeling System (NAQPMS) to examine the role of heterogeneous processes on the <span class="hlt">dust</span>. A comparison of observations shows that the NAQPMS successfully reproduces the time series of the vertical profile, particulate matter concentration, and chemical <span class="hlt">components</span> of fine mode (diameter ≤ 2.5 μm) and coarse mode (2.5 μm < diameter ≤ 10 μm) particles. After considering the heterogeneous reactions, the simulated nitrate, ammonium, and sulfate are in better agreement with the observed values during this period. The modeling results with observations show that heterogeneous reactions are the major mechanisms producing nitrate reaching 19 μg/m3, and sulfate reaching 7 μg/m3, on coarse mode <span class="hlt">dust</span> particles, which were almost 100% of the coarse mode nitrate and sulfate. The heterogeneous reactions are also important for fine mode secondary aerosols, for producing 17% of nitrate and 11% of sulfate on fine mode <span class="hlt">dust</span> particles, with maximum mass concentrations of 6 μg/m3 and 4 μg/m3. In contrast, due to uptake of acid gases (e.g. HNO3 and SO2) by <span class="hlt">dust</span> particles, the fine mode anthropogenic ammonium nitrate and ammonium sulfate decreased. As a result, the total fine mode nitrate decreased with a maximum of 14 μg/m3, while the total fine mode sulfate increased with a maximum of 2 μg/m3. Because of heterogeneous reactions, 15% of fine mode secondary inorganic aerosols and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120017008','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120017008"><span>Tropical Atlantic <span class="hlt">Dust</span> and Smoke Aerosol Variabilities Related to the Madden-Julian Oscillation in MODIS and MISR Observations</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Guo, Yanjuan; Tian, Baijun; Kahn, Ralph A.; Kalashnikova, Olga; Wong, Sun; Waliser, Duane E.</p> <p>2012-01-01</p> <p>In this study, MODIS fine mode fraction and MISR non-spherical fraction are 2used to derive <span class="hlt">dust</span> and smoke AOT <span class="hlt">components</span> (tau(sub <span class="hlt">dust</span>) and tau(sub smoke)) over the tropical Atlantic, and their variabilities related to the Madden-Julian Oscillation (MJO) are then investigated. Both MODIS and MISR show a very similar <span class="hlt">dust</span> and smoke winter climatology. tau(sub <span class="hlt">dust</span>) is found to be the dominant aerosol <span class="hlt">component</span> over the tropical Atlantic while tau(sub smoke) is significantly smaller than tau(sub <span class="hlt">dust</span>). The daily MODIS and MISR tau(sub <span class="hlt">dust</span>) are overall highly correlated, with the correlation coefficients typically about 0.7 over the North Atlantic. The consistency between the MODIS and MISR <span class="hlt">dust</span> and smoke aerosol climatology and daily variations give us confidence to use these two data sets to investigate their relative contributions to the total AOT variation associated with the MJO. However, unlike the MISR <span class="hlt">dust</span> discrimination, which is based on particle shape retrievals, the smoke discrimination is less certain, based on assumed partitioning of maritime aerosol for both MISR and MODIS. The temporal evolution and spatial patterns of the tau(sub <span class="hlt">dust</span>) anomalies associated with the MJO are consistent between MODIS and MISR. The tau(sub <span class="hlt">dust</span>) anomalies are very similar to those of tau anomalies, and are of comparable magnitude. In contrast, the MJO-related tau(sub smoke) anomalies are rather small, and the tau(sub mar) anomalies are negligible. The consistency between the MODIS and MISR results suggests that <span class="hlt">dust</span> aerosol is the dominant <span class="hlt">component</span> on the intra-seasonal time scale over the tropical Atlantic Ocean.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_17 --> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A13J..07S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A13J..07S"><span>Chemistry and Photochemistry at the Surface of Urban Road <span class="hlt">Dust</span> and Photoactive Minerals</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Styler, S. A.; Abou-Ghanem, M.; Wickware, B.</p> <p>2017-12-01</p> <p>Each year, over a billion tons of <span class="hlt">dust</span> are released into the atmosphere from arid regions. After its emission, <span class="hlt">dust</span> can undergo efficient long-range transport to urban centres, where it can interact with local pollution sources. Another source of <span class="hlt">dust</span> in urban regions is road <span class="hlt">dust</span> resuspension, which is the largest anthropogenic source of primary particulate matter in both Canada and the United States. Since <span class="hlt">dust</span> contains light-absorbing <span class="hlt">components</span>, including iron- and titanium-containing minerals, <span class="hlt">dust</span>-catalyzed photochemical processes have the potential to influence both the lifetime of pollutants present at the <span class="hlt">dust</span> surface and the composition of the surrounding atmosphere. To date, most studies of <span class="hlt">dust</span> photochemistry have focused on TiO2-mediated processes, and no studies have explored trace gas uptake at the surface of road <span class="hlt">dust</span>. Here, we present first results from aerosol and coated-wall flow tube investigations of ozone uptake at the surface of a suite of titanium-containing minerals and road <span class="hlt">dust</span> collected in Edmonton, Alberta. Together, this work represents a significant advance in our understanding of chemistry and photochemistry at realistic environmental interfaces.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1915759O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1915759O"><span>Distribution of <span class="hlt">dust</span> during two <span class="hlt">dust</span> storms in Iceland</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ösp Magnúsdóttir, Agnes; Dagsson-Waldhauserova, Pavla; Arnalds, Ólafur; Ólafsson, Haraldur</p> <p>2017-04-01</p> <p>Particulate matter mass concentrations and size fractions of PM1, PM2.5, PM4, PM10, and PM15 measured in transversal horizontal profile of two <span class="hlt">dust</span> storms in southwestern Iceland are presented. Images from a camera network were used to estimate the visibility and spatial extent of measured <span class="hlt">dust</span> events. Numerical simulations were used to calculate the total <span class="hlt">dust</span> flux from the sources as 180,000 and 280,000 tons for each storm. The mean PM15 concentrations inside of the <span class="hlt">dust</span> plumes varied from 10 to 1600 ?g?m?3 (PM10 = 7 to 583 ?g?m?3). The mean PM1 concentrations were 97-241 ?g?m?3 with a maximum of 261 ?g?m?3 for the first storm. The PM1/PM2.5 ratios of >0.9 and PM1/PM10 ratios of 0.34-0.63 show that suspension of volcanic materials in Iceland causes air pollution with extremely high PM1 concentrations, similar to polluted urban areas in Europe or Asia. Icelandic volcanic <span class="hlt">dust</span> consists of a higher proportion of submicron particles compared to crustal <span class="hlt">dust</span>. Both <span class="hlt">dust</span> storms occurred in relatively densely inhabited areas of Iceland. First results on size partitioning of Icelandic <span class="hlt">dust</span> presented here should challenge health authorities to enhance research in relation to <span class="hlt">dust</span> and shows the need for public <span class="hlt">dust</span> warning systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018SSRv..214...64L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018SSRv..214...64L"><span>Cometary <span class="hlt">Dust</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Levasseur-Regourd, Anny-Chantal; Agarwal, Jessica; Cottin, Hervé; Engrand, Cécile; Flynn, George; Fulle, Marco; Gombosi, Tamas; Langevin, Yves; Lasue, Jérémie; Mannel, Thurid; Merouane, Sihane; Poch, Olivier; Thomas, Nicolas; Westphal, Andrew</p> <p>2018-04-01</p> <p>This review presents our understanding of cometary <span class="hlt">dust</span> at the end of 2017. For decades, insight about the <span class="hlt">dust</span> ejected by nuclei of comets had stemmed from remote observations from Earth or Earth's orbit, and from flybys, including the samples of <span class="hlt">dust</span> returned to Earth for laboratory studies by the Stardust return capsule. The long-duration Rosetta mission has recently provided a huge and unique amount of data, obtained using numerous instruments, including innovative <span class="hlt">dust</span> instruments, over a wide range of distances from the Sun and from the nucleus. The diverse approaches available to study <span class="hlt">dust</span> in comets, together with the related theoretical and experimental studies, provide evidence of the composition and physical properties of <span class="hlt">dust</span> particles, e.g., the presence of a large fraction of carbon in macromolecules, and of aggregates on a wide range of scales. The results have opened vivid discussions on the variety of <span class="hlt">dust</span>-release processes and on the diversity of <span class="hlt">dust</span> properties in comets, as well as on the formation of cometary <span class="hlt">dust</span>, and on its presence in the near-Earth interplanetary medium. These discussions stress the significance of future explorations as a way to decipher the formation and evolution of our Solar System.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1996LPI....27.1071R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1996LPI....27.1071R"><span>Principal <span class="hlt">Components</span> Constrain Dynamic Pyrometamorphism in a Partially Melted Interplanetary <span class="hlt">Dust</span> Particle</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rietmeijer, F. J. M.</p> <p>1996-03-01</p> <p>All interplanetary <span class="hlt">dust</span> particles [IDPs] that decelerate in the Earth's atmosphere experience flash heating whereby their orbital velocity (km s^-1) is reduced to cm s^-1. Iron-oxide rims that may either be continuous on the particle surface, or discontinuous along its perimeter, occur on many IDPs. It is the most conspicuous mineralogical indicator of dynamic pyrometamorphism and its formation is interpreted as 'intense' IDP heating. It appears that the formation of these magnetite and maghemite rims is intimately linked to the presence of Fe,Ni-sulfides in the pre-entry particle. In this regard chondritic porous (CP) IDP L2011K7 may be an unusual particle. This porous aggregate consists of S-free polyphase units (PUs), nonstoichiometric diopside and Mg-rich wollastonite single-crystals and small, accessory Fe,Ni-sulfide grains. Only a few Fe-oxide nanograins are present along its perimeter. The nonstoichiometry of its Ca,Mg-clinopyroxenes indicates incongruent melting or vaporization that was experimentally determined at 1300 degrees-1400 degrees C. The CP IDP L2011K7 is probably of cometary origin since active comet nuclei are the most likely sources for uncompacted aggregate IDPs whereby their low density (< 1 g cm^-3) enhances atmospheric entry survival of large particles. In addition, the fluffy texture which inhibits chemical exchange among its <span class="hlt">components</span> further enhances their survival unless compaction occurs during deceleration in the Earth's atmosphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2728055','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2728055"><span>Addition of Alarm Pheromone <span class="hlt">Components</span> Improves the Effectiveness of Desiccant <span class="hlt">Dusts</span> Against Cimex lectularius</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>BENOIT, JOSHUA B.; PHILLIPS, SETH A.; CROXALL, TRAVIS J.; CHRISTENSEN, BRADY S.; YODER, JAY A.; DENLINGER, DAVID L.</p> <p>2009-01-01</p> <p>We demonstrate that the addition of bed bug, Cimex lectularius, alarm pheromone to desiccant formulations greatly enhances their effectiveness during short-term exposure. Two desiccant formulations, diatomaceous earth (DE) and Dri-die (silica gel), were applied at the label rate with and without bed bug alarm pheromone <span class="hlt">components</span>, (E)-2-hexenal, (E)-2-octenal, and a (E)-2-hexenal:(E)-2-octenal blend. First-instar nymphs and adult females were subjected to 10-min exposures, and water loss rates were used to evaluate the response. Optimal effectiveness was achieved with a pheromone concentration of 0.01 M. With Dri-die alone, the water loss was 21% higher than in untreated controls, and water loss increased nearly two times with (E)-2-hexenal and (E)-2-octenal and three times with the (E)-2-hexenal: (E)-2-octenal blend. This shortened survival of first-instar nymphs from 4 to 1 d, with a similar reduction noted in adult females. DE was effective only if supplemented with pheromone, resulting in a 50% increase in water loss over controls with the (E)-2-hexenal:(E)-2-octenal blend, and a survival decrease from 4 to 2 d in first-instar nymphs. Consistently, the addition of the pheromone blend to desiccant <span class="hlt">dust</span> was more effective than adding either <span class="hlt">component</span> by itself or by using Dri-die or DE alone. Based on observations in a small microhabitat, the addition of alarm pheromone <span class="hlt">components</span> prompted bed bugs to leave their protective harborages and to move through the desiccant, improving the use of desiccants for control. We concluded that short exposure to Dri-die is a more effective treatment against bed bugs than DE and that the effectiveness of the desiccants can be further enhanced by incorporation of alarm pheromone. Presumably, the addition of alarm pheromone elevates excited crawling activity, thereby promoting cuticular changes that increase water loss. PMID:19496429</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015MinPe.109..377L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015MinPe.109..377L"><span>The dissolution of natural and artificial <span class="hlt">dusts</span> in glutamic acid</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ling, Zhang; Faqin, Dong; Xiaochun, He</p> <p>2015-06-01</p> <p>This article describes the characteristics of natural <span class="hlt">dusts</span>, industrial <span class="hlt">dusts</span>, and artificial <span class="hlt">dusts</span>, such as mineral phases, chemical <span class="hlt">components</span>, morphological observation and size. Quartz and calcite are the main phases of natural <span class="hlt">dusts</span> and industrial <span class="hlt">dusts</span> with high SiO2 and CaO and low K2O and Na2O in the chemical composition. The dissolution and electrochemical action of <span class="hlt">dusts</span> in glutamic acid liquor at the simulated human body temperature (37 °C) in 32 h was investigated. The potential harm that the <span class="hlt">dust</span> could lead to in body glutamic acid acidic environment, namely biological activity, is of great importance for revealing the human toxicological mechanism. The changes of pH values and electric conductivity of suspension of those <span class="hlt">dusts</span> were similar, increased slowly in the first 8 h, and then the pH values increased rapidly. The total amount of dissolved ions of K, Ca, Na, and Mg was 35.4 to 429 mg/kg, particularly Ca was maximal of 20 to 334 mg/kg. The total amount of dissolved ions of Fe, Zn, Mn, Pb, and Ba was 0.18 to 5.59 mg/kg and in Al and Si was 3.0 to 21.7 mg/kg. The relative solubility order of <span class="hlt">dusts</span> in glutamic acid is wollastonite > serpentine > sepiolite, the cement plant industrial <span class="hlt">dusts</span> > natural <span class="hlt">dusts</span> > power plant industrial <span class="hlt">dusts</span>. The wollastonite and cement plant industrial <span class="hlt">dusts</span> have the highest solubility, which also have high content of CaO; this shows that there are a poorer corrosion-resisting ability and lower bio-resistibility. Sepiolite and power plant industrial <span class="hlt">dusts</span> have lowest solubility, which also have high content of SiO2; this shows that there are a higher corrosion-resisting ability and stronger bio-resistibility.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17100663','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17100663"><span>Exposure to microbial <span class="hlt">components</span> and allergens in population studies: a comparison of two house <span class="hlt">dust</span> collection methods applied by participants and fieldworkers.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Schram-Bijkerk, D; Doekes, G; Boeve, M; Douwes, J; Riedler, J; Ublagger, E; von Mutius, E; Benz, M; Pershagen, G; Wickman, M; Alfvén, T; Braun-Fahrländer, C; Waser, M; Brunekreef, B</p> <p>2006-12-01</p> <p><span class="hlt">Dust</span> collection by study participants instead of fieldworkers would be a practical and cost-effective alternative in large-scale population studies estimating exposure to indoor allergens and microbial agents. We aimed to compare <span class="hlt">dust</span> weights and biological agent levels in house <span class="hlt">dust</span> samples taken by study participants with nylon socks, with those in samples taken by fieldworkers using the sampling nozzle of the Allergology Laboratory Copenhagen (ALK). In homes of 216 children, parents and fieldworkers collected house <span class="hlt">dust</span> within the same year. <span class="hlt">Dust</span> samples were analyzed for levels of allergens, endotoxin, (1-->3)-beta-D-glucans and fungal extracellular polysaccharides (EPS). Socks appeared to yield less <span class="hlt">dust</span> from mattresses at relatively low <span class="hlt">dust</span> amounts and more <span class="hlt">dust</span> at high <span class="hlt">dust</span> amounts than ALK samples. Correlations between the methods ranged from 0.47-0.64 for microbial agents and 0.64-0.87 for mite and pet allergens. Cat allergen levels were two-fold lower and endotoxin levels three-fold higher in socks than in ALK samples. Levels of allergens and microbial agents in sock samples taken by study participants are moderately to highly correlated to levels in ALK samples taken by fieldworkers. Absolute levels may differ, probably because of differences in the method rather than in the person who performed the sampling. Practical Implications <span class="hlt">Dust</span> collection by participants is a reliable and practical option for allergen and microbial agent exposure assessment. Absolute levels of biological agents are not (always) comparable between studies using different <span class="hlt">dust</span> collection methods, even when expressed per gram <span class="hlt">dust</span>, because of potential differences in particle-size constitution of the collected <span class="hlt">dust</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JTAP..tmp...13T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JTAP..tmp...13T"><span>Effect of <span class="hlt">dust</span> on tilted electrostatic resistive instability in a Hall thruster</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tyagi, Jasvendra; Singh, Sukhmander; Malik, Hitendra K.</p> <p>2018-03-01</p> <p>Effect of negatively charged <span class="hlt">dust</span> on resistive instability corresponding to the electrostatic wave is investigated in a Hall thruster plasma when this purely azimuthal wave is tilted and strong axial <span class="hlt">component</span> of wave vector is developed. Analytical calculations are done to obtain the relevant dispersion equation, which is solved numerically to investigate the growth rate of the instability. The magnitude of the growth rate in the plasma having <span class="hlt">dust</span> particles is found to be much smaller than the case of pure plasma. However, the instability grows faster for the increasing <span class="hlt">dust</span> density and the higher charge on the <span class="hlt">dust</span> particles. The higher magnetic field is also found to support the instability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013PhDT.......350L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013PhDT.......350L"><span>The circumstellar environment of evolved stars as traced by molecules and <span class="hlt">dust</span>. The diagnostic power of Herschel</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lombaert, Robin</p> <p>2013-12-01</p> <p> require that the <span class="hlt">dust</span> species is embedded in a heterogeneous composite grain structure together with carbonaceous compounds. The final chapter considers the circumstellar gas chemistry of carbon-rich AGB stars. The recent discovery of <span class="hlt">warm</span> water vapor in carbon-rich winds challenges our understanding of chemical processes ongoing in the wind. Two mechanisms for producing <span class="hlt">warm</span> water were proposed: water formation induced by interstellar ultraviolet photons penetrating into the inner region of a clumpy wind, and water formation induced by shocks passing through the atmospheric and inner-wind molecular gas. A sample of eighteen carbon-rich AGB stars has been observed with the Herschel Space Telescope and offers insights into the dependence of water properties on the stellar and circumstellar conditions. We suggest that both proposed water formation mechanisms must be at work to account for the following findings: 1) <span class="hlt">warm</span> water is present in all observed carbon stars; 2) water formation efficiency decreases with higher circumstellar column density; 3) water properties strongly depend on the variability characteristics of the AGB stars; and 4) a positive water abundance gradient is present up to at most ˜ 50 rstar in individual stars.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20170002771&hterms=target&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dtarget','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20170002771&hterms=target&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dtarget"><span>Assimilation of MODIS Dark Target and Deep Blue Observations in the <span class="hlt">Dust</span> Aerosol <span class="hlt">Component</span> of NMMB-MONARCH version 1.0</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Di Tomaso, Enza; Schutgens, Nick A. J.; Jorba, Oriol; Perez Garcia-Pando, Carlos</p> <p>2017-01-01</p> <p>A data assimilation capability has been built for the NMMB-MONARCH chemical weather prediction system, with a focus on mineral <span class="hlt">dust</span>, a prominent type of aerosol. An ensemble-based Kalman filter technique (namely the local ensemble transform Kalman filter - LETKF) has been utilized to optimally combine model background and satellite retrievals. Our implementation of the ensemble is based on known uncertainties in the physical parametrizations of the <span class="hlt">dust</span> emission scheme. Experiments showed that MODIS AOD retrievals using the Dark Target algorithm can help NMMB-MONARCH to better characterize atmospheric <span class="hlt">dust</span>. This is particularly true for the analysis of the <span class="hlt">dust</span> outflow in the Sahel region and over the African Atlantic coast. The assimilation of MODIS AOD retrievals based on the Deep Blue algorithm has a further positive impact in the analysis downwind from the strongest <span class="hlt">dust</span> sources of the Sahara and in the Arabian Peninsula. An analysis-initialized forecast performs better (lower forecast error and higher correlation with observations) than a standard forecast, with the exception of underestimating <span class="hlt">dust</span> in the long-range Atlantic transport and degradation of the temporal evolution of <span class="hlt">dust</span> in some regions after day 1. Particularly relevant is the improved forecast over the Sahara throughout the forecast range thanks to the assimilation of Deep Blue retrievals over areas not easily covered by other observational datasets.The present study on mineral <span class="hlt">dust</span> is a first step towards data assimilation with a complete aerosol prediction system that includes multiple aerosol species.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GMD....10.1107D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GMD....10.1107D"><span>Assimilation of MODIS Dark Target and Deep Blue observations in the <span class="hlt">dust</span> aerosol <span class="hlt">component</span> of NMMB-MONARCH version 1.0</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Di Tomaso, Enza; Schutgens, Nick A. J.; Jorba, Oriol; Pérez García-Pando, Carlos</p> <p>2017-03-01</p> <p>A data assimilation capability has been built for the NMMB-MONARCH chemical weather prediction system, with a focus on mineral <span class="hlt">dust</span>, a prominent type of aerosol. An ensemble-based Kalman filter technique (namely the local ensemble transform Kalman filter - LETKF) has been utilized to optimally combine model background and satellite retrievals. Our implementation of the ensemble is based on known uncertainties in the physical parametrizations of the <span class="hlt">dust</span> emission scheme. Experiments showed that MODIS AOD retrievals using the Dark Target algorithm can help NMMB-MONARCH to better characterize atmospheric <span class="hlt">dust</span>. This is particularly true for the analysis of the <span class="hlt">dust</span> outflow in the Sahel region and over the African Atlantic coast. The assimilation of MODIS AOD retrievals based on the Deep Blue algorithm has a further positive impact in the analysis downwind from the strongest <span class="hlt">dust</span> sources of the Sahara and in the Arabian Peninsula. An analysis-initialized forecast performs better (lower forecast error and higher correlation with observations) than a standard forecast, with the exception of underestimating <span class="hlt">dust</span> in the long-range Atlantic transport and degradation of the temporal evolution of <span class="hlt">dust</span> in some regions after day 1. Particularly relevant is the improved forecast over the Sahara throughout the forecast range thanks to the assimilation of Deep Blue retrievals over areas not easily covered by other observational datasets. The present study on mineral <span class="hlt">dust</span> is a first step towards data assimilation with a complete aerosol prediction system that includes multiple aerosol species.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20170000345&hterms=agriculture&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dagriculture','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20170000345&hterms=agriculture&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dagriculture"><span>Simulating US Agriculture in a Modern <span class="hlt">Dust</span> Bowl Drought</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Glotter, Michael; Elliott, Joshua</p> <p>2016-01-01</p> <p>Drought-induced agricultural loss is one of the most costly impacts of extreme weather, and without mitigation, climate change is likely to increase the severity and frequency of future droughts. The <span class="hlt">Dust</span> Bowl of the 1930s was the driest and hottest for agriculture in modern US history. Improvements in farming practices have increased productivity, but yields today are still tightly linked to climate variation and the impacts of a 1930s-type drought on current and future agricultural systems remain unclear. Simulations of biophysical process and empirical models suggest that <span class="hlt">Dust</span>-Bowl-type droughts today would have unprecedented consequences, with yield losses approx.50% larger than the severe drought of 2012. Damages at these extremes are highly sensitive to temperature, worsening by approx.25% with each degree centigrade of <span class="hlt">warming</span>. We find that high temperatures can be more damaging than rainfall deficit, and, without adaptation, warmer mid-century temperatures with even average precipitation could lead to maize losses equivalent to the <span class="hlt">Dust</span> Bowl drought. Warmer temperatures alongside consecutive droughts could make up to 85% of rain-fed maize at risk of changes that may persist for decades. Understanding the interactions of weather extremes and a changing agricultural system is therefore critical to effectively respond to, and minimize, the impacts of the next extreme drought event.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.C13B0553L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.C13B0553L"><span>The role of mineral <span class="hlt">dust</span> aerosols in polar amplification</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lambert, F.; Kug, J.; Park, R.; Jin, F.; Lee, J. H.</p> <p>2010-12-01</p> <p>During today’s global <span class="hlt">warming</span>, as well as during glacial-interglacial changes, temperature increase is larger in polar areas than the global average, a phenomenon called “polar amplification”. Model studies suggest ice cap melting due to greenhouse gas induced temperature rise, and consequent decrease of albedo and enhanced oceanic and atmospheric heat transport, as the primary cause for this phenomenon in nowadays Arctic. However, the underlying causes for polar amplification on glacial-interglacial timescales are still unclear, especially in the Antarctic where sea ice coverage does not change as drastically as in the North. Recent results have shown that the temperature increase is not limited to the surface and that these changes can not be explained by snow and ice changes alone. Starting with <span class="hlt">dust</span> flux measurements from ice cores in Greenland and Antarctica, we have estimated tropospheric concentrations using deposition velocities and vertical concentration profiles for Holocene and LGM conditions from the National Center for Atmospheric Research’s Community Climate System Model (CCSM3) and a 3-D global chemical transport model (GEOS-Chem). The radiative forcing due to mineral <span class="hlt">dust</span> aerosols was then estimated using the GEOS-Chem model, based on the particle properties found in the ice. Preliminary results point towards positive forcing of <span class="hlt">dust</span> because of the high albedo of the underlying ice sheets.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27941818','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27941818"><span>Simulating US agriculture in a modern <span class="hlt">Dust</span> Bowl drought.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Glotter, Michael; Elliott, Joshua</p> <p>2016-12-12</p> <p>Drought-induced agricultural loss is one of the most costly impacts of extreme weather 1-3 , and without mitigation, climate change is likely to increase the severity and frequency of future droughts 4,5 . The <span class="hlt">Dust</span> Bowl of the 1930s was the driest and hottest for agriculture in modern US history. Improvements in farming practices have increased productivity, but yields today are still tightly linked to climate variation 6 and the impacts of a 1930s-type drought on current and future agricultural systems remain unclear. Simulations of biophysical process and empirical models suggest that <span class="hlt">Dust</span>-Bowl-type droughts today would have unprecedented consequences, with yield losses ∼50% larger than the severe drought of 2012. Damages at these extremes are highly sensitive to temperature, worsening by ∼25% with each degree centigrade of <span class="hlt">warming</span>. We find that high temperatures can be more damaging than rainfall deficit, and, without adaptation, warmer mid-century temperatures with even average precipitation could lead to maize losses equivalent to the <span class="hlt">Dust</span> Bowl drought. Warmer temperatures alongside consecutive droughts could make up to 85% of rain-fed maize at risk of changes that may persist for decades. Understanding the interactions of weather extremes and a changing agricultural system is therefore critical to effectively respond to, and minimize, the impacts of the next extreme drought event.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12107295','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12107295"><span>Pulmonary epithelial response in the rat lung to instilled Montserrat respirable <span class="hlt">dusts</span> and their major mineral <span class="hlt">components</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Housley, D G; Bérubé, K A; Jones, T P; Anderson, S; Pooley, F D; Richards, R J</p> <p>2002-07-01</p> <p>The Soufriere Hills, a stratovolcano on Montserrat, started erupting in July 1995, producing volcanic ash, both from dome collapse pyroclastic flows and phreatic explosions. The eruptions/ash resuspension result in high concentrations of suspended particulate matter in the atmosphere, which includes cristobalite, a mineral implicated in respiratory disorders. To conduct toxicological studies on characterised samples of ash, together with major <span class="hlt">components</span> of the <span class="hlt">dust</span> mixture (anorthite, cristobalite), and a bioreactive mineral control (DQ12 quartz). Rats were challenged with a single mass (1 mg) dose of particles via intratracheal instillation and groups sacrificed at one, three, and nine weeks. Acute bioreactivity of the particles was assessed by increases in lung permeability and inflammation, changes in epithelial cell markers, and increase in the size of bronchothoracic lymph nodes. Data indicated that respirable ash derived from pyroclastic flows (20.1% cristobalite) or phreatic explosion (8.6% cristobalite) had minimal bioreactivity in the lung. Anorthite showed low bioreactivity, in contrast to pure cristobalite, which showed progressive increases in lung damage. Results suggests that either the percentage mass of cristobalite particles present in Montserrat ash was not sufficient as a catalyst in the lung environment, or its surface reactivity was masked by the non-reactive volcanic glass <span class="hlt">components</span> during the process of ash formation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.1927K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.1927K"><span><span class="hlt">Dust</span> influx into the northern Indian Ocean over the last 1.5 Myr.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kunkelová, Tereza; Kroon, Dick; Jung, Simon; de Leau, Erica S.; Odling, Nicholas; Spezzaferri, Silvia; Hayman, Stephanie; Alonso-Garcia, Montserrat; Wright, James D.; Alvarez Zarikian, Carlos; Betzler, Christian; Eberli, Gregor P.; Jovane, Luigi; Laya, Juan Carlos; Hui-Mee, Anna Ling; Reijmer, John; Reolid, Jesus; Sloss, Craig R.</p> <p>2017-04-01</p> <p>Over the last 2 Ma the Earth's climate has been profoundly affected by quasi-periodic changes in the Earth's orbit around the Sun. The Earth's climate reflects cooling and <span class="hlt">warming</span> associated with this orbital forcing, such as periods of glaciation and warmer interglacials, variations in sea surface temperatures and changes in global wind patterns. During glacial periods, <span class="hlt">dust</span> input into the oceans increased as a result of stronger surface winds and greater source area from increased desertification. At low latitudes, the seasonality of monsoonal wind direction controls <span class="hlt">dust</span> transport into the ocean. This research identifies the main controls on <span class="hlt">dust</span> influx into the northern Indian Ocean over the last 1.5 Ma by analyzing the first high resolution marine sediment record from the Maldives carbonate platform (IODP Expedition 359; Site U1467), an area strongly affected by the monsoon seasons. Here we present variations in the concentration of specific normalized elements, from X-ray fluorescence spectrometry, reflecting the chemistry of the <span class="hlt">dust</span> particles and source areas. The new <span class="hlt">dust</span> record will be compared to other records of climate change, mainly from the North Atlantic, to investigate the degree of coupling between driving forces in the Earth's climate in the northern hemisphere. The results of this study will aid our understanding of the monsoon system, low latitude desertification, and the degree of climate coupling, essential for predicting the response of the system to future anthropogenic climate change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19800063628&hterms=monsanto&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dmonsanto','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19800063628&hterms=monsanto&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dmonsanto"><span>Optical spectroscopy of interplanetary <span class="hlt">dust</span> collected in the earth's stratosphere</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Fraundorf, P.; Patel, R. I.; Shirck, J.; Walker, R. M.; Freeman, J. J.</p> <p>1980-01-01</p> <p>Optical absorption spectra of interplanetary <span class="hlt">dust</span> particles 2-30 microns in size collected in the atmosphere at an altitude of 20 km by inertial impactors mounted on NASA U-2 aircraft are reported. Fourier transform absorption spectroscopy of crushed samples of the particles reveals a broad feature in the region 1300-800 kaysers which has also been found in meteorite and cometary <span class="hlt">dust</span> spectra, and a weak iron crystal field absorption band at approximately 9800 kaysers, as is observed in meteorites. Work is currently in progress to separate the various <span class="hlt">components</span> of the interplanetary <span class="hlt">dust</span> particles in order to evaluate separately their contributions to the absorption.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.A11D3043S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.A11D3043S"><span>Integrating Windblown <span class="hlt">Dust</span> Forecasts with Public Safety and Health Systems</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sprigg, W. A.</p> <p>2014-12-01</p> <p>Experiments in real-time prediction of desert <span class="hlt">dust</span> emissions and downstream plume concentrations (~ 3.5 km near-surface spatial resolution) succeed to the point of challenging public safety and public health services to beta test a <span class="hlt">dust</span> storm warning and advisory system in lowering risks of highway and airline accidents and illnesses such as asthma and valley fever. Key beta test <span class="hlt">components</span> are: high-resolution models of <span class="hlt">dust</span> emission, entrainment and diffusion, integrated with synoptic weather observations and forecasts; satellite-based detection and monitoring of soil properties on the ground and elevated above; high space and time resolution for health surveillance and transportation advisories.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AstBu..70..474Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AstBu..70..474Z"><span>Hydrodynamic model of a self-gravitating optically thick gas and <span class="hlt">dust</span> cloud</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhukova, E. V.; Zankovich, A. M.; Kovalenko, I. G.; Firsov, K. M.</p> <p>2015-10-01</p> <p>We propose an original mechanism of sustained turbulence generation in gas and <span class="hlt">dust</span> clouds, the essence of which is the consistent provision of conditions for the emergence and maintenance of convective instability in the cloud. We considered a quasi-stationary one-dimensional model of a selfgravitating flat cloud with stellar radiation sources in its center. The material of the cloud is considered a two-<span class="hlt">component</span> two-speed continuous medium, the first <span class="hlt">component</span> of which, gas, is transparent for stellar radiation and is supposed to rest being in hydrostatic equilibrium, and the second one, <span class="hlt">dust</span>, is optically dense and is swept out by the pressure of stellar radiation to the periphery of the cloud. The <span class="hlt">dust</span> is specified as a set of spherical grains of a similar size (we made calculations for <span class="hlt">dust</span> particles with radii of 0.05, 0.1, and 0.15 μm). The processes of scattering and absorption of UV radiation by <span class="hlt">dust</span> particles followed by IR reradiation, with respect to which the medium is considered to be transparent, are taken into account. <span class="hlt">Dust</span>-driven stellar wind sweeps gas outwards from the center of the cloud, forming a cocoon-like structure in the gas and <span class="hlt">dust</span>. For the radiation flux corresponding to a concentration of one star with a luminosity of about 5 ×104 L ⊙ per square parsec on the plane of sources, sizes of the gas cocoon are equal to 0.2-0.4 pc, and for the <span class="hlt">dust</span> one they vary from tenths of a parsec to six parsecs. Gas and <span class="hlt">dust</span> in the center of the cavity are heated to temperatures of about 50-60 K in the model with graphite particles and up to 40 K in the model with silicate <span class="hlt">dust</span>, while the background equilibrium temperature outside the cavity is set equal to 10 K. The characteristic <span class="hlt">dust</span> expansion velocity is about 1-7 kms-1. Three structural elements define the hierarchy of scales in the <span class="hlt">dust</span> cocoon. The sizes of the central rarefied cavity, the dense shell surrounding the cavity, and the thin layer inside the shell in which <span class="hlt">dust</span> is settling provide</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ACP....18.1241A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ACP....18.1241A"><span>The early summertime Saharan heat low: sensitivity of the radiation budget and atmospheric heating to water vapour and <span class="hlt">dust</span> aerosol</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Alamirew, Netsanet K.; Todd, Martin C.; Ryder, Claire L.; Marsham, John H.; Wang, Yi</p> <p>2018-01-01</p> <p>The Saharan heat low (SHL) is a key <span class="hlt">component</span> of the west African climate system and an important driver of the west African monsoon across a range of timescales of variability. The physical mechanisms driving the variability in the SHL remain uncertain, although water vapour has been implicated as of primary importance. Here, we quantify the independent effects of variability in <span class="hlt">dust</span> and water vapour on the radiation budget and atmospheric heating of the region using a radiative transfer model configured with observational input data from the Fennec field campaign at the location of Bordj Badji Mokhtar (BBM) in southern Algeria (21.4° N, 0.9° E), close to the SHL core for June 2011. Overall, we find <span class="hlt">dust</span> aerosol and water vapour to be of similar importance in driving variability in the top-of-atmosphere (TOA) radiation budget and therefore the column-integrated heating over the SHL (˜ 7 W m-2 per standard deviation of <span class="hlt">dust</span> aerosol optical depth - AOD). As such, we infer that SHL intensity is likely to be similarly enhanced by the effects of <span class="hlt">dust</span> and water vapour surge events. However, the details of the processes differ. <span class="hlt">Dust</span> generates substantial radiative cooling at the surface (˜ 11 W m-2 per standard deviation of <span class="hlt">dust</span> AOD), presumably leading to reduced sensible heat flux in the boundary layer, which is more than compensated by direct radiative heating from shortwave (SW) absorption by <span class="hlt">dust</span> in the dusty boundary layer. In contrast, water vapour invokes a radiative <span class="hlt">warming</span> at the surface of ˜ 6 W m-2 per standard deviation of column-integrated water vapour in kg m-2. Net effects involve a pronounced net atmospheric radiative convergence with heating rates on average of 0.5 K day-1 and up to 6 K day-1 during synoptic/mesoscale <span class="hlt">dust</span> events from monsoon surges and convective cold-pool outflows (<q>haboobs</q>). On this basis, we make inferences on the processes driving variability in the SHL associated with radiative and advective heating/cooling. Depending</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22493866-electrostatic-twisted-modes-multi-component-dusty-plasmas','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22493866-electrostatic-twisted-modes-multi-component-dusty-plasmas"><span>Electrostatic twisted modes in multi-<span class="hlt">component</span> dusty plasmas</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Ayub, M. K.; National Centre for Physics, Shahdra Valley Road, Quaid-i-Azam University Campus, Islamabad 44000; Pohang University of Sciences and Technology, Pohang, Gyeongbuk 790-784</p> <p></p> <p>Various electrostatic twisted modes are re-investigated with finite orbital angular momentum in an unmagnetized collisionless multi-<span class="hlt">component</span> dusty plasma, consisting of positive/negative charged <span class="hlt">dust</span> particles, ions, and electrons. For this purpose, hydrodynamical equations are employed to obtain paraxial equations in terms of density perturbations, while assuming the Gaussian and Laguerre-Gaussian (LG) beam solutions. Specifically, approximated solutions for potential problem are studied by using the paraxial approximation and expressed the electric field <span class="hlt">components</span> in terms of LG functions. The energy fluxes associated with these modes are computed and corresponding expressions for orbital angular momenta are derived. Numerical analyses reveal that radial/angular modemore » numbers as well as <span class="hlt">dust</span> number density and <span class="hlt">dust</span> charging states strongly modify the LG potential profiles attributed to different electrostatic modes. Our results are important for understanding particle transport and energy transfer due to wave excitations in multi-<span class="hlt">component</span> dusty plasmas.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/1059193-direct-radiative-effect-mineral-dust-development-african-easterly-waves-late-summer','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1059193-direct-radiative-effect-mineral-dust-development-african-easterly-waves-late-summer"><span>Direct Radiative Effect of Mineral <span class="hlt">Dust</span> on the Development of African Easterly Waves in Late Summer, 2003-07</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Ma, Po-Lun; Zhang, Kai; Shi, Jainn Jong</p> <p>2012-12-19</p> <p>Episodic events of both Saharan <span class="hlt">dust</span> outbreaks and African easterly waves (AEWs) are observed to move westward over the eastern tropical Atlantic Ocean. The relationship between the <span class="hlt">warm</span>, dry, and dusty Saharan air layer on the nearby storms has been the subject of considerable debate. In this study, the Weather Research and Forecasting model is used to investigate the radiative effect of <span class="hlt">dust</span> on the development of AEWs during August and September, the months of maximumtropical cyclone activity, in years 2003–07. The simulations show that <span class="hlt">dust</span> radiative forcing enhances the convective instability of the environment. As a result, mostAEWsintensify inmore » the presence of a <span class="hlt">dust</span> layer. The Lorenz energy cycle analysis reveals that the <span class="hlt">dust</span> radiative forcing enhances the condensational heating, which elevates the zonal and eddy available potential energy. In turn, available potential energy is effectively converted to eddy kinetic energy, in which local convective overturning plays the primary role. The magnitude of the intensification effect depends on the initial environmental conditions, including moisture, baroclinity, and the depth of the boundary layer. The authors conclude that <span class="hlt">dust</span> radiative forcing, albeit small, serves as a catalyst to promote local convection that facilitates AEW development.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018MNRAS.474.5560I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018MNRAS.474.5560I"><span>Sparse estimation of model-based diffuse thermal <span class="hlt">dust</span> emission</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Irfan, Melis O.; Bobin, Jérôme</p> <p>2018-03-01</p> <p><span class="hlt">Component</span> separation for the Planck High Frequency Instrument (HFI) data is primarily concerned with the estimation of thermal <span class="hlt">dust</span> emission, which requires the separation of thermal <span class="hlt">dust</span> from the cosmic infrared background (CIB). For that purpose, current estimation methods rely on filtering techniques to decouple thermal <span class="hlt">dust</span> emission from CIB anisotropies, which tend to yield a smooth, low-resolution, estimation of the <span class="hlt">dust</span> emission. In this paper, we present a new parameter estimation method, premise: Parameter Recovery Exploiting Model Informed Sparse Estimates. This method exploits the sparse nature of thermal <span class="hlt">dust</span> emission to calculate all-sky maps of thermal <span class="hlt">dust</span> temperature, spectral index, and optical depth at 353 GHz. premise is evaluated and validated on full-sky simulated data. We find the percentage difference between the premise results and the true values to be 2.8, 5.7, and 7.2 per cent at the 1σ level across the full sky for thermal <span class="hlt">dust</span> temperature, spectral index, and optical depth at 353 GHz, respectively. A comparison between premise and a GNILC-like method over selected regions of our sky simulation reveals that both methods perform comparably within high signal-to-noise regions. However, outside of the Galactic plane, premise is seen to outperform the GNILC-like method with increasing success as the signal-to-noise ratio worsens.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMGC41B1096J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMGC41B1096J"><span>The Impact of Desert <span class="hlt">Dust</span> Aerosol Radiative Forcing on Global and West African Precipitation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jordan, A.; Zaitchik, B. F.; Gnanadesikan, A.; Dezfuli, A. K.</p> <p>2015-12-01</p> <p>Desert <span class="hlt">dust</span> aerosols exert a radiative forcing on the atmosphere, influencing atmospheric temperature structure and modifying radiative fluxes at the top of the atmosphere (TOA) and surface. As <span class="hlt">dust</span> aerosols perturb radiative fluxes, the atmosphere responds by altering both energy and moisture dynamics, with potentially significant impacts on regional and global precipitation. Global Climate Model (GCM) experiments designed to characterize these processes have yielded a wide range of results, owing to both the complex nature of the system and diverse differences across models. Most model results show a general decrease in global precipitation, but regional results vary. Here, we compare simulations from GFDL's CM2Mc GCM with multiple other model experiments from the literature in order to investigate mechanisms of radiative impact and reasons for GCM differences on a global and regional scale. We focus on West Africa, a region of high interannual rainfall variability that is a source of <span class="hlt">dust</span> and that neighbors major Sahara Desert <span class="hlt">dust</span> sources. As such, changes in West African climate due to radiative forcing of desert <span class="hlt">dust</span> aerosol have serious implications for desertification feedbacks. Our CM2Mc results show net cooling of the planet at TOA and surface, net <span class="hlt">warming</span> of the atmosphere, and significant increases in precipitation over West Africa during the summer rainy season. These results differ from some previous GCM studies, prompting comparative analysis of desert <span class="hlt">dust</span> parameters across models. This presentation will offer quantitative analysis of differences in <span class="hlt">dust</span> aerosol parameters, aerosol optical properties, and overall particle burden across GCMs, and will characterize the contribution of model differences to the uncertainty of forcing and climate response affecting West Africa.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19910004824','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19910004824"><span>Emission from small <span class="hlt">dust</span> particles in diffuse and molecular cloud medium</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bernard, J. P.; Desert, X.</p> <p>1990-01-01</p> <p>Infrared Astronomy Satellite (IRAS) observations of the whole galaxy has shown that long wavelength emission (100 and 60 micron bands) can be explained by thermal emission from big grains (approx 0.1 micron) radiating at their equilibrium temperature when heated by the InterStellar Radiation Field (ISRF). This conclusion has been confirmed by continuum sub-millimeter observations of the galactic plane made by the EMILIE experiment at 870 microns (Pajot et al. 1986). Nevertheless, shorter wavelength observations like 12 and 25 micron IRAS bands, show an emission from the galactic plane in excess with the long wavelength measurements which can only be explained by a much hotter particles population. Because <span class="hlt">dust</span> at equilibrium cannot easily reach high temperatures required to explain this excess, this <span class="hlt">component</span> is thought to be composed of very small <span class="hlt">dust</span> grains or big molecules encompassing thermal fluctuations. Researchers present here a numerical model that computes emission, from Near Infrared Radiation (NIR) to Sub-mm wavelengths, from a non-homogeneous spherical cloud heated by the ISRF. This model fully takes into account the heating of <span class="hlt">dust</span> by multi-photon processes and back-heating of <span class="hlt">dust</span> in the Visual/Infrared Radiation (VIS-IR) so that it is likely to describe correctly emission from molecular clouds up to large A sub v and emission from <span class="hlt">dust</span> experiencing temperature fluctuations. The <span class="hlt">dust</span> is a three <span class="hlt">component</span> mixture of polycyclic aromatic hydrocarbons, very small grains, and classical big grains with independent size distributions (cut-off and power law index) and abundances.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1335605-modeling-dust-emission-hl-tau-disk-based-planet-disk-interactions','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1335605-modeling-dust-emission-hl-tau-disk-based-planet-disk-interactions"><span>Modeling <span class="hlt">Dust</span> Emission of HL Tau Disk Based on Planet-Disk Interactions</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Jin, Sheng; Li, Shengtai; Isella, Andrea; ...</p> <p>2016-02-09</p> <p>In this paper, we use extensive global two-dimensional hydrodynamic disk gas+<span class="hlt">dust</span> simulations with embedded planets, coupled with three-dimensional radiative transfer calculations, to model the <span class="hlt">dust</span> ring and gap structures in the HL Tau protoplanetary disk observed with the Atacama Large Millimeter/Submillimeter Array (ALMA). We include the self-gravity of disk gas and <span class="hlt">dust</span> <span class="hlt">components</span> and make reasonable choices of disk parameters, assuming an already settled <span class="hlt">dust</span> distribution and no planet migration. We can obtain quite adequate fits to the observed <span class="hlt">dust</span> emission using three planets with masses of 0.35, 0.17, and 0.26 M Jup at 13.1, 33.0, and 68.6 AU, respectively.more » Finally, implications for the planet formation as well as the limitations of this scenario are discussed.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950012918&hterms=fine+dust&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dfine%2Bdust','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950012918&hterms=fine+dust&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dfine%2Bdust"><span>The fine nebula <span class="hlt">dust</span> <span class="hlt">component</span>: A key to chondrule formation by lightning</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wasson, J. T.; Rasmussen, K. L.</p> <p>1994-01-01</p> <p>Our assessment indicates that chondrule formation by lightning is indeed possible in the solar nebula. Previously the overriding objection to the lightning process of chondrule formation has been that low nebula pressures prevented the buildup of large potential differences. The breakdown potential is controlled by the mean free live distance of an electron. We calculate the mean free live distance in pure H2 gas at 2 AU to be approximately 500 m. A fine <span class="hlt">dust</span> load constituting 4 wt% of the <span class="hlt">dust</span> in the dusty midplane region leads to a reduced mean free live distance of only 7 m. Very conservatively we estimate the breakdown potential to be at least 10, 1.8, and 0.7 V/cm at 1, 2, and 3 AU respectively. We set the radius of the lightning bolt equal to the kinetic mean free path of the gas. Our calculations based on electron drift velocities in a fully ionized H2 gas show that first strike durations are 0.96, 3.4, and 7.0 ms at 1, 2, and 3 AU respectively, in much better accordance with the meteoritic evidence than previous estimates of 10-100 s.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..1514206P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..1514206P"><span>African <span class="hlt">dust</span> outbreaks over the Mediterranean Basin during 2001-2011: concentrations, phenomenology and trends</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pey, Jorge; Querol, Xavier; Alastuey, Andres; Forastiere, Franceso; Stafoggia, Massimo</p> <p>2013-04-01</p> <p>Concentrations, phenomenology and trends of African <span class="hlt">dust</span> outbreaks over the whole Mediterranean Basin werestudied on an 11-year period (2001-2011). This work has been performed in the context of the MED-PARTICLES (LIFE programme, EU) project, devoted to quantify short-term health effects of particulate matter over the Mediterranean region by distinguishing different particle sizes, chemical <span class="hlt">components</span> and sources, with emphasis in the effects of African <span class="hlt">dust</span>. In order to evaluate conduct this investigation, PM10 data from 19 regional and suburban background sites West to East in the Mediterranean area were compiled. After identifying the daily occurrence of African <span class="hlt">dust</span> outbreaks, a methodology for estimating natural <span class="hlt">dust</span> contributions on daily PM10 concentrations was applied. Our findings point out that African <span class="hlt">dust</span> outbreaks are sensibly more frequent in southern sitesacross the Mediterranean, from 30 to 37 % of the annual days, whereas they occur less than 20% of the annual days in northern sites. The central Mediterranean emerges as a transitional area, with slightly higher frequency of <span class="hlt">dust</span> episodes in its lower extreme when compared to similar latitudinal positions in western and eastern sides of the Basin. A decreasing south to north gradient of African <span class="hlt">dust</span> contribution to PM10, driven by the latitudinal position of the monitoring sites at least 25°E westwards across the Basin,is patent across the Mediterranean. From 25°E eastwards, higher annual <span class="hlt">dust</span> contributions are encountered due to the elevated annual occurrence of severe episodesof <span class="hlt">dust</span> but also because of inputs from Middle Eastern deserts. Concerning seasonality patterns and intensity characteristics, a clear summer prevalence is observed in the western part, with low occurrence of severe episodes (daily <span class="hlt">dust</span> averages over 100 µg m-3 in PM10); no seasonal trend is detected in the central region, with moderate-intensity episodes; and significantly higher contributions are common in autumn</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013NucFu..53l3002R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013NucFu..53l3002R"><span>Migration of tungsten <span class="hlt">dust</span> in tokamaks: role of <span class="hlt">dust</span>-wall collisions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ratynskaia, S.; Vignitchouk, L.; Tolias, P.; Bykov, I.; Bergsåker, H.; Litnovsky, A.; den Harder, N.; Lazzaro, E.</p> <p>2013-12-01</p> <p>The modelling of a controlled tungsten <span class="hlt">dust</span> injection experiment in TEXTOR by the <span class="hlt">dust</span> dynamics code MIGRAINe is reported. The code, in addition to the standard <span class="hlt">dust</span>-plasma interaction processes, also encompasses major mechanical aspects of <span class="hlt">dust</span>-surface collisions. The use of analytical expressions for the restitution coefficients as functions of the <span class="hlt">dust</span> radius and impact velocity allows us to account for the sticking and rebound phenomena that define which parts of the <span class="hlt">dust</span> size distribution can migrate efficiently. The experiment provided unambiguous evidence of long-distance <span class="hlt">dust</span> migration; artificially introduced tungsten <span class="hlt">dust</span> particles were collected 120° toroidally away from the injection point, but also a selectivity in the permissible size of transported grains was observed. The main experimental results are reproduced by modelling.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/965127-water-uptake-clay-desert-dust-aerosol-particles-sub-supersaturated-water-vapor-conditions','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/965127-water-uptake-clay-desert-dust-aerosol-particles-sub-supersaturated-water-vapor-conditions"><span>Water uptake of clay and desert <span class="hlt">dust</span> aerosol particles at sub- and supersaturated water vapor conditions</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Herich, Hanna; Tritscher, Torsten; Wiacek, Aldona</p> <p>2009-11-01</p> <p>Airborne mineral <span class="hlt">dust</span> particles serve as cloud condensation nuclei (CCN), thereby influencing the formation and properties of <span class="hlt">warm</span> clouds. It is therefore of particular interest how <span class="hlt">dust</span> aerosols with different mineralogy behave when exposed to high relative humidity (RH) or supersaturation with respect to liquid water similar to atmospheric conditions. In this study the sub-saturated hygroscopic growth and the supersaturated cloud condensation nucleus activity of pure clays and real desert <span class="hlt">dust</span> aerosols was determined using a hygroscopicity tandem differential mobility analyzer (HTDMA) and a cloud condensation nuclei counter (CCNC), respectively. Five different illite, montmorillonite and kaolinite clay samples as wellmore » as three desert <span class="hlt">dust</span> samples (Saharan <span class="hlt">dust</span> (SD), Chinese <span class="hlt">dust</span> (CD) and Arizona test <span class="hlt">dust</span> (ATD)) were used. Aerosols were generated both with a wet and a dry disperser and the water uptake was parameterized via the hygroscopicity parameter, κ. The hygroscopicity of dry generated <span class="hlt">dust</span> aerosols was found to be negligible when compared to processed atmospheric aerosols, with CCNC derived κ values between 0.00 and 0.02. The latter value can be idealized as a particle consisting of 96.7% (by volume) insoluble material and ~3.3% ammonium sulfate. Pure clay aerosols were found to be generally less hygroscopic than real desert <span class="hlt">dust</span> particles. All illite and montmorillonite samples had κ~0.003, kaolinites were least hygroscopic and had κ=0.001. SD (κ=0.023) was found to be the most hygroscopic dry-generated desert <span class="hlt">dust</span> followed by CD (κ=0.007) and ATD (κ=0.003). Wet-generated <span class="hlt">dust</span> showed an increased water uptake when compared to dry-generated samples. This is considered to be an artifact introduced by redistribution of soluble material between the particles while immersed in an aqueous medium during atomization, thus indicating that specification of the generation method is critically important when presenting such data. Any atmospheric</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19727486','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19727486"><span>Water uptake of clay and desert <span class="hlt">dust</span> aerosol particles at sub- and supersaturated water vapor conditions.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Herich, Hanna; Tritscher, Torsten; Wiacek, Aldona; Gysel, Martin; Weingartner, Ernest; Lohmann, Ulrike; Baltensperger, Urs; Cziczo, Daniel J</p> <p>2009-09-28</p> <p>Airborne mineral <span class="hlt">dust</span> particles serve as cloud condensation nuclei (CCN), thereby influencing the formation and properties of <span class="hlt">warm</span> clouds. It is therefore of atmospheric interest how <span class="hlt">dust</span> aerosols with different mineralogy behave when exposed to high relative humidity (RH) or supersaturation (SS) with respect to liquid water. In this study the subsaturated hygroscopic growth and the supersaturated cloud condensation nucleus activity of pure clays and real desert <span class="hlt">dust</span> aerosols were determined using a hygroscopicity tandem differential mobility analyzer (HTDMA) and a cloud condensation nuclei counter (CCNC), respectively. Five different illite, montmorillonite and kaolinite clay samples as well as three desert <span class="hlt">dust</span> samples (Saharan <span class="hlt">dust</span> (SD), Chinese <span class="hlt">dust</span> (CD) and Arizona test <span class="hlt">dust</span> (ATD)) were investigated. Aerosols were generated both with a wet and a dry disperser. The water uptake was parameterized via the hygroscopicity parameter kappa. The hygroscopicity of dry generated <span class="hlt">dust</span> aerosols was found to be negligible when compared to processed atmospheric aerosols, with CCNC derived kappa values between 0.00 and 0.02 (the latter corresponds to a particle consisting of 96.7% by volume insoluble material and approximately 3.3% ammonium sulfate). Pure clay aerosols were generally found to be less hygroscopic than natural desert <span class="hlt">dust</span> particles. The illite and montmorillonite samples had kappa approximately 0.003. The kaolinite samples were less hygroscopic and had kappa=0.001. SD (kappa=0.023) was found to be the most hygroscopic dry-generated desert <span class="hlt">dust</span> followed by CD (kappa=0.007) and ATD (kappa=0.003). Wet-generated <span class="hlt">dust</span> showed an increased water uptake when compared to dry-generated samples. This is considered to be an artifact introduced by redistribution of soluble material between the particles. Thus, the generation method is critically important when presenting such data. These results indicate any atmospheric processing of a fresh mineral <span class="hlt">dust</span> particle which</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20110013536&hterms=absorbing+carbon&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dabsorbing%2Bcarbon','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20110013536&hterms=absorbing+carbon&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dabsorbing%2Bcarbon"><span>Enhanced Surface <span class="hlt">Warming</span> and Accelerated Snow Melt in the Himalayas and Tibetan Plateau Induced by Absorbing Aerosols</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lau, William K.; Kim, Maeng-Ki; Kim, Kyu-Myong; Lee, Woo-Seop</p> <p>2010-01-01</p> <p>Numerical experiments with the NASA finite-volume general circulation model show that heating of the atmosphere by <span class="hlt">dust</span> and black carbon can lead to widespread enhanced <span class="hlt">warming</span> over the Tibetan Plateau (TP) and accelerated snow melt in the western TP and Himalayas. During the boreal spring, a thick aerosol layer, composed mainly of <span class="hlt">dust</span> transported from adjacent deserts and black carbon from local emissions, builds up over the Indo-Gangetic Plain, against the foothills of the Himalaya and the TP. The aerosol layer, which extends from the surface to high elevation (approx.5 km), heats the mid-troposphere by absorbing solar radiation. The heating produces an atmospheric dynamical feedback the so-called elevated-heat-pump (EHP) effect, which increases moisture, cloudiness, and deep convection over northern India, as well as enhancing the rate of snow melt in the Himalayas and TP. The accelerated melting of snow is mostly confined to the western TP, first slowly in early April and then rapidly from early to mid-May. The snow cover remains reduced from mid-May through early June. The accelerated snow melt is accompanied by similar phases of enhanced <span class="hlt">warming</span> of the atmosphere-land system of the TP, with the atmospheric <span class="hlt">warming</span> leading the surface <span class="hlt">warming</span> by several days. Surface energy balance analysis shows that the short-wave and long-wave surface radiative fluxes strongly offset each other, and are largely regulated by the changes in cloudiness and moisture over the TP. The slow melting phase in April is initiated by an effective transfer of sensible heat from a warmer atmosphere to land. The rapid melting phase in May is due to an evaporation-snow-land feedback coupled to an increase in atmospheric moisture over the TP induced by the EHP effect.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1227765-modeling-dust-component-minerals-community-atmosphere-model-development-framework-impact-radiative-forcing','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1227765-modeling-dust-component-minerals-community-atmosphere-model-development-framework-impact-radiative-forcing"><span>Modeling <span class="hlt">dust</span> as <span class="hlt">component</span> minerals in the Community Atmosphere Model: development of framework and impact on radiative forcing</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Scanza, R. A.; Mahowald, N.; Ghan, S.; ...</p> <p>2014-07-02</p> <p>The mineralogy of desert <span class="hlt">dust</span> is important due to its effect on radiation, clouds and biogeochemical cycling of trace nutrients. This study presents the simulation of <span class="hlt">dust</span> radiative forcing as a function of both mineral composition and size at the global scale using mineral soil maps for estimating emissions. Externally mixed mineral aerosols in the bulk aerosol module in the Community Atmosphere Model version 4 (CAM4) and internally mixed mineral aerosols in the modal aerosol module in the Community Atmosphere Model version 5.1 (CAM5) embedded in the Community Earth System Model version 1.0.5 (CESM) are speciated into common mineral componentsmore » in place of total <span class="hlt">dust</span>. The simulations with mineralogy are compared to available observations of mineral atmospheric distribution and deposition along with observations of clear-sky radiative forcing efficiency. Based on these simulations, we estimate the all-sky direct radiative forcing at the top of the atmosphere as +0.05 W m −2 for both CAM4 and CAM5 simulations with mineralogy and compare this both with simulations of <span class="hlt">dust</span> in release versions of CAM4 and CAM5 (+0.08 and +0.17 W m −2) and of <span class="hlt">dust</span> with optimized optical properties, wet scavenging and particle size distribution in CAM4 and CAM5, −0.05 and −0.17 W m −2, respectively. The ability to correctly include the mineralogy of <span class="hlt">dust</span> in climate models is hindered by its spatial and temporal variability as well as insufficient global in-situ observations, incomplete and uncertain source mineralogies and the uncertainties associated with data retrieved from remote sensing methods.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1230072-modeling-dust-component-minerals-community-atmosphere-model-development-framework-impact-radiative-forcing','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1230072-modeling-dust-component-minerals-community-atmosphere-model-development-framework-impact-radiative-forcing"><span>Modeling <span class="hlt">dust</span> as <span class="hlt">component</span> minerals in the Community Atmosphere Model: development of framework and impact on radiative forcing</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Scanza, Rachel; Mahowald, N.; Ghan, Steven J.; ...</p> <p>2015-01-01</p> <p>The mineralogy of desert <span class="hlt">dust</span> is important due to its effect on radiation, clouds and biogeochemical cycling of trace nutrients. This study presents the simulation of <span class="hlt">dust</span> radiative forcing as a function of both mineral composition and size at the global scale, using mineral soil maps for estimating emissions. Externally mixed mineral aerosols in the bulk aerosol module in the Community Atmosphere Model version 4 (CAM4) and internally mixed mineral aerosols in the modal aerosol module in the Community Atmosphere Model version 5.1 (CAM5) embedded in the Community Earth System Model version 1.0.5 (CESM) are speciated into common mineral componentsmore » in place of total <span class="hlt">dust</span>. The simulations with mineralogy are compared to available observations of mineral atmospheric distribution and deposition along with observations of clear-sky radiative forcing efficiency. Based on these simulations, we estimate the all-sky direct radiative forcing at the top of the atmosphere as + 0.05 Wm⁻² for both CAM4 and CAM5 simulations with mineralogy. We compare this to the radiative forcing from simulations of <span class="hlt">dust</span> in release versions of CAM4 and CAM5 (+0.08 and +0.17 Wm⁻²) and of <span class="hlt">dust</span> with optimized optical properties, wet scavenging and particle size distribution in CAM4 and CAM5, -0.05 and -0.17 Wm⁻², respectively. The ability to correctly include the mineralogy of <span class="hlt">dust</span> in climate models is hindered by its spatial and temporal variability as well as insufficient global in situ observations, incomplete and uncertain source mineralogies and the uncertainties associated with data retrieved from remote sensing methods.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120016830','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120016830"><span>The Mars <span class="hlt">Dust</span> Cycle: Investigating the Effects of Radiatively Active Water Ice Clouds on Surface Stresses and <span class="hlt">Dust</span> Lifting Potential with the NASA Ames Mars General Circulation Model</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kahre, Melinda A.; Hollingsworth, Jeffery</p> <p>2012-01-01</p> <p>The <span class="hlt">dust</span> cycle is a critically important <span class="hlt">component</span> of Mars' current climate system. <span class="hlt">Dust</span> is present in the atmosphere of Mars year-round but the <span class="hlt">dust</span> loading varies with season in a generally repeatable manner. <span class="hlt">Dust</span> has a significant influence on the thermal structure of the atmosphere and thus greatly affects atmospheric circulation. The <span class="hlt">dust</span> cycle is the most difficult of the three climate cycles (CO2, water, and <span class="hlt">dust</span>) to model realistically with general circulation models. Until recently, numerical modeling investigations of the <span class="hlt">dust</span> cycle have typically not included the effects of couplings to the water cycle through cloud formation. In the Martian atmosphere, <span class="hlt">dust</span> particles likely provide the seed nuclei for heterogeneous nucleation of water ice clouds. As ice coats atmospheric <span class="hlt">dust</span> grains, the newly formed cloud particles exhibit different physical and radiative characteristics. Thus, the coupling between the <span class="hlt">dust</span> and water cycles likely affects the distributions of <span class="hlt">dust</span>, water vapor and water ice, and thus atmospheric heating and cooling and the resulting circulations. We use the NASA Ames Mars GCM to investigate the effects of radiatively active water ice clouds on surface stress and the potential for <span class="hlt">dust</span> lifting. The model includes a state-of-the-art water ice cloud microphysics package and a radiative transfer scheme that accounts for the radiative effects of CO2 gas, <span class="hlt">dust</span>, and water ice clouds. We focus on simulations that are radiatively forced by a prescribed <span class="hlt">dust</span> map, and we compare simulations that do and do not include radiatively active clouds. Preliminary results suggest that the magnitude and spatial patterns of surface stress (and thus <span class="hlt">dust</span> lifting potential) are substantial influenced by the radiative effects of water ice clouds.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20030067938','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20030067938"><span>Longwave Radiative Forcing of Saharan <span class="hlt">Dust</span> Aerosols Estimated from MODIS, MISR and CERES Observations on Terra</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zhang, Jiang-Long; Christopher, Sundar A.</p> <p>2003-01-01</p> <p>Using observations from the Multi-angle Imaging Spectroradiometer (MISR), the Moderate Resolution Imaging Spectroradiometer (MODIS), and the Clouds and the Earth's Radiant Energy System (CERES) instruments onboard the Terra satellite; we present a new technique for studying longwave (LW) radiative forcing of <span class="hlt">dust</span> aerosols over the Saharan desert for cloud-free conditions. The monthly-mean LW forcing for September 2000 is 7 W/sq m and the LW forcing efficiency' (LW(sub eff)) is 15 W/sq m. Using radiative transfer calculations, we also show that the vertical distribution of aerosols and water vapor are critical to the understanding of <span class="hlt">dust</span> aerosol forcing. Using well calibrated, spatially and temporally collocated data sets, we have combined the strengths of three sensors from the same satellite to quantify the LW radiative forcing, and show that <span class="hlt">dust</span> aerosols have a "<span class="hlt">warming</span>" effect over the Saharan desert that will counteract the shortwave "cooling effect" of aerosols.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26381088','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26381088"><span>Lead in Chinese villager house <span class="hlt">dust</span>: Geographical variation and influencing factors.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bi, Xiangyang; Liu, Jinling; Han, Zhixuan; Yang, Wenlin</p> <p>2015-12-01</p> <p>House <span class="hlt">dust</span> has been recognized as an important contributor to Pb exposure of children. Here we conducted a comprehensive study to investigate geographical variation of Pb in Chinese villager house <span class="hlt">dust</span>. The influences of outdoor soil Pb concentrations, dates of construction, house decoration materials, heating types, and site specific pollution on Pb concentrations in house <span class="hlt">dust</span> were evaluated. The concentrations of Pb in 477 house <span class="hlt">dust</span> samples collected from twenty eight areas throughout China varied from 12 to 2510 mg/kg, with a median concentration of 42 mg/kg. The median Pb concentrations in different geographical areas ranged from 16 (Zhangjiakou, Hebei) to 195 mg/kg (Loudi, Hunan). No correlations were found between the house <span class="hlt">dust</span> Pb concentrations and the age of houses, as well as house decoration materials. Whereas outdoor soil, coal combustion, and site specific pollution may be potential Pb sources. Principal <span class="hlt">component</span> analysis (PCA) confirmed that elemental compositions of the house <span class="hlt">dust</span> were controlled by both anthropogenic and geogenic sources. Using scanning electron microscopy (SEM), the Pb bearing particles in the house <span class="hlt">dust</span> were also studied. Copyright © 2015 Elsevier Ltd. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22600223-excitation-dust-kinetic-alfven-waves-semi-relativistic-ion-beams','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22600223-excitation-dust-kinetic-alfven-waves-semi-relativistic-ion-beams"><span>Excitation of <span class="hlt">dust</span> kinetic Alfven waves by semi-relativistic ion beams</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Rubab, N.; Jaffer, G.</p> <p>2016-05-15</p> <p>The growth rates for <span class="hlt">dust</span> kinetic Alfvén wave (DKAW) based on semi-relativistic Maxwellian distribution function are investigated in a hot and magnetized plasma. The dispersion relation of DKAW is obtained on a <span class="hlt">dust</span> acoustic velocity branch, and the kinetic instability due to cross-field semi-relativistic ion flow is examined by the effect of <span class="hlt">dust</span> parameters. Analytical expressions are derived for various modes as a natural consequence of the form of the solution, and is shown through graphical representation that the presence of <span class="hlt">dust</span> particles and the cross-field semi-relativistic ions sensibly modify the dispersion characteristics of low-frequency DKAW. The results are validmore » for a frequency regime well below the <span class="hlt">dust</span> cyclotron frequency. We suggest that semi-relativistic particles are an important factor in the growth/damping of DKAWs. It is also found that relativistic effects appear with the <span class="hlt">dust</span> lower hybrid frequency are more effective for <span class="hlt">dust</span> kinetic Alfvén waves in the perpendicular <span class="hlt">component</span> as compared to the parallel one. In particular, the relativistic effects associated with electrons suppress the instability while ions enhance the growth rates. The growth rates are significantly modified with <span class="hlt">dust</span> parameters and streaming velocity of cross-field ions.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-STS106-718-056.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-STS106-718-056.html"><span>View of a <span class="hlt">dust</span> storm taken from Atlantis during STS-106</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2000-09-11</p> <p>STS106-718-056 (11 September 2000) --- One of the STS-106 crew members on board the Space Shuttle Atlantis used a handheld 70mm camera to photograph this image of Afghanistan <span class="hlt">dust</span>/front winds in the upper Amu Darya Valley. The strong winds along the northern border of Afghanistan lofted thick, light brown <span class="hlt">dust</span> into the air (top half of the view). In this desert environment land surfaces are not protected by vegetation from the effect of blowing wind. The central Asian deserts experience the greatest number of <span class="hlt">dust</span> storm days on the planet each year. The sharp <span class="hlt">dust</span> front shows that the <span class="hlt">dust</span> has not traveled far, but has been raised from the surfaces in the view. <span class="hlt">Dust</span> is entrained in the atmosphere by horizontal winds but also by vertical movements. Here the vertical <span class="hlt">component</span> is indicated by the fact that the higher points along the <span class="hlt">dust</span> front are each topped by a small cumulus cloud, which appear as a line of small white puffballs. Cumulus clouds indicate upward motion and here the air which has entrained the <span class="hlt">dust</span> is lifting the air above to the level of condensation at each point where a small cloud has formed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ApJ...844..155T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ApJ...844..155T"><span>Attenuation Modified by DIG and <span class="hlt">Dust</span> as Seen in M31</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tomičić, Neven; Kreckel, Kathryn; Groves, Brent; Schinnerer, Eva; Sandstrom, Karin; Kapala, Maria; Blanc, Guillermo A.; Leroy, Adam</p> <p>2017-08-01</p> <p>The spatial distribution of <span class="hlt">dust</span> in galaxies affects the global attenuation, and hence inferred properties, of galaxies. We trace the spatial distribution of <span class="hlt">dust</span> in five approximately kiloparsec fields of M31 by comparing optical attenuation with the total <span class="hlt">dust</span> mass distribution. We measure the attenuation from the Balmer decrement using Integral Field Spectroscopy and the <span class="hlt">dust</span> mass from Herschel far-IR observations. Our results show that M31's <span class="hlt">dust</span> attenuation closely follows a foreground screen model, contrary to what was previously found in other nearby galaxies. By smoothing the M31 data, we find that spatial resolution is not the cause for this difference. Based on the emission-line ratios and two simple models, we conclude that previous models of <span class="hlt">dust</span>/gas geometry need to include a weakly or non-attenuated diffuse ionized gas (DIG) <span class="hlt">component</span>. Due to the variation of <span class="hlt">dust</span> and DIG scale heights with galactic radius, we conclude that different locations in galaxies will have different vertical distributions of gas and <span class="hlt">dust</span> and therefore different measured attenuation. The difference between our result in M31 with that found in other nearby galaxies can be explained by our fields in M31 lying at larger galactic radii than the previous studies that focused on the centers of galaxies.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018A%26A...612A..81R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018A%26A...612A..81R"><span>Gathering <span class="hlt">dust</span>: A galaxy-wide study of <span class="hlt">dust</span> emission from cloud complexes in NGC 300</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Riener, M.; Faesi, C. M.; Forbrich, J.; Lada, C. J.</p> <p>2018-05-01</p> <p>Aims: We use multi-band observations by the Herschel Space Observatory to study the <span class="hlt">dust</span> emission properties of the nearby spiral galaxy NGC 300. We compile a first catalogue of the population of giant <span class="hlt">dust</span> clouds (GDCs) in NGC 300, including temperature and mass estimates, and give an estimate of the total <span class="hlt">dust</span> mass of the galaxy. Methods: We carried out source detection with the multiwavelength source extraction algorithm getsources. We calculated physical properties, including mass and temperature, of the GDCs from five-band Herschel PACS and SPIRE observations from 100 to 500 μm; the final size and mass estimates are based on the observations at 250 μm that have an effective spatial resolution of 170 pc. We correlated our final catalogue of GDCs to pre-existing catalogues of HII regions to infer the number of GDCs associated with high-mass star formation and determined the Hα emission of the GDCs. Results: Our final catalogue of GDCs includes 146 sources, 90 of which are associated with known HII regions. We find that the <span class="hlt">dust</span> masses of the GDCs are completely dominated by the cold <span class="hlt">dust</span> <span class="hlt">component</span> and range from 1.1 × 103 to 1.4 × 104 M⊙. The GDCs have effective temperatures of 13-23 K and show a distinct cold <span class="hlt">dust</span> effective temperature gradient from the centre towards the outer parts of the stellar disk. We find that the population of GDCs in our catalogue constitutes 16% of the total <span class="hlt">dust</span> mass of NGC 300, which we estimate to be about 5.4 × 106 M⊙. At least about 87% of our GDCs have a high enough average <span class="hlt">dust</span> mass surface density to provide sufficient shielding to harbour molecular clouds. We compare our results to previous pointed molecular gas observations in NGC 300 and results from other nearby galaxies and also conclude that it is very likely that most of our GDCs are associated with complexes of giant molecular clouds. The catalogue is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://eric.ed.gov/?q=WTP&id=EJ906652','ERIC'); return false;" href="https://eric.ed.gov/?q=WTP&id=EJ906652"><span>Assessing the <span class="hlt">Warm</span> Glow Effect in Contingent Valuations for Public Libraries</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Lee, Soon-Jae; Chung, Hye-Kyung; Jung, Eun-Joo</p> <p>2010-01-01</p> <p>This article aims to present evidence of the <span class="hlt">warm</span> glow effect in a public library setting. More specifically, it tests whether individual respondents with different values for the <span class="hlt">warm</span> glow <span class="hlt">component</span> report different values for their willingness to pay (WTP). The data come from a contingent valuation survey conducted on randomly selected citizens…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ApJ...780...13I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ApJ...780...13I"><span>CO <span class="hlt">Component</span> Estimation Based on the Independent <span class="hlt">Component</span> Analysis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ichiki, Kiyotomo; Kaji, Ryohei; Yamamoto, Hiroaki; Takeuchi, Tsutomu T.; Fukui, Yasuo</p> <p>2014-01-01</p> <p>Fast Independent <span class="hlt">Component</span> Analysis (FastICA) is a <span class="hlt">component</span> separation algorithm based on the levels of non-Gaussianity. Here we apply FastICA to the <span class="hlt">component</span> separation problem of the microwave background, including carbon monoxide (CO) line emissions that are found to contaminate the PLANCK High Frequency Instrument (HFI) data. Specifically, we prepare 100 GHz, 143 GHz, and 217 GHz mock microwave sky maps, which include galactic thermal <span class="hlt">dust</span>, NANTEN CO line, and the cosmic microwave background (CMB) emissions, and then estimate the independent <span class="hlt">components</span> based on the kurtosis. We find that FastICA can successfully estimate the CO <span class="hlt">component</span> as the first independent <span class="hlt">component</span> in our deflection algorithm because its distribution has the largest degree of non-Gaussianity among the <span class="hlt">components</span>. Thus, FastICA can be a promising technique to extract CO-like <span class="hlt">components</span> without prior assumptions about their distributions and frequency dependences.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22348370-co-component-estimation-based-independent-component-analysis','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22348370-co-component-estimation-based-independent-component-analysis"><span>CO <span class="hlt">component</span> estimation based on the independent <span class="hlt">component</span> analysis</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Ichiki, Kiyotomo; Kaji, Ryohei; Yamamoto, Hiroaki</p> <p>2014-01-01</p> <p>Fast Independent <span class="hlt">Component</span> Analysis (FastICA) is a <span class="hlt">component</span> separation algorithm based on the levels of non-Gaussianity. Here we apply FastICA to the <span class="hlt">component</span> separation problem of the microwave background, including carbon monoxide (CO) line emissions that are found to contaminate the PLANCK High Frequency Instrument (HFI) data. Specifically, we prepare 100 GHz, 143 GHz, and 217 GHz mock microwave sky maps, which include galactic thermal <span class="hlt">dust</span>, NANTEN CO line, and the cosmic microwave background (CMB) emissions, and then estimate the independent <span class="hlt">components</span> based on the kurtosis. We find that FastICA can successfully estimate the CO <span class="hlt">component</span> as the first independentmore » <span class="hlt">component</span> in our deflection algorithm because its distribution has the largest degree of non-Gaussianity among the <span class="hlt">components</span>. Thus, FastICA can be a promising technique to extract CO-like <span class="hlt">components</span> without prior assumptions about their distributions and frequency dependences.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23252479','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23252479"><span>Controlling <span class="hlt">dust</span> from concrete saw cutting.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Shepherd, Susan; Woskie, Susan</p> <p>2013-01-01</p> <p>Cutting concrete with gas-powered saws is ubiquitous in the construction industry and a source of exposure to respirable crystalline silica. Volunteers from the New England Laborers Training Center were recruited to participate in a field experiment examining <span class="hlt">dust</span> reductions through the use of water, from a hose and from a sprayer, as a <span class="hlt">dust</span> control. In four series of tests, reinforced concrete pipe was cut under both "dry" and "wet" control conditions. Overall, the geometric mean respirable <span class="hlt">dust</span> concentration for "dry" cutting (14.396 mg/m³) exceeded both types of water-based controls by more than tenfold. Wet cutting reduced the respirable <span class="hlt">dust</span> concentration by 85% compared with dry cutting when comparing tests paired by person and saw blade (n = 79 pairs). Using a respirable cyclone, a total of 178 samples were taken. Due to the high variability in <span class="hlt">dust</span> exposure found in this and other studies of saw cutting, the data were examined for potential exposure determinants that contribute to that variability. Using mixed models, three fixed effects were statistically significant: control condition, worker experience, and location. A random effect for subject was included in the model to account for repeated measures. When each of the significant fixed effects was included with the random effect, it was apparent that inclusion of worker experience or location reduced the between-worker <span class="hlt">component</span> of exposure variability, while inclusion of control condition (wet vs. dry) explained a large portion of the within-subject variability. Overall, the fixed effect variable for control condition explained the largest fraction of the total exposure variability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19920035418&hterms=carbon+emissions&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dcarbon%2Bemissions','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19920035418&hterms=carbon+emissions&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dcarbon%2Bemissions"><span>Infrared <span class="hlt">dust</span> and millimeter-wave carbon monoxide emission in the Orion region</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bally, John; Langer, William D.; Liu, Weihong</p> <p>1991-01-01</p> <p>The far-infrared <span class="hlt">dust</span> emission seen by the IRAS satellite in the Orion region is analyzed as a function of the local radiation field intensity, and the <span class="hlt">dust</span> temperature and opacity are compared with (C-12)O and (C-13)O emission. The infrared radiation is interpreted within the framework of a single-<span class="hlt">component</span> large grain model and a multicomponent grain model consisting of subpopulations of grains with size-dependent temperatures. A strong dependence of the 100-micron optical depth derived is found using the large grain model on the average line-of-sight <span class="hlt">dust</span> temperature and radiation field. In the hot environment surrounding high-luminosity sources and H II regions, all <span class="hlt">dust</span> along the line-of-sight radiates at 100 microns, and the <span class="hlt">dust</span>-to-gas ratio, based on the 100-micron opacity and I(/C-13/O), appears to be in agreement with the standard value, about 1 percent by mass. A relationship is found between the inferred <span class="hlt">dust</span>-to-gas ratio and the radiation field intensity responsible for heating the <span class="hlt">dust</span> which can be used to estimate the gas column density from the <span class="hlt">dust</span> opacity derived from the 60- and 100-micron IRAS fluxes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140017712','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140017712"><span>Direct Measurement of <span class="hlt">Dust</span> Attenuation in z approx. 1.5 Star-Forming Galaxies from 3D-HST: Implications for <span class="hlt">Dust</span> Geometry and Star Formation Rates</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Price, Sedona H.; Kriek, Mariska; Brammer, Gabriel B; Conroy, Charlie; Schreiber, Natascha M. Foerster; Franx, Marijn; Fumagalli, Mattia; Lundren, Britt; Momcheva, Ivelina; Nelson, Erica J.; <a style="text-decoration: none; " href="javascript:void(0); " onClick="displayelement('author_20140017712'); toggleEditAbsImage('author_20140017712_show'); toggleEditAbsImage('author_20140017712_hide'); "> <img style="display:inline; width:12px; height:12px; " src="images/arrow-up.gif" width="12" height="12" border="0" alt="hide" id="author_20140017712_show"> <img style="width:12px; height:12px; display:none; " src="images/arrow-down.gif" width="12" height="12" border="0" alt="hide" id="author_20140017712_hide"></p> <p>2013-01-01</p> <p>The nature of <span class="hlt">dust</span> in distant galaxies is not well understood, and until recently few direct <span class="hlt">dust</span> measurements have been possible. We investigate <span class="hlt">dust</span> in distant star-forming galaxies using near-infrared grism spectra of the 3D-HST survey combined with archival multi-wavelength photometry. These data allow us to make a direct comparison between <span class="hlt">dust</span> towards star-forming regions (measured using Balmer decrements) and the integrated <span class="hlt">dust</span> properties (derived by comparing spectral energy distributions [SEDs] with stellar population and <span class="hlt">dust</span> models) for a statistically significant sample of distant galaxies. We select a sample of 163 galaxies between 1.36< or = z< or = 1.5 with H(alpha) SNR > or = 5 and measure Balmer decrements from stacked spectra. First, we stack spectra in bins of integrated stellar <span class="hlt">dust</span> attenuation, and find that there is extra <span class="hlt">dust</span> extinction towards star-forming regions (AV,HII is 1.81 times the integrated AV, star), though slightly lower than found for low-redshift starburst galaxies. Next, we stack spectra in bins of specific star formation rate (log sSFR), star formation rate (log SFR), and stellar mass (logM*). We find that on average AV,HII increases with SFR and mass, but decreases with increasing sSFR. The amount of extra extinction also decreases with increasing sSFR and decreasing stellar mass. Our results are consistent with the two-phase <span class="hlt">dust</span> model - in which galaxies contain both a diffuse and a stellar birth cloud <span class="hlt">dust</span> <span class="hlt">component</span> - as the extra extinction will increase once older stars outside the star-forming regions become more dominant. Finally, using our Balmer decrements we derive <span class="hlt">dust</span>-corrected H(alpha) SFRs, and find evidence that SED fitting produces incorrect SFRs if very rapidly declining SFHs are included in the explored parameter space. Subject headings: <span class="hlt">dust</span>, extinction- galaxies: evolution- galaxies: high-redshift</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018MNRAS.473.2633K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018MNRAS.473.2633K"><span>Modelling of mid-infrared interferometric signature of hot exozodiacal <span class="hlt">dust</span> emission</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kirchschlager, Florian; Wolf, Sebastian; Brunngräber, Robert; Matter, Alexis; Krivov, Alexander V.; Labdon, Aaron</p> <p>2018-01-01</p> <p>Hot exozodiacal <span class="hlt">dust</span> emission was detected in recent surveys around two dozen main-sequence stars at distances of less than 1 au using the H- and K-band interferometry. Due to the high contrast as well as the small angular distance between the circumstellar <span class="hlt">dust</span> and the star, direct observation of this <span class="hlt">dust</span> <span class="hlt">component</span> is challenging. An alternative way to explore the hot exozodiacal <span class="hlt">dust</span> is provided by mid-infrared interferometry. We analyse the L, M and N bands interferometric signature of this emission in order to find stronger constraints for the properties and the origin of the hot exozodiacal <span class="hlt">dust</span>. Considering the parameters of nine debris disc systems derived previously, we model the discs in each of these bands. We find that the M band possesses the best conditions to detect hot <span class="hlt">dust</span> emission, closely followed by L and N bands. The hot <span class="hlt">dust</span> in three systems - HD 22484 (10 Tau), HD 102647 (β Leo) and HD 177724 (ζ Aql) - shows a strong signal in the visibility functions, which may even allow one to constrain the <span class="hlt">dust</span> location. In particular, observations in the mid-infrared could help to determine whether the <span class="hlt">dust</span> piles up at the sublimation radius or is located at radii up to 1 au. In addition, we explore observations of the hot exozodiacal <span class="hlt">dust</span> with the upcoming mid-infrared interferometer Multi AperTure mid-Infrared SpectroScopic Experiment (MATISSE) at the Very Large Telescope Interferometer.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150002145','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150002145"><span>Operational <span class="hlt">Dust</span> Prediction</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Benedetti, Angela; Baldasano, Jose M.; Basart, Sara; Benincasa, Francesco; Boucher, Olivier; Brooks, Malcolm E.; Chen, Jen-Ping; Colarco, Peter R.; Gong, Sunlin; Huneeus, Nicolas; <a style="text-decoration: none; " href="javascript:void(0); " onClick="displayelement('author_20150002145'); toggleEditAbsImage('author_20150002145_show'); toggleEditAbsImage('author_20150002145_hide'); "> <img style="display:inline; width:12px; height:12px; " src="images/arrow-up.gif" width="12" height="12" border="0" alt="hide" id="author_20150002145_show"> <img style="width:12px; height:12px; display:none; " src="images/arrow-down.gif" width="12" height="12" border="0" alt="hide" id="author_20150002145_hide"></p> <p>2014-01-01</p> <p>Over the last few years, numerical prediction of <span class="hlt">dust</span> aerosol concentration has become prominent at several research and operational weather centres due to growing interest from diverse stakeholders, such as solar energy plant managers, health professionals, aviation and military authorities and policymakers. <span class="hlt">Dust</span> prediction in numerical weather prediction-type models faces a number of challenges owing to the complexity of the system. At the centre of the problem is the vast range of scales required to fully account for all of the physical processes related to <span class="hlt">dust</span>. Another limiting factor is the paucity of suitable <span class="hlt">dust</span> observations available for model, evaluation and assimilation. This chapter discusses in detail numerical prediction of <span class="hlt">dust</span> with examples from systems that are currently providing <span class="hlt">dust</span> forecasts in near real-time or are part of international efforts to establish daily provision of <span class="hlt">dust</span> forecasts based on multi-model ensembles. The various models are introduced and described along with an overview on the importance of <span class="hlt">dust</span> prediction activities and a historical perspective. Assimilation and evaluation aspects in <span class="hlt">dust</span> prediction are also discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/20752366-scavenging-pollutant-acid-substances-asian-mineral-dust-particles-article-l07816','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/20752366-scavenging-pollutant-acid-substances-asian-mineral-dust-particles-article-l07816"><span>Scavenging of pollutant acid substances by Asian mineral <span class="hlt">dust</span> particles - article no. L07816</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Matsumoto, J.; Takahashi, K.; Matsumi, Y.</p> <p>2006-04-13</p> <p>Uptakes of sulfate and nitrate onto Asian <span class="hlt">dust</span> particles during transport from the Asian continent to the Pacific Ocean were analyzed by using a single-particle time-of-flight mass spectrometer. Observation was conducted at Tsukuba in Japan in the springtime of 2004. Sulfate-rich <span class="hlt">dust</span> particles made their largest contribution during the '<span class="hlt">dust</span> event' in the middle of April 2004. As a result of detailed analysis including backward trajectory calculations, it was confirmed that sulfate <span class="hlt">components</span> originating from coal combustion in the continent were internally mixed with <span class="hlt">dust</span> particles. Even in the downstream of the outflow far from the continental coastline, significant contributionmore » of Asian <span class="hlt">dust</span> to sulfate was observed. Asian <span class="hlt">dust</span> plays critical roles as the carrier of sulfate over the Pacific Ocean.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29681689','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29681689"><span>Influence of specific surface area on coal <span class="hlt">dust</span> explosibility using the 20-L chamber.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zlochower, Isaac A; Sapko, Michael J; Perera, Inoka E; Brown, Connor B; Harris, Marcia L; Rayyan, Naseem S</p> <p>2018-07-01</p> <p>The relationship between the explosion inerting effectiveness of rock <span class="hlt">dusts</span> on coal <span class="hlt">dusts</span>, as a function of the specific surface area (cm 2 /g) of each <span class="hlt">component</span> is examined through the use of 20-L explosion chamber testing. More specifically, a linear relationship is demonstrated for the rock <span class="hlt">dust</span> to coal <span class="hlt">dust</span> (or incombustible to combustible) content of such inerted mixtures with the specific surface area of the coal and the inverse of that area of the rock <span class="hlt">dust</span>. Hence, the inerting effectiveness, defined as above, is more generally linearly dependent on the ratio of the two surface areas. The focus on specific surface areas, particularly of the rock <span class="hlt">dust</span>, provide supporting data for minimum surface area requirements in addition to the 70% less than 200 mesh requirement specified in 30 CFR 75.2.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014prdu.book.....A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014prdu.book.....A"><span>Protoplanetary <span class="hlt">Dust</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Apai, D.´niel; Lauretta, Dante S.</p> <p>2014-02-01</p> <p>Preface; 1. Planet formation and protoplanetary <span class="hlt">dust</span> Daniel Apai and Dante Lauretta; 2. The origins of protoplanetary <span class="hlt">dust</span> and the formation of accretion disks Hans-Peter Gail and Peter Hope; 3. Evolution of protoplanetary disk structures Fred Ciesla and Cornelius P. Dullemond; 4. Chemical and isotopic evolution of the solar nebula and protoplanetary disks Dmitry Semenov, Subrata Chakraborty and Mark Thiemens; 5. Laboratory studies of simple <span class="hlt">dust</span> analogs in astrophysical environments John R. Brucato and Joseph A. Nuth III; 6. <span class="hlt">Dust</span> composition in protoplanetaty <span class="hlt">dust</span> Michiel Min and George Flynn; 7. <span class="hlt">Dust</span> particle size evolution Klaus M. Pontoppidan and Adrian J. Brearly; 8. Thermal processing in protoplanetary nebulae Daniel Apai, Harold C. Connolly Jr. and Dante S. Lauretta; 9. The clearing of protoplanetary disks and of the protosolar nebula Ilaira Pascucci and Shogo Tachibana; 10. Accretion of planetesimals and the formation of rocky planets John E. Chambers, David O'Brien and Andrew M. Davis; Appendixes; Glossary; Index.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ThApC.124..451C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ThApC.124..451C"><span>Comparison of characteristics of aerosol during rainy weather and cold air-<span class="hlt">dust</span> weather in Guangzhou in late March 2012</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chen, Huizhong; Wu, Dui; Yu, Jianzhen</p> <p>2016-04-01</p> <p>Using the data on aerosol observed hourly by Marga ADI 2080 and Grimm 180, we compared the characteristics of aerosol during rainy weather and cold air-<span class="hlt">dust</span> weather in Guangzhou in late March 2012. The mass concentration of aerosol appeared distinct between the two weather processes. During rainy weather, the mass concentration of PM and total water-soluble <span class="hlt">components</span> decreased obviously. During cold air-<span class="hlt">dust</span> weather, the cleaning effect of cold air occurred much more suddenly and about a half day earlier than the <span class="hlt">dust</span> effect. As a result, the mass concentration of PM and total water-soluble <span class="hlt">components</span> first dropped dramatically to a below-normal level and then rose gradually to an above-normal level. The ratio of PM2.5/PM10 and PM1/PM10 decreased, suggesting that <span class="hlt">dust</span>-storm weather mainly brought in coarse particles. The proportion of Ca2+ in the total water-soluble <span class="hlt">components</span> significantly increased to as high as 50 % because of the effect of <span class="hlt">dust</span> weather. We further analysed the ionic equilibrium during rainy and cold air-<span class="hlt">dust</span> weather, and compared it with that during hazy weather during the same period. The aerosol during rainy weather was slightly acidic, whereas that during hazy weather and cold air-<span class="hlt">dust</span> weather was obviously alkaline, with that during cold air-<span class="hlt">dust</span> weather being significantly more alkaline. Most of the anions, including SO4 2- and NO3 -, were neutralised by NH4 + during rainy and hazy weather, and by Ca2+ during cold air-<span class="hlt">dust</span> weather.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1999smtp.conf...66M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1999smtp.conf...66M"><span>The MECA Payload as a <span class="hlt">Dust</span> Analysis Laboratory on the MSP 2001 Lander</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Marshall, J.; Anderson, M.; Buehler, M.; Frant, M.; Fuerstenau, S.; Hecht, M.; Keller, U.; Markiewicz, W.; Meloy, T.; Pike, T.</p> <p>1999-09-01</p> <p>In a companion abstract, the "Mars Environmental Compatibility Assessment" (MECA) payload for Mars Surveyor Program 2001 (MSP 2001) is described in terms of its capabilities for addressing exobiology on Mars. Here we describe how the same payload elements perform in terms of gathering data about surface <span class="hlt">dust</span> on the planet. An understanding of the origin and properties of <span class="hlt">dust</span> is important to both human exploration and planetary geology. The MECA instrument is specifically designed for soil/<span class="hlt">dust</span> investigations: it is a multifunctional laboratory equipped to assess particulate properties with wet chemistry, camera imagery, optical microscopy (potentially with LTV fluorescence capability), atomic force microscopy (AFM; potentially with mineral-discrimination capabilities), electrometry, active & passive external materials-test panels, mineral hardness testing, and electrostatic & magnetic materials testing. Additionally, evaluation of soil chemical and physical properties as a function of depth down to about 50 cm will be facilitated by the Lander/MECA robot arm on which the camera (RAC) and electrometer are mounted. Types of data being sought for the <span class="hlt">dust</span> include: (1) general textural and grain-size characterization of the soil as a whole --for example, is the soil essentially <span class="hlt">dust</span> with other <span class="hlt">components</span> or is it a clast-supported material in which <span class="hlt">dust</span> resides only in the clast interstices, (2) size frequency distribution for <span class="hlt">dust</span> particles in the range 0.01 to 10.00 microns, (3) particle-shape distribution of the soil <span class="hlt">components</span> and of the fine <span class="hlt">dust</span> fraction in particular, (4) soil fabric such as grain clustering into clods, aggregates, and cemented/indurated grain amalgamations, as well as related porosity, cohesiveness, and other mechanical soil properties, (5) cohesive relationship that <span class="hlt">dust</span> has to certain types of rocks and minerals as a clue to which soil materials may be prime hosts for <span class="hlt">dust</span> "piggybacking", (6) particle, aggregate, and bulk soil electrostatic</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20000025381&hterms=DIRT&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DDIRT','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20000025381&hterms=DIRT&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DDIRT"><span>The MECA Payload as a <span class="hlt">Dust</span> Analysis Laboratory on the MSP 2001 Lander</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Marshall, J.; Anderson, M.; Buehler, M.; Frant, M.; Fuerstenau, S.; Hecht, M.; Keller, U.; Markiewicz, W.; Meloy, T.; Pike, T.</p> <p>1999-01-01</p> <p>In a companion abstract, the "Mars Environmental Compatibility Assessment" (MECA) payload for Mars Surveyor Program 2001 (MSP 2001) is described in terms of its capabilities for addressing exobiology on Mars. Here we describe how the same payload elements perform in terms of gathering data about surface <span class="hlt">dust</span> on the planet. An understanding of the origin and properties of <span class="hlt">dust</span> is important to both human exploration and planetary geology. The MECA instrument is specifically designed for soil/<span class="hlt">dust</span> investigations: it is a multifunctional laboratory equipped to assess particulate properties with wet chemistry, camera imagery, optical microscopy (potentially with LTV fluorescence capability), atomic force microscopy (AFM; potentially with mineral-discrimination capabilities), electrometry, active & passive external materials-test panels, mineral hardness testing, and electrostatic & magnetic materials testing. Additionally, evaluation of soil chemical and physical properties as a function of depth down to about 50 cm will be facilitated by the Lander/MECA robot arm on which the camera (RAC) and electrometer are mounted. Types of data being sought for the <span class="hlt">dust</span> include: (1) general textural and grain-size characterization of the soil as a whole --for example, is the soil essentially <span class="hlt">dust</span> with other <span class="hlt">components</span> or is it a clast-supported material in which <span class="hlt">dust</span> resides only in the clast interstices, (2) size frequency distribution for <span class="hlt">dust</span> particles in the range 0.01 to 10.00 microns, (3) particle-shape distribution of the soil <span class="hlt">components</span> and of the fine <span class="hlt">dust</span> fraction in particular, (4) soil fabric such as grain clustering into clods, aggregates, and cemented/indurated grain amalgamations, as well as related porosity, cohesiveness, and other mechanical soil properties, (5) cohesive relationship that <span class="hlt">dust</span> has to certain types of rocks and minerals as a clue to which soil materials may be prime hosts for <span class="hlt">dust</span> "piggybacking", (6) particle, aggregate, and bulk soil electrostatic</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20020050364&hterms=iso&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Diso','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20020050364&hterms=iso&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Diso"><span>New <span class="hlt">Dust</span> Features Observed with ISO</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Tielens, Alexander G. G. M.; Young, Richard E. (Technical Monitor)</p> <p>1997-01-01</p> <p>This paper will review our current knowledge of circumstellar and interstellar <span class="hlt">dust</span> with the emphasis on infrared spectroscopy with ISO. Objects embedded in or located behind molecular clouds show a wealth of absorption features due to simple molecules in an icy mantle. The SWS on ISO has provided us, for the first time, with complete 3-45 um spectra which allow an inventory of interstellar ice. Among the species identified are H2O, CH3OH, CH4, CO2, CO, and OCS. These species are formed through simple reactions among gas phase species accreted on grain surfaces, possibly modified by FUV photolysis and <span class="hlt">warm</span>-up (ie., outgassing). The implications of the observations for our understanding of these processes will be reviewed. The IR spectra of many UV bright objects are dominated by strong emission features at 3.3, 6.2, 7.7, and 11.3 micrometers. These are generally attributed to Polycyclic Aromatic Hydrocarbons (PAHs) molecules. The observational evidence will be reviewed. The emphasis will be on recent data which show widespread spectral variations, particularly among protoplanetary and planetary nebulae, and their implications. One of the most exciting, recent discoveries on interstellar and circumstellar <span class="hlt">dust</span> has been the detection of spectral structure due to crystalline olivine and enstatite in a variety of objects surrounded by circumstellar silicates. These spectra will be reviewed and circumstellar silicate mineralogy will be discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010CSR....30.1108O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010CSR....30.1108O"><span>Biological response to coastal upwelling and <span class="hlt">dust</span> deposition in the area off Northwest Africa</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ohde, T.; Siegel, H.</p> <p>2010-05-01</p> <p>Nutrient supply in the area off Northwest Africa is mainly regulated by two processes, coastal upwelling and deposition of Saharan <span class="hlt">dust</span>. In the present study, both processes were analyzed and evaluated by different methods, including cross-correlation, multiple correlation, and event statistics, using remotely sensed proxies of the period from 2000 to 2008 to investigate their influence on the marine environment. The remotely sensed chlorophyll- a concentration was used as a proxy for the phytoplankton biomass stimulated by nutrient supply into the euphotic zone from deeper water layers and from the atmosphere. Satellite-derived alongshore wind stress and sea-surface temperature were applied as proxies for the strength and reflection of coastal upwelling processes. The westward wind and the <span class="hlt">dust</span> <span class="hlt">component</span> of the aerosol optical depth describe the transport direction of atmospheric <span class="hlt">dust</span> and the atmospheric <span class="hlt">dust</span> column load. Alongshore wind stress and induced upwelling processes were most significantly responsible for the surface chlorophyll- a variability, accounting for about 24% of the total variance, mainly in the winter and spring due to the strong north-easterly trade winds. The remotely sensed proxies allowed determination of time lags between biological response and its forcing processes. A delay of up to 16 days in the surface chlorophyll- a concentration due to the alongshore wind stress was determined in the northern winter and spring. Although input of atmospheric iron by <span class="hlt">dust</span> storms can stimulate new phytoplankton production in the study area, only 5% of the surface chlorophyll- a variability could be ascribed to the <span class="hlt">dust</span> <span class="hlt">component</span> in the aerosol optical depth. All strong desert storms were identified by an event statistics in the time period from 2000 to 2008. The 57 strong storms were studied in relation to their biological response. Six events were clearly detected in which an increase of chlorophyll- a was caused by Saharan <span class="hlt">dust</span> input and not by</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.acs.org/doi/abs/10.1021/bk-2006-0919.ch005','USGSPUBS'); return false;" href="http://pubs.acs.org/doi/abs/10.1021/bk-2006-0919.ch005"><span>Materials characterization of <span class="hlt">dusts</span> generated by the collapse of the World Trade Center</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Meeker, Gregory P.; Sutley, Stephen J.; Brownfield, Isabelle; Lowers, Heather; Bern, Amy M.; Swayze, Gregg A.; Hoefen, Todd M.; Plumlee, Geoffrey S.; Clark, Roger N.; Gent, Carol A.</p> <p>2009-01-01</p> <p>The major inorganic <span class="hlt">components</span> of the <span class="hlt">dusts</span> generated from the collapse of the World Trade Center buildings on September 11, 2001 were concrete materials, gypsum, and man-made vitreous fibers. These <span class="hlt">components</span> were likely derived from lightweight Portland cement concrete floors, gypsum wallboard, and spray-on fireproofing and ceiling tiles, respectively. All of the 36 samples collected by the USGS team had these materials as the three major inorganic <span class="hlt">components</span> of the <span class="hlt">dust</span>. <span class="hlt">Components</span> found at minor and trace levels include chrysotile asbestos, lead, crystalline silica, and particles of iron and zinc oxides. Other heavy metals, such as lead, bismuth, copper, molybdenum, chromium, and nickel, were present at much lower levels occurring in a variety of chemical forms. Several of these materials have health implications based on their chemical composition, morphology, and bioaccessibility.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70032393','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70032393"><span>Measurements of Martian <span class="hlt">dust</span> devil winds with HiRISE</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Choi, D.S.; Dundas, C.M.</p> <p>2011-01-01</p> <p>We report wind measurements within Martian <span class="hlt">dust</span> devils observed in plan view from the High Resolution Imaging Science Experiment (HiRISE) orbiting Mars. The central color swath of the HiRISE instrument has three separate charge-coupled devices (CCDs) and color filters that observe the surface in rapid cadence. Active features, such as <span class="hlt">dust</span> devils, appear in motion when observed by this region of the instrument. Our image animations reveal clear circulatory motion within <span class="hlt">dust</span> devils that is separate from their translational motion across the Martian surface. Both manual and automated tracking of <span class="hlt">dust</span> devil clouds reveal tangential winds that approach 20-30 m s -1 in some cases. These winds are sufficient to induce a ???1% decrease in atmospheric pressure within the <span class="hlt">dust</span> devil core relative to ambient, facilitating <span class="hlt">dust</span> lifting by reducing the threshold wind speed for particle elevation. Finally, radial velocity profiles constructed from our automated measurements test the Rankine vortex model for <span class="hlt">dust</span> devil structure. Our profiles successfully reveal the solid body rotation <span class="hlt">component</span> in the interior, but fail to conclusively illuminate the profile in the outer regions of the vortex. One profile provides evidence for a velocity decrease as a function of r -1/2, instead of r -1, suggestive of surface friction effects. However, other profiles do not support this observation, or do not contain enough measurements to produce meaningful insights. Copyright 2011 by the American Geophysical Union.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20020066641','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20020066641"><span>Studies of <span class="hlt">Dust</span> Emission as Measured by DIRBE and IRAS</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Davis, Marc</p> <p>2002-01-01</p> <p>The main activity supported by this grant was to make the <span class="hlt">dust</span> reddening map more useful for optical and microwave astronomy, and to increase our understanding of interstellar <span class="hlt">dust</span> in general. We completed all the major objectives of the proposal, and we are eagerly awaiting the launch of Space Infrared Telescope Facility (SIRTF) so that we can check one of our most controversial conclusions. According to the ADS abstract service, the above paper has been cited 895 times. A number of authors have claimed the SFD98 <span class="hlt">dust</span> maps are miscalibrated, but recent work suggests that the calibration is correct. The primary goal of this ADP grant was to determine the microwave / sum-mm spectrum of interstellar <span class="hlt">dust</span> emission by cross-correlating the Far Infrared Absolute Spectrophotometer (FIRAS) spectra with a model based on the SFD98 <span class="hlt">dust</span> map. Because of temperature variation, large (factor of two) variations are observed in submillimeter / 100 micron ratio, so a careful accounting of <span class="hlt">dust</span> temperature data, based on Diffuse Infrared Background Experiment (DIRBE) 100 and 240 micron channels, was required. Even this improvement was unable to reduce the chi(sup 2) per degree of freedom below 30. Further study revealed that a two-<span class="hlt">component</span> model, with the two <span class="hlt">components</span> having different (but reasonable) optical properties, achieved a decrease in chi(sup 2) to less than 2, five times better than the next best fit in the literature. The resulting model uses density and temperature estimates based on DIRBE data, with only four global parameters fit using the FIRAS data. This dramatic reduction in chi(sup 2) using only four fit parameters may indicate that the model is physically correct, but in any case, it is an acceptable phenomenological model. We have released the appropriate data and software on our website (http://astro.berkeley.edu/<span class="hlt">dust</span>) to allow users to compute the interstellar <span class="hlt">dust</span> emission between from 100-3000 GHz (or 100 micron 3 mm) with approx. 15% precision. The paper</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110011724','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110011724"><span>Spitzer IRS Spectroscopy of the 10 Myr-Old EF Cha Debris Disk: Evidence for Phyllosilicate-Rich <span class="hlt">Dust</span> in the Terrestrial Zone</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Currie, Thayne; Lisse, Carey M.; Sicillia-Aguilar, Aurora; Rieke, George H.; Su, Kate Y. L.</p> <p>2011-01-01</p> <p>We describe Spitzer IRS spectroscopic observations of the approx. 10 Myr-old star, EF Chao Compositional modeling of the spectra from 5 micron to 35 micron confirms that it is surrounded by a luminous debris disk with L(sub D)/L(sub *) approx. 10(exp -3), containing <span class="hlt">dust</span> with temperatures between 225 K and 430 K characteristic of the terrestrial zone. The EF Cha spectrum shows evidence for many solid-state features, unlike most cold, low-luminosity debris disks but like some other 10-20 Myr-old luminous, <span class="hlt">warm</span> debris disks (e.g. HD 113766A). The EF Cha debris disk is unusually rich in a species or combination of species whose emissivities resemble that of finely-powdered, laboratory-measured phyllosilicate species (talc, saponite, and smectite), which are likely produced by aqueous alteration of primordial anhydrous rocky materials. The <span class="hlt">dust</span> and, by inference, the parent bodies of the debris also contain abundant amorphous silicates and metal sulfides, and possibly water ice. The <span class="hlt">dust</span>'s total olivine to pyroxene ratio of approx. 2 also provides evidence of aqueous alteration. The large mass volume of grains with sizes comparable to or below the radiation blow-out limit implies that planetesimals may be colliding at a rate high enough to yield the emitting <span class="hlt">dust</span> but not so high as to devolatize the planetesimals via impact processing. Because phyllosilicates are produced by the interactions between anhydrous rock and <span class="hlt">warm</span>, reactive water, EF Cha's disk is a likely signpost for water delivery to the terrestrial zone of a young planetary system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016cems.book..675Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016cems.book..675Y"><span>Study on Dezincification and De-Lead of Blast Furnace <span class="hlt">Dust</span> by Fluidized Reduction Experiment</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yang, Shufeng; Liu, Chengsong; Gao, Xiaojie; Li, Jingshe</p> <p></p> <p>In the blast furnace process, the <span class="hlt">dust</span> entrained in the blast furnace gas enters into the down-comer, flows through the gravity <span class="hlt">dust</span> separator (to eliminate coarse particles) and then is collected in a bag-house. The powder collected by the baghouse is called bag <span class="hlt">dust</span>, while both fractions are called blast furnace <span class="hlt">dust</span> whose main <span class="hlt">components</span> are C and Fe. The <span class="hlt">dust</span> also contains small amounts of nonferrous metals such as Zn and Pb, which have some value. Also, due to the small particle size and low density the <span class="hlt">dust</span> is easily suspended in air and so can endanger human health. Therefore it is necessary to develop a process to both treat the <span class="hlt">dust</span> to recover the metal values and to dispose of the residue — preferably by recycling to the blast furnace itself via the sinter strand. These objectives will result in good economic, environmental and social benefits [1].</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.9173K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.9173K"><span><span class="hlt">Dust</span> devil characteristics and associated <span class="hlt">dust</span> entrainment based on large-eddy simulations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Klose, Martina; Kwidzinski, Nick; Shao, Yaping</p> <p>2015-04-01</p> <p>The characteristics of <span class="hlt">dust</span> devils, such as occurrence frequency, lifetime, size, and intensity, are usually inferred from in situ field measurements and remote sensing. Numerical models, e.g. large-eddy simulation (LES) models, have also been established as a tool to investigate <span class="hlt">dust</span> devils and their structures. However, most LES models do not contain a <span class="hlt">dust</span> module. Here, we present results from simulations using the WRF-LES model coupled to the convective turbulent <span class="hlt">dust</span> emission (CTDE) scheme of Klose et al. (2014). The scheme describes the stochastic process of aerodynamic <span class="hlt">dust</span> entrainment in the absence of saltation. It therefore allows for <span class="hlt">dust</span> emission even below the threshold friction velocity for saltation. Numerical experiments have been conducted for different atmospheric stability and background wind conditions at 10 m horizontal resolution. A <span class="hlt">dust</span> devil tracking algorithm is used to identify <span class="hlt">dust</span> devils in the simulation results. The detected <span class="hlt">dust</span> devils are statistically analyzed with regard to e.g. radius, pressure drop, lifetime, and turbulent wind speeds. An additional simulation with higher horizontal resolution (2 m) is conducted for conditions, which are especially favorable for <span class="hlt">dust</span> devil development, i.e. unstable atmospheric stratification and weak mean winds. The higher resolution enables the identification of smaller <span class="hlt">dust</span> devils and a more detailed structure analysis. <span class="hlt">Dust</span> emission fluxes, <span class="hlt">dust</span> concentrations, and <span class="hlt">dust</span> mass budgets are calculated from the simulations. The results are compared to field observations reported in literature.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19910005584','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19910005584"><span>Interstellar <span class="hlt">Dust</span>: Contributed Papers</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Tielens, Alexander G. G. M. (Editor); Allamandola, Louis J. (Editor)</p> <p>1989-01-01</p> <p>A coherent picture of the <span class="hlt">dust</span> composition and its physical characteristics in the various phases of the interstellar medium was the central theme. Topics addressed included: <span class="hlt">dust</span> in diffuse interstellar medium; overidentified infrared emission features; <span class="hlt">dust</span> in dense clouds; <span class="hlt">dust</span> in galaxies; optical properties of <span class="hlt">dust</span> grains; interstellar <span class="hlt">dust</span> models; interstellar <span class="hlt">dust</span> and the solar system; <span class="hlt">dust</span> formation and destruction; UV, visible, and IR observations of interstellar extinction; and quantum-statistical calculations of IR emission from highly vibrationally excited polycyclic aromatic hydrocarbon (PAH) molecules.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29667527','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29667527"><span>Comparison of the physical and chemical characteristics of fine road <span class="hlt">dust</span> at different urban sites.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lee, Kwang Yul; Batmunkh, Tsatsral; Joo, Hung Soo; Park, Kihong</p> <p>2018-04-18</p> <p>The size distribution and chemical <span class="hlt">components</span> of a fine fraction (<2.5 μm) of road <span class="hlt">dust</span> collected at urban sites in Korea (Gwangju) and Mongolia (Ulaanbaatar) where distinct urban characteristics exist were measured. A clear bimodal size distribution was observed for the resuspended fine road <span class="hlt">dust</span> at the urban sites in Korea. The first mode peaked at 100-110 nm, and the second peak was observed at 435-570 nm. Ultrafine mode (~30 nm) was found for the fine road <span class="hlt">dust</span> at the Mongolia site, which was significantly affected by residential coal/biomass burning. The contribution of the water-soluble ions to the fine road <span class="hlt">dust</span> was higher at the sites in Mongolia (15.8-16.8%) than at those in Korea (1.2-4.8%). Sulfate and chloride were the most dominant ionic species for the fine road <span class="hlt">dust</span> in Mongolia. As (arsenic) was also much higher for the Mongolian road <span class="hlt">dust</span> than the others. The sulfate, chloride, and As mainly come from coal burning activity, suggesting that coal and biomass combustion in Mongolia during the heating season should affect the size and chemical <span class="hlt">components</span> of the fine road <span class="hlt">dust</span>. Cu (copper) and Zn (zinc), carbonaceous particles (organic carbon [OC] and elemental carbon [EC]) increased at sites in Korea, suggesting that the fine road <span class="hlt">dust</span> at these sites was significantly affected by the high volume of traffic (engine emission and brake/tire wear). Our results suggest that chemical profiles for road <span class="hlt">dust</span> specific to certain sites should be applied to more accurately apportion road <span class="hlt">dust</span> source contributing to the ambient particulate matter. Size and chemical characteristics of fine road <span class="hlt">dust</span> at sites having distinct urban characteristics were examined. Residential coal and biomass burning and traffic affected physiochemical properties of the fine road <span class="hlt">dust</span>. Different road <span class="hlt">dust</span> profiles at different sites should be needed to determine the ambient PM2.5 sources more accurately.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PPCF...57a4037F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PPCF...57a4037F"><span>Characterising <span class="hlt">dust</span> in JET with the new ITER-like wall</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Flanagan, J. C.; Sertoli, M.; Bacharis, M.; Matthews, G. F.; de Vries, P. C.; Widdowson, A.; Coffey, I. H.; Arnoux, G.; Sieglin, B.; Brezinsek, S.; Coenen, J. W.; Marsen, S.; Craciunescu, T.; Murari, A.; Harting, D.; Cackett, A.; Hodille, E.</p> <p>2015-01-01</p> <p>Recent studies dedicated to the characterisation of in-vessel <span class="hlt">dust</span> in JET with the new ITER-like wall (ILW) show that <span class="hlt">dust</span> levels are orders of magnitude lower compared with the latter stages of the carbon-wall (CW) period and are decreasing with operational time. Less than 1 g of <span class="hlt">dust</span> was recovered in a recent inspection, compared with more than 200 g of material recovered at the end of the JET-CW life. Recent inspection of the ILW shows low rates of re-deposition with only small areas of damage of a type likely to create particulate matter. Quantifiers from laser scattering techniques also indicate an order of magnitude reduction in <span class="hlt">dust</span> relative to the JET-CW and show that the amount of <span class="hlt">dust</span> mobilized after a disruption is proportional to the dynamic vessel forces. It is not possible to infer what fraction of <span class="hlt">dust</span> (if any) might be created by disruptions. However, disruption mitigation is found to reduce the amount of <span class="hlt">dust</span> seen after moderate disruptions by a factor of 4. Analysis of the transient impurity events (TIEs) associated with <span class="hlt">dust</span> show that tungsten dominates. A significant contribution to TIEs is also seen from iron, nickel and chromium (probably from steel and Inconel <span class="hlt">components</span>). The incidence of severe negative effects on operations from TIEs is found to be relatively rare, with <1% of ILW disruptions linked to TIEs. The evolution of the TIE rate closely follows changes in the laser scattering <span class="hlt">dust</span> quantifiers; both trend downwards in time but peak during periods of higher disruption rate (thought to be primarily driven by the mobilization of existing <span class="hlt">dust</span>).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://lsn.nei.org/NEIEXTL0718.pdf','USGSPUBS'); return false;" href="http://lsn.nei.org/NEIEXTL0718.pdf"><span>Lead isotopes and trace metals in <span class="hlt">dust</span> at Yucca Mountain</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Kwak, Loretta; Neymark, Leonid A.; Peterman, Zell E.</p> <p>2008-01-01</p> <p>Lead (Pb)-isotope compositions and trace-metal concentrations were determined for samples of <span class="hlt">dust</span> collected from underground and surface locations at and near the proposed radioactive waste repository at Yucca Mountain, Nevada. Rare earth element concentrations in the <span class="hlt">dust</span> samples from the underground tunnels are similar to those in wholerock samples of the repository host rocks (Miocene Tiva Canyon Tuff and Topopah Spring Tuff), supporting interpretation that the subsurface <span class="hlt">dust</span> is mainly composed of rock comminuted during tunnel construction. Other trace metals (arsenic, cadmium, cobalt, chromium, copper, manganese, nickel, lead, antimony, thallium, and zinc) are variably enriched in the subsurface <span class="hlt">dust</span> samples relative to the average concentrations in the host rocks. Average concentrations of arsenic and lead in <span class="hlt">dust</span> samples, high concentrations of which can cause corrosion of waste canisters, have enrichment factors from 1.2 to 1.6 and are insignificant relative to the range of concentrations for these metals observed in the host rock samples. Most <span class="hlt">dust</span> samples from surface sites also are enriched in many of these trace metals relative to average repository host rocks. At least some of these enrichments may be artifacts of sampling. Plotted on a 208Pb/206Pb-207Pb/206Pb graph, Pb-isotope compositions of <span class="hlt">dust</span> samples from underground sites form a mixing line extending from host-rock Pb-isotope compositions towards compositions of many of the <span class="hlt">dust</span> samples from surface sites; however, combined Pb concentration and isotope data indicate the presence of a Pbenriched <span class="hlt">component</span> in the subsurface <span class="hlt">dust</span> that is not derived from host rock or surface <span class="hlt">dust</span> and may derive from anthropogenic materials introduced into the underground environment.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28336085','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28336085"><span>The dual effect of vegetation green-up date and strong wind on the return period of spring <span class="hlt">dust</span> storms.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Feng, Jieling; Li, Ning; Zhang, Zhengtao; Chen, Xi</p> <p>2017-08-15</p> <p>Vegetation phenology changes have been widely applied in the disaster risk assessments of the spring <span class="hlt">dust</span> storms, and vegetation green-up date shifts have a strong influence on <span class="hlt">dust</span> storms. However, the effect of earlier vegetation green-up dates due to climate <span class="hlt">warming</span> on the evaluation of <span class="hlt">dust</span> storms return periods remains an important, but poorly understood issue. In this study, we evaluate the spring <span class="hlt">dust</span> storm return period (February to June) in Inner Mongolia, Northern China, using 165 observations of severe spring <span class="hlt">dust</span> storm events from 16 weather stations, and regional vegetation green-up dates as an integrated factor from NDVI (Normalized Difference Vegetation Index), covering a period from 1982 to 2007, by building the bivariate Copula model. We found that the joint return period showed better fitting results than without considering the integrated factor when the actual <span class="hlt">dust</span> storm return period is longer than 2years. Also, for extremely severe <span class="hlt">dust</span> storm events, the gap between simulation result and actual return period can be narrowed up to 0.4888years by using integrated factor. Furthermore, the risk map based on the return period results shows that the Mandula, Zhurihe, Sunitezuoqi, Narenbaolige stations are identified as high risk areas. In this study area, land surface is extensively covered by grasses and shrubs, vegetation green-up date can play a significant role in restraining spring <span class="hlt">dust</span> storm outbreaks. Therefore, we suggest that Copula method can become a useful tool for joint return period evaluation and risk analysis of severe <span class="hlt">dust</span> storms. Copyright © 2017 Elsevier B.V. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1740313','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1740313"><span>Pulmonary epithelial response in the rat lung to instilled Montserrat respirable <span class="hlt">dusts</span> and their major mineral <span class="hlt">components</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Housley, D; Berube, K; Jones, T; Anderson, S; Pooley, F; Richards, R</p> <p>2002-01-01</p> <p>Background: The Soufriere Hills, a stratovolcano on Montserrat, started erupting in July 1995, producing volcanic ash, both from dome collapse pyroclastic flows and phreatic explosions. The eruptions/ash resuspension result in high concentrations of suspended particulate matter in the atmosphere, which includes cristobalite, a mineral implicated in respiratory disorders. Aims: To conduct toxicological studies on characterised samples of ash, together with major <span class="hlt">components</span> of the <span class="hlt">dust</span> mixture (anorthite, cristobalite), and a bioreactive mineral control (DQ12 quartz). Methods: Rats were challenged with a single mass (1 mg) dose of particles via intratracheal instillation and groups sacrificed at one, three, and nine weeks. Acute bioreactivity of the particles was assessed by increases in lung permeability and inflammation, changes in epithelial cell markers, and increase in the size of bronchothoracic lymph nodes. Results: Data indicated that respirable ash derived from pyroclastic flows (20.1% cristobalite) or phreatic explosion (8.6% cristobalite) had minimal bioreactivity in the lung. Anorthite showed low bioreactivity, in contrast to pure cristobalite, which showed progressive increases in lung damage. Conclusion: Results suggests that either the percentage mass of cristobalite particles present in Montserrat ash was not sufficient as a catalyst in the lung environment, or its surface reactivity was masked by the non-reactive volcanic glass <span class="hlt">components</span> during the process of ash formation. PMID:12107295</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApJ...831..188G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApJ...831..188G"><span>The Cold <span class="hlt">Dust</span> Content of the Oxygen-rich Supernova Remnant G292.0+1.8</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ghavamian, Parviz; Williams, Brian J.</p> <p>2016-11-01</p> <p>We present far-infrared images of the Galactic oxygen-rich supernova remnant (SNR) G292.0+1.8, acquired with the PACS and SPIRE instruments of the Herschel Space Observatory. We find that the SNR shell is detected in the PACS blue (100 μm) band, but not in the red (160 μm) band, broadly consistent with results from AKARI observations. There is no discernible emission from G292.0+1.8 in SPIRE imagery at 250, 350 and 500 μm. Comparing the 100 μm emission to that observed with Spitzer at 24 and 70 μm, we find a very similar appearance for G292.0+1.8 at all three wavelengths. The infrared emission is dominated by <span class="hlt">dust</span> from non-radiative circumstellar shocks. In addition, the radiatively shocked O-rich clump known as the “Spur” on the eastern side of G292.0+1.8 is clearly detected in the PACS blue images, with marginal detection in the red. Fitting the existing 14-40 μm IRS spectra of the Spur together with photometric measurements from 70 μm MIPS and 100 μm PACS photometry, we place an upper limit of ≲ 0.04 M ⊙ of ejecta <span class="hlt">dust</span> mass in the Spur, under the most conservative assumption that the ejecta <span class="hlt">dust</span> has a temperature of 15 K. Modeling the <span class="hlt">dust</span> continuum in the IRS spectra at four positions around the rim, we estimate post-shock densities ranging from {n}p=3.5 cm-3 to 11 cm-3. The integrated spectrum of the entire SNR, dominated by swept-up circumstellar <span class="hlt">dust</span>, can be fitted with a two-<span class="hlt">component</span> <span class="hlt">dust</span> model with a silicate <span class="hlt">component</span> at 62 K and graphite <span class="hlt">component</span> at 40 K for a total <span class="hlt">dust</span> mass of 0.023 M ⊙.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://medlineplus.gov/ency/patientinstructions/000487.htm','NIH-MEDLINEPLUS'); return false;" href="https://medlineplus.gov/ency/patientinstructions/000487.htm"><span>Allergies, asthma, and <span class="hlt">dust</span></span></a></p> <p><a target="_blank" href="http://medlineplus.gov/">MedlinePlus</a></p> <p></p> <p></p> <p>Reactive airway disease - <span class="hlt">dust</span>; Bronchial asthma - <span class="hlt">dust</span>; Triggers - <span class="hlt">dust</span> ... Things that make allergies or asthma worse are called triggers. <span class="hlt">Dust</span> is a common trigger. When your asthma or allergies become worse due to <span class="hlt">dust</span>, you are ...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22397504','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22397504"><span>Environmental tobacco smoke as a source of polycyclic aromatic hydrocarbons in settled household <span class="hlt">dust</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hoh, Eunha; Hunt, Richard N; Quintana, Penelope J E; Zakarian, Joy M; Chatfield, Dale A; Wittry, Beth C; Rodriguez, Edgar; Matt, Georg E</p> <p>2012-04-03</p> <p>Environmental tobacco smoke is a major contributor to indoor air pollution. <span class="hlt">Dust</span> and surfaces may remain contaminated long after active smoking has ceased (called 'thirdhand' smoke). Polycyclic aromatic hydrocarbons (PAHs) are known carcinogenic <span class="hlt">components</span> of tobacco smoke found in settled house <span class="hlt">dust</span> (SHD). We investigated whether tobacco smoke is a source of PAHs in SHD. House <span class="hlt">dust</span> was collected from 132 homes in urban areas of Southern California. Total PAHs were significantly higher in smoker homes than nonsmoker homes (by concentration: 990 ng/g vs 756 ng/g, p = 0.025; by loading: 1650 ng/m(2) vs 796 ng/m(2), p = 0.012). We also found significant linear correlations between nicotine and total PAH levels in SHD (concentration, R(2) = 0.105; loading, R(2) = 0.385). <span class="hlt">Dust</span> collected per square meter (g/m(2)) was significantly greater in smoker homes and might dilute PAH concentration in SHD inconsistently. Therefore, <span class="hlt">dust</span> PAH loading (ng PAH/m(2)) is a better indicator of PAH content in SHD. House <span class="hlt">dust</span> PAH loadings in the bedroom and living room in the same home were significantly correlated (R(2) = 0.468, p < 0.001) suggesting PAHs are distributed by tobacco smoke throughout a home. In conclusion, tobacco smoke is a source of PAHs in SHD, and tobacco smoke generated PAHs are a <span class="hlt">component</span> of thirdhand smoke.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20090020421&hterms=Skin&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DSkin','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20090020421&hterms=Skin&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DSkin"><span>Aluminum is More Cytotoxic than Lunar <span class="hlt">Dust</span> in Human Skin and Lung Fibroblasts</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hammond, D.; Shehata, T.; Hammond, D.; Shehata, T.; Wise, J.P.; Martino, J; Wise, J.P.; Wise, J.P.</p> <p>2009-01-01</p> <p>NASA plans to build a permanent space station on the moon to explore its surface. The surface of the moon is covered in lunar <span class="hlt">dust</span>, which consists of fine particles that contain silicon, aluminum and titanium, among others. Because this will be a manned base, the potential toxicity of this <span class="hlt">dust</span> has to be studied. Also, toxicity standards for potential exposure have to be set. To properly address the potential toxicity of lunar <span class="hlt">dust</span> we need to understand the toxicity of its individual <span class="hlt">components</span>, as well as their combined effects. In order to study this we compared NASA simulant JSC-1AVF (volcanic ash particles), that simulates the <span class="hlt">dust</span> found on the moon, to aluminum, the 3rd most abundant <span class="hlt">component</span> in lunar <span class="hlt">dust</span>. We tested the cytotoxicity of both compounds on human lung and skin fibroblasts (WTHBF-6 and BJhTERT cell lines, respectively). Aluminum oxide was more cytotoxic than lunar <span class="hlt">dust</span> to both cell lines. In human lung fibroblasts 5, 10 and 50 g/sq cm of aluminum oxide induced 85%, 61% and 30% relative survival, respectively. For human skin fibroblasts the same concentrations induced 58%, 41% and 58% relative survival. Lunar <span class="hlt">dust</span> was also cytotoxic to both cell lines, but its effects were seen at higher concentrations: 50, 100, 200 and 400 g/sq cm of lunar <span class="hlt">dust</span> induced a 69%, 46%, 35% and 30% relative survival in the skin cells and 53%, 16%, 8% and 2% on the lung cells. Overall, for both compounds, lung cells were more sensitive than skin cells. This work was supported by a NASA EPSCoR grant through the Maine Space Grant Consortium (JPW), the Maine Center for Toxicology and Environmental Health., a Fulbright Grant (JM) and a Delta Kappa Gamma Society International World Fellowship (JM).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20080024226','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20080024226"><span>Estimation of Asian <span class="hlt">Dust</span> Aerosol Effect on Cloud Radiation Forcing Using Fu-Liou Radiative Model and CERES Measurements</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Su, Jing; Huang, Jianping; Fu, Qiang; Minnis, Patrick; Ge, Jinming; Bi, Jianrong</p> <p>2008-01-01</p> <p>The impact of Asian <span class="hlt">dust</span> on cloud radiative forcing during 2003-2006 is studied by using the Earth's Radiant Energy Budget Scanner (CERES) data and the Fu-Liou radiative transfer model. Analysis of satellite data shows that the <span class="hlt">dust</span> aerosol significantly reduced the cloud cooling effect at TOA. In <span class="hlt">dust</span> contaminated cloudy regions, the 4-year mean values of the instantaneous shortwave, longwave and net cloud radiative forcing are -138.9, 69.1, and -69.7 Wm(sup -2), which are 57.0, 74.2, and 46.3%, respectively, of the corresponding values in more pristine cloudy regions. The satellite-retrieved cloud properties are significantly different in the dusty regions and can influence the radiative forcing indirectly. The contributions to the cloud radiation forcing by the <span class="hlt">dust</span> direct, indirect and semi-direct effects are estimated using combined satellite observations and Fu-Liou model simulation. The 4-year mean value of combination of indirect and semi-direct shortwave radiative forcing (SWRF) is 82.2 Wm(sup -2), which is 78.4% of the total <span class="hlt">dust</span> effect. The direct effect is only 22.7 Wm(sup -2), which is 21.6% of the total effect. Because both first and second indirect effects enhance cloud cooling, the aerosol-induced cloud <span class="hlt">warming</span> is mainly the result of the semi-direct effect of <span class="hlt">dust</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/CFR-2012-title30-vol1/pdf/CFR-2012-title30-vol1-sec75-1103-7.pdf','CFR2012'); return false;" href="https://www.gpo.gov/fdsys/pkg/CFR-2012-title30-vol1/pdf/CFR-2012-title30-vol1-sec75-1103-7.pdf"><span>30 CFR 75.1103-7 - Electrical <span class="hlt">components</span>; permissibility requirements.</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collectionCfr.action?selectedYearFrom=2012&page.go=Go">Code of Federal Regulations, 2012 CFR</a></p> <p></p> <p>2012-07-01</p> <p>... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Electrical <span class="hlt">components</span>; permissibility... Protection § 75.1103-7 Electrical <span class="hlt">components</span>; permissibility requirements. The electrical <span class="hlt">components</span> of each... <span class="hlt">dust</span> when the electrical power is deenergized as required by § 75.313, but these <span class="hlt">components</span> shall be...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/CFR-2010-title30-vol1/pdf/CFR-2010-title30-vol1-sec75-1103-7.pdf','CFR'); return false;" href="https://www.gpo.gov/fdsys/pkg/CFR-2010-title30-vol1/pdf/CFR-2010-title30-vol1-sec75-1103-7.pdf"><span>30 CFR 75.1103-7 - Electrical <span class="hlt">components</span>; permissibility requirements.</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collectionCfr.action?selectedYearFrom=2010&page.go=Go">Code of Federal Regulations, 2010 CFR</a></p> <p></p> <p>2010-07-01</p> <p>... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Electrical <span class="hlt">components</span>; permissibility... Protection § 75.1103-7 Electrical <span class="hlt">components</span>; permissibility requirements. The electrical <span class="hlt">components</span> of each... <span class="hlt">dust</span> when the electrical power is deenergized as required by § 75.313, but these <span class="hlt">components</span> shall be...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/CFR-2013-title30-vol1/pdf/CFR-2013-title30-vol1-sec75-1103-7.pdf','CFR2013'); return false;" href="https://www.gpo.gov/fdsys/pkg/CFR-2013-title30-vol1/pdf/CFR-2013-title30-vol1-sec75-1103-7.pdf"><span>30 CFR 75.1103-7 - Electrical <span class="hlt">components</span>; permissibility requirements.</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collectionCfr.action?selectedYearFrom=2013&page.go=Go">Code of Federal Regulations, 2013 CFR</a></p> <p></p> <p>2013-07-01</p> <p>... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Electrical <span class="hlt">components</span>; permissibility... Protection § 75.1103-7 Electrical <span class="hlt">components</span>; permissibility requirements. The electrical <span class="hlt">components</span> of each... <span class="hlt">dust</span> when the electrical power is deenergized as required by § 75.313, but these <span class="hlt">components</span> shall be...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/CFR-2014-title30-vol1/pdf/CFR-2014-title30-vol1-sec75-1103-7.pdf','CFR2014'); return false;" href="https://www.gpo.gov/fdsys/pkg/CFR-2014-title30-vol1/pdf/CFR-2014-title30-vol1-sec75-1103-7.pdf"><span>30 CFR 75.1103-7 - Electrical <span class="hlt">components</span>; permissibility requirements.</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collectionCfr.action?selectedYearFrom=2014&page.go=Go">Code of Federal Regulations, 2014 CFR</a></p> <p></p> <p>2014-07-01</p> <p>... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Electrical <span class="hlt">components</span>; permissibility... Protection § 75.1103-7 Electrical <span class="hlt">components</span>; permissibility requirements. The electrical <span class="hlt">components</span> of each... <span class="hlt">dust</span> when the electrical power is deenergized as required by § 75.313, but these <span class="hlt">components</span> shall be...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/CFR-2011-title30-vol1/pdf/CFR-2011-title30-vol1-sec75-1103-7.pdf','CFR2011'); return false;" href="https://www.gpo.gov/fdsys/pkg/CFR-2011-title30-vol1/pdf/CFR-2011-title30-vol1-sec75-1103-7.pdf"><span>30 CFR 75.1103-7 - Electrical <span class="hlt">components</span>; permissibility requirements.</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collectionCfr.action?selectedYearFrom=2011&page.go=Go">Code of Federal Regulations, 2011 CFR</a></p> <p></p> <p>2011-07-01</p> <p>... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Electrical <span class="hlt">components</span>; permissibility... Protection § 75.1103-7 Electrical <span class="hlt">components</span>; permissibility requirements. The electrical <span class="hlt">components</span> of each... <span class="hlt">dust</span> when the electrical power is deenergized as required by § 75.313, but these <span class="hlt">components</span> shall be...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeoRL..43.5501E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeoRL..43.5501E"><span>The role of the atmospheric electric field in the <span class="hlt">dust</span>-lifting process</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Esposito, F.; Molinaro, R.; Popa, C. I.; Molfese, C.; Cozzolino, F.; Marty, L.; Taj-Eddine, K.; Di Achille, G.; Franzese, G.; Silvestro, S.; Ori, G. G.</p> <p>2016-05-01</p> <p>Mineral <span class="hlt">dust</span> particles represent the most abundant <span class="hlt">component</span> of atmospheric aerosol in terms of dry mass. They play a key role in climate and climate change, so the study of their emission processes is of utmost importance. Measurements of <span class="hlt">dust</span> emission into the atmosphere are scarce, so that the <span class="hlt">dust</span> load is generally estimated using models. It is known that the emission process can generate strong atmospheric electric fields. Starting from the data we acquired in the Sahara desert, here, we show for the first time that depending on the relative humidity conditions, electric fields contribute to increase up to a factor of 10 the amount of particles emitted into the atmosphere. This means that electrical forces and humidity are critical quantities in the <span class="hlt">dust</span> emission process and should be taken into account in climate and circulation models to obtain more realistic estimations of the <span class="hlt">dust</span> load in the atmosphere.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22663306-attenuation-modified-dig-dust-seen-m31','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22663306-attenuation-modified-dig-dust-seen-m31"><span>Attenuation Modified by DIG and <span class="hlt">Dust</span> as Seen in M31</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Tomičić, Neven; Kreckel, Kathryn; Schinnerer, Eva</p> <p></p> <p>The spatial distribution of <span class="hlt">dust</span> in galaxies affects the global attenuation, and hence inferred properties, of galaxies. We trace the spatial distribution of <span class="hlt">dust</span> in five approximately kiloparsec fields of M31 by comparing optical attenuation with the total <span class="hlt">dust</span> mass distribution. We measure the attenuation from the Balmer decrement using Integral Field Spectroscopy and the <span class="hlt">dust</span> mass from Herschel far-IR observations. Our results show that M31's <span class="hlt">dust</span> attenuation closely follows a foreground screen model, contrary to what was previously found in other nearby galaxies. By smoothing the M31 data, we find that spatial resolution is not the cause for thismore » difference. Based on the emission-line ratios and two simple models, we conclude that previous models of <span class="hlt">dust</span>/gas geometry need to include a weakly or non-attenuated diffuse ionized gas (DIG) <span class="hlt">component</span>. Due to the variation of <span class="hlt">dust</span> and DIG scale heights with galactic radius, we conclude that different locations in galaxies will have different vertical distributions of gas and <span class="hlt">dust</span> and therefore different measured attenuation. The difference between our result in M31 with that found in other nearby galaxies can be explained by our fields in M31 lying at larger galactic radii than the previous studies that focused on the centers of galaxies.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/864831','DOE-PATENT-XML'); return false;" href="https://www.osti.gov/servlets/purl/864831"><span><span class="hlt">Dust</span> feed mechanism</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Milliman, Edward M.</p> <p>1984-01-01</p> <p>The invention is a <span class="hlt">dust</span> feed device for delivery of a uniform supply of <span class="hlt">dust</span> for long periods of time to an aerosolizing means for production of a <span class="hlt">dust</span> suspension. The device utilizes at least two tandem containers having spiral brushes within the containers which transport the <span class="hlt">dust</span> from a supply to the aerosolizer means.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1474371','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1474371"><span>Carbohydrate and protein contents of grain <span class="hlt">dusts</span> in relation to <span class="hlt">dust</span> morphology.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Dashek, W V; Olenchock, S A; Mayfield, J E; Wirtz, G H; Wolz, D E; Young, C A</p> <p>1986-01-01</p> <p>Grain <span class="hlt">dusts</span> contain a variety of materials which are potentially hazardous to the health of workers in the grain industry. Because the characterization of grain <span class="hlt">dusts</span> is incomplete, we are defining the botanical, chemical, and microbial contents of several grain <span class="hlt">dusts</span> collected from grain elevators in the Duluth-Superior regions of the U.S. Here, we report certain of the carbohydrate and protein contents of <span class="hlt">dusts</span> in relation to <span class="hlt">dust</span> morphology. Examination of the gross morphologies of the <span class="hlt">dusts</span> revealed that, except for corn, each <span class="hlt">dust</span> contained either husk or pericarp (seed coat in the case of flax) fragments in addition to respirable particles. When viewed with the light microscope, the fragments appeared as elongated, pointed structures. The possibility that certain of the fragments within corn, settled, and spring wheat were derived from cell walls was suggested by the detection of pentoses following colorimetric assay of neutralized 2 N trifluoroacetic acid hydrolyzates of these <span class="hlt">dusts</span>. The presence of pentoses together with the occurrence of proteins within water washings of grain <span class="hlt">dusts</span> suggests that glycoproteins may be present within the <span class="hlt">dusts</span>. With scanning electron microscopy, each <span class="hlt">dust</span> was found to consist of a distinct assortment of particles in addition to respirable particles. Small husk fragments and "trichome-like" objects were common to all but corn <span class="hlt">dust</span>. Images FIGURE 4. FIGURE 5. PMID:3709476</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://eosweb.larc.nasa.gov/project/misr/gallery/sahara_dust_storm','SCIGOV-ASDC'); return false;" href="https://eosweb.larc.nasa.gov/project/misr/gallery/sahara_dust_storm"><span>Sahara <span class="hlt">Dust</span></span></a></p> <p><a target="_blank" href="http://eosweb.larc.nasa.gov/">Atmospheric Science Data Center </a></p> <p></p> <p>2013-04-15</p> <p>article title:  Casting Light and Shadows on a Saharan <span class="hlt">Dust</span> Storm     ... ocean and <span class="hlt">dust</span> layer, which are visible in shades of blue and tan, respectively. In the lower panel, heights derived from automated ... cast by the cirrus clouds onto the <span class="hlt">dust</span> (indicated by blue and cyan pixels) provide sufficient spatial contrast for a retrieval of ...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3672903','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3672903"><span>Polycyclic Aromatic Hydrocarbons in Residential <span class="hlt">Dust</span>: Sources of Variability</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Metayer, Catherine; Petreas, Myrto; Does, Monique; Buffler, Patricia A.; Rappaport, Stephen M.</p> <p>2013-01-01</p> <p>Background: There is interest in using residential <span class="hlt">dust</span> to estimate human exposure to environmental contaminants. Objectives: We aimed to characterize the sources of variability for polycyclic aromatic hydrocarbons (PAHs) in residential <span class="hlt">dust</span> and provide guidance for investigators who plan to use residential <span class="hlt">dust</span> to assess exposure to PAHs. Methods: We collected repeat <span class="hlt">dust</span> samples from 293 households in the Northern California Childhood Leukemia Study during two sampling rounds (from 2001 through 2007 and during 2010) using household vacuum cleaners, and measured 12 PAHs using gas chromatography–mass spectrometry. We used a random- and a mixed-effects model for each PAH to apportion observed variance into four <span class="hlt">components</span> and to identify sources of variability. Results: Median concentrations for individual PAHs ranged from 10 to 190 ng/g of <span class="hlt">dust</span>. For each PAH, total variance was apportioned into regional variability (1–9%), intraregional between-household variability (24–48%), within-household variability over time (41–57%), and within-sample analytical variability (2–33%). Regional differences in PAH <span class="hlt">dust</span> levels were associated with estimated ambient air concentrations of PAH. Intraregional differences between households were associated with the residential construction date and the smoking habits of residents. For some PAHs, a decreasing time trend explained a modest fraction of the within-household variability; however, most of the within-household variability was unaccounted for by our mixed-effects models. Within-household differences between sampling rounds were largest when the interval between <span class="hlt">dust</span> sample collections was at least 6 years in duration. Conclusions: Our findings indicate that it may be feasible to use residential <span class="hlt">dust</span> for retrospective assessment of PAH exposures in studies of health effects. PMID:23461863</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013A%26A...555A.128T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013A%26A...555A.128T"><span>Cold <span class="hlt">dust</span> in the giant barred galaxy NGC 1365</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tabatabaei, F. S.; Weiß, A.; Combes, F.; Henkel, C.; Menten, K. M.; Beck, R.; Kovács, A.; Güsten, R.</p> <p>2013-07-01</p> <p>Constraining the physcial properties of <span class="hlt">dust</span> requires observations at submm wavelengths. This will provide important insight into the gas content of galaxies. We mapped NGC 1365 at 870 μm with LABOCA, the Large APEX Bolometer Camera, allowing us to probe the central mass concentration as well as the rate at which the gas flows to the center. We obtained the <span class="hlt">dust</span> physical properties both globally and locally for different locations in the galaxy. A 20 K modified black body represents about 98% of the total <span class="hlt">dust</span> content of the galaxy, the rest can be represented by a warmer <span class="hlt">dust</span> <span class="hlt">component</span> of 40 K. The bar exhibits an east-west asymmetry in the <span class="hlt">dust</span> distribution: The eastern bar is heavier than the western bar by more than a factor of 4. Integrating the <span class="hlt">dust</span> spectral energy distribution, we derived a total infrared luminosity, LTIR, of 9.8 × 1010 L⊙, leading to a <span class="hlt">dust</span>-enshrouded star formation rate of SFRTIR ≃ 16.7 M⊙ yr-1 in NGC 1365. We derived the gas mass from the measurements of the <span class="hlt">dust</span> emission, resulting in a CO-to-H2 conversion factor of XCO ≃ 1.2 × 1020 mol cm-2 (K km s-1)-1 in the central disk, including the bar. Taking into account the metallicity variation, the central gas mass concentration is only ≃20% at R < 40″ (3.6 kpc). On the other hand, the timescale on which the gas flows into the center, ≃300 Myr, is relatively short. This indicates that the current central mass in NGC 1365 is evolving fast because of the strong bar.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JAG...116...84S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JAG...116...84S"><span>Magnetic characteristics of industrial <span class="hlt">dust</span> from different sources of emission: A case study of Poland</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Szuszkiewicz, Marcin; Magiera, Tadeusz; Kapička, Aleš; Petrovský, Eduard; Grison, Hanna; Gołuchowska, Beata</p> <p>2015-05-01</p> <p><span class="hlt">Dust</span> emission and deposition in topsoil have negative effect on individual <span class="hlt">components</span> of the ecosystem. In addition to routine geochemical analyses, magnetic measurements may provide useful complementary information related to the type, concentration and grain-size distribution of the technogenic magnetic particles (TMPs) and thus the degree of contamination of the environment. The aim of this contribution is to use magnetic parameters in distinguishing <span class="hlt">dust</span> from a wide range of sources of air pollution (power industry, cement, coke, ceramic industries and biomass combustion). We measured magnetic susceptibility, hysteresis parameters and thermomagnetic curves. Our results suggest that predominant <span class="hlt">component</span> in tested samples is magnetite, only <span class="hlt">dust</span> from coking plant and the combustion of lignite contained also maghemite and/or hematite. Mixture of sizes, ranging from fine single-domain to coarse multi-domain grains, was detected. Our results indicate that industrial <span class="hlt">dusts</span> from various sources of emissions have different specific magnetic properties and magnetic measurements may provide very helpful information.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA03791&hterms=DIRT&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DDIRT','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA03791&hterms=DIRT&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DDIRT"><span><span class="hlt">Dust</span> Devil Tracks</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2002-01-01</p> <p>(Released 8 May 2002) The Science This image, centered near 50.0 S and 17.7 W displays <span class="hlt">dust</span> devil tracks on the surface. Most of the lighter portions of the image likely have a thin veneer of <span class="hlt">dust</span> settled on the surface. As a <span class="hlt">dust</span> devil passes over the surface, it acts as a vacuum and picks up the <span class="hlt">dust</span>, leaving the darker substrate exposed. In this image there is a general trend of many of the tracks running from east to west or west to east, indicating the general wind direction. There is often no general trend present in <span class="hlt">dust</span> devil tracks seen in other images. The track patterns are quite ephemeral and can completely change or even disappear over the course of a few months. <span class="hlt">Dust</span> devils are one of the mechanisms that Mars uses to constantly pump <span class="hlt">dust</span> into the ubiquitously dusty atmosphere. This atmospheric <span class="hlt">dust</span> is one of the main driving forces of the present Martian climate. The Story Vrrrrooooooooom. Think of a tornado, the cartoon Tasmanian devil, or any number of vacuum commercials that powerfully suck up swirls of <span class="hlt">dust</span> and dirt. That's pretty much what it's like on the surface of Mars a lot of the time. Whirlpools of wind called</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=309416&Lab=NERL&keyword=observational+AND+research+AND+methods&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=309416&Lab=NERL&keyword=observational+AND+research+AND+methods&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50"><span>Seasonal Contribution of Mineral <span class="hlt">Dust</span> and Otlher Major <span class="hlt">Components</span> to Particulate Matter at Two Remote Sites in Central Asia</span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p><span class="hlt">Dust</span> storms are significant contributors to ambient levels of particulate matter (PM) in many areas of the world. Central Asia, an area that is relatively understudied in this regard, is anticipated to be affected by <span class="hlt">dust</span> storms due to its proximity to several major deserts that ...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24467247','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24467247"><span>Inactivation of <span class="hlt">dust</span> mites, <span class="hlt">dust</span> mite allergen, and mold from carpet.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ong, Kee-Hean; Lewis, Roger D; Dixit, Anupma; MacDonald, Maureen; Yang, Mingan; Qian, Zhengmin</p> <p>2014-01-01</p> <p>Carpet is known to be a reservoir for biological contaminants, such as <span class="hlt">dust</span> mites, <span class="hlt">dust</span> mite allergen, and mold, if it is not kept clean. The accumulation of these contaminants in carpet might trigger allergies or asthma symptoms in both children and adults. The purpose of this study is to compare methods for removal of <span class="hlt">dust</span> mites, <span class="hlt">dust</span> mite allergens, and mold from carpet. Carpets were artificially worn to simulate 1 to 2 years of wear in a four-person household. The worn carpets were inoculated together with a common indoor mold (Cladosporium species) and house <span class="hlt">dust</span> mites and incubated for 6 weeks to allow time for <span class="hlt">dust</span> mite growth on the carpet. The carpets were randomly assigned to one of the four treatment groups. Available treatment regimens for controlling carpet contaminants were evaluated through a literature review and experimentation. Four moderately low-hazard, nondestructive methods were selected as treatments: vacuuming, steam-vapor, Neem oil (a natural tree extract), and benzalkonium chloride (a quaternary ammonium compound). Steam vapor treatment demonstrated the greatest <span class="hlt">dust</span> mite population reduction (p < 0.05) when compared to other methods. The two physical methods, steam vapor and vacuuming, have no statistically significant efficacy in inactivating <span class="hlt">dust</span> mite allergens (p = 0.084), but have higher efficacy when compared to the chemical method on <span class="hlt">dust</span> mite allergens (p = 0.002). There is no statistically significant difference in the efficacy for reducing mold in carpet (p > 0.05) for both physical and chemical methods. The steam-vapor treatment effectively killed <span class="hlt">dust</span> mites and denatured <span class="hlt">dust</span> mite allergen in the laboratory environment.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009SPIE.7334E..1GJ','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009SPIE.7334E..1GJ"><span>Directional analysis and filtering for <span class="hlt">dust</span> storm detection in NOAA-AVHRR imagery</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Janugani, S.; Jayaram, V.; Cabrera, S. D.; Rosiles, J. G.; Gill, T. E.; Rivera Rivera, N.</p> <p>2009-05-01</p> <p>In this paper, we propose spatio-spectral processing techniques for the detection of <span class="hlt">dust</span> storms and automatically finding its transport direction in 5-band NOAA-AVHRR imagery. Previous methods that use simple band math analysis have produced promising results but have drawbacks in producing consistent results when low signal to noise ratio (SNR) images are used. Moreover, in seeking to automate the <span class="hlt">dust</span> storm detection, the presence of clouds in the vicinity of the <span class="hlt">dust</span> storm creates a challenge in being able to distinguish these two types of image texture. This paper not only addresses the detection of the <span class="hlt">dust</span> storm in the imagery, it also attempts to find the transport direction and the location of the sources of the <span class="hlt">dust</span> storm. We propose a spatio-spectral processing approach with two <span class="hlt">components</span>: visualization and automation. Both approaches are based on digital image processing techniques including directional analysis and filtering. The visualization technique is intended to enhance the image in order to locate the <span class="hlt">dust</span> sources. The automation technique is proposed to detect the transport direction of the <span class="hlt">dust</span> storm. These techniques can be used in a system to provide timely warnings of <span class="hlt">dust</span> storms or hazard assessments for transportation, aviation, environmental safety, and public health.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A33F2415C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A33F2415C"><span>Estimation of the Anthropogenic <span class="hlt">Dust</span> Emission at Global Scale from 2007 to 2010</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chen, S.; Huang, J.; Jiang, N.</p> <p>2017-12-01</p> <p><span class="hlt">Dust</span> emission refers to the spatial displacement of <span class="hlt">dust</span> particles by the wind forcing, which is a key <span class="hlt">component</span> of the <span class="hlt">dust</span> circulation. It plays an important role in energy, hydrological and carbon cycle in the Earth system. However, most of the <span class="hlt">dust</span> emission schemes only considered the natural <span class="hlt">dust</span>, neglecting the anthropogenic <span class="hlt">dust</span> induced by human activities, which led to the large uncertainties in the quantitative estimations of <span class="hlt">dust</span> emission in the numerical modeling. In order to fully consider the mechanism of anthropogenic <span class="hlt">dust</span> emission, the "indrect" and "direct" anthropogenic <span class="hlt">dust</span> emission schemes were constructed and developed in the study. Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) retrievals were used to evaluate the simulations at global scales. The results showed that the schemes reasonably reproduced the spatio-temporal distributions of anthropogenic <span class="hlt">dust</span> from 2007 to 2010. The high centers of anthropogenic <span class="hlt">dust</span> emission flux appeared in India, east of China, North America and Africa with a value of 12 μg m-2 s-1. For the indirect anthropogenic <span class="hlt">dust</span> emission, it has an obvious seasonal variations, with maximum in spring and winter, while minimum in summer. Compared with the cropland, pastureland (including pastures and artificially sparse grasslands) has the higher potential anthropogenic <span class="hlt">dust</span> emission, with emission of approximately 4.7 μg m-2 s-1, accounting for 39% of the total anthropogenic <span class="hlt">dust</span> emission. Moreover, the direct anthropogenic <span class="hlt">dust</span> emission is larger than the indirect <span class="hlt">dust</span> emission at gobal scale. Especially when the increasing vegetation coverage in summer, the contribution of the direct anthropogenic <span class="hlt">dust</span> emission flux can reach up to about 75.2%. It demonstrates that the environmental problems caused by urban anthropogenic <span class="hlt">dust</span> can not be ignored.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012APS..DPPJP8062S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012APS..DPPJP8062S"><span>Development of an electrostatic <span class="hlt">dust</span> detector for tungsten <span class="hlt">dust</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Starkey, D.; Hammond, K.; Roquemore, L.; Skinner, C. H.</p> <p>2012-10-01</p> <p>Next-step fusion reactors, such as ITER, are expected to have large quantities of <span class="hlt">dust</span> that will present hazards that have yet to be encountered in current fusion devices. To manage the amount of <span class="hlt">dust</span> within the reactors a real-time <span class="hlt">dust</span> detector must be implemented to ensure that <span class="hlt">dust</span> does not reach hazardous levels. An electrostatic device that accomplishes this has already been tested on NSTX and Tore Supra [1,2]. We will present modifications of this device to improve its ruggedness to withstand the conditions that will be present in ITER. The detector consists of two tungsten wires wrapped around a macor cylinder that are biased at 100-300 V. Incident <span class="hlt">dust</span> causes a measurable transient short circuit. Initial results have demonstrated the detection of tungsten particles. We will also present a potential method of electrostatic cleaning of residual <span class="hlt">dust</span> from the detector.[4pt] [1] C. H. Skinner et al., Rev. Sci. Instrum., 81, 10E102 (2010)[0pt] [2] H. Roche et al., Phys. Scr., T145, (2011).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20020083030&hterms=extinction&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dextinction','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20020083030&hterms=extinction&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dextinction"><span>New Interstellar <span class="hlt">Dust</span> Models Consistent with Interstellar Extinction, Emission and Abundances Constraints</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zubko, V.; Dwek, E.; Arendt, R. G.; Oegerle, William (Technical Monitor)</p> <p>2001-01-01</p> <p>We present new interstellar <span class="hlt">dust</span> models that are consistent with both, the FUV to near-IR extinction and infrared (IR) emission measurements from the diffuse interstellar medium. The models are characterized by different <span class="hlt">dust</span> compositions and abundances. The problem we solve consists of determining the size distribution of the various <span class="hlt">dust</span> <span class="hlt">components</span> of the model. This problem is a typical ill-posed inversion problem which we solve using the regularization approach. We reproduce the Li Draine (2001, ApJ, 554, 778) results, however their model requires an excessive amount of interstellar silicon (48 ppM of hydrogen compared to the 36 ppM available for an ISM of solar composition) to be locked up in <span class="hlt">dust</span>. We found that <span class="hlt">dust</span> models consisting of PAHs, amorphous silicate, graphite, and composite grains made up from silicates, organic refractory, and water ice, provide an improved fit to the extinction and IR emission measurements, while still requiring a subsolar amount of silicon to be in the <span class="hlt">dust</span>. This research was supported by NASA Astrophysical Theory Program NRA 99-OSS-01.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15.6731H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.6731H"><span>Knudsen cell: Investigations about the uptake of important traces gases on ambient airborne mineral <span class="hlt">dust</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Horn, Sabrina; Herrmann, Hartmut</p> <p>2013-04-01</p> <p>Mineral <span class="hlt">dust</span> constitutes one of the largest mass fractions of natural aerosol. Its emission is estimated between 800 - 2000 Tg/a]. The <span class="hlt">dust</span> is emitted through sand and <span class="hlt">dust</span> storms in the arid regions of our planet, in particular by the great desserts such as the Sahara. The complex chemical composition of mineral <span class="hlt">dust</span> is similar to crust material, because the <span class="hlt">dust</span> is produced by soil erosion. The main <span class="hlt">components</span> of mineral <span class="hlt">dust</span> are SiO2 and Al2O3, whereas the active oxides (Fe2O3, TiO2) show some variety in content due to the <span class="hlt">dust</span> source region. Mineral <span class="hlt">dust</span> particles can be transported over several 1000 km and during its transport the surface can be changed by the uptake of water vapor and trace gases. On such modified surfaces homo- and heterogeneous reactions can occur. Trace gas uptakes play an important role in atmospheric chemistry as sinks or sources for several gaseous species. Hence, it is necessary to study these reactions. Among several experimental setups, the Knudsen cell is one of the promising tools to study reactive uptakes from the gas phase and the release of products formed by <span class="hlt">dust</span> surface-mediated reactions. The Knudsen cell, implemented by Golden et al. in 1975, is a high vacuum flow reactor operating under molecular flow conditions, i.e., gas-wall collisions are highly preferred over gas-gas collisions. Despite several Knudsen cell studies examining the reaction between different traces gases and model <span class="hlt">dust</span> surfaces constituted of not more than a few <span class="hlt">components</span>, no measurements utilizing collected ambient mineral <span class="hlt">dust</span> are done so far. For a better understanding of the chemistry on mineral <span class="hlt">dust</span> surfaces gas uptake measurements will be done with a Knudsen cell. The first measurements are done with isopropanol on TiO2. Afterwards there are studies with different substrates like, Al2O3 (α- and γ-phase), FeO2, Arizona test <span class="hlt">dust</span>, air collected mineral <span class="hlt">dust</span> from the Cap Verde islands. In the beginning SO2, NO2 and HNO3 will be used.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20000057311','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20000057311"><span>Interactive Soil <span class="hlt">Dust</span> Aerosol Model in the GISS GCM. Part 1; Sensitivity of the Soil <span class="hlt">Dust</span> Cycle to Radiative Properties of Soil <span class="hlt">Dust</span> Aerosols</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Perlwitz, Jan; Tegen, Ina; Miller, Ron L.</p> <p>2000-01-01</p> <p>The sensitivity of the soil <span class="hlt">dust</span> aerosol cycle to the radiative forcing by soil <span class="hlt">dust</span> aerosols is studied. Four experiments with the NASA/GISS atmospheric general circulation model, which includes a soil <span class="hlt">dust</span> aerosol model, are compared, all using a prescribed climatological sea surface temperature as lower boundary condition. In one experiment, <span class="hlt">dust</span> is included as dynamic tracer only (without interacting with radiation), whereas <span class="hlt">dust</span> interacts with radiation in the other simulations. Although the single scattering albedo of <span class="hlt">dust</span> particles is prescribed to be globally uniform in the experiments with radiatively active <span class="hlt">dust</span>, a different single scattering albedo is used in those experiments to estimate whether regional variations in <span class="hlt">dust</span> optical properties, corresponding to variations in mineralogical composition among different source regions, are important for the soil <span class="hlt">dust</span> cycle and the climate state. On a global scale, the radiative forcing by <span class="hlt">dust</span> generally causes a reduction in the atmospheric <span class="hlt">dust</span> load corresponding to a decreased <span class="hlt">dust</span> source flux. That is, there is a negative feedback in the climate system due to the radiative effect of <span class="hlt">dust</span>. The <span class="hlt">dust</span> source flux and its changes were analyzed in more detail for the main <span class="hlt">dust</span> source regions. This analysis shows that the reduction varies both with the season and with the single scattering albedo of the <span class="hlt">dust</span> particles. By examining the correlation with the surface wind, it was found that the <span class="hlt">dust</span> emission from the Saharan/Sahelian source region and from the Arabian peninsula, along with the sensitivity of the emission to the single scattering albedo of <span class="hlt">dust</span> particles, are related to large scale circulation patterns, in particular to the trade winds during Northern Hemisphere winter and to the Indian monsoon circulation during summer. In the other regions, such relations to the large scale circulation were not found. There, the dependence of <span class="hlt">dust</span> deflation to radiative forcing by <span class="hlt">dust</span> particles is probably</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19970026865','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19970026865"><span>Kuiper Belt <span class="hlt">Dust</span> Grains as a Source of Interplanetary <span class="hlt">Dust</span> Particles</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Liou, Jer-Chyi; Zook, Herbert A.; Dermott, Stanley F.</p> <p>1996-01-01</p> <p>The recent discovery of the so-called Kuiper belt objects has prompted the idea that these objects produce <span class="hlt">dust</span> grains that may contribute significantly to the interplanetary <span class="hlt">dust</span> population. In this paper, the orbital evolution of <span class="hlt">dust</span> grains, of diameters 1 to 9 microns, that originate in the region of the Kuiper belt is studied by means of direct numerical integration. Gravitational forces of the Sun and planets, solar radiation pressure, as well as Poynting-Robertson drag and solar wind drag are included. The interactions between charged <span class="hlt">dust</span> grains and solar magnetic field are not considered in the model. Because of the effects of drag forces, small <span class="hlt">dust</span> grains will spiral toward the Sun once they are released from their large parent bodies. This motion leads <span class="hlt">dust</span> grains to pass by planets as well as encounter numerous mean motion resonances associated with planets. Our results show that about 80% of the Kuiper belt grains are ejected from the Solar System by the giant planets, while the remaining 20% of the grains evolve all the way to the Sun. Surprisingly, the latter <span class="hlt">dust</span> grains have small orbital eccentricities and inclinations when they cross the orbit of the Earth. This makes them behave more like asteroidal than cometary-type <span class="hlt">dust</span> particles. This also enhances their chances of being captured by the Earth and makes them a possible source of the collected interplanetary <span class="hlt">dust</span> particles; in particular, they represent a possible source that brings primitive/organic materials from the outer Solar System to the Earth. When collisions with interstellar <span class="hlt">dust</span> grains are considered, however, Kuiper belt <span class="hlt">dust</span> grains around 9 microns appear likely to be collisionally shattered before they can evolve toward the inner part of the Solar System. The collision destruction can be applied to Kuiper belt grains up to about 50 microns. Therefore, Kuiper belt <span class="hlt">dust</span> grains within this range may not be a significant part of the interplanetary <span class="hlt">dust</span> complex in the inner Solar</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/1249736-warm-spring-reduced-carbon-cycle-impact-us-summer-drought','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1249736-warm-spring-reduced-carbon-cycle-impact-us-summer-drought"><span><span class="hlt">Warm</span> spring reduced carbon cycle impact of the 2012 US summer drought</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Wolf, Sebastian; Keenan, Trevor F.; Fisher, Joshua B.</p> <p></p> <p>The global terrestrial carbon sink offsets one-third of the world's fossil fuel emissions, but the strength of this sink is highly sensitive to large-scale extreme events. In 2012, the contiguous United States experienced exceptionally <span class="hlt">warm</span> temperatures and the most severe drought since the <span class="hlt">Dust</span> Bowl era of the 1930s, resulting in substantial economic damage. It is crucial to understand the dynamics of such events because warmer temperatures and a higher prevalence of drought are projected in a changing climate. Here in this paper, we combine an extensive network of direct ecosystem flux measurements with satellite remote sensing and atmospheric inversemore » modeling to quantify the impact of the warmer spring and summer drought on biosphereatmosphere carbon and water exchange in 2012. We consistently find that earlier vegetation activity increased spring carbon uptake and compensated for the reduced uptake during the summer drought, which mitigated the impact on net annual carbon uptake. The early phenological development in the Eastern Temperate Forests played a major role for the continental-scale carbon balance in 2012. The <span class="hlt">warm</span> spring also depleted soil water resources earlier, and thus exacerbated water limitations during summer. Our results show that the detrimental effects of severe summer drought on ecosystem carbon storage can be mitigated by <span class="hlt">warming</span>-induced increases in spring carbon uptake. However, the results also suggest that the positive carbon cycle effect of <span class="hlt">warm</span> spring enhances water limitations and can increase summer heating through biosphere-atmosphere feedbacks.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27114518','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27114518"><span><span class="hlt">Warm</span> spring reduced carbon cycle impact of the 2012 US summer drought.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wolf, Sebastian; Keenan, Trevor F; Fisher, Joshua B; Baldocchi, Dennis D; Desai, Ankur R; Richardson, Andrew D; Scott, Russell L; Law, Beverly E; Litvak, Marcy E; Brunsell, Nathaniel A; Peters, Wouter; van der Laan-Luijkx, Ingrid T</p> <p>2016-05-24</p> <p>The global terrestrial carbon sink offsets one-third of the world's fossil fuel emissions, but the strength of this sink is highly sensitive to large-scale extreme events. In 2012, the contiguous United States experienced exceptionally <span class="hlt">warm</span> temperatures and the most severe drought since the <span class="hlt">Dust</span> Bowl era of the 1930s, resulting in substantial economic damage. It is crucial to understand the dynamics of such events because warmer temperatures and a higher prevalence of drought are projected in a changing climate. Here, we combine an extensive network of direct ecosystem flux measurements with satellite remote sensing and atmospheric inverse modeling to quantify the impact of the warmer spring and summer drought on biosphere-atmosphere carbon and water exchange in 2012. We consistently find that earlier vegetation activity increased spring carbon uptake and compensated for the reduced uptake during the summer drought, which mitigated the impact on net annual carbon uptake. The early phenological development in the Eastern Temperate Forests played a major role for the continental-scale carbon balance in 2012. The <span class="hlt">warm</span> spring also depleted soil water resources earlier, and thus exacerbated water limitations during summer. Our results show that the detrimental effects of severe summer drought on ecosystem carbon storage can be mitigated by <span class="hlt">warming</span>-induced increases in spring carbon uptake. However, the results also suggest that the positive carbon cycle effect of <span class="hlt">warm</span> spring enhances water limitations and can increase summer heating through biosphere-atmosphere feedbacks.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4889356','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4889356"><span><span class="hlt">Warm</span> spring reduced carbon cycle impact of the 2012 US summer drought</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Keenan, Trevor F.; Fisher, Joshua B.; Richardson, Andrew D.; Scott, Russell L.; Law, Beverly E.; Litvak, Marcy E.; Brunsell, Nathaniel A.; Peters, Wouter</p> <p>2016-01-01</p> <p>The global terrestrial carbon sink offsets one-third of the world’s fossil fuel emissions, but the strength of this sink is highly sensitive to large-scale extreme events. In 2012, the contiguous United States experienced exceptionally <span class="hlt">warm</span> temperatures and the most severe drought since the <span class="hlt">Dust</span> Bowl era of the 1930s, resulting in substantial economic damage. It is crucial to understand the dynamics of such events because warmer temperatures and a higher prevalence of drought are projected in a changing climate. Here, we combine an extensive network of direct ecosystem flux measurements with satellite remote sensing and atmospheric inverse modeling to quantify the impact of the warmer spring and summer drought on biosphere-atmosphere carbon and water exchange in 2012. We consistently find that earlier vegetation activity increased spring carbon uptake and compensated for the reduced uptake during the summer drought, which mitigated the impact on net annual carbon uptake. The early phenological development in the Eastern Temperate Forests played a major role for the continental-scale carbon balance in 2012. The <span class="hlt">warm</span> spring also depleted soil water resources earlier, and thus exacerbated water limitations during summer. Our results show that the detrimental effects of severe summer drought on ecosystem carbon storage can be mitigated by <span class="hlt">warming</span>-induced increases in spring carbon uptake. However, the results also suggest that the positive carbon cycle effect of <span class="hlt">warm</span> spring enhances water limitations and can increase summer heating through biosphere–atmosphere feedbacks. PMID:27114518</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_22 --> <div id="page_23" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="441"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1249736-warm-spring-reduced-carbon-cycle-impact-us-summer-drought','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1249736-warm-spring-reduced-carbon-cycle-impact-us-summer-drought"><span><span class="hlt">Warm</span> spring reduced carbon cycle impact of the 2012 US summer drought</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Wolf, Sebastian; Keenan, Trevor F.; Fisher, Joshua B.; ...</p> <p>2016-04-25</p> <p>The global terrestrial carbon sink offsets one-third of the world's fossil fuel emissions, but the strength of this sink is highly sensitive to large-scale extreme events. In 2012, the contiguous United States experienced exceptionally <span class="hlt">warm</span> temperatures and the most severe drought since the <span class="hlt">Dust</span> Bowl era of the 1930s, resulting in substantial economic damage. It is crucial to understand the dynamics of such events because warmer temperatures and a higher prevalence of drought are projected in a changing climate. Here in this paper, we combine an extensive network of direct ecosystem flux measurements with satellite remote sensing and atmospheric inversemore » modeling to quantify the impact of the warmer spring and summer drought on biosphereatmosphere carbon and water exchange in 2012. We consistently find that earlier vegetation activity increased spring carbon uptake and compensated for the reduced uptake during the summer drought, which mitigated the impact on net annual carbon uptake. The early phenological development in the Eastern Temperate Forests played a major role for the continental-scale carbon balance in 2012. The <span class="hlt">warm</span> spring also depleted soil water resources earlier, and thus exacerbated water limitations during summer. Our results show that the detrimental effects of severe summer drought on ecosystem carbon storage can be mitigated by <span class="hlt">warming</span>-induced increases in spring carbon uptake. However, the results also suggest that the positive carbon cycle effect of <span class="hlt">warm</span> spring enhances water limitations and can increase summer heating through biosphere-atmosphere feedbacks.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016MNRAS.462S.304M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016MNRAS.462S.304M"><span>Fractal cometary <span class="hlt">dust</span> - a window into the early Solar system</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mannel, T.; Bentley, M. S.; Schmied, R.; Jeszenszky, H.; Levasseur-Regourd, A. C.; Romstedt, J.; Torkar, K.</p> <p>2016-11-01</p> <p>The properties of <span class="hlt">dust</span> in the protoplanetary disc are key to understanding the formation of planets in our Solar system. Many models of <span class="hlt">dust</span> growth predict the development of fractal structures which evolve into non-fractal, porous <span class="hlt">dust</span> pebbles representing the main <span class="hlt">component</span> for planetesimal accretion. In order to understand comets and their origins, the Rosetta orbiter followed comet 67P/Churyumov-Gerasimenko for over two years and carried a dedicated instrument suite for <span class="hlt">dust</span> analysis. One of these instruments, the MIDAS (Micro-Imaging <span class="hlt">Dust</span> Analysis System) atomic force microscope, recorded the 3D topography of micro- to nanometre-sized <span class="hlt">dust</span>. All particles analysed to date have been found to be hierarchical agglomerates. Most show compact packing; however, one is extremely porous. This paper contains a structural description of a compact aggregate and the outstanding porous one. Both particles are tens of micrometres in size and show rather narrow subunit size distributions with noticeably similar mean values of 1.48^{+0.13}_{-0.59} μm for the porous particle and 1.36^{+0.15}_{-0.59} μm for the compact. The porous particle allows a fractal analysis, where a density-density correlation function yields a fractal dimension of Df = 1.70 ± 0.1. GIADA, another <span class="hlt">dust</span> analysis instrument on board Rosetta, confirms the existence of a <span class="hlt">dust</span> population with a similar fractal dimension. The fractal particles are interpreted as pristine agglomerates built in the protoplanetary disc and preserved in the comet. The similar subunits of both fractal and compact <span class="hlt">dust</span> indicate a common origin which is, given the properties of the fractal, dominated by slow agglomeration of equally sized aggregates known as cluster-cluster agglomeration.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19760041714&hterms=refraction+index&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Drefraction%2Bindex','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19760041714&hterms=refraction+index&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Drefraction%2Bindex"><span>Complex refractive index of Martian <span class="hlt">dust</span> - Mariner 9 ultraviolet observations</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Pang, K.; Ajello, J. M.; Hord, C. W.; Egan, W. G.</p> <p>1976-01-01</p> <p>Mariner 9 ultraviolet spectrometer observations of the 1971 <span class="hlt">dust</span> clouds obscuring the surface of Mars have been analyzed by matching the observed <span class="hlt">dust</span> phase function with Mie scattering calculations for size distributions of homogeneous and isotropic material. Preliminary results indicate an effective particle radius of not less than 0.2. The real <span class="hlt">component</span> of the index of refraction is not less than 1.8 at both 268 and 305 nm; corresponding values for the imagery <span class="hlt">component</span> are 0.02 and 0.01. These values are consistent with those found by Mead (1970) for the visible and near-visible wavelengths. The refractive index and the absorption coefficient increase rapidly with decreasing wavelength in going from the visible to the ultraviolet, indicating the presence of an ultraviolet absorption band which may shield organisms from ultraviolet irradiation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009GMS...187...37R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009GMS...187...37R"><span>Global <span class="hlt">dust</span> cycle</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ridgwell, Andy</p> <p></p> <p><span class="hlt">Dust</span>, micron to submicron particles and mostly comprising soil mineral fragments, affects a multitude of climatic and biogeochemical processes during its journey from its sources on land to sinks on land and in the ocean. Suspended in the atmosphere, the presence of <span class="hlt">dust</span> can alter both shortwave and longwave radiation balances, enhance cloud nucleation, and affect photochemical reaction rates. Deposited to the land surface, <span class="hlt">dust</span> has beneficial impacts on soil quality but detrimental implications for human health. At the interface of surface ocean and lower atmosphere, <span class="hlt">dust</span> deposited to seawater supplies plankton with the essential micronutrient iron and hence provides an important control on marine ecosystems. This chapter reviews these various roles of <span class="hlt">dust</span> in the Earth system; summarizes the factors controlling the production, transport, and deposition of <span class="hlt">dust</span>; and, because the causes and consequences of <span class="hlt">dust</span> are interlinked via climate and atmospheric CO2, discusses the potential importance of dusty feedback in past and future climate change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28085472','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28085472"><span>Dynamic properties of the energy loss of multi-MeV charged particles traveling in two-<span class="hlt">component</span> <span class="hlt">warm</span> dense plasmas.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Fu, Zhen-Guo; Wang, Zhigang; Li, Meng-Lei; Li, Da-Fang; Kang, Wei; Zhang, Ping</p> <p>2016-12-01</p> <p>The energy loss of multi-MeV charged particles moving in two-<span class="hlt">component</span> <span class="hlt">warm</span> dense plasmas (WDPs) is studied theoretically beyond the random-phase approximation. The short-range correlations between particles are taken into account via dynamic local field corrections (DLFC) in a Mermin dielectric function for two-<span class="hlt">component</span> plasmas. The mean ionization states are obtained by employing the detailed configuration accounting model. The Yukawa-type effective potential is used to derive the DLFC. Numerically, the DLFC are obtained via self-consistent iterative operations. We find that the DLFC are significant around the maximum of the stopping power. Furthermore, by using the two-<span class="hlt">component</span> extended Mermin dielectric function model including the DLFC, the energy loss of a proton with an initial energy of ∼15 MeV passing through a WDP of beryllium with an electronic density around the solid value n_{e}≈3×10^{23}cm^{-3} and with temperature around ∼40 eV is estimated numerically. The numerical result is reasonably consistent with the experimental observations [A. B. Zylsta et al., Phys. Rev. Lett. 111, 215002 (2013)PRLTAO0031-900710.1103/PhysRevLett.111.215002]. Our results show that the partial ionization and the dynamic properties should be of importance for the stopping of charged particles moving in the WDP.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27529268','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27529268"><span>Heavy Metal Distribution in Street <span class="hlt">Dust</span> from Traditional Markets and the Human Health Implications.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kim, Jin Ah; Park, Jin Hee; Hwang, Won Ju</p> <p>2016-08-13</p> <p>Street <span class="hlt">dust</span> is a hazard for workers in traditional markets. Exposure time is longer than for other people, making them vulnerable to heavy metals in street <span class="hlt">dust</span>. This study investigated heavy metal concentrations in street <span class="hlt">dust</span> samples collected from different types of markets. It compared the results with heavy metal concentrations in heavy traffic and rural areas. Street <span class="hlt">dust</span> was significantly enriched with most heavy metals in a heavy traffic area while street <span class="hlt">dust</span> from a fish market was contaminated with cupper (Cu), lead (Pb) and zinc (Zn). Street <span class="hlt">dust</span> from medicinal herb and fruit markets, and rural areas were not contaminated. Principal <span class="hlt">component</span> and cluster analyses indicated heavy metals in heavy traffic road and fish market <span class="hlt">dust</span> had different sources. Relatively high heavy metal concentration in street <span class="hlt">dust</span> from the fish market may negatively affect worker's mental health, as depression levels were higher compared with workers in other markets. Therefore, intensive investigation of the relationship between heavy metal concentrations in street <span class="hlt">dust</span> and worker's health in traditional marketplaces should be conducted to elucidate the effect of heavy metals on psychological health in humans.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4997506','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4997506"><span>Heavy Metal Distribution in Street <span class="hlt">Dust</span> from Traditional Markets and the Human Health Implications</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Kim, Jin Ah; Park, Jin Hee; Hwang, Won Ju</p> <p>2016-01-01</p> <p>Street <span class="hlt">dust</span> is a hazard for workers in traditional markets. Exposure time is longer than for other people, making them vulnerable to heavy metals in street <span class="hlt">dust</span>. This study investigated heavy metal concentrations in street <span class="hlt">dust</span> samples collected from different types of markets. It compared the results with heavy metal concentrations in heavy traffic and rural areas. Street <span class="hlt">dust</span> was significantly enriched with most heavy metals in a heavy traffic area while street <span class="hlt">dust</span> from a fish market was contaminated with cupper (Cu), lead (Pb) and zinc (Zn). Street <span class="hlt">dust</span> from medicinal herb and fruit markets, and rural areas were not contaminated. Principal <span class="hlt">component</span> and cluster analyses indicated heavy metals in heavy traffic road and fish market <span class="hlt">dust</span> had different sources. Relatively high heavy metal concentration in street <span class="hlt">dust</span> from the fish market may negatively affect worker’s mental health, as depression levels were higher compared with workers in other markets. Therefore, intensive investigation of the relationship between heavy metal concentrations in street <span class="hlt">dust</span> and worker’s health in traditional marketplaces should be conducted to elucidate the effect of heavy metals on psychological health in humans. PMID:27529268</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25837247','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25837247"><span>Does Vibration <span class="hlt">Warm</span>-up Enhance Kinetic and Temporal Sprint Parameters?</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cochrane, D J; Cronin, M J; Fink, P W</p> <p>2015-08-01</p> <p>The aim of this study was to investigate the efficacy of vibration <span class="hlt">warm</span>-up to enhance sprint performance. 12 males involved in representative team sports performed 4 <span class="hlt">warm</span>-up conditions in a randomised order performed at least 24 h apart; VbX <span class="hlt">warm</span>-up (VbX-WU); Neural activation <span class="hlt">warm</span>-up (Neu-WU); Dynamic <span class="hlt">warm</span>-up (Dyn-WU) and Control (No VbX). Participants completed 5 m sprint at 30 s, 2:30 min and 5 min post <span class="hlt">warm</span>-up where sprint time, kinetics, and temporal <span class="hlt">components</span> were recorded. There was no significant (p>0.05) main effect or interaction effect between the split sprint times of 1 m, 2.5 m, and 5 m. There was a condition effect where vertical mean force was significantly higher (p<0.05) in Dyn-WU and Control compared to Neu-WU. No other significant (p>0.05) main and interaction effects in sprint kinetic and temporal parameters existed. Overall, all 4 <span class="hlt">warm</span>-up conditions produced comparable results for sprint performance, and there was no detrimental effect on short-duration sprint performance using VbX-WU. Therefore, VbX could be useful for adding variety to the training <span class="hlt">warm</span>-up or be included into the main <span class="hlt">warm</span>-up routine as a supplementary modality. © Georg Thieme Verlag KG Stuttgart · New York.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000DPS....32.5404C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000DPS....32.5404C"><span>MGS TES Measurements of <span class="hlt">Dust</span> and Ice Aerosol Behaviors</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Clancy, R. T.; Wolff, M. J.; Christensen, P. R.</p> <p>2000-10-01</p> <p>The Thermal Emission Spectrometer (TES, Christensen et al., Science, v279, 1692-1697, 1998) on board the Mars Global Surveyor obtains simultaneous solar band and thermal IR spectral emission-phase-function (EPF) observations with global spatial coverage and continuous seasonal sampling. These measurements allow the first comprehensive study of the coupled visible scattering and thermal IR absorption properties of Mars atmospheric aerosols, a fundamental requirement towards defining opacities, particle sizes, and particle shapes for separable <span class="hlt">dust</span> and water ice aerosol <span class="hlt">components</span>. Furthermore, TES limb sounding at solar band and IR wavelengths may be analyzed in the context of these EPF column determinations to constrain the distinctive vertical profile behaviors of <span class="hlt">dust</span> and ice clouds. We present initial radiative transfer analyses of TES visible and IR EPFs, which indicate surprisingly complex <span class="hlt">dust</span> and ice aerosol behaviors over all latitudes and seasons. Distinctive backscattering peaks of variable intensity are observed for several types of water ice clouds, along with evidence for ice-coated <span class="hlt">dust</span> aerosols. We will present a broad spatial and temporal sampling of solar band and spectral IR results for Mars atmospheric ice and <span class="hlt">dust</span> aerosols observed over the 1998-2000 period. This research is supported by the MGS Participating Scientist and MED Science Data Analysis programs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA21501.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA21501.html"><span><span class="hlt">Dust</span> Devil Tracks</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2017-03-06</p> <p>This image captured by NASA 2001 Mars Odyssey spacecraft shows <span class="hlt">dust</span> devil tracks in Aonia Terra. As the <span class="hlt">dust</span> devil moves along the surface it scours the <span class="hlt">dust</span> and fine materials away, revealing the darker rocky surface below the <span class="hlt">dust</span>. Orbit Number: 66962 Latitude: -68.8221 Longitude: 241.346 Instrument: VIS Captured: 2017-01-17 13:13 http://photojournal.jpl.nasa.gov/catalog/PIA21501</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20050165559','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20050165559"><span>The Nature and Origin of Interplanetary <span class="hlt">Dust</span>: High Temperature <span class="hlt">Components</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Keller, L. P.; Messenger, S.</p> <p>2004-01-01</p> <p>The specific parent bodies of individual interplanetary <span class="hlt">dust</span> particles (IDPs) are un-known, but the anhydrous chondritic-porous (CP) sub-set has been linked directly to cometary sources [1]. The CP IDPs escaped the thermal processing and water-rock interactions that have severely modified or destroyed the original mineralogy of primitive meteorites. Their origin in the outer regions of the solar system suggests they should retain primitive chemical and physical characteristics from the earliest stages of solar system formation (including abundant presolar materials). Indeed, CP IDPs are the most primitive extraterrestrial materials available for laboratory studies based on their unequilibrated mineralogy [2], high concentrations of carbon, nitrogen and volatile trace elements relative to CI chondrites [3, 4, 5], presolar hydrogen and nitrogen isotopic signatures [6, 7] and abundant presolar silicates [8].</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20160005317','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20160005317"><span>Electrodynamic <span class="hlt">Dust</span> Shield for Space Applications</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mackey, Paul J.; Johansen, Michael R.; Olsen, Robert C.; Raines, Matthew G.; Phillips, James R., III; Cox, Rachel E.; Hogue, Michael D.; Calle, Carlos I.; Pollard, Jacob R. S.</p> <p>2016-01-01</p> <p>The International Space Exploration Coordination Group (ISECG) has chosen <span class="hlt">dust</span> mitigation technology as a Global Exploration Roadmap (GER) critical technology need in order to reduce life cycle cost and risk, and increase the probability of mission success. NASA has also included Particulate Contamination Prevention and Mitigation as a cross-cutting technology to be developed for contamination prevention, cleaning and protection. This technology has been highlighted due to the detrimental effect of <span class="hlt">dust</span> on both human and robotic missions. During manned Apollo missions, <span class="hlt">dust</span> caused issues with both equipment and crew. Contamination of equipment caused many issues including incorrect instrument readings and increased temperatures due to masking of thermal radiators. The astronauts were directly affected by <span class="hlt">dust</span> that covered space suits, obscured face shields and later propagated to the cabin and into the crew's eyes and lungs. Robotic missions on Mars were affected when solar panels were obscured by <span class="hlt">dust</span> thereby reducing the effectiveness of the solar panels. The Electrostatics and Surface Physics Lab in Swamp Works at the Kennedy Space Center has been developing an Electrodynamic <span class="hlt">Dust</span> Shield (EDS) to remove <span class="hlt">dust</span> from multiple surfaces, including glass shields and thermal radiators. This technology has been tested in lab environments and has evolved over several years. Tests of the technology include reduced gravity flights (6g) in which Apollo Lunar <span class="hlt">dust</span> samples were successfully removed from glass shields while under vacuum (1 millipascal). Further development of the technology is underway to reduce the size of the EDS as well as to perform material and <span class="hlt">component</span> testing outside of the International Space Station (ISS) on the Materials on International Space Station Experiment X (MISSE-X). This experiment is designed to verify that the EDS can withstand the harsh environment of space and will look to closely replicate the solar environment experienced on the moon</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=327541','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=327541"><span>Combustibility determination for cotton gin <span class="hlt">dust</span> and almond huller <span class="hlt">dust</span></span></a></p> <p><a target="_blank" href="https://www.ars.usda.gov/research/publications/find-a-publication/">USDA-ARS?s Scientific Manuscript database</a></p> <p></p> <p></p> <p>It has been documented that some <span class="hlt">dusts</span> generated while processing agricultural products, such as grain and sugar (OSHA, 2009), can constitute combustible <span class="hlt">dust</span> hazards. After a catastrophic <span class="hlt">dust</span> explosion in a sugar refinery in 2008, OSHA initiated action to develop a mandatory standard to comprehen...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA04698&hterms=fine+dust&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dfine%2Bdust','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA04698&hterms=fine+dust&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dfine%2Bdust"><span>Summertime <span class="hlt">Dust</span> Devil</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2003-01-01</p> <p>MGS MOC Release No. MOC2-464, 26 August 2003<p/><span class="hlt">Dust</span> devils are spinning, columnar vortices of air that move across a landscape, picking up <span class="hlt">dust</span> as they go. They are common occurrences during summer on Mars. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image, acquired during northern summer, shows a <span class="hlt">dust</span> devil in the Phlegra region of Mars near 32.0oN, 182.1oW. Sunlight illuminates the scene from the lower left; the <span class="hlt">dust</span> devil is casting a columnar shadow toward the upper right. Some <span class="hlt">dust</span> devils on Mars make streaks as they disrupt the fine coating of <span class="hlt">dust</span> on the surface--but others do not make streaks. This one did not make a streak. The view shown here is 3 km (1.9 mi) wide.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1814601H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1814601H"><span>Intense <span class="hlt">dust</span> episodes in the Mediterranean and possible effects on atmospheric lapse rates</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hatzianastassiou, Nikos; Gkikas, Antonis; Papadimas, Christos D.; Gavrouzou, Maria</p> <p>2016-04-01</p> <p><span class="hlt">Dust</span> aerosols are major contributor to the atmospheric particulate matter, having significant effects on climate and weather patterns as well as on human health, not to mention others like agriculture or ocean chlorophyll. Moreover, these effects are maximized under conditions of massive <span class="hlt">dust</span> concentration in the atmosphere, namely <span class="hlt">dust</span> episodes or events. Such events are caused by uplifting and transport of <span class="hlt">dust</span> from arid and semi-arid areas under favorable synoptic conditions. The Mediterranean basin, nearby to the greatest world deserts of North Africa and Middle East, frequently undergoes <span class="hlt">dust</span> episodes. During such Mediterranean episodes, the number and mass concentration of <span class="hlt">dust</span> is high, due to the proximity of its source areas. The <span class="hlt">dust</span> episodes, through the direct interaction of <span class="hlt">dust</span> primarily withthe shortwave but also with longwave radiation can lead to strong local <span class="hlt">warming</span> in the atmosphere, possibly causing temperature inversion during daytime. The existence of such temperature inversions, associated with intense <span class="hlt">dust</span> episodes in the Mediterranean, is the focus in this study. The methodology followed to achieve the scientific goal of the study consists in the use of a synergy of different data. This synergy enables: (i) the determination of intense <span class="hlt">dust</span> episodes over the Mediterranean, (ii) the investigation and specification of temperature lapse rates and inversions during the days of <span class="hlt">dust</span> episodes and (iii) the identification of vertical distribution of aerosols in the atmosphere over specific locations during the days of the episodes. These objectives are achieved through the use of data from: (i) the AERosol Robotic NETwork (AERONET) network, (ii) the Upper Air Observations (radiosondes) database of the University of Wyoming (UoW) and (iii) the European Aerosol Research Lidar Network (EARLINET) database. The study period spans the years from 2000 to 2013, constrained by the data availability of the databases. A key element of the methodology is the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20070023437','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20070023437"><span>Lunar <span class="hlt">Dust</span> on Heat Rejection System Surfaces: Problems and Prospects</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gaier, James R.; Jaworske, Donald A.</p> <p>2007-01-01</p> <p>Heat rejection from power systems will be necessary for human and robotic activity on the lunar surface. Functional operation of such heat rejection systems is at risk of degradation as a consequence of <span class="hlt">dust</span> accumulation. The Apollo astronauts encountered marked degradation of performance in heat rejection systems for the lunar roving vehicle, science packages, and other <span class="hlt">components</span>. Although ground testing of <span class="hlt">dust</span> mitigation concepts in support of the Apollo mission identified mitigation tools, the brush concept adopted by the Apollo astronauts proved essentially ineffective. A better understanding of the issues associated with the impact of lunar <span class="hlt">dust</span> on the functional performance of heat rejection systems and its removal is needed as planning gets underway for human and robotic missions to the Moon. Renewed emphasis must also be placed on ground testing of pristine and <span class="hlt">dust</span>-covered heat rejection system surfaces to quantify degradation and address mitigation concepts. This paper presents a review of the degradation in performance of heat rejection systems encountered on the lunar surface to-date, and will discuss current activities underway to evaluate the durability of candidate heat rejection system surfaces and current <span class="hlt">dust</span> mitigation concepts.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=332610','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=332610"><span>A numerical study on <span class="hlt">dust</span> devils with implications to global <span class="hlt">dust</span> budget estimates</span></a></p> <p><a target="_blank" href="https://www.ars.usda.gov/research/publications/find-a-publication/">USDA-ARS?s Scientific Manuscript database</a></p> <p></p> <p></p> <p>The estimates of the contribution of <span class="hlt">dust</span> devils (DDs) to the global <span class="hlt">dust</span> budget have large uncertainties because the <span class="hlt">dust</span> emission mechanisms in DDs are not yet well understood. In this study, a large-eddy simulation model coupled with a <span class="hlt">dust</span> scheme is used to investigate DD <span class="hlt">dust</span> entrainment. DDs a...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ApJ...857...94Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ApJ...857...94Z"><span>Iron and Silicate <span class="hlt">Dust</span> Growth in the Galactic Interstellar Medium: Clues from Element Depletions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhukovska, Svitlana; Henning, Thomas; Dobbs, Clare</p> <p>2018-04-01</p> <p>The interstellar abundances of refractory elements indicate a substantial depletion from the gas phase, which increases with gas density. Our recent model of <span class="hlt">dust</span> evolution, based on hydrodynamic simulations of the life cycle of giant molecular clouds (GMCs), proves that the observed trend for [Sigas/H] is driven by a combination of <span class="hlt">dust</span> growth by accretion in the cold diffuse interstellar medium (ISM) and efficient destruction by supernova (SN) shocks. With an analytic model of <span class="hlt">dust</span> evolution, we demonstrate that even with optimistic assumptions for the <span class="hlt">dust</span> input from stars and without destruction of grains by SNe it is impossible to match the observed [Sigas/H]–n H relation without growth in the ISM. We extend the framework developed in our previous work for silicates to include the evolution of iron grains and address a long-standing conundrum: “Where is the interstellar iron?” Much higher depletion of Fe in the <span class="hlt">warm</span> neutral medium compared to Si is reproduced by the models, in which a large fraction of interstellar iron (70%) is locked as inclusions in silicate grains, where it is protected from efficient sputtering by SN shocks. The slope of the observed [Fegas/H]–n H relation is reproduced if the remaining depleted iron resides in a population of metallic iron nanoparticles with sizes in the range of 1–10 nm. Enhanced collision rates due to the Coulomb focusing are important for both silicate and iron <span class="hlt">dust</span> models to match the slopes of the observed depletion–density relations and the magnitudes of depletion at high gas density.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110014327','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110014327"><span><span class="hlt">Dust</span> Destruction in the ISM: A Re-Evaluation of <span class="hlt">Dust</span> Lifetimes</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Jones, A. P.; Nuth, J. A., III</p> <p>2011-01-01</p> <p>There is a long-standing conundrum in interstellar <span class="hlt">dust</span> studies relating to the discrepancy between the time-scales for <span class="hlt">dust</span> formation from evolved stars and the apparently more rapid destruction in supernova-generated shock waves. Aims. We re-examine some of the key issues relating to <span class="hlt">dust</span> evolution and processing in the interstellar medium. Methods. We use recent and new constraints from observations, experiments, modelling and theory to re-evaluate <span class="hlt">dust</span> formation in the interstellar medium (ISM). Results. We find that the discrepancy between the <span class="hlt">dust</span> formation and destruction time-scales may not be as significant as has previously been assumed because of the very large uncertainties involved. Conclusions. The derived silicate <span class="hlt">dust</span> lifetime could be compatible with its injection time-scale, given the inherent uncertainties in the <span class="hlt">dust</span> lifetime calculation. The apparent need to re-form significant quantities of silicate <span class="hlt">dust</span> in the tenuous interstellar medium may therefore not be a strong requirement. Carbonaceous matter, on the other hand, appears to be rapidly recycled in the ISM and, in contrast to silicates, there are viable mechanisms for its re-formation in the ISM.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015Icar..254..262H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015Icar..254..262H"><span>Evolution of the <span class="hlt">dust</span> and water ice plume <span class="hlt">components</span> as observed by the LCROSS visible camera and UV-visible spectrometer</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Heldmann, Jennifer L.; Lamb, Justin; Asturias, Daniel; Colaprete, Anthony; Goldstein, David B.; Trafton, Laurence M.; Varghese, Philip L.</p> <p>2015-07-01</p> <p>The LCROSS (Lunar Crater Observation and Sensing Satellite) impacted the Cabeus crater near the lunar South Pole on 9 October 2009 and created an impact plume that was observed by the LCROSS Shepherding Spacecraft. Here we analyze data from the ultraviolet-visible spectrometer and visible context camera aboard the spacecraft. We use these data to constrain a numerical model to understand the physical evolution of the resultant plume. The UV-visible light curve peaks in brightness 18 s after impact and then decreases in radiance but never returns to the pre-impact radiance value for the ∼4 min of observation by the Shepherding Spacecraft. The blue:red spectral ratio increases in the first 10 s, decreases over the following 50 s, remains constant for approximately 150 s, and then begins to increase again ∼180 s after impact. Constraining the modeling results with spacecraft observations, we conclude that lofted <span class="hlt">dust</span> grains remained suspended above the lunar surface for the entire 250 s of observation after impact. The impact plume was composed of both a high angle spike and low angle plume <span class="hlt">component</span>. Numerical modeling is used to evaluate the relative effects of various plume parameters to further constrain the plume properties when compared with the observational data. <span class="hlt">Dust</span> particle sizes lofted above the lunar surface were micron to sub-micron in size. Water ice particles were also contained within the ejecta cloud and simultaneously photo-dissociated and sublimated after reaching sunlight.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_23 --> <div id="page_24" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="461"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.A23C0316G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.A23C0316G"><span>Direct Radiative Effect of Intense <span class="hlt">Dust</span> Outbreaks in the Mediterranean</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gkikas, A.; Obiso, V.; Basart, S.; Jorba, O.; Pérez García-Pando, C.; Hatzianastassiou, N.; Gassó, S.; Baldasano, J. M.</p> <p>2015-12-01</p> <p>The broader Mediterranean basin is affected by intense desert <span class="hlt">dust</span> outbreaks in spring. In the present study, we make use of satellite observations and modelling to investigate <span class="hlt">dust</span> radiative impacts during three consecutive <span class="hlt">dust</span> outbreaks occurred over the Mediterranean in the period 9/4-15/4/2008. The direct radiative effect (DRE) is estimated by using two simulations run with the NMMB/BSC-<span class="hlt">Dust</span> model, where the interaction between <span class="hlt">dust</span> aerosols and radiation is activated and deactivated, respectively. The simulation domain covers the North Africa, the Middle East and Europe at 0.25ºx0.25° and 40σ-layers. The first outbreak took place over the central and eastern Mediterranean on the 9th reaching aerosol optical depths (AODs) close to 1. The second one, with AODs up to 2, lasted from 10th to 14th affecting mainly the central Mediterranean. The third one, with AODs up to 5, affected the Iberian Peninsula on the 15th. DREs are computed for the outgoing radiation at the top of the atmosphere (TOA), the absorbed radiation into the atmosphere (ATMAB), for the downwelling (SURF) and the absorbed (NETSURF) radiation at surface, for the shortwave (SW), longwave (LW) and NET (SW+LW) radiation. According to our results, it is evident that DREs' spatial patterns are driven by those of AOD. Negative (cooling) instantaneous DRETOA, DRESURF and DRENETSURF values up to -500W/m2, -700W/m2 and -600W/m2, respectively, and positive (<span class="hlt">warming</span>) instantaneous DREATMAB up to 340W/m2 are found for the SW spectrum, during daytime. Opposite but less pronounced effects are encountered for the LW radiation and during nightime. Due to these perturbations on the radiation field, the surface temperature is reduced locally by up to 8°C during daytime and increased by up to 4°C during nightime. It is found that the regional average NET DREs can be as large as -12W/m2, -45W/m2, -30W/m2 and 27W/m2 for TOA, SURF, NETSURF and ATMAB, respectively. Impacts on atmospheric stability and <span class="hlt">dust</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.U11A0003B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.U11A0003B"><span>Improved <span class="hlt">Dust</span> Forecast Products for Southwest Asia Forecasters through <span class="hlt">Dust</span> Source Database Advancements</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brooks, G. R.</p> <p>2011-12-01</p> <p><span class="hlt">Dust</span> storm forecasting is a critical part of military theater operations in Afghanistan and Iraq as well as other strategic areas of the globe. The Air Force Weather Agency (AFWA) has been using the <span class="hlt">Dust</span> Transport Application (DTA) as a forecasting tool since 2001. Initially developed by The Johns Hopkins University Applied Physics Laboratory (JHUAPL), output products include <span class="hlt">dust</span> concentration and reduction of visibility due to <span class="hlt">dust</span>. The performance of the products depends on several factors including the underlying <span class="hlt">dust</span> source database, treatment of soil moisture, parameterization of <span class="hlt">dust</span> processes, and validity of the input atmospheric model data. Over many years of analysis, seasonal <span class="hlt">dust</span> forecast biases of the DTA have been observed and documented. As these products are unique and indispensible for U.S. and NATO forces, amendments were required to provide the best forecasts possible. One of the quickest ways to scientifically address the <span class="hlt">dust</span> concentration biases noted over time was to analyze the weaknesses in, and adjust the <span class="hlt">dust</span> source database. <span class="hlt">Dust</span> source database strengths and weaknesses, the satellite analysis and adjustment process, and tests which confirmed the resulting improvements in the final <span class="hlt">dust</span> concentration and visibility products will be shown.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20020045391','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20020045391"><span>Dynamics of Solar System <span class="hlt">Dust</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Dermott, Stanley F.</p> <p>2002-01-01</p> <p>The ongoing aim of the research is to investigate the dynamical and physical evolution of interplanetary <span class="hlt">dust</span> particles in order to produce a detailed global model of the zodiacal cloud and its constituent <span class="hlt">components</span> that is capable of predicting thermal fluxes in mid-infrared wave bands to an accuracy of 1% or better; with the additional aim of exploiting this research as a basis for predicting structure in exozodiacal clouds that may be signatures of unseen planets.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007DPS....39.4002T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007DPS....39.4002T"><span>Vertical Profiles Of Temperature And <span class="hlt">Dust</span> Derived From Mars Climate Sounder</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Teanby, Nicholas; Irwin, P. G.; Howett, C.; Calcutt, S.; Lolachi, R.; Bowles, N.; Taylor, F.; Schofield, J. T.; Kleinboehl, A.; McCleese, D. J.</p> <p>2007-10-01</p> <p>Mars Climate Sounder (MCS) on board NASA's Mars Reconnaissance Orbiter (MRO) primarily operates as a limb sounding infrared radiometer. The small field of view and limb scanning mode allow retrieval of temperature and <span class="hlt">dust</span> properties from the surface up to approximately 80km with 5km vertical resolution. The polar orbit of MRO gives coverage of all latitudes at 3pm and 3am local time. The ability of MCS to sounds these altitudes at high spatial and temporal resolution gives a unique dataset with which to test our understanding of the Martian atmosphere. It also complements and extends upon previous climatalogical datasets (for example TES). Measured mid-infrared radiances from MCS were analysed using the correlated-k approximation with Oxford's NEMESIS retrieval software. The correlated-k approximation was compared with a line-by-line model to confirm its accuracy under Martian atmospheric conditions. <span class="hlt">Dust</span> properties were taken from analysis of TES data by Wolff and Clancy (2003). We present profiles of temperature and <span class="hlt">dust</span> for data covering September to December 2006. During this period Mars' north pole was experiencing summer and the south pole was in winter. Preliminary results show that high altitude <span class="hlt">warming</span> over the southern winter pole is greater than that predicted by models. Our results will be compared to numerical models of the Martian atmosphere and the implications discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ApJ...791...98V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ApJ...791...98V"><span>Searching for <span class="hlt">Dust</span> around Hyper Metal Poor Stars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Venn, Kim A.; Puzia, Thomas H.; Divell, Mike; Côté, Stephanie; Lambert, David L.; Starkenburg, Else</p> <p>2014-08-01</p> <p>We examine the mid-infrared fluxes and spectral energy distributions for stars with iron abundances [Fe/H] <-5, and other metal-poor stars, to eliminate the possibility that their low metallicities are related to the depletion of elements onto <span class="hlt">dust</span> grains in the formation of a debris disk. Six out of seven stars examined here show no mid-IR excesses. These non-detections rule out many types of circumstellar disks, e.g., a <span class="hlt">warm</span> debris disk (T <= 290 K), or debris disks with inner radii <=1 AU, such as those associated with the chemically peculiar post-asymptotic giant branch spectroscopic binaries and RV Tau variables. However, we cannot rule out cooler debris disks, nor those with lower flux ratios to their host stars due to, e.g., a smaller disk mass, a larger inner disk radius, an absence of small grains, or even a multicomponent structure, as often found with the chemically peculiar Lambda Bootis stars. The only exception is HE0107-5240, for which a small mid-IR excess near 10 μm is detected at the 2σ level; if the excess is real and associated with this star, it may indicate the presence of (recent) <span class="hlt">dust</span>-gas winnowing or a binary system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19880027290&hterms=physical+chemistry&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dphysical%2Bchemistry','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19880027290&hterms=physical+chemistry&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dphysical%2Bchemistry"><span>Composition, structure, and chemistry of interstellar <span class="hlt">dust</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Tielens, A. G. G. M.; Allamandola, L. J.</p> <p>1987-01-01</p> <p>Different <span class="hlt">dust</span> <span class="hlt">components</span> present in the interstellar medium (IM) such as amorphous carbon, polycyclic aromatic hydrocarbons, and those IM <span class="hlt">components</span> which are organic refractory grains and icy grain mantles are discussed as well as their relative importance. The physical properties of grain surface chemistry are discussed with attention given to the surface structure of materials, the adsorption energy and residence time of species on a grain surface, and the sticking probability. Consideration is also given to the contribution of grains to the gas-phase composition of molecular clouds.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040087095&hterms=grain+dust&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dgrain%2Bdust','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040087095&hterms=grain+dust&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dgrain%2Bdust"><span>Formation and Destruction Processes of Interstellar <span class="hlt">Dust</span>: From Organic Molecules to carbonaceous Grains</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Salama, F.; Biennier, L.</p> <p>2004-01-01</p> <p>The study of the formation and destruction processes of cosmic <span class="hlt">dust</span> is essential to understand and to quantify the budget of extraterrestrial organic molecules. interstellar <span class="hlt">dust</span> presents a continuous size distribution from large molecules, radicals and ions to nanometer-sized particles to micron-sized grains. The lower end of the <span class="hlt">dust</span> size distribution is thought to be responsible for the ubiquitous spectral features that are seen in emission in the IR (UIBs) and in absorption in the visible (DIBs). The higher end of the <span class="hlt">dust</span>-size distribution is thought to be responsible for the continuum emission plateau that is seen in the IR and for the strong absorption seen in the interstellar UV extinction curve. All these spectral signatures are characteristic of cosmic organic materials that are ubiquitous and present in various forms from gas-phase molecules to solid-state grains. Although <span class="hlt">dust</span> with all its <span class="hlt">components</span> plays an important role in the evolution of interstellar chemistry and in the formation of organic molecules, little is known on the formation and destruction processes of <span class="hlt">dust</span>. Recent space observations in the UV (HST) and in the IR (ISO) help place size constraints on the molecular <span class="hlt">component</span> of carbonaceous IS <span class="hlt">dust</span> and indicate that small (ie., subnanometer) PAHs cannot contribute significantly to the IS features in the UV and in the IR. Studies of large molecular and nano-sized IS <span class="hlt">dust</span> analogs formed from PAH precursors have been performed in our laboratory under conditions that simulate diffuse ISM environments (the particles are cold -100 K vibrational energy, isolated in the gas phase and exposed to a high-energy discharge environment in a cold plasma). The species (molecules, molecular fragments, ions, nanoparticles, etc) formed in the pulsed discharge nozzle (PDN) plasma source are detected with a high-sensitivity cavity ring-down spectrometer (CRDS). We will present new experimental results that indicate that nanoparticles are generated in the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011ApJ...738..112D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011ApJ...738..112D"><span><span class="hlt">Warm</span> H2O and OH Disk Emission in V1331 Cyg</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Doppmann, Greg W.; Najita, Joan R.; Carr, John S.; Graham, James R.</p> <p>2011-09-01</p> <p>We present high-resolution (R = 24, 000) L-band spectra of the young intermediate-mass star V1331 Cyg obtained with NIRSPEC on the Keck II telescope. The spectra show strong, rich emission from water and OH that likely arises from the <span class="hlt">warm</span> surface region of the circumstellar disk. We explore the use of the new BT2 water line list in fitting the spectra, and we find that it does a much better job than the well-known HITRAN water line list in the observed wavelength range and for the <span class="hlt">warm</span> temperatures probed by our data. By comparing the observed spectra with synthetic disk emission models, we find that the water and OH emission lines have similar widths (FWHM ~= 18 km s-1). If the line widths are set by disk rotation, the OH and water emission lines probe a similar range of disk radii in this source. The water and OH emission are consistent with thermal emission for both <span class="hlt">components</span> at a temperature ~1500 K. The column densities of the emitting water and OH are large, ~1021 cm-2 and ~1020 cm-2, respectively. Such a high column density of water is more than adequate to shield the disk midplane from external UV irradiation in the event of complete <span class="hlt">dust</span> settling out of the disk atmosphere, enabling chemical synthesis to continue in the midplane despite a harsh external UV environment. The large OH-to-water ratio is similar to expectations for UV irradiated disks, although the large OH column density is less easily accounted for. Data presented herein were obtained at the W. M. Keck Observatory from telescope time allocated to the National Aeronautics and Space Administration through the agency's scientific partnership with the California Institute of Technology and the University of California. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PhRvD..95j3511P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PhRvD..95j3511P"><span>Line-of-sight extrapolation noise in <span class="hlt">dust</span> polarization</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Poh, Jason; Dodelson, Scott</p> <p>2017-05-01</p> <p>The B-modes of polarization at frequencies ranging from 50-1000 GHz are produced by Galactic <span class="hlt">dust</span>, lensing of primordial E-modes in the cosmic microwave background (CMB) by intervening large scale structure, and possibly by primordial B-modes in the CMB imprinted by gravitational waves produced during inflation. The conventional method used to separate the <span class="hlt">dust</span> <span class="hlt">component</span> of the signal is to assume that the signal at high frequencies (e.g. 350 GHz) is due solely to <span class="hlt">dust</span> and then extrapolate the signal down to a lower frequency (e.g. 150 GHz) using the measured scaling of the polarized <span class="hlt">dust</span> signal amplitude with frequency. For typical Galactic thermal <span class="hlt">dust</span> temperatures of ˜20 K , these frequencies are not fully in the Rayleigh-Jeans limit. Therefore, deviations in the <span class="hlt">dust</span> cloud temperatures from cloud to cloud will lead to different scaling factors for clouds of different temperatures. Hence, when multiple clouds of different temperatures and polarization angles contribute to the integrated line-of-sight polarization signal, the relative contribution of individual clouds to the integrated signal can change between frequencies. This can cause the integrated signal to be decorrelated in both amplitude and direction when extrapolating in frequency. Here we carry out a Monte Carlo analysis on the impact of this line-of-sight extrapolation noise on a greybody <span class="hlt">dust</span> model consistent with Planck and Pan-STARRS observations, enabling us to quantify its effect. Using results from the Planck experiment, we find that this effect is small, more than an order of magnitude smaller than the current uncertainties. However, line-of-sight extrapolation noise may be a significant source of uncertainty in future low-noise primordial B-mode experiments. Scaling from Planck results, we find that accounting for this uncertainty becomes potentially important when experiments are sensitive to primordial B-mode signals with amplitude r ≲0.0015 in the greybody <span class="hlt">dust</span> models considered in this</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.A21C0064G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.A21C0064G"><span>Large-scale Desert <span class="hlt">Dust</span> Deposition on the Himalayan Snow Cover: A Climatological Perspective from Satellite Observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gautam, R.; Hsu, N. C.; Lau, W. K.</p> <p>2013-12-01</p> <p>The Himalaya-Tibetan Plateau (HTP) has a profound influence on the Asian climate. The HTP are also among the largest snow/ice-covered regions on the Earth and provide major freshwater resource to the downstream densely-populated regions of Asia. Recent studies indicate climate <span class="hlt">warming</span> over the HTP amplified by atmospheric heating and deposition of absorbing aerosols (e.g. <span class="hlt">dust</span> and soot) over the HTP snowpack and glaciers. Recently, greater attention has focused on the effects of soot deposition on accelerated snowmelt and glacier retreat in the HTP, associated with increasing anthropogenic emissions in Asia. On the other hand, the role of transported <span class="hlt">dust</span> affecting snow albedo/melt is not well understood over the HTP, in spite of the large annual cycle of mineral <span class="hlt">dust</span> loading, particularly over the northern parts of south Asia during pre-monsoon season. This study addresses the large-scale effects of <span class="hlt">dust</span> deposition on snow albedo in the elevated HTP from a satellite observational perspective. <span class="hlt">Dust</span> aerosol transport, from southwest Asian arid regions, is observed in satellite imagery as darkening of the Himalayan snowpack. Additionally, multi-year spaceborne lidar observations, from CALIPSO, also show <span class="hlt">dust</span> advected to elevated altitudes (~5km) over the Himalayan foothills, and episodically reaching the top of the western Himalaya. Spectral surface reflectance analysis of <span class="hlt">dust</span>-laden snow cover (from MODIS) indicates enhanced absorption in the shorter visible wavelengths, yielding a significant gradient in the visible-nearIR reflectance spectrum. While soot in snow is difficult to distinguish from remote sensing, our spectral reflectance analysis of <span class="hlt">dust</span> detection in the snowpack is consistent with theoretical simulations of snow darkening due to <span class="hlt">dust</span> impurity. We find that the western HTP, in general, is influenced by enhanced <span class="hlt">dust</span> deposition due to its proximity to major <span class="hlt">dust</span> sources (and prevailing <span class="hlt">dust</span> transport pathways), compared to the eastern HTP. Coinciding</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMPP21C1280S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMPP21C1280S"><span>A <span class="hlt">dust</span> record from Permo-Pennsylvanian shallow-water carbonates of Iran: Glacial-interglacial variation proximal to the Gondwanan ice sheets</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sardar Abadi, M.; Soreghan, G. S.</p> <p>2017-12-01</p> <p>The Late Paleozoic was earth's longest Phanerozoic glaciation, with ice sheets ultimately covering large parts of the Gondwanan continent, to latitudes as low as 32°S during peak icehouse conditions (Evans, 2003). Here we focus on the sedimentology, paleoecology and <span class="hlt">dust</span> record of strata of the Central Persian Terrane (CPT) that accumulated during the Middle Pennsylvanian to earliest Permian acme of the Late Paleozoic Ice Age (LPIA). The CPT was located along the northern Gondwanan margin, within the Paleo-Tethyan ocean at 30º S. Despite its mid-latitude paleoposition, the mid-Pennsylvanian of the Absheni Formation (Sanandaj-Sirjan Zone) preserves calcareous (formerly aragonitic) green algae, clotted micritic textures indicative of microbial carbonate precipitation, and extensive oolitic carbonates that record CaCO3 supersaturation. The earliest Permian interval of the Emarat Formation (Alborz Basin) consists of thick algally coated oncolitic limestone, also present in correlative strata of the CPT. No evidence exists for fluvial or deltaic influences in these strata; rather, these data indicate <span class="hlt">warm</span>-water conditions across an extensive shallow-water carbonate system. This setting contrasts strikingly with the glacial conditions recorded in, e.g. coeval strata of the Arabian plate (within 1000 km). The juxtaposition of such contrasting lithologic records can perhaps be reconciled with a <span class="hlt">warm</span>-water Paleotethyan current that promoted larval dispersal to higher southern latitudes. The non-authigenic silicate fractions extracted from these carbonates record atmospheric <span class="hlt">dust</span> and comprise quartz, clay, trace feldspar and heavy minerals. The weight % <span class="hlt">dust</span> from these carbonates varies from 0.15% to 25.5% with peak values in proximity to inferred sequence boundaries (glacial lowstands), and covary with values of detrital (<span class="hlt">dust</span>) proxies (Ti, Sr, K, Al, Zr) and magnetic susceptibility (χin). Although awaiting MAR estimates, preliminary observations indicate increased</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29522999','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29522999"><span>Bacillus licheniformis in geogenic <span class="hlt">dust</span> induces inflammation in respiratory epithelium.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Pickering, Janessa; Teo, Teck Hui; Thornton, Ruth B; Kirkham, Lea-Ann; Zosky, Graeme R; Clifford, Holly D</p> <p>2018-07-01</p> <p>Exposure to environmental geogenic (or earth-derived) <span class="hlt">dust</span> can lead to more frequent and severe infections in the human airway. Particulate matter < 10 µm (PM 10 ) is the <span class="hlt">component</span> of air pollution that is commonly associated with the exacerbation of respiratory diseases. We have previously demonstrated that mice exposed to geogenic <span class="hlt">dust</span> PM 10 experienced an exacerbation of inflammatory responses to influenza A virus. Whether geogenic <span class="hlt">dust</span> PM 10 also exacerbates respiratory bacterial infection is not yet known, nor are the <span class="hlt">components</span> of the <span class="hlt">dust</span> that drive these responses. We treated airway bronchial epithelial cells (NuLi-1) with UV-irradiated geogenic <span class="hlt">dust</span> PM 10 from six remote Western Australian towns. High levels of IL-6 and IL-8 production were observed, as well as persistent microbial growth. 16 S rRNA sequencing of the growth identified the microbe as Bacillus licheniformis, a spore-forming, environmentally abundant bacterium. We next investigated the interaction of B. licheniformis with respiratory epithelium in vitro to determine whether this exacerbated infection with a bacterial respiratory pathogen (non-typeable Haemophilus influenzae, NTHi). Heat treatment (100 °C) of all PM 10 samples eliminated B. licheniformis contamination and reduced epithelial inflammatory responses, suggesting that heat-labile and/or microbial factors were involved in the host response to geogenic <span class="hlt">dust</span> PM 10 . We then exposed NuLi-1 epithelium to increasing doses of the isolated Bacillus licheniformis (multiplicity of infection of 10:1, 1:1 or 0.1:1 bacteria: cells) for 1, 3, and 24 h. B. licheniformis and NTHi infection (association and invasion) was assessed using a standard gentamicin survival assay, and epithelial release of IL-6 and IL-8 was measured using a bead based immunoassay. B. licheniformis was cytotoxic to NuLi-1 cells at 24 h. At 3 h post-challenge, B. licheniformis elicited high IL-6 and IL-8 inflammatory responses from NuLi-1 cells compared with</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110005542','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110005542"><span>Airborne <span class="hlt">Dust</span>, "The Good Guy or the Bad Guy": How Much do We Know?</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Tsay, Si-Chee</p> <p>2010-01-01</p> <p> as the Joint Aerosol Monsoon Experiment (JAMEX), a core element of the Asian Monsoon Years (AMY, 2008-2012). SMART-COMMIT deployments during 2008 AMY/JAMEX were conducted in northwestern China to characterize the properties of <span class="hlt">dust</span>-laden aerosols. In 2009, SMART-COMMIT also participated in the JAMEX/RAJO-MEGHA (Radiation, Aerosol Joint Observations-Monsoon Experiment in the Gangetic-Himalayan Area; Sanskrit for <span class="hlt">Dust</span>-Cloud) to study the aerosol properties, solar absorption and the associated atmospheric <span class="hlt">warming</span>, and the climatic impact of elevated aerosols during the premonsoon season in South Asia. To fully characterize the properties of airborne <span class="hlt">dust</span> in the field is an important but challenging task. In this seminar, we will present our recent measurements and retrievals of airborne <span class="hlt">dust</span> properties.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20020021570&hterms=nolan&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dnolan','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20020021570&hterms=nolan&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dnolan"><span><span class="hlt">Warm</span>-Core Intensification of a Hurricane Through Horizontal Eddy Heat Transports Inside the Eye</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Braun, Scott A.; Montgomery, Michael T.; Fulton, John; Nolan, David S.</p> <p>2001-01-01</p> <p>A simulation of Hurricane Bob (1991) using the PSU/NCAR MM5 mesoscale model with a finest mesh spacing of 1.3 km is used to diagnose the heat budget of the hurricane. Heat budget terms, including latent and radiative heating, boundary layer forcing, and advection terms were output directly from the model for a 6-h period with 2-min frequency. Previous studies of <span class="hlt">warm</span> core formation have emphasized the <span class="hlt">warming</span> associated with gentle subsidence within the eye. The simulation of Hurricane Bob also identifies subsidence <span class="hlt">warming</span> as a major factor for eye <span class="hlt">warming</span>, but also shows a significant contribution from horizontal advective terms. When averaged over the area of the eye, excluding the eyewall (at least in an azimuthal mean sense), subsidence is found to strongly <span class="hlt">warm</span> the mid-troposphere (2-9 km) while horizontal advection <span class="hlt">warms</span> the mid to upper troposphere (5-13 km) with about equal magnitude. Partitioning of the horizontal advective terms into azimuthal mean and eddy <span class="hlt">components</span> shows that the mean radial circulation cannot, as expected, generally contribute to this <span class="hlt">warming</span>, but that it is produced almost entirely by the horizontal eddy transport of heat into the eye. A further breakdown of the eddy <span class="hlt">components</span> into azimuthal wave numbers 1, 2, and higher indicates that the <span class="hlt">warming</span> is dominated by wave number 1 asymmetries, with smaller contributions coming from higher wave numbers. <span class="hlt">Warming</span> by horizontal eddy transport is consistent with idealized modeling of vortex Rossby waves and work is in progress to identify and clarify the role of vortex Rossby waves in <span class="hlt">warm</span>-core intensification in both the full-physics model and idealized models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.A33L0354K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.A33L0354K"><span>Mechanisms and Effects of Summertime Transport of African <span class="hlt">Dust</span> Through the Tokar Mountain Gap to the Red Sea and Arabian Peninsula</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kalenderski, S.; Stenchikov, G. L.</p> <p>2015-12-01</p> <p>Very high <span class="hlt">dust</span> loading over the Red Sea region in summer strongly affects the nutrition balance and thermal and dynamic regimes of the sea. The observations suggest that small-scale local dynamic and orographic effects, from both the Arabian and African sides, strongly contribute to <span class="hlt">dust</span> plume formation. To better understand and quantify these processes we present here the first high resolution modeling study of the <span class="hlt">dust</span> outbreak phenomena in June 2012 over East Africa, the Red Sea, and the Arabian Peninsula using the WRF-Chem model. We identified several <span class="hlt">dust</span> generating dynamical processes that range from convective to synoptic scales, including: synoptic cyclones, nocturnal low-level jets, and cold pools of mesoscale convective systems. The simulations reveal an eastward transport of African <span class="hlt">dust</span> across the Red Sea. Over the northern part of the Red Sea most of the <span class="hlt">dust</span> transport occurs beyond 2 km above ground level and is strengthened by a pressure gradient formed by low pressure over the eastern Mediterranean and high pressure over the Arabian Peninsula. Across the central and southern parts of the Red Sea <span class="hlt">dust</span> is mostly transported below 2 km height. During the study period <span class="hlt">dust</span> is a dominant contributor (87%) to aerosol optical depth (AOD), producing a domain average cooling effect of -12.1 W m-2 at surface, a <span class="hlt">warming</span> of 7.1 W m-2 in the atmosphere, and a residual cooling of -4.9 W m-2 at the top of the atmosphere. WRF-Chem simulations demonstrate that both dry and wet deposition processes contribute significantly to <span class="hlt">dust</span> removal from the atmosphere. During the <span class="hlt">dust</span> outbreak 49.2 Tg of <span class="hlt">dust</span> deposits within the calculation domain, which is approximately 90% of the total <span class="hlt">dust</span> emission of 54.5 Tg. Model results compare well with available ground-based and satellite observations but generally underestimate the observed AOD maximum values.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70185032','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70185032"><span>Iron oxide minerals in <span class="hlt">dust</span>-source sediments from the Bodélé Depression, Chad: Implications for radiative properties and Fe bioavailability of <span class="hlt">dust</span> plumes from the Sahara</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Moskowitz, Bruce M; Reynolds, Richard L.; Goldstein, Harland L.; Beroquo, Thelma; Kokaly, Raymond F.; Bristow, Charlie S</p> <p>2016-01-01</p> <p>Atmospheric mineral <span class="hlt">dust</span> can influence climate and biogeochemical cycles. An important <span class="hlt">component</span> of mineral <span class="hlt">dust</span> is ferric oxide minerals (hematite and goethite) which have been shown to influence strongly the optical properties of <span class="hlt">dust</span> plumes and thus affect the radiative forcing of global <span class="hlt">dust</span>. Here we report on the iron mineralogy of <span class="hlt">dust</span>-source samples from the Bodélé Depression (Chad, north-central Africa), which is estimated to be Earth’s most prolific <span class="hlt">dust</span> producer and may be a key contributor to the global radiative budget of the atmosphere as well as to long-range nutrient transport to the Amazon Basin. By using a combination of magnetic property measurements, Mössbauer spectroscopy, reflectance spectroscopy, chemical analysis, and scanning electron microscopy, we document the abundance and relative amounts of goethite, hematite, and magnetite in <span class="hlt">dust</span>-source samples from the Bodélé Depression. The partition between hematite and goethite is important to know to improve models for the radiative effects of ferric oxide minerals in mineral <span class="hlt">dust</span> aerosols. The combination of methods shows (1) the dominance of goethite over hematite in the source sediments, (2) the abundance and occurrences of their nanosize <span class="hlt">components</span>, and (3) the ubiquity of magnetite, albeit in small amounts. Dominant goethite and subordinate hematite together compose about 2% of yellow-reddish <span class="hlt">dust</span>-source sediments from the Bodélé Depression and contribute strongly to diminution of reflectance in bulk samples. These observations imply that <span class="hlt">dust</span> plumes from the Bodélé Depression that are derived from goethite-dominated sediments strongly absorb solar radiation. The presence of ubiquitous magnetite (0.002–0.57 wt%) is also noteworthy for its potentially higher solubility relative to ferric oxide and for its small sizes, including PM < 0.1 μm. For all examined samples, the average iron apportionment is estimated at about 33% in ferric oxide minerals, 1.4% in magnetite, and 65</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://eosweb.larc.nasa.gov/project/misr/gallery/middle_east_dust','SCIGOV-ASDC'); return false;" href="https://eosweb.larc.nasa.gov/project/misr/gallery/middle_east_dust"><span>Middle East <span class="hlt">Dust</span></span></a></p> <p><a target="_blank" href="http://eosweb.larc.nasa.gov/">Atmospheric Science Data Center </a></p> <p></p> <p>2013-04-16</p> <p>... only some of the <span class="hlt">dust</span> over eastern Syria and southeastern Turkey can be discerned. The <span class="hlt">dust</span> is much more obvious in the center panel, ... 18, 2002 - A large <span class="hlt">dust</span> plume extends across Syria and Turkey. project:  MISR category:  gallery ...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70028569','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70028569"><span>A 16-year record of eolian <span class="hlt">dust</span> in Southern Nevada and California, USA: Controls on <span class="hlt">dust</span> generation and accumulation</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Reheis, M.C.</p> <p>2006-01-01</p> <p>An ongoing project monitors modern <span class="hlt">dust</span> accumulation in the arid southwestern United States to (1) determine the rate and composition of <span class="hlt">dust</span> inputs to soils and (2) relate <span class="hlt">dust</span> accumulation to weather patterns to help predict the effects of climate change on <span class="hlt">dust</span> production and accumulation. The 16-year records of 35 <span class="hlt">dust</span>-trap sites in the eastern Mojave Desert and southern Great Basin reveal how generation and accumulation of <span class="hlt">dust</span>, including the silt-clay, carbonate, and soluble-salt fractions, is affected by the amount and seasonal distribution of rainfall and the behavior of different source types (alluvium, dry playas, and wet playas). Accumulation rates (fluxes) of the silt-clay fraction of <span class="hlt">dust</span>, including carbonates, range from about 2-20 g/m2/yr. Average rates are higher in the southern part of the study area (south of latitude 36.5??N) and annually fluctuate over a larger range than rates in the northern part of the area. Sites throughout the study area show peaks in <span class="hlt">dust</span> flux in the 1984-1985 sampling period and again in 1997-1999; northern sites also show increased flux in 1987-1988 and southern sites in 1989-1991. These peaks of <span class="hlt">dust</span> flux correspond with both La Nina (dry) conditions and with strong El Nino (wet) periods. The accumulation rates of different <span class="hlt">components</span> of mineral <span class="hlt">dusts</span> fluctuate differently. For example, soluble-salt flux increases in 1987-1988, coincident with a moderate El Nino event, and increases very strongly in 1997-1999, overlapping with a strong El Nino event. Both of these high-rainfall winters were preceded and accompanied by strong summer rains. In contrast, little or no change in soluble-salt flux occurred during other periods of high winter rainfall but little summer rain, e.g. 1992-1995. The differences between northern vs. southern sites and between sites with playa <span class="hlt">dust</span> sources vs. alluvial <span class="hlt">dust</span> sources indicate that regional differences in the response of precipitation and vegetation growth to ENSO influence and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19044616','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19044616"><span><span class="hlt">Dust</span> measurements in tokamaks (invited).</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Rudakov, D L; Yu, J H; Boedo, J A; Hollmann, E M; Krasheninnikov, S I; Moyer, R A; Muller, S H; Pigarov, A Yu; Rosenberg, M; Smirnov, R D; West, W P; Boivin, R L; Bray, B D; Brooks, N H; Hyatt, A W; Wong, C P C; Roquemore, A L; Skinner, C H; Solomon, W M; Ratynskaia, S; Fenstermacher, M E; Groth, M; Lasnier, C J; McLean, A G; Stangeby, P C</p> <p>2008-10-01</p> <p><span class="hlt">Dust</span> production and accumulation present potential safety and operational issues for the ITER. <span class="hlt">Dust</span> diagnostics can be divided into two groups: diagnostics of <span class="hlt">dust</span> on surfaces and diagnostics of <span class="hlt">dust</span> in plasma. Diagnostics from both groups are employed in contemporary tokamaks; new diagnostics suitable for ITER are also being developed and tested. <span class="hlt">Dust</span> accumulation in ITER is likely to occur in hidden areas, e.g., between tiles and under divertor baffles. A novel electrostatic <span class="hlt">dust</span> detector for monitoring <span class="hlt">dust</span> in these regions has been developed and tested at PPPL. In the DIII-D tokamak <span class="hlt">dust</span> diagnostics include Mie scattering from Nd:YAG lasers, visible imaging, and spectroscopy. Laser scattering is able to resolve particles between 0.16 and 1.6 microm in diameter; using these data the total <span class="hlt">dust</span> content in the edge plasmas and trends in the <span class="hlt">dust</span> production rates within this size range have been established. Individual <span class="hlt">dust</span> particles are observed by visible imaging using fast framing cameras, detecting <span class="hlt">dust</span> particles of a few microns in diameter and larger. <span class="hlt">Dust</span> velocities and trajectories can be determined in two-dimension with a single camera or three-dimension using multiple cameras, but determination of particle size is challenging. In order to calibrate diagnostics and benchmark <span class="hlt">dust</span> dynamics modeling, precharacterized carbon <span class="hlt">dust</span> has been injected into the lower divertor of DIII-D. Injected <span class="hlt">dust</span> is seen by cameras, and spectroscopic diagnostics observe an increase in carbon line (CI, CII, C(2) dimer) and thermal continuum emissions from the injected <span class="hlt">dust</span>. The latter observation can be used in the design of novel <span class="hlt">dust</span> survey diagnostics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26075927','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26075927"><span>Mechanical properties of <span class="hlt">dust</span> collected by <span class="hlt">dust</span> separators in iron ore sinter plants.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lanzerstorfer, Christof</p> <p>2015-01-01</p> <p>The flow-related mechanical properties of <span class="hlt">dusts</span> from the de-<span class="hlt">dusting</span> systems of several sinter plants were investigated. The mass median diameters of the <span class="hlt">dusts</span> were in the range from approximately 3 to 100 µm. Also, the bulk density of the <span class="hlt">dusts</span> varied in a wide range (approximately 400 to 2300 kg/m³). A good correlation between the bulk density and the mass median diameter for most of the <span class="hlt">dusts</span> was found. In contrast, the angles of repose did not vary very much, only for the coarsest <span class="hlt">dust</span> a significantly lower value was measured. The angles of internal friction as well as the wall friction angles were lower for coarse <span class="hlt">dust</span> and higher for fine <span class="hlt">dust</span>. The shear tests showed that both angles depend considerably on the stress level. At low stress, the angles decreased significantly with increasing values of stress, whereas at higher stress, the dependence was small or even disappeared. The only exception to this behaviour was shown by the finest <span class="hlt">dust</span>. The flowability decreased with the particle size. The flowability categories suggested by the three flowability indicators were passable only for the coarser <span class="hlt">dusts</span>. For the finer <span class="hlt">dusts</span>, the flowability was overestimated by all flowability indicators.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_24 --> <div id="page_25" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="481"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20030011397&hterms=Influence+clouds+climate&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DInfluence%2Bclouds%2Bclimate','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20030011397&hterms=Influence+clouds+climate&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DInfluence%2Bclouds%2Bclimate"><span>Deciphering the Role of Desert <span class="hlt">Dust</span> in the Climate Puzzle: The Mediterranean Israeli <span class="hlt">Dust</span> Experiment (MEIDEX)</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Levin, Zev; Joseph, Joachim; Mekler, Yuri; Israelevich, Peter; Ganor, Eli; Hilsenrath, Ernest; Janz, Scott</p> <p>2002-01-01</p> <p>Numerous studies have shown that aerosol particles may be one of the primary agents that can offset the climate <span class="hlt">warming</span> induced by the increase in the amount of atmospheric greenhouse gases. Desert aerosols are probably the most abundant and massive type of aerosol particles that are present in the atmosphere worldwide. These aerosols are carried over large distances and have various global impacts. They interact with clouds, impact the efficiency of their rain production and change their optical properties. They constitute one of the primary sources of minerals for oceanic life and influence the health of coral reefs. They have direct effects on human health, especially by inducing breathing difficulties in children. It was lately discovered that desert particles carry pathogens from the Sahara desert over the Atlantic Ocean, a fact that may explain the migration of certain types of diseases. Aerosols not only absorb solar radiation but also scatter it, so that their climatic effect is influenced not only by their physical properties and height distribution but also by the reflectivity of the underlying surface. This latter property changes greatly over land and is low over ocean surfaces. Aerosol plumes are emitted from discrete, sporadic sources in the desert areas of the world and are transported worldwide by the atmosphere's wind systems. For example, Saharan <span class="hlt">dust</span> reaches Mexico City, Florida, Ireland, Switzerland and the Mediterranean region, while Asian <span class="hlt">dust</span> reaches Alaska, Hawaii and the continental United States. This means that in order to assess its global effects, one must observe <span class="hlt">dust</span> from space. The Space Shuttle is a unique platform, because it flies over the major deserts of our planet, enabling measurements and remote sensing of the aerosols as they travel from source to sink regions. Such efforts must always be accompanied by in-situ data for validation and calibration, with direct sampling of the airborne particles. MEIDEX is a joint project of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25902494','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25902494"><span>Amplified Arctic <span class="hlt">warming</span> by phytoplankton under greenhouse <span class="hlt">warming</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Park, Jong-Yeon; Kug, Jong-Seong; Bader, Jürgen; Rolph, Rebecca; Kwon, Minho</p> <p>2015-05-12</p> <p>Phytoplankton have attracted increasing attention in climate science due to their impacts on climate systems. A new generation of climate models can now provide estimates of future climate change, considering the biological feedbacks through the development of the coupled physical-ecosystem model. Here we present the geophysical impact of phytoplankton, which is often overlooked in future climate projections. A suite of future <span class="hlt">warming</span> experiments using a fully coupled ocean-atmosphere model that interacts with a marine ecosystem model reveals that the future phytoplankton change influenced by greenhouse <span class="hlt">warming</span> can amplify Arctic surface <span class="hlt">warming</span> considerably. The <span class="hlt">warming</span>-induced sea ice melting and the corresponding increase in shortwave radiation penetrating into the ocean both result in a longer phytoplankton growing season in the Arctic. In turn, the increase in Arctic phytoplankton <span class="hlt">warms</span> the ocean surface layer through direct biological heating, triggering additional positive feedbacks in the Arctic, and consequently intensifying the Arctic <span class="hlt">warming</span> further. Our results establish the presence of marine phytoplankton as an important potential driver of the future Arctic climate changes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4434777','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4434777"><span>Amplified Arctic <span class="hlt">warming</span> by phytoplankton under greenhouse <span class="hlt">warming</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Park, Jong-Yeon; Kug, Jong-Seong; Bader, Jürgen; Rolph, Rebecca; Kwon, Minho</p> <p>2015-01-01</p> <p>Phytoplankton have attracted increasing attention in climate science due to their impacts on climate systems. A new generation of climate models can now provide estimates of future climate change, considering the biological feedbacks through the development of the coupled physical–ecosystem model. Here we present the geophysical impact of phytoplankton, which is often overlooked in future climate projections. A suite of future <span class="hlt">warming</span> experiments using a fully coupled ocean−atmosphere model that interacts with a marine ecosystem model reveals that the future phytoplankton change influenced by greenhouse <span class="hlt">warming</span> can amplify Arctic surface <span class="hlt">warming</span> considerably. The <span class="hlt">warming</span>-induced sea ice melting and the corresponding increase in shortwave radiation penetrating into the ocean both result in a longer phytoplankton growing season in the Arctic. In turn, the increase in Arctic phytoplankton <span class="hlt">warms</span> the ocean surface layer through direct biological heating, triggering additional positive feedbacks in the Arctic, and consequently intensifying the Arctic <span class="hlt">warming</span> further. Our results establish the presence of marine phytoplankton as an important potential driver of the future Arctic climate changes. PMID:25902494</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040071147&hterms=mcd&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dmcd','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040071147&hterms=mcd&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dmcd"><span>Studying the <span class="hlt">Warm</span> Layer and the Hardening Factor in Cygnus X-1</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Yao, Yangsen; Zhang, Shuangnan; Zhang, Xiaoling; Feng, Yuxin</p> <p>2002-01-01</p> <p>As the first dynamically determined black hole X-ray binary system, Cygnus X-1 has been studied extensively. However, its broadband spectrum observed with BeppoSax is still not well understood. Besides the soft excess described by the multi-color disk model (MCD), the power-law hard <span class="hlt">component</span> and a broad excess feature above 10 keV (a disk reflection <span class="hlt">component</span>), there is also an additional soft <span class="hlt">component</span> around 1 keV, whose origin is not known currently. Here we propose that the additional soft <span class="hlt">component</span> is due to the thermal Comptonization between the soft disk photons and a <span class="hlt">warm</span> plasma cloud just above the disk, i.e., a <span class="hlt">warm</span> layer. We use the Monte-Carlo technique to simulate this Compton scattering process and build a table model based on our simulation results. With this table model, we study the disk structure and estimate the hardening factor to the MCD <span class="hlt">component</span> in Cygnus X-1.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28409517','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28409517"><span>Could the negative effects of static stretching in <span class="hlt">warm</span>-up be restored by sport specific exercise?</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bengtsson, Victor; Yu, Ji-Guo; Gilenstam, Kajsa</p> <p>2017-04-13</p> <p>Static stretching (SS) is widely used in <span class="hlt">warm</span>-up as it is generally believed to increase mobility and reduce the risk of injury; however, SS has been shown to induce transient negative effects on subsequent muscle performance. Interestingly, recent studies have shown that sport specific exercise could restore SS-induced negative effects on certain sports, especially of explosive muscular performance. Whether sport specific exercise could restore SS-induced negative effects on isokinetic muscle performance remains unclear. The present study conducted two different <span class="hlt">warm</span>-ups: 2-<span class="hlt">component</span> <span class="hlt">warm</span>-up and 3-<span class="hlt">component</span> <span class="hlt">warm</span>-up on 15 university students. Both protocols contained low intensity aerobic exercise and sport specific exercise, whereas the 3-<span class="hlt">component</span> <span class="hlt">warm</span>-up also contained SS which has been previously proven to induce negative effects on subsequent muscle performance. After the <span class="hlt">warm</span>-ups, the subjects performed an isokinetic test on a Biodex. To make the sport specific exercise mimic the subsequent test, both included concentric isokinetic knee extension. During the tests, muscle performance of peak torque, mean power, and total work was recorded. Comparison of the measurements on each parameter between the two <span class="hlt">warm</span>-ups was performed using paired t test. The comparisons did not reveal any significant difference in the measurement of any parameter between the two different <span class="hlt">warm</span>-up protocols, and calculation of Cohen's revealed small effect sizes on all of the three variables. On basis of the present results and that the SS could induce transient negative effects on subsequent muscle performance, we concluded that the negative effects of the SS on the variables were restored by the isokinetic contractions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26433809','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26433809"><span><span class="hlt">Dust</span>-Metal Sources in an Urbanized Arid Zone: Implications for Health-Risk Assessments.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>García-Rico, Leticia; Meza-Figueroa, Diana; Gandolfi, A Jay; Del Río-Salas, Rafael; Romero, Francisco M; Meza-Montenegro, Maria Mercedes</p> <p>2016-04-01</p> <p>The available information concerning metal pollution in different <span class="hlt">dust</span> sources and the health effects in children remains limited in Mexico. This study focuses on Hermosillo, which is an urbanized area located in the Sonoran Desert in which soil resuspension and <span class="hlt">dust</span> emission processes are common. The metal content of arsenic (As), chromium (Cr), manganese (Mn), and lead (Pb) were determined in three <span class="hlt">dust</span> sources (playgrounds, roofs, and roads), each representing different exposure media (EM) for these elements. The metal levels in <span class="hlt">dust</span> were found in the order of Mn > Cr > Pb > As with the highest metal content found in road <span class="hlt">dust</span>. Despite the similar average metal distributions, principal <span class="hlt">component</span> analysis shows a clear separation of the three EM with playground <span class="hlt">dust</span> related to Cr and Mn and road <span class="hlt">dust</span> to As and Pb. However, the geoaccumulation index results indicate that <span class="hlt">dust</span> samples are uncontaminated to moderately polluted, except for Pb in road <span class="hlt">dust</span>, which is considerably high. In addition, the enrichment factor suggests an anthropogenic origin for all of the studied metals except for Mn. In this context, the hazard index (HI) for noncarcinogenic risk is >1 in this population and thus represents a potential health risk. The spatial distribution for each metal on EM and the HI related to the marginality index could represent a more accurate decision-making tool in risk assessment studies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1996ApJ...464..805B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1996ApJ...464..805B"><span>Grain Temperature and Infrared Emission from Carbon <span class="hlt">Dust</span> of Mixed Composition</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bartlett, S.; Duley, W. W.</p> <p>1996-06-01</p> <p>The equilibrium temperature of carbonaceous <span class="hlt">dust</span> grains whose composition is consistent with IR spectra of diffuse cloud and dense cloud <span class="hlt">dust</span> has been calculated using random covalent network (RCN) solutions for amorphous <span class="hlt">dust</span> having a mixed graphite, diamond, and polymeric hydrocarbon composition. An effective medium approximation has been adopted to describe optical and thermal constants for <span class="hlt">dust</span> compositions consistent with IR absorption spectra. A small amount of sp2 hybridized carbon in the form of aromatic rings is found to have a significant effect in reducing equilibrium temperature in <span class="hlt">dust</span> with high diamond/polymer content. This formalism has also been used to calculate nonequilibrium emission spectra of very small grains (VSGs) subjected to stochastic heating in the interstellar radiation field. Such grains are found to emit strongly in sharp IR bands associated with C-H bonds at 3.4 μm and longer wavelengths. The effect of varying graphite/diamond/hydrocarbon composition on nonequilibrium emission by VSGs can also be described using this formalism. The ratio of emission at 12 and 25 μm is found to be high for VSGs with a large fraction of diamond or polymeric hydrocarbon but decreases dramatically for <span class="hlt">dust</span> with a large sp2 aromatic <span class="hlt">component</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26475241','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26475241"><span>Urban <span class="hlt">dust</span> in the Guanzhong basin of China, part II: A case study of urban <span class="hlt">dust</span> pollution using the WRF-<span class="hlt">Dust</span> model.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Li, Nan; Long, Xin; Tie, Xuexi; Cao, Junji; Huang, Rujin; Zhang, Rong; Feng, Tian; Liu, Suixin; Li, Guohui</p> <p>2016-01-15</p> <p>We developed a regional <span class="hlt">dust</span> dynamical model (WRF-<span class="hlt">Dust</span>) to simulate surface <span class="hlt">dust</span> concentrations in the Guanzhong (GZ) basin of China during two typical <span class="hlt">dust</span> cases (19th Aug. and 26th Nov., 2013), and compared model results with the surface measurements at 17 urban and rural sites. The important improvement of the model is to employ multiple high-resolution (0.5-500 m) remote sensing data to construct <span class="hlt">dust</span> sources. The new data include the geographic information of constructions, croplands, and barrens over the GZ basin in summer and winter of 2013. For the first time, detailed construction <span class="hlt">dust</span> emissions have been introduced in a regional <span class="hlt">dust</span> model in large cities of China. Our results show that by including the detailed <span class="hlt">dust</span> sources, model performance at simulating <span class="hlt">dust</span> pollutions in the GZ basin is significantly improved. For example, the simulated <span class="hlt">dust</span> concentration average for the 17 sites increases from 28 μg m(-3) to 59 μg m(-3), closing to the measured concentration of 66 μg m(-3). In addition, the correlation coefficient (r) between the calculated and measured <span class="hlt">dust</span> concentrations is also improved from 0.17 to 0.57, suggesting that our model better presents the spatial variation. Further analysis shows that urban construction activities are the crucial source in controlling urban <span class="hlt">dust</span> pollutions. It should be considered by policy makers for mitigating particulate air pollution in many Chinese cities. Copyright © 2015 Elsevier B.V. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20160010670&hterms=desert&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Ddesert','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20160010670&hterms=desert&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Ddesert"><span>Three-Dimensional Distribution of a Major Desert <span class="hlt">Dust</span> Outbreak over East Asia in March 2008 Derived from IASI Satellite Observations</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cuesta, Juan; Eremenko, Maxim; Flamant, Cyrille; Dufour, Gaelle; Laurent, Benoît; Bergametti, Gilles; Hopfner, Michael; Orphal, Johannes; Zhou, Daniel</p> <p>2015-01-01</p> <p>We describe the daily evolution of the three-dimensional (3D) structure of a major <span class="hlt">dust</span> outbreak initiated by an extratropical cyclone over East Asia in early March 2008, using new aerosol retrievals derived from satellite observations of IASI (Infrared Atmospheric Sounding Interferometer). A novel auto-adaptive Tikhonov-Phillips-type approach called AEROIASI is used to retrieve vertical profiles of <span class="hlt">dust</span> extinction coefficient at 10 microns for most cloud-free IASI pixels, both over land and ocean. The <span class="hlt">dust</span> vertical distribution derived from AEROIASI is shown to agree remarkably well with along-track transects of Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) spaceborne lidar vertical profiles (mean biases less than 110 meters, correlation of 0.95, and precision of 260 meters for mean altitudes of the <span class="hlt">dust</span> layers). AEROIASI allows the daily characterization of the 3D transport pathways across East Asia of two <span class="hlt">dust</span> plumes originating from the Gobi and North Chinese deserts. From AEROIASI retrievals, we provide evidence that (i) both <span class="hlt">dust</span> plumes are transported over the Beijing region and the Yellow Sea as elevated layers above a shallow boundary layer, (ii) as they progress eastward, the <span class="hlt">dust</span> layers are lifted up by the ascending motions near the core of the extratropical cyclone, and (iii) when being transported over the <span class="hlt">warm</span> waters of the Japan Sea, turbulent mixing in the deep marine boundary layer leads to high <span class="hlt">dust</span> concentrations down to the surface. AEROIASI observations and model simulations also show that the progression of the <span class="hlt">dust</span> plumes across East Asia is tightly related to the advancing cold front of the extratropical cyclone.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1912885U','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1912885U"><span>Differences in ice nucleation behavior of arable and desert soil <span class="hlt">dust</span> in deposition nucleation regime</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ullrich, Romy; Vogel, Franziska; Möhler, Ottmar; Höhler, Kristina; Schiebel, Thea</p> <p>2017-04-01</p> <p>Soil <span class="hlt">dust</span> from arid and semi-arid regions is one of the most abundant aerosol types in the atmosphere with emission rates of about 1600 Tg per year (Andreae et al. (2009)). Therewith, soil <span class="hlt">dust</span> plays an important role for the atmospheric radiative transfer and also for the formation of clouds. Soil <span class="hlt">dust</span> refers to <span class="hlt">dust</span> sampled from agricultural used areas, to <span class="hlt">dust</span> from bare soil as well as to <span class="hlt">dust</span> from desert regions. By mass-spectrometric measurements of the chemical composition of ice residuals, mineral <span class="hlt">dust</span> as <span class="hlt">component</span> of soil <span class="hlt">dust</span> was found to be the major heterogeneous ice nucleating particle (INP) type (e.g. Cziczo et al. (2013)), in particular in the upper troposphere. Also in laboratory studies the ice nucleation efficiency of the different soil <span class="hlt">dusts</span> was investigated. It was shown that desert <span class="hlt">dusts</span> (Ullrich et al. (2017)) as well as soil <span class="hlt">dusts</span> from arable regions (O'Sullivan et al. (2014), Tobo et al. (2014)) are efficient INP. However, there is still a lack of data for ice nucleation on soil <span class="hlt">dusts</span> for temperatures below about 220 K. With the AIDA (Aerosol Interactions and Dynamics in the Atmosphere) cloud chamber, we are able to characterize the ice nucleation efficiency for different aerosol types to temperatures down to 180 K and high ice supersaturations. In order to extend the already existing AIDA data base for deposition nucleation on desert <span class="hlt">dusts</span> and agricultural soil <span class="hlt">dusts</span>, new experiments were done in the upper tropospheric temperature regime. This contribution will show the results of the new experiments with desert <span class="hlt">dust</span> in comparison to existing data for higher temperatures. The first data analysis confirms the temperature dependent trend of the ice nucleation activity as discussed and parameterized in a recent paper by Ullrich et al. (2017). Furthermore, the update and extension of the recently published parameterization of deposition nucleation for desert <span class="hlt">dust</span> to lower temperatures will be discussed. The experiments with agricultural soil</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhDT.......401S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhDT.......401S"><span>The Lunar <span class="hlt">Dust</span> Environment</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Szalay, Jamey Robert</p> <p></p> <p>Planetary bodies throughout the solar system are continually bombarded by <span class="hlt">dust</span> particles, largely originating from cometary activities and asteroidal collisions. Surfaces of bodies with thick atmospheres, such as Venus, Earth, Mars and Titan are mostly protected from incoming <span class="hlt">dust</span> impacts as these particles ablate in their atmospheres as 'shooting stars'. However, the majority of bodies in the solar system have no appreciable atmosphere and their surfaces are directly exposed to the flux of high speed <span class="hlt">dust</span> grains. Impacts onto solid surfaces in space generate charged and neutral gas clouds, as well as solid secondary ejecta <span class="hlt">dust</span> particles. Gravitationally bound ejecta clouds forming <span class="hlt">dust</span> exospheres were recognized by in situ <span class="hlt">dust</span> instruments around the icy moons of Jupiter and Saturn, and had not yet been observed near bodies with refractory regolith surfaces before NASA's Lunar <span class="hlt">Dust</span> and Environment Explorer (LADEE) mission. In this thesis, we first present the measurements taken by the Lunar <span class="hlt">Dust</span> Explorer (LDEX), aboard LADEE, which discovered a permanently present, asymmetric <span class="hlt">dust</span> cloud surrounding the Moon. The global characteristics of the lunar <span class="hlt">dust</span> cloud are discussed as a function of a variety of variables such as altitude, solar longitude, local time, and lunar phase. These results are compared with models for lunar <span class="hlt">dust</span> cloud generation. Second, we present an analysis of the groupings of impacts measured by LDEX, which represent detections of dense ejecta plumes above the lunar surface. These measurements are put in the context of understanding the response of the lunar surface to meteoroid bombardment and how to use other airless bodies in the solar system as detectors for their local meteoroid environment. Third, we present the first in-situ <span class="hlt">dust</span> measurements taken over the lunar sunrise terminator. Having found no excess of small grains in this region, we discuss its implications for the putative population of electrostatically lofted <span class="hlt">dust</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/16426748','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16426748"><span>Generation of urban road <span class="hlt">dust</span> from anti-skid and asphalt concrete aggregates.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Tervahattu, Heikki; Kupiainen, Kaarle J; Räisänen, Mika; Mäkelä, Timo; Hillamo, Risto</p> <p>2006-04-30</p> <p>Road <span class="hlt">dust</span> forms an important <span class="hlt">component</span> of airborne particulate matter in urban areas. In many winter cities the use of anti-skid aggregates and studded tires enhance the generation of mineral particles. The abrasion particles dominate the PM10 during springtime when the material deposited in snow is resuspended. This paper summarizes the results from three test series performed in a test facility to assess the factors that affect the generation of abrasion <span class="hlt">components</span> of road <span class="hlt">dust</span>. Concentrations, mass size distribution and composition of the particles were studied. Over 90% of the particles were aluminosilicates from either anti-skid or asphalt concrete aggregates. Mineral particles were observed mainly in the PM10 fraction, the fine fraction being 12% and submicron size being 6% of PM10 mass. The PM10 concentrations increased as a function of the amount of anti-skid aggregate dispersed. The use of anti-skid aggregate increased substantially the amount of PM10 originated from the asphalt concrete. It was concluded that anti-skid aggregate grains contribute to pavement wear. The particle size distribution of the anti-skid aggregates had great impact on PM10 emissions which were additionally enhanced by studded tires, modal composition, and texture of anti-skid aggregates. The results emphasize the interaction of tires, anti-skid aggregate, and asphalt concrete pavement in the production of <span class="hlt">dust</span> emissions. They all must be taken into account when measures to reduce road <span class="hlt">dust</span> are considered. The winter maintenance and springtime cleaning must be performed properly with methods which are efficient in reducing PM10 <span class="hlt">dust</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018A%26A...609A..85G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018A%26A...609A..85G"><span>Multiple origins for the DLA at zabs = 0.313 toward PKS 1127-145 indicated by a complex <span class="hlt">dust</span> depletion pattern of Ca, Ti, and Mn</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Guber, C. R.; Richter, P.; Wendt, M.</p> <p>2018-01-01</p> <p>Aims: We aim to investigate the <span class="hlt">dust</span> depletion properties of optically thick gas in and around galaxies and its origin we study in detail the <span class="hlt">dust</span> depletion patterns of Ti, Mn, and Ca in the multi-<span class="hlt">component</span> damped Lymanα (DLA) absorber at zabs = 0.313 toward the quasar PKS 1127-145. Methods: We performed a detailed spectral analysis of the absorption profiles of Ca II, Mn II, Ti II, and Na I associated with the DLA toward PKS 1127-145, based on optical high-resolution data obtained with the UVES instrument at the Very Large Telescope. We obtained column densities and Doppler-parameters for the ions listed above and determine their gas-phase abundances, from which we conclude on their <span class="hlt">dust</span> depletion properties. We compared the Ca and Ti depletion properties of this DLA with that of other DLAs. Results: One of the six analyzed absorption <span class="hlt">components</span> (<span class="hlt">component</span> 3) shows a striking underabundance of Ti and Mn in the gas-phase, indicating the effect of <span class="hlt">dust</span> depletion for these elements and a locally enhanced <span class="hlt">dust</span>-to-gas ratio. In this DLA and in other similar absorbers, the Mn II abundance follows that of Ti II very closely, implying that both ions are equally sensitive to the <span class="hlt">dust</span> depletion effects. Conclusions: Our analysis indicates that the DLA toward PKS 1127-145 has multiple origins. With its narrow line width and its strong <span class="hlt">dust</span> depletion, <span class="hlt">component</span> 3 points toward the presence of a neutral gas disk from a faint LSB galaxy in front of PKS 1127-145, while the other, more diffuse and <span class="hlt">dust</span>-poor, absorption <span class="hlt">components</span> possibly are related to tidal gas features from the interaction between the various, optically confirmed galaxy-group members. In general, the Mn/Ca II ratio in sub-DLAs and DLAs possibly serves as an important indicator to discriminate between <span class="hlt">dust</span>-rich and <span class="hlt">dust</span>-poor in neutral gas in and around galaxies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20060015637&hterms=planets+orbit+sun&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DWhy%2Bplanets%2Borbit%2Bsun','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20060015637&hterms=planets+orbit+sun&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DWhy%2Bplanets%2Borbit%2Bsun"><span>Comet <span class="hlt">Dust</span>: The Story of Planet Formation as Told by the Tiniest of Particles</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wooden, D. H.</p> <p>2005-01-01</p> <p>Our planetary system formed out of a gas-rich disk-shaped nebula with the early Sun at its center. Many small icy bodies were consumed by the formation of the giant planets. However, many km-size icy bodies were tossed out of the giant-planet region to the cold, distant reaches of our solar system. Comets remained in their places of cold storage until perturbed into orbits that carry them into the inner solar system where they pass relatively close to the Sun. Comets are <span class="hlt">warmed</span> by the Sun and shed material from their outer layers. The ices and gases shed by comets reveal simple and complex organic molecules were present at the time and in the region of the formation of the giant planets. Where the Earth was forming was too hot and had too intense sunlight for many of these ices and molecules to survive. The <span class="hlt">dust</span> shed by comets tells us that some stardust survived unaltered but much of the <span class="hlt">dust</span> was heated and crystallized before becoming part of the comet. Therefore, comet <span class="hlt">dust</span> grains tell of large radial migrations from the cold outer reaches near Neptune into the hot regions near the forming Sun, and then back out to the cold regions where icy comets were accreting and forming. On 2005 July 4, the NASA Deep Impact Mission hit a comet and ejected primitive materials fiom its interior. These materials were not released into the comet s coma during normal activity. Despite the many passages of this comet close to the Sun, these primitive volatile gases and <span class="hlt">dust</span> grains survived in its interior. Comet <span class="hlt">dust</span> grains show that cold and hot materials were mixed into the same tiny particle very early in the formation of the solar system, and these aggregate <span class="hlt">dust</span> grains never saw high temperatures again. The survival of primitive materials in comet nuclei suggests comets could have delivered organic molecules and primitive <span class="hlt">dust</span> grains to early Earth.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001DPS....33.3901H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001DPS....33.3901H"><span>Velocity Distributions of Interplanetary <span class="hlt">Dust</span> Derived from Astronomical Sky Spectra</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Huestis, D. L.; Ali, S.; Cosby, P. C.; Slanger, T. G.</p> <p>2001-11-01</p> <p>Characterization of interplanetary <span class="hlt">dust</span> is important for understanding the creation by accretion of planets and moons, the development of planetary atmospheres, and, potentially, for the initiation of prebiotic chemistry. The recent COBE mission has provided a profile in ecliptic coordinates of the distribution of interplanetary <span class="hlt">dust</span> particles through their thermal infrared emission. Additional information about interplanetary <span class="hlt">dust</span> can be extracted from its visible spectrum of scattered sunlight, called Zodiacal Light. Night sky spectra taken at large-aperture telescopes using high-resolution echelle spectrographs reveal Fraunhofer absorption features in the Zodiacal Light spectrum of scattered sunlight, a nuisance in subtraction from the spectrum of the extraterrestrial object under investigation. We are analyzing the intensity modulations and Doppler shifts of solar Fraunhofer absorption lines in the Zodiacal Light <span class="hlt">component</span> of sky spectra, donated by collaborating astronomers using Keck/HIRES and other high-performance astronomical facilities. Our objectives include velocity distributions of interplanetary <span class="hlt">dust</span> and improved separation of terrestrial and extraterrestrial sources in sky spectra. Participation of S. Ali was made possible by a grant from the NSF Physics Research Experiences for Undergraduates (REU) program.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016APS..DPPP10137L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APS..DPPP10137L"><span><span class="hlt">Dust</span> Particle Dynamics in The Presence of Highly Magnetized Plasmas</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lynch, Brian; Konopka, Uwe; Thomas, Edward; Merlino, Robert; Rosenberg, Marlene</p> <p>2016-10-01</p> <p>Complex plasmas are four <span class="hlt">component</span> plasmas that contain, in addition to the usual electrons, ions, and neutral atoms, macroscopic electrically charged (nanometer to micrometer) sized ``<span class="hlt">dust</span>'' particles. These macroscopic particles typically obtain a net negative charge due to the higher mobility of electrons compared to that of ions. Because the electrons, ions, and <span class="hlt">dust</span> particles are charged, their dynamics may be significantly modified by the presence of electric and magnetic fields. Possible consequences of this modification may be the charging rate and the equilibrium charge. For example, in the presence of a strong horizontal magnetic field (B >1 Tesla), it may be possible to observe <span class="hlt">dust</span> particle gx B deflection and, from that deflection, determine the <span class="hlt">dust</span> grain charge. In this poster, we present recent data from performing multiple particle dropping experiments to characterize the g x B deflection in the Magnetized Dusty Plasma Experiment (MDPX). This work is supported by funding from the U. S. Department of Energy Grant Number DE - SC0010485 and the NASA/Jet Propulsion Laboratory, JPL-1543114.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20020015753&hterms=evolution+rock&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Devolution%2Brock','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20020015753&hterms=evolution+rock&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Devolution%2Brock"><span>Chemical Evolution of Interstellar <span class="hlt">Dust</span> into Planetary Materials</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Fomenkova, M. N.; Chang, S.; DeVincenzi, Donald L. (Technical Monitor)</p> <p>1995-01-01</p> <p> residues wherein the H, C and N are largely retained and ultimately accreted in cometary <span class="hlt">dust</span>. The abundance of O is about the same for cometary <span class="hlt">dust</span>, meteorites and interstellar <span class="hlt">dust</span>. In all these samples, most of O in a solid phase is bonded to silicates. In dense molecular clouds, the abundance of O in <span class="hlt">dust</span>+mantles is significantly higher then in cometary <span class="hlt">dust</span>. This difference may reflect the greater lability of oxygenated species toward astrophysical processing. Laboratory studies show that O-bearing functional groups in organic compounds tend to be relatively easily removed by heating and/or UV and particle irradiation . In Halley's coma, O-containing organic grains, being unstable, were located closest to the nucleus. The decomposition of the organic grain <span class="hlt">component</span> in the coma provided a significant extended source contribution to O-containing gaseous species such as CO and H2CO.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22667483-assessment-models-galactic-thermal-dust-emission-using-cobe-firas-cobe-dirbe-observations','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22667483-assessment-models-galactic-thermal-dust-emission-using-cobe-firas-cobe-dirbe-observations"><span>ASSESSMENT OF MODELS OF GALACTIC THERMAL <span class="hlt">DUST</span> EMISSION USING COBE /FIRAS AND COBE /DIRBE OBSERVATIONS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Odegard, N.; Kogut, A.; Miller, N. J.</p> <p>2016-09-01</p> <p>Accurate modeling of the spectrum of thermal <span class="hlt">dust</span> emission at millimeter wavelengths is important for improving the accuracy of foreground subtraction for cosmic microwave background (CMB) measurements, for improving the accuracy with which the contributions of different foreground emission <span class="hlt">components</span> can be determined, and for improving our understanding of <span class="hlt">dust</span> composition and <span class="hlt">dust</span> physics. We fit four models of <span class="hlt">dust</span> emission to high Galactic latitude COBE /FIRAS and COBE /DIRBE observations from 3 mm to 100 μ m and compare the quality of the fits. We consider the two-level systems (TLS) model because it provides a physically motivated explanation formore » the observed long wavelength flattening of the <span class="hlt">dust</span> spectrum and the anti-correlation between emissivity index and <span class="hlt">dust</span> temperature. We consider the model of Finkbeiner et al. because it has been widely used for CMB studies, and the generalized version of this model that was recently applied to Planck data by Meisner and Finkbeiner. For comparison we have also fit a phenomenological model consisting of the sum of two graybody <span class="hlt">components</span>. We find that the two-graybody model gives the best fit and the FDS model gives a significantly poorer fit than the other models. The Meisner and Finkbeiner model and the TLS model remain viable for use in Galactic foreground subtraction, but the FIRAS data do not have a sufficient signal-to-noise ratio to provide a strong test of the predicted spectrum at millimeter wavelengths.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20170002740&hterms=thermal+noise&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dthermal%2Bnoise','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20170002740&hterms=thermal+noise&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dthermal%2Bnoise"><span>Assessment of Models of Galactic Thermal <span class="hlt">Dust</span> Emission Using COBE/FIRAS and COBE/DIRBE Observations</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Odegard, N.; Kogut, A.; Chuss, D. T.; Miller, N. J.</p> <p>2016-01-01</p> <p>Accurate modeling of the spectrum of thermal <span class="hlt">dust</span> emission at millimeter wavelengths is important for improving the accuracy of foreground subtraction for cosmic microwave background (CMB) measurements, for improving the accuracy with which the contributions of different foreground emission <span class="hlt">components</span> can be determined, and for improving our understanding of <span class="hlt">dust</span> composition and <span class="hlt">dust</span> physics. We fit four models of <span class="hlt">dust</span> emission to high Galactic latitude COBE/FIRAS and COBE/DIRBE observations from 3 mm to 100m and compare the quality of the fits. We consider the two-level systems (TLS) model because it provides a physically motivated explanation for the observed long wavelength flattening of the <span class="hlt">dust</span> spectrum and the anti-correlation between emissivity index and <span class="hlt">dust</span> temperature. We consider the model of Finkbeiner et al. because it has been widely used for CMB studies, and the generalized version of this model that was recently applied to Planck data by Meisner and Finkbeiner. For comparison we have also fit a phenomenological model consisting of the sum of two-graybody <span class="hlt">components</span>. We find that the two-graybody model gives the best fit and the FDS model gives a significantly poorer fit than the othermodels. The Meisner and Finkbeiner model and the TLS model remain viable for use in Galactic foreground subtraction, but the FIRAS data do not have a sufficient signal-to-noise ratio to provide a strong test of the predicted spectrum at millimeter wavelengths.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://eric.ed.gov/?q=global+AND+warming+AND+effects&pg=7&id=EJ391198','ERIC'); return false;" href="https://eric.ed.gov/?q=global+AND+warming+AND+effects&pg=7&id=EJ391198"><span>Global <span class="hlt">Warming</span>.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Hileman, Bette</p> <p>1989-01-01</p> <p>States the foundations of the theory of global <span class="hlt">warming</span>. Describes methodologies used to measure the changes in the atmosphere. Discusses steps currently being taken in the United States and the world to slow the <span class="hlt">warming</span> trend. Recognizes many sources for the <span class="hlt">warming</span> and the possible effects on the earth. (MVL)</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_25 --> <div class="footer-extlink text-muted" style="margin-bottom:1rem; text-align:center;">Some links on this page may take you to non-federal websites. Their policies may differ from this site.</div> </div><!-- container --> <footer><a id="backToTop" href="#top"> </a><nav><a id="backToTop" href="#top"> </a><ul class="links"><a id="backToTop" href="#top"> </a><li><a id="backToTop" href="#top"></a><a href="/sitemap.html">Site Map</a></li> <li><a href="/members/index.html">Members Only</a></li> <li><a href="/website-policies.html">Website Policies</a></li> <li><a href="https://doe.responsibledisclosure.com/hc/en-us" target="_blank">Vulnerability Disclosure Program</a></li> <li><a href="/contact.html">Contact Us</a></li> </ul> <div class="small">Science.gov is maintained by the U.S. Department of Energy's <a href="https://www.osti.gov/" target="_blank">Office of Scientific and Technical Information</a>, in partnership with <a href="https://www.cendi.gov/" target="_blank">CENDI</a>.</div> </nav> </footer> <script type="text/javascript"><!-- // var lastDiv = ""; function showDiv(divName) { // hide last div if (lastDiv) { document.getElementById(lastDiv).className = "hiddenDiv"; } //if value of the box is not nothing and an object with that name exists, then change the class if (divName && document.getElementById(divName)) { document.getElementById(divName).className = "visibleDiv"; lastDiv = divName; } } //--> </script> <script> /** * Function that tracks a click on an outbound link in Google Analytics. * This function takes a valid URL string as an argument, and uses that URL string * as the event label. */ var trackOutboundLink = function(url,collectionCode) { try { h = window.open(url); setTimeout(function() { ga('send', 'event', 'topic-page-click-through', collectionCode, url); }, 1000); } catch(err){} }; </script> <!-- Google Analytics --> <script> (function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){ (i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o), m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m) })(window,document,'script','//www.google-analytics.com/analytics.js','ga'); ga('create', 'UA-1122789-34', 'auto'); ga('send', 'pageview'); </script> <!-- End Google Analytics --> <script> showDiv('page_1') </script> </body> </html>