The brightest high-latitude 12-micron IRAS sources

NASA Technical Reports Server (NTRS)

Hacking, P.; Beichman, C.; Chester, T.; Neugebauer, G.; Emerson, J.

1985-01-01

The Infrared Astronomical Satellite (IRAS) Point Source catalog was searched for sources brighter than 28 Jy (0 mag) at 12 microns with absolute galactic latitude greater than 30 deg excluding the Large Magellanic Cloud. The search resulted in 269 sources, two of which are the galaxies NGC 1068 and M82. The remaining 267 sources are identified with, or have infrared color indices consistent with late-type stars some of which show evidence of circumstellar dust shells. Seven sources are previously uncataloged stars. K and M stars without circumstellar dust shells, M stars with circumstellar dust shells, and carbon stars occupy well-defined regions of infrared color-color diagrams.

Episodic Dust Emission from Alpha Orionis

NASA Astrophysics Data System (ADS)

Danchi, W. C.; Greenhill, L. J.; Bester, M.; Degiacomi, C.; Townes, C. H.

1993-05-01

The spatial distribution of dust surrounding alpha Orionis has been observed with the Infrared Spatial Interferometer (ISI) operating at a wavelength of 11.15 microns. Radiative transfer modeling of the visibility curves obtained by the ISI has yielded estimates of the physical parameters of the dust surrounding the star and new details of the dust distribution. The visibility curves taken in 1992 can be fitted best by a model with two dust shells. One shell has an inner radius of 1.0+/- 0.1{ }('') , a thickness between 50-200 milliarcsec, and a temperature of about 380 K. The second shell has an inner radius of 2.0+/-0.1{ }('') , a thickness less than about 200 milliarcsec, and a temperature of 265 K. These results are consistent with the recent spatially resolved spectroscopy of alpha Orionis reported by Sloan et al. (1993, Ap.J., 404, 303). The dust was modelled with the MRN size distribution with radius varying from 0.005--0.25 microns. The star was assumed to be a blackbody with a temperature of 3500 K and angular radius of 21.8 milliarcsec, consistent with recent interferometric determinations of its diameter (cf. Dyck et al., 1992, A.J., 104, 1992). For an adopted distance of 150 pc, the model for the 1992 data was evolved backward in time for a comparison with previous visibility data of Sutton (1979, Ph.D. Thesis, U.C. Berkeley) and Howell et al. (1981, Ap.J., 251, L21). The velocities, 11 km \\ s(-1) and 18 km \\ s(-1) , were used for the first and second shells respectively, which are the CO velocities measured by Bernat et al. (1979, Ap.J.,233, L135). We find excellent agreement if the dust shells were at approximately 0.80{ }('') and 1.67{ }('') at the epoch of the previous measurements. The data are consistent with the hypothesis that inner dust shell was emitted during the unusual variations in radial velocity and visual magnitude in the early 1940's, described by Goldberg (1984, PASP, 96, 366).

The Dust Ring of Luminous Blue Variable Candidate HD 168625: Infrared Observations and Model Calculations

NASA Astrophysics Data System (ADS)

O'Hara, Timothy B.; Meixner, Margaret; Speck, Angela K.; Ueta, Toshiya; Bobrowsky, Matthew

2003-12-01

We present a 2.218 μm image from the Hubble Space Telescope/Near Infrared Camera and Multi-Object Spectrometer (NICMOS) and a 55 μm image from ISOPHOT of the dust ring surrounding the luminous blue variable (LBV) candidate HD 168625, together with new temperature and optical depth maps derived from mid-IR images. The shell is detached from the star in the near-IR, and substructure in the overall toroidal shell is visible. The far-IR image constrains the extent of the dust shell to ~25" in diameter, providing an upper radius limit for modeling. The temperature maps and the NICMOS image show evidence for very small transiently heated dust grains in the shell. The opacity maps show higher optical depth in the limbs, consistent with interpretation of the dust shell as an equatorially enhanced torus inclined ~60° with respect to the observer. An overall trend in the dust emission location with wavelength is observed and interpreted as a variation with respect to location in the nebula of either the dust grain size distribution or gas-to-dust mass ratio. Radiative transfer calculations using 2-DUST indicate that a mass-loss event occurred ~5700 yr ago with a rate of (1.9+/-0.1)×10-4Msolaryr-1, creating a dust torus that currently has a τV~0.22 in the equatorial plane and a dust mass of (2.5+/-0.1)×10-3Msolar. Using published values for the gas mass, we find a gas-to-dust mass ratio of 840, which is ~4 times higher than current estimates for the interstellar medium. In addition to a high equator-to-pole density ratio (~31) torus, an elliptical midshell is needed to reproduce the appearance and spectral energy distribution of the dust. Therefore, HD 168625 is an excellent example of proposed models of LBV nebulae in which a stellar wind interacts with a preexisting density contrast and creates a blowout in the polar direction perpendicular to the equatorial ring. The circumstellar shell is much lower in mass than that of LBV η Carinae, suggesting that HD 168625 had a lower mass progenitor. Based in part on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555 these observations are associated with proposal 7898. Based also on observations with ISO, an ESA project with instruments funded by ESA member states (especially the PI countries: France, Germany, the Netherlands, and the United Kingdom) and with the participation of ISAS and NASA.

X-rays from Eta Carinae

NASA Technical Reports Server (NTRS)

Chlebowski, T.; Seward, F. D.; Swank, J.; Szymkowiak, A.

1984-01-01

X-ray observations of Eta Car obtained with the high-resolution imager and solid-state spectrometer of the Einstein observatory are reported and interpreted in terms of a two-shell model. A soft component with temperature 5 million K is located in the expanding outer shell, and the hard core component with temperature 80 million K is attributed to the interaction of a high-velocity stellar wind from the massive central object with the inner edge of a dust shell. Model calculations based on comparison with optical and IR data permit estimation of the mass of the outer shell (0.004 solar mass), the mass of the dust shell (3 solar mass), and the total shell expansion energy (less than 2 x 10 to the 49th ergs).

AGN radiative feedback in dusty quasar populations

NASA Astrophysics Data System (ADS)

Ishibashi, W.; Banerji, M.; Fabian, A. C.

2017-08-01

New populations of hyper-luminous, dust-obscured quasars have been recently discovered around the peak epoch of galaxy formation (z ˜ 2-3), in addition to similar sources found at lower redshifts. Such dusty quasars are often interpreted as sources 'in transition', from dust-enshrouded starbursts to unobscured luminous quasars, along the evolutionary sequence. Here we consider the role of the active galactic nucleus (AGN) radiative feedback, driven by radiation pressure on dust, in high-luminosity, dust-obscured sources. We analyse how the radiation pressure-driven dusty shell models, with different shell mass configurations, may be applied to the different populations of dusty quasars reported in recent observations. We find that expanding shells, sweeping up matter from the surrounding environment, may account for prolonged obscuration in dusty quasars, e.g. for a central luminosity of L ˜ 1047 erg s-1, a typical obscured phase (with extinction in the range AV ˜ 1-10 mag) may last a few ˜106 yr. On the other hand, fixed-mass shells, coupled with high dust-to-gas ratios, may explain the extreme outflows recently discovered in red quasars at high redshifts. We discuss how the interaction between AGN radiative feedback and the ambient medium at different temporal stages in the evolutionary sequence may contribute to shape the observational appearance of dusty quasar populations.

An Infrared Study of the Circumstellar Material Associated with the Carbon Star R Sculptoris

NASA Astrophysics Data System (ADS)

Hankins, M. J.; Herter, T. L.; Maercker, M.; Lau, R. M.; Sloan, G. C.

2018-01-01

The asymptotic giant branch (AGB) star R Sculptoris (R Scl) is one of the most extensively studied stars on the AGB. R Scl is a carbon star with a massive circumstellar shell (M shell ∼ 7.3 × 10‑3 M ⊙) that is thought to have been produced during a thermal pulse event ∼2200 years ago. To study the thermal dust emission associated with its circumstellar material, observations were taken with the Faint Object InfraRed CAMera for the SOFIA Telescope (FORCAST) at 19.7, 25.2, 31.5, 34.8, and 37.1 μm. Maps of the infrared emission at these wavelengths were used to study the morphology and temperature structure of the spatially extended dust emission. Using the radiative-transfer code DUSTY, and fitting the spatial profile of the emission, we find that a geometrically thin dust shell cannot reproduce the observed spatially resolved emission. Instead, a second dust component in addition to the shell is needed to reproduce the observed emission. This component, which lies interior to the dust shell, traces the circumstellar envelope of R Scl. It is best fit by a density profile with n ∝ r α , where α ={0.75}-0.25+0.45 and a dust mass of {M}d={9.0}-4.1+2.3× {10}-6 {M}ȯ . The strong departure from an r ‑2 law indicates that the mass-loss rate of R Scl has not been constant. This result is consistent with a slow decline in the post-pulse mass loss that has been inferred from observations of the molecular gas.

Guilt by Association: The 13 micron Dust Feature in Circumstellar Shells and Related Spectral Features

NASA Astrophysics Data System (ADS)

Sloan, G. C.; Kraemer, K. E.; Goebel, J. H.; Price, S. D.

A study of spectra from the SWS on ISO of optically thin oxygen-rich dust shells shows that the strength of the 13 micron dust emission feature is correlated with the CO2 bands (13--17 microns) and dust emission features at 19.8 and 28.1 microns. SRb variables tend to show stronger 13 micron features than Mira variables, suggesting that the presence of the 13 micron and related features depends on pulsation mode and mass-loss rate. The absence of any correlation to dust emission features at 16.8 and 32 microns makes spinel an unlikely carrier. The most plausible carrier of the 13 micron feature remains crystalline alumina, and we suggest that the related dust features may be crystalline silicates. When dust forms in regions of low density, it may condense into crystalline grain structures.

Dust around Mira variables: An analysis of IRAS LRS spectra

NASA Technical Reports Server (NTRS)

Slijkhuis, S.

1989-01-01

The spatial extent and spectral appearance of the thin dust shell around Mira variables is determined largely by the dust absorptivity, Q(sub abs)(lambda), and the dust condensation temperature T(sub cond). Both Q(sub abs)(lambda) and T(sub cond) are extracted from IRAS low-resolution spectra (LRS) spectra. In order to do this, the assumption that the ratio of total power in the 10 micron feature to that in the 20 micron feature should be equal to that measured in other amorphous silicates (e.g., synthesized amorphous Mg2SiO4). It was found that T(sub cond) decreases with decreasing strength of the 10 micron feature, from T(sub cond) = 1000 K to 500 K (estimated error 20 percent). A value for the near-infrared dust absorptivity could not be determined. Although this parameter strongly affects the condensation radius, it hardly affects the shape of the LRS spectrum (as long as the optically thin approximation is valid), because it scales the spatial distribution of the dust. Information on the magnitude of the near-infrared dust absorptivity may be deduced from the unique carbon star BM Gem. This star has a LRS spectrum with silicate features indication an inner dust shell temperature of at least 1000 K. However, on the basis of observations in the 1920s-30s one may infer an inner dust shell radius of at least 6x10(exp 12)m. To have this high temperature at such a large distance, the near-infrared absorptivity of the dust must be high.

Health-hazard evaluation report HETA 91-298-2182, Gibson Flatiron, Erica Shell Manufacturing, Bozeman, Montana

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

McCammon, C.S.

1992-02-01

In response to a request from the Montana State Health Department, an evaluation was undertaken of exposures to wood dust and lacquer vapors at the Gibson Flatiron/Erica Shell Manufacturing Companies (SIC-3931), Bozeman, Montana. Gibson Flatiron manufactured mandolins and banjoes. Erica Shell Manufacturing Company cuts and grinds abalone and other sea shells into small pieces to be used in designs inlayed into mandolins and banjos. Measured wood dust levels ranged from 0.8 to 32mg/cu m with an 8 hour time weighted average (TWA) of 1.2 to 30mg/cu m. Rib construction and assembly, and planing bulk ebony wood had TWA exposures abovemore » the OSHA permissible exposure limit of 5mg/cu m for wood dust. Application of dyes and finishes resulted in low exposures to acetone (67641), toluene (108883), xylene (1330207), and butyl-acetate (123864). No solvent air concentrations were above 10% of their respective PELs. The author concludes that a health hazard existed for exposure to wood dusts. The author recommends the establishment of a respiratory protection program and a hearing conservation program. Emergency egress routes should be marked in the buildings.« less

Induced nucleation of carbon dust in red giant stars

NASA Technical Reports Server (NTRS)

Cadwell, Brian J.; Wang, Hai; Feigelson, Eric D.; Frenklach, Michael

1994-01-01

This study quantitatively tests the proposed model of induced nucleation of carbonaceous grains in carbon-rich red giant stars. Induced nucleation is the process of grain growth initiated by the presence of reactive surfaces provided by seed particles. The numerical study was performed using a deailed chemical kinetic model of carbon deposition, grain coagulation, and homogeneous nucleation of polycyclic aromatic hydrocarbons (PAHs). The model uses a method of moments to keep track of developing grain population in the forming dust shell. We test the efficiency of grain formation for large ranges of dust shell parameters typical for carbon stars. Our model is capable of producing a range of optically thick and thin dust shells in carbon stars. Results are in accord with (IRAS) spectral classes of carbon stars. The resulting composite grains produced are consistent with those recently found in ancient meteorites. This model also provides a realistic explanation for high abundances of (PAHs) in the interstellar medium and some planetary nebulae.

7 CFR 51.2126 - Particles and dust.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 7 Agriculture 2 2010-01-01 2010-01-01 false Particles and dust. 51.2126 Section 51.2126... STANDARDS) United States Standards for Grades of Shelled Almonds Definitions § 51.2126 Particles and dust. Particles and dust means fragments of almond kernels or other material which will pass through a round...

7 CFR 51.1443 - Particles and dust.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 7 Agriculture 2 2011-01-01 2011-01-01 false Particles and dust. 51.1443 Section 51.1443... STANDARDS) United States Standards for Grades of Shelled Pecans Definitions § 51.1443 Particles and dust. Particles and dust means, for all size designations except “midget pieces” and “granules,” fragments of...

7 CFR 51.2126 - Particles and dust.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 7 Agriculture 2 2011-01-01 2011-01-01 false Particles and dust. 51.2126 Section 51.2126... STANDARDS) United States Standards for Grades of Shelled Almonds Definitions § 51.2126 Particles and dust. Particles and dust means fragments of almond kernels or other material which will pass through a round...

7 CFR 51.1443 - Particles and dust.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 7 Agriculture 2 2012-01-01 2012-01-01 false Particles and dust. 51.1443 Section 51.1443... STANDARDS) United States Standards for Grades of Shelled Pecans Definitions § 51.1443 Particles and dust. Particles and dust means, for all size designations except “midget pieces” and “granules,” fragments of...

7 CFR 51.1443 - Particles and dust.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 7 Agriculture 2 2010-01-01 2010-01-01 false Particles and dust. 51.1443 Section 51.1443... STANDARDS) United States Standards for Grades of Shelled Pecans Definitions § 51.1443 Particles and dust. Particles and dust means, for all size designations except “midget pieces” and “granules,” fragments of...

7 CFR 51.2126 - Particles and dust.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 7 Agriculture 2 2012-01-01 2012-01-01 false Particles and dust. 51.2126 Section 51.2126... STANDARDS) United States Standards for Grades of Shelled Almonds Definitions § 51.2126 Particles and dust. Particles and dust means fragments of almond kernels or other material which will pass through a round...

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 density and filling factors of the clumpy medium swept up by the SNR.

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 quantitative estimates of density and filling factors of the clumpy medium swept up by the SNR.

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 estimates of density and filling factors of the clumpy medium swept up by the SNR.

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 filling factors of the clumpy medium swept up by the SNR.

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

Tinyanont, Samaporn; Kasliwal, Mansi M.; Lau, Ryan

We present a systematic study of mid-infrared emission from 141 nearby supernovae (SNe) observed with Spitzer /IRAC as part of the ongoing SPIRITS survey. We detect 8 Type Ia and 36 core-collapse SNe. All Type Ia/Ibc SNe become undetectable within three years of explosion, whereas 22 ± 11% of Type II SNe continue to be detected. Five Type II SNe are detected even two decades after discovery (SN 1974E, 1979C, 1980K, 1986J, and 1993J). Warm dust luminosity, temperature, and a lower limit on mass are obtained by fitting the two IRAC bands, assuming an optically thin dust shell. We derive warm dust masses between 10{sup −6} and 10{sup −2}more » M {sub ⊙} and dust color temperatures between 200 and 1280 K. This observed warm dust could be pre-existing or newly created, but in either case represents a lower limit to the dust mass because cooler dust may be present. We present three case studies of extreme SNe. SN 2011ja (II-P) was over-luminous ([4.5] = −15.6 mag) at 900 days post explosion with increasing hot dust mass, suggesting either an episode of dust formation or intensifying circumstellar material (CSM) interactions heating up pre-existing dust. SN 2014bi (II-P) showed a factor of 10 decrease in dust mass over one month, suggesting either dust destruction or reduced dust heating. The IR luminosity of SN 2014C (Ib) stayed constant over 800 days, possibly due to strong CSM interaction with an H-rich shell, which is rare among stripped-envelope SNe. The observations suggest that this CSM shell originated from an LBV-like eruption roughly 100 years pre-explosion. The observed diversity demonstrates the power of mid-IR observations of a large sample of SNe.« less

Constraining the Post-Thermal Pulse Mass-Loss History of R Scl with SOFIA/FORCAST

NASA Astrophysics Data System (ADS)

Hankins, Matthew; Herter, Terry; maercker, matthias; Lau, Ryan M.; Sloan, Greg

2018-06-01

R Sculptoris (R Scl) is a nearby (~370 pc) carbon star with a massive circumstellar shell (Mshell∼7×10‑3 M⊙) which is thought to have been produced by a thermal pulse event ∼2200 years ago. We observed R Scl with the Faint Object InfraRed CAMera for the SOFIA Telescope (FORCAST) at 19.7, 25.2, 31.5, 34.8, and 37.1 μm to study its circumstellar dust emission. Maps of the infrared emission were used to examine the morphology and temperature structure of the spatially extended dust emission. We used the radiative transfer code DUSTY to fit the radial density profile of the circumstellar material, and find that a geometrically thin dust shell cannot reproduce the observed emission. Instead, a second dust component is needed to model the emission. This component, which lies interior to the dust shell, traces the post-thermal pulse mass loss of R Scl and is indicative of a slow decline in the star’s mass loss over thousands of years. This result is at odds with 'classical' thermal pulse models but is consistent with earlier observations of molecular gas in R Scl’s circumstellar environment.

IRAS observations of a large circumstellar dust shell around W Hydrae

NASA Technical Reports Server (NTRS)

Hawkins, G. W.

1990-01-01

IRAS observations at 60 and 100 microns reveal a large 30-40-arcmin (about 1-pc) diameter dust shell centered on the oxygen-rich red giant W Hya. Except for SNRs, this is the largest mass-loss envelope, in apparent diameter, known around any evolved star, including PN. W Hya's radiation field, stronger than the interstellar radiation field in the outer envelope, is sufficient to heat dust grains with IR emissivity proportional to lambda exp -1.2 to temperatures of about 40 K implied by the ratio of intensities at 60 and 100 microns.

Quantum collapse of dust shells in 2 + 1 gravity

NASA Astrophysics Data System (ADS)

Ortíz, L.; Ryan, M. P.

2007-08-01

This paper considers the quantum collapse of infinitesimally thin dust shells in 2 + 1 gravity. In 2 + 1 gravity a shell is no longer a sphere, but a ring of matter. The classical equation of motion of such shells in terms of variables defined on the shell has been considered by Peleg and Steif (Phys Rev D 51:3992, 1995), using the 2 + 1 version of the original formulation of Israel (Nuovo Cimento B 44:1, 1966), and Crisóstomo and Olea (Phys Rev D 69:104023, 2004), using canonical methods. The minisuperspace quantum problem can be reduced to that of a harmonic oscillator in terms of the curvature radius of the shell, which allows us to use well-known methods to find the motion of coherent wave packets that give the quantum collapse of the shell. Classically, as the radius of the shell falls below a certain point, a horizon forms. In the quantum problem one can define various quantities that give “indications” of horizon formation. Without a proper definition of a “horizon” in quantum gravity, these can be nothing but indications.

Modeling of the Dust and Gas Outflows from OH 26.5+0.6: The Superwind

NASA Technical Reports Server (NTRS)

Justtanont, K.; Skinner, C. J.; Tielens, A. G. G. M.; Meixner, M.; Baas, F.

1996-01-01

We have observed the extreme OH/IR star, OH 26.5+0.6, in the infrared dust continuum and in the sub- millimeter rotational lines of CO. Mid-infrared images reveal the compact nature of the circumstellar shell (less than 0.5 sec). A deep 9.7 microns absorption feature and an absorption at 18 microns show that the dust mass-loss rate is very high. However, the low antenna temperatures of CO J = 1-0 and 2-1 lines suggest that the outer part of the circumstellar shell is much more tenuous. In order to resolve this discrepancy, we have observed the J = 3-2 and 4-3 CO rotational transitions. We have developed a model for the circumstellar shell for OH 26.5 + 0.6 which is consistent with the infrared and submillimeter observations. The dust and gas data are well fitted by a two-shell model, consisting of a dense shell surrounded by a more tenuous shell. The former we identify with the superwind (M = 5.5 x 10(exp -4) solar mass/ yr), and the latter we identify with mass loss on the asymptotic giant branch (AGB) (M = 10(exp -6) solar mass/ yr). The transition between the two mass-loss phases is shown to be rather abrupt ((Delta)t less than 150 yr). Depending on the mass of the progenitor, this superwind phase may be the last thermal pulse (for M(sub *) less than 1.5 solar mass), or the first of a series of the superwind phases (for up to 8 solar mass), punctuated by a period of low mass-loss rates, before the star evolves off the AGB.

Pathologies of van Stockum dust/Tipler's time machine

NASA Astrophysics Data System (ADS)

Lindsay, David S.

2016-09-01

We study the internal solution, and external vacuum solution for radial cutoff, of "van Stockum dust", an infinitely long rotating pressureless dust column; its density increases with radius. This interesting but poorly explored spacetime turns out to have a number of exotic properties, especially in the external vacuum region. These solutions have been known for decades, but it seems that they have never been investigated in detail. In this paper we analyze them and describe their peculiar properties. There are three regimes of radial cutoff that are of interest: (1) If the dust column is thick enough that closed timelike loops (CTLs or "time machines") exist inside the column, then the radius of the entire "universe" is finite, and in fact does not extend much beyond the edge of the matter, even though the metric's radial parameter is unbounded. This interesting finite proper radius seems to have been missed by earlier investigators. Other exotic properties of the external vacuum in this regime: CTLs exist in cylindrical shells, alternating with shells having no circular CTLs; there are infinitely many such shells, getting closer and closer together as one gets farther from the rotation axis. Also, a separate set of infinitely many cylindrical shells exists, having what might be termed "extreme frame-dragging", within which motion is possible only in one direction; they alternate with "normal" shells allowing motion in either direction. Gravitational attraction and tides increase with distance from the matter column, and diverge at the "edge of the universe". In addition, though the radius of the universe is finite, its circumference is infinite; and its boundary is a circle, not a cylinder (the z-axis has shrunk to nothing at the edge). (2) For smaller radial cutoff, but still large enough to produce CTLs, the radius of the universe is infinite; but there are still infinitely many cylindrical shells of CTLs alternating with non-CTL shells. However, the innermost shell begins substantially outside the dust, making this solution even stranger—you have to back away from the matter to find a CTL! And, regardless of how far away you are, there are still infinitely many CTL shells beyond you, the closest only a finite distance away. (3) For radial cutoff too close to produce CTLs, the external solution is more benign; nearby it perhaps approximates that of a finite rotating rod. But "planes" of constant z approach each other at large radii, so that any two enclose a shape somewhat like two pie-pans facing each other and glued together at their edges.

Debris Disks Among the Shell Stars: Insights from Spitzer

NASA Technical Reports Server (NTRS)

Roberge, Aki; Weinberger, Alycia; Teske, Johanna

2008-01-01

Shell stars are a class of early-type stars that show narrow absorption lines in their spectra that appear to arise from circumstellar class. This observationally defined class contains a variety of objects, including evolved stars and classical Be stars. However, some of the main sequence shell stars harbor debris disks and younger protoplanetary disks, though this aspect of the class has been largely overlooked. We surveyed a set of main sequence stars for cool dust using Spitzer MIPS and found four additional systems with IR excesses at both 24 and 70 microns. This indicates that the stars have both circumstellar gas and dust, and are likely to be edge-on debris disks. Our estimate of the disk fraction among nearby main sequence shell stars is 48% +/- 14%. We discuss here the nature of the shell stars and present preliminary results from ground-based optical spectra of the survey target stars. We will also outline our planned studies aimed at further characterization of the shell star class.

Numerical investigation of the coagulation mixing between dust and hygroscopic aerosol particles and its impacts

NASA Astrophysics Data System (ADS)

Tsai, I.-Chun; Chen, Jen-Ping; Lin, Yi-Chiu; Chung-Kuang Chou, Charles; Chen, Wei-Nai

2015-05-01

A statistical-numerical aerosol parameterization was incorporated into the Community Multiscale Air Quality modeling system to study the coagulation mixing process focusing on a dust storm event that occurred over East Asia. Simulation results show that the coagulation mixing process tends to decrease aerosol mass, surface area, and number concentrations over the dust source areas. Over the downwind oceanic areas, aerosol concentrations generally increased due to enhanced sedimentation as particles became larger upon coagulation. The mixture process can reduce the overall single-scattering albedo by up to 10% as a result of enhanced core with shell absorption by dust and reduction in the number of scattering particles. The enhanced dry deposition speed also altered the vertical distribution. In addition, the ability of aerosol particles to serve as cloud condensation nuclei (CCN) increased from around 107 m-3 to above 109 m-3 over downwind areas because a large amount of mineral dust particles became effective CCN with solute coating, except over the highly polluted areas where multiple collections of hygroscopic particles by dust in effect reduced CCN number. This CCN effect is much stronger for coagulation mixing than by the uptake of sulfuric acid gas on dust, although the nitric acid gas uptake was not investigated. The ability of dust particles to serve as ice nuclei may decrease or increase at low or high subzero temperatures, respectively, due to the switching from deposition nucleation to immersion freezing or haze freezing.

Ir Observations Of An Outburst In Comet Hale-Bopp (C/1995 O1)

NASA Astrophysics Data System (ADS)

Tozzi, Gian Paolo; Mannucci, Filippo; Stanga, Ruggero

1997-07-01

The comet Hale-Bopp (C/1995 O1) has been observed in the infrared (1 2.5 μm) with the Nordic Optical Telescope (NOT) equipped with the Arcetri NICMOS3 camera (ARNICA). Two observational campaigns, each one lasting about one week, were made when the comet heliocentric distance was about 3 AU. The first campaign was at the end of August and the second at the end of September 1996. During both runs two major outbursts were observed, the more intense of them started the day before the beginning of the second run. In the images recorded during the first three nights (24.8 26.8 Sept.) of the second run a dust shell expanding in the northern quadrant with a projected velocity of 0.14 0.28 km/s is clearly evident. The dust production rate increased by at least a factor ≈3 at the time of the outburst. Also evident on the first night is a change in the IR color that is well correlated with the dust shell. This is an indication that the material released by the outburst has a different composition and/or size distribution than that in the “quiescent” dust coma. In this paper we present preliminary results about the evolution and the photometric characteristics of the dust shell.

Detached dust shell around Wolf-Rayet star WR60-6 in the young stellar cluster VVV CL036

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

Borissova, J.; Amigo, P.; Kurtev, R.

The discovery of a detached dust shell around the Wolf-Rayet (WR) star WR60-6 in the young stellar cluster VVV CL036 is reported. This shell is uncovered through the Spitzer-MIPS 24 μm image, where it appears brightest, and it is invisible at shorter wavelengths. Using new APEX observations and other data available from the literature, we have estimated some of the shell parameters: the inner and outer radii of 0.15 and 0.90 pc, respectively; the overall systemic velocity of the molecular {sup 12}CO(3 → 2) emission of –45.7 ± 2.3 km s{sup –1}; an expansion velocity of the gas of 16.3more » ± 1 km s{sup –1}; the dust temperature and opacity of 122 ± 12 K and 1.04, respectively; and an age of 2.8 × 10{sup 4} yr. The WR star displays some cyclic variability. The mass computed for the WR60-6 nebula indicates that the material was probably ejected during its previous stages of evolution. In addition, we have identified a bright spot very close to the shell, which can be associated with the Midcourse Space Experiment source G312.13+00.20.« less

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

Fossil dust shells around luminous supergiants

NASA Technical Reports Server (NTRS)

Stothers, R.

1975-01-01

The observed frequency with which infrared excesses appear in F, G, and K supergiants of luminosity class Ia supports the idea that these excesses arise in a 'fossil' circumstellar dust shell that was formed during a prior M-super-giant phase of evolution. The required leftward evolution of the star on the H-R diagram would then imply that the Ledoux, rather than the Schwarzschild, criterion for convective mixing is the correct criterion to use in stellar evolution calculations.

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.

Astrophysical dust grains in stars, the interstellar medium, and the solar system

NASA Technical Reports Server (NTRS)

Gehrz, Robert D.

1991-01-01

Studies of astrophysical dust grains in circumstellar shells, the interstellar medium, and the solar system may provide information about stellar evolution and about physical conditions in the primitive solar nebula. The following subject areas are covered: (1) the cycling of dust in stellar evolution and the formation of planetary systems; (2) astrophysical dust grains in circumstellar environments; (3) circumstellar grain formation and mass loss; (4) interstellar dust grains; (5) comet dust and the zodiacal cloud; (6) the survival of dust grains during stellar evolution; and (7) establishing connections between stardust and dust in the solar system.

7 CFR 51.1437 - Size classifications for halves.

Code of Federal Regulations, 2010 CFR

2010-01-01

... weight of half-kernels after all pieces, particles and dust, shell, center wall, and foreign material..., particles, and dust. In order to allow for variations incident to proper sizing and handling, not more than 15 percent, by weight, of any lot may consist of pieces, particles, and dust: Provided, That not more...

7 CFR 51.1437 - Size classifications for halves.

Code of Federal Regulations, 2012 CFR

2012-01-01

... weight of half-kernels after all pieces, particles and dust, shell, center wall, and foreign material..., particles, and dust. In order to allow for variations incident to proper sizing and handling, not more than 15 percent, by weight, of any lot may consist of pieces, particles, and dust: Provided, That not more...

7 CFR 51.1437 - Size classifications for halves.

Code of Federal Regulations, 2011 CFR

2011-01-01

... weight of half-kernels after all pieces, particles and dust, shell, center wall, and foreign material..., particles, and dust. In order to allow for variations incident to proper sizing and handling, not more than 15 percent, by weight, of any lot may consist of pieces, particles, and dust: Provided, That not more...

Experimental study on the strength parameter of Quarry Dust mixed Coconut Shell Concrete adding Coconut Fibre

NASA Astrophysics Data System (ADS)

Matangulu Shrestha, Victor; Anandh, S.; Sindhu Nachiar, S.

2017-07-01

Concrete is a heterogeneous mixture constitute of cement as the main ingredient with a different mix of fine and coarse aggregate. The massive use of conventional concrete has a shortfall in its key ingredients, natural sand and coarse aggregate, due to increased industrialisation and globalisation. To overcome the shortage of material, an alternate material with similar mechanical properties and composition has to be studied, as replacement of conventional concrete. Coconut shell concrete is a prime option as replacement of key ingredients of conventional concrete as coconut is produced in massive quantity in south East Asia. Coconut shell concrete is lightweight concrete and different research is still ongoing concerning about its mix design and composition in the construction industry. Concrete is weak in tension as compared to compression, hence the fibre is used to refrain the crack in the concrete. Coconut fibre is one of many fibres which can be used in concrete. The main aim of this project is to analyse the use of natural by-products in the construction industry, make light weight concrete and eco-friendly construction. This project concerns with the comparison of the mechanical properties of coconut shell concrete and conventional concrete, replacing fine aggregate with quarry dust using coconut fibre. M25 grade of concrete was adopted and testing of concrete was done at the age of 3, 7 and 28 days. In this concrete mix, sand was replaced completely in volumetric measurement by quarry dust. The result was analysed and compared with addition of coconut fibre at varying percentage of 1%, 2%, 3%, 4% and 5%. From the test conducted, coconut shell concrete with quarry dust has the maximum value at 4% of coconut fibre while conventional concrete showed the maximum value at 2% of coconut fibre.

THE CIRCUMSTELLAR ENVIRONMENT OF R CORONAE BOREALIS: WHITE DWARF MERGER OR FINAL-HELIUM-SHELL FLASH?

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

Clayton, Geoffrey C.; Andrews, J. E.; Sugerman, Ben E. K.

2011-12-10

In 2007, R Coronae Borealis (R CrB) went into a historically deep and long decline. In this state, the dust acts like a natural coronagraph at visible wavelengths, allowing faint nebulosity around the star to be seen. Imaging has been obtained from 0.5 to 500 {mu}m with Gemini/GMOS, Hubble Space Telescope/WFPC2, Spitzer/MIPS, and Herschel/SPIRE. Several of the structures around R CrB are cometary globules caused by wind from the star streaming past dense blobs. The estimated dust mass of the knots is consistent with their being responsible for the R CrB declines if they form along the line of sightmore » to the star. In addition, there is a large diffuse shell extending up to 4 pc away from the star containing cool 25 K dust that is detected all the way out to 500 {mu}m. The spectral energy distribution of R CrB can be well fitted by a 150 AU disk surrounded by a very large diffuse envelope which corresponds to the size of the observed nebulosity. The total masses of the disk and envelope are 10{sup -4} and 2 M{sub Sun }, respectively, assuming a gas-to-dust ratio of 100. The evidence pointing toward a white dwarf merger or a final-helium-shell flash origin for R CrB is contradictory. The shell and the cometary knots are consistent with a fossil planetary nebula. Along with the fact that R CrB shows significant lithium in its atmosphere, this supports the final-helium-shell flash. However, the relatively high inferred mass of R CrB and its high fluorine abundance support a white dwarf merger.« less

Infrared photometry of Nova Delphini 2013 (=V339 Del) in the first sixty days after its outburst

NASA Astrophysics Data System (ADS)

Taranova, O. G.; Tatarnikov, A. M.; Shenavrin, V. I.; Tatarnikova, A. A.

2014-02-01

The results of JHKLM photometry for Nova Delphini 2013 obtained in the first sixty days after its outburst are analyzed. Analysis of the energy distribution in a wide spectral range (0.36-5 µm) has shown that the source mimics the emission of normal supergiants of spectral types B5 and A0 for two dates near its optical brightness maximum, August 15.94 UT and August 16.86 UT, respectively. The distance to the nova has been estimated to be D ≈ 3 kpc. For these dates, the following parameters have been estimated: the source's bolometric fluxes ˜9 × 10-7 and ˜7.2 × 10-7 erg s-1 cm-2, luminosities L ≈ 2.5 × 105 L ⊙ and ≈2 × 105 L ⊙, and radii R ≈ 6.3 × 1012 and ≈1.2 × 1013 cm. The nova's expansion velocity near its optical brightness maximum was ˜700 km s-1. An infrared (IR) excess associated with the formation of a dust shell is shown to have appeared in the energy distribution one month after the optical brightness maximum. The parameters of the dust component have been estimated for two dates of observations, JD2456557.28 (September 21, 2013) and JD2456577.18 (October 11, 2013). For these dates, the dust shell parameters have been estimated: the color temperatures ≈1500 and ≈1200 K, radii ≈6.5 × 1013 and 1.7 × 1014 cm, luminosities ˜4 × 103 L ⊙ and ˜1.1 × 104 L ⊙, and the dust mass ˜1.6 × 1024 and ˜1025 g. The total mass of the material ejected in twenty days (gas + dust) could reach ˜1.1 × 10-6 M ⊙. The rate of dust supply to the nova shell was ˜8 × 10-8 M ⊙ yr-1. The expansion velocity of the dust shell was about 600 km s-1.

IRAS observations of R Coronae Borealis - Detection and study of a fossil shell

NASA Technical Reports Server (NTRS)

Gillett, F. C.; Backman, D. E.; Beichman, C.; Neugebauer, G.

1986-01-01

IRAS observations of the extreme hydrogen-deficient supergiant R CrB are presented and discussed. The star is surrounded by an enormous cool dust cloud which is tentatively identified as a fossil remnant of the hydrogen-rich envelope of the star. The angular extent of the emission corresponds to a linear extent of 8 pc, 20 times larger than the largest previously known shell around a late-type star. The radiating material is distributed very symmetrically over a wide range of radial distances from the star. The dust temperature is nearly constant throughout the extended shell. The total mass in the shell is about 0.3 solar mass. The ejection process appears to have occurred in a spherically symmetric fashion with a nearly constant mass loss rate and expansion velocity over a period of about 150,000 yr, terminating about 26,000 yr ago.

Silicosis Caused by Chronic Inhalation of Snail Shell Powder

PubMed Central

Jung, Jae Woo; Lee, Byung Ook; Lee, Jae Hee; Park, Sung Woon; Kim, Bo Min; Choi, Jae Chol; Shin, Jong Wook; Park, In Won; Choi, Byoung Whui

2012-01-01

A 70-yr-old woman visited our hospital for shortness of breath. Chest CT showed ground glass opacity and traction bronchiectasis at right middle, lower lobe and left lingular division. Video-assisted thoracic surgical biopsy at right lower lobe and pathologic examination revealed mixed dust pneumoconiosis. Polarized optical microscopy showed lung lesions were consisted of silica and carbon materials. She was a housewife and never been exposed to silica dusts occupationally. She has taken freshwater snails as a health-promoting food for 40 yr and ground shell powder was piled up on her backyard where she spent day-time. Energy dispersive X-ray spectroscopy of snail shell and scanning electron microscopy with energy dispersive x-ray spectroscopy of lung lesion revealed that silica occupies important portion. Herein, we report the first known case of silicosis due to chronic inhalation of shell powder of freshwater snail. PMID:22219621

The Last Gasps of VY Canis Majoris: Aperture Synthesis and Adaptive Optics Imagery

NASA Astrophysics Data System (ADS)

Monnier, J. D.; Tuthill, P. G.; Lopez, B.; Cruzalebes, P.; Danchi, W. C.; Haniff, C. A.

1999-02-01

We present new observations of the red supergiant VY CMa at 1.25, 1.65, 2.26, 3.08, and 4.8 μm. Two complementary observational techniques were utilized: nonredundant aperture masking on the 10 m Keck I telescope, yielding images of the innermost regions at unprecedented resolution, and adaptive optics imaging on the ESO 3.6 m telescope at La Silla, attaining an extremely high (~105) peak-to-noise dynamic range over a wide field. For the first time the inner dust shell has been resolved in the near-infrared to reveal a one-sided extension of circumstellar emission within 0.1" (~15 R*) of the star. The line-of-sight optical depths of the circumstellar dust shell at 1.65, 2.26, and 3.08 μm have been estimated to be 1.86+/-0.42, 0.85+/-0.20, and 0.44+/-0.11, respectively. These new results allow the bolometric luminosity of VY CMa to be estimated independent of the dust shell geometry, yielding L*~2×105 Lsolar. A variety of dust condensations, including a large scattering plume and a bow-shaped dust feature, were observed in the faint, extended nebula up to 4" from the central source. While the origin of the nebulous plume remains uncertain, a geometrical model is developed assuming the plume is produced by radially driven dust grains forming at a rotating flow insertion point with a rotational period between 1200 and 4200 yr, which is perhaps the stellar rotational period or the orbital period of an unseen companion.

Discovery and Analysis of 21 micrometer Feature Sources in the Magellanic Clouds (Postprint)

DTIC Science & Technology

2011-07-10

either definitely or may show the 21 μm feature have distinct dust shell properties compared to the Galactic 21 μm objects—the 21 μm features are weaker...13 objects that either definitely or may show the 21μm feature have distinct dust shell properties compared to the Galactic 21μm objects—the 21μm...SMC object J004441 than it is to the spectra of any of the other LMC objects. The optical counterpart, while definitely detected in the MCPS (V ∼ 18.4

High-resolution speckle masking interferometry and radiative transfer modeling of the oxygen-rich AGB star AFGL 2290

NASA Astrophysics Data System (ADS)

Gauger, A.; Balega, Y. Y.; Irrgang, P.; Osterbart, R.; Weigelt, G.

1999-06-01

We present the first diffraction-limited speckle masking observations of the oxygen-rich AGB star AFGL 2290. The speckle interferograms were recorded with the Russian 6 m SAO telescope. At the wavelength 2.11 microns a resolution of 75 milli-arcsec (mas) was obtained. The reconstructed diffraction-limited image reveals that the circumstellar dust shell (CDS) of AFGL 2290 is at least slightly non-spherical. The visibility function shows that the stellar contribution to the total 2.11 microns flux is less than ~ 40%, indicating a rather large optical depth of the circumstellar dust shell. The 2-dimensional Gaussian visibility fit yields a diameter of AFGL 2290 at 2.11 microns of 43 masx51 mas, which corresponds to a diameter of 42 AUx50 AU for an adopted distance of 0.98 kpc. Our new observational results provide additional constraints on the CDS of AFGL 2290, which supplement the information from the spectral energy distribution (SED). To determine the structure and the properties of the CDS we have performed radiative transfer calculations for spherically symmetric dust shell models. The observed SED approximately at phase 0.2 can be well reproduced at all wavelengths by a model with T_eff=2000 K, a dust temperature of 800 K at the inner boundary r1, an optical depth tau_ {V}=100 and a radius for the single-sized grains of a_gr=0.1 microns . However, the 2.11 microns visibility of the model does not match the observation. Exploring the parameter space, we found that grain size is the key parameter in achieving a fit of the observed visibility while retaining the match of the SED, at least partially. Both the slope and the curvature of the visibility strongly constrain the possible grain radii. On the other hand, the SED at longer wavelengths, the silicate feature in particular, determines the dust mass loss rate and, thereby, restricts the possible optical depths of the model. With a larger grain size of 0.16 microns and a higher tau_ {V}=150, the observed visibility can be reproduced preserving the match of the SED at longer wavelengths. Nevertheless, the model shows a deficiency of flux at short wavelengths, which is attributed to the model assumption of a spherically symmetric dust distribution, whereas the actual structure of the CDS around AFGL 2290 is in fact non-spherical. Our study demonstrates the possible limitations of dust shell models which are constrained solely by the spectral energy distribution, and emphasizes the importance of high spatial resolution observations for the determination of the structure and the properties of circumstellar dust shells around evolved stars. Based on data collected at the 6~m telescope of the Special Astrophysical Observatory in Russia

A Mid-IR Census of Dusty Supernovae From the Past Decade In Preparation for JWST

NASA Astrophysics Data System (ADS)

Fox, Ori; Andrews, Jennifer; Arendt, Rick; Clayton, Geoff; Dwek, Eli; Filippenko, Alex; Johansson, Joel; Kelly, Patrick; Krafton, Kelsie; Marston, Tony; Mauerhan, Jon; Szalai, Tamas; Van Dyk, Schuyler

2018-05-01

Over the past decade, our team has shown that a surprising number of different supernova (SN) subclasses have members that exhibit mid-infrared (mid-IR) emission from warm dust at late times (>100 days post-explosion). This work has used Spitzer 3.6 and 4.5 micron imaging to constrain the dust origin and heating mechanisms, but a number of questions still remain. How much dust can SNe IIP produce in their ejecta? What progenitor can produce such extreme mass-loss events required to form the large, dense, pre-existing dust shells observed in so many cases? Many of these SNe remain bright today, in some cases more than a decade after discovery. Continued mid-IR monitoring is necessary to answer these questions by measuring the full extent of either the newly formed dust mass or pre-existing dust shell. Furthermore, Spitzer observations of both old and new SNe will provide up to date flux estimates as we prepare for continued observations with JWST. This proposal will cap off nearly a decade of work and bridge the gap to the first few cycles of JWST.

Suzaku Observation of Diffuse X-ray Emission from the Carina Nebula

NASA Technical Reports Server (NTRS)

Hamaguchi, Kenji; Petre, Robert; Matsumoti, Hironori; Tsujimoto, Masahiro; Holt, Stephan S.; Ezoe, Yuichiro; Ozawa, Hideki; Tsuboi, Yohko; Soong, Yang; Kitamoto, Shunji;

INFRARED TWO-COLOR DIAGRAMS FOR AGB STARS, POST-AGB STARS, AND PLANETARY NEBULAE

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

Suh, Kyung-Won, E-mail: kwsuh@chungbuk.ac.kr

2015-08-01

We present various infrared two-color diagrams (2CDs) for asymptotic giant branch (AGB) stars, post-AGB stars, and Planetary Nebulae (PNe) and investigate possible evolutionary tracks. We use catalogs from the available literature for the sample of 4903 AGB stars (3373 O-rich; 1168 C-rich; 362 S-type), 660 post-AGB stars (326 post-AGB; 334 pre-PN), and 1510 PNe in our Galaxy. For each object in the catalog, we cross-identify the IRAS, AKARI, Midcourse Space Experiment, and 2MASS counterparts. The IR 2CDs can provide useful information about the structure and evolution of the dust envelopes as well as the central stars. To find possible evolutionarymore » tracks from AGB stars to PNe on the 2CDs, we investigate spectral evolution of post-AGB stars by making simple but reasonable assumptions on the evolution of the central star and dust shell. We perform radiative transfer model calculations for the detached dust shells around evolving central stars in the post-AGB phase. We find that the theoretical dust shell model tracks using dust opacity functions of amorphous silicate and amorphous carbon roughly coincide with the densely populated observed points of AGB stars, post-AGB stars, and PNe on various IR 2CDs. Even though some discrepancies are inevitable, the end points of the theoretical post-AGB model tracks generally converge in the region of the observed points of PNe on most 2CDs.« less

A Massive Shell of Supernova-Formed Dust in SNR G54.1+0.3

NASA Technical Reports Server (NTRS)

Temim, Tea; Dwek, Eli; Arendt, Richard G.; Borkowski, Kazimiera J.; Reynolds, Stephen P.; Slane, Patrick; Gelfand, Joseph D.; Raymond, John C.

2017-01-01

While theoretical models of dust condensation predict that most refractory elements produced in core-collapsesupernovae (SNe) efficiently condense into dust, a large quantity of dust has so far only been observed inSN1987A. We present an analysis of observations from the Spitzer Space Telescope, Herschel SpaceObservatory, Stratospheric Observatory for Infrared Astronomy, and AKARI of the infrared shell surrounding thepulsar wind nebula in the supernova remnant G54.1+0.3. We attribute a distinctive spectral feature at 21 m to amagnesium silicate grain species that has been invoked in modeling the ejecta-condensed dust in Cas A, whichexhibits the same spectral signature. If this species is responsible for producing the observed spectral feature andaccounts for a significant fraction of the observed infrared continuum, we find that it would be the dominantconstituent of the dust in G54.1+0.3, with possible secondary contributions from other compositions, such ascarbon, silicate, or alumina grains. The total mass of SN-formed dust required by this model is at least 0.3Me. Wediscuss how these results may be affected by varying dust grain properties and self-consistent grain heating models.The spatial distribution of the dust mass and temperature in G54.1+0.3 confirms the scenario in which the SNformeddust has not yet been processed by the SN reverse shock and is being heated by stars belonging to a clusterin which the SN progenitor exploded. The dust mass and composition suggest a progenitor mass of 1627Me andimply a high dust condensation efficiency, similar to that found for Cas A and SN1987A. The study providesanother example of significant dust formation in a Type IIP SN explosion and sheds light on the properties ofpristine SN-condensed dust.

Far-infrared data for symbiotic stars. II - The IRAS survey observations

NASA Technical Reports Server (NTRS)

Kenyon, S. J.; Fernandez-Castro, T.; Stencel, R. E.

1988-01-01

IRAS survey data for all known symbiotic binaries are reported. S type systems have 25 micron excesses much larger than those of single red giant stars, suggesting that these objects lose mass more rapidly than do normal giants. D type objects have far-IR colors similar to those of Mira variables, implying mass-loss rate of about 10 to the -6th solar masses/yr. The near-IR extinctions of the D types indicate that their Mira components are enshrouded in optically thick dust shells, while their hot companions lie outside the shells. If this interpretation of the data is correct, then the very red near-IR colors of D type symbiotic stars are caused by extreme amounts of dust absorption rather than dust emission. The small group of D prime objects possesses far-IR colors resembling those of compact planetary nebulae or extreme OH/IR stars. It is speculated that these binaries are not symbiotic stars at all, but contain a hot compact star and an exasymptotic branch giant which is in the process of ejecting a planetary nebula shell.

Millennial-scale fluctuations in Saharan dust supply across the decline of the African Humid Period

NASA Astrophysics Data System (ADS)

Zielhofer, Christoph; von Suchodoletz, Hans; Fletcher, William J.; Schneider, Birgit; Dietze, Elisabeth; Schlegel, Michael; Schepanski, Kerstin; Weninger, Bernhard; Mischke, Steffen; Mikdad, Abdeslam

2017-09-01

The Sahara is the world's largest dust source with significant impacts on trans-Atlantic terrestrial and large-scale marine ecosystems. Contested views about a gradual or abrupt onset of Saharan aridity at the end of the African Humid Period dominate the current scientific debate about the Holocene Saharan desiccation. In this study, we present a 19.63 m sediment core sequence from Lake Sidi Ali (Middle Atlas, Morocco) at the North African desert margin. We reconstruct the interaction between Saharan dust supply and Western Mediterranean hydro-climatic variability during the last 12,000 yr based on analyses of lithogenic grain-sizes, XRF geochemistry and stable isotopes of ostracod shells. A robust chronological model based on AMS 14C dated pollen concentrates supports our multi-proxy study. At orbital-scale there is an overall increase in southern dust supply from the Early Holocene to the Late Holocene, but our Northern Saharan dust record indicates that a gradual Saharan desiccation was interrupted by multiple abrupt dust increases before the 'southern dust mode' was finally established at 4.7 cal ka BP. The Sidi Ali record features millennial peaks in Saharan dust increase at about 11.1, 10.2, 9.4, 8.2, 7.3, 6.6, 6.0, and 5.0 cal ka BP. Early Holocene Saharan dust peaks coincide with Western Mediterranean winter rain minima and North Atlantic cooling events. In contrast, Late Holocene dust peaks correspond mostly with prevailing positive phases of the North Atlantic Oscillation. By comparing with other North African records, we suggest that increases in Northern Saharan dust supply do not solely indicate sub-regional to regional aridity in Mediterranean Northwest Africa but might reflect aridity at a trans-Saharan scale. In particular, our findings support major bimillennial phases of trans-Saharan aridity at 10.2, 8.2, 6.0 and 4.2 cal ka BP. These phases coincide with North Atlantic cooling and a weak African monsoon.

Driving gas shells with radiation pressure on dust in radiation-hydrodynamic simulations

NASA Astrophysics Data System (ADS)

Costa, Tiago; Rosdahl, Joakim; Sijacki, Debora; Haehnelt, Martin G.

2018-01-01

We present radiation-hydrodynamic simulations of radiatively-driven gas shells launched by bright active galactic nuclei (AGN) in isolated dark matter haloes. Our goals are (1) to investigate the ability of AGN radiation pressure on dust to launch galactic outflows and (2) to constrain the efficiency of infrared (IR) multiscattering in boosting outflow acceleration. Our simulations are performed with the radiation-hydrodynamic code RAMSES-RT and include both single- and multiscattered radiation pressure from an AGN, radiative cooling and self-gravity. Since outflowing shells always eventually become transparent to the incident radiation field, outflows that sweep up all intervening gas are likely to remain gravitationally bound to their halo even at high AGN luminosities. The expansion of outflowing shells is well described by simple analytic models as long as the shells are mildly optically thick to IR radiation. In this case, an enhancement in the acceleration of shells through IR multiscattering occurs as predicted, i.e. a force \\dot{P} ≈ τ_IR L/c is exerted on the gas. For high optical depths τIR ≳ 50, however, momentum transfer between outflowing optically thick gas and IR radiation is rapidly suppressed, even if the radiation is efficiently confined. At high τIR, the characteristic flow time becomes shorter than the required trapping time of IR radiation such that the momentum flux \\dot{P} ≪ τ_IR L/c. We argue that while unlikely to unbind massive galactic gaseous haloes, AGN radiation pressure on dust could play an important role in regulating star formation and black hole accretion in the nuclei of massive compact galaxies at high redshift.

VizieR Online Data Catalog: Investigation of mass loss mechanism of LPVs (Winters+, 2000)

NASA Astrophysics Data System (ADS)

Winters, J. M.; Le Bertre, T.; Jeong, K. S.; Helling, C.; Sedlmayr, E.

2000-09-01

Parameters and resultant quantities of a grid of hydrodynamical models for the circumstellar dust shells around pulsating red giants which treat the time-dependent hydrodynamics and include a detailed treatment of the dust formation process. (1 data file).

The mass-loss return from evolved stars to the Large Magellanic Cloud. V. The GRAMS carbon-star model grid

NASA Astrophysics Data System (ADS)

Srinivasan, S.; Sargent, B. A.; Meixner, M.

2011-08-01

Context. Outflows from asymptotic giant branch (AGB) and red supergiant (RSG) stars inject dust into the interstellar medium. The total rate of dust return provides an important constraint to galactic chemical evolution models. However, this requires detailed radiative transfer (RT) modeling of individual stars, which becomes impractical for large data sets. An alternative approach is to select the best-fit spectral energy distribution (SED) from a grid of dust shell models, allowing for a faster determination of the luminosities and mass-loss rates for entire samples. Aims: We have developed the Grid of RSG and AGB ModelS (GRAMS) to measure the mass-loss return from evolved stars. The models span the range of stellar, dust shell and grain properties relevant to evolved stars. The GRAMS model database will be made available to the scientific community. In this paper we present the carbon-rich AGB model grid and compare our results with photometry and spectra of Large Magellanic Cloud (LMC) carbon stars from the SAGE (Surveying the Agents of Galaxy Evolution) and SAGE-Spec programs. Methods: We generate models for spherically symmetric dust shells using the 2Dust code, with hydrostatic models for the central stars. The model photospheres have effective temperatures between 2600 and 4000 K and luminosities from ~2000 L⊙ to ~40 000 L⊙. Assuming a constant expansion velocity, we explore five values of the inner radius Rin of the dust shell (1.5, 3, 4.5, 7 and 12 Rstar). We fix the outer radius at 1000 Rin. Based on the results from our previous study, we use amorphous carbon dust mixed with 10% silicon carbide by mass. The grain size distribution follows a power-law and an exponential falloff at large sizes. The models span twenty-six values of 11.3 μm optical depth, ranging from 0.001 to 4. For each model, 2Dust calculates the output SED from 0.2 to 200 μm. Results: Over 12 000 models have dust temperatures below 1800 K. For these, we derive synthetic photometry in optical, near-infrared and mid-infrared filters for comparison with available data. We find good agreement with magnitudes and colors observed for LMC carbon-rich and extreme AGB star candidates from the SAGE survey, as well as spectroscopically confirmed carbon stars from the SAGE-Spec study. Our models reproduce the IRAC colors of most of the extreme AGB star candidates, consistent with the expectation that a majority of these enshrouded stars have carbon-rich dust. Finally, we fit the SEDs of some well-studied carbon stars and compare the resulting luminosities and mass-loss rates with those from previous studies. The model grid is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/532/A54

Evolution of Dust in Primordial Supernova Remnants and Its Influence on the Elemental Composition of Hyper-Metal-Poor Stars

NASA Astrophysics Data System (ADS)

Nozawa, Takaya; Kozasa, Takashi; Habe, Asao; Dwek, Eli; Umeda, Hideyuki; Tominaga, Nozomu; Maeda, Keiichi; Nomoto, Ken'ichi

2008-05-01

The calculations for the evolution of dust within Population III supernova remnants (SNRs) are presented, based on the models of dust formed in the unmixed ejecta of Type II SNe. We show that once dust grains collide with the reverse shock penetrating into the ejecta, their fates strongly depend on the initial radius aini. For SNRs expanding into the interstellar medium (ISM) with nH,0 = 1 cm-3, grains of aini<0.05 μm are trapped in the hot gas to be completely destroyed; grains of aini = 0.05-0.2 μm are piled up in the dense shell formed behind the forward shock; grains of aini>0.2 μm are injected into the ISM without being eroded significantly. The total mass of surviving dust is 0.01 to 0.8 Msolar for nH,0 = 10 to 0.1 cm-3. We also investigate the influence of the piled-up dust on the elemental abundances of the second-generation stars formed in the dense shell of Population III SNRs. The comparison of the calculated elemental abundances with those observed in hyper-metal-poor (HMP) and ultra-metal-poor (UMP) stars indicates that the transport of dust separated from metal-rich gas can be an important process in determining the abundance patterns of Mg and Si in HMP and UMP stars.

Observations of circumstellar carbon monoxide and evidence for multiple ejections in red giants

NASA Technical Reports Server (NTRS)

Bernat, A. P.

1981-01-01

Observations of the fundamental 4.6 micron band of CO in nine red giants are presented. A common feature is multiple absorption lines which are identified as products of separate components or shells. Column densities are derived; the relative values should be free of the uncertainties inherent in determining the absolute scale. These column densities are well fitted by single excitation temperatures for each absorption component; these excitation temperatures are identified with the local kinetic temperatures. There is no correlation of CO column density with either gas or dust column density nor of the expansion velocity of the component with its distance from the star. The evidence is reviewed, and it is concluded that mass loss from red giants is most likely episodic in nature.

DIRT: Dust InfraRed Toolbox

NASA Astrophysics Data System (ADS)

Pound, Marc W.; Wolfire, Mark G.; Mundy, Lee G.; Teuben, Peter; Lord, Steve

2011-02-01

DIRT is a Java applet for modelling astrophysical processes in circumstellar dust shells around young and evolved stars. With DIRT, you can: select and display over 500,000 pre-run model spectral energy distributions (SEDs) find the best-fit model to your data set account for beam size in model fitting manipulate data and models with an interactive viewer display gas and dust density and temperature profiles display model intensity profiles at various wavelengths

A Massive Shell of Supernova-formed Dust in SNR G54.1+0.3

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

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

While theoretical models of dust condensation predict that most refractory elements produced in core-collapse supernovae (SNe) efficiently condense into dust, a large quantity of dust has so far only been observed in SN 1987A. We present an analysis of observations from the Spitzer Space Telescope , Herschel Space Observatory , Stratospheric Observatory for Infrared Astronomy, and AKARI of the infrared shell surrounding the pulsar wind nebula in the supernova remnant G54.1+0.3. We attribute a distinctive spectral feature at 21 μ m to a magnesium silicate grain species that has been invoked in modeling the ejecta-condensed dust in Cas A, whichmore » exhibits the same spectral signature. If this species is responsible for producing the observed spectral feature and accounts for a significant fraction of the observed infrared continuum, we find that it would be the dominant constituent of the dust in G54.1+0.3, with possible secondary contributions from other compositions, such as carbon, silicate, or alumina grains. The total mass of SN-formed dust required by this model is at least 0.3 M {sub ⊙}. We discuss how these results may be affected by varying dust grain properties and self-consistent grain heating models. The spatial distribution of the dust mass and temperature in G54.1+0.3 confirms the scenario in which the SN-formed dust has not yet been processed by the SN reverse shock and is being heated by stars belonging to a cluster in which the SN progenitor exploded. The dust mass and composition suggest a progenitor mass of 16–27 M {sub ⊙} and imply a high dust condensation efficiency, similar to that found for Cas A and SN 1987A. The study provides another example of significant dust formation in a Type IIP SN explosion and sheds light on the properties of pristine SN-condensed dust.« less

POLARIZATION MEASUREMENTS OF HOT DUST STARS AND THE LOCAL INTERSTELLAR MEDIUM

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

Marshall, J. P.; Cotton, D. V.; Bott, K.

2016-07-10

Debris discs are typically revealed through the presence of excess emission at infrared wavelengths. Most discs exhibit excess at mid- and far-infrared wavelengths, analogous to the solar system’s Asteroid and Edgeworth-Kuiper belts. Recently, stars with strong (∼1%) excess at near-infrared wavelengths were identified through interferometric measurements. Using the HIgh Precision Polarimetric Instrument, we examined a sub-sample of these hot dust stars (and appropriate controls) at parts-per-million sensitivity in SDSS g ′ (green) and r ′ (red) filters for evidence of scattered light. No detection of strongly polarized emission from the hot dust stars is seen. We, therefore, rule out scatteredmore » light from a normal debris disk as the origin of this emission. A wavelength-dependent contribution from multiple dust components for hot dust stars is inferred from the dispersion (the difference in polarization angle in red and green) of southern stars. Contributions of 17 ppm (green) and 30 ppm (red) are calculated, with strict 3- σ upper limits of 76 and 68 ppm, respectively. This suggests weak hot dust excesses consistent with thermal emission, although we cannot rule out contrived scenarios, e.g., dust in a spherical shell or face-on discs. We also report on the nature of the local interstellar medium (ISM), obtained as a byproduct of the control measurements. Highlights include the first measurements of the polarimetric color of the local ISM and the discovery of a southern sky region with a polarization per distance thrice the previous maximum. The data suggest that λ {sub max}, the wavelength of maximum polarization, is bluer than typical.« less

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.

Measurement of the sizes of circumstellar dust shells around evolved stars with high mass loss rates

NASA Technical Reports Server (NTRS)

Phillips, T. G.; Knapp, G. R.

1992-01-01

The research supported by the NASA ADP contract NAG5-1153 has been completed. The attached paper, which will be submitted for publication in the Astrophysical Journal in January 1992, presents the results of this work. Here is a summary of the project and its results. A set of computer programs was developed to process the raw 60 micron and 100 micron IRAS survey data. The programs were designed to detect faint extended emission surrounding a bright unresolved source. Candidate objects were chosen from a list of red giant stars and young planetary nebulae which have been detected in millimeter/submillimeter lines of CO. Of the 279 stars examined, 55 were resolved at 60 microns. The principle results of the study are given. The average age for the shells surrounding the 9 Mira-type stars which are extended is 6 x 10(exp 4) yr. This suggests that the period during which these stars lose mass lasts for approx 10(exp 5) yr. The oldest shell found surrounds U Ori, and the youngest surrounds Mira itself. Some shells appear to be detached from the central star. This phenomenon is more common among older stars, suggesting that the mass loss becomes more episodic as the star sheds its envelope. Although all 8 stars less distant than 200 pc are resolved in the IRAS 60 micron data, 29 stars within 500 pc were not. These stars probably have younger circumstellar shells than those which were resolved. Almost all the carbon stars with distances of 500 pc or less have resolved shells, while only 1/2 of the oxygen-rich stars do. The resolved carbon star shells also are older on average than the oxygen-rich ones. These facts imply that carbon stars have been losing mass for a longer period, on average, than oxygen-rich red giants. Large circumstellar shells tend to be found at large distances from the galactic plane, confirming that the ISM density limits the size to which a dust shell can grow. Surprisingly, even very large shells seem to be nearly spherical, and do not appear to be distorted by ram-pressure caused by the star's motion with respect to the ISM. Radiative transfer models and the value of I sub 60 microns/I sub 100 microns allow the average dust temperature in the outer regions of a circumstellar shell to be estimated. The typical value obtained in about 35 K.

3D dust clouds (Yukawa Balls) in strongly coupled dusty plasmas

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

Melzer, A.; Passvogel, M.; Miksch, T.

2010-06-16

Three-dimensional finite systems of charged dust particles confined to concentric spherical shells in a dusty plasma, so-called 'Yukawa balls', have been studied with respect to their static and dynamic properties. Here, we review the charging of particles in a dusty plasma discharge by computer simulations and the respective particle arrangements. The normal mode spectrum of Yukawa balls is measured from the 3D thermal Brownian motion of the dust particles around their equilibrium positions.

Imaging the asymmetric dust shell around CI Cam with long baseline optical interferometry

NASA Astrophysics Data System (ADS)

Thureau, N. D.; Monnier, J. D.; Traub, W. A.; Millan-Gabet, R.; Pedretti, E.; Berger, J.-P.; Garcia, M. R.; Schloerb, F. P.; Tannirkulam, A.-K.

2009-09-01

We present the first high angular resolution observation of the B[e] star/X-ray transient object CI Cam, performed with the two-telescope Infrared Optical Telescope Array (IOTA), its upgraded three-telescope version (IOTA3T) and the Palomar Testbed Interferometer (PTI). Visibilities and closure phases were obtained using the IONIC-3 integrated optics beam combiner. CI Cam was observed in the near-infrared H and K spectral bands, wavelengths well suited to measure the size and study the geometry of the hot dust surrounding CI Cam. The analysis of the visibility data over an 8yr period from soon after the 1998 outburst to 2006 shows that the dust visibility has not changed over the years. The visibility data show that CI Cam is elongated which confirms the disc-shape of the circumstellar environment and totally rules out the hypothesis of a spherical dust shell. Closure phase measurements show direct evidence of asymmetries in the circumstellar environment of CI Cam and we conclude that the dust surrounding CI Cam lies in an inhomogeneous disc seen at an angle. The near-infrared dust emission appears as an elliptical skewed Gaussian ring with a major axis a = 7.58 +/- 0.24mas, an axis ratio r = 0.39 +/- 0.03 and a position angle θ = 35° +/- 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 (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.

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.

Dust and molecular shells in asymptotic giant branch stars

NASA Astrophysics Data System (ADS)

Zhao-Geisler, R.; Quirrenbach, A.; Köhler, R.; Lopez, B.

2012-09-01

Context. Asymptotic giant branch (AGB) stars are one of the largest distributors of dust into the interstellar medium. However, the wind formation mechanism and dust condensation sequence leading to the observed high mass-loss rates have not yet been constrained well observationally, in particular for oxygen-rich AGB stars. Aims: The immediate objective in this work is to identify molecules and dust species which are present in the layers above the photosphere, and which have emission and absorption features in the mid-infrared (IR), causing the diameter to vary across the N-band, and are potentially relevant for the wind formation. Methods: Mid-IR (8-13 μm) interferometric data of four oxygen-rich AGB stars (R Aql, R Aqr, R Hya, and W Hya) and one carbon-rich AGB star (V Hya) were obtained with MIDI/VLTI between April 2007 and September 2009. The spectrally dispersed visibility data are analyzed by fitting a circular fully limb-darkened disk (FDD). Results: The FDD diameter as function of wavelength is similar for all oxygen-rich stars. The apparent size is almost constant between 8 and 10 μm and gradually increases at wavelengths longer than 10 μm. The apparent FDD diameter in the carbon-rich star V Hya essentially decreases from 8 to 12 μm. The FDD diameters are about 2.2 times larger than the photospheric diameters estimated from K-band observations found in the literature. The silicate dust shells of R Aql, R Hya and W Hya are located fairly far away from the star, while the silicate dust shell of R Aqr and the amorphous carbon (AMC) and SiC dust shell of V Hya are found to be closer to the star at around 8 photospheric radii. Phase-to-phase variations of the diameters of the oxygen-rich stars could be measured and are on the order of 15% but with large uncertainties. Conclusions: From a comparison of the diameter trend with the trends in RR Sco and S Ori it can be concluded that in oxygen-rich stars the overall larger diameter originates from a warm molecular layer of H2O, and the gradual increase longward of 10 μm can be most likely attributed to the contribution of a close Al2O3 dust shell. The chromatic trend of the Gaussian FWHM in V Hya can be explained with the presence of AMC and SiC dust. The observations suggest that the formation of amorphous Al2O3 in oxygen-rich stars occurs mainly around or after visual minimum. However, no firm conclusions can be drawn concerning the mass-loss mechanism. Future modeling with hydrostatic and self-consistent dynamical stellar atmospheric models will be required for a more certain understanding. Based on observations made with the Very Large Telescope Interferometer (VLTI) at the Paranal Observatory under program IDs 079.D-0140, 080.D-0005, 081.D-0198, 082.D-0641 and 083.D-0294.Color versions of the figures and Appendices A-C are available in electronic form at http://www.aanda.orgFITS files of the calibrated visibilities are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/545/A56

Polarimetry and spectroscopy of the "oxygen flaring" DQ Herculis-like nova: V5668 Sagittarii (2015)

NASA Astrophysics Data System (ADS)

Harvey, E. J.; Redman, M. P.; Darnley, M. J.; Williams, S. C.; Berdyugin, A.; Piirola, V. E.; Fitzgerald, K. P.; O'Connor, E. G. P.

2018-03-01

Context. Classical novae are eruptions on the surface of a white dwarf in a binary system. The material ejected from the white dwarf surface generally forms an axisymmetric shell of gas and dust around the system. The three-dimensional structure of these shells is difficult to untangle when viewed on the plane of the sky. In this work a geometrical model is developed to explain new observations of the 2015 nova V5668 Sagittarii. Aim. We aim to better understand the early evolution of classical nova shells in the context of the relationship between polarisation, photometry, and spectroscopy in the optical regime. To understand the ionisation structure in terms of the nova shell morphology and estimate the emission distribution directly following the light curve's dust-dip. Methods: High-cadence optical polarimetry and spectroscopy observations of a nova are presented. The ejecta is modelled in terms of morpho-kinematics and photoionisation structure. Results: Initially observational results are presented, including broadband polarimetry and spectroscopy of V5668 Sgr nova during eruption. Variability over these observations provides clues towards the evolving structure of the nova shell. The position angle of the shell is derived from polarimetry, which is attributed to scattering from small dust grains. Shocks in the nova outflow are suggested in the photometry and the effect of these on the nova shell are illustrated with various physical diagnostics. Changes in density and temperature as the super soft source phase of the nova began are discussed. Gas densities are found to be of the order of 109 cm-3 for the nova in its auroral phase. The blackbody temperature of the central stellar system is estimated to be around 2.2 × 105 K at times coincident with the super soft source turn-on. It was found that the blend around 4640 Å commonly called "nitrogen flaring" is more naturally explained as flaring of the O II multiplet (V1) from 4638-4696 Å, i.e. "oxygen flaring". Conclusions: V5668 Sgr (2015) was a remarkable nova of the DQ Her class. Changes in absolute polarimetric and spectroscopic multi-epoch observations lead to interpretations of physical characteristics of the nova's evolving outflow. The high densities that were found early-on combined with knowledge of the system's behaviour at other wavelengths and polarimetric measurements strongly suggest that the visual "cusps" are due to radiative shocks between fast and slow ejecta that destroy and create dust seed nuclei cyclically.

Theoretical studies of the infrared emission from circumstellar dust shells: the infrared characteristics of circumstellar silicates and the mass-loss rate of oxygen-rich late-type giants

NASA Technical Reports Server (NTRS)

Schutte, W. A.; Tielens, A. G.; Allamandola, L. J. (Principal Investigator)

1989-01-01

We have modeled the infrared emission of spherically symmetric, circumstellar dust shells with the aim of deriving the infrared absorption properties of circumstellar silicate grains and the mass-loss rates of the central stars. As a basis for our numerical studies, a simple semianalytical formula has been derived that illustrates the essential characteristics of the infrared emission of such dust shells. A numerical radiative transfer program has been developed and applied to dust shells around oxygen-rich late-type giants. Free parameters in such models include the absorption properties and density distribution of the dust. An approximate, analytical expression is derived for the density distribution of circumstellar dust driven outward by radiation pressure from a central source. A large grid of models has been calculated to study the influence of the free parameters on the emergent spectrum. These results form the basis for a comparison with near-infrared observations. Observational studies have revealed a correlation between the near-infrared color temperature, Tc, and the strength of the 10 micrometers emission or absorption feature, A10. This relationship, which essentially measures the near-infrared optical depth in terms of the 10 micrometers optical depth, is discussed. Theoretical A10-Tc relations have been calculated and compared to the observations. The results show that this relation is a sensitive way to determine the ratio of the near-infrared to 10 micrometers absorption efficiency of circumstellar silicates. These results as well as previous studies show that the near-infrared absorption efficiency of circumstellar silicate grains is much higher than expected from terrestrial minerals. We suggest that this enhanced absorption is due to the presence of ferrous iron (Fe2+) color centers dissolved in the circumstellar silicates. By using the derived value for the ratio of the near-infrared to 10 micrometers absorption efficiency, the observed A10-Tc relation can be calibrated in terms of the total dust column density of the circumstellar shell and thus the mass-loss rate of late-type giants can easily be derived. Detailed models have been made of the infrared emission of three well-studied Miras: R Cas, IRC 10011, and OH 26.5+0.6, with the emphasis on the shape of the 10 micrometers emission or absorption feature. The results show that the intrinsic shape of the 10 micrometers resonance varies from a very broad feature in R Cas to a relatively narrower feature in OH 26.5+0.6, with IRC 10011 somewhere in between. Possible origins of this variation are discussed. The mass-loss rates from these objects are calculated to be 3 x 10(-7), 2 x 10(-5), and 2 x 10(-4) M Sun yr-1 for R Cas, IRC 10011, and OH 26.5+0.6, respectively. These results are compared to other determinations in the literature.

Planck intermediate results: XXXIV. The magnetic field structure in the Rosette Nebula

DOE PAGES

Aghanim, N.; Alves, M. I. R.; Arnaud, M.; ...

2016-02-09

Planck has mapped the polarized dust emission over the whole sky, making it possible to trace the Galactic magnetic field structure that pervades the interstellar medium (ISM). In this paper, we combine polarization data from Planck with rotation measure (RM) observations towards a massive star-forming region, the Rosette Nebula in the Monoceros molecular cloud, to study its magnetic field structure and the impact of an expanding H ii region on the morphology of the field. We derive an analytical solution for the magnetic field, assumed to evolve from an initially uniform configuration following the expansion of ionized gas and themore » formation of a shell of swept-up ISM. From the RM data we estimate a mean value of the line-of-sight component of the magnetic field of about 3 μG (towards the observer) in the Rosette Nebula, for a uniform electron density of about 12 cm -3. The dust shell that surrounds the Rosette H ii region is clearly observed in the Planck intensity map at 353 GHz, with a polarization signal significantly different from that of the local background when considered asa whole. The Planck observations constrain the plane-of-the-sky orientation of the magnetic field in the Rosette’s parent molecular cloud to be mostly aligned with the large-scale field along the Galactic plane. The Planck data are compared with the analytical model, which predicts the mean polarization properties of a spherical and uniform dust shell for a given orientation of the field. This comparison leads to an upper limit of about 45° on the angle between the line of sight and the magnetic field in the Rosette complex, for an assumed intrinsic dust polarization fraction of 4%. This field direction can reproduce the RM values detected in the ionized region if the magnetic field strength in the Monoceros molecular cloud is in the range 6.5–9 μG. Finally, the present analytical model is able to reproduce the RM distribution across the ionized nebula, as well as the mean dust polarization properties of the swept-up shell, and can be directly applied to other similar objects.« less

Planck intermediate results: XXXIV. The magnetic field structure in the Rosette Nebula

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

Aghanim, N.; Alves, M. I. R.; Arnaud, M.

Planck has mapped the polarized dust emission over the whole sky, making it possible to trace the Galactic magnetic field structure that pervades the interstellar medium (ISM). In this paper, we combine polarization data from Planck with rotation measure (RM) observations towards a massive star-forming region, the Rosette Nebula in the Monoceros molecular cloud, to study its magnetic field structure and the impact of an expanding H ii region on the morphology of the field. We derive an analytical solution for the magnetic field, assumed to evolve from an initially uniform configuration following the expansion of ionized gas and themore » formation of a shell of swept-up ISM. From the RM data we estimate a mean value of the line-of-sight component of the magnetic field of about 3 μG (towards the observer) in the Rosette Nebula, for a uniform electron density of about 12 cm -3. The dust shell that surrounds the Rosette H ii region is clearly observed in the Planck intensity map at 353 GHz, with a polarization signal significantly different from that of the local background when considered asa whole. The Planck observations constrain the plane-of-the-sky orientation of the magnetic field in the Rosette’s parent molecular cloud to be mostly aligned with the large-scale field along the Galactic plane. The Planck data are compared with the analytical model, which predicts the mean polarization properties of a spherical and uniform dust shell for a given orientation of the field. This comparison leads to an upper limit of about 45° on the angle between the line of sight and the magnetic field in the Rosette complex, for an assumed intrinsic dust polarization fraction of 4%. This field direction can reproduce the RM values detected in the ionized region if the magnetic field strength in the Monoceros molecular cloud is in the range 6.5–9 μG. Finally, the present analytical model is able to reproduce the RM distribution across the ionized nebula, as well as the mean dust polarization properties of the swept-up shell, and can be directly applied to other similar objects.« less

A close halo of large transparent grains around extreme red giant stars

NASA Astrophysics Data System (ADS)

Norris, Barnaby R. M.; Tuthill, Peter G.; Ireland, Michael J.; Lacour, Sylvestre; Zijlstra, Albert A.; Lykou, Foteini; Evans, Thomas M.; Stewart, Paul; Bedding, Timothy R.

2012-04-01

An intermediate-mass star ends its life by ejecting the bulk of its envelope in a slow, dense wind. Stellar pulsations are thought to elevate gas to an altitude cool enough for the condensation of dust, which is then accelerated by radiation pressure, entraining the gas and driving the wind. Explaining the amount of mass loss, however, has been a problem because of the difficulty of observing tenuous gas and dust only tens of milliarcseconds from the star. For this reason, there is no consensus on the way sufficient momentum is transferred from the light from the star to the outflow. Here we report spatially resolved, multiwavelength observations of circumstellar dust shells of three stars on the asymptotic giant branch of the Hertzsprung-Russell diagram. When imaged in scattered light, dust shells were found at remarkably small radii (less than about two stellar radii) and with unexpectedly large grains (about 300 nanometres in radius). This proximity to the photosphere argues for dust species that are transparent to the light from the star and, therefore, resistant to sublimation by the intense radiation field. Although transparency usually implies insufficient radiative pressure to drive a wind, the radiation field can accelerate these large grains through photon scattering rather than absorption--a plausible mass loss mechanism for lower-amplitude pulsating stars.

Images of the 10-micron source in the Cygnus 'Egg'

NASA Technical Reports Server (NTRS)

Jaye, D.; Fienberg, R. Tresch; Fazio, G. G.; Gezari, D. Y.; Lamb, G. M.; Shu, P. K.; Hoffmann, W. F.; Mccreight, C. R.

1989-01-01

Mid-IR images of AFGL 2688, the Egg nebula, obtained with a 16 x 16 pixel array camera (field of view 12.5 x 12.5 arcsec) resolve the central source. It appears as a centrally peaked ellipsoid with major axis of symmetry parallel to the axis of the visible nebulosity. This is contrary to the expected extension perpendicular to this axis implied by proposed dust-toroid models of the IR source. Maps of the spatial distribution of 8-13 micron color temperature and warm dust opacity derived from the multiwavelength images further characterize the IR emission. The remarkable flatness of the color temperature conflicts with the radial temperature gradient expected across a thick shell of material with a single heat source at its center. The new data suggest instead that the source consists of a central star surrounded by a dust shell that is too thin to provide a detectable temperature gradient and too small to permit the resolution of limb brightening.

Dust composition and mass-loss return from the luminous blue variable R71 in the LMC

NASA Astrophysics Data System (ADS)

Guha Niyogi, S.; Min, M.; Meixner, M.; Waters, L. B. F. M.; Seale, J.; Tielens, A. G. G. M.

2014-09-01

Context. We present an analysis of mid- and far-infrared (IR) spectrum and spectral energy distribution (SED) of the luminous blue variable (LBV) R71 in the Large Magellanic Cloud (LMC). Aims: This work aims to understand the overall contribution of high-mass LBVs to the total dust-mass budget of the interstellar medium (ISM) of the LMC and compare this with the contribution from low-mass asymptotic giant branch (AGB) stars. As a case study, we analyze the SED of R71. Methods: We compiled all the available photometric and spectroscopic observational fluxes from various telescopes for a wide wavelength range (0.36-250 μm). We determined the dust composition from the spectroscopic data, and derived the ejected dust mass, dust mass-loss rate, and other dust shell properties by modeling the SED of R71. We noted nine spectral features in the dust shell of R71 by analyzing Spitzer Space Telescope spectroscopic data. Among these, we identified three new crystalline silicate features. We computed our model spectrum by using 3D radiative transfer code MCMax. Results: Our model calculation shows that dust is dominated by amorphous silicates, with some crystalline silicates, metallic iron, and a very tiny amount of polycyclic aromatic hydrocarbon (PAH) molecules. The presence of both silicates and PAHs indicates that the dust has a mixed chemistry. We derived a dust mass of 0.01 M⊙, from which we arrive at a total ejected mass of ≈5 M⊙. This implies a time-averaged dust mass-loss rate of 2.5 × 10-6 M⊙ yr-1 with an explosion about 4000 years ago. We assume that the other five confirmed dusty LBVs in the LMC loose mass at a similar rate, and estimate the total contribution to the mass budget of the LMC to be ≈10-5 M⊙ yr-1, which is comparable to the contribution by all the AGB stars in the LMC. Conclusions: Based on our analysis on R71, we speculate that LBVs as a class may be an important dust source in the ISM of the LMC.

Watching a 'New Star' Make the Universe Dusty

NASA Astrophysics Data System (ADS)

2008-07-01

Using ESO's Very Large Telescope Interferometer, and its remarkable acuity, astronomers were able for the first time to witness the appearance of a shell of dusty gas around a star that had just erupted, and follow its evolution for more than 100 days. This provides the astronomers with a new way to estimate the distance of this object and obtain invaluable information on the operating mode of stellar vampires, dense stars that suck material from a companion. Uncovering the disc ESO PR Photo 22/08 Dust shells around a nova Although novae were first thought to be new stars appearing in the sky, hence their Latin name, they are now understood as signaling the brightening of a small, dense star. Novae occur in double star systems comprising a white dwarf - the end product of a solar-like star - and, generally, a low-mass normal star - a red dwarf. The two stars are so close together that the red dwarf cannot hold itself together and loses mass to its companion. Occasionally, the shell of matter that has fallen onto the ingesting star becomes unstable, leading to a thermonuclear explosion which makes the system brighter. Nova Scorpii 2007a (or V1280 Scorpii), was discovered by Japanese amateur astronomers on 4 February 2007 towards the constellation Scorpius ("the Scorpion"). For a few days, it became brighter and brighter, reaching its maximum on 17 February, to become one of the brightest novae of the last 35 years. At that time, it was easily visible with the unaided eye. Eleven days after reaching its maximum, astronomers witnessed the formation of dust around the object. Dust was present for more than 200 days, as the nova only slowly emerged from the smoke between October and November 2007. During these 200 days, the erupting source was screened out efficiently, becoming more than 10,000 times dimmer in the visual. An unprecedented high spatial resolution monitoring of the dust formation event was carried out with the Very Large Telescope Interferometer (VLTI), extending over more than 5 months following the discovery. The astronomers first used the AMBER near-infrared instrument, then, as the nova continued to produce dust at a high rate, they moved to using the MIDI mid-infrared instrument, that is more sensitive to the radiation of the hot dust. Similarly, as the nova became fainter, the astronomers switched from the 1.8-m Auxiliary Telescopes to their larger brethren, the 8.2-m Unit Telescopes. With the interferometry mode, the resolution obtained is equivalent to using a telescope with a size between 35 and 71 metres (the distance between the 2 telescopes used). The first observations, secured 23 days after the discovery, showed that the source was very compact, less than 1 thousandth of an arcsecond (1 milli-arcsecond or mas), which is a size comparable to viewing one grain of sand from about 100 kilometres away. A few days later, after the detection of the major dust formation event, the source measured 13 mas. "It is most likely that the latter size corresponds to the diameter of the dust shell in expansion, while the size previously measured was an upper limit of the erupting source," explains lead author Olivier Chesneau. Over the following months the dusty shell expanded regularly, at a rate close to 2 million km/h. "This is the first time that the dust shell of a nova is spatially resolved and its evolution traced starting from the onset of its formation up to the point that it becomes too diluted to be seen", says co-author Dipankar Banerjee, from India. The measurement of the angular expansion rate, together with the knowledge of the expansion velocity, enables the astronomer to derive the distance of the object, in this case about 5500 light-years. "This is a new and promising technique for providing distances of close novae. This was made possible because the state of the art facility of the VLTI, both in terms of infrastructure and management of the observations, allows one to schedule such observations," says co-author Markus Wittkowski from ESO. Moreover, the quality of the data provided by the VLTI was such that it was possible to estimate the daily production of dust and infer the total mass ejected. "Overall, V1280 Sco probably ejected more than the equivalent of 33 times the mass of the Earth, a rather impressive feat if one considers that this mass was ejected from a star not larger in radius than the Earth," concludes Chesneau. Of this material, about a percent or less was in the form of dust.

Gas and dust spectra of the D' type symbiotic star HD 330036

NASA Astrophysics Data System (ADS)

Angeloni, R.; Contini, M.; Ciroi, S.; Rafanelli, P.

2007-09-01

Aims:We present a comprehensive and self-consistent modelling of the D' type symbiotic star (SS) HD 330036 from radio to UV. Methods: Within a colliding-wind scenario, we analyse the continuum, line, and dust spectra by means of SUMA, a code that simulates the physical conditions of an emitting gaseous cloud under the coupled effect of ionisation from an external radiation source and shocks. Results: We find that the UV lines are emitted from high-density gas between thestars downstream of the reverse shock, while the optical lines are emitted downstream of the shock propagating outwards from the system. As regards the continuum SED, three shells are identified in the IR, at 850 K, 320 K, and 200 K with radii r = 2.8 × 1013 cm, 4 × 1014 cm, and 1015 cm, respectively, after adopting a distance to Earth of d=2.3 kpc. Interestingly, all these shells appear to be circumbinary. Analysis of the unexploited ISO-SWS spectrum reveals that both PAHs and crystalline silicates coexist in HD 330036, with PAHs associated to the internal shell at 850 K, and crystalline silicates stored in the cool shells at 320 K and 200 K. Strong evidence that crystalline silicates are shaped in a disk-like structure is derived on the basis of the relative band strengths. Finally, we suggest that shocks can be a reliable mechanism for activating the annealing and the consequent crystallisation processes. Conclusions: We show that a consistent interpretation of gas and dust spectra emitted by SS can be obtained by models that account for the coupled effect of the photoionising flux and of shocks. The VLTI/MIDI proposal recently accepted by ESO aims to verify and better constrain some of our results by means of IR interferometric observations.

Dust Around Herbig Ae Stars: Additional Constraints from their Photometric and Polarimetric Variability

NASA Technical Reports Server (NTRS)

Krivova, N. A.; Ilin, V. B.; Fischer, O.

1996-01-01

For the Herbig Ae stars with Algol-like minima (UX Ori, WW Vul, etc), the effects of circumstellar dust include: excess infrared emission, anomalous ultraviolet extinction, the 'blueing' of the stars in minima accompanying by an increase of intrinsic polarization. Using a Monte-Carlo code for polarized radiation transfer we have simulated these effects and compared the results obtained for different models with the observational data available. We found that the photometric and polarimetric behavior of the stars provided essential additional constraints on the circumstellar dust models. The models with spheroidal shell geometry and compact (non-fluffy) dust grains do not appear to be able to explain all the data.

The Dust Bowl in the American West: A geochemical record of dust provenance and deposition in the Upper Fremont Glacier ice core

NASA Astrophysics Data System (ADS)

Andrus, C. F. T.; Bassett, C.; Black, H. D.; Payne, T. N.

2016-12-01

Several recent studies demonstrate that nitrogen isotope analysis of the organic fraction of mollusk shells can serve as a proxy for anthropogenic environmental impacts, including sewage input into estuaries. Analysis of δ15N in shells from archaeological sites permits construction of time-series proxy data from the present day to pre-industrial times, yielding insight into the history of some human environmental influences such as waste input and land use changes. Most such studies utilize a single bulk analysis per valve, combining shell material grown over time periods of one or more years. However, large, fast-growing species (e.g. some scallops and abalone) may permit sub-annual sampling, potentially yielding insight into seasonal processes. Such sclerochronological sampling of archaeological shells may enable researchers to detect variation at a finer temporal scale than has been attempted to date, which in turn may facilitate analysis of seasonal resource procurement strategies and related actions. This presentation will incorporate new and published data from the Atlantic, Pacific and Gulf of Mexico coasts of North America to assess how sclerochronological δ15N data can be useful to better understand pre-industrial human-environmental interaction and change, and also address diagenesis and other preservational concerns commonly found in archaeological samples.

R associations. VI - The reddening law in dust clouds and the nature of early-type emission stars in nebulosity from a study of five associations

NASA Technical Reports Server (NTRS)

Herbst, W.; Warner, J. W.; Miller, D. P.; Herzog, A.

1982-01-01

Positions, identification charts, UBVRIKLMN photometry and spectral types are given for stars, illuminating reflection nebulae that are visible on the POSS prints, which have been identified in five associations. With a ratio of total to selective extinction of 4.2, the reddening law applicable to the dust clouds in which the stars are embedded is steeper than normal. The five associations exhibit 18 early-type stars with circumstellar shells, of which those with spectral types earlier than B5 characteristically have weak IR excesses, in contrast to the strong excesses indicative of circumstellar dust, of later-type stars. Color-magnitude charts show a distribution lying above the ZAMS by up to about 2 mag for both the circumstellar shell stars and those classified as rapid rotators. It is suggested that (1) rapid rotation accounts for the scatter in the color-magnitude diagram, and (2) many of the nebulous early-type emission-line stars are rapid rotators rather than pre-main sequence objects.

Multiple shell fusion targets

DOEpatents

Lindl, J.D.; Bangerter, R.O.

1975-10-31

Multiple shell fusion targets for use with electron beam and ion beam implosion systems are described. The multiple shell targets are of the low-power type and use a separate relatively low Z, low density ablator at large radius for the outer shell, which reduces the focusing and power requirements of the implosion system while maintaining reasonable aspect ratios. The targets use a high Z, high density pusher shell placed at a much smaller radius in order to obtain an aspect ratio small enough to protect against fluid instability. Velocity multiplication between these shells further lowers the power requirements. Careful tuning of the power profile and intershell density results in a low entropy implosion which allows breakeven at low powers. For example, with ion beams as a power source, breakeven at 10-20 Terrawatts with 10 MeV alpha particles for imploding a multiple shell target can be accomplished.

SIRTF Tools for DIRT

NASA Astrophysics Data System (ADS)

Pound, M. W.; Wolfire, M. G.; Amarnath, N. S.

2004-07-01

The Dust InfraRed ToolBox (DIRT - a part of the Web Infrared ToolShed, or WITS {http://dustem.astro.umd.edu}) is a Java applet for modeling astrophysical processes in circumstellar shells around young and evolved stars. DIRT has been used by the astrophysics community for about 5 years. Users can automatically and efficiently search grids of pre-calculated models to fit their data. A large set of physical parameters and dust types are included in the model database, which contains over 500,000 models. We are adding new functionality to DIRT to support new missions like SIRTF and SOFIA. A new Instrument module allows for plotting of the model points convolved with the spatial and spectral responses of the selected instrument. This lets users better fit data from specific instruments. Currently, we have implemented modules for the Infrared Array Camera (IRAC) and Multiband Imaging Photometer (MIPS) on SIRTF. The models are based on the dust radiation transfer code of Wolfire & Cassinelli (1986) which accounts for multiple grain sizes and compositions. The model outputs are averaged over the instrument bands using the same weighting (νFν = constant) as the SIRTF data pipeline which allows the SIRTF data products to be compared directly with the model database. This work was supported in part by a NASA AISRP grant NAG 5-10751 and the SIRTF Legacy Science Program provided by NASA through an award issued by JPL under NASA contract 1407.

Nucleation Studies under the Conditions of Carbon-rich AGB Star Envelopes: TiC

NASA Astrophysics Data System (ADS)

Patzer, A. B. C.; Wendt, M.; Chang, C.; Sülzle, D.

2011-09-01

Many studies of dust nucleation in winds of carbon-rich AGB stars consider primarily carbon as the dust forming material. But dust grains formed in such circumstellar envelopes are rather a mixture of several chemical elements such as titanium or silicon in addition to carbon, as verified by many investigations of pre-solar grains enclosed in meteorites, for example. In this contribution we focus on the study of the nucleation of titanium carbide particles from the gas phase. The necessary properties of molecular titanium carbide clusters have been estimated by the density functional approach, and the first implications for the homogeneous nucleation of TiC are studied for conditions representative of circumstellar dust shells around carbon-rich AGB stars.

Radiation-pressure-driven dust waves inside bursting interstellar bubbles

NASA Astrophysics Data System (ADS)

Ochsendorf, B. B.; Verdolini, S.; Cox, N. L. J.; Berné, O.; Kaper, L.; Tielens, A. G. G. M.

2014-06-01

Massive stars drive the evolution of the interstellar medium through their radiative and mechanical energy input. After their birth, they form "bubbles" of hot gas surrounded by a dense shell. Traditionally, the formation of bubbles is explained through the input of a powerful stellar wind, even though direct evidence supporting this scenario is lacking. Here we explore the possibility that interstellar bubbles seen by the Spitzer- and Herschel space telescopes, blown by stars with log (L/L⊙) ≲ 5.2, form and expand because of the thermal pressure that accompanies the ionization of the surrounding gas. We show that density gradients in the natal cloud or a puncture in the swept-up shell lead to an ionized gas flow through the bubble into the general interstellar medium, which is traced by a dust wave near the star, which demonstrates the importance of radiation pressure during this phase. Dust waves provide a natural explanation for the presence of dust inside H II bubbles, offer a novel method to study dust in H II regions and provide direct evidence that bubbles are relieving their pressure into the interstellar medium through a champagne flow, acting as a probe of the radiative interaction of a massive star with its surroundings. We explore a parameter space connecting the ambient density, the ionizing source luminosity, and the position of the dust wave, while using the well studied H II bubbles RCW 120 and RCW 82 as benchmarks of our model. Finally, we briefly examine the implications of our study for the environments of super star clusters formed in ultraluminous infrared galaxies, merging galaxies, and the early Universe, which occur in very luminous and dense environments and where radiation pressure is expected to dominate the dynamical evolution.

Circumstellar shells, the formation of grains, and radiation transfer

NASA Technical Reports Server (NTRS)

Lefevre, Jean

1987-01-01

Advances in infrared astronomy during the last decade have firmly established the presence of dust around a large number of cold giant and supergiant stars. To describe the properties of stars and to understand their evolution, it is necessary to know the nature of the giants and their influence on stellar radiation. Two questions are considered: the formation of grains around cold stars and the modification of stellar radiation by the stellar shell.

Evidence for dust-driven, radial plasma transport in Saturn's inner radiation belts

NASA Astrophysics Data System (ADS)

Roussos, E.; Krupp, N.; Kollmann, P.; Paranicas, C.; Mitchell, D. G.; Krimigis, S. M.; Andriopoulou, M.

2016-08-01

A survey of Cassini MIMI/LEMMS data acquired between 2004 and 2015 has led to the identification of 13 energetic electron microsignatures that can be attributed to particle losses on one of the several faint rings of the planet. Most of the signatures were detected near L-shells that map between the orbits of Mimas and Enceladus or near the G-ring. Our analysis indicates that it is very unlikely for these signatures to have originated from absorption on Mimas, Enceladus or unidentified Moons and rings, even though most were not found exactly at the L-shells of the known rings of the saturnian system (G-ring, Methone, Anthe, Pallene). The lack of additional absorbers is apparent in the L-shell distribution of MeV ions which are very sensitive for tracing the location of weakly absorbing material permanently present in Saturn's radiation belts. This sensitivity is demonstrated by the identification, for the first time, of the proton absorption signatures from the asteroid-sized Moons Pallene, Anthe and/or their rings. For this reason, we investigate the possibility that the 13 energetic electron events formed at known saturnian rings and the resulting depletions were later displaced radially by one or more magnetospheric processes. Our calculations indicate that the displacement magnitude for several of those signatures is much larger than the one that can be attributed to radial flows imposed by the recently discovered noon-to-midnight electric field in Saturn's inner magnetosphere. This observation is consistent with a mechanism where radial plasma velocities are enhanced near dusty obstacles. Several possibilities are discussed that may explain this observation, including a dust-driven magnetospheric interchange instability, mass loading by the pick-up of nanometer charged dust grains and global magnetospheric electric fields induced by perturbed orbits of charged dust due to the act of solar radiation pressure. Indirect evidence for a global scale interaction between the magnetosphere and Saturn's faint rings that may drive such radial transport processes may also exist in previously reported measurements of plasma density by Cassini. Alternative explanations that do not involve enhanced plasma transport near the rings require the presence of a transient absorbing medium, such as E-ring clumps. Such clumps may form at the L-shell range where microsignatures have been observed due to resonances between charged dust and corotating magnetospheric structures, but remote imaging observations of the E-ring are not consistent with such a scenario.

Wintertime Experimental investigation of Morphology, Mixing States and Columnar Optical Properties of Aerosols over a Desert location in India

NASA Astrophysics Data System (ADS)

Mishra, S.; Kumar, T.; Sharma, C.; Prasad, M. V. S. N.; Singh, S.; Agnihotri, R.; Arya, B. C.; Gupta, B.; Naaraayanan, T.; Gautam, S.; Kumar, D.; Sood, K. N.; Tawale, J. S.; Sharma, A. K.; Mitra, A. K.

2014-12-01

Indian Desert (The Thar Desert) is considered as the source of mineral dust in the Indo-Gangetic Plain (IGP) especially in pre-monsoon period due to large scale convective activities during hot summer. To study the physico-chemical characteristics of aerosols over the Thar Desert (Jaisalmer, Rajasthan) during winter (December, 2013), a field campaign has been carried out in Jaisalmer in Rajasthan state. Experiments were conducted inside the city as well as far from the city. The faraway location is close to international border of another country i.e. Pakistan. PM2.5 and PM10 were collected within the city while PM5 was collected far from the city. Particles were collected on Teflon filters for bulk analysis with Fourier Transform Infrared Spectroscopy (FTIR), on Tin substrate for individual particle morphology and elemental composition analysis with Scanning Electron Microscope (SEM) equipped with Energy Dispersive Spectrometer (EDS) and on the Cu-TEM grid for individual particle morphology and mixing state characterization using High Resolution-Transmission Electron Microscope (HRTEM). Together with this, aerosol size distribution observation and columnar spectral aerosol optical properties have been carried out with OPC (Optical Particle Counter, GRIMM Model 1.108) and hand held Microtops-II, respectively. HRTEM analysis reveals occurrence of carbonaceous fractals found in various mixing states 1) aged with some hygroscopic species 2) embedded in sulfate host 3) semi-externally mixed with sulfate and other species. Core-shell particles were also observed with varying core composition (carbon, typical mineral dust, and calcite) and shell thickness (shell comprising of water). The back trajectory analysis reveals the source of wind from Karachi and Islamabad from Pakistan which may be the potential source of carbonaceous species over the sampling site. SEM-EDS analysis reveals occurrence of mineral dust 1) pure mineral dust (Ca and Si rich) 2) polluted mineral dust (mixed with carbon and Cr) together with some pollutants (rich in carbon, S, K, Cl, Mo and Nb). Signatures of various organics were traced using FTIR. Aerosol columnar spectral optical properties, size distribution and meteorology in tandem with aforementioned aerosol properties will be discussed in detail during the presentation.

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.

Anatomy of a Busted Comet

NASA Technical Reports Server (NTRS)

2008-01-01

[figure removed for brevity, see original site] Poster Version (Figure 1)

NASA's Spitzer Space Telescope captured the picture on the left of comet Holmes in March 2008, five months after the comet suddenly erupted and brightened a millionfold overnight. The contrast of the picture has been enhanced on the right to show the anatomy of the comet.

Every six years, comet 17P/Holmes speeds away from Jupiter and heads inward toward the sun, traveling the same route typically without incident. However, twice in the last 116 years, in November 1892 and October 2007, comet Holmes mysteriously exploded as it approached the asteroid belt. Astronomers still do not know the cause of these eruptions.

Spitzer's infrared picture at left hand side of figure 1, reveals fine dust particles that make up the outer shell, or coma, of the comet. The nucleus of the comet is within the bright whitish spot in the center, while the yellow area shows solid particles that were blown from the comet in the explosion. The comet is headed away from the sun, which lies beyond the right-hand side of figure 1.

The contrast-enhanced picture on the right shows the comet's outer shell, and strange filaments, or streamers, of dust. The streamers and shell are a yet another mystery surrounding comet Holmes. Scientists had initially suspected that the streamers were small dust particles ejected from fragments of the nucleus, or from hyerpactive jets on the nucleus, during the October 2007 explosion. If so, both the streamers and the shell should have shifted their orientation as the comet followed its orbit around the sun. Radiation pressure from the sun should have swept the material back and away from it. But pictures of comet Holmes taken by Spitzer over time show the streamers and shell in the same configuration, and not pointing away from the sun. The observations have left astronomers stumped.

The horizontal line seen in the contrast-enhanced picture is a trail of debris that travels along with the comet in its orbit.

The Spitzer picture was taken with the spacecraft's multiband imaging photometer at an infrared wavelength of 24 microns.

Polarization and studies of evolved star mass loss

NASA Astrophysics Data System (ADS)

Sargent, Benjamin; Srinivasan, Sundar; Riebel, David; Meixner, Margaret

2012-05-01

Polarization studies of astronomical dust have proven very useful in constraining its properties. Such studies are used to constrain the spatial arrangement, shape, composition, and optical properties of astronomical dust grains. Here we explore possible connections between astronomical polarization observations to our studies of mass loss from evolved stars. We are studying evolved star mass loss in the Large Magellanic Cloud (LMC) by using photometry from the Surveying the Agents of a Galaxy's Evolution (SAGE; PI: M. Meixner) Spitzer Space Telescope Legacy program. We use the radiative transfer program 2Dust to create our Grid of Red supergiant and Asymptotic giant branch ModelS (GRAMS), in order to model this mass loss. To model emission of polarized light from evolved stars, however, we appeal to other radiative transfer codes. We probe how polarization observations might be used to constrain the dust shell and dust grain properties of the samples of evolved stars we are studying.

The components of mid- and far-infrared emission from S0 and early-type shell galaxies

NASA Technical Reports Server (NTRS)

Thronson, Harley A., Jr.; Bally, John; Hacking, Perry

1989-01-01

The IRAS database has been used to study detections of about 150 early-type elliptical and S0 galaxies exhibiting a shell structure. No strong evidence for the expected enhancement of either star formation rates or heating of the interstellar medium is found. It is suggested that for some of the sample galaxies either a contribution from warm dust surrounding evolved stars or emission from an active nucleus may be significant.

Observations of emission lines in M supergiants

NASA Technical Reports Server (NTRS)

Lambert, D. L.

1979-01-01

Copernicus observations of Mg 2 h and k emission lines from M giants and supergiants are described. Supergiants with extensive circumstellar gas shells show an asymmetric k line. The asymmetry is ascribed to superimposed lines of Fe 1 and Mn 1. The Mg 2 line width fit the Wilson-Bappu relation derived from observations of G and K Stars. Results of correlated ground-based observations include (1) the discovery of K 1 fluorescent emission from the Betelgeuse shell; (2) extimates of the mass-loss rates; and (3) the proposal that silicate dust grains must account for the major fraction of the Si atoms in the Betelgeuse shell.

Gravitational radiation from a cylindrical naked singularity

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

Nakao, Ken-ichi; Morisawa, Yoshiyuki

We construct an approximate solution which describes the gravitational emission from a naked singularity formed by the gravitational collapse of a cylindrical thick shell composed of dust. The assumed situation is that the collapsing speed of the dust is very large. In this situation, the metric variables are obtained approximately by a kind of linear perturbation analysis in the background Morgan solution which describes the motion of cylindrical null dust. The most important problem in this study is what boundary conditions for metric and matter variables should be imposed at the naked singularity. We find a boundary condition that allmore » the metric and matter variables are everywhere finite at least up to the first order approximation. This implies that the spacetime singularity formed by this high-speed dust collapse is very similar to that formed by the null dust and the final singularity will be a conical one. Weyl curvature is completely released from the collapsed dust.« less

Dying Star Creates Fantasy-like Sculpture of Gas and Dust

NASA Image and Video Library

2004-09-09

This detailed view of NGC 6543, the Cat Eye Nebula, from NASA Hubble Space Telescope includes intricate structures, including concentric gas shells, jets of high-speed gas, and unusual shock-induced knots of gas.

Mixing states of aerosols over four environmentally distinct atmospheric regimes in Asia: coastal, urban, and industrial locations influenced by dust.

PubMed

Ramachandran, S; Srivastava, Rohit

2016-06-01

Mixing can influence the optical, physical, and chemical characteristics of aerosols, which in turn can modify their life cycle and radiative effects. Assumptions on the mixing state can lead to uncertain estimates of aerosol radiative effects. To examine the effect of mixing on the aerosol characteristics, and their influence on radiative effects, aerosol mixing states are determined over four environmentally distinct locations (Karachi, Gwangju, Osaka, and Singapore) in Asia, an aerosol hot spot region, using measured spectral aerosol optical properties and optical properties model. Aerosol optical depth (AOD), single scattering albedo (SSA), and asymmetry parameter (g) exhibit spectral, spatial, and temporal variations. Aerosol mixing states exhibit large spatial and temporal variations consistent with aerosol characteristics and aerosol type over each location. External mixing of aerosol species is unable to reproduce measured SSA over Asia, thus providing a strong evidence that aerosols exist in mixed state. Mineral dust (MD) (core)-Black carbon (BC) (shell) is one of the most preferred aerosol mixing states. Over locations influenced by biomass burning aerosols, BC (core)-water soluble (WS, shell) is a preferred mixing state, while dust gets coated by anthropogenic aerosols (BC, WS) over urban regions influenced by dust. MD (core)-sea salt (shell) mixing is found over Gwangju corroborating the observations. Aerosol radiative forcing exhibits large seasonal and spatial variations consistent with features seen in aerosol optical properties and mixing states. TOA forcing is less negative/positive for external mixing scenario because of lower SSA. Aerosol radiative forcing in Karachi is a factor of 2 higher when compared to Gwangju, Osaka, and Singapore. The influence of g on aerosol radiative forcing is insignificant. Results emphasize that rather than prescribing one single aerosol mixing state in global climate models regionally and temporally varying aerosol mixing states should be included for more accurate assessment of aerosol radiative effects.

Valorization of aquaculture waste in removal of cadmium from aqueous solution: optimization by kinetics and ANN analysis

NASA Astrophysics Data System (ADS)

Aditya, Gautam; Hossain, Asif

2018-05-01

Cadmium is one of the most hazardous heavy metal concerning human health and aquatic pollution. The removal of cadmium through biosorption is a feasible option for restoration of the ecosystem health of the contaminated freshwater ecosystems. In compliance with this proposition and considering the efficiency of calcium carbonate as biosorbent, the shell dust of the economically important snail Bellamya bengalensis was tested for the removal of cadmium from aqueous medium. Following use of the flesh as a cheap source of protein, the shells of B. bengalensis made up of CaCO3 are discarded as aquaculture waste. The biosorption was assessed through batch sorption studies along with studies to characterize the morphology and surface structures of waste shell dust. The data on the biosorption were subjected to the artificial neural network (ANN) model for optimization of the process. The biosorption process changed as functions of pH of the solution, concentration of heavy metal, biomass of the adsorbent and time of exposure. The kinetic process was well represented by pseudo second order ( R 2 = 0.998), and Langmuir equilibrium ( R 2 = 0.995) had better fits in the equilibrium process with 30.33 mg g-1 of maximum sorption capacity. The regression equation ( R 2 = 0.948) in the ANN model supports predicted values of Cd removal satisfactorily. The normalized importance analysis in ANN predicts Cd2+ concentration, and pH has the most influence in removal than biomass dose and time. The SEM and EDX studies show clear peaks for Cd confirming the biosorption process while the FTIR study depicts the main functional groups (-OH, C-H, C=O, C=C) responsible for the biosorption process. The study indicated that the waste shell dust can be used as an efficient, low cost, environment friendly, sustainable adsorbent for the removal of cadmium from aqueous solution.

THE MASS-LOSS RETURN FROM EVOLVED STARS TO THE LARGE MAGELLANIC CLOUD. VI. LUMINOSITIES AND MASS-LOSS RATES ON POPULATION SCALES

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

Riebel, D.; Meixner, M.; Srinivasan, S.

We present results from the first application of the Grid of Red Supergiant and Asymptotic Giant Branch ModelS (GRAMS) model grid to the entire evolved stellar population of the Large Magellanic Cloud (LMC). GRAMS is a pre-computed grid of 80,843 radiative transfer models of evolved stars and circumstellar dust shells composed of either silicate or carbonaceous dust. We fit GRAMS models to {approx}30,000 asymptotic giant branch (AGB) and red supergiant (RSG) stars in the LMC, using 12 bands of photometry from the optical to the mid-infrared. Our published data set consists of thousands of evolved stars with individually determined evolutionarymore » parameters such as luminosity and mass-loss rate. The GRAMS grid has a greater than 80% accuracy rate discriminating between oxygen- and carbon-rich chemistry. The global dust injection rate to the interstellar medium (ISM) of the LMC from RSGs and AGB stars is on the order of 2.1 Multiplication-Sign 10{sup -5} M{sub Sun} yr{sup -1}, equivalent to a total mass injection rate (including the gas) into the ISM of {approx}6 Multiplication-Sign 10{sup -3} M{sub Sun} yr{sup -1}. Carbon stars inject two and a half times as much dust into the ISM as do O-rich AGB stars, but the same amount of mass. We determine a bolometric correction factor for C-rich AGB stars in the K{sub s} band as a function of J - K{sub s} color, BC{sub K{sub s}}= -0.40(J-K{sub s}){sup 2} + 1.83(J-K{sub s}) + 1.29. We determine several IR color proxies for the dust mass-loss rate (M-dot{sub d}) from C-rich AGB stars, such as log M-dot{sub d} = (-18.90/((K{sub s}-[8.0])+3.37) - 5.93. We find that a larger fraction of AGB stars exhibiting the 'long-secondary period' phenomenon are more O-rich than stars dominated by radial pulsations, and AGB stars without detectable mass loss do not appear on either the first-overtone or fundamental-mode pulsation sequences.« less

Columbia University Participation in the Infrared Space Observatory (ISO) Guest Obs. Program: Evolution of Near-Infrared Lines from the Formation of Supernova Remnant 1987A

NASA Technical Reports Server (NTRS)

Crotts, Arlin P. S.

2000-01-01

The goal of this project is to determine the mass loss history of a sample of seven mass losing Asymptotic Giant Branch stars. This is done by observing their circumstellar dust shells which contain a record of the most recent mass loss history. The further away from the star we are able to detect this increasingly fainter dust emission the further back we can look into the mass loss history.

The Charged Aerosol Release Experiment (CARE)

NASA Astrophysics Data System (ADS)

Bernhardt, P. A.; Ganguli, G.; Lampe, M.; Scales, W. A.

2005-12-01

The physics of radar scatter from charged particulates in the upper atmosphere will be studied with the Charged Aerosol Release Experiment (CARE). In 2008, two rocket payloads are being designed for launch North America. The purpose of the CARE program is to identify the mechanisms for radar scatter from polar mesospheric clouds. Polar mesospheric summer echoes (PMSE) are observed at high latitudes when small concentrations of electrons (one-thousand per cubic cm) become attached to sub-micron dust particles. Radar in the VHF (30-300 MHz) frequency range have seen 30 dB enhancements in radar echoes coincident with formation of ice near 85 km altitude. Radar echoes from electrons in the vicinity of charged dust have been observed for frequencies exceeding 1 GHz. Some fundamental questions that remain about the scatting process are: (1) What is the relative importance of turbulent scatter versus incoherent (i.e., Thompson) scatter from individual electrons? (2) What produces the inhomogeneous electron/dust plasma? (3) How is the radar scatter influenced by the density of background electrons, plasma instabilities and turbulence, and photo detachment of electrons from the particulates? These questions will be addressed when the CARE program releases 50 kg of dust particles in an expanding shell at about 300 km altitude. The dust will be manufactured by the chemical release payload to provide particulate sizes in the 10 to 1000 nm range. The expanding dust shell will collect electrons making dense, heavy particles the move the negative charges across magnetic field lines. Plasma turbulence and electron acceleration will be formed from the charge separation between the magnetized oxygen ions in the background ionosphere and the streaming negatively charged dust. Simulations of this process provide estimates of plasma structure which can scatter radar. As the particulates settle through the lower thermosphere into the mesosphere, artificial mesospheric clouds will be formed. Radar scatter form this artificial layer will be compared with natural PMSE observations. Along with the chemical release rocket, in situ probes with a separate instrumented payload will be used to measure dust density, electric fields, plasma density and velocity, and radio wave scattering.

Infrared Measurements of AFGL (Air Force Geophysics Laboratory) Sources.

DTIC Science & Technology

1983-06-07

of sources brighter than magnitude [ X ] is plotted against [ X ] in figures 3 and 4. The LL source counts are plotted as dots in these two figu re s. From...radiation is from, a cir- cumstellar dust shell. The characteristic temperature of these shells 21 *~** * * ** X ...scale height. We find: N([4)) = 3 x 10 -7 pc -3 and N(L1Q]) = 9 x 10 .8 pc 3 . Kirton and Fitzgerald (1974) found the density of late M stars (M5-9) to

Ejecta of Eta Carinae: What We Learn about N-Rich Chemistry

NASA Technical Reports Server (NTRS)

Gull, Theodore

2006-01-01

At least one member of the binary system, Eta Carinae, is in the late stages of CNO-cycle. At least ten solar masses of ejecta make up the Homunculus, a neutral bi-polar shell ejected in the 1840s and the Little Homunculus, an internal, ionized bi-polar shell ejected in the 1890s. HST/STIS and VLTAJVES high dispersion spectroscopy revealed absorptions of multiple elements and diatomic molecules in these shells, some, such as V II and Sr II have not been seen previously in the ISM. The skirt region between the bi-lobes includes the very bright Weigelt blobs, within 0.1 to 0.3" of the central source, and the more distant, unusual Strontium Filament, a neutral emission nebula photoexcited by Balmer continuum, but shielded by Fe II from Lyman radiation. The 600+ emission lines are due to metals usually tied up in dust, but underabundances of C and O prevent precipitation as oxides onto the dust grains. Indications are that Ti/Ni is 100X solar, likely due not to nuclear processing, but the very different photo-excitation environments coupled with N-rich, C-, O-poor chemistry. In the Homunculus, level populations of the molecules indicate 60K gas; the metal absorption lines, 760K; that of the Little Homunculus 6400K during the broad spectroscopic maximum, relaxing to 5000K for the few month long minimum. Lyman radiation, including both continuum and Lyman lines, is trapped across periastron. leading to temporary relaxation of the ejecta. These ejecta are a treasure trove of information on material thrown out of massive stars in the CNO-cycle, well before the helium burning phase. Curiously, spectra of three very recent SWIFT GRBs indicate the presence of warm, photoexcited ejecta in the vicinity of the protoGRBs, but obviously of very different abundances. However, the ejecta of Eta Carinae promise to be a nearby example of massive ejecta, the study of which should lead to increased insight of earlier, very distant massive stars.

Identification of Ice Nucleation Active Sites on Feldspar Dust Particles

PubMed Central

2015-01-01

Mineral dusts originating from Earth’s crust are known to be important atmospheric ice nuclei. In agreement with earlier studies, feldspar was found as the most active of the tested natural mineral dusts. Here we investigated in closer detail the reasons for its activity and the difference in the activity of the different feldspars. Conclusions are drawn from scanning electron microscopy, X-ray powder diffraction, infrared spectroscopy, and oil-immersion freezing experiments. K-feldspar showed by far the highest ice nucleation activity. Finally, we give a potential explanation of this effect, finding alkali-metal ions having different hydration shells and thus an influence on the ice nucleation activity of feldspar surfaces. PMID:25584435

A polarimetric survey of symbiotic stars

NASA Technical Reports Server (NTRS)

Schulte-Ladbeck, R. E.; Aspin, C.; Magalhaes, A. M.; Schwarz, H. E.

1990-01-01

Optical and near-infrared polarization observations of 24 symbiotic stars, 14 observed with polarimetry for the first time are presented. In combination with published data, it is found that about 50 percent of the symbiotics observed polarimetrically show evidence for intrinsic polarization. The results are discussed in the light of previous observations, and comments are made on the temporal variability and wavelength dependence of the polarization. Dust scattering is identified as the dominant mechanism producing polarization in symbiotic stars. While it cannot be excluded that some symbiotic systems are completely engulfed in their dust shells, the data indicate that the H-alpha emission line may originate from outside of the dust-scattering envelopes in some systems.

Propierties of dust in circumstellar gas around Wolf-Rayet stars

NASA Astrophysics Data System (ADS)

Jiménez-Hernández, P.; Arthur, S. J.; Toalá, J. A.

2017-11-01

Using archive photometric observations from Herschel (70μm, 100μm, 160μm and 250μm), Spitzer (24μm) and WISE (22μm and 12μm) we obtained infrared SED's of nebulae around the Wolf-Rayet stars WR 124, WR 16 and WR 7. We used the photoionization code Cloudy to construct models of the nebulae, taking into account the spectrum of the central star and varying the density and distance of the photoionized shell as well as the size distribution and chemical composition of the dust grains mixed with the gas, and we compared the resulting SEDs with the observations in order to study the properties of the dust in these objects. We discuss whether the dust properties depend on the spectral type of the central star and the age of the nebulae.

The chromosphere of VV cephei and the distribution of circumstellar dust around red giants and supergiants

NASA Technical Reports Server (NTRS)

Bauer, Wendy Hagen

1992-01-01

The work on this project has followed two separate paths of inquiry. The first project was entitled 'the Chromosphere of VV Cephei.' The examination of the archival spectra revealed significant changes in the spectra. Therefore, we obtained additional observing time with IUE to monitor the system during the summer of 1991. Short-term changes continue to be seen in both the overall spectrum and individual line profiles. Work continues on this object. The second project was entitled 'the Distribution of Circumstellar Dust around Red Giants and Supergiants.' A number of cool evolved stars are surrounded by dust shells of sufficient angular size as to appear extended in the IRAS survey data. The aim of this project has been to convolve the predictions of the flux distribution from model dust shells with the IRAS beam profiles in order to reproduce the observed IRAS scans. At the time of the last status report, the cross-scan profiles of the IRAS detectors had just been added to the modeling procedure. For scans in which the star passed near the detector center, there was no significant variation in predicted scan profile for different detectors. Scans in which the detector did not pass over the bright central star had been anticipated to be particularly useful in determining the dust distribution; however, significant differences in the predicted scan profiles were seen for different detector profiles. For this reason, and due to the cross-talk effects discussed in the previous status report, further work on the scans not including a central star has been postponed in favor of further analysis of scans passing over the central star.

The Mass-loss Return from Evolved Stars to the Large Magellanic Cloud. IV. Construction and Validation of a Grid of Models for Oxygen-rich AGB Stars, Red Supergiants, and Extreme AGB Stars

NASA Astrophysics Data System (ADS)

Sargent, Benjamin A.; Srinivasan, S.; Meixner, M.

2011-02-01

To measure the mass loss from dusty oxygen-rich (O-rich) evolved stars in the Large Magellanic Cloud (LMC), we have constructed a grid of models of spherically symmetric dust shells around stars with constant mass-loss rates using 2Dust. These models will constitute the O-rich model part of the "Grid of Red supergiant and Asymptotic giant branch star ModelS" (GRAMS). This model grid explores four parameters—stellar effective temperature from 2100 K to 4700 K luminosity from 103 to 106 L sun; dust shell inner radii of 3, 7, 11, and 15 R star; and 10.0 μm optical depth from 10-4 to 26. From an initial grid of ~1200 2Dust models, we create a larger grid of ~69,000 models by scaling to cover the luminosity range required by the data. These models are available online to the public. The matching in color-magnitude diagrams and color-color diagrams to observed O-rich asymptotic giant branch (AGB) and red supergiant (RSG) candidate stars from the SAGE and SAGE-Spec LMC samples and a small sample of OH/IR stars is generally very good. The extreme AGB star candidates from SAGE are more consistent with carbon-rich (C-rich) than O-rich dust composition. Our model grid suggests lower limits to the mid-infrared colors of the dustiest AGB stars for which the chemistry could be O-rich. Finally, the fitting of GRAMS models to spectral energy distributions of sources fit by other studies provides additional verification of our grid and anticipates future, more expansive efforts.

Properties and evolution of dust in the interstellar medium.

NASA Astrophysics Data System (ADS)

Flagey, N.

2007-10-01

My thesis is dedicated to the properties and evolution of the dust in the Galactic interstellar medium (ISM), particularly the small sizes end of the dust size distribution. Throughout these three years, new infrared (IR) observations provided by the Spitzer Space Telescope helped me to bring my own contribution to the knowledge of the dust lifecycle. In order to get a view as global as possible, I have studied three different interstellar environments : the diffuse Galactic medium, a molecular cloud and a star forming region. I analyzed one line of sight that points towards the diffuse Galactic ISM, away from bright star forming regions. Combining spectroscopic and photometric data, I have built a mean Galactic near to mid IR spectrum of the dust, that I have afterwards used as a reference. The Polycyclic Aromatic Hydrocarbons (PAHs) bands are present on top of a continuum. In order to interpret the band intensity ratios in terms of PAHs size and ionization state, I have updated our dust model so that it takes into account the size dependent ionization state of the PAHs. The diffuse ISM spectrum is fit for a PAH mean size of about 60 carbon atoms and a cation fraction of about 40%. Molecular size and charged PAHs are thus present within the diffuse medium. A 3-5 μm continuum, first detected in reflection nebulae, is observed to be present in the diffuse ISM emission. This continuum accounts for 70% of the emission in the Spitzer/IRAC 3.6μm filter. Its origin is still unknown. I show that it is neither scattered light nor PAH fluorescence, as this process would require a photon conversion efficiency above 100%. I used Spitzer observations to quantify spatial variations of PAHs properties across the galaxy and on small scales within the Taurus molecular cloud. Analysis of a set of Galactic diffuse ISM sight lines show that the PAHs mean size exhibits significant dispersion, from 40 to 80 carbon atoms, while their ionization fraction stays constant within error bars. I have also analyzed mid and far-IR Spitzer images of the Taurus Molecular Cloud. Each dust component (PAHs, VSGs for Very Small Grains and BGs for Big Grains) can be related to one Spitzer channel (IRAC 8, MIPS 24 and MIPS 160 microns). A first difficulty was to obtain images of the low brightness diffuse emission across the entire cloud. I worked with Spitzer Science Center (SSC) experts to produce the IRAC 8 and MIPS 24 images. For the MIPS 160 I used an inversion algorithm developed to destripe the data. I validated the photometry of each image. The observations show that PAHs are present within a surface layer thinn! er than that penetrated by ultraviolet photons and that of VSGs emission. Such variations cannot be only explained by the extinction and must thus trace real PAH depletion within dense gas where the smallest dust particles may stick on large grains and/or coagulate. During my PhD thesis, I applied for a SSC Visiting Graduate Student grant in order to study the Eagle Nebula (M16), the object that made me decide to do astrophysics, more than ten years ago, when the Hubble Space Telescope imaged the iconic Pillars of Creation. My application was accepted and I spent 6 months within the MIPSGAL Science Team. My aim was to combine IRAC and MIPS data of M16 in order to analyze the properties of the dust within the dusty and gaseous structures, while being involved in the data processing enhancement. The MIPS 24 microns image defines a shell-like structure within the nebula while the pillars are observed at other wavelengths. M16 is a massive star forming region where the dust emission is expected to be powered by the massive stars radiation. However, we show that the UV field is one order of magnitude too small to account for the shell dust temperature. For comparison we analyzed several other Galactic shells. The M16 nebula stands out for having unusually high far-IR color temperature.We considered an alternative interpretation where the dust is heated by gas grain collisions. This interpretation would imply that the shell is a supernova remnant (SNR) about 3000 years old. If confirmed, the Eagle SNR would be the first one detected through dust emission and within a stellar cradle. Moreover, it would illustrate the importance of dust infrared emission within energetics of SNRs. At last, but not at least, the question of the formation and/or destruction of the iconic Pillars of Creation would be (re)opened.

NASA's Great Observatories May Unravel 400-Year Old Supernova Mystery

NASA Astrophysics Data System (ADS)

2004-10-01

Four hundred years ago, sky watchers, including the famous astronomer Johannes Kepler, best known as the discoverer of the laws of planetary motion, were startled by the sudden appearance of a "new star" in the western sky, rivaling the brilliance of the nearby planets. Kepler's Supernova Remnant Multiple Images of Kepler's Supernova Remnant Modern astronomers, using NASA's three orbiting Great Observatories, are unraveling the mysteries of the expanding remains of Kepler's supernova, the last such object seen to explode in our Milky Way galaxy. When a new star appeared Oct. 9, 1604, observers could use only their eyes to study it. The telescope would not be invented for another four years. A team of modern astronomers has the combined abilities of NASA's Great Observatories, the Spitzer Space Telescope (SST), Hubble Space Telescope (HST), and Chandra X-ray Observatory, to analyze the remains in infrared radiation, visible light, and X-rays. Ravi Sankrit and William Blair of the Johns Hopkins University in Baltimore lead the team. The combined image unveils a bubble-shaped shroud of gas and dust, 14 light-years wide and expanding at 4 million mph. Observations from each telescope highlight distinct features of the supernova, a fast-moving shell of iron-rich material, surrounded by an expanding shock wave sweeping up interstellar gas and dust. Interview with Dr. Ravi Sankrit Interview with Dr. Ravi Sankrit "Multi-wavelength studies are absolutely essential for putting together a complete picture of how supernova remnants evolve," Sankrit said. Sankrit is an associate research scientist, Center for Astrophysical Sciences at Hopkins and lead for HST astronomer observations. "For instance, the infrared data are dominated by heated interstellar dust, while optical and X-ray observations sample different temperatures of gas," Blair added. Blair is a research professor, Physics and Astronomy Department at Hopkins and lead astronomer for SST observations. "A range of observations is needed to help us understand the complex relationship that exists among the various components," Blair said. The explosion of a star is a catastrophic event. The blast rips the star apart and unleashes a roughly spherical shock wave that expands outward at more than 22 million mph like an interstellar tsunami. The shock wave spreads out into surrounding space, sweeping up any tenuous interstellar gas and dust into an expanding shell. The stellar ejecta from the explosion initially trail behind the shock wave. It eventually catches up with the inner edge of the shell and is heated to X-ray temperatures. Kepler's Supernova Remnant Hubble Optical Image of Kepler's Supernova Remnant Visible-light images from Hubble's Advanced Camera for Surveys reveal where the supernova shock wave is slamming into the densest regions of surrounding gas. The bright glowing knots are dense clumps that form behind the shock wave. Sankrit and Blair compared their HST observations with those taken with ground-based telescopes to obtain a more accurate distance to the supernova remnant of about 13,000 light-years. Kepler's Supernova Remnant Spitzer Infrared Image of Kepler's Supernova Remnant The astronomers used the SST to probe for material that radiates in infrared light, which shows heated microscopic dust particles that have been swept up by the supernova shock wave. SST is sensitive enough to detect both the densest regions seen by HST and the entire expanding shock wave, a spherical cloud of material. Instruments on SST also reveal information about the chemical composition and physical environment of the expanding clouds of gas and dust ejected into space. This dust is similar to dust which was part of the cloud of dust and gas that formed the sun and planets in our solar system. Interview with Dr. William Blair Interview with Dr. William Blair The Chandra X-ray data show regions of very hot gas. The hottest gas, higher-energy X-rays, is located primarily in the regions directly behind the shock front. These regions also show up in the HST observations and also align with the faint rim of material seen in the SST data. Cooler X-ray gas, lower-energy X-rays, resides in a thick interior shell and marks the location of the material expelled from the exploded star. There have been six known supernovas in our Milky Way over the past 1,000 years. Kepler's is the only one, which astronomers do not know what type of star exploded. By combining information from all three Great Observatories, astronomers may find the clues they need. "It's really a situation where the total is greater than the sum of the parts," Blair said. "When the analysis is complete, we will be able to answer several questions about this enigmatic object." Information and images from this research is available on the Web at: http://www.nasa.gov http://hubblesite.org/newscenter/newsdesk/archive/releases/2004/29/ http://chandra.harvard.edu and http://www.spitzer.caltech.edu/

Senilia senilis (Linnaeus, 1758), a biogenic archive of environmental conditions on the Banc d'Arguin (Mauritania)

NASA Astrophysics Data System (ADS)

Lavaud, Romain; Thébault, Julien; Lorrain, Anne; van der Geest, Matthijs; Chauvaud, Laurent

2013-02-01

Environmental archives are useful tools for describing past and current climate variations and they provide an opportunity to assess the anthropogenic contribution in coastal ecological changes. Along the West African coast, few studies have focused on such archives in coastal ecosystems. The bloody cockle Senilia senilis, an intertidal bivalve mollusk species, is widely distributed from Western Sahara to Angola, and has been harvested by humans over thousands of years. Therefore, this species appears to be a good candidate for assessing past variations of key environmental parameters such as temperature, primary production, and Saharan dust advection within West African coastal ecosystems. In the present paper, we focused (i) on the identification of growth rhythms of S. senilis shells in Mauritania (Banc d'Arguin), and (ii) on the potential of these shells as (paleo-)environmental archives. The method we used combined environmental survey, sclerochronology, and geochemical analyses of aragonite samples. We showed that microgrowth line formation was controlled by a tidal forcing, leading to the formation of two lines per lunar day. Brightness and thickness of these microgrowth lines progressively decreased from spring to neap tides (fortnightly cycle). Lunar daily growth rates displayed strong seasonal variations, with highest values (> 300 μm per lunar day) recorded in summer. The oxygen isotope composition of S. senilis shells (δ18Oaragonite) accurately tracked seawater temperature seasonal variations, with a precision of 0.8 °C. Finally, we discussed the opportunity to use Ba:Ca ratio in shells as a proxy for primary production or for Saharan dust transport. We also hypothesized that either Canary Currentvariations or, more probably, massive aerosol transfers from Sahara to the Atlantic Ocean could control uranium availability in coastal waters and explain the occurrence of U:Ca peaks within S. senilis shells.

Absorption and scattering properties of the Martian dust in the solar wavelengths.

PubMed

Ockert-Bell, M E; Bell JF 3rd; Pollack, J B; McKay, C P; Forget, F

1997-04-25

A new wavelength-dependent model of the single-scattering properties of the Martian dust is presented. The model encompasses the solar wavelengths (0.3 to 4.3 micrometers at 0.02 micrometer resolution) and does not assume a particular mineralogical composition of the particles. We use the particle size distribution, shape, and single-scattering properties at Viking Lander wavelengths presented by Pollack et al. [1995]. We expand the wavelength range of the aerosol model by assuming that the atmospheric dust complex index of refraction is the same as that of dust particles in the bright surface geologic units. The new wavelength-dependent model is compared to observations taken by the Viking Orbiter Infrared Thermal Mapper solar channel instrument during two dust storms. The model accurately matches afternoon observations and some morning observations. Some of the early morning observations are much brighter than the model results. The increased reflectance can be ascribed to the formation of a water ice shell around the dust particles, thus creating the water ice clouds which Colburn et al. [1989], among others, have predicted.

Mapping the three-dimensional dust extinction towards the supernova remnant S147 - the S147 dust cloud

NASA Astrophysics Data System (ADS)

Chen, B.-Q.; Liu, X.-W.; Ren, J.-J.; Yuan, H.-B.; Huang, Y.; Yu, B.; Xiang, M.-S.; Wang, C.; Tian, Z.-J.; Zhang, H.-W.

2017-12-01

We present a three-dimensional (3D) extinction analysis in the region towards the supernova remnant (SNR) S147 (G180.0-1.7) using multiband photometric data from the Xuyi Schmidt Telescope Photometric Survey of the Galactic Anticentre (XSTPS-GAC), 2MASS and WISE. We isolate a previously unrecognized dust structure likely to be associated with SNR S147. The structure, which we term as 'S147 dust cloud', is estimated to have a distance d = 1.22 ± 0.21 kpc, consistent with the conjecture that S147 is associated with pulsar PSR J0538 + 2817. The cloud includes several dense clumps of relatively high extinction that locate on the radio shell of S147 and coincide spatially with the CO and gamma-ray emission features. We conclude that the usage of CO measurements to trace the SNR associated MCs is unavoidably limited by the detection threshold, dust depletion and the difficulty of distance estimates in the outer Galaxy. 3D dust extinction mapping may provide a better way to identify and study SNR-MC interactions.

The mid-infrared diameter of W Hydrae

NASA Astrophysics Data System (ADS)

Zhao-Geisler, R.; Quirrenbach, A.; Köhler, R.; Lopez, B.; Leinert, C.

2011-06-01

Aims: Asymptotic giant branch (AGB) stars are among the largest distributors of dust into the interstellar medium, and it is therefore important to understand the dust formation process and sequence in their strongly pulsating extended atmosphere. By monitoring the AGB star W Hya interferometrically over a few pulsations cycles, the upper atmospheric layers can be studied to obtain information on their chemical gas and dust composition and their intracycle and cycle-to-cycle behavior. Methods: Mid-infrared (8-13 μm) interferometric data of W Hya were obtained with MIDI/VLTI between April 2007 and September 2009, covering nearly three pulsation cycles. The spectrally dispersed visibility data of all 75 observations were analyzed by fitting a circular fully limb-darkened disk (FDD) model to all data and individual pulsation phases. Asymmetries were studied with an elliptical FDD. Results: Modeling results in an apparent angular FDD diameter of W Hya of about (80 ± 1.2) mas (7.8 AU) between 8 and 10 μm, which corresponds to an about 1.9 times larger diameter than the photospheric one. The diameter gradually increases up to (105 ± 1.2) mas (10.3 AU) at 12 μm. In contrast, the FDD relative flux fraction decreases from (0.85 ± 0.02) to (0.77 ± 0.02), reflecting the increased flux contribution from a fully resolved surrounding silicate dust shell. The asymmetric character of the extended structure could be confirmed. An elliptical FDD yields a position angle of (11 ± 20)° and an axis ratio of (0.87 ± 0.07). A weak pulsation dependency is revealed with a diameter increase of (5.4 ± 1.8) mas between visual minimum and maximum, while detected cycle-to-cycle variations are smaller. Conclusions: W Hya's diameter shows a behavior that is very similar to the Mira stars RR Sco and S Ori and can be described by an analogous model. The constant diameter part results from a partially resolved stellar disk, including a close molecular layer of H2O, while the increase beyond 10 μm can most likely be attributed to the contribution of a spatially resolved nearby Al2O3 dust shell. Probably due to the low mass-loss rate, close Fe-free silicate dust could not be detected. The results suggest that the formation of amorphous Al2O3 occurs mainly at visual minimum. A possible close Al2O3 dust shell has now been revealed in a few objects calling for self-consistent dynamic atmospheric models including dust formation close to the star. The asymmetry might be explained by an enhanced dust concentration along an N-S axis. Based on observations made with the Very Large Telescope Interferometer (VLTI) at the Paranal Observatory under program IDs 079.D-0140, 080.D-0005, 081.D-0198, 082.D-0641 and 083.D-0294.FITS files of the calibrated visibilities are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/530/A120

Molecular gas associated with IRAS 10361-5830

NASA Astrophysics Data System (ADS)

Vazzano, M. M.; Cappa, C. E.; Vasquez, J.; Rubio, M.; Romero, G. A.

2014-10-01

Aims: We analyze the distribution of the molecular gas and dust in the molecular clump linked to IRAS 10361-5830, located in the environs of the bubble-shaped Hii region Gum 31 in the Carina region, with the aim of determining the main parameters of the associated material and of investigating the evolutionary state of the young stellar objects identified there. Methods: Using the APEX telescope, we mapped the molecular emission in the J = 3-2 transition of three CO isotopologues, 12CO, 13CO and C18O, over a 1.´5 × 1.´5 region around the IRAS position. We also observed the high-density tracers CS and HCO+ toward the source. The cold- dust distribution was analyzed using submillimeter continuum data at 870 μm obtained with the APEX telescope. Complementary IR and radio data at different wavelengths were used to complete the study of the interstellar medium. Results: The molecular gas distribution reveals a cavity and a shell-like structure of ~0.32 pc in radius centered at the position of the IRAS source, with some young stellar objects projected onto the cavity. The total molecular mass in the shell and the mean H2volume density are ~40 M⊙ and ~(1-2) × 103 cm-3. The cold-dust counterpart of the molecular shell has been detected in the far-IR at 870 μm and in Herschel data at 350 μm. Weak extended emission at 24 μm from warm dust is projected onto the cavity, as well as weak radio continuum emission. Conclusions: A comparison of the distribution of cold and warm dust, and molecular and ionized gas allows us to conclude that a compact Hii region has developed in the molecular clump, indicating that this is an area of recent massive star formation. Probable exciting sources capable of creating the compact Hii region are investigated. The 2MASS source 10380461-5846233 (MSX G286.3773-00.2563) seems to be responsible for the formation of the Hii region. FITS files with datacubes corresponding to 12CO, 13CO, C180 maps are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/570/A109

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 suggest that the warm and cool dust components represent grain species produced in diffuse SN ejecta and in dense ejecta clumps, respectively

Cosmic dust-ion-acoustic waves, spherical modified Kadomtsev-Petviashvili model, and symbolic computation

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

Gao Yitian; Tian Bo; State Key Laboratory of Software Development Environment, Beijing University of Aeronautics and Astronautics, Beijing 100083

2006-11-15

The spherical modified Kadomtsev-Petviashvili (smKP) model is hereby derived with symbolic computation for the dust-ion-acoustic waves with zenith-angle perturbation in a cosmic dusty plasma. Formation and properties of both dark and bright smKP nebulons are obtained and discussed. The relevance of those smKP nebulons to the supernova shells and Saturn's F-ring is pointed out, and possibly observable nebulonic effects for the future cosmic plasma experiments are proposed. The difference of the smKP nebulons from other types of nebulons is also analyzed.

Pinwheel Nebula around WR 98a.

PubMed

Monnier; Tuthill; Danchi

1999-11-10

We present the first near-infrared images of the dusty Wolf-Rayet star WR 98a. Aperture-masking interferometry has been utilized to recover images at the diffraction limit of the Keck I telescope, less, similar50 mas at 2.2 µm. Multiepoch observations spanning about 1 yr have resolved the dust shell into a "pinwheel" nebula, the second example of a new class of dust shell first discovered around WR 104 by Tuthill, Monnier, & Danchi. Interpreting the collimated dust outflow in terms of an interacting winds model, the binary orbital parameters and apparent wind speed are derived: a period of 565+/-50 days, a viewing angle of 35&j0;+/-6 degrees from the pole, and a wind speed of 99+/-23 mas yr-1. This period is consistent with a possible approximately 588 day periodicity in the infrared light curve, linking the photometric variation to the binary orbit. Important implications for binary stellar evolution are discussed by identifying WR 104 and WR 98a as members of a class of massive, short-period binaries whose orbits were circularized during a previous red supergiant phase. The current component separation in each system is similar to the diameter of a red supergiant, which indicates that the supergiant phase was likely terminated by Roche lobe overflow, leading to the present Wolf-Rayet stage.

Infrared circumstellar shells - Origins, and clues to the evolution of massive stars

NASA Technical Reports Server (NTRS)

Stencel, Robert E.; Pesce, Joseph E.; Bauer, Wendy Hagen

1989-01-01

The infrared fluxes, spatial and spectral characteristics for a sample of 111 supergiant stars of spectral types F0 through M5 are tabulated, and correlations examined with respect to the nature of their circumstellar envelopes. One-fourth of these objects were spatialy resolved by IRAS at 60 microns and possess extended circumstellar shell material, with implied expansion ages of about 10 to the 5th yr. Inferences about the production of dust, mass loss, and the relation of these characteristics of the evolution of massive stars, are discussed.

The Mira Variable S Orionis: Relationships Between the Photosphere, Molecular Layer, Dust Shell, and SiO Maser Shell at 4 Epochs

DTIC Science & Technology

2007-01-01

C ., Gray, M. D., Humphreys, E. M. L ., Braithwaite, M. F ., & Field, D. 1995, A & A , 302, 797 Feast, M. W., Glass, I. S., Whitelock, P. A ., & Catchpole... C ., Bester, M., Degiacomi, C . G., Greenhill, L . J., & Townes, C . H. 1994, AJ, 107, 1469 Desmurs, J. F ., Bujarrabal, V., Colomer, F ., & Alcolea, J...2003, Proc. SPIE, 4838, 89 Gray, M. D., & Humphreys, E. M. L . 2000, New Astron., 5, 155 Haniff, C . A ., Scholz, M., & Tuthill,

Comet Hartley 2 Gets a Visitor Artist Concept

NASA Image and Video Library

2010-10-26

This artist concept shows a view of NASA EPOXI mission spacecraft during its Nov. 4, 2010 flyby of comet Hartley 2. The fluffy shell around the comet, called a coma, is made up of gas and dust that blew off the comet core, or nucleus.

Dust formation at low metallicity

NASA Astrophysics Data System (ADS)

Ferrarotti, A. S.; Gail, H.-P.

Stars between 3Modot and 25Modot reach their final stages of stellar evolution either as AGB (asymptotic giant branch) stars and finally become white dwarfs, or end in a supernova explosion. The last evolutionary stages, shortly before the final state, are regularly accompanied by stellar winds which lead to substantial mass loss and develop optically very thick dust shells. Mass loss for smaller and medium sized stars higher up on the AGB depends predominantly on the metallicity of the star. For Pop I metallicity, the mass loss is caused by dust condensation. This process is not possible for stars of small Z. Thus, their final evolution strongly depends on the possibility of dust formation. Our research focuses on the dependence of dust formation of the first stellar generation on Z and on the initial mass of the star. Furthermore, we investigate when dust formation becomes possible in stellar winds and the effects this process has on the evolution of the star at the final evolutionary stages. With synthetic AGB evolution models some important issues in stellar evolution can tried to be answered: (1) mass loss on the AGB, (2) the shift of the limit (γ>1) for the onset of dust driven winds with Z and (3) the critical Z when dust formation becomes possible.

Chronicle of a Death Foretold

NASA Astrophysics Data System (ADS)

2007-05-01

Using ESO's VLTI on Cerro Paranal and the VLBA facility operated by NRAO, an international team of astronomers has made what is arguably the most detailed study of the environment of a pulsating red giant star. They performed, for the first time, a series of coordinated observations of three separate layers within the star's tenuous outer envelope: the molecular shell, the dust shell, and the maser shell, leading to significant progress in our understanding of the mechanism of how, before dying, evolved stars lose mass and return it to the interstellar medium. S Orionis (S Ori) belongs to the class of Mira-type variable stars. It is a solar-mass star that, as will be the fate of our Sun in 5 billion years, is nearing its gloomy end as a white dwarf. Mira stars are very large and lose huge amounts of matter. Every year, S Ori ejects as much as the equivalent of Earth's mass into the cosmos. ESO PR Photo 25a/07 ESO PR Photo 25a/07 Evolution of the Mira-type Star S Orionis "Because we are all stardust, studying the phases in the life of a star when processed matter is sent back to the interstellar medium to be used for the next generation of stars, planets... and humans, is very important," said Markus Wittkowski, lead author of the paper reporting the results. A star such as the Sun will lose between a third and half of its mass during the Mira phase. S Ori pulsates with a period of 420 days. In the course of its cycle, it changes its brightness by a factor of the order of 500, while its diameter varies by about 20%. Although such stars are enormous - they are typically larger than the current Sun by a factor of a few hundred, i.e. they encompass the orbit of the Earth around the Sun - they are also distant and to peer into their deep envelopes requires very high resolution. This can only be achieved with interferometric techniques. ESO PR Photo 25b/07 ESO PR Photo 25b/07 Structure of S Ori (Artist's Impression) "Astronomers are like medical doctors, who use various instruments to examine different parts of the human body," said co-author David Boboltz. "While the mouth can be checked with a simple light, a stethoscope is required to listen to the heart beat. Similarly the heart of the star can be observed in the optical, the molecular and dust layers can be studied in the infrared and the maser emission can be probed with radio instruments. Only the combination of the three gives us a more complete picture of the star and its envelope." The maser emission comes from silicon monoxide (SiO) molecules and can be used to image and track the motion of gas clouds in the stellar envelope roughly 10 times the size of the Sun. The astronomers observed S Ori with two of the largest interferometric facilities available: the ESO Very Large Telescope Interferometer (VLTI) at Paranal, observing in the near- and mid-infrared, and the NRAO-operated Very Long Baseline Array (VLBA), that takes measurements in the radio wave domain. Because the star's luminosity changes periodically, the astronomers observed it simultaneously with both instruments, at several different epochs. The first epoch occurred close to the stellar minimum luminosity and the last just after the maximum on the next cycle. ESO PR Photo 25c/07 ESO PR Photo 25c/07 S Ori to Scale (Artist's Impression) The astronomers found the star's diameter to vary between 7.9 milliarcseconds and 9.7 milliarcseconds. At the distance of S Ori, this corresponds to a change of the radius from about 1.9 to 2.3 times the distance between the Earth and the Sun, or between 400 and 500 solar radii! As if such sizes were not enough, the inner dust shell is found to be about twice as big. The maser spots, which also form at about twice the radius of the star, show the typical structure of partial to full rings with a clumpy distribution. Their velocities indicate that the gas is expanding radially, moving away at a speed of about 10 km/s. The multi-wavelength analysis indicates that near the minimum there is more dust production and mass ejection: in these phases indeed the amount of dust is significantly higher than in the others. After this intense matter production and ejection the star continues its pulsation and when it reaches the maximum luminosity, it displays a much more expanded dust shell. This clearly supports a strong connection between the Mira pulsation and the dust production and expulsion. Furthermore, the astronomers found that grains of aluminum oxide - also called corundum - constitute most of S Ori's dust shell: the grain size is estimated to be of the order of 10 millionths of a centimetre, that is one thousand times smaller than the diameter of a human hair. "We know one chapter of the secret life of a Mira star, but much more can be learned in the near future, when we add near-infrared interferometry with the AMBER instrument on the VLTI to our (already broad) observational approach," said Wittkowski. More Information The research presented here is reported in a paper in press in the journal Astronomy and Astrophysics ("The Mira variable S Ori: Relationships between the photosphere, molecular layer, dust shell, and SiO maser shell at 4 epochs", by M. Wittkowski et al.). It is available in PDF format from the publisher's web site. The team consists of Markus Wittkowski (ESO), David A. Boboltz (U.S. Naval Observatory, USA), Keiichi Ohnaka and Thomas Driebe (MPIfR Bonn, Germany), and Michael Scholz (University of Heidelberg, Germany and University of Sydney, Australia).

Microbiological and meteorological analysis of two Australian dust storms in April 2009.

PubMed

Lim, Natalie; Munday, Chris I; Allison, Gwen E; O'Loingsigh, Tadhg; De Deckker, Patrick; Tapper, Nigel J

2011-12-15

Dust is an important source of bioaerosols including bacteria. In this study, the microbiology and meteorology of specific dust storms in Australia were investigated. The samples were collected from two dust events in April 2009 that were characterised by intense cold fronts that entrained dust from the highly erodible and drought-stricken Mallee and Riverina regions of Victoria and central NSW. In the first storm, the dust travelled eastward over Canberra and Sydney, and in the second storm, the dust travelled east/southeastward over Canberra and Melbourne. Rain fell on both cities during the second dust storm. Dust and rain samples were collected, cultured, and the composition compared using polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE). Multiple bands were evident on DGGE indicative of a diverse microflora, and identification of several bands confirmed the presence of multiple genera and species representing three phyla. Numerous bands represented Bacillus species, and these were present in multiple dust samples collected from both Canberra and Melbourne. Interestingly, the microflora present in rain samples collected in Canberra during the second dust storm was quite different and the DGGE banding patterns from these samples clustered separately to most dust samples collected at the same time. Identification of several DGGE bands and PCR products from these rain samples indicated the presence of Pseudomonas species. These results indicate that Australian dust and rain have a diverse microflora and highlights the contribution of dust events to the distribution of microbes in the environment. Copyright © 2011 Elsevier B.V. All rights reserved.

Role of angular momentum and cosmic censorship in (2+1)-dimensional rotating shell collapse

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

Mann, Robert B.; Oh, John J.; Park, Mu-In

2009-03-15

We study the gravitational collapse problem of rotating shells in three-dimensional Einstein gravity with and without a cosmological constant. Taking the exterior and interior metrics to be those of stationary metrics with asymptotically constant curvature, we solve the equations of motion for the shells from the Darmois-Israel junction conditions in the corotating frame. We study various collapse scenarios with arbitrary angular momentum for a variety of geometric configurations, including anti-de Sitter, de Sitter, and flat spaces. We find that the collapsing shells can form a BTZ black hole, a three-dimensional Kerr-dS spacetime, and an horizonless geometry of point masses undermore » certain initial conditions. For pressureless dust shells, the curvature singularity is not formed due to the angular momentum barrier near the origin. However when the shell pressure is nonvanishing, we find that for all types of shells with polytropic-type equations of state (including the perfect fluid and the generalized Chaplygin gas), collapse to a naked singularity is possible under generic initial conditions. We conclude that in three dimensions angular momentum does not in general guard against violation of cosmic censorship.« less

Experimental observation of self excited co-rotating multiple vortices in a dusty plasma with inhomogeneous plasma background

NASA Astrophysics Data System (ADS)

Choudhary, Mangilal; Mukherjee, S.; Bandyopadhyay, P.

2017-03-01

We report an experimental observation of multiple co-rotating vortices in an extended dust column in the background of an inhomogeneous diffused plasma. An inductively coupled rf discharge is initiated in the background of argon gas in the source region. This plasma was later found to diffuse into the main experimental chamber. A secondary DC glow discharge plasma is produced to introduce dust particles into the plasma volume. These micron-sized poly-disperse dust particles get charged in the background of the DC plasma and are transported by the ambipolar electric field of the diffused plasma. These transported particles are found to be confined in an electrostatic potential well, where the resultant electric field due to the diffused plasma (ambipolar E-field) and glass wall charging (sheath E-field) holds the micron-sized particles against the gravity. Multiple co-rotating (anti-clockwise) dust vortices are observed in the dust cloud for a particular discharge condition. The transition from multiple vortices to a single dust vortex is observed when input rf power is lowered. The occurrence of these vortices is explained on the basis of the charge gradient of dust particles, which is orthogonal to the ion drag force. The charge gradient is a consequence of the plasma inhomogeneity along the dust cloud length. The detailed nature and the reason for multiple vortices are still under investigation through further experiments; however, preliminary qualitative understanding is discussed based on the characteristic scale length of the dust vortex. There is a characteristic size of the vortex in the dusty plasma; therefore, multiple vortices could possibly be formed in an extended dusty plasma with inhomogeneous plasma background. The experimental results on the vortex motion of particles are compared with a theoretical model and are found to be in close agreement.

CSM interaction and dust formation in SN 2010jl .

NASA Astrophysics Data System (ADS)

Krafton, K.; Clayton, G. C.

The origin of dust in galaxies >1 Gyr old has remained an unsolved mystery for over a decade. One proposed solution is dust produced by core collapse supernovae (CCSNe). Theorists have shown that 0.1-1 M⊙ of dust must be produced per supernova for this to work as an explanation for the dust in young galaxies. SN 1987A has produced ˜1 M⊙ of dust since its detonation. However, most supernovae have been found to only produce 10-4 - 10-2 M⊙ of dust. The energetic type IIn SN 2010jl is located in UGC 5189, in a dense shell of CSM. As dust condenses in the SN ejecta, we see, (1) a sudden decrease in continuum brightness in the visible due to increased dust extinction, (2) the development of an infrared excess in the SN light curve arising from dust grains absorbing high-energy photons and re-emitting them in the infrared, and (3) the development of asymmetric, blue-shifted emission-line profiles, caused by dust forming in the ejecta, and preferentially extinguishing redshifted emission. A dense circumstellar material (CSM) may increase the dust production by supernovae. We observe signs of strong interaction between the SN ejecta and a dense CSM in SN 2010jl. SN 2010jl has been a source of much debate in the CCSN community, particularly over when and how much dust it formed. The light curve shows strong signs of dust formation after 260 days. Arguments over these subjects have been based on the evolution of the light curve and spectra. We present new optical and IR photometry, as well as optical spectroscopy, of SN 2010jl over 2000 days. We estimate dust masses using the DAMOCLES and MOCASSIN radiative transfer codes.

High-resolution near-infrared speckle interferometry and radiative transfer modeling of the OH/IR star OH 104.9+2.4

NASA Astrophysics Data System (ADS)

Riechers, D.; Balega, Y.; Driebe, T.; Hofmann, K.-H.; Men'shchikov, A. B.; Weigelt, G.

2004-09-01

We present near-infrared speckle interferometry of the OH/IR star OH 104.9+2.4 in the K' band obtained with the 6 m telescope of the Special Astrophysical Observatory (SAO). At a wavelength of λ = 2.12 μm the diffraction-limited resolution of 74 mas was attained. The reconstructed visibility reveals a spherically symmetric, circumstellar dust shell (CDS) surrounding the central star. The visibility function shows that the stellar contribution to the total flux at λ = 2.12 μm is less than ˜50%, indicating a rather large optical depth of the CDS. The azimuthally averaged 1-dimensional Gaussian visibility fit yields a diameter of 47 ± 3 mas (FHWM), which corresponds to 112 ± 13 AU for an adopted distance of D = 2.38 ± 0.24 kpc. To determine the structure and the properties of the CDS of OH 104.9+2.4, radiative transfer calculations using the code DUSTY were performed to simultaneously model its visibility and the spectral energy distribution (SED). We found that both the ISO spectrum and the visibility of OH 104.9+2.4 can be well reproduced by a radiative transfer model with an effective temperature Teff = 2500 ± 500 K of the central source, a dust temperature Tin = 1000 ± 200 K at the inner shell boundary Rin ≃ 9.1 R* = 25.4 AU, an optical depth τ2.2 μm = 6.5 ± 0.3, and dust g rain radii ranging from amin = 0.005 ± 0.003 μm to amax = 0.2 ± 0.02 μm with a power law n(a) ∝ a-3.5. It was found that even minor changes in amax have a major impact on both the slope and the curvature of the visibility function, while the SED shows only minor changes. Our detailed analysis demonstrates the potential of dust shell modeling constrained by both the SED and visibilities. Based on data collected at the 6 m BTA telescope of the Special Astrophysical Observatory in Russia.

Grain formation around carbon stars. 1: Stationary outflow models

NASA Technical Reports Server (NTRS)

Egan, Michael P.; Leung, Chun Ming

1995-01-01

Asymptotic giant branch (AGB) stars are known to be sites of dust formation and undergo significant mass loss. The outflow is believed to be driven by radiation pressure on grains and momentum coupling between the grains and gas. While the physics of shell dynamics and grain formation are closely coupled, most previous models of circumstellar shells have treated the problem separately. Studies of shell dynamics typically assume the existence of grains needed to drive the outflow, while most grain formation models assume a constant veolcity wind in which grains form. Furthermore, models of grain formation have relied primarily on classical nucleation theory instead of using a more realistic approach based on chemical kinetics. To model grain formation in carbon-rich AGB stars, we have coupled the kinetic equations governing small cluster growth to moment equations which determine the growth of large particles. Phenomenological models assuming stationary outflow are presented to demonstrate the differences between the classical nucleation approach and the kinetic equation method. It is found that classical nucleation theory predicts nucleation at a lower supersaturation ratio than is predicted by the kinetic equations, resulting in significant differences in grain properties. Coagulation of clusters larger than monomers is unimportant for grain formation in high mass-loss models but becomes more important to grain growth in low mass-loss situations. The properties of the dust grains are altered considerably if differential drift velocities are ignored in modeling grain formation. The effect of stellar temperature, stellar luminosity, and different outflow velocities are investigated. The models indicate that changing the stellar temperature while keeping the stellar luminosity constant has little effect on the physical parameters of the dust shell formed. Increasing the stellar luminosity while keeping the stellar temperature constant results in large differences in grain properties. For small outflow velocities, grains form at lower supersaturation ratios and close to the stellar photosphere, resulting in larger but fewer grains. The reverse is true when grains form under high outflow velocities, i.e., they form at higher supersaturation ratios, farther from the star, and are much smaller but at larger quantities.

The close circumstellar environment of the semi-regular S-type star π 1 Gruis

NASA Astrophysics Data System (ADS)

Sacuto, S.; Jorissen, A.; Cruzalèbes, P.; Chesneau, O.; Ohnaka, K.; Quirrenbach, A.; Lopez, B.

2008-05-01

Aims: We study the close circumstellar environment of the nearby S-type star π1 Gruis using high spatial-resolution, mid-infrared observations from the ESO/VLTI. Methods: Spectra and visibilities were obtained with the MIDI interferometer on the VLT Auxiliary Telescopes. The cool M5III giant β Gruis was used as bright primary calibrator, and a dedicated spectro-interferometric study was undertaken to determine its angular diameter accurately. The MIDI measurements were fitted with the 1D numerical radiative transfer code DUSTY to determine the dust shell parameters of π1 Gruis. Taking into account the low spatial extension of the model in the 8-9 μm spectral band for the smallest projected baselines, we consider the possibility of a supplementary molecular shell. Results: The MIDI visibility and phase data are mostly dominated by the spherical 21 mas (694 R_⊙) central star, while the extended dusty environment is over-resolved even with the shortest baselines. No obvious departure from spherical symmetry is found on the milliarcsecond scale. The spectro-interferometric observations are well-fitted by an optically thin (τ_dust<0.01 in the N band) dust shell that is located at about 14 stellar radii with a typical temperature of 700 K and composed of 70% silicate and 30% of amorphous alumina grains. An optically thin (τ_mol<0.1 in the N band) H{2}O + SiO molecular shell extending from the photosphere of the star up to 4.4 stellar radii with a typical temperature of 1000 K is added to the model to improve the fit in the 8-9 μm spectral band. We discuss the probable binary origin of asymmetries as revealed by millimetric observations. Based on observations made with the Very Large Telescope Interferometer at Paranal Observatory under programs 077.D-0294(D/E/F). Reduced visibilities and differential phases are available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/482/561

Nested Shells Reveal the Rejuvenation of the Orion-Eridanus Superbubble

NASA Astrophysics Data System (ADS)

Ochsendorf, Bram B.; Brown, Anthony G. A.; Bally, John; Tielens, Alexander G. G. M.

2015-08-01

The Orion-Eridanus superbubble is the prototypical superbubble owing to its proximity and evolutionary state. Here we provide a synthesis of recent observational data from WISE and Planck with archival data, allowing us to draw a new and more complete picture on the history and evolution of the Orion-Eridanus region. We discuss the general morphological structures and observational characteristics of the superbubble and derive quantitative properties of the gas and dust inside Barnard’s Loop. We reveal that Barnard’s Loop is a complete bubble structure that, together with the λ Ori region and other smaller-scale bubbles, expands within the Orion-Eridanus superbubble. We argue that the Orion-Eridanus superbubble is larger and more complex than previously thought, and that it can be viewed as a series of nested shells, superimposed along the line of sight. During the lifetime of the superbubble, Hii region champagne flows and thermal evaporation of embedded clouds continuously mass-load the superbubble interior, while winds or supernovae from the Orion OB association rejuvenate the superbubble by sweeping up the material from the interior cavities in an episodic fashion, possibly triggering the formation of new stars that form shells of their own. The steady supply of material into the superbubble cavity implies that dust processing from interior supernova remnants is more efficient than previously thought. The cycle of mass loading, interior cleansing, and star formation repeats until the molecular reservoir is depleted or the clouds have been disrupted. While the nested shells come and go, the superbubble remains for tens of millions of years.

NESTED SHELLS REVEAL THE REJUVENATION OF THE ORION–ERIDANUS SUPERBUBBLE

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

Ochsendorf, Bram B.; Brown, Anthony G. A.; Tielens, Alexander G. G. M.

2015-08-01

The Orion–Eridanus superbubble is the prototypical superbubble owing to its proximity and evolutionary state. Here we provide a synthesis of recent observational data from WISE and Planck with archival data, allowing us to draw a new and more complete picture on the history and evolution of the Orion–Eridanus region. We discuss the general morphological structures and observational characteristics of the superbubble and derive quantitative properties of the gas and dust inside Barnard’s Loop. We reveal that Barnard’s Loop is a complete bubble structure that, together with the λ Ori region and other smaller-scale bubbles, expands within the Orion–Eridanus superbubble. We argue that themore » Orion–Eridanus superbubble is larger and more complex than previously thought, and that it can be viewed as a series of nested shells, superimposed along the line of sight. During the lifetime of the superbubble, Hii region champagne flows and thermal evaporation of embedded clouds continuously mass-load the superbubble interior, while winds or supernovae from the Orion OB association rejuvenate the superbubble by sweeping up the material from the interior cavities in an episodic fashion, possibly triggering the formation of new stars that form shells of their own. The steady supply of material into the superbubble cavity implies that dust processing from interior supernova remnants is more efficient than previously thought. The cycle of mass loading, interior cleansing, and star formation repeats until the molecular reservoir is depleted or the clouds have been disrupted. While the nested shells come and go, the superbubble remains for tens of millions of years.« less

Scanning the parameter space of collapsing rotating thin shells

NASA Astrophysics Data System (ADS)

Rocha, Jorge V.; Santarelli, Raphael

2018-06-01

We present results of a comprehensive study of collapsing and bouncing thin shells with rotation, framing it in the context of the weak cosmic censorship conjecture. The analysis is based on a formalism developed specifically for higher odd dimensions that is able to describe the dynamics of collapsing rotating shells exactly. We analyse and classify a plethora of shell trajectories in asymptotically flat spacetimes. The parameters varied include the shell’s mass and angular momentum, its radial velocity at infinity, the (linear) equation-of-state parameter and the spacetime dimensionality. We find that plunges of rotating shells into black holes never produce naked singularities, as long as the matter shell obeys the weak energy condition, and so respects cosmic censorship. This applies to collapses of dust shells starting from rest or with a finite velocity at infinity. Not even shells with a negative isotropic pressure component (i.e. tension) lead to the formation of naked singularities, as long as the weak energy condition is satisfied. Endowing the shells with a positive isotropic pressure component allows for the existence of bouncing trajectories satisfying the dominant energy condition and fully contained outside rotating black holes. Otherwise any turning point occurs always inside the horizon. These results are based on strong numerical evidence from scans of numerous sections in the large parameter space available to these collapsing shells. The generalisation of the radial equation of motion to a polytropic equation-of-state for the matter shell is also included in an appendix.

Science & Technology Review September 2005

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

Aufderheide III, M B

2005-07-19

This month's issue has the following articles: (1) The Pursuit of Fusion Energy--Commentary by William H. Goldstein; (2) A Dynamo of a Plasma--The self-organizing magnetized plasmas in a Livermore fusion energy experiment are akin to solar flares and galactic jets; (3) How One Equation Changed the World--A three-page paper by Albert Einstein revolutionized physics by linking mass and energy; (4) Recycled Equations Help Verify Livermore Codes--New analytic solutions for imploding spherical shells give scientists additional tools for verifying codes; and (5) Dust That.s Worth Keeping--Scientists have solved the mystery of an astronomical spectral feature in interplanetary dust particles.

The Evolution of Carbon Stars

NASA Astrophysics Data System (ADS)

Chan, S. Josephine

1993-04-01

This dissertation is concerned with the nature of the carbon stars, unusual late-type stars in which the abundance of carbon in the photosphere is greater than that of oxygen. Data from the Infrared Astronomical Satellite (IRAS) survey has shown that carbon stars which were identified from optical surveys and those identified from the SiC dust features in their IRAS Low Resolution Spectrometer LRS spectra have different IRAS colours. The former (which will be referred to as visual carbon stars) are visually bright and have large excesses at 6 microns, while the latter group (which will be referred to as infrared carbon stars) have blackbody energy distributions. The origin of visual carbon stars has been discussed by Chan and Kwok (1988) based on the hypothesis of Willems and de Jong (1988). A complete sample of visual carbon stars detected by IRAS with 12 microns flux densities greater than 5 Jy was selected, and 207 LRS spectra were extracted for those sources without previous \\lrs data. Of these, 152 sources had new LRS spectra with reasonably good signal-to-noise ratio and 575 sources had previously released LRS spectra. All these spectra have been classified with the scheme of Volk and Cohen (1989). When the LRS spectra of these 727 IRAS CCGCS sources were examined, 15 were found to show the 9.7 microns silicate emission feature which is expected to occur only in an oxygen-rich circumstellar shell. Eight of these are reported for the first time in this dissertation. This group of visual carbon stars (hereafter called silicate carbon stars) may represent transition objects between oxygen-rich and carbon stars on the asymptotic giant branch (AGB) because the photosphere is carbon-rich while the circumstellar material resembles that from a typical M-type star. A radiative transfer dust shell model for these silicate carbon stars is presented. The model spectra produce excellent fits to the observed energy distributions of these silicate carbon stars. The J-type stars (^13C-rich carbon stars) have been suggested to be transition objects between M-type stars and C-type stars. An optical spectroscopic study of these silicate carbon stars was performed at the Dominion Astrophysical Observatory (DAO) in Victoria in 1991. CCGCS 1653, CCGCS 4222, CCGCS 4923 and CCGCS 5848 have been confirmed to be J stars. CCGCS 1158 and CCGCS 4729 are provisionally identified as J stars. A preliminary spectral analysis has also been carried out. Model calculations are presented on the evolution from the visual carbon stars to infrared carbon stars, and on the evolution of infrared carbon stars. A new empirical opacity function for the SiC grain is derived based on the LRS spectra of a selected sample of infrared carbon stars. A two-shell model has been developed with an oxygen-rich detached shell and a newly-forming SiC dust shell. The energy distributions of ~110 transition objects which are late-stage visual carbon stars or early-stage infrared carbon stars are fitted with this Interrupted Mass Loss Model. Furthermore, the model tracks successfully explain the "C" shaped distribution of the transition objects in the IRAS 12 microns/25 microns/60 microns colour-colour diagram. The energy distributions of ~150 infrared carbon stars are also matched with a radiative transfer dust shell model using only SiC dust. The colour evolution of infrared carbon stars can be explained with a continuous increase in mass loss rate on the AGB. An evolutionary scenario of AGB stars is suggested. There is a branching of M-type and C-type stars on the AGB with each branch evolving independently to the planetary nebula stage. The initial mass of the star in the main sequence may be the factor that determines which branch the star will follow. (SECTION: Dissertation Abstracts)

SOFIA Observations of SN 2010jl: Another Non-Detection of the 9.7 Micrometer Silicate Dust Feature

NASA Technical Reports Server (NTRS)

Williams, Brian J.; Fox, Ori D.

2015-01-01

We present photometric observations from the Stratospheric Observatory for Infrared Astronomy (SOFIA) at 11.1 micrometers of the Type IIn supernova (SN IIn) 2010jl. The SN is undetected by SOFIA, but the upper limits obtained, combined with new and archival detections from Spitzer at 3.6 and 4.5 micrometers, allow us to characterize the composition of the dust present. Dust in other SN IIn has been shown in previous works to reside in a circumstellar shell of material ejected by the progenitor system in the few millennia prior to explosion. Our model fits show that the dust in the system shows no evidence for the strong, ubiquitous 9.7 micrometer feature from silicate dust, suggesting the presence of carbonaceous grains. The observations are best fit with 0.01-0.05 solar mass of carbonaceous dust radiating at a temperature of approximately 550-620 degrees Kelvin. The dust composition may reveal clues concerning the nature of the progenitor system, which remains ambiguous for this subclass. Most of the single star progenitor systems proposed for SNe IIn, such as luminous blue variables, red supergiants, yellow hypergiants, and B[e] stars, all clearly show silicate dust in their pre-SN outflows. However, this post-SN result is consistent with the small sample of SNe IIn with mid-infrared observations, none of which show signs of emission from silicate dust in their infrared spectra.

Metal Evolution and TrAnsport in the Large Magellanic Cloud (METAL): Probing Dust Evolution in Star Forming Galaxies

NASA Astrophysics Data System (ADS)

Roman-Duval

2016-10-01

METAL is a large spectroscopic and imaging program with HST dedicated to the study of dust evolution in the Large Magellanic Cloud (LMC). The program will obtain FUV and NUV medium-resolution spectra of 33 massive stars in the LMC with STIS and COS complementing existing archival data to measure gas-phase and dust-phase (depletion) elemental abundances. With these spectra, we will subsequently directly measure the dust composition and abundance as a function of environment (surface density, radiation field, dynamical conditions, such as the proximity of supernova remnants or expanding HI shells). The depletion information will be complemented with dust UV extinction curves (i.e., the UV opacity of dust grains as a function of wavelength) derived from either archival IUE, or new COS and low-resolution STIS spectra acquired as part of this program. Together, the depletions and extinction curves will constrain how the dust abundance and properties (composition, size distribution) vary with environment at Z=0.5Zo. In parallel to the spectroscopic observations, we will obtain WFC3 NUV-NIR imaging to map dust extinction parameters (AV, RV) in the vicinity of our targets and calibrate the far-infrared (FIR) emissivity of dust. Our observations we will improve the accuracy of dust mass and extinction estimates in the local and high-redshift universe by up to an order of magnitude.METAL will complement a Cycle 23 HST/STIS program (GO-13778) focused on dust evolution in the Small Magellanic Cloud (SMC) at Z=0.2Zo, and previously published depletion studies in the Milky Way (Jenkins et al. 2009) to provide a comprehensive view of dust evolution as a function of metallicity.

Cassiopeia A: Death Becomes Her

NASA Technical Reports Server (NTRS)

2005-01-01

This stunning false-color picture shows off the many sides of the supernova remnant Cassiopeia A. It is made up of images taken by three of NASA's Great Observatories, using three different wavebands of light. Infrared data from the Spitzer Space Telescope are colored red; visible data from the Hubble Space Telescope are yellow; and X-ray data from the Chandra X-ray Observatory are green and blue.

Located 10,000 light-years away in the northern constellation Cassiopeia, Cassiopeia A is the remnant of a once massive star that died in a violent supernova explosion 325 years ago. It consists of a dead star, called a neutron star, and a surrounding shell of material that was blasted off as the star died. The neutron star can be seen in the Chandra data as a sharp turquoise dot in the center of the shimmering shell.

Each Great Observatory highlights different characteristics of this celestial orb. While Spitzer reveals warm dust in the outer shell about a few hundred degrees Kelvin (80 degrees Fahrenheit) in temperature, Hubble sees the delicate filamentary structures of hot gases about 10,000 degrees Kelvin (18,000 degrees Fahrenheit). Chandra probes unimaginably hot gases, up to about 10 million degrees Kelvin (18 million degrees Fahrenheit). These extremely hot gases were created when ejected material from Cassiopeia A smashed into surrounding gas and dust. Chandra can also see Cassiopeia A's neutron star (turquoise dot at center of shell).

Blue Chandra data were acquired using broadband X-rays (low to high energies); green Chandra data correspond to intermediate energy X-rays; yellow Hubble data were taken using a 900 nanometer-wavelength filter, and red Spitzer data are from the telescope's 24-micron detector.

The animation begins with the false-color picture of the supernova remnant Cassiopeia A. It then pans out to show a Spitzer view of Cassiopeia A (yellow ball) and surrounding clouds of dust (reddish orange). Here, the animation flips back and forth between two Spitzer images taken one year apart. A blast of light from Cassiopeia A is seen waltzing through the dusty skies. Called an 'infrared echo,' this dance began when the remnant's dead star erupted, or 'turned in its grave,' about 50 years ago.

Infrared echoes are created when a star explodes or erupts, flashing light into surrounding clumps of dust. As the light zips through the dust clumps, it heats them up, causing them to glow successively in infrared, like a chain of Christmas bulbs lighting up one by one. The result is an optical illusion, in which the dust appears to be flying outward at the speed of light. Echoes are distinct from supernova shockwaves, which are made up material that is swept up and hurled outward by exploding stars.

This infrared echo is the largest ever seen, stretching more than 50 light-years away from Cassiopeia A. If viewed from Earth, the entire movie frame would take up the same amount of space as two full moons.

Hints of an older infrared echo from Cassiopeia A's supernova explosion hundreds of years ago can also be seen.

The earlier Spitzer image was taken on November 30, 2003, and the later, on December 2, 2004.

On the morphology of the compact dust shell in the symbiotic system HM Sagittae

NASA Astrophysics Data System (ADS)

Sacuto, S.; Chesneau, O.

2009-01-01

Context: The symbiotic system HM Sagittae consists of a Mira star and a secondary White Dwarf component. The dust content of the system was severely affected by the nova outburst in 1975, which is still ongoing. The capabilities of optical interferometry operating in the mid-IR allow us to investigate the current geometry of the dust envelope. Aims: We test our previous spectro-interferometric study of this system with new interferometric configurations, increasing the uv coverage and allowing us to ascertain the appearance of the source between 8 and 13 μm. Methods: We used the MIDI instrument of the VLTI with the unit telescopes (UTs) and auxiliary telescopes (ATs) providing baselines oriented from PA = 42° to 127°. The data are interpreted by means of an elliptical Gaussian model and the spherical radiative transfer code DUSTY. Results: We demonstrate that the data can be reproduced well by an optically thick dust shell of amorphous silicate, typical of those encountered around Mira stars, whose measured dimension increases from 8 to 13 μm. We confirm that the envelope is more extended in a direction perpendicular to the binary axis. The level of elongation increases with wavelength in contrast to our claim in a previous study. Conclusions: The wider uv coverage allows us to deepen our previous investigations of the close circumstellar structure of this object. Based on observations made with the Very Large Telescope Interferometer at Paranal Observatory under programs 075.D-0484, 077.D-0216, and 079.D-0213. Reduced visibilities and differential phases are available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/493/1043

A compact dust shell in the symbiotic system HM Sagittae

NASA Astrophysics Data System (ADS)

Sacuto, S.; Chesneau, O.; Vannier, M.; Cruzalèbes, P.

2007-04-01

Aims:We present high spatial resolution observations of the mid-infrared core of the dusty symbiotic system HM Sge. Methods: The MIDI interferometer was used with the VLT Unit Telescopes and Auxiliary Telescopes providing baselines oriented from PA = 42° to 105°. The MIDI visibilities are compared with the ones predicted in the frame of various spherical dust shells published in the literature involving single or double dusty shells intended to account for the influence of the hot White Dwarf. Results: The mid-IR environment is unresolved by a 8 m telescope (resolution ~ 300 mas) and the MIDI spectrum exhibits a level similar to the ISO spectra recorded 10 yr ago. The estimated Gaussian Half Width at Half Maximum of the shell of 7.8±1.3 mas (12 AU, assuming a distance of 1.5 kpc) in the 8-9 μm range, and 11.9±1.3 mas (18 AU) in the 11-12 μm range, are much smaller than the angular separation between the Mira and the White Dwarf of 40 mas (60 AU). The discrepancies between the HWHM at different angle orientations suggest an increasing level of asymmetry from 13 to 8 μm. The observations are surprisingly well fitted by the densest (optically thick in the N band) and smallest spherical model published in the literature based on the ISO data, although such a model does not account for the variations of near-IR photometry due to the Mira pulsation cycle suggesting a much smaller optical thickness. These observations also discard the two shells models, developed in an attempt to take into account the effect of the White Dwarf illumination onto the dusty wind of the Mira. These models are too extended, and lead to a level of asymmetry of the dusty environment tightly constrained by the MIDI visibilities. These observations show that a high rate of dust formation is occurring in the vicinity of the Mira which seems to be not highly perturbed by the hot companion. Based on observations made with the Very Large Telescope Interferometer at Paranal Observatory under programs 075.D-0484 and 077.D-0216. Visibility ans differential phase data are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/465/469 Appendices are only available in electronic form at http://www.aanda.org

Discovery of polarized light scattered by dust around Alpha Orionis

NASA Technical Reports Server (NTRS)

Mcmillan, R. S.; Tapia, S.

1978-01-01

Following the suggestion by Jura and Jacoby (1976), linearly polarized blue continuum starlight scattered by the dust shell around the M2 Iab star Alpha Orionis (Betelgeuse) has been discovered. The polarization has been traced in the NE, NW, SE, and SW directions and has positive (tangential) orientation. Some asymmetry of the optical depth in the shell exists 15 and 30 arcsec from the star. In the NE direction the polarization was measured as far as 90 arcsec (17,000 AU) from the star. The dependence of the average intensity of the scattered light from the nebula on angular distance from the star is more consistent with an inverse-square density law than with inverse 1.5 or inverse-cube laws. Assuming that the density is proportional to the inverse square of distance from the star, the scattering optical depth in blue light along a radius of 0.03 arcsec is no more than 0.15 + or - 0.05. Future observations of the wavelength dependence of polarization will allow a determination of grain size.

The Local Bubble: a magnetic veil to our Galaxy

NASA Astrophysics Data System (ADS)

Alves, M. I. R.; Boulanger, F.; Ferrière, K.; Montier, L.

2018-04-01

The magnetic field in the local interstellar medium does not follow the large-scale Galactic magnetic field. The local magnetic field has probably been distorted by the Local Bubble, a cavity of hot ionized gas extending all around the Sun and surrounded by a shell of cold neutral gas and dust. However, so far no conclusive association between the local magnetic field and the Local Bubble has been established. Here we develop an analytical model for the magnetic field in the shell of the Local Bubble, which we represent as an inclined spheroid, off-centred from the Sun. We fit the model to Planck dust polarized emission observations within 30° of the Galactic poles. We find a solution that is consistent with a highly deformed magnetic field, with significantly different directions towards the north and south Galactic poles. This work sets a methodological framework for modelling the three-dimensional (3D) structure of the magnetic field in the local interstellar medium, which is a most awaited input for large-scale Galactic magnetic field models.

Dust and ionized gas in active radio elliptical galaxies

NASA Technical Reports Server (NTRS)

Forbes, D. A.; Sparks, W. B.; Macchetto, F. D.

1990-01-01

The authors present broad and narrow bandwidth imaging of three southern elliptical galaxies which have flat-spectrum active radio cores (NGC 1052, IC 1459 and NGC 6958). All three contain dust and extended low excitation optical line emission, particularly extensive in the case of NGC 1052 which has a large H alpha + (NII) luminosity. Both NGC 1052 and IC 1459 have a spiral morphology in emission-line images. All three display independent strong evidence that a merger or infall event has recently occurred, i.e., extensive and infalling HI gas in NGC 1052, a counter-rotating core in IC 1459 and Malin-Carter shells in NGC 6958. This infall event is the most likely origin for the emission-line gas and dust, and the authors are currently investigating possible excitation mechanisms (Sparks et al. 1990).

Nature versus Nurture: Luminous Blue Variable Nebulae in and near Massive Stellar Clusters at the Galactic Center

NASA Astrophysics Data System (ADS)

Lau, R. M.; Herter, T. L.; Morris, M. R.; Adams, J. D.

2014-04-01

Three luminous blue variables (LBVs) are located in and near the Quintuplet Cluster at the Galactic center: the Pistol Star, G0.120-0.048, and qF362. We present imaging at 19, 25, 31, and 37 μm of the region containing these three LBVs, obtained with SOFIA using FORCAST. We argue that Pistol and G0.120-0.048 are identical "twins" that exhibit contrasting nebulae due to the external influence of their different environments. Our images reveal the asymmetric, compressed shell of hot dust surrounding the Pistol Star and provide the first detection of the thermal emission from the symmetric, hot dust envelope surrounding G0.120-0.048. However, no detection of hot dust associated with qF362 is made. Dust and gas composing the Pistol nebula are primarily heated and ionized by the nearby Quintuplet Cluster stars. The northern region of the Pistol nebula is decelerated due to the interaction with the high-velocity (2000 km s-1) winds from adjacent Wolf-Rayet Carbon (WC) stars. From fits to the spectral energy distribution (SED) of the Pistol nebula with the DustEM code we determine that the Pistol nebula is composed of a distribution of very small, transiently heated grains (10 to ~ 35 Å) having a total dust mass of 0.03 M ⊙, and that it exhibits a gradient of decreasing grain size from south to north due to differential sputtering by the winds from the WC stars. The total IR luminosity of the Pistol nebula is 5.2 × 105 L ⊙. Dust in the G0.120-0.048 nebula is primarily heated by the central star; however, the nebular gas is ionized externally by the Arches Cluster. Unlike the Pistol nebula, the G0.120-0.048 nebula is freely expanding into the surrounding medium. A grain size distribution identical to that of the non-sputtered region of the Pistol nebula satisfies the constraints placed on the G0.120-0.048 nebula from DustEM model fits to its SED and implies a total dust mass of 0.021 M ⊙. The total IR luminosity of the G0.120-0.048 nebula is ~105 L ⊙. From Paschen-α and 6 cm observations we determine a total gas mass of 9.3 M ⊙ and 6.2 M ⊙ for the Pistol and G0.120-0.048 nebulae, respectively. Given the independent dust and gas mass estimates we find that the Pistol and G0.120-0.048 nebulae exhibit similar gas-to-dust mass ratios of 310^{+77}_{-52} and 293^{+73}_{-101}, respectively. Both nebulae share identical size scales (~0.7 pc) which suggests that they have similar dynamical timescales of ~104 yr, assuming a shell expansion velocity of v exp = 60 km s-1.

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).

Delayed Shock-induced Dust Formation in the Dense Circumstellar Shell Surrounding the Type IIn Supernova SN 2010jl

NASA Astrophysics Data System (ADS)

Sarangi, Arkaprabha; Dwek, Eli; Arendt, Richard G.

2018-05-01

The light curves of Type IIn supernovae are dominated by the radiative energy released through the interaction of the supernova shock waves with their dense circumstellar medium (CSM). The ultraluminous Type IIn supernova SN 2010jl exhibits an infrared emission component that is in excess of the extrapolated UV–optical spectrum as early as few weeks postexplosion. This emission has been considered by some as evidence for the rapid formation of dust in the cooling postshock CSM. We investigate the physical processes that may inhibit or facilitate the formation of dust in the CSM. When only radiative cooling is considered, the temperature of the dense shocked gas rapidly drops below the dust condensation temperature. However, by accounting for the heating of the postshock gas by the downstream radiation from the shock, we show that dust formation is inhibited until the radiation from the shock weakens as it propagates into the less dense outer regions of the CSM. In SN 2010jl, dust formation can therefore only commence after day ∼380. Only the IR emission since that epoch can be attributed to the newly formed CSM dust. Observations on day 460 and later show that the IR luminosity exceeds the UV–optical luminosity. The postshock dust cannot extinct the radiation emitted by the expanding SN shock. Therefore, its IR emission must be powered by an interior source, which we identify as the reverse shock propagating through the SN ejecta. IR emission before day 380 must therefore be an IR echo from preexisting CSM dust.

Optical properties and carrier dynamics of GaAs/GaInAs multiple-quantum-well shell grown on GaAs nanowire by molecular beam epitaxy

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

Park, Kwangwook; Ravindran, Sooraj; Ju, Gun Wu

GaAs/GaInAs multiple-quantum-well (MQW) shells having different GaInAs shell width formed on the surface of self-catalyzed GaAs core nanowires (NWs) are grown on (100) Si substrate using molecular beam epitaxy. The photoluminescence emission from GaAs/GaInAs MQW shells and the carrier lifetime could be varied by changing the width of GaInAs shell. Time-resolved photoluminescence measurements showed that the carrier lifetime had a fast and slow decay owing to the mixing of wurtzite and zinc-blende structures of the NWs. Furthermore, strain relaxation caused the carrier lifetime to decrease beyond a certain thickness of GaInAs quantum well shells.

12. BUILDING 621, INTERIOR, GROUND FLOOR, LOOKING NORTHWEST AT SCREENING ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

12. BUILDING 621, INTERIOR, GROUND FLOOR, LOOKING NORTHWEST AT SCREENING MACHINE THAT REMOVES SHELL FRAGMENTS. METALLIC DUST REMOVED BY MAGNETIC SEPERATOR UNDERNEATH SCREEN. SAWDUST IS RETURNED TO SAWDUST HOPPER BY ELEVATOR. HOODS OVER SCREENING MACHINE AT WORKBENCH REMOVE FINE SAWDUST. - Picatinny Arsenal, 600 Area, Test Areas District, State Route 15 near I-80, Dover, Morris County, NJ

Multi-proxies Approach of Climatic Records In Terrestrial Mollusks Shells

NASA Astrophysics Data System (ADS)

Labonne, M.; Rousseau, D. D.; Ben Othman, D.; Luck, J. M.; Metref, S.

Fossil land snails shells constitute a valuable source of information for the study of Quaternary deposits as they are commonly preserved in many regions and notably in loess sequences. The use of stable isotope composition of the carbonate in the shells was previously applied to reconstruct past climate or environnements but the technic was not widely exploited and compared with other proxies from the same sequence. In this study, we have analysed stables isotopes, trace elements and Sr isotopes from both shells of land snails Vertigo modesta and the sediment from the Eustis upper Pleistocene loess sequence (Nebraska, USA). This serie developed during the last glaciation and records the last deglaciation between 18,000 and 12,000 B.P. years. We compare the paleoclimatic information obtained by different proxies, such as mag- netic susceptibility, temperature and moisture estimated by land snails assemblage with geochemical data measured on land snails shells in order to validate the climatic information obtained with this proxy. Our study demonstrates that shell carbonate reflects environmental conditions estimated by other proxies. Carbon and oxygen iso- topes show cyclic variations (millenial cycles) along the profile which correlate with stratigraphic units and could be link with the retreat of the Laurentide ice sheet. Trace element and Sr isotopes in the shells indicate various origins for the eolian dusts in the two main loess units along the sequence.

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

Gronke, M.; Dijkstra, M., E-mail: maxbg@astro.uio.no

We perform Lyman- α (Ly α ) Monte-Carlo radiative transfer calculations on a suite of 2500 models of multiphase, outflowing media, which are characterized by 14 parameters. We focus on the Ly α spectra emerging from these media and investigate which properties are dominant in shaping the emerging Ly α profile. Multiphase models give rise to a wide variety of emerging spectra, including single-, double-, and triple-peaked spectra. We find that the dominant parameters in shaping the spectra include (i) the cloud covering factor, f {sub c} , which is in agreement with earlier studies, and (ii) the temperature andmore » number density of residual H i in the hot ionized medium. We attempt to reproduce spectra emerging from multiphase models with “shell models” which are commonly used to fit observed Ly α spectra, and investigate the connection between shell-model parameters and the physical parameters of the clumpy media. In shell models, the neutral hydrogen content of the shell is one of the key parameters controlling Ly α radiative transfer. Because Ly α spectra emerging from multiphase media depend much less on the neutral hydrogen content of the clumps, the shell-model parameters such as H i column density (but also shell velocity and dust content) are generally not well matched to the associated physical parameters of the clumpy media.« less

The Temporal Development of Dust Formation and Destruction in Nova Sagittarii 2015#2 (V5668 SGR): A Panchromatic Study

NASA Astrophysics Data System (ADS)

Gehrz, R. D.; Evans, A.; Woodward, C. E.; Helton, L. A.; Banerjee, D. P. K.; Srivastava, M. K.; Ashok, N. M.; Joshi, V.; Eyres, S. P. S.; Krautter, Joachim; Kuin, N. P. M.; Page, K. L.; Osborne, J. P.; Schwarz, G. J.; Shenoy, D. P.; Shore, S. N.; Starrfield, S. G.; Wagner, R. M.

2018-05-01

We present 5–28 μm SOFIA FORECAST spectroscopy complemented by panchromatic X-ray through infrared observations of the CO nova V5668 Sgr documenting the formation and destruction of dust during ∼500 days following outburst. Dust condensation commenced by 82 days after outburst at a temperature of ∼1090 K. The condensation temperature indicates that the condensate was amorphous carbon. There was a gradual decrease of the grain size and dust mass during the recovery phase. Absolute parameter values given here are for an assumed distance of 1.2 kpc. We conclude that the maximum mass of dust produced was 1.2 × 10‑7 M ⊙ if the dust was amorphous carbon. The average grain radius grew to a maximum of ∼2.9 μm at a temperature of ∼720 K around day 113 when the shell visual optical depth was τ v ∼ 5.4. Maximum grain growth was followed by a period of grain destruction. X-rays were detected with Swift from day 95 to beyond day 500. The Swift X-ray count rate due to the hot white dwarf peaked around day 220, when its spectrum was that of a kT = 35 eV blackbody. The temperature, together with the supersoft X-ray turn-on and turn-off times, suggests a white dwarf mass of ∼1.1 M ⊙. We show that the X-ray fluence was sufficient to destroy the dust. Our data show that the post-dust event X-ray brightening is not due to dust destruction, which certainly occurred, as the dust is optically thin to X-rays.

Dust Evolution in Nova Cassiopeia 1993

NASA Astrophysics Data System (ADS)

Eyres, S. P. S.; Evans, A.; Geballe, T. R.; Davies, J. K.; Rawlings, J. M. C.

1997-07-01

We present UKIRT spectroscopy of Nova Cassiopeia 1993 (= V705 Cas) in KLNQ bands, taken in 1994 and 1995. Fitting the continuum indicates a dust temperature T ˜ 740 750 K in the latter part of 1994; this is similar to earlier measurements, and consistent with the “isothermal” behaviour observed in novae with optically thick dust shells. The β-index drops from 0.8 to 0.4 over the same period. This suggests grain growth; grain diameter increases from < 0.54 µm around day 256, to > 0.57 µm by day 342. The UIR features differ from those in other Galactic sources, and are similar to those in V842 Cen. This suggests fundamental differences between the UIR carriers, or environments, in novae and other Galactic sources. The silicate feature is consistent with an amorphous structure, in contrast to previous novae. We believe that grains in V705 Cas form two populations: silicates, and hydrocarbons.

Nova V2362 Cygni (Nova Cygni 2006): Spitzer, Swift, and Ground-Based Spectral Evolution

NASA Technical Reports Server (NTRS)

Lynch, David K.; Venturini, Catherine C.; Mazuk, S.; Woodward, Charles; Gehrz, Robert; Rayner, John; Helton, L.A.; Ness, Jan-Uwe; Starrfield, Sumner; Rudy, Richard J.;

Magnetically controlled multifrequency invisibility cloak with a single shell of ferrite material

NASA Astrophysics Data System (ADS)

Wang, Xiaohua; Liu, Youwen

2015-02-01

A magnetically controlled multifrequency invisibility cloak with a single shell of the isotropic and homogeneous ferrite material has been investigated based on the scattering cancellation method from the Mie scattering theory. The analytical and simulated results have demonstrated that such this shell can drastically reduce the total scattering cross-section of this cloaking system at multiple frequencies. These multiple cloaking frequencies of this shell can be externally controlled since the magnetic permeability of ferrites is well tuned by the applied magnetic field. This may provide a potential way to design a tunable multifrequency invisibility cloak with considerable flexibility.

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.

VLBA Teams With Optical Interferometer to Study Star's Layers

NASA Astrophysics Data System (ADS)

2007-05-01

Two of the World's Largest Interferometric Facilities Team-up to Study a Red Giant Star Using ESO's VLTI on Cerro Paranal and the VLBA facility operated by NRAO, an international team of astronomers has made what is arguably the most detailed study of the environment of a pulsating red giant star. They performed, for the first time, a series of coordinated observations of three separate layers within the star's tenuous outer envelope: the molecular shell, the dust shell, and the maser shell, leading to significant progress in our understanding of the mechanism of how, before dying, evolved stars lose mass and return it to the interstellar medium. S Orionis (S Ori) belongs to the class of Mira-type variable stars. It is a solar-mass star that, as will be the fate of our Sun in 5 billion years, is nearing its gloomy end as a white dwarf. Mira stars are very large and lose huge amounts of matter. Every year, S Ori ejects as much as the equivalent of Earth's mass into the cosmos. ESO PR Photo 25a/07 ESO PR Photo 25a/07 Evolution of the Mira-type Star S Orionis "Because we are all stardust, studying the phases in the life of a star when processed matter is sent back to the interstellar medium to be used for the next generation of stars, planets... and humans, is very important," said Markus Wittkowski, lead author of the paper reporting the results. A star such as the Sun will lose between a third and half of its mass during the Mira phase. S Ori pulsates with a period of 420 days. In the course of its cycle, it changes its brightness by a factor of the order of 500, while its diameter varies by about 20%. Although such stars are enormous - they are typically larger than the current Sun by a factor of a few hundred, i.e. they encompass the orbit of the Earth around the Sun - they are also distant and to peer into their deep envelopes requires very high resolution. This can only be achieved with interferometric techniques. ESO PR Photo 25b/07 ESO PR Photo 25b/07 Structure of S Ori (Artist's Impression) "Astronomers are like medical doctors, who use various instruments to examine different parts of the human body," said co-author David Boboltz. "While the mouth can be checked with a simple light, a stethoscope is required to listen to the heart beat. Similarly the heart of the star can be observed in the optical, the molecular and dust layers can be studied in the infrared and the maser emission can be probed with radio instruments. Only the combination of the three gives us a more complete picture of the star and its envelope." The maser emission comes from silicon monoxide (SiO) molecules and can be used to image and track the motion of gas clouds in the stellar envelope roughly 10 times the size of the Sun. The astronomers observed S Ori with two of the largest interferometric facilities available: the ESO Very Large Telescope Interferometer (VLTI) at Paranal, observing in the near- and mid-infrared, and the NRAO-operated Very Long Baseline Array (VLBA), that takes measurements in the radio wave domain. Because the star's luminosity changes periodically, the astronomers observed it simultaneously with both instruments, at several different epochs. The first epoch occurred close to the stellar minimum luminosity and the last just after the maximum on the next cycle. ESO PR Photo 25c/07 ESO PR Photo 25c/07 S Ori to Scale (Artist's Impression) The astronomers found the star's diameter to vary between 7.9 milliarcseconds and 9.7 milliarcseconds. At the distance of S Ori, this corresponds to a change of the radius from about 1.9 to 2.3 times the distance between the Earth and the Sun, or between 400 and 500 solar radii! As if such sizes were not enough, the inner dust shell is found to be about twice as big. The maser spots, which also form at about twice the radius of the star, show the typical structure of partial to full rings with a clumpy distribution. Their velocities indicate that the gas is expanding radially, moving away at a speed of about 10 km/s. The multi-wavelength analysis indicates that near the minimum there is more dust production and mass ejection: in these phases indeed the amount of dust is significantly higher than in the others. After this intense matter production and ejection the star continues its pulsation and when it reaches the maximum luminosity, it displays a much more expanded dust shell. This clearly supports a strong connection between the Mira pulsation and the dust production and expulsion. Furthermore, the astronomers found that grains of aluminum oxide - also called corundum - constitute most of S Ori's dust shell: the grain size is estimated to be of the order of 10 millionths of a centimetre, that is one thousand times smaller than the diameter of a human hair. "We know one chapter of the secret life of a Mira star, but much more can be learned in the near future, when we add near-infrared interferometry with the AMBER instrument on the VLTI to our (already broad) observational approach," said Wittkowski. More Information The research presented here is reported in a paper in press in the journal Astronomy and Astrophysics ("The Mira variable S Ori: Relationships between the photosphere, molecular layer, dust shell, and SiO maser shell at 4 epochs", by M. Wittkowski et al.). It is available in PDF format from the publisher's web site. The team consists of Markus Wittkowski (ESO), David A. Boboltz (U.S. Naval Observatory, USA), Keiichi Ohnaka and Thomas Driebe (MPIfR Bonn, Germany), and Michael Scholz (University of Heidelberg, Germany and University of Sydney, Australia). Notes A maser is the microwave equivalent to a laser, which emits visible light. A maser emits powerful microwave radiation instead and its study requires radio telescopes. An astrophysical maser is a naturally occurring source of stimulated emission that may arise in molecular clouds, comets, planetary atmospheres, stellar atmospheres, or from various conditions in interstellar space. ESO operates the Very Large Telescope Interferometer at Paranal Observatory, Chile, with four fixed 8.2-m telescopes and four relocatable 1.8-m telescopes, working at optical/infrared wavelengths. NRAO operates the Very Long Baseline Array with 10 stations across the U.S. working at radio wavelengths between 3 mm and 90 cm (0.3-90 GHz). ESO, NRAO and other partners will operate the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, working at millimetre wavelengths between 0.3 and 10 mm (30-950 GHz)

Nature versus nurture: Luminous blue variable nebulae in and near massive stellar clusters at the galactic center

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

Lau, R. M.; Herter, T. L.; Adams, J. D.

Three luminous blue variables (LBVs) are located in and near the Quintuplet Cluster at the Galactic center: the Pistol Star, G0.120-0.048, and qF362. We present imaging at 19, 25, 31, and 37 μm of the region containing these three LBVs, obtained with SOFIA using FORCAST. We argue that Pistol and G0.120-0.048 are identical 'twins' that exhibit contrasting nebulae due to the external influence of their different environments. Our images reveal the asymmetric, compressed shell of hot dust surrounding the Pistol Star and provide the first detection of the thermal emission from the symmetric, hot dust envelope surrounding G0.120-0.048. However, nomore » detection of hot dust associated with qF362 is made. Dust and gas composing the Pistol nebula are primarily heated and ionized by the nearby Quintuplet Cluster stars. The northern region of the Pistol nebula is decelerated due to the interaction with the high-velocity (2000 km s{sup –1}) winds from adjacent Wolf-Rayet Carbon (WC) stars. From fits to the spectral energy distribution (SED) of the Pistol nebula with the DustEM code we determine that the Pistol nebula is composed of a distribution of very small, transiently heated grains (10 to ∼ 35 Å) having a total dust mass of 0.03 M {sub ☉}, and that it exhibits a gradient of decreasing grain size from south to north due to differential sputtering by the winds from the WC stars. The total IR luminosity of the Pistol nebula is 5.2 × 10{sup 5} L {sub ☉}. Dust in the G0.120-0.048 nebula is primarily heated by the central star; however, the nebular gas is ionized externally by the Arches Cluster. Unlike the Pistol nebula, the G0.120-0.048 nebula is freely expanding into the surrounding medium. A grain size distribution identical to that of the non-sputtered region of the Pistol nebula satisfies the constraints placed on the G0.120-0.048 nebula from DustEM model fits to its SED and implies a total dust mass of 0.021 M {sub ☉}. The total IR luminosity of the G0.120-0.048 nebula is ∼10{sup 5} L {sub ☉}. From Paschen-α and 6 cm observations we determine a total gas mass of 9.3 M {sub ☉} and 6.2 M {sub ☉} for the Pistol and G0.120-0.048 nebulae, respectively. Given the independent dust and gas mass estimates we find that the Pistol and G0.120-0.048 nebulae exhibit similar gas-to-dust mass ratios of 310{sub −52}{sup +77} and 293{sub −101}{sup +73}, respectively. Both nebulae share identical size scales (∼0.7 pc) which suggests that they have similar dynamical timescales of ∼10{sup 4} yr, assuming a shell expansion velocity of v {sub exp} = 60 km s{sup –1}.« less

Mid-Infrared Long-Baseline Interferometry of the Symbiotic Mira Star RX Pup with the VLTI/MIDI Instrument

NASA Astrophysics Data System (ADS)

Driebe, T.; Hofmann, K.-H.; Ohnaka, K.; Schertl, D.; Weigelt, G.; Wittkowski, M.

We present mid-infrared long-baseline interferometric observations of the symbiotic Mira star RX Pup obtained with the VLTI/MIDI instrument in prism mode within the framework of the Science Demonstration Time (SDT) program in Feb. 2004. Four visibility measurements have been carried out using the unit telescopes UT2 and UT3, with projected baseline lengths ranging from 34.7 to 46.5 m.As we show by means of radiative transfer modelin with the code DUSTY [3], the wavelength dependence of the visibility and the N-band spectrum measured with MIDI can be interpreted as thesignature of a circumstellar dust shell which is dominated by silicate dust.

Energy emission from a high curvature region and its backreaction

NASA Astrophysics Data System (ADS)

Kokubu, Takafumi; Jhingan, Sanjay; Harada, Tomohiro

2018-05-01

A strong gravity naked singular region can give important clues toward understanding the classical as well as spontaneous nature of General Relativity. We propose here a model for energy emission from a naked singular region in a self-similar dust spacetime by gluing two self-similar dust solutions at the Cauchy horizon. The energy is defined and evaluated as a surface energy of a null hypersurface, the null shell. Also included are scenarios of the spontaneous creation or disappearance of a singularity, the end of inflation, black hole formation, and bubble nucleation. Our examples investigated here explicitly show that one can model unlimitedly luminous and energetic objects in the framework of General Relativity.

The circumstellar envelope of the C-rich post-AGB star HD 56126

NASA Astrophysics Data System (ADS)

Hony, S.; Tielens, A. G. G. M.; Waters, L. B. F. M.; de Koter, A.

2003-04-01

We present a detailed study of the circumstellar envelope of the post-asymptotic giant branch ``21 mu m object'' HD 56126. We build a detailed dust radiative transfer model of the circumstellar envelope in order to derive the dust composition and mass, and the mass-loss history of the star. To model the emission of the dust we use amorphous carbon, hydrogenated amorphous carbon, magnesium sulfide and titanium carbide. We present a detailed parametrisation of the optical properties of hydrogenated amorphous carbon as a function of H/C content. The mid-infrared imaging and spectroscopy is best reproduced by a single dust shell from 1.2 to 2.6'' radius around the central star. This shell originates from a short period during which the mass-loss rate exceeded 10-4 Msun/yr. We find that the strength of the ``21'' mu m feature poses a problem for the TiC identification. The low abundance of Ti requires very high absorption cross-sections in the ultraviolet and visible wavelength range to explain the strength of the feature. Other nano-crystalline metal carbides should be considered as well. We find that hydrogenated amorphous carbon in radiative equilibrium with the local radiation field does not reach a high enough temperature to explain the strength of the 3.3-3.4 and 6-9 mu m hydrocarbon features relative to the 11-17 mu m hydrocarbon features. We propose that the carriers of these hydrocarbon features are not in radiative equilibrium but are transiently heated to high temperature. We find that 2 per cent of the dust mass is required to explain the strength of the ``30'' mu m feature, which fits well within the measured atmospheric abundance of Mg and S. This further strengthens the MgS identification of the ``30'' mu m feature. Based on observations taken at the European Southern Observatory, La Silla, Chile and observation obtained with ISO, an ESA project with instruments funded by ESA Member states (especially the PI countries: France, Germany, The Netherlands and the UK) with the participation of ISAS and NASA.

EXTINCTION LAWS TOWARD STELLAR SOURCES WITHIN A DUSTY CIRCUMSTELLAR MEDIUM AND IMPLICATIONS FOR TYPE IA SUPERNOVAE

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

Nagao, Takashi; Maeda, Keiichi; Nozawa, Takaya, E-mail: nagao@kusastro.kyoto-u.ac.jp

Many astronomical objects are surrounded by dusty environments. In such dusty objects, multiple scattering processes of photons by circumstellar (CS) dust grains can effectively alter extinction properties. In this paper, we systematically investigate the effects of multiple scattering on extinction laws for steady-emission sources surrounded by the dusty CS medium using a radiation transfer simulation based on the Monte Carlo technique. In particular, we focus on whether and how the extinction properties are affected by properties of CS dust grains by adopting various dust grain models. We confirm that behaviors of the (effective) extinction laws are highly dependent on themore » properties of CS grains, especially the total-to-selective extinction ratio R{sub V}, which characterizes the extinction law and can be either increased or decreased and compared with the case without multiple scattering. We find that the criterion for this behavior is given by a ratio of albedos in the B and V bands. We also find that either small silicate grains or polycyclic aromatic hydrocarbons are necessary for realizing a low value of R{sub V} as often measured toward SNe Ia if the multiple scattering by CS dust is responsible for their non-standard extinction laws. Using the derived relations between the properties of dust grains and the resulting effective extinction laws, we propose that the extinction laws toward dusty objects could be used to constrain the properties of dust grains in CS environments.« less

PO43 Removal by and Permeability of Industrial Byproducts and Minerals: Granulated Blast Furnace Slag, Cement Kiln Dust, Coconut Shell Activated Carbon, Silica Sand and Zeolite

USDA-ARS?s Scientific Manuscript database

Excess aqueous concentration of phosphate degrades the overall water quality of the receiving surface waters in a cumulatively damaging process referred to as eutrophication. Adsorption of excess phosphate has proven to be the most effective, and economical methods of phosphate removal from such wat...

ALMA sub-mm maser and dust distribution of VY Canis Majoris

NASA Astrophysics Data System (ADS)

Richards, A. M. S.; Impellizzeri, C. M. V.; Humphreys, E. M.; Vlahakis, C.; Vlemmings, W.; Baudry, A.; De Beck, E.; Decin, L.; Etoka, S.; Gray, M. D.; Harper, G. M.; Hunter, T. R.; Kervella, P.; Kerschbaum, F.; McDonald, I.; Melnick, G.; Muller, S.; Neufeld, D.; O'Gorman, E.; Parfenov, S. Yu.; Peck, A. B.; Shinnaga, H.; Sobolev, A. M.; Testi, L.; Uscanga, L.; Wootten, A.; Yates, J. A.; Zijlstra, A.

2014-12-01

Aims: Cool, evolved stars have copious, enriched winds. Observations have so far not fully constrained models for the shaping and acceleration of these winds. We need to understand the dynamics better, from the pulsating stellar surface to ~10 stellar radii, where radiation pressure on dust is fully effective. Asymmetric nebulae around some red supergiants imply the action of additional forces. Methods: We retrieved ALMA Science Verification data providing images of sub-mm line and continuum emission from VY CMa. This enables us to locate water masers with milli-arcsec accuracy and to resolve the dusty continuum. Results: The 658, 321, and 325 GHz masers lie in irregular, thick shells at increasing distances from the centre of expansion. For the first time this is confirmed as the stellar position, coinciding with a compact peak offset to the NW of the brightest continuum emission. The maser shells overlap but avoid each other on scales of up to 10 au. Their distribution is broadly consistent with excitation models but the conditions and kinematics are complicated by wind collisions, clumping, and asymmetries. Appendices are available in electronic form at http://www.aanda.org

Persistent Organic Pollutants in Dust From Older Homes: Learning From Lead

PubMed Central

Metayer, Catherine; Ward, Mary H.; Colt, Joanne S.; Gunier, Robert B.; Deziel, Nicole C.; Rappaport, Stephen M.; Buffler, Patricia A.

2014-01-01

Objectives. We aimed to (1) evaluate the relation between home age and concentrations of multiple chemical contaminants in settled dust and (2) discuss the feasibility of using lead hazard controls to reduce children’s exposure to persistent organic pollutants. Methods. As part of the California Childhood Leukemia Study, from 2001 to 2007, we used a high-volume small surface sampler and household vacuum cleaners to collect dust samples from 583 homes and analyzed the samples for 94 chemicals with gas chromatography–mass spectrometry and inductively coupled plasma mass spectrometry. We evaluated relations between chemical concentrations in dust and home age with Spearman rank correlation coefficients. Results. Dust concentrations of lead, polychlorinated biphenyls, organochlorine insecticides, and polycyclic aromatic hydrocarbons were correlated with home age (ρ > 0.2; P < .001), whereas concentrations of pyrethroid insecticides and polybrominated diphenyl ethers were not. Conclusions. Dust in older homes contains higher levels of multiple, persistent chemicals than does dust in newer homes. Further development of strategies to reduce chemical exposures for children living in older homes is warranted. PMID:24832145

Contamination and health risks of heavy metals in street dust from a coal-mining city in eastern China.

PubMed

Tang, Zhenwu; Chai, Miao; Cheng, Jiali; Jin, Jing; Yang, Yufei; Nie, Zhiqiang; Huang, Qifei; Li, Yanhua

2017-04-01

We collected street dust from Huainan, a typical coal-mining city in China, to investigate the contamination features and health risks of heavy metals. Concentrations of Co, Cr, Cu, Pb, As, and Sb were generally low to moderate, while pollution levels of Cd and Hg were moderate to high. Concentrations of Cd and Hg were associated with considerable health risks at 64.3% and 58.6% of sites, respectively. In particular, about a fifth of samples had associated high risks as a result of Hg contamination levels. Relative to other urban areas, the street dust from the mining area had no more severe metal pollution, which might be partly attributed to the deposition of coal dust onto street dusts. A source assessment indicated that metals in dust form Huainan were mainly derived from vehicular-related activities, industrial emissions, weathering of coal dust and natural soils, and coal combustion. Although the health risk levels from exposure to individual metals in dusts were low, the non-carcinogenic risks from multiple metals to local children exceeded the acceptable level (1.0), suggesting that the overall risk from exposure to multiple metals in dust is concerning. Copyright © 2016 Elsevier Inc. All rights reserved.

Revealing the Galactic Center in the Far-Infrared with SOFIA/FORCAST

NASA Astrophysics Data System (ADS)

Lau, Ryan M.; Herter, Terry; Morris, Mark; Li, Zhiyuan; Becklin, Eric; Adams, Joseph; Hankins, Matthew

2015-08-01

We present a summary of far-infrared imaging observations of the inner 40 pc of the Galactic center addressing the dense, dusty torus around Sgr A*, massive star formation, and dust production around massive stars and in the Sgr A East supernova remnant. Observations of warm dust emission were performed using the Faint Object Infrared Camera for the SOFIA Telescope (FORCAST). The Circumnuclear Ring (CNR) surrounding and heated by central cluster in the vicinity of Sgr A* shows no internal active star formation but does exhibit significant density “clumps,” a surprising result because tidal shearing should act quickly to smear out structure. G-0.02-0.07, a complex consisting of three compact HII regions and one ultracompact HII region, is site of the most recent confirmed star formation within ~10 pc of the Galactic center. Our observations reveal the dust morphologies and SEDs of the regions to constrain the composition and gas-to-dust mass ratios of the emitting dust and identify heating sources candidates from archival near-IR images. FORCAST observations Luminous Blue Variables (LBVs) located in and near the Quintuplet Cluster reveal the asymmetric, compressed shell of hot dust surrounding the Pistol Star and provide the first detection of the thermal emission from the symmetric, hot dust envelope surrounding G0.120-0.048. These two LBV’s have nebulae with similar quantities of dust (~0.02 M⊙) but exhibit contrasting appearances due to the external influence of their different environments. Finally, the far-infrared observations indicate the presence of ~0.02 M⊙ of warm (~100 K) dust in the hot interior of the ~10,000 yr-old SgrA East supernova remnant indicating the dust has survived the passage of the reverse shock. The results suggest that supernovae may indeed be the dominant dust production mechanism in the dense environment of early Universe galaxies.

Multiple piece turbine rotor blade

DOEpatents

Jones, Russell B; Fedock, John A

2013-05-21

A multiple piece turbine rotor blade with a shell having an airfoil shape and secured between a spar and a platform with the spar including a tip end piece. a snap ring fits around the spar and abuts against the spar tip end piece on a top side and abuts against a shell on the bottom side so that the centrifugal loads from the shell is passed through the snap ring and into the spar and not through a tip cap dovetail slot and projection structure.

OT2_nflagey_2: Capturing missing evolved stars in the Galactic plane

NASA Astrophysics Data System (ADS)

Flagey, N.

2011-09-01

We discovered more than 400 compact shells in the MIPSGAL 24 microns survey of the Galactic plane. About 15% of all these objects were already known as planetary nebulae, supernova remnants, Wolf-Rayet stars, and luminous blue variables. The unknown bubbles are expected to be envelopes of evolved stars that could account for the ``missing massive stars in the Galaxy. Indeed, recent spectroscopic follow-ups in the near-IR and mid-IR have revealed several dust-free planetary nebulae with very hot central white dwarf and significantly increased the number of WR and LBV candidates. Our OT1 Priority 1 proposal just provided us with a first observation in the PACS-SED B2A mode of one object, revealing only a strong [N II] 122 microns line. Without further spectral information, identification and modeling of the target are impossible. However, analysis of the PACS and SPIRE data from the HiGal survey has recently enabled us to measure much higher detection rates of the shells in the far-IR than with MIPS 70 microns. We are thus very confident that dust features and/or gas lines can be detected with the PACS and SPIRE spectrometers. Therefore, we request complementary PACS-SED B2B and SPIRE-FTS observations on our OT1 sample. The complete far-IR/submm spectrum of each target will allow its unequivocal identification thanks to comparison with spectra of known evolved stars from the MESS key program. We will also model with much detail the different phases of the envelopes, thanks to our expertise in circumstellar envelopes, dust models and photoionization codes.

On the Distribution of Dust in the ``Born-again'' Planetary Nebula A 30

NASA Astrophysics Data System (ADS)

Kerber, F.; Roth, M.; Rauch, T.; Ageorges, N.; Clayton, G. C.; De Marco, O.; Koller, J.

2009-09-01

The planetary nebula (PN) A30 consists of two nebular shells, one old, spherical, hydrogen-rich PN and a second, younger, H-poor, and dust-rich nebula which is the result of a very late thermal pulse (VLTP), a helium shell flash that occurred long after the central star (CS) had left the asymptotic giant branch (AGB). During the VLTP the CS returned to the AGB and became a ``born-again'' giant for a few years. During this extremely fast episode of stellar evolution a final mass-loss phase created the second, dusty PN a few thousand years ago. Such a VLTP should occur in 20% of all post-AGB stars according to theory but only a handful of ``born-again'' PNe are known, a discrepancy that remains unexplained so far. Moreover, the knots in A30 have been reported to be O-rich in clear disagreement with the C-rich composition predicted for a VLTP. In the case of A30 the ``born-again'' PN is highly filamentary and the individual knots clearly show signs of erosion from the fast wind of the -- yet again -- hot CS, such as ``cometary'' tails. While optical imaging (gas emission) obtained with the HST has provided excellent spatial resolution, near infrared imaging (dust emission) had been very limited in resolution so far. Our new PANIC/Magellan data quite literally shows the other side of the coin and as a consequence, for the first time we are able to shed light on the complex interplay between gas and dust in this PN. A30 forms an evolutionary sequence with V4334 Sgr (10 yrs after the flash) and V605 Aql (100 yrs) and, hence, provides valuable insight into the physics of the still poorly understood ``born-again'' PNe. This paper includes data gathered with the 6.5 meter Magellan Telescopes located at Las Campanas Observatory, Chile.

OISTER optical and near-infrared observations of the super-Chandrasekhar supernova candidate SN 2012dn: Dust emission from the circumstellar shell

NASA Astrophysics Data System (ADS)

Yamanaka, Masayuki; Maeda, Keiichi; Tanaka, Masaomi; Tominaga, Nozomu; Kawabata, Koji S.; Takaki, Katsutoshi; Kawabata, Miho; Nakaoka, Tatsuya; Ueno, Issei; Akitaya, Hiroshi; Nagayama, Takahiro; Takahashi, Jun; Honda, Satoshi; Omodaka, Toshihiro; Miyanoshita, Ryo; Nagao, Takashi; Watanabe, Makoto; Isogai, Mizuki; Arai, Akira; Itoh, Ryosuke; Ui, Takahiro; Uemura, Makoto; Yoshida, Michitoshi; Hanayama, Hidekazu; Kuroda, Daisuke; Ukita, Nobuharu; Yanagisawa, Kenshi; Izumiura, Hideyuki; Saito, Yoshihiko; Masumoto, Kazunari; Ono, Rikako; Noguchi, Ryo; Matsumoto, Katsura; Nogami, Daisaku; Morokuma, Tomoki; Oasa, Yumiko; Sekiguchi, Kazuhiro

2016-10-01

We present extensively dense observations of the super-Chandrasekhar supernova (SC SN) candidate SN 2012dn from -11 to +140 d after the date of its B-band maximum in the optical and near-infrared (NIR) wavelengths conducted through the OISTER ToO (Optical and Infrared Synergetic Telescopes for Education and Research Target of Opportunity) program. The NIR light curves and color evolutions up to 35 days after the B-band maximum provided an excellent match with those of another SC SN 2009dc, providing further support to the nature of SN 2012dn as an SC SN. We found that SN 2012dn exhibited strong excesses in the NIR wavelengths from 30 d after the B-band maximum. The H- and Ks-band light curves exhibited much later maximum dates at 40 and 70 d after the B-band maximum, respectively, compared with those of normal SNe Ia. The H- and Ks-band light curves subtracted by those of SN 2009dc displayed plateaued evolutions, indicating an NIR echo from the surrounding dust. The distance to the inner boundary of the dust shell is limited to 4.8-6.4 × 10-2 pc. No emission lines were found in its early phase spectra, suggesting that the ejecta-circumstellar material interaction could not occur. On the other hand, we found no signature that strongly supports the scenario of dust formation. The mass-loss rate of the pre-explosion system is estimated to be 10-6-10-5 M⊙ yr-1, assuming that the wind velocity of the system is 10-100 km s-1, which suggests that the progenitor of SN 2012dn could be a recurrent nova system. We conclude that the progenitor of this SC SN could be explained by the single-degenerate scenario.

Light Scattering by Fractal Dust Aggregates. II. Opacity and Asymmetry Parameter

NASA Astrophysics Data System (ADS)

Tazaki, Ryo; Tanaka, Hidekazu

2018-06-01

Optical properties of dust aggregates are important at various astrophysical environments. To find a reliable approximation method for optical properties of dust aggregates, we calculate the opacity and the asymmetry parameter of dust aggregates by using a rigorous numerical method, the T-Matrix Method, and then the results are compared to those obtained by approximate methods: the Rayleigh–Gans–Debye (RGD) theory, the effective medium theory (EMT), and the distribution of hollow spheres method (DHS). First of all, we confirm that the RGD theory breaks down when multiple scattering is important. In addition, we find that both EMT and DHS fail to reproduce the optical properties of dust aggregates with fractal dimensions of 2 when the incident wavelength is shorter than the aggregate radius. In order to solve these problems, we test the mean field theory (MFT), where multiple scattering can be taken into account. We show that the extinction opacity of dust aggregates can be well reproduced by MFT. However, it is also shown that MFT is not able to reproduce the scattering and absorption opacities when multiple scattering is important. We successfully resolve this weak point of MFT, by newly developing a modified mean field theory (MMF). Hence, we conclude that MMF can be a useful tool to investigate radiative transfer properties of various astrophysical environments. We also point out an enhancement of the absorption opacity of dust aggregates in the Rayleigh domain, which would be important to explain the large millimeter-wave opacity inferred from observations of protoplanetary disks.

Allergens in household dust and serological indicators of atopy and sensitization in Detroit children with history-based evidence of asthma.

PubMed

Williams, Ann Houston; Smith, James Travis; Hudgens, Edward E; Rhoney, Scott; Ozkaynak, Halûk; Hamilton, Robert G; Gallagher, Jane E

2011-09-01

Home exposure to allergens is an important factor in the development of sensitization and subsequent exacerbations of allergic asthma. We investigated linkages among allergen exposure, immunological measurements, and asthma by examining (1) reservoir dust allergen levels in homes, (2) associations between presence of allergens in homes and sensitization status of resident children, and (3) associations between asthma status and total IgE, atopy (by Phadiatop), and positive allergen-specific tests. The study protocol was approved by Institutional Review Boards (IRBs) of the University of North Carolina Chapel Hill; Westat, Inc.; and the US Environmental Protection Agency Human Research Protocol Office. Data were collected from questionnaires, serum analyses, and household vacuum dust. Children (n = 205) were predominately African American (AA) (85.4%) and 51.6% were asthmatic. Sera from 185 children and home dust samples (n = 141) were analyzed for total and specific IgE antibodies to allergens from cat and dog dander, cockroach, dust mites, mice, rats, and molds. Sixty percent of the homes had detectable levels of three or more dust allergens. The proportions of children with positive allergen-specific IgE tests were dust mite (32%), dog (28%), cat (23%), cockroach (18%), mouse (5%), rat (4%), and molds (24-36%). Children testing positive to a single allergen also had positive responses to other allergens. Those children with positive serum tests for cat, dog, and dust mite lived in homes with detectable levels of cat (51%), dog (90%), and dust mite (Der f 1) (92%) allergens. Correlations between children's specific IgE levels and dust levels were linearly related for dog (p < .04), but not for cat (p = .12) or dust mite (Der f 1) (p = .21). Odds ratios (95% CI) for the associations between asthma and serum-specific IgE were over 1.0 for cat, dog, dust mite (Der f 1), cockroach, and four types of molds. House dust allergen exposure levels, however, exhibited no differences between asthmatic and non-asthmatic homes. Both the co-occurrence of multiple allergens in dust and the high frequency of multiple allergen sensitizations indicate that a broad-based intervention aimed at reducing multiple allergens (pets, pests, and molds) would be more successful than any approach that aimed at reducing one type of allergen.

EVALUATION OF IMMUNOASSAY METHODS FOR DETERMINATION OF 3,5,6-TRICHLORO-2-PYRIDINOL IN MULTIPLE SAMPLE MEDIA

EPA Science Inventory

Two enzyme-linked immunosorbent assay (ELISA) methods were evaluated for the determination of 3,5,6-trichloro-2-pyridinol (3,5,6-TCP) in multiple sample media (dust, soil, food, and urine). The dust and soil samples were analyzed by the RaPID (TM) commercial immunoassay testing ...

IRC +10 216 in 3-D: morphology of a TP-AGB star envelope

PubMed Central

Guélin, M.; Patel, N.A.; Bremer, M.; Cernicharo, J.; Castro-Carrizo, A.; Pety, J.; Fonfría, J.P.; Agúndez, M.; Santander-García, M.; Quintana-Lacaci, G.; Velilla Prieto, L.; Blundell, R.; Thaddeus, P.

2017-01-01

During their late pulsating phase, AGB stars expel most of their mass in the form of massive dusty envelopes, an event that largely controls the composition of interstellar matter. The envelopes, however, are distant and opaque to visible and NIR radiation: their structure remains poorly known and the mass-loss process poorly understood. Millimeter-wave interferometry, which combines the advantages of longer wavelength, high angular resolution and very high spectral resolution is the optimal investigative tool for this purpose. Mm waves pass through dust with almost no attenuation. Their spectrum is rich in molecular lines and hosts the fundamental lines of the ubiquitous CO molecule, allowing a tomographic reconstruction of the envelope structure. The circumstellar envelope IRC +10 216 and its central star, the C-rich TP-AGB star closest to the Sun, are the best objects for such an investigation. Two years ago, we reported the first detailed study of the CO(2-1) line emission in that envelope, made with the IRAM 30-m telescope. It revealed a series of dense gas shells, expanding at a uniform radial velocity. The limited resolution of the telescope (HPBW 11″) did not allow us to resolve the shell structure. We now report much higher angular resolution observations of CO(2-1), CO(1-0), CN(2-1) and C4H(24-23) made with the SMA, PdB and ALMA interferometers (with synthesized half-power beamwidths of 3″, 1″ and 0.3″, respectively). Although the envelope appears much more intricate at high resolution than with an 11″ beam, its prevailing structure remains a pattern of thin, nearly concentric shells. The average separation between the brightest CO shells is 16″ in the outer envelope, where it appears remarkably constant. Closer to the star (< 40″), the shell pattern is denser and less regular, showing intermediary arcs. Outside the small (r < 0.3″) dust formation zone, the gas appears to expand radially at a constant velocity, 14.5 km s−1, with small turbulent motions. Based on that property, we have reconstructed the 3-D structure of the outer envelope and have derived the gas temperature and density radial profiles in the inner (r < 25″) envelope. The shell-intershell density contrast is found to be typically 3. The over-dense shells have spherical or slightly oblate shapes and typically extend over a few steradians, implying isotropic mass loss. The regular spacing of shells in the outer envelope supports the model of a binary star system with a period of 700 years and a near face-on elliptical orbit. The companion fly-by triggers enhanced episodes of mass loss near periastron. The densification of the shell pattern observed in the central part of the envelope suggests a more complex scenario for the last few thousand years. ⋆ PMID:29456257

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

Cacciari, C.; Clementini, G.

Attention is given to the folowing topics: population I and II variable stars; LP variables, the sun, and mass determination; and predegenerate and degenerate variables. Particular papers are presented on alternative evolutionary approaches to the absolute magnitude of the RR Lyrae variables; the evolution of the Cepheid stars; nonradial pulsations in rapidly rotating Delta Scuti stars; dynamical models of dust shells around Mira variables; and pulsations of central stars of planetary nebulae.

Comment on self-consistent model of black hole formation and evaporation

NASA Astrophysics Data System (ADS)

Ho, Pei-Ming

2015-08-01

In an earlier work, Kawai et al. proposed a model of black-hole formation and evaporation, in which the geometry of a collapsing shell of null dust is studied, including consistently the back reaction of its Hawking radiation. In this note, we illuminate the implications of their work, focusing on the resolution of the information loss paradox and the problem of the firewall.

Chandra Observations and Models of the Mixed Morphology Supernova Remnant W44: Global Trends

NASA Technical Reports Server (NTRS)

Shelton, R. L.; Kuntz, K. D.; Petre, R.

2004-01-01

We report on the Chandra observations of the archetypical mixed morphology (or thermal composite) supernova remnant, W44. As with other mixed morphology remnants, W44's projected center is bright in thermal X-rays. It has an obvious radio shell, but no discernable X-ray shell. In addition, X-ray bright knots dot W44's image. The spectral analysis of the Chandra data show that the remnant s hot, bright projected center is metal-rich and that the bright knots are regions of comparatively elevated elemental abundances. Neon is among the affected elements, suggesting that ejecta contributes to the abundance trends. Furthermore, some of the emitting iron atoms appear to be underionized with respect to the other ions, providing the first potential X-ray evidence for dust destruction in a supernova remnant. We use the Chandra data to test the following explanations for W44's X-ray bright center: 1.) entropy mixing due to bulk mixing or thermal conduction, 2.) evaporation of swept up clouds, and 3.) a metallicity gradient, possibly due to dust destruction and ejecta enrichment. In these tests, we assume that the remnant has evolved beyond the adiabatic evolutionary stage, which explains the X-ray dimness of the shell. The entropy mixed model spectrum was tested against the Chandra spectrum for the remnant's projected center and found to be a good match. The evaporating clouds model was constrained by the finding that the ionization parameters of the bright knots are similar to those of the surrounding regions. While both the entropy mixed and the evaporating clouds models are known to predict centrally bright X-ray morphologies, their predictions fall short of the observed brightness gradient. The resulting brightness gap can be largely filled in by emission from the extra metals in and near the remnant's projected center. The preponderance of evidence (including that drawn from other studies) suggests that W44's remarkable morphology can be attributed to dust destruction and ejecta enrichment within an entropy mixed, adiabatic phase supernova remnant. The Chandra data prompts a new question - by what astrophysical mechanisms are the metals distributed so inhomogeneously in the supernova remnant.

Electrophoretic manipulation of multiple-emulsion droplets

NASA Astrophysics Data System (ADS)

Schoeler, Andreas M.; Josephides, Dimitris N.; Chaurasia, Ankur S.; Sajjadi, Shahriar; Mesquida, Patrick

2014-02-01

Electrophoretic manipulation of multiple-emulsion oil-in-water-in-oil (O/W)/O and water-in-oil-in-water-in-oil (W/O/W)/O core-shell droplets is shown. It was found that the electrophoretic mobility of the droplets is determined solely by the outer water shell, regardless of size or composition of the inner droplets. It was observed that the surface charge of the outer water shell can be changed and the polarity can be reversed through contact with a biased electrode in a similar way as with simple W/O droplets. Furthermore, addition of the anionic surfactant, sodium dodecyl sulfate to the outer water shell reverses the initial polarity and hence, electrophoretic mobility of the core-shell droplets before contact with an electrode. The results have practical implications for the manipulation of oil droplets in a continuous oil phase.

The Late-Time Evolution of SN 2002hh

NASA Astrophysics Data System (ADS)

Clayton, G. C.; Welch, D. L.

2005-12-01

We present new spectroscopic and photometric observations of the interesting Type II-P supernova, SN 2002hh, in NGC 6946. Gemini/GMOS-N has been used to acquire visible spectra and also g'r'i' photometry covering 5 epochs between August 2004 and October 2005, following the evolution of the supernova from 650 to 1050 d since its initial explosion. Supernova spectra obtained 3 years after outburst are rare. In addition, data have been obtained at several epochs in the JHK bands using the Steward 90" with the 256x256 imager and with Gemini/NIRI. Dust emission from SN 2002hh has been detected at mid-infrared wavelengths by SST/IRAC and confirmed by higher angular resolution Gemini/Michelle observations (Barlow et al. 2005, ApJ, 627, L113). There is a pre-existing optically thick dust shell having a mass of ˜0.1 Msun, suggesting a massive M supergiant or luminous blue variable precursor. However, the formation of new dust in the ejecta of SN 2002hh has not been ruled out. The IR emission from any such new dust would be swamped by the emission from the existing circumstellar dust. The new data, presented here, are being used to investigate the late-time evolution of SN 2002hh and whether new dust has been formed in its ejecta. In particular, we are looking for changes in the H-alpha emission line profiles and for variations in brightness due to changes in the extinction and emission due to dust. This study is partially supported by the Natural Sciences and Engineering Research Council of Canada (NSERC).

Balancing Newtonian gravity and spin to create localized structures

NASA Astrophysics Data System (ADS)

Bush, Michael; Lindner, John

2015-03-01

Using geometry and Newtonian physics, we design localized structures that do not require electromagnetic or other forces to resist implosion or explosion. In two-dimensional Euclidean space, we find an equilibrium configuration of a rotating ring of massive dust whose inward gravity is the centripetal force that spins it. We find similar solutions in three-dimensional Euclidean and hyperbolic spaces, but only in the limit of vanishing mass. Finally, in three-dimensional Euclidean space, we generalize the two-dimensional result by finding an equilibrium configuration of a spherical shell of massive dust that supports itself against gravitational collapse by spinning isoclinically in four dimensions so its three-dimensional acceleration is everywhere inward. These Newtonian ``atoms'' illuminate classical physics and geometry.

Hypervelocity Dust Injection for Plasma Diagnostic Applications

NASA Astrophysics Data System (ADS)

Ticos, Catalin

2005-10-01

Hypervelocity micron-size dust grain injection was proposed for high-temperature magnetized plasma diagnosis. Multiple dust grains are launched simultaneously into high temperature plasmas at several km/s or more. The hypervelocity dust grains are ablated by the electron and ion fluxes. Fast imaging of the resulting luminous plumes attached to each grain is expected to yield local magnetic field vectors. Combination of multiple local magnetic field vectors reproduces 2D or even 3D maps of the internal magnetic field topology. Key features of HDI are: (1) a high spatial resolution, due to a relatively small transverse size of the elongated tail, and (2) a small perturbation level, as the dust grains introduce negligible number of particles compared to the plasma particle inventory. The latter advantage, however, could be seriously compromised if the gas load from the accelerator has an unobstructed access to the diagnosed plasma. Construction of a HDI diagnostic for National Spherical Torus Experiment (NSTX), which includes a coaxial plasma gun for dust grain acceleration, is underway. Hydrogen and deuterium gas discharges inside accelerator are created by a ˜ 1 mF capacitor bank pre-charged up to 10 kV. The diagnostic apparatus also comprises a dust dispenser for pre-loading the accelerator with dust grains, and an imaging system that has a high spatial and temporal resolution.

Large Interstellar Polarisation Survey. II. UV/optical study of cloud-to-cloud variations of dust in the diffuse ISM

NASA Astrophysics Data System (ADS)

Siebenmorgen, R.; Voshchinnikov, N. V.; Bagnulo, S.; Cox, N. L. J.; Cami, J.; Peest, C.

2018-03-01

It is well known that the dust properties of the diffuse interstellar medium exhibit variations towards different sight-lines on a large scale. We have investigated the variability of the dust characteristics on a small scale, and from cloud-to-cloud. We use low-resolution spectro-polarimetric data obtained in the context of the Large Interstellar Polarisation Survey (LIPS) towards 59 sight-lines in the Southern Hemisphere, and we fit these data using a dust model composed of silicate and carbon particles with sizes from the molecular to the sub-micrometre domain. Large (≥6 nm) silicates of prolate shape account for the observed polarisation. For 32 sight-lines we complement our data set with UVES archive high-resolution spectra, which enable us to establish the presence of single-cloud or multiple-clouds towards individual sight-lines. We find that the majority of these 35 sight-lines intersect two or more clouds, while eight of them are dominated by a single absorbing cloud. We confirm several correlations between extinction and parameters of the Serkowski law with dust parameters, but we also find previously undetected correlations between these parameters that are valid only in single-cloud sight-lines. We find that interstellar polarisation from multiple-clouds is smaller than from single-cloud sight-lines, showing that the presence of a second or more clouds depolarises the incoming radiation. We find large variations of the dust characteristics from cloud-to-cloud. However, when we average a sufficiently large number of clouds in single-cloud or multiple-cloud sight-lines, we always retrieve similar mean dust parameters. The typical dust abundances of the single-cloud cases are [C]/[H] = 92 ppm and [Si]/[H] = 20 ppm.

Large Interstellar Polarisation Survey:The Dust Elongation When Combining Optical-Submm Polarisation

NASA Astrophysics Data System (ADS)

Siebenmorgen, Ralf; Voschinnikov, N.; Bagnulo, S.; Cox, N.; Cami, J.

2017-10-01

The Planck mission has shown that dust properties of the diffuse ISM varies on a large scale and we present variability on a small scales. We present FORS spectro-polarimetry obtained by the Large Interstellar Polarisation Survey along 60 sight-lines. We fit these combined with extinction data by a silicate and carbon dust model with grain sizes ranging from the molecular to the sub-mic. domain. Large silicates of prolate shape account for the observed polarisation. For 37 sight-lines we complement our data set with UVES high-resolution spectra that establish the presence of single or multiple clouds along individual sight-lines. We find correlations between extinction and Serkowski parameters with the dust model and that the presence of multiple clouds depolarises the incoming radiation. However, there is a degeneracy in the dust model between alignment efficiency and the elongation of the grains. This degeneracy can be broken by combining polarization data in the optical-to-submm. This is of wide general interest as it improves the accuracy of deriving dust masses. We show that a flat IR/submm polarisation spectrum with substantial polarisation is predicted from dust models.

COMPARISON OF IMMUNOASSAY AND GAS CHROMATOGRAPHY/MASS SPECTROMETRY METHODS FOR MEASURING 3,5,6-TRICHLORO-2PYRIDINOL IN MULTIPLE SAMPLE MEDIA

EPA Science Inventory

Two enzyme-linked immunosorbent assay (ELISA) methods were evaluated for the determination of 3,5,6-trichloro-2-pyridinol (3,5,6-TCP) in multiple sample media (dust, soil, food, and urine). The dust and soil samples were analyzed by a commercial RaPID immunoassay testing kit. ...

Importance of dust storms in the diagenesis of sandstones: a case study, Entrada sandstone in the Ghost Ranch area, New Mexico, USA

NASA Astrophysics Data System (ADS)

Orhan, Hükmü

1992-04-01

The importance of dust storms on geological processes has only been studied recently. Case-hardening, desert-varnish formation, duricrust development, reddening and cementation of sediments and caliche formation, are some important geological processes related to dust storms. Dust storms can also be a major source for cements in aeolian sandstones. The Jurassic aeolian Entrada Formation in the Ghost Ranch area is composed of quartz with minor amounts of feldspar and rock fragments, and is cemented with smectite as grain coatings and calcite and kaolinite as pore fillings. Smectite shows a crinkly and honeycomb-like morphology which points to an authigenic origin. The absence of smectite as framework grains and the presence of partially dissolved grains, coated with smectite and smectite egg-shells, indicate an external source. Clay and fine silt-size particles are believed to be the major source for cements, smectite and calcite in the Entrada Formation. The common association of kaolinite with altered feldspar, and the absence of kaolinite in spots heavily cemented with calcite, lead to the conclusions that the kaolinite formation postdates carbonates and that framework feldspar grains were the source of kaolinite.

Early dust formation and a massive progenitor for SN 2011ja?

NASA Astrophysics Data System (ADS)

Andrews, J. E.; Krafton, Kelsie M.; Clayton, Geoffrey C.; Montiel, E.; Wesson, R.; Sugerman, Ben E. K.; Barlow, M. J.; Matsuura, M.; Drass, H.

2016-04-01

SN 2011ja was a bright (I = -18.3) Type II supernova occurring in the nearby edge on spiral galaxy NGC 4945. Flat-topped and multipeaked H α and H β spectral emission lines appear between 64 and 84 d post-explosion, indicating interaction with a disc-like circumstellar medium inclined ˜45° from edge-on. After day 84, an increase in the H- and K-band flux along with heavy attenuation of the red wing of the emission lines are strong indications of early dust formation, likely located in the cool dense shell created between the forward shock of the SN ejecta and the reverse shock created as the ejecta plows into the existing circumstellar material. Radiative transfer modelling reveals both ≈1 × 10-5 M⊙ of pre-existing dust located ˜1016.7 cm away and up to ≈6 × 10-4 M⊙ of newly formed dust. Spectral observations after 1.5 yr reveal the possibility that the fading SN is located within a young (3-6 Myr) massive stellar cluster, which when combined with tentative 56Ni mass estimates of 0.2 M⊙ may indicate a massive (≥25 M⊙) progenitor for SN 2011ja.

A high-resolution infrared spectrum of IRC +10216. [carbon star immersed in expanding gas/dust shell

NASA Technical Reports Server (NTRS)

Barnes, T. G.; Hinkle, K. H.; Lambert, D. L.; Beer, R.

1977-01-01

The IR-emitting core and shell of IRC +10216 are investigated using a high-resolution spectrum covering the wavelength interval between 3 and 5 microns. Line identifications made or confirmed include those due to (C-12)(O-16), (C-13)(O-16), (C-12)(O-17), and (C-12)(O-18). A mean heliocentric velocity of about -32 km/s is obtained from the 42 least blended (C-12)O and (C-13)O lines, and the following isotopic abundance ratios are derived by comparing equivalent widths of the observed lines: C-12/C-13, C-12/C-14, O-16/O-17, and O-17/O-18. The structure of the expanding gas shell is examined, an explanation is offered for the lack of P Cygni profiles in the spectrum, and an unsuccessful search for other molecules is briefly discussed. It is concluded that a low C-12/C-13 ratio is not necessarily a signature of a carbon star.

Evaluation of sanitizers for inactivating Salmonella on in-shell pecans and pecan nutmeats.

PubMed

Beuchat, Larry R; Mann, David A; Alali, Walid Q

2012-11-01

Chlorine, organic acids, and water extracts of inedible pecan components were tested for effectiveness in killing Salmonella on pecans. In-shell pecans and nutmeats (U.S. Department of Agriculture medium pieces) were immersion inoculated with a mixture of five Salmonella serotypes, dried to 3.7% moisture, and stored at 4°C for 3 to 6 weeks. In-shell nuts were immersed in chlorinated water (200, 400, and 1,000 μg/ml), lactic acid (0.5, 1, and 2%), and levulinic acid (0.5, 1, and 2%) with and without 0.05% sodium dodecyl sulfate (SDS), and a mixed peroxyacid sanitizer (Tsunami 200, 40 μg/ml) for up to 20 min at 21°C. The rate of reduction of free chlorine in conditioning water decreased as the ratio of in-shell nuts/water was increased. The rate of reduction was more rapid when nuts were not precleaned before treatment. The initial population of Salmonella on in-shell nuts (5.9 to 6.3 log CFU/g) was reduced by 2.8 log CFU/g after treating with chlorinated water (1,000 μg/ml). Treatment with 2% lactic acid plus SDS or 2% levulinic acid plus SDS reduced the pathogen by 3.7 and 3.4 log CFU/g, respectively. Lactic and levulinic acids (2%) without SDS were less effective (3.3- and 2.1-log CFU/g reductions, respectively) than acids with SDS. Treatment with Tsunami 200 resulted in a 2.4-log CFU/g reduction. In-shell nuts and nutmeats were immersed in water extracts of ground pecan shucks (hulls), shells, a mixture of shells and pith, and pith. The general order of lethality of extracts to Salmonella was shuck < shell-pith ≤ shell ≤ pith < chlorine (400 μg/ml) and shuck < shell ≤ pith = shell-pith < chlorine (400 μg/ml). Results emphasize the importance of removing soil and dust on in-shell pecans before conditioning in chlorinated water and the need for sanitizers with increased effectiveness in killing Salmonella on pecans.

One-step formation of multiple emulsions in microfluidics.

PubMed

Abate, Adam R; Thiele, Julian; Weitz, David A

2011-01-21

We present a robust way to create multiple emulsions with controllable shell thicknesses that can vary over a wide range. We use a microfluidic device to create a coaxial jet of immiscible fluids; using a dripping instability, we break the jet into multiple emulsions. By controlling the thickness of each layer of the jet, we adjust the thicknesses of the shells of the multiple emulsions. The same method is also effective in creating monodisperse emulsions from fluids that cannot otherwise be controllably emulsified, such as, for example, viscoelastic fluids.

Dance of the Light Echoes

NASA Technical Reports Server (NTRS)

2008-01-01

[figure removed for brevity, see original site] Click on image for larger poster version

This composite image from NASA's Spitzer Space Telescope shows the remnant of a star that exploded, called Cassiopeia A (center) and its surrounding 'light echoes' -- dances of light through dusty clouds, created when stars blast apart. The light echoes are colored and the surrounding clouds of dust are gray.

In figure 1, dramatic changes are highlighted in phenomena referred to as light echoes (colored areas) around the Cassiopeia A supernova remnant (center). Cassiopeia A is the remnant of a once massive star that died in a violent supernova explosion. It consists of a dead star, called a neutron star, and a surrounding shell of material that was blasted off as the star died.

A light echo occurs when a star explodes, acting like a cosmic flashbulb. The light from this explosion zips through nearby dust clumps, illuminating and heating them up slightly. This brief period of warming causes them to glow in infrared, like a chain of Christmas bulbs lighting up one by one. The result is an optical illusion, in which the dust appears to be flying outward at the speed of light. In figure 1, this apparent motion can be seen here by the shift in colored dust clumps

Cassiopeia A is the remnant of a once massive star that died in a violent supernova explosion. It consists of a dead star, called a neutron star, and a surrounding shell of material that was blasted off as the star died. This remnant is located 11,000 light-years away in the northern constellation Cassiopeia.

This composite consists of six processed images taken over a time span of three years. Dust features that have not changed over time appear gray, while those that have changed are colored blue or orange. Bluer colors represent an earlier time and redder ones, a later time. The progression of the light echo through the dust can be seen here by the shift in colored dust clumps.

This light echo is the largest ever seen, stretching more than 300 light-years away from Cassiopeia A. If viewed from Earth, the entire frame would take up the same amount of space as seven full moons. The supernova remnant is located 11,000 light-years away in the northern constellation Cassiopeia.

The earliest Spitzer image shown here was taken in February 2005, and the latest one in January 2008. The image was processed to emphasize the light echo by enhancing the areas that change, which appear in color, and dimming regions that remain constant, seen in grayscale. Spurious color artifacts such as diffraction spikes around stars were removed by hand.

On the properties of dust and gas in the environs of V838 Monocerotis

NASA Astrophysics Data System (ADS)

Exter, K. M.; Cox, N. L. J.; Swinyard, B. M.; Matsuura, M.; Mayer, A.; De Beck, E.; Decin, L.

2016-12-01

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 dust 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 dust 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 dust in the environs (≈2.7 pc) surrounding V838 Mon. The surface-integrated infrared flux (signifying the thermal light echo), and derived dust 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 warm dust 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 warm (Tkin ≈ 400 K) zone that is associated with the extended environment of V838 Mon within a region of radius of ≈210 AU. The SiO lines arise from a warm/hot zone. We did not fit the lines of H2O as they are far more dependent on the model assumed. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

The Herschel Planetary Nebula Survey (HerPlaNS). I. Data overview and analysis demonstration with NGC 6781

NASA Astrophysics Data System (ADS)

Ueta, T.; Ladjal, D.; Exter, K. M.; Otsuka, M.; Szczerba, R.; Siódmiak, N.; Aleman, I.; van Hoof, P. A. M.; Kastner, J. H.; Montez, R.; McDonald, I.; Wittkowski, M.; Sandin, C.; Ramstedt, S.; De Marco, O.; Villaver, E.; Chu, Y.-H.; Vlemmings, W.; Izumiura, H.; Sahai, R.; Lopez, J. A.; Balick, B.; Zijlstra, A.; Tielens, A. G. G. M.; Rattray, R. E.; Behar, E.; Blackman, E. G.; Hebden, K.; Hora, J. L.; Murakawa, K.; Nordhaus, J.; Nordon, R.; Yamamura, I.

2014-05-01

Context. This is the first of a series of investigations into far-IR characteristics of 11 planetary nebulae (PNe) under the Herschel Space Observatory open time 1 program, Herschel Planetary Nebula Survey (HerPlaNS). Aims: Using the HerPlaNS data set, we look into the PN energetics and variations of the physical conditions within the target nebulae. In the present work, we provide an overview of the survey, data acquisition and processing, and resulting data products. Methods: We performed (1) PACS/SPIRE broadband imaging to determine the spatial distribution of the cold dust component in the target PNe and (2) PACS/SPIRE spectral-energy-distribution and line spectroscopy to determine the spatial distribution of the gas component in the target PNe. Results: For the case of NGC 6781, the broadband maps confirm the nearly pole-on barrel structure of the amorphous carbon-rich dust shell and the surrounding halo having temperatures of 26-40 K. The PACS/SPIRE multiposition spectra show spatial variations of far-IR lines that reflect the physical stratification of the nebula. We demonstrate that spatially resolved far-IR line diagnostics yield the (Te, ne) profiles, from which distributions of ionized, atomic, and molecular gases can be determined. Direct comparison of the dust and gas column mass maps constrained by the HerPlaNS data allows to construct an empirical gas-to-dust mass ratio map, which shows a range of ratios with the median of 195 ± 110. The present analysis yields estimates of the total mass of the shell to be 0.86 M⊙, consisting of 0.54 M⊙ of ionized gas, 0.12 M⊙ of atomic gas, 0.2 M⊙ of molecular gas, and 4 × 10-3 M⊙ of dust grains. These estimates also suggest that the central star of about 1.5 M⊙ initial mass is terminating its PN evolution onto the white dwarf cooling track. Conclusions: The HerPlaNS data provide various diagnostics for both the dust and gas components in a spatially resolved manner. In the forthcoming papers of the HerPlaNS series we will explore the HerPlaNS data set fully for the entire sample of 11 PNe. Herschel is an ESA Space Observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.Table 2 and appendices are available in electronic form at http://www.aanda.org

CO OBSERVATIONS AND INVESTIGATION OF TRIGGERED STAR FORMATION TOWARD THE N10 INFRARED BUBBLE AND SURROUNDINGS

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

Gama, D. R. G.; Lepine, J. R. D.; Mendoza, E.

We studied the environment of the dust bubble N10 in molecular emission. Infrared bubbles, first detected by the GLIMPSE survey at 8.0 μ m, are ideal regions to investigate the effect of the expansion of the H ii region on its surroundings and the eventual triggering of star formation at its borders. In this work, we present a multi-wavelength study of N10. This bubble is especially interesting because infrared studies of the young stellar content suggest a scenario of ongoing star formation, possibly triggered on the edge of the H ii region. We carried out observations of {sup 12}CO(1-0) andmore » {sup 13}CO(1-0) emission at PMO 13.7 m toward N10. We also analyzed the IR and sub-millimeter emission on this region and compare those different tracers to obtain a detailed view of the interaction between the expanding H ii region and the molecular gas. We also estimated the parameters of the denser cold dust condensation and the ionized gas inside the shell. Bright CO emission was detected and two molecular clumps were identified from which we have derived physical parameters. We also estimate the parameters for the densest cold dust condensation and for the ionized gas inside the shell. The comparison between the dynamical age of this region and the fragmentation timescale favors the “Radiation-Driven Implosion” mechanism of star formation. N10 is a case of particular interest with gas structures in a narrow frontier between the H ii region and surrounding molecular material, and with a range of ages of YSOs situated in the region, indicating triggered star formation.« less

Novae as distance indicators

NASA Technical Reports Server (NTRS)

Ford, Holland C.; Ciardullo, Robin

1988-01-01

Nova shells are characteristically prolate with equatorial bands and polar caps. Failure to account for the geometry can lead to large errors in expansion parallaxes for individual novae. When simple prescriptions are used for deriving expansion parallaxes from an ensemble of randomly oriented prolate spheroids, the average distance will be too small by factors of 10 to 15 percent. The absolute magnitudes of the novae will be underestimated and the resulting distance scale will be too small by the same factors. If observations of partially resolved nova shells select for large inclinations, the systematic error in the resulting distance scale could easily be 20 to 30 percent. Extinction by dust in the bulge of M31 may broaden and shift the intrinsic distribution of maximum nova magnitudes versus decay rates. We investigated this possibility by projecting Arp's and Rosino's novae onto a composite B - 6200A color map of M31's bulge. Thirty two of the 86 novae projected onto a smooth background with no underlying structure due to the presence of a dust cloud along the line of sight. The distribution of maximum magnitudes versus fade rates for these unreddened novae is indistinguishable from the distribution for the entire set of novae. It is concluded that novae suffer very little extinction from the filamentary and patchy distribution of dust seen in the bulge of M31. Time average B and H alpha nova luminosity functions are potentially powerful new ways to use novae as standard candles. Modern CCD observations and the photographic light curves of M31 novae found during the last 60 years were analyzed to show that these functions are power laws. Consequently, unless the eruption times for novae are known, the data cannot be used to obtain distances.

Molecules and Dust in the Humunculus: Ejecta of Eta Carinae

NASA Technical Reports Server (NTRS)

Gull, T.

2007-01-01

In the 18401s, Eta Carinae ejected massive amounts of nitrogen-rich, carbon- and oxygen-poor material which we see as the hourglass-shaped Homunculus. With the Hubble Space Telescope Imaging Spectrograph, we detected multiple shells in line of sight, the most massive and intriguing being at -513 km/s. Numerous lines of Fe I, Fe II, Ni II, Cr II, Sc II, Sr II, Ti II, V II, etc are identified as well as nearly a thousand H2 lines. The metals have energy level populations consistent with 760K and excited by photons < 8.5eV. We have now identified CH, CH+, OH, and NH at the same velocity, but at 60K, suggesting stratification in the outer ejecta. Analysis of the interior, photoionized emission hourglass structure, known as the Little Homunculus, indicates He, N overabundances and C, 0 underabundances (approximately 1/80 solar). A skirt of neutral and partially ionized gas lies between the lobes of the hourglasses. A portion is seen as the Strontium Filament, a metal- ionized, neutral hydrogen structure. Relative abundances of TiNi are 1/80 solar, CrNi are 1/20 solar. This complex of ejecta appears to have been ejected by a massive star(s) at the end of the hydrogen-burning phase when convection led to overproduction of nitrogen at the expense of carbon and oxygen. Given the underabundances of carbon and oxygen, the chemistry of this system is quite different to the normal ISM, leading to a nitrogen- dominated chemistry. What little C and 0 that is formed is immediately taken up by SiO and Al0 molecules leading to a very different gas/dust ratio than the normal ISM. Dust in this ejecta is abundance, but known to be very grey in character. Observations with HST/STIS and VLT/UVES will be presented along with simple physical models and CLOUD modeling. Insight by the participants will be solicited.

Gravitationally Unstable Condensations Revealed by ALMA in the TUKH122 Prestellar Core in the Orion A Cloud

NASA Astrophysics Data System (ADS)

Ohashi, Satoshi; Sanhueza, Patricio; Sakai, Nami; Kandori, Ryo; Choi, Minho; Hirota, Tomoya; Nguyễn-Lu’o’ng, Quang; Tatematsu, Ken’ichi

2018-04-01

We have investigated the TUKH122 prestellar core in the Orion A cloud using ALMA 3 mm dust continuum, N2H+ (J = 1‑0), and CH3OH ({J}K={2}K-{1}K) molecular-line observations. Previous studies showed that TUKH122 is likely on the verge of star formation because the turbulence is almost dissipated and chemically evolved among other starless cores in the Orion A cloud. By combining ALMA 12 m and ACA data, we recover extended emission with a resolution of ∼5″ corresponding to 0.01 pc and identify six condensations with a mass range of 0.1–0.4 M ⊙ and a radius of ≲0.01 pc. These condensations are gravitationally bound following a virial analysis and are embedded in the filament, including the elongated core with a mass of ∼29 M ⊙ and a radial density profile of r ‑1.6 derived by Herschel. The separation of these condensations is ∼0.035 pc, consistent with the thermal Jeans length at a density of 4.4 × 105 cm‑3. This density is similar to the central part of the core. We also find a tendency for the N2H+ molecule to deplete at the dust peak condensation. This condensation may be beginning to collapse because the line width becomes broader. Therefore, the fragmentation still occurs in the prestellar core by thermal Jeans instability, and multiple stars are formed within the TUKH122 prestellar core. The CH3OH emission shows a large shell-like distribution and surrounds these condensations, suggesting that the CH3OH molecule formed on dust grains is released into the gas phase by nonthermal desorption such as photoevaporation caused by cosmic-ray-induced UV radiation.

Effects of multiple resistive shells and transient electromagnetic torque on the dynamics of mode locking in reversed field pinch plasmas

NASA Astrophysics Data System (ADS)

Guo, S. C.; Chu, M. S.

2002-11-01

The effects of multiple resistive shells and transient electromagnetic torque on the dynamics of mode locking in the reversed field pinch (RFP) plasmas are studied. Most RFP machines are equipped with one or more metal shells outside of the vacuum vessel. These shells have finite resistivities. The eddy currents induced in each of the shells contribute to the braking electromagnetic (EM) torque which slows down the plasma rotation. In this work we study the electromagnetic torque acting on the plasma (tearing) modes produced by a system of resistive shells. These shells may consist of several nested thin shells or several thin shells enclosed within a thick shell. The dynamics of the plasma mode is investigated by balancing the EM torque from the resistive shells with the plasma viscous torque. Both the steady state theory and the time-dependent theory are developed. The steady state theory is shown to provide an accurate account of the resultant EM torque if (dω/dt)ω-2≪1 and the time scale of interest is much longer than the response (L/R) time of the shell. Otherwise, the transient theory should be adopted. As applications, the steady state theory is used to evaluate the changes of the EM torque response from the resistive shells in two variants of two RFP machines: (1) modification from Reversed Field Experiment (RFX) [Gnesotto et al., Fusion Eng. Des. 25, 335 (1995)] to the modified RFX: both of them are equipped with one thin shell plus one thick shell; (2) modification from Extrap T2 to Extrap T2R [Brunsell et al., Plasma Phys. Controlled Fusion 43, 1457 (2001)]: both of them are equipped with two thin shells. The transient theory has been applied numerically to study the time evolution of the EM torque during the unlocking of a locked tearing mode in the modified RFX.

Thermal effectiveness of multiple shell and tube pass TEMA E heat exchangers

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

Pignotti, A.; Tamborenea, P.I.

1988-02-01

The thermal effectiveness of a TEMAE shell-and-tube heat exchanger, with one shell pass and an arbitrary number of tube passes, is determined under the usual simplifying assumptions of perfect transverse mixing of the shell fluid, no phase change, and temperature independence of the heat capacity rates and the heat transfer coefficient. A purely algebraic solution is obtained for the effectiveness as a functions of the heat capacity rate ratio and the number of heat transfer units. The case with M shell passes and N tube passes is easily expressed in terms of the single-shell-pass case.

The extinction and dust-to-gas structure of the planetary nebula NGC 7009 observed with MUSE

NASA Astrophysics Data System (ADS)

Walsh, J. R.; Monreal-Ibero, A.; Barlow, M. J.; Ueta, T.; Wesson, R.; Zijlstra, A. A.

2016-04-01

Context. Dust plays a significant role in planetary nebulae. Dust ejected with the gas in the asymptotic giant branch (AGB) phase is subject to the harsh environment of the planetary nebula (PN) while the star is evolving towards a white dwarf. Dust surviving the PN phase contributes to the dust content of the interstellar medium. Aims: The morphology of the internal dust extinction has been mapped for the first time in a PN, the bright nearby Galactic nebula NGC 7009. The morphologies of the gas, dust extinction and dust-to-gas ratio are compared to the structural features of the nebula. Methods: Emission line maps in H Balmer and Paschen lines were formed from analysis of MUSE cubes of NGC 7009 observed during science verification of the instrument. The measured electron temperature and density from the same cube were employed to predict the theoretical H line ratios and derive the extinction distribution across the nebula. After correction for the interstellar extinction to NGC 7009, the internal AV/NH has been mapped for the first time in a PN. Results: The extinction map of NGC 7009 has considerable structure, broadly corresponding to the morphological features of the nebula. The dust-to-gas ratio, AV/NH, increases from 0.7 times the interstellar value to >5 times from the centre towards the periphery of the ionized nebula. The integrated AV/NH is about 2× the mean ISM value. A large-scale feature in the extinction map is a wave, consisting of a crest and trough, at the rim of the inner shell. The nature of this feature is investigated and instrumental and physical causes considered; no convincing mechanisms were identified to produce this feature, other than AGB mass loss variations. Conclusions: Extinction mapping from H emission line imaging of PNe with MUSE provides a powerful tool for revealing the properties of internal dust and the dust-to-gas ratio. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programme 060.A-9347(A).

Near-infrared and optical studies of the highly obscured nova V1831 Aquilae (Nova Aquilae 2015)

NASA Astrophysics Data System (ADS)

Banerjee, D. P. K.; Srivastava, Mudit K.; Ashok, N. M.; Munari, U.; Hambsch, F.-J.; Righetti, G. L.; Maitan, A.

2018-01-01

Near-infrared (NIR) and optical photometry and spectroscopy are presented for the nova V1831 Aquilae, covering the early decline and dust-forming phases during the first ∼90 d after its discovery. The nova is highly reddened due to interstellar extinction. Based solely on the nature of the NIR spectrum, we are able to classify the nova to be of the Fe II class. The distance and extinction to the nova are estimated to be 6.1 ± 0.5 kpc and Av ∼ 9.02, respectively. Lower limits of the electron density, emission measure and ionized ejecta mass are made from a Case B analysis of the NIR Brackett lines, while the neutral gas mass is estimated from the optical [O I] lines. We discuss the cause of the rapid strengthening of the He I 1.0830-μm line during the early stages. V1831 Aql formed a modest amount of dust fairly early (∼19.2 d after discovery); the dust shell is not seen to be optically thick. Estimates of the dust temperature, dust mass and grain size are made. Dust formation commences around day 19.2 at a condensation temperature of 1461 ± 15 K, suggestive of a carbon composition, following which the temperature is seen to decrease gradually to 950 K. The dust mass shows a rapid initial increase, which we interpret as being due to an increase in the number of grains, followed by a period of constancy, suggesting the absence of grain destruction processes during this latter time. A discussion of the evolution of these parameters is made, including certain peculiarities seen in the grain radius evolution.

Dying star creates sculpture of gas and dust

NASA Astrophysics Data System (ADS)

2004-09-01

Sculpture of gas and dust hi-res Size hi-res: 125 Kb Credits: ESA, NASA, HEIC and The Hubble Heritage Team (STScI/AURA) Dying star creates sculpture of gas and dust The so-called Cat's Eye Nebula, formally catalogued NGC 6543 and seen here in this detailed view from the NASA/ESA Hubble Space Telescope, is one of the most complex planetary nebulae ever seen in space. A planetary nebula forms when Sun-like stars gently eject their outer gaseous layers to form bright nebulae with amazing twisted shapes. Hubble first revealed NGC 6543's surprisingly intricate structures including concentric gas shells, jets of high-speed gas and unusual shock-induced knots of gas in 1994. This new image, taken with Hubble's Advanced Camera for Surveys (ACS), reveals the full beauty of a bull's-eye pattern of eleven or more concentric rings, or shells, around the Cat’s Eye. Each ‘ring’ is actually the edge of a spherical bubble seen projected onto the sky - which is why it appears bright along its outer edge. High resolution version (JPG format) 125 Kb High resolution version (TIFF format) 2569 Kb Acknowledgment: R. Corradi (Isaac Newton Group of Telescopes, Spain) and Z. Tsvetanov (NASA). Sculpture of gas and dust hi-res Size hi-res: 287 Kb Credits: Nordic Optical Telescope and Romano Corradi (Isaac Newton Group of Telescopes, Spain) Dying star creates sculpture of gas and dust An enormous but extremely faint halo of gaseous material surrounds the Cat’s Eye Nebula and is over three light-years across. Some planetary nebulae been found to have halos like this one, likely formed of material ejected during earlier active episodes in the star's evolution - most likely some 50 000 to 90 000 years ago. This image was taken by Romano Corradi with the Nordic Optical Telescope on La Palma in the Canary Islands. The image is constructed from two narrow-band exposures showing oxygen atoms (1800 seconds, in blue) and nitrogen atoms (1800 seconds, in red). High resolution version (JPG format) 287 Kb High resolution version (TIFF format) 4674 Kb Although the rings may be the key to explaining the final ‘gasp’ of the dying central star, the mystery behind the Cat’s Eye Nebula’s nested ‘Russian doll’ structure remains largely unsolved. The so-called Cat's Eye Nebula, formally catalogued NGC 6543 and seen here in this detailed view from the NASA/ESA Hubble Space Telescope, is one of the most complex planetary nebulae ever seen in space. A planetary nebula forms when Sun-like stars gently eject their outer gaseous layers to form bright nebulae with amazing twisted shapes. Hubble first revealed NGC 6543's surprisingly intricate structures including concentric gas shells, jets of high-speed gas and unusual shock-induced knots of gas in 1994. This new image, taken with Hubble's Advanced Camera for Surveys (ACS), reveals the full beauty of a bull's-eye pattern of eleven or more concentric rings, or shells, around the Cat’s Eye. Each ‘ring’ is actually the edge of a spherical bubble seen projected onto the sky - which is why it appears bright along its outer edge. Observations suggest that the star ejected its mass in a series of pulses at 1500-year intervals. These convulsions created dust shells that each contains as much mass as all of the planets in our Solar System combined (but still only one-percent of the Sun's mass). These concentric shells make a layered onion-skin structure around the dying star. The view from Hubble is like seeing an onion cut in half, where each layer of skin is discernible. Until recently, it was thought that shells around planetary nebulae were a rare phenomenon. However, Romano Corradi (Isaac Newton Group of Telescopes, Spain) and collaborators, in a paper published in the European journal Astronomy & Astrophysics in April 2004, have instead shown that the formation of these rings is likely to be the rule rather than the exception. The bull's-eye patterns seen around planetary nebulae come as a surprise to astronomers because they had no expectation of episodes of mass loss at the end of stellar lives that repeat every 1500 years or so. Several explanations have been proposed, including cycles of magnetic activity somewhat similar to our own Sun's sunspot cycle, the action of companion stars orbiting around the dying star, and stellar pulsations. Another school of thought is that the material is ejected smoothly from the star, and the rings are created later on due to formation of waves in the outflowing material. It will take further observations and more theoretical studies to decide between these and other possible explanations. Approximately 1000 years ago the pattern of mass loss suddenly changed, and the Cat's Eye Nebula itself started forming inside the dusty shells. It has been expanding ever since, as can be seen by comparing Hubble images taken in 1994, 1997, 2000 and 2002. But what has caused this dramatic change? Many aspects of the process that leads a star to lose its gaseous envelope are poorly known, and the study of planetary nebulae is one of the few ways to recover information about the last few thousand years in the life of a Sun-like star. Notes for editors: The group of astronomers involved in the April 2004, Astronomy & Astrophysics paper are: R.L.M. Corradi (Isaac Newton Group of Telescopes, Spain), P. Sanchez-Blazquez (Universidad Complutense, Spain), G. Mellema (Foundation for Research in Astronomy, The Netherlands), C. Giammanco (Instituto de Astrofisica de Canarias, Spain) and H.E. Schwarz (Cerro Tololo Inter-American Observatory, Chile). The Hubble Space Telescope is a project of international co-operation between ESA and NASA.

The Geminga pulsar wind nebula in the mid-infrared and submillimetre

NASA Astrophysics Data System (ADS)

Greaves, J. S.; Holland, W. S.

2017-10-01

The nearby middle-aged Geminga pulsar has crossed the Galactic plane within the last ∼0.1 Myr. We present archival data from Wide-field Infrared Survey Explorer and from SCUBA and SCUBA-2 on the James Clerk Maxwell Telescope to assess whether any mid-infrared and submillimetre emission arises from interaction of the pulsar wind nebula with the interstellar medium. A candidate shell and bow shock are reported. Given the low pulsar velocity and local density, dust grains appear able to penetrate into the nebula. A compact source seen towards the pulsar is fitted with a dust spectrum. If confirmed as a real association at higher resolution, this could be a circum-pulsar disc of at least a few Earth-masses, in which future planets could form.

Stochastic parameterization for light absorption by internally mixed BC/dust in snow grains for application to climate models

NASA Astrophysics Data System (ADS)

Liou, K. N.; Takano, Y.; He, C.; Yang, P.; Leung, L. R.; Gu, Y.; Lee, W. L.

2014-06-01

A stochastic approach has been developed to model the positions of BC (black carbon)/dust internally mixed with two snow grain types: hexagonal plate/column (convex) and Koch snowflake (concave). Subsequently, light absorption and scattering analysis can be followed by means of an improved geometric-optics approach coupled with Monte Carlo photon tracing to determine BC/dust single-scattering properties. For a given shape (plate, Koch snowflake, spheroid, or sphere), the action of internal mixing absorbs substantially more light than external mixing. The snow grain shape effect on absorption is relatively small, but its effect on asymmetry factor is substantial. Due to a greater probability of intercepting photons, multiple inclusions of BC/dust exhibit a larger absorption than an equal-volume single inclusion. The spectral absorption (0.2-5 µm) for snow grains internally mixed with BC/dust is confined to wavelengths shorter than about 1.4 µm, beyond which ice absorption predominates. Based on the single-scattering properties determined from stochastic and light absorption parameterizations and using the adding/doubling method for spectral radiative transfer, we find that internal mixing reduces snow albedo substantially more than external mixing and that the snow grain shape plays a critical role in snow albedo calculations through its forward scattering strength. Also, multiple inclusion of BC/dust significantly reduces snow albedo as compared to an equal-volume single sphere. For application to land/snow models, we propose a two-layer spectral snow parameterization involving contaminated fresh snow on top of old snow for investigating and understanding the climatic impact of multiple BC/dust internal mixing associated with snow grain metamorphism, particularly over mountain/snow topography.

MULTIGRAIN: a smoothed particle hydrodynamic algorithm for multiple small dust grains and gas

NASA Astrophysics Data System (ADS)

Hutchison, Mark; Price, Daniel J.; Laibe, Guillaume

2018-05-01

We present a new algorithm, MULTIGRAIN, for modelling the dynamics of an entire population of small dust grains immersed in gas, typical of conditions that are found in molecular clouds and protoplanetary discs. The MULTIGRAIN method is more accurate than single-phase simulations because the gas experiences a backreaction from each dust phase and communicates this change to the other phases, thereby indirectly coupling the dust phases together. The MULTIGRAIN method is fast, explicit and low storage, requiring only an array of dust fractions and their derivatives defined for each resolution element.

A toy Penrose inequality and its proof

NASA Astrophysics Data System (ADS)

Bengtsson, Ingemar; Jakobsson, Emma

2016-12-01

We formulate and prove a toy version of the Penrose inequality. The formulation mimics the original Penrose inequality in which the scenario is the following: a shell of null dust collapses in Minkowski space and a marginally trapped surface forms on it. Through a series of arguments relying on established assumptions, an inequality relating the area of this surface to the total energy of the shell is formulated. Then a further reformulation turns the inequality into a statement relating the area and the outer null expansion of a class of surfaces in Minkowski space itself. The inequality has been proven to hold true in many special cases, but there is no proof in general. In the toy version here presented, an analogous inequality in (2 + 1)-dimensional anti-de Sitter space turns out to hold true.

Nonsymmetric dynamical thin-shell wormhole in Robinson-Trautman class

NASA Astrophysics Data System (ADS)

Svítek, O.; Tahamtan, T.

2018-02-01

The thin-shell wormhole created using the Darmois-Israel formalism applied to Robinson-Trautman family of spacetimes is presented. The stress energy tensor created on the throat is interpreted in terms of two dust streams and it is shown that asymptotically this wormhole settles to the Schwarzschild wormhole with a throat located at the position of the horizon. This behavior shows a nonlinear stability (within the Robinson-Trautman class) of this spherically symmetric wormhole. The gravitational radiation emitted by the Robinson-Trautman wormhole during the transition to spherical symmetry is indistinguishable from that of the corresponding black hole Robinson-Trautman spacetime. Subsequently, we show that the higher-dimensional generalization of Robinson-Trautman geometry offers a possibility of constructing wormholes without the need to violate the energy conditions for matter induced on the throat.

Design, synthesis and applications of core-shell, hollow core, and nanorattle multifunctional nanostructures.

PubMed

El-Toni, Ahmed Mohamed; Habila, Mohamed A; Labis, Joselito Puzon; ALOthman, Zeid A; Alhoshan, Mansour; Elzatahry, Ahmed A; Zhang, Fan

2016-02-07

With the evolution of nanoscience and nanotechnology, studies have been focused on manipulating nanoparticle properties through the control of their size, composition, and morphology. As nanomaterial research has progressed, the foremost focus has gradually shifted from synthesis, morphology control, and characterization of properties to the investigation of function and the utility of integrating these materials and chemical sciences with the physical, biological, and medical fields, which therefore necessitates the development of novel materials that are capable of performing multiple tasks and functions. The construction of multifunctional nanomaterials that integrate two or more functions into a single geometry has been achieved through the surface-coating technique, which created a new class of substances designated as core-shell nanoparticles. Core-shell materials have growing and expanding applications due to the multifunctionality that is achieved through the formation of multiple shells as well as the manipulation of core/shell materials. Moreover, core removal from core-shell-based structures offers excellent opportunities to construct multifunctional hollow core architectures that possess huge storage capacities, low densities, and tunable optical properties. Furthermore, the fabrication of nanomaterials that have the combined properties of a core-shell structure with that of a hollow one has resulted in the creation of a new and important class of substances, known as the rattle core-shell nanoparticles, or nanorattles. The design strategies of these new multifunctional nanostructures (core-shell, hollow core, and nanorattle) are discussed in the first part of this review. In the second part, different synthesis and fabrication approaches for multifunctional core-shell, hollow core-shell and rattle core-shell architectures are highlighted. Finally, in the last part of the article, the versatile and diverse applications of these nanoarchitectures in catalysis, energy storage, sensing, and biomedicine are presented.

THE S{sup 4}G PERSPECTIVE ON CIRCUMSTELLAR DUST EXTINCTION OF ASYMPTOTIC GIANT BRANCH STARS IN M100

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

Meidt, Sharon E.; Schinnerer, Eva; Munoz-Mateos, Juan-Carlos

2012-04-01

We examine the effect of circumstellar dust extinction on the near-IR (NIR) contribution of asymptotic giant branch (AGB) stars in intermediate-age clusters throughout the disk of M100. For our sample of 17 AGB-dominated clusters we extract optical-to-mid-IR spectral energy distributions (SEDs) and find that NIR brightness is coupled to the mid-IR dust emission in such a way that a significant reduction of AGB light, of up to 1 mag in the K band, follows from extinction by the dust shell formed during this stage. Since the dust optical depth varies with AGB chemistry (C-rich or O-rich), our results suggest thatmore » the contribution of AGB stars to the flux from their host clusters will be closely linked to the metallicity and the progenitor mass of the AGB star, to which dust chemistry and mass-loss rate are sensitive. Our sample of clusters-each the analogue of a {approx}1 Gyr old post-starburst galaxy-has implications within the context of mass and age estimation via SED modeling at high-z: we find that the average {approx}0.5 mag extinction estimated here may be sufficient to reduce the AGB contribution in the (rest-frame) K band from {approx}70%, as predicted in the latest generation of synthesis models, to {approx}35%. Our technique for selecting AGB-dominated clusters in nearby galaxies promises to be effective for discriminating the uncertainties associated with AGB stars in intermediate-age populations that plague age and mass estimation in high-z galaxies.« less

Multiple impacts of dusty projectiles

NASA Astrophysics Data System (ADS)

Kothe, Stefan; Güttler, Carsten; Blum, Jurgen

In the context of early stages of planetesimal formation we performed laboratory and drop tower experiments to study multiple impacts of small dust-aggregate projectiles into solid sintered dust targets. Both collision partners consisted of 1.5 µm monodisperse spherical SiO2 monomers with volume filling factors of 0.15 (projectiles) and 0.35 (targets), respectively. The fragile projectiles were accelerated by a solenoid accelerator with a linear projectile magazine, which enabled us to perform 25 impacts within 4.5 s of microgravity time in the Bremen drop tower. We measured the mass-accretion efficiency for different impact velocities between 3 and 5 m s-1 , using an analytical balance and imaging methods. Furthermore, we observed random collisions among small dust aggregates with sizes around 1 mm and collision velocities of the order of 0.25 m s-1 and used them to improve the dust-aggregate collision model of Güttler et al. (2010). u

Dust Plasma Environment between Saturn's Rings and Mimas' L Shell

NASA Astrophysics Data System (ADS)

Sittler, E. C., Jr.; Johnson, R. E.

2015-12-01

We will present a new analysis of the available data on the extension of Saturn's ring atmosphere into the magnetosphere beyond the A-ring outer edge (Johnson et al. 2006) out to the orbit of Mimas. This is an interesting region in Saturn's magnetosphere containing the F and G rings and penetrated by the E-ring and the Enceladus neutral torus. This analysis will include a comparison of the Cassini Plasma Spectrometer (CAPS) plasma data, Radio and Plasma Wave Spectrometer (RPWS) plasma wave observations, RPWS Langmuir Probe (LP) observations and Cassini Dust Analyzer (CDA). The central focus will be on the dust plasma interactions. Specific attention will be paid to the SOI data for which there are considerable differences between the ion and electron densities (Elrod et al., 2012) while for other close flybys inside Mimas' L shell such differences are less obvious but the electron data appear to be highly variable. Using previous identifications of nm particles (Jones et al., 2010) inferred from CAPS data and micron sized particles that can be detected by CDA (Kempf et al., 2006) and the RPWS plasma wave dust impact signatures (Kurth et al., 2006) we will attempt to infer the full particle size distribution between the A-ring and Mimas. These nm to micron sized particles can accumulate considerable charge and under certain circumstances could account for the radial trend in the ion density described in Elrod et al. (2014) a critical issue in preparation for the Cassini proximal orbits. References: Elrod, M.K., W.-L. Tseng, R.J. Wilson, R.E. Johnson, J. Geophys. Res., 117, A03207, 2012. Elrod, M.K., W-L Tseng, A.K. Woodson, R.E. Johnson, Icarus, 242, 130-137,2014. Johnson, R. E., et al., Icarus, 180, 393-402, 2006. Jones, G. H., et al., Geophys. Res. Lett., 36, L16204, 2009. Kempf, S., U. Beckmann, R. Srama, M. Horanyi, S. Auerd, E. Grun, Planet. Space Sci., 54, 999-1006, 2006. Kurth, W. S., T.F. Averkamp, D.A. Gurnett, Z. Wang, Planet. Space Sci., 54, 988-998, 2006.

Method of fabricating nested shells and resulting product

DOEpatents

Henderson, Timothy M.; Kool, Lawrence B.

1982-01-01

A multiple shell structure and a method of manufacturing such structure wherein a hollow glass microsphere is surface treated in an organosilane solution so as to render the shell outer surface hydrophobic. The surface treated glass shell is then suspended in the oil phase of an oil-aqueous phase dispersion. The oil phase includes an organic film-forming monomer, a polymerization initiator and a blowing agent. A polymeric film forms at each phase boundary of the dispersion and is then expanded in a blowing operation so as to form an outer homogeneously integral monocellular substantially spherical thermoplastic shell encapsulating an inner glass shell of lesser diameter.

Single-step generation of metal-plasma polymer multicore@shell nanoparticles from the gas phase.

PubMed

Solař, Pavel; Polonskyi, Oleksandr; Olbricht, Ansgar; Hinz, Alexander; Shelemin, Artem; Kylián, Ondřej; Choukourov, Andrei; Faupel, Franz; Biederman, Hynek

2017-08-17

Nanoparticles composed of multiple silver cores and a plasma polymer shell (multicore@shell) were prepared in a single step with a gas aggregation cluster source operating with Ar/hexamethyldisiloxane mixtures and optionally oxygen. The size distribution of the metal inclusions as well as the chemical composition and the thickness of the shells were found to be controlled by the composition of the working gas mixture. Shell matrices ranging from organosilicon plasma polymer to nearly stoichiometric SiO 2 were obtained. The method allows facile fabrication of multicore@shell nanoparticles with tailored functional properties, as demonstrated here with the optical response.

Thick-shell nanocrystal quantum dots

DOEpatents

Hollingsworth, Jennifer A [Los Alamos, NM; Chen, Yongfen [Eugene, OR; Klimov, Victor I [Los Alamos, NM; Htoon, Han [Los Alamos, NM; Vela, Javier [Los Alamos, NM

2011-05-03

Colloidal nanocrystal quantum dots comprising an inner core having an average diameter of at least 1.5 nm and an outer shell, where said outer shell comprises multiple monolayers, wherein at least 30% of the quantum dots have an on-time fraction of 0.80 or greater under continuous excitation conditions for a period of time of at least 10 minutes.

Line spring model and its applications to part-through crack problems in plates and shells

NASA Technical Reports Server (NTRS)

Erdogan, Fazil; Aksel, Bulent

1988-01-01

The line spring model is described and extended to cover the problem of interaction of multiple internal and surface cracks in plates and shells. The shape functions for various related crack geometries obtained from the plane strain solution and the results of some multiple crack problems are presented. The problems considered include coplanar surface cracks on the same or opposite sides of a plate, nonsymmetrically located coplanar internal elliptic cracks, and in a very limited way the surface and corner cracks in a plate of finite width and a surface crack in a cylindrical shell with fixed end.

Line Spring Model and Its Applications to Part-Through Crack Problems in Plates and Shells

NASA Technical Reports Server (NTRS)

Erdogan, F.; Aksel, B.

1986-01-01

The line spring model is described and extended to cover the problem of interaction of multiple internal and surface cracks in plates and shells. The shape functions for various related crack geometries obtained from the plane strain solution and the results of some multiple crack problems are presented. The problems considered include coplanar surface cracks on the same or opposite sides of a plate, nonsymmetrically located coplanar internal elliptic cracks, and in a very limited way the surface and corner cracks in a plate of finite width and a surface crack in a cylindrical shell with fixed end.

A 2 MV Van de Graaff accelerator as a tool for planetary and impact physics research

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

Mocker, Anna; Bugiel, Sebastian; Srama, Ralf

Investigating the dynamical and physical properties of cosmic dust can reveal a great deal of information about both the dust and its many sources. Over recent years, several spacecraft (e.g., Cassini, Stardust, Galileo, and Ulysses) have successfully characterised interstellar, interplanetary, and circumplanetary dust using a variety of techniques, including in situ analyses and sample return. Charge, mass, and velocity measurements of the dust are performed either directly (induced charge signals) or indirectly (mass and velocity from impact ionisation signals or crater morphology) and constrain the dynamical parameters of the dust grains. Dust compositional information may be obtained via either time-of-flightmore » mass spectrometry of the impact plasma or direct sample return. The accurate and reliable interpretation of collected spacecraft data requires a comprehensive programme of terrestrial instrument calibration. This process involves accelerating suitable solar system analogue dust particles to hypervelocity speeds in the laboratory, an activity performed at the Max Planck Institut fuer Kernphysik in Heidelberg, Germany. Here, a 2 MV Van de Graaff accelerator electrostatically accelerates charged micron and submicron-sized dust particles to speeds up to 80 km s{sup -1}. Recent advances in dust production and processing have allowed solar system analogue dust particles (silicates and other minerals) to be coated with a thin conductive shell, enabling them to be charged and accelerated. Refinements and upgrades to the beam line instrumentation and electronics now allow for the reliable selection of particles at velocities of 1-80 km s{sup -1} and with diameters of between 0.05 {mu}m and 5 {mu}m. This ability to select particles for subsequent impact studies based on their charges, masses, or velocities is provided by a particle selection unit (PSU). The PSU contains a field programmable gate array, capable of monitoring in real time the particles' speeds and charges, and is controlled remotely by a custom, platform independent, software package. The new control instrumentation and electronics, together with the wide range of accelerable particle types, allow the controlled investigation of hypervelocity impact phenomena across a hitherto unobtainable range of impact parameters.« less

A 2 MV Van de Graaff accelerator as a tool for planetary and impact physics research

NASA Astrophysics Data System (ADS)

Mocker, Anna; Bugiel, Sebastian; Auer, Siegfried; Baust, Günter; Colette, Andrew; Drake, Keith; Fiege, Katherina; Grün, Eberhard; Heckmann, Frieder; Helfert, Stefan; Hillier, Jonathan; Kempf, Sascha; Matt, Günter; Mellert, Tobias; Munsat, Tobin; Otto, Katharina; Postberg, Frank; Röser, Hans-Peter; Shu, Anthony; Sternovsky, Zoltán; Srama, Ralf

2011-09-01

Investigating the dynamical and physical properties of cosmic dust can reveal a great deal of information about both the dust and its many sources. Over recent years, several spacecraft (e.g., Cassini, Stardust, Galileo, and Ulysses) have successfully characterised interstellar, interplanetary, and circumplanetary dust using a variety of techniques, including in situ analyses and sample return. Charge, mass, and velocity measurements of the dust are performed either directly (induced charge signals) or indirectly (mass and velocity from impact ionisation signals or crater morphology) and constrain the dynamical parameters of the dust grains. Dust compositional information may be obtained via either time-of-flight mass spectrometry of the impact plasma or direct sample return. The accurate and reliable interpretation of collected spacecraft data requires a comprehensive programme of terrestrial instrument calibration. This process involves accelerating suitable solar system analogue dust particles to hypervelocity speeds in the laboratory, an activity performed at the Max Planck Institut für Kernphysik in Heidelberg, Germany. Here, a 2 MV Van de Graaff accelerator electrostatically accelerates charged micron and submicron-sized dust particles to speeds up to 80 km s-1. Recent advances in dust production and processing have allowed solar system analogue dust particles (silicates and other minerals) to be coated with a thin conductive shell, enabling them to be charged and accelerated. Refinements and upgrades to the beam line instrumentation and electronics now allow for the reliable selection of particles at velocities of 1-80 km s-1 and with diameters of between 0.05 μm and 5 μm. This ability to select particles for subsequent impact studies based on their charges, masses, or velocities is provided by a particle selection unit (PSU). The PSU contains a field programmable gate array, capable of monitoring in real time the particles' speeds and charges, and is controlled remotely by a custom, platform independent, software package. The new control instrumentation and electronics, together with the wide range of accelerable particle types, allow the controlled investigation of hypervelocity impact phenomena across a hitherto unobtainable range of impact parameters.

Demonstration of a Three-dimensional Negative Index Medium Operated at Multiple-angle Incidences by Monolithic Metallic Hemispherical Shells

NASA Astrophysics Data System (ADS)

Yeh, Ting-Tso; Huang, Tsung-Yu; Tanaka, Takuo; Yen, Ta-Jen

2017-04-01

We design and construct a three-dimensional (3D) negative index medium (NIM) composed of gold hemispherical shells to supplant an integration of a split-ring resonator and a discrete plasmonic wire for both negative permeability and permittivity at THz gap. With the proposed highly symmetric gold hemispherical shells, the negative index is preserved at multiple incident angles ranging from 0° to 85° for both TE and TM waves, which is further evidenced by negative phase flows in animated field distributions and outweighs conventional fishnet structures with operating frequency shifts when varying incident angles. Finally, the fabrication of the gold hemispherical shells is facilitated via standard UV lithographic and isotropic wet etching processes and characterized by μ-FTIR. The measurement results agree the simulated ones very well.

Light Scattering by Lunar Exospheric Dust: What could be Learned from LRO LAMP and LADEE UVS?

NASA Astrophysics Data System (ADS)

Glenar, D. A.; Stubbs, T. J.; Richard, D. T.; Stern, S. A.; Retherford, K. D.; Gladstone, R.; Feldman, P. D.; Colaprete, A.; Delory, G. T.

2011-12-01

Two complementary spectrometers, namely the Lunar Reconnaissance Orbiter, Lyman Alpha Mapping Project (LAMP) and the planned Lunar Atmosphere and Dust Environment Explorer (LADEE) Ultraviolet Explorer (UVS) will carry out sensitive searches for high altitude exospheric dust, via detection of scattered sunlight. The combined spectral coverage of these instruments extends from far-UV to near-IR wavelengths. Over this wavelength range, grain size parameter (X=2πr/λ, with r the grain radius and λ the wavelength) changes dramatically, which makes broad wavelength coverage a good diagnostic of grain size. Utilizing different pointing geometries, both LAMP and UVS are able to observe dust over a range of scattering angles, as well as measure the dust vertical profile via limb measurements at multiple tangent heights. We summarize several categories of information that can be inferred from the data sets, using broadband simulations of horizon glow as observed at the limb. Grain scattering properties used in these simulations were computed for multiple grain shapes using Discrete-Dipole theory. Some cautionary remarks are included regarding the use of Mie theory to interpret scattering measurements.

The Cold Dust Content of the Oxygen-rich Supernova Remnant G292.0+1.8

NASA Astrophysics Data System (ADS)

Ghavamian, Parviz; Williams, Brian J.

2016-11-01

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 dust 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 dust mass in the Spur, under the most conservative assumption that the ejecta dust has a temperature of 15 K. Modeling the dust 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 dust, can be fitted with a two-component dust model with a silicate component at 62 K and graphite component at 40 K for a total dust mass of 0.023 M ⊙.

Gene Expression Profiling of Lung Tissue of Rats Exposed to Lunar Dust Particles

NASA Technical Reports Server (NTRS)

Zhang, Ye; Feiveson, Alan H.; Lam, Chiu-Wing; Kidane, Yared H.; Ploutz-Snyder Robert; Yeshitla, Samrawit; Zalesak, Selina M.; Scully, Robert R.; Wu, Honglu; James, John T.

2014-01-01

The purpose of the study is to analyze the dynamics of global gene expression changes in the lung tissue of rats exposed to lunar dust particles. Multiple pathways and transcription factors were identified using the Ingenuity Pathway Analysis tool, showing the potential networks of these signaling regulations involved in lunar dust-induced prolonged proflammatory response and toxicity. The data presented in this study, for the first time, explores the molecular mechanisms of lunar dust induced toxicity. This work contributes not only to the risk assessment for future space exploration, but also to the understanding of the dust-induced toxicity to humans on earth.

THE INFRARED SPECTRAL PROPERTIES OF MAGELLANIC CARBON STARS

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

Sloan, G. C.; Kraemer, K. E.; McDonald, I.

2016-07-20

The Infrared Spectrograph on the Spitzer Space Telescope observed 184 carbon stars in the Magellanic Clouds. This sample reveals that the dust-production rate (DPR) from carbon stars generally increases with the pulsation period of the star. The composition of the dust grains follows two condensation sequences, with more SiC condensing before amorphous carbon in metal-rich stars, and the order reversed in metal-poor stars. MgS dust condenses in optically thicker dust shells, and its condensation is delayed in more metal-poor stars. Metal-poor carbon stars also tend to have stronger absorption from C{sub 2}H{sub 2} at 7.5 μ m. The relation betweenmore » DPR and pulsation period shows significant apparent scatter, which results from the initial mass of the star, with more massive stars occupying a sequence parallel to lower-mass stars, but shifted to longer periods. Accounting for differences in the mass distribution between the carbon stars observed in the Small and Large Magellanic Clouds reveals a hint of a subtle decrease in the DPR at lower metallicities, but it is not statistically significant. The most deeply embedded carbon stars have lower variability amplitudes and show SiC in absorption. In some cases they have bluer colors at shorter wavelengths, suggesting that the central star is becoming visible. These deeply embedded stars may be evolving off of the asymptotic giant branch and/or they may have non-spherical dust geometries.« less

Properties of dust and clouds in the Mars atmosphere: Analysis of Viking IRTM emission phase function sequences

NASA Technical Reports Server (NTRS)

Clancy, R. T.; Lee, S. W.

1991-01-01

An analysis of emission-phase-function (EPF) observations from the Viking Orbiter Infrared Thermal Mapper (IRTM) yields a wide variety of results regarding dust and cloud scattering in the Mars atmosphere and atmospheric-corrected albedos for the surface of Mars. A multiple scattering radiative transfer model incorporating a bidirectional phase function for the surface and atmospheric scattering by dust and clouds is used to derive surface albedos and dust and ice optical properties and optical depths for these various conditions on Mars.

Desert Dust and Health: A Central Asian Review and Steppe Case Study.

PubMed

Sternberg, Troy; Edwards, Mona

2017-11-03

In Asian deserts environmental and anthropomorphic dust is a significant health risk to rural populations. Natural sources in dry landscapes are exacerbated by human activities that increase the vulnerability to dust and dust-borne disease vectors. Today in Central and Inner Asian drylands, agriculture, mining, and rapid development contribute to dust generation and community exposure. Thorough review of limited dust investigation in the region implies but does not quantify health risks. Anthropogenic sources, such as the drying of the Aral Sea, highlight the shifting dust dynamics across the Central EurAsian steppe. In the Gobi Desert, our case study in Khanbogd, Mongolia addressed large-scale mining's potential dust risk to the health of the local population. Dust traps showed variable exposure to particulates among herder households and town residents; dust density distribution indicated that sources beyond the mine need to be considered when identifying particulate sources. Research suggests that atmospheric dust from multiple causes may enhance human particulate exposure. Greater awareness of dust in greater Central Asia reflects community concern about related health implications. Future human well-being in the region will require more thorough information on dust emissions in the changing environment.

Desert Dust and Health: A Central Asian Review and Steppe Case Study

PubMed Central

Sternberg, Troy; Edwards, Mona

2017-01-01

In Asian deserts environmental and anthropomorphic dust is a significant health risk to rural populations. Natural sources in dry landscapes are exacerbated by human activities that increase the vulnerability to dust and dust-borne disease vectors. Today in Central and Inner Asian drylands, agriculture, mining, and rapid development contribute to dust generation and community exposure. Thorough review of limited dust investigation in the region implies but does not quantify health risks. Anthropogenic sources, such as the drying of the Aral Sea, highlight the shifting dust dynamics across the Central EurAsian steppe. In the Gobi Desert, our case study in Khanbogd, Mongolia addressed large-scale mining’s potential dust risk to the health of the local population. Dust traps showed variable exposure to particulates among herder households and town residents; dust density distribution indicated that sources beyond the mine need to be considered when identifying particulate sources. Research suggests that atmospheric dust from multiple causes may enhance human particulate exposure. Greater awareness of dust in greater Central Asia reflects community concern about related health implications. Future human well-being in the region will require more thorough information on dust emissions in the changing environment. PMID:29099792

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.

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.

Peatland Microbial Communities as Indicators of the Extreme Atmospheric Dust Deposition.

PubMed

Fiałkiewicz-Kozieł, B; Smieja-Król, B; Ostrovnaya, T M; Frontasyeva, M; Siemińska, A; Lamentowicz, M

We investigated a peat profile from the Izery Mountains, located within the so-called Black Triangle, the border area of Poland, Czech Republic, and Germany. This peatland suffered from an extreme atmospheric pollution during the last 50 years, which created an exceptional natural experiment to examine the impact of pollution on peatland microbes. Testate amoebae (TA), Centropyxis aerophila and Phryganella acropodia , were distinguished as a proxy of atmospheric pollution caused by extensive brown coal combustion. We recorded a decline of mixotrophic TA and development of agglutinated taxa as a response for the extreme concentration of Al (30 g kg -1 ) and Cu (96 mg kg -1 ) as well as the extreme amount of fly ash particles determined by scanning electron microscopy (SEM) analysis, which were used by TA for shell construction. Titanium (5.9 %), aluminum (4.7 %), and chromium (4.2 %) significantly explained the highest percentage of the variance in TA data. Elements such as Al, Ti, Cr, Ni, and Cu were highly correlated ( r  > 0.7, p  < 0.01) with pseudostome position/body size ratio and pseudostome position. Changes in the community structure, functional diversity, and mechanisms of shell construction were recognized as the indicators of dust pollution. We strengthen the importance of the TA as the bioindicators of the recent atmospheric pollution.

Eta Carinae: A Demanding Mistress

NASA Technical Reports Server (NTRS)

Gull, Theodore

2012-01-01

In the 1840's a southern star, Eta Argus, brightened to rival Sirius for nearly a decade, then faded. Today, we see the Homunculus, an hourglass figure with tutu, a dusty shell exceeding 12 solar masses expanding outward at 500 km/s. Many observers have systematically studied the massive binary total shrouded by interacting winds and its ejecta. More recently 3-D wind-wind collision models have begun to explain the extended structures resolved by Hubble Space Telescope. Now Herschel Space Observatory infrared scans are revealing wind interaction emissions and complex molecules left over from the dust that formed out of gas originally overabundant in nitrogen and greatly-depleted in oxygen and carbon. Many questions remain to be answered: What is the dust that formed in the 1840s event? What are the end states of the two massive companions ... SN, GRB, Hypernova? and When

Titanium carbide and titania phases on Antarctic ice particles of probable extraterrrestrial origin

NASA Technical Reports Server (NTRS)

Zolensky, M. E.; Pun, A.; Thomas, K. L.

1989-01-01

Two unique titania-rich particles, found within ancient Antarctic ice have been discovered and characterized, and are believed to be of extraterrestrial origin. Both particles contain abundant submicron-sized crystals of Magneli phases (Ti(n)O(2n-1). In addition, one particle contains a core of TiC. Whereas the Magneli phases would have been stable in the early solar nebula, and so probably formed there, the TiC is more likely to have condensed in the cool, dusty, carbon-rich outer shell of a red giant star. It is suggested that both particles are interplanetary dust particles whose Magneli phases carry a record of the PO2-T conditions of the early solar nebula. It is further suggested that the TiC grain in particle 705 is remnant interstellar dust.

Multiwavelength Modeling of Nove Atmospheres

NASA Technical Reports Server (NTRS)

Huschildt, P. H.

2001-01-01

LMC 1988 #1 was a slow, CO type, dust forming classical nova. It was the first extragalactic nova to be observed with the IUE satellite. We have successfully fitted observed ultraviolet and optical spectra of LMC 1988 #1 taken within the first two months of its outburst (when the atmosphere was still optically thick) with synthetic spectra computed using PHOENIX nova model atmospheres. The synthetic spectra reproduce most of the features seen in the spectra and provide V band magnitudes consistent with the observed light curve. The fits are improved by increasing the CNO abundances to 10 times the solar values. The bolometric luminosity of LMC 1988 #1 was approximately constant at 2 x 10(exp 38) ergs per second at a distance of 47.3 kpc for the first 2 months of the outburst until the formation of the dust shell.

Multiple piece turbine airfoil

DOEpatents

Kimmel, Keith D; Wilson, Jr., Jack W.

2010-11-02

A turbine airfoil, such as a rotor blade or a stator vane, for a gas turbine engine, the airfoil formed as a shell and spar construction with a plurality of dog bone struts each mounted within openings formed within the shell and spar to allow for relative motion between the spar and shell in the airfoil chordwise direction while also forming a seal between adjacent cooling channels. The struts provide the seal as well as prevent bulging of the shell from the spar due to the cooling air pressure.

Bessel Fourier orientation reconstruction: an analytical EAP reconstruction using multiple shell acquisitions in diffusion MRI.

PubMed

Hosseinbor, Ameer Pasha; Chung, Moo K; Wu, Yu-Chien; Alexander, Andrew L

2011-01-01

The estimation of the ensemble average propagator (EAP) directly from q-space DWI signals is an open problem in diffusion MRI. Diffusion spectrum imaging (DSI) is one common technique to compute the EAP directly from the diffusion signal, but it is burdened by the large sampling required. Recently, several analytical EAP reconstruction schemes for multiple q-shell acquisitions have been proposed. One, in particular, is Diffusion Propagator Imaging (DPI) which is based on the Laplace's equation estimation of diffusion signal for each shell acquisition. Viewed intuitively in terms of the heat equation, the DPI solution is obtained when the heat distribution between temperatuere measurements at each shell is at steady state. We propose a generalized extension of DPI, Bessel Fourier Orientation Reconstruction (BFOR), whose solution is based on heat equation estimation of the diffusion signal for each shell acquisition. That is, the heat distribution between shell measurements is no longer at steady state. In addition to being analytical, the BFOR solution also includes an intrinsic exponential smootheing term. We illustrate the effectiveness of the proposed method by showing results on both synthetic and real MR datasets.

Global Gene Expression Profiling in Lung Tissues of Rat Exposed to Lunar Dust Particles

NASA Technical Reports Server (NTRS)

Yeshitla, Samrawit A.; Lam, Chiu-Wing; Kidane, Yared H.; Feiveson, Alan H.; Ploutz-Snyder, Robert; Wu, Honglu; James, John T.; Meyers, Valerie E.; Zhang, Ye

2014-01-01

The Moon's surface is covered by a layer of fine, potential reactive dust. Lunar dust contain about 1-2% respirable very fine dust (less than 3 micrometers). The habitable area of any lunar landing vehicle and outpost would inevitably be contaminated with lunar dust that could pose a health risk. The purpose of the study is to analyze the dynamics of global gene expression changes in lung tissues of rats exposed to lunar dust particles. F344 rats were exposed for 4 weeks (6h/d; 5d/wk) in nose-only inhalation chambers to concentrations of 0 (control air), 2.1, 6.8, 21, and 61 mg/m3 of lunar dust. Animals were euthanized at 1 day and 13 weeks after the last inhalation exposure. After being lavaged, lung tissue from each animal was collected and total RNA was isolated. Four samples of each dose group were analyzed using Agilent Rat GE v3 microarray to profile global gene expression of 44K transcripts. After background subtraction, normalization, and log transformation, t tests were used to compare the mean expression levels of each exposed group to the control group. Correction for multiple testing was made using the method of Benjamini, Krieger, and Yekuteli (1) to control the false discovery rate. Genes with significant changes of at least 1.75 fold were identified as genes of interest. Both low and high doses of lunar dust caused dramatic, dose-dependent global gene expression changes in the lung tissues. However, the responses of lung tissue to low dose lunar dust are distinguished from those of high doses, especially those associated with 61mg/m3 dust exposure. The data were further integrated into the Ingenuity system to analyze the gene ontology (GO), pathway distribution and putative upstream regulators and gene targets. Multiple pathways, functions, and upstream regulators have been identified in response to lunar dust induced damage in the lung tissue.

Multiple origins for the DLA at zabs = 0.313 toward PKS 1127-145 indicated by a complex dust depletion pattern of Ca, Ti, and Mn

NASA Astrophysics Data System (ADS)

Guber, C. R.; Richter, P.; Wendt, M.

2018-01-01

Aims: We aim to investigate the dust depletion properties of optically thick gas in and around galaxies and its origin we study in detail the dust depletion patterns of Ti, Mn, and Ca in the multi-component 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 dust 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 components (component 3) shows a striking underabundance of Ti and Mn in the gas-phase, indicating the effect of dust depletion for these elements and a locally enhanced dust-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 dust depletion effects. Conclusions: Our analysis indicates that the DLA toward PKS 1127-145 has multiple origins. With its narrow line width and its strong dust depletion, component 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 dust-poor, absorption components 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 dust-rich and dust-poor in neutral gas in and around galaxies.

Magnetism and Mössbauer study of formation of multi-core γ -Fe2O3 nanoparticles

NASA Astrophysics Data System (ADS)

Kamali, Saeed; Bringas, Eugenio; Hah, Hien-Yoong; Bates, Brian; Johnson, Jacqueline A.; Johnson, Charles E.; Stroeve, Pieter

2018-04-01

A systematic investigation of magnetic nanoparticles and the formation of a core-shell structure, consisting of multiple maghemite (γ -Fe2O3) nanoparticles as the core and silica as the shell, has been performed using various techniques. High-resolution transmission electron microscopy clearly shows isolated maghemite nanoparticles with an average diameter of 13 nm and the formation of a core-shell structure. Low temperature Mössbauer spectroscopy reveals the presence of pure maghemite nanoparticles with all vacancies at the B-sites. Isothermal magnetization and zero-field-cooled and field-cooled measurements are used for investigating the magnetic properties of the nanoparticles. The magnetization results are in good accordance with the contents of the magnetic core and the non-magnetic shell. The multiple-core γ -Fe2O3 nanoparticles show similar behavior to isolated particles of the same size.

Space science applications for conducting polymer particles: synthetic mimics for cosmic dust and micrometeorites.

PubMed

Fielding, Lee A; Hillier, Jon K; Burchell, Mark J; Armes, Steven P

2015-12-11

Over the last decade or so, a range of polypyrrole-based particles have been designed and evaluated for space science applications. This electrically conductive polymer enables such particles to efficiently acquire surface charge, which in turn allows their acceleration up to the hypervelocity regime (>1 km s(-1)) using a Van de Graaff accelerator. Either organic latex (e.g. polystyrene or poly(methyl methacrylate)) or various inorganic materials (such as silica, olivine or pyrrhotite) can be coated with polypyrrole; these core-shell particles are useful mimics for understanding the hypervelocity impact ionisation behaviour of micro-meteorites (a.k.a. cosmic dust). Impacts on metal targets at relatively low hypervelocities (<10 km s(-1)) generate ionic plasma composed mainly of molecular fragments, whereas higher hypervelocities (>10 km s(-1)) generate predominately atomic species, since many more chemical bonds are cleaved if the particles impinge with higher kinetic energy. Such fundamental studies are relevant to the calibration of the cosmic dust analyser (CDA) onboard the Cassini spacecraft, which was designed to determine the chemical composition of Saturn's dust rings. Inspired by volcanism observed for one of the Jupiter's moons (Io), polypyrrole-coated sulfur-rich latexes have also been designed to help space scientists understand ionisation spectra originating from sulfur-rich dust particles. Finally, relatively large (20 μm diameter) polypyrrole-coated polystyrene latexes have proven to be useful for understanding the extent of thermal ablation of organic projectiles when fired at ultralow density aerogel targets at up to 6.1 km s(-1) using a Light Gas Gun. In this case, the sacrificial polypyrrole overlayer simply provides a sensitive spectroscopic signature (rather than a conductive overlayer), and the scientific findings have important implications for the detection of organic dust grains during the Stardust space mission.

The Dust Management Project: Characterizing Lunar Environments and Dust, Developing Regolith Mitigation Technology and Simulants

NASA Technical Reports Server (NTRS)

Hyatt, Mark J.; Straka, Sharon A.

2010-01-01

A return to the Moon to extend human presence, pursue scientific activities, use the Moon to prepare for future human missions to Mars, and expand Earth?s economic sphere, will require investment in developing new technologies and capabilities to achieve affordable and sustainable human exploration. From the operational experience gained and lessons learned during the Apollo missions, conducting long-term operations in the lunar environment will be a particular challenge, given the difficulties presented by the unique physical properties and other characteristics of lunar regolith, including dust. The Apollo missions and other lunar explorations have identified significant lunar dust-related problems that will challenge future mission success. Comprised of regolith particles ranging in size from tens of nanometers to microns, lunar dust is a manifestation of the complex interaction of the lunar soil with multiple mechanical, electrical, and gravitational effects. The environmental and anthropogenic factors effecting the perturbation, transport, and deposition of lunar dust must be studied in order to mitigate it?s potentially harmful effects on exploration systems and human explorers. The Dust Management Project (DMP) is tasked with the evaluation of lunar dust effects, assessment of the resulting risks, and development of mitigation and management strategies and technologies related to Exploration Systems architectures. To this end, the DMP supports the overall goal of the Exploration Technology Development Program (ETDP) of addressing the relevant high priority technology needs of multiple elements within the Constellation Program (CxP) and sister ETDP projects. Project scope, plans, and accomplishments will be presented.

Constant Chinese Loess Plateau dust source since the Late Miocene

NASA Astrophysics Data System (ADS)

Bird, Anna; Millar, Ian; Stevens, Thomas; Rodenburg, Tanja; Rittner, Martin; Vermeesch, Pieter; Lu, Huayu

2017-04-01

The dramatic deepening of northern hemisphere glaciation at the Pliocene-Pleistocene boundary is accompanied by major changes in global climate. The role of the global atmospheric dust cycle in this event is not clear; in particular, whether, changes in the dust cycle influenced climates change, or resulted from it. Miocene and Quaternary wind-blown Chinese loess records past dust-cycle history, influences of aridification and monsoon circulation. Previous work on the vast Chinese Loess Plateau is in conflict over whether changes in dust source occur at the Pliocene-Pleistocene boundary (2.59 Ma), or at 1.2 Ma, despite these intervals marking major shifts in monsoon dynamics (Sun 2005; Nie et al. 2014a). Here we present Sr, Nd and Hf isotopic data from multiple sites and show that the dust source remains the same across these boundaries. The use of isotope tracers from multiple sites allows us to demonstrate that shifts in sediment geochemistry can be explained by grain-size and weathering changes. Nd and Hf isotopes show that the dust was dominantly sourced from the Tibetan Plateau, with some input from bedrock underlying the Badain Jaran/Tengger deserts. This shows that a major established and constant dust source on the northern Tibetan Plateau has been active and unchanged since the late Miocene, despite dramatically changing climate conditions. Changes in loess accumulation are therefore a function of climate change in the Tibetan Plateau source regions rather than due to expanding source areas controlled by aridification over a widening area over the Pliocene and Quaternary.

Do freshwater mussel shells record road-salt pollution?

NASA Astrophysics Data System (ADS)

O'Neil, Dane D.; Gillikin, David P.

2014-11-01

Road-salt pollution in streams in the Northeastern United States has become a major concern, but historical data are scarce. Freshwater bivalve shells have the ability to record past environmental information, and may act as archives of road-salt pollution. We sampled Elliptio complanata shells from four streams, as well as specimens collected in 1877. Average [Na/Ca]shell was highest in modern shells from the stream with the highest sodium concentrations, and low in shells collected from this same stream in 1877 as well as in the shells from other streams, suggesting that [Na/Ca]shell serves as a proxy for road-salt pollution. We expected higher [Na/Ca]shell in winter and spring. However, high-resolution [Na/Ca]shell analyses along the growth axis of one shell did not reveal any clear subannual patterns, which could be the result of shell growth cessation in winter and/or during periods of high stream sodium concentrations. Therefore, bulk [Na/Ca]shell analysis from multiple shells can be used as a proxy of large changes in stream sodium concentrations, but high-resolution variations in stream sodium concentrations do not seem to be recorded in the shells.

Do freshwater mussel shells record road-salt pollution?

PubMed Central

O'Neil, Dane D.; Gillikin, David P.

2014-01-01

Road-salt pollution in streams in the Northeastern United States has become a major concern, but historical data are scarce. Freshwater bivalve shells have the ability to record past environmental information, and may act as archives of road-salt pollution. We sampled Elliptio complanata shells from four streams, as well as specimens collected in 1877. Average [Na/Ca]shell was highest in modern shells from the stream with the highest sodium concentrations, and low in shells collected from this same stream in 1877 as well as in the shells from other streams, suggesting that [Na/Ca]shell serves as a proxy for road-salt pollution. We expected higher [Na/Ca]shell in winter and spring. However, high-resolution [Na/Ca]shell analyses along the growth axis of one shell did not reveal any clear subannual patterns, which could be the result of shell growth cessation in winter and/or during periods of high stream sodium concentrations. Therefore, bulk [Na/Ca]shell analysis from multiple shells can be used as a proxy of large changes in stream sodium concentrations, but high-resolution variations in stream sodium concentrations do not seem to be recorded in the shells. PMID:25418687

Search for the Exotic Wobbling Mode in Rhenium-171

DTIC Science & Technology

2011-05-13

USB hard drive. The decay sequences mentioned above release all of their γ rays within a nanosecond (ns). Data will be recorded when multiple ...events in which multiple detectors measured γ rays within a 120 ns window. An event in which three detectors fired within the coincidence window is...spherical nuclei; however, if the nucleus is axially deformed (non-spherical), the shell model cannot accurately describe its features . The shell model

Stochastic Parameterization for Light Absorption by Internally Mixed BC/dust in Snow Grains for Application to Climate Models

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

Liou, K. N.; Takano, Y.; He, Cenlin

2014-06-27

A stochastic approach to model the positions of BC/dust internally mixed with two snow-grain types has been developed, including hexagonal plate/column (convex) and Koch snowflake (concave). Subsequently, light absorption and scattering analysis can be followed by means of an improved geometric-optics approach coupled with Monte Carlo photon tracing to determine their single-scattering properties. For a given shape (plate, Koch snowflake, spheroid, or sphere), internal mixing absorbs more light than external mixing. The snow-grain shape effect on absorption is relatively small, but its effect on the asymmetry factor is substantial. Due to a greater probability of intercepting photons, multiple inclusions ofmore » BC/dust exhibit a larger absorption than an equal-volume single inclusion. The spectral absorption (0.2 – 5 um) for snow grains internally mixed with BC/dust is confined to wavelengths shorter than about 1.4 um, beyond which ice absorption predominates. Based on the single-scattering properties determined from stochastic and light absorption parameterizations and using the adding/doubling method for spectral radiative transfer, we find that internal mixing reduces snow albedo more than external mixing and that the snow-grain shape plays a critical role in snow albedo calculations through the asymmetry factor. Also, snow albedo reduces more in the case of multiple inclusion of BC/dust compared to that of an equal-volume single sphere. For application to land/snow models, we propose a two-layer spectral snow parameterization containing contaminated fresh snow on top of old snow for investigating and understanding the climatic impact of multiple BC/dust internal mixing associated with snow grain metamorphism, particularly over mountains/snow topography.« less

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 2 years post-explosion.

A possible mechanism to detect super-earth formation in protoplanetary disks

NASA Astrophysics Data System (ADS)

Dong, Ruobing; Chiang, Eugene; Li, Hui; Li, Shengtai

2017-06-01

Using combined gas+dust global hydrodynamics and radiative transfer simulations, we calculate the distribution of gas and sub-mm-sized dust in protoplanetary disks with a super-Earth at tens of AU, and examine observational signatures of such systems in resolved observations. We confirm previous results that in a typical disk with a low viscosity ($\\alpha\\lesssim10^{-4}$), a super-Earth is able to open two gaps at $\\sim$scale-height away around its orbit in $\\sim$mm-sized dust (St$\\sim$0.01), due to differential dust drift in a perturbed gas background. Additional rings and gaps may also be produced under certain conditions. These features, particularly a signature ``double-gap'' feature, can be detected in a Taurus target by ALMA in dust continuum under an angular resolution of $\\sim0\\arcsec.025$ with two hours of integration. The features are robust --- it can survive in a variety of background disk profiles, withstand modest planetary radial migration ($|r/\\dot{r}|\\sim$ a few Myr), and last for thousands of orbits. Multiple ring/gap systems observed by ALMA were typically modeled using multiple (Saturn-to-Jupiter sized) planets. Here, we argue that a single super-Earth in a low viscosity disk could produce multiple rings and gaps as well. By examining the prevalence of such features in nearby disks, upcoming high angular resolution ALMA surveys may infer how common super-Earth formation events are at tens of au.

Residential Culturable Fungi, (1–3, 1–6)-β-D-glucan, and Ergosterol Concentrations in Dust Are Not Associated with Asthma, Rhinitis or Eczema Diagnoses in Children

PubMed Central

Choi, Hyunok; Byrne, Sam; Larsen, Lisbeth Suldrup; Sigsgaard, Torben; Thorne, Peter S.; Larsson, Lennart; Sebastian, Aleksandra; Bornehag, Carl-Gustaf

2014-01-01

Background Qualitative reporting of home indoor moisture problems predicts respiratory diseases. However, causal agents underlying such qualitative markers remain unknown. Methods In the homes of 198 multiple allergic case children and 202 controls in Sweden, we cultivated culturable fungi by directly plating dust, and quantified(1–3, 1–6)-β-D-glucan, and ergosterol in dust samples from the child’s bedroom. We examined the relationship between these fungal agents and degree of parent or inspector reported home indoor dampness, and microbiological laboratory’s mold index. We also compared the concentrations of these agents between multiple allergic cases and healthy controls, as well as IgE-sensitization among cases. Results The concentrations of culturable fungal agents were comparable between houses with parent and inspector reported mold issues and those without. There were no differences in concentrations of the individual or the total summed culturable fungi, (1–3, 1–6)-β-D-glucan, and ergosterol between the controls and the multiple allergic case children, or individual diagnosis of asthma, rhinitis or eczema. Conclusion Culturable fungi, (1–3, 1–6)-β-D-glucan, and ergosterol in dust were not associated with qualitative markers of indoor dampness or mold or indoor humidity. Furthermore, these agents in dust samples were not associated with any health outcomes in the children. PMID:24016225

Emission Characteristics of InGaN/GaN Core-Shell Nanorods Embedded in a 3D Light-Emitting Diode.

PubMed

Jung, Byung Oh; Bae, Si-Young; Lee, Seunga; Kim, Sang Yun; Lee, Jeong Yong; Honda, Yoshio; Amano, Hiroshi

2016-12-01

We report the selective-area growth of a gallium nitride (GaN)-nanorod-based InGaN/GaN multiple-quantum-well (MQW) core-shell structure embedded in a three-dimensional (3D) light-emitting diode (LED) grown by metalorganic chemical vapor deposition (MOCVD) and its optical analysis. High-resolution transmission electron microscopy (HR-TEM) observation revealed the high quality of the GaN nanorods and the position dependence of the structural properties of the InGaN/GaN MQWs on multiple facets. The excitation and temperature dependences of photoluminescence (PL) revealed the m-plane emission behaviors of the InGaN/GaN core-shell nanorods. The electroluminescence (EL) of the InGaN/GaN core-shell-nanorod-embedded 3D LED changed color from green to blue with increasing injection current. This phenomenon was mainly due to the energy gradient and deep localization of the indium in the selectively grown InGaN/GaN core-shell MQWs on the 3D architecture.

Multiple outer-shell ionization effect in inner-shell x-ray production by light ions

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

Lapicki, G.; Mehta, R.; Duggan, J.L.

1986-11-01

L-shell x-ray production cross sections by 0.25--2.5-MeV /sub 2//sup 4/He/sup +/ ions in /sub 28/Ni, /sub 29/Cu, /sub 32/Ge, /sub 33/As, /sub 37/Rb, /sub 38/Sr, /sub 39/Y, /sub 40/Zr, and /sub 46/Pd are reported. The data are compared to the first Born approximation and the ECPSSR theory that accounts for the projectile energy loss (E) and Coulomb deflection (C) as well as the perturbed-stationary-state (PSS) and relativistic (R) effects in the treatment of the target L-shell electron. Surprisingly, the first Born approximation appears to converge to the data while the ECPSSR predictions underestimate them in the low-velocity limit. This ismore » explained as the result of improper use of single-hole fluorescence yields. A heuristic formula is proposed to account for multiple ionizations in terms of a classical probability for these phenomena and, after it is applied, the ECPSSR theory of L-shell ionization is found to be in good agreement with the data.« less

Mars dust storms - Interannual variability and chaos

NASA Technical Reports Server (NTRS)

Ingersoll, Andrew P.; Lyons, James R.

1993-01-01

The hypothesis is that the global climate system, consisting of atmospheric dust interacting with the circulation, produces its own interannual variability when forced at the annual frequency. The model has two time-dependent variables representing the amount of atmospheric dust in the northern and southern hemispheres, respectively. Absorption of sunlight by the dust drives a cross-equatorial Hadley cell that brings more dust into the heated hemisphere. The circulation decays when the dust storm covers the globe. Interannual variability manifests itself either as a periodic solution in which the period is a multiple of the Martian year, or as an aperiodic (chaotic) solution that never repeats. Both kinds of solution are found in the model, lending support to the idea that interannual variability is an intrinsic property of the global climate system. The next step is to develop a hierarchy of dust-circulation models capable of being integrated for many years.

Atmospheric bioaerosols transported via dust storms in the western United States

NASA Astrophysics Data System (ADS)

Hallar, A. Gannet; Chirokova, Galina; McCubbin, Ian; Painter, Thomas H.; Wiedinmyer, Christine; Dodson, Craig

2011-09-01

Measurements are presented showing the presence of biological material within frequent dust storms in the western United States. Previous work has indicated that biological particles were enhancing the impact of dust storms on the formation of clouds. This paper presents multiple case studies, between April and May 2010, showing the presence of and quantifying the amount of biological material via an Ultraviolet Aerodynamic Particle Sizer during dust events. All dust storms originated in the Four Corners region in the western Untied States and were measured at Storm Peak Laboratory, a high elevation facility in northwestern Colorado. From an Aerodynamic Particle Sizer, the mean dust particle size during these events was approximately 1 μm, with number concentrations between 6 cm-3 and 12 cm-3. Approximately 0.2% of these dust particles had fluorescence signatures, indicating the presence of biological material.

The Kinematics of Multiple-peaked Lyα Emission in Star-forming Galaxies at z ~ 2-3

NASA Astrophysics Data System (ADS)

Kulas, Kristin R.; Shapley, Alice E.; Kollmeier, Juna A.; Zheng, Zheng; Steidel, Charles C.; Hainline, Kevin N.

2012-01-01

We present new results on the Lyα emission-line kinematics of 18 z ~ 2-3 star-forming galaxies with multiple-peaked Lyα profiles. With our large spectroscopic database of UV-selected star-forming galaxies at these redshifts, we have determined that ~30% of such objects with detectable Lyα emission display multiple-peaked emission profiles. These profiles provide additional constraints on the escape of Lyα photons due to the rich velocity structure in the emergent line. Despite recent advances in modeling the escape of Lyα from star-forming galaxies at high redshifts, comparisons between models and data are often missing crucial observational information. Using Keck II NIRSPEC spectra of Hα (z ~ 2) and [O III]λ5007 (z ~ 3), we have measured accurate systemic redshifts, rest-frame optical nebular velocity dispersions, and emission-line fluxes for the objects in the sample. In addition, rest-frame UV luminosities and colors provide estimates of star formation rates and the degree of dust extinction. In concert with the profile sub-structure, these measurements provide critical constraints on the geometry and kinematics of interstellar gas in high-redshift galaxies. Accurate systemic redshifts allow us to translate the multiple-peaked Lyα profiles into velocity space, revealing that the majority (11/18) display double-peaked emission straddling the velocity-field zero point with stronger red-side emission. Interstellar absorption-line kinematics suggest the presence of large-scale outflows for the majority of objects in our sample, with an average measured interstellar absorption velocity offset of langΔv absrang = -230 km s-1. A comparison of the interstellar absorption kinematics for objects with multiple- and single-peaked Lyα profiles indicate that the multiple-peaked objects are characterized by significantly narrower absorption line widths. We compare our data with the predictions of simple models for outflowing and infalling gas distributions around high-redshift galaxies. While popular "shell" models provide a qualitative match with many of the observations of Lyα emission, we find that in detail there are important discrepancies between the models and data, as well as problems with applying the framework of an expanding thin shell of gas to explain high-redshift galaxy spectra. Our data highlight these inconsistencies, as well as illuminating critical elements for success in future models of outflow and infall in high-redshift galaxies. Based, in part, on data obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA, and was made possible by the generous financial support of the W. M. Keck Foundation.

The Dust Management Project: Final Report

NASA Technical Reports Server (NTRS)

Hyatt, Mark J.; Straka, Sharon

2011-01-01

A return to the Moon to extend human presence, pursue scientific activities, use the Moon to prepare for future human missions to Mars, and expand Earth s economic sphere, will require investment in developing new technologies and capabilities to achieve affordable and sustainable human exploration. From the operational experience gained and lessons learned during the Apollo missions, conducting longterm operations in the lunar environment will be a particular challenge, given the difficulties presented by the unique physical properties and other characteristics of lunar regolith, including dust. The Apollo missions and other lunar explorations have identified significant lunar dust-related problems that will challenge future mission success. Comprised of regolith particles ranging in size from tens of nanometers to microns, lunar dust is a manifestation of the complex interaction of the lunar soil with multiple mechanical, electrical, and gravitational effects. The environmental and anthropogenic factors effecting the perturbation, transport, and deposition of lunar dust must be studied in order to mitigate it s potentially harmful effects on exploration systems and human explorers. The Dust Management Project (DMP) is tasked with the evaluation of lunar dust effects, assessment of the resulting risks, and development of mitigation and management strategies and technologies related to Exploration Systems architectures. To this end, the DMP supports the overall goal of the Exploration Technology Development Program (ETDP) of addressing the relevant high priority technology needs of multiple elements within the Constellation Program (CxP) and sister ETDP projects. Project scope, approach, accomplishments, summary of deliverables, and lessons learned are presented.

The VLTI/MIDI view on the inner mass loss of evolved stars from the Herschel MESS sample

NASA Astrophysics Data System (ADS)

Paladini, C.; Klotz, D.; Sacuto, S.; Lagadec, E.; Wittkowski, M.; Richichi, A.; Hron, J.; Jorissen, A.; Groenewegen, M. A. T.; Kerschbaum, F.; Verhoelst, T.; Rau, G.; Olofsson, H.; Zhao-Geisler, R.; Matter, A.

2017-04-01

Context. The mass-loss process from evolved stars is a key ingredient for our understanding of many fields of astrophysics, including stellar evolution and the chemical enrichment of the interstellar medium (ISM) via stellar yields. Nevertheless, many questions are still unsolved, one of which is the geometry of the mass-loss process. Aims: Taking advantage of the results from the Herschel Mass loss of Evolved StarS (MESS) programme, we initiated a coordinated effort to characterise the geometry of mass loss from evolved red giants at various spatial scales. Methods: For this purpose we used the MID-infrared interferometric Instrument (MIDI) to resolve the inner envelope of 14 asymptotic giant branch stars (AGBs) in the MESS sample. In this contribution we present an overview of the interferometric data collected within the frame of our Large Programme, and we also add archive data for completeness. We studied the geometry of the inner atmosphere by comparing the observations with predictions from different geometric models. Results: Asymmetries are detected for the following five stars: R Leo, RT Vir, π1Gruis, omi Ori, and R Crt. All the objects are O-rich or S-type, suggesting that asymmetries in the N band are more common among stars with such chemistry. We speculate that this fact is related to the characteristics of the dust grains. Except for one star, no interferometric variability is detected, I.e. the changes in size of the shells of non-mira stars correspond to changes of the visibility of less than 10%. The observed spectral variability confirms previous findings from the literature. The detection of dust in our sample follows the location of the AGBs in the IRAS colour-colour diagram: more dust is detected around oxygen-rich stars in region II and in the carbon stars in region VII. The SiC dust feature does not appear in the visibility spectrum of the U Ant and S Sct, which are two carbon stars with detached shells. This finding has implications for the theory of SiC dust formation. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programmes 073.D-0711, 076.D-0620, 077.D-0294, 078.D-0122, 080.D-0801, 081.D-0021, 083.D-0234, 086.D-0737, 086.D-899, 187.D-0924, 089.D-0562, 090.D-410, 091.C-0468, 091.D-0344.

Multiple lead seal assembly for a liquid-metal-cooled fast-breeder nuclear reactor

DOEpatents

Hutter, Ernest; Pardini, John A.

1977-03-15

A reusable multiple lead seal assembly provides leak-free passage of stainless-steel-clad instrument leads through the cover on the primary tank of a liquid-metal-cooled fast-breeder nuclear reactor. The seal isolates radioactive argon cover gas and sodium vapor within the primary tank from the exterior atmosphere and permits reuse of the assembly and the stainless-steel-clad instrument leads. Leads are placed in flutes in a seal body, and a seal shell is then placed around the seal body. Circumferential channels in the body and inner surface of the shell are contiguous and together form a conduit which intersects each of the flutes, placing them in communication with a port through the wall of the seal shell. Liquid silicone rubber sealant is injected into the flutes through the port and conduit; the sealant fills the space in the flutes not occupied by the leads themselves and dries to a rubbery hardness. A nut, threaded onto a portion of the seal body not covered by the seal shell, jacks the body out of the shell and shears the sealant without damage to the body, shell, or leads. The leads may then be removed from the body. The sheared sealant is cleaned from the body, leads, and shell and the assembly may then be reused with the same or different leads.

Sparse and optimal acquisition design for diffusion MRI and beyond

PubMed Central

Koay, Cheng Guan; Özarslan, Evren; Johnson, Kevin M.; Meyerand, M. Elizabeth

2012-01-01

Purpose: Diffusion magnetic resonance imaging (MRI) in combination with functional MRI promises a whole new vista for scientists to investigate noninvasively the structural and functional connectivity of the human brain—the human connectome, which had heretofore been out of reach. As with other imaging modalities, diffusion MRI data are inherently noisy and its acquisition time-consuming. Further, a faithful representation of the human connectome that can serve as a predictive model requires a robust and accurate data-analytic pipeline. The focus of this paper is on one of the key segments of this pipeline—in particular, the development of a sparse and optimal acquisition (SOA) design for diffusion MRI multiple-shell acquisition and beyond. Methods: The authors propose a novel optimality criterion for sparse multiple-shell acquisition and quasimultiple-shell designs in diffusion MRI and a novel and effective semistochastic and moderately greedy combinatorial search strategy with simulated annealing to locate the optimum design or configuration. The goal of the optimality criteria is threefold: first, to maximize uniformity of the diffusion measurements in each shell, which is equivalent to maximal incoherence in angular measurements; second, to maximize coverage of the diffusion measurements around each radial line to achieve maximal incoherence in radial measurements for multiple-shell acquisition; and finally, to ensure maximum uniformity of diffusion measurement directions in the limiting case when all the shells are coincidental as in the case of a single-shell acquisition. The approach taken in evaluating the stability of various acquisition designs is based on the condition number and the A-optimal measure of the design matrix. Results: Even though the number of distinct configurations for a given set of diffusion gradient directions is very large in general—e.g., in the order of 10232 for a set of 144 diffusion gradient directions, the proposed search strategy was found to be effective in finding the optimum configuration. It was found that the square design is the most robust (i.e., with stable condition numbers and A-optimal measures under varying experimental conditions) among many other possible designs of the same sample size. Under the same performance evaluation, the square design was found to be more robust than the widely used sampling schemes similar to that of 3D radial MRI and of diffusion spectrum imaging (DSI). Conclusions: A novel optimality criterion for sparse multiple-shell acquisition and quasimultiple-shell designs in diffusion MRI and an effective search strategy for finding the best configuration have been developed. The results are very promising, interesting, and practical for diffusion MRI acquisitions. PMID:22559620

The effects of environment on Arctica islandica shell formation and architecture

NASA Astrophysics Data System (ADS)

Milano, Stefania; Nehrke, Gernot; Wanamaker, Alan D., Jr.; Ballesta-Artero, Irene; Brey, Thomas; Schöne, Bernd R.

2017-03-01

Mollusks record valuable information in their hard parts that reflect ambient environmental conditions. For this reason, shells can serve as excellent archives to reconstruct past climate and environmental variability. However, animal physiology and biomineralization, which are often poorly understood, can make the decoding of environmental signals a challenging task. Many of the routinely used shell-based proxies are sensitive to multiple different environmental and physiological variables. Therefore, the identification and interpretation of individual environmental signals (e.g., water temperature) often is particularly difficult. Additional proxies not influenced by multiple environmental variables or animal physiology would be a great asset in the field of paleoclimatology. The aim of this study is to investigate the potential use of structural properties of Arctica islandica shells as an environmental proxy. A total of 11 specimens were analyzed to study if changes of the microstructural organization of this marine bivalve are related to environmental conditions. In order to limit the interference of multiple parameters, the samples were cultured under controlled conditions. Three specimens presented here were grown at two different water temperatures (10 and 15 °C) for multiple weeks and exposed only to ambient food conditions. An additional eight specimens were reared under three different dietary regimes. Shell material was analyzed with two techniques; (1) confocal Raman microscopy (CRM) was used to quantify changes of the orientation of microstructural units and pigment distribution, and (2) scanning electron microscopy (SEM) was used to detect changes in microstructural organization. Our results indicate that A. islandica microstructure is not sensitive to changes in the food source and, likely, shell pigment are not altered by diet. However, seawater temperature had a statistically significant effect on the orientation of the biomineral. Although additional work is required, the results presented here suggest that the crystallographic orientation of biomineral units of A. islandica may serve as an alternative and independent proxy for seawater temperature.

Physical properties of gas disks around shell stars with and without dust

NASA Technical Reports Server (NTRS)

Grady, Carol A.

1992-01-01

Analysis of archival IRAS and IUE data has resulted in: (1) identification of 8 new A star proto-planetary candidates; (2) detection of a mass outflow event around Beta Pic (subsequently confirmed by the 1991 July HST observation); and (3) confirmation of the suggestion by Waters et al. (1988) that 51 Oph is a protoplanetary system similar to beta Pic with the detection of high density, high velocity, collisionally ionized accreting gas in the line of sight toward this star.

Far-infrared data for symbiotic stars. I - The IRAS pointed observations

NASA Technical Reports Server (NTRS)

Kenyon, Scott J.; Fernandez-Castro, Telmo; Stencel, Robert E.

1986-01-01

In the present IRAS-pointed observations of eight symbiotic stars, five S-type ones have IR energy distributions that are similar to those of normal M giants, and free-free emission may furnish a fraction of the observed 12- and 25-micron flux in three of them. Three D-type symbiotics have IR energy distributions consistent with those of Mira variables only if the giants are heavily reddened. The binaries' hot components appear to lie outside the dust shell enshrouding the Mira companions.

Beyond single-stream with the Schrödinger method

NASA Astrophysics Data System (ADS)

Uhlemann, Cora; Kopp, Michael

2016-10-01

We investigate large scale structure formation of collisionless dark matter in the phase space description based on the Vlasov-Poisson equation. We present the Schrödinger method, originally proposed by \\cite{WK93} as numerical technique based on the Schrödinger Poisson equation, as an analytical tool which is superior to the common standard pressureless fluid model. Whereas the dust model fails and develops singularities at shell crossing the Schrödinger method encompasses multi-streaming and even virialization.

High angular resolution observations of the cool giant V Hya

NASA Astrophysics Data System (ADS)

Pedretti, E.; Monnier, J. D.; Millan Gabet, R.; Traub, W. A.; Tuthill, P.; Danchi, W.; Berger, J.; Schloerb, F. P.; Thureau, N. D.; Carleton, N. P.; Lacasse, M. G.; Schuller, P. A.; Ragland, S.; Brewer, M.

2005-12-01

We present the preliminary interferometric observations of the cool giant star V Hya. V Hya, which is known to have mass-loss and to be surrounded by a dust shell,was observed in three narrow-band filters in the H bandpass at the infrared optical telescope array (IOTA), using the IONIC three-telescope beam combiner. The star was also observed at the Keck telescope using an aperture mask. We discuss the results and try to fit simple models to the observed data.

THREE-DIMENSIONAL MODELING OF THE DYNAMICS OF THERAPEUTIC ULTRASOUND CONTRAST AGENTS

PubMed Central

Hsiao, Chao-Tsung; Lu, Xiaozhen; Chahine, Georges

2010-01-01

A 3-D thick-shell contrast agent dynamics model was developed by coupling a finite volume Navier-Stokes solver and a potential boundary element method flow solver to simulate the dynamics of thick-shelled contrast agents subjected to pressure waves. The 3-D model was validated using a spherical thick-shell model validated by experimental observations. We then used this model to study shell break-up during nonspherical deformations resulting from multiple contrast agent interaction or the presence of a nearby solid wall. Our simulations indicate that the thick viscous shell resists the contrast agent from forming a re-entrant jet, as normally observed for an air bubble oscillating near a solid wall. Instead, the shell thickness varies significantly from location to location during the dynamics, and this could lead to shell break-up caused by local shell thinning and stretching. PMID:20950929

An observationally constrained estimate of global dust aerosol optical depth

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

Ridley, David A.; Heald, Colette L.; Kok, Jasper F.

Here, the role of mineral dust in climate and ecosystems has been largely quantified using global climate and chemistry model simulations of dust emission, transport, and deposition. However, differences between these model simulations are substantial, with estimates of global dust aerosol optical depth (AOD) that vary by over a factor of 5. Here we develop an observationally based estimate of the global dust AOD, using multiple satellite platforms, in situ AOD observations and four state-of-the-science global models over 2004–2008. We estimate that the global dust AOD at 550 nm is 0.030 ± 0.005 (1σ), higher than the AeroCom model medianmore » (0.023) and substantially narrowing the uncertainty. The methodology used provides regional, seasonal dust AOD and the associated statistical uncertainty for key dust regions around the globe with which model dust schemes can be evaluated. Exploring the regional and seasonal differences in dust AOD between our observationally based estimate and the four models in this study, we find that emissions in Africa are often overrepresented at the expense of Asian and Middle Eastern emissions and that dust removal appears to be too rapid in most models.« less

An observationally constrained estimate of global dust aerosol optical depth

DOE PAGES

Ridley, David A.; Heald, Colette L.; Kok, Jasper F.; ...

2016-12-06

Here, the role of mineral dust in climate and ecosystems has been largely quantified using global climate and chemistry model simulations of dust emission, transport, and deposition. However, differences between these model simulations are substantial, with estimates of global dust aerosol optical depth (AOD) that vary by over a factor of 5. Here we develop an observationally based estimate of the global dust AOD, using multiple satellite platforms, in situ AOD observations and four state-of-the-science global models over 2004–2008. We estimate that the global dust AOD at 550 nm is 0.030 ± 0.005 (1σ), higher than the AeroCom model medianmore » (0.023) and substantially narrowing the uncertainty. The methodology used provides regional, seasonal dust AOD and the associated statistical uncertainty for key dust regions around the globe with which model dust schemes can be evaluated. Exploring the regional and seasonal differences in dust AOD between our observationally based estimate and the four models in this study, we find that emissions in Africa are often overrepresented at the expense of Asian and Middle Eastern emissions and that dust removal appears to be too rapid in most models.« less

Linguine sign at MR imaging: does it represent the collapsed silicone implant shell?

PubMed

Gorczyca, D P; DeBruhl, N D; Mund, D F; Bassett, L W

1994-05-01

One intact and one ruptured single-lumen implant were surgically placed in a rabbit. Magnetic resonance (MR) imaging was performed before and after surgical removal, and the ruptured implant was imaged after removal of the implant shell. Multiple curvilinear hypointense lines (linguine sign) were present in the MR images of the ruptured implant and of the implant shell alone immersed in saline solution but not in the image of the free silicone. The collapsed implant shell in a ruptured silicone implant does cause the linguine sign.

Multiple piece turbine blade/vane

DOEpatents

Kimmel, Keith D

2013-02-05

An air cooled turbine blade or vane of a spar and shell construction with the shell made from a high temperature resistant material that must be formed from an EDM process. The shell and the spar both have a number of hooks extending in a spanwise direction and forming a contact surface that is slanted such that a contact force increases as the engaging hooks move away from one another. The slanted contact surfaces on the hooks provides for an better seal and allows for twisting between the shell and the spar while maintaining a tight fit.

Eagle Nebula Flaunts its Infrared Feathers

NASA Technical Reports Server (NTRS)

2007-01-01

[figure removed for brevity, see original site] Figure 1 [figure removed for brevity, see original site] [figure removed for brevity, see original site] Figure 2 Figure 3

This set of images from NASA's Spitzer Space Telescope shows the Eagle nebula in different hues of infrared light. Each view tells a different tale. The left picture shows lots of stars and dusty structures with clarity. Dusty molecules found on Earth called polycyclic aromatic hydrocarbons produce most of the red; gas is green and stars are blue.

The middle view is packed with drama, because it tells astronomers that a star in this region violently erupted, or went supernova, heating surrounding dust (orange). This view also reveals that the hot dust is shell shaped, another indication that a star exploded.

The final picture highlights the contrast between the hot, supernova-heated dust (green) and the cooler dust making up the region's dusty star-forming clouds and towers (red, blue and purple).

The left image is a composite of infrared light with the following wavelengths: 3.6 microns (blue); 4.5 microns (green); 5.8 microns (orange); and 8 microns (red). The right image includes longer infrared wavelengths, and is a composite of light of 4.5 to 8.0 microns (blue); 24 microns (green); and 70 microns (red). The middle image is made up solely of 24-micron light.

A Dielectric-Filled Waveguide Antenna Element for 3D Imaging Radar in High Temperature and Excessive Dust Conditions.

PubMed

Xu, Ding; Li, Zhiping; Chen, Xianzhong; Wang, Zhengpeng; Wu, Jianhua

2016-08-22

Three-dimensional information of the burden surface in high temperature and excessive dust industrial conditions has been previously hard to obtain. This paper presents a novel microstrip-fed dielectric-filled waveguide antenna element which is resistant to dust and high temperatures. A novel microstrip-to-dielectric-loaded waveguide transition was developed. A cylinder and cuboid composite structure was employed at the terminal of the antenna element, which improved the return loss performance and reduced the size. The proposed antenna element was easily integrated into a T-shape multiple-input multiple-output (MIMO) imaging radar system and tested in both the laboratory environment and real blast furnace environment. The measurement results show that the proposed antenna element works very well in industrial 3D imaging radar.

Kinematic arguments against single relativistic shell models for GRBs

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

Fenimore, E.E.; Ramirez, E.; Sumner, M.C.

1997-09-01

Two main types of models have been suggested to explain the long durations and multiple peaks of Gamma Ray Bursts (GRBs). In one, there is a very quick release of energy at a central site resulting in a single relativistic shell that produces peaks in the time history through its interactions with the ambient material. In the other, the central site sporadically releases energy over hundreds of seconds forming a peak with each burst of energy. The authors show that the average envelope of emission and the presence of gaps in GRBs are inconsistent with a single relativistic shell. Theymore » estimate that the maximum fraction of a single shell that can produce gamma-rays in a GRB with multiple peaks is 10{sup {minus}3}, implying that single relativistic shells require 10{sup 3} times more energy than previously thought. They conclude that either the central site of a GRB must produce {approx}10{sup 51} erg/s{sup {minus}1} for hundreds of seconds, or the relativistic shell must have structure on a scales the order of {radical}{epsilon}{Gamma}{sup {minus}1}, where {Gamma} is the bulk Lorentz factor ({approximately}10{sup 2} to 10{sup 3}) and {epsilon} is the efficiency.« less

Dust measurements in tokamaks (invited).

PubMed

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

2008-10-01

Dust production and accumulation present potential safety and operational issues for the ITER. Dust diagnostics can be divided into two groups: diagnostics of dust on surfaces and diagnostics of dust in plasma. Diagnostics from both groups are employed in contemporary tokamaks; new diagnostics suitable for ITER are also being developed and tested. Dust accumulation in ITER is likely to occur in hidden areas, e.g., between tiles and under divertor baffles. A novel electrostatic dust detector for monitoring dust in these regions has been developed and tested at PPPL. In the DIII-D tokamak dust 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 dust content in the edge plasmas and trends in the dust production rates within this size range have been established. Individual dust particles are observed by visible imaging using fast framing cameras, detecting dust particles of a few microns in diameter and larger. Dust 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 dust dynamics modeling, precharacterized carbon dust has been injected into the lower divertor of DIII-D. Injected dust 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 dust. The latter observation can be used in the design of novel dust survey diagnostics.

The Eagle Nebula: a spectral template for star forming regions

NASA Astrophysics Data System (ADS)

Flagey, Nicolas; Boulanger, Francois; Carey, Sean; Compiegne, Mathieu; Dwek, Eli; Habart, Emilie; Indebetouw, Remy; Montmerle, Thierry; Noriega-Crespo, Alberto

2008-03-01

IRAC and MIPS have revealed spectacular images of massive star forming regions in the Galaxy. These vivid illustrations of the interaction between the stars, through their winds and radiation, and their environment, made of gas and dust, still needs to be explained. The large scale picture of layered shells of gas components, is affected by the small scale interaction of stars with the clumpy medium that surrounds them. To understand spatial variations of physical conditions and dust properties on small scales, spectroscopic imaging observations are required on a nearby object. The iconic Eagle Nebula (M16) is one of the nearest and most observed star forming region of our Galaxy and as such, is a well suited template to obtain this missing data set. We thus propose a complete spectral map of the Eagle Nebula (M16) with the IRS/Long Low module (15-38 microns) and MIPS/SED mode (55-95 microns). Analysis of the dust emission, spectral features and continuum, and of the H2 and fine-structure gas lines within our models will provide us with constraints on the physical conditions (gas ionization state, pressure, radiation field) and dust properties (temperature, size distribution) at each position within the nebula. Only such a spatially and spectrally complete map will allow us to characterize small scale structure and dust evolution within the global context and understand the impact of small scale structure on the evolution of dusty star forming regions. This project takes advantage of the unique ability of IRS at obtaining sensitive spectral maps covering large areas.

A Consolidated Block Grant Proposal to Carry Out the Analysis of Data from the ISO Satellite

NASA Technical Reports Server (NTRS)

Allen, Ron

2000-01-01

This block grant covers the activities of three research groups at STScI: search for cold molecular hydrogen in the galaxy; dust characterization in circumstellar shells around evolved massive stars; and the relationship between dust absorption and emission in galaxies. We proposed to group the efforts and resources available to several approved ISO projects in order to more efficiently deal with the data reduction and analysis. We give a brief description of primary objectives and scope of each project, along with the final status of the project as of the expiration date of the grant. Owing to many delays on the part of the ISO Project, the calibrated data was received very late, which resulted in significant delays in deriving the results. In addition, for one of the components of this project, the ISO data was finally determined to be of too low a quality to be useful.

SIRTF Tools for DIRT

NASA Astrophysics Data System (ADS)

Pound, M. W.; Wolfire, M. G.; Amarnath, N. S.

2003-12-01

The Dust InfraRed ToolBox (DIRT - a part of the Web Infrared ToolShed, or WITS, located at http://dustem.astro.umd.edu) is a Java applet for modeling astrophysical processes in circumstellar shells around young and evolved stars. DIRT has been used by the astrophysics community for about 5 years. Users can automatically and efficiently search grids of pre-calculated models to fit their data. A large set of physical parameters and dust types are included in the model database, which contains over 500,000 models. We are adding new functionality to DIRT to support new missions like SIRTF and SOFIA. A new Instrument module allows for plotting of the model points convolved with the spatial and spectral responses of the selected instrument. This lets users better fit data from specific instruments. Currently, we have implemented modules for the Infrared Array Camera (IRAC) and Multiband Imaging Photometer (MIPS) on SIRTF.

On the formation of molecules and solid-state compounds from the AGB to the PN phases

NASA Astrophysics Data System (ADS)

García-Hernández, D. A.; Manchado, A.

2016-07-01

During the asymptoyic giant branch (AGB) phase, different elements are dredge- up to the stellar surface depending on progenitor mass and metallicity. When the mass loss increases at the end of the AGB, a circumstellar dust shell is formed, where different (C-rich or O-rich) molecules and solid-state compounds are formed. These are further processed in the transition phase between AGB stars and planetary nebulae (PNe) to create more complex organic molecules and inorganic solid-state compounds (e.g., polycyclic aromatic hydrocarbons, fullerenes, and graphene precursors in C-rich environments and oxides and crystalline silicates in O-rich ones). We present an observational review of the different molecules and solid-state materials that are formed from the AGB to the PN phases. We focus on the formation routes of complex fullerene (and fullerene-based) molecules as well as on the level of dust processing depending on metallicity.

Prevalence and Antimicrobial Resistance of Enterobacteriaceae in Shell Eggs from Small-Scale Poultry Farms and Farmers' Markets.

PubMed

Kilonzo-Nthenge, A; Nahashon, S N; Godwin, S; Liu, S; Long, D

2016-12-01

Public health concerns over the emergence of antimicrobial resistant bacteria have increased recently. The purpose of this study was to investigate the prevalence of antimicrobial resistant Enterobacteriaceae in shell eggs purchased from small poultry farms and farmers' markets. A total of 504 eggs were pooled to make 252 composite samples, consisting of 2 eggs per composite. The microbial quality of shell eggs was determined by standard quantitative, biochemical, and PCR techniques. Susceptibility to 13 antimicrobial agents was determined by the Kirby-Bauer disk diffusion technique, and results were interpreted based on Clinical and Laboratory Standards Institute values. Shell eggs and egg contents were positive for Escherichia coli (11.9 and 5.2%, respectively), Enterobacter (9.1 and 7.9%), and Serratia (11.5 and 4.8%). Salmonella was isolated from 3.6% of egg shells but not from egg contents. Mean (±SD) Enterobacteriaceae levels (4.4 ± 2.0 log CFU per eggshell) on shell eggs from poultry farms was significantly higher (P ≤ 0.05) than that on shell eggs from farmers' markets (2.1 ± 1.3 log CFU per eggshell). Of the 134 isolates recovered, resistance among isolates from farm and market shell eggs to erythromycin was most common (48.5 and 32.8%, respectively) followed by ampicillin (44.8 and 17.2%), and tetracycline (29.9 and 17.2%). The multiple antibiotic resistance index value for E. coli and Pantoea was 0.62, and that for Salmonella and Klebsiella terrigena was 0.08, indicating that Enterobacteriaceae in shell eggs can be resistant to multiple antimicrobial agents. These data reveal that shell eggs from small poultry farms and farmers' markets can harbor antimicrobial resistant pathogenic and commensal bacteria. Thus, failure to properly handle shell eggs poses a potential health hazard to consumers.

MERLIN observations of water maser proper motions in VY Canis Majoris

NASA Astrophysics Data System (ADS)

Richards, A. M. S.; Yates, J. A.; Cohen, R. J.

1998-09-01

MERLIN observations of the 22-GHz water masers in the circumstellar envelope of the supergiant VY CMa show an ellipsoidal distribution with a maximum extent of 700 mas east-west and 400 mas north-south. Comparison with observations made nine years earlier shows that the majority of maser features have survived and show proper motions throughout the region. The mean change in position is 28 mas and the proper motions are generally directed away from the assumed stellar position, and tend to be larger for features at greater projected distances. If the H_2O maser region is modelled as a partially filled thick spherical shell, and VY CMa is at a distance of 1.5 kpc, then the proper motion velocities in the direction of expansion are between 8kms^-1 at a distance of 75 mas from the assumed stellar position and 32kms^-1 at 360 mas. These velocities are consistent with the H_2O maser spectral line velocities which correspond to a maximum expansion velocity of 36kms^-1 at 400 mas from the assumed stellar position. These observations are consistent with radiation pressure on dust providing the force to accelerate the stellar wind as it passes through the H_2O maser shell. The H_2O maser region is elongated in the same direction as the dusty nebula around VY CMa. The water masers illuminate the small-scale dynamics and clumpiness which show the role of dust in driving the outflow. The overall ellipsoidal shape may be due to properties of the dust, such as its behaviour in the stellar magnetic field, or to interaction between the wind and circumstellar material. Maser monitoring also shows the difference between changes on the time-scale of stellar variability (a few years) and possible stages in the evolution of VY CMa to its likely fate as a supernova.

THE ORION H ii REGION AND THE ORION BAR IN THE MID-INFRARED

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

Salgado, F.; Tielens, A. G. G. M.; Berné, O.

2016-10-20

We present mid-infrared photometry of the Orion bar obtained with the Faint Object infraRed Camera for the SOFIA Telescope (FORCAST) on board SOFIA at 6.4, 6.6, 7.7, 19.7, 31.5, and 37.1 μ m. By complementing this observation with archival FORCAST and Herschel /PACS images, we are able to construct a complete infrared spectral energy distribution of the Huygens region in the Orion nebula. Comparing the infrared images with gas tracers, we find that PACS maps trace the molecular cloud, while the FORCAST data trace the photodissociation region (PDR) and the H ii region. Analysis of the energetics of the regionmore » reveal that the PDR extends for 0.28 pc along the line of sight and that the bar is inclined at an angle of 4°. The infrared and submillimeter images reveal that the Orion bar represents a swept-up shell with a thickness of 0.1 pc. The mass of the shell implies a shock velocity of ≃3 km s{sup −1} and an age of ≃10{sup 5} years for the H ii region. Our analysis shows that the UV and infrared dust opacities in the H ii region and the PDR are a factor 5 to 10 lower than in the diffuse interstellar medium. In the ionized gas, Ly α photons are a major source of dust heating at distances larger than ≃0.06 pc from θ {sup 1} Ori C. Dust temperatures can be explained if the size of the grains is between 0.1 and 1 μ m. We derive the photoelectric heating efficiency of the atomic gas in the Orion bar. The results are in good qualitative agreement with models and the quantitative differences indicate a decreased polycyclic aromatic hydrocarbon abundance in this region.« less

Detecting dust hits at Enceladus, Saturn and beyond using CAPS / ELS data from Cassini

NASA Astrophysics Data System (ADS)

Vandegriff, J. D.; Stoneberger, P. J.; Jones, G.; Waite, J. H., Jr.

2016-12-01

It has recently been shown (1) that the impact of hypervelocity dust grains on the Cassini spacecraft can be detected by the Cassini Plasma Spectrometer (CAPS) Electron Spectrometer (ELS) instrument. For multiple Enceladus flybys, fine scale features in the lower energy regime of ELS energy spectra can be explained as short-duration, isotropic plasma clouds due to dust impacts. We have developed an algorithm for detecting these hypervelocity dust impacts, and the list of such impacts during Enceladus flybys will be presented. We also present preliminary results obtained when using the algorithm to search for dust impacts in other regions of Saturn's magnetosphere as well as in the solar wind. (1) Jones, Geraint, Hypervelocity dust impact signatures detected by Cassini CAPS-ELS in the Enceladus plume, MOP Meeting, June 1-5, 2015, Atlanta, GA

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

Rudakov, D. L.; Yu, J. H.; Boedo, J. A.

Dust production and accumulation present potential safety and operational issues for the ITER. Dust diagnostics can be divided into two groups: diagnostics of dust on surfaces and diagnostics of dust in plasma. Diagnostics from both groups are employed in contemporary tokamaks; new diagnostics suitable for ITER are also being developed and tested. Dust accumulation in ITER is likely to occur in hidden areas, e.g., between tiles and under divertor baffles. A novel electrostatic dust detector for monitoring dust in these regions has been developed and tested at PPPL. In the DIII-D tokamak dust diagnostics include Mie scattering from Nd:YAG lasers,more » visible imaging, and spectroscopy. Laser scattering is able to resolve particles between 0.16 and 1.6 {mu}m in diameter; using these data the total dust content in the edge plasmas and trends in the dust production rates within this size range have been established. Individual dust particles are observed by visible imaging using fast framing cameras, detecting dust particles of a few microns in diameter and larger. Dust 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 dust dynamics modeling, precharacterized carbon dust has been injected into the lower divertor of DIII-D. Injected dust is seen by cameras, and spectroscopic diagnostics observe an increase in carbon line (CI, CII, C{sub 2} dimer) and thermal continuum emissions from the injected dust. The latter observation can be used in the design of novel dust survey diagnostics.« less

Multiple Scattering Effects in EXAFS (Extended X-Ray Absorption Fine Structure): Comparison between Theory and Experiment for Pt Metal.

DTIC Science & Technology

1984-05-29

radial distribution and inverse transform of this range. The region commonly used for the inverse transform usually corresponds to the first or second...r-space and comparing it with the corresponding model function. Figure 5 shows the filtered spectra (k weighting), where the pe. 48 allowed inverse ... transform range was successively increased from the radial distance corresponding to the first shell to all the first four shells. There are no multiple

MISR Decadal Observations of Mineral Dust: Property Characterization and Climate Applications

NASA Technical Reports Server (NTRS)

Kalashnikova, Olga V.; Garay, Michael J.; Sokolik, Irina; Kahn, Ralph A.; Lyapustin, A.; Diner, David J.; Lee, Jae N.; Torres, Omar; Leptoukh, Gregory G.; Sabbah, Ismail

2012-01-01

The Multi-angle Imaging SpectroRadiometer (MISR) provides a unique, independent source of data for studying dust emission and transport. MISR's multiple view angles allow the retrieval of aerosol properties over bright surfaces, and such retrievals have been shown to be sensitive to the non-sphericity of dust aerosols over both land and water. MISR stereographic views of thick aerosol plumes allow height and instantaneous wind derivations at spatial resolutions of better than 1.1 km horizontally and 200m vertically. We will discuss the radiometric and stereo-retrieval capabilities of MISR specifically for dust, and demonstrate the use of MISR data in conjunction with other available satellite observations for dust property characterization and climate studies.First, we will discuss MISR non-spherical (dust) fraction product over the global oceans. We will show that over the Atlantic Ocean, changes in the MISR-derived non-spherical AOD fraction illustrate the evolution of dust during transport. Next, we will present a MISR satellite perspective on dust climatology in major dust source regions with a particular emphasis on the West Africa and Middle East and discuss MISR's unique strengths as well as current product biases. Finally, we will discuss MISR dust plume product and climatological applications.

Intermediate energy proton-deuteron elastic scattering

NASA Technical Reports Server (NTRS)

Wilson, J. W.

1973-01-01

A fully symmetrized multiple scattering series is considered for the description of proton-deuteron elastic scattering. An off-shell continuation of the experimentally known twobody amplitudes that retains the exchange symmeteries required for the calculation is presented. The one boson exchange terms of the two body amplitudes are evaluated exactly in this off-shell prescription. The first two terms of the multiple scattering series are calculated explicitly whereas multiple scattering effects are obtained as minimum variance estimates from the 146-MeV data of Postma and Wilson. The multiple scattering corrections indeed consist of low order partial waves as suggested by Sloan based on model studies with separable interactions. The Hamada-Johnston wave function is shown consistent with the data for internucleon distances greater than about 0.84 fm.

Multiple sources supply eolian mineral dust to the Atlantic sector of coastal Antarctica: Evidence from recent snow layers at the top of Berkner Island ice sheet

NASA Astrophysics Data System (ADS)

Bory, Aloys; Wolff, Eric; Mulvaney, Robert; Jagoutz, Emil; Wegner, Anna; Ruth, Urs; Elderfield, Harry

2010-03-01

The Sr and Nd isotopic composition of dust extracted from recent snow layers at the top of Berkner Island ice sheet (located within the Filchner-Ronne Ice Shelf at the southern end of the Weddell Sea) enables us, for the first time, to document dust provenance in Antarctica outside the East Antarctic Plateau (EAP) where all previous studies based on isotopic fingerprinting were carried out. Berkner dust displays an overall crust-like isotopic signature, characterized by more radiogenic 87Sr/ 86Sr and much less radiogenic 143Nd/ 144Nd compared to dust deposited on the EAP during glacial periods. Differences with EAP interglacial dust are not as marked but still significant, indicating that present-day Berkner dust provenance is distinct, at least to some extent, from that of the dust reaching the EAP. The fourteen snow-pit sub-seasonal samples that were obtained span a two-year period (2002-2003) and their dust Sr and Nd isotopic composition reveals that multiple sources are at play over a yearly time period. Southern South America, Patagonia in particular, likely accounts for part of the observed spring/summer dust deposition maxima, when isotopic composition is shifted towards "younger" isotopic signatures. In the spring, possible additional inputs from Australian sources would also be supported by the data. Most of the year, however, the measured isotopic signatures would be best explained by a sustained background supply from putative local sources in East Antarctica, which carry old-crust-like isotopic fingerprints. Whether the restricted East Antarctic ice-free areas produce sufficient eolian material has yet to be substantiated however. The fact that large (> 5 μm) particles represent a significant fraction of the samples throughout the entire time-series supports scenarios that involve contributions from proximal sources, either in Patagonia and/or Antarctica (possibly including snow-free areas in the Antarctic Peninsula and other areas as well). This also indicates that additional dust transport, which does not reach the EAP, must occur at low-tropospheric levels to this coastal sector of Antarctica.

Multicore-shell nanofiber architecture of polyimide/polyvinylidene fluoride blend for thermal and long-term stability of lithium ion battery separator.

PubMed

Park, Sejoon; Son, Chung Woo; Lee, Sungho; Kim, Dong Young; Park, Cheolmin; Eom, Kwang Sup; Fuller, Thomas F; Joh, Han-Ik; Jo, Seong Mu

2016-11-11

Li-ion battery, separator, multicoreshell structure, thermal stability, long-term stability. A nanofibrous membrane with multiple cores of polyimide (PI) in the shell of polyvinylidene fluoride (PVdF) was prepared using a facile one-pot electrospinning technique with a single nozzle. Unique multicore-shell (MCS) structure of the electrospun composite fibers was obtained, which resulted from electrospinning a phase-separated polymer composite solution. Multiple PI core fibrils with high molecular orientation were well-embedded across the cross-section and contributed remarkable thermal stabilities to the MCS membrane. Thus, no outbreaks were found in its dimension and ionic resistance up to 200 and 250 °C, respectively. Moreover, the MCS membrane (at ~200 °C), as a lithium ion battery (LIB) separator, showed superior thermal and electrochemical stabilities compared with a widely used commercial separator (~120 °C). The average capacity decay rate of LIB for 500 cycles was calculated to be approximately 0.030 mAh/g/cycle. This value demonstrated exceptional long-term stability compared with commercial LIBs and with two other types (single core-shell and co-electrospun separators incorporating with functionalized TiO 2 ) of PI/PVdF composite separators. The proper architecture and synergy effects of multiple PI nanofibrils as a thermally stable polymer in the PVdF shell as electrolyte compatible polymers are responsible for the superior thermal performance and long-term stability of the LIB.

Multicore-shell nanofiber architecture of polyimide/polyvinylidene fluoride blend for thermal and long-term stability of lithium ion battery separator

PubMed Central

Park, Sejoon; Son, Chung Woo; Lee, Sungho; Kim, Dong Young; Park, Cheolmin; Eom, Kwang Sup; Fuller, Thomas F.; Joh, Han-Ik; Jo, Seong Mu

2016-01-01

Li-ion battery, separator, multicoreshell structure, thermal stability, long-term stability. A nanofibrous membrane with multiple cores of polyimide (PI) in the shell of polyvinylidene fluoride (PVdF) was prepared using a facile one-pot electrospinning technique with a single nozzle. Unique multicore-shell (MCS) structure of the electrospun composite fibers was obtained, which resulted from electrospinning a phase-separated polymer composite solution. Multiple PI core fibrils with high molecular orientation were well-embedded across the cross-section and contributed remarkable thermal stabilities to the MCS membrane. Thus, no outbreaks were found in its dimension and ionic resistance up to 200 and 250 °C, respectively. Moreover, the MCS membrane (at ~200 °C), as a lithium ion battery (LIB) separator, showed superior thermal and electrochemical stabilities compared with a widely used commercial separator (~120 °C). The average capacity decay rate of LIB for 500 cycles was calculated to be approximately 0.030 mAh/g/cycle. This value demonstrated exceptional long-term stability compared with commercial LIBs and with two other types (single core-shell and co-electrospun separators incorporating with functionalized TiO2) of PI/PVdF composite separators. The proper architecture and synergy effects of multiple PI nanofibrils as a thermally stable polymer in the PVdF shell as electrolyte compatible polymers are responsible for the superior thermal performance and long-term stability of the LIB. PMID:27833132

Fabrication of core-shell micro/nanoparticles for programmable dual drug release by emulsion electrospraying

NASA Astrophysics Data System (ADS)

Wang, Yazhou; Zhang, Yiqiong; Wang, Bochu; Cao, Yang; Yu, Qingsong; Yin, Tieying

2013-06-01

The study aimed at constructing a novel drug delivery system for programmable multiple drug release controlled with core-shell structure. The core-shell structure consisted of chitosan nanoparticles as core and polyvinylpyrrolidone micro/nanocoating as shell to form core-shell micro/nanoparticles, which was fabricated by ionic gelation and emulsion electrospray methods. As model drug agents, Naproxen and rhodamine B were encapsulated in the core and shell regions, respectively. The core-shell micro/nanoparticles thus fabricated were characterized and confirmed by scanning electron microscope, transmission electron microscope, and fluorescence optical microscope. The core-shell micro/nanoparticles showed good release controllability through drug release experiment in vitro. It was noted that a programmable release pattern for dual drug agents was also achieved by adjusting their loading regions in the core-shell structures. The results indicate that emulsion electrospraying technology is a promising approach in fabrication of core-shell micro/nanoparticles for programmable dual drug release. Such a novel multi-drug delivery system has a potential application for the clinical treatment of cancer, tuberculosis, and tissue engineering.

Evidence for Reduced, Carbon-rich Regions in the Solar Nebula from an Unusual Cometary Dust Particle

NASA Astrophysics Data System (ADS)

De Gregorio, Bradley T.; Stroud, Rhonda M.; Nittler, Larry R.; Kilcoyne, A. L. David

2017-10-01

Geochemical indicators in meteorites imply that most formed under relatively oxidizing conditions. However, some planetary materials, such as the enstatite chondrites, aubrite achondrites, and Mercury, were produced in reduced nebular environments. Because of large-scale radial nebular mixing, comets and other Kuiper Belt objects likely contain some primitive material related to these reduced planetary bodies. Here, we describe an unusual assemblage in a dust particle from comet 81P/Wild 2 captured in silica aerogel by the NASA Stardust spacecraft. The bulk of this ˜20 μm particle is comprised of an aggregate of nanoparticulate Cr-rich magnetite, containing opaque sub-domains composed of poorly graphitized carbon (PGC). The PGC forms conformal shells around tiny 5-15 nm core grains of Fe carbide. The C, N, and O isotopic compositions of these components are identical within errors to terrestrial standards, indicating a formation inside the solar system. Magnetite compositions are consistent with oxidation of reduced metal, similar to that seen in enstatite chondrites. Similarly, the core-shell structure of the carbide + PGC inclusions suggests a formation via FTT reactions on the surface of metal or carbide grains in warm, reduced regions of the solar nebula. Together, the nanoscale assemblage in the cometary particle is most consistent with the alteration of primary solids condensed from a C-rich, reduced nebular gas. The nanoparticulate components in the cometary particle provide the first direct evidence from comets of reduced, carbon-rich regions that were present in the solar nebula.

Predator-prey interactions between shell-boring beetle larvae and rock-dwelling land snails.

PubMed

Baalbergen, Els; Helwerda, Renate; Schelfhorst, Rense; Castillo Cajas, Ruth F; van Moorsel, Coline H M; Kundrata, Robin; Welter-Schultes, Francisco W; Giokas, Sinos; Schilthuizen, Menno

2014-01-01

Drilus beetle larvae (Coleoptera: Elateridae) are specialized predators of land snails. Here, we describe various aspects of the predator-prey interactions between multiple Drilus species attacking multiple Albinaria (Gastropoda: Clausiliidae) species in Greece. We observe that Drilus species may be facultative or obligate Albinaria-specialists. We map geographically varying predation rates in Crete, where on average 24% of empty shells carry fatal Drilus bore holes. We also provide first-hand observations and video-footage of prey entry and exit strategies of the Drilus larvae, and evaluate the potential mutual evolutionary impacts. We find limited evidence for an effect of shell features and snail behavioral traits on inter- and intra-specifically differing predation rates. We also find that Drilus predators adjust their predation behavior based on specific shell traits of the prey. In conclusion, we suggest that, with these baseline data, this interesting predator-prey system will be available for further, detailed more evolutionary ecology studies.

Studies on mineral dust using airborne lidar, ground-based remote sensing, and in situ instrumentation

NASA Astrophysics Data System (ADS)

Marenco, Franco; Ryder, Claire; Estellés, Victor; Segura, Sara; Amiridis, Vassilis; Proestakis, Emmanouil; Marinou, Eleni; Tsekeri, Alexandra; Smith, Helen; Ulanowski, Zbigniew; O'Sullivan, Debbie; Brooke, Jennifer; Pradhan, Yaswant; Buxmann, Joelle

2018-04-01

In August 2015, the AER-D campaign made use of the FAAM research aircraft based in Cape Verde, and targeted mineral dust. First results will be shown here. The campaign had multiple objectives: (1) lidar dust mapping for the validation of satellite and model products; (2) validation of sunphotometer remote sensing with airborne measurements; (3) coordinated measurements with the CATS lidar on the ISS; (4) radiative closure studies; and (5) the validation of a new model of dustsonde.

Harmonic Quantum Coherence of Multiple Excitons in PbS/CdS Core-Shell Nanocrystals

NASA Astrophysics Data System (ADS)

Tahara, Hirokazu; Sakamoto, Masanori; Teranishi, Toshiharu; Kanemitsu, Yoshihiko

2017-12-01

The generation and recombination dynamics of multiple excitons in nanocrystals (NCs) have attracted much attention from the viewpoints of fundamental physics and device applications. However, the quantum coherence of multiple exciton states in NCs still remains unclear due to a lack of experimental support. Here, we report the first observation of harmonic dipole oscillations in PbS/CdS core-shell NCs using a phase-locked interference detection method for transient absorption. From the ultrafast coherent dynamics and excitation-photon-fluence dependence of the oscillations, we found that multiple excitons cause the harmonic dipole oscillations with ω , 2 ω , and 3 ω oscillations, even though the excitation pulse energy is set to the exciton resonance frequency, ω . This observation is closely related to the quantum coherence of multiple exciton states in NCs, providing important insights into multiple exciton generation mechanisms.

The Electrostatic Environments of Mars and the Moon

NASA Technical Reports Server (NTRS)

Calle, Carlos I.

2011-01-01

The electrical activity present in the environment near the surfaces of Mars and the moon has very different origins and presents a challenge to manned and robotic planetary exploration missions. Mars is covered with a layer of dust that has been redistributed throughout the entire planet by global dust storms. Dust, levitated by these storms as well as by the frequent dust devils, is expected to be electrostatically charged due to the multiple grain collisions in the dust-laden atmosphere. Dust covering the surface of the moon is expected to be electrostatically charged due to the solar wind, cosmic rays, and the solar radiation itself through the photoelectric effect. Electrostatically charged dust has a large tendency to adhere to surfaces. NASA's Mars exploration rovers have shown that atmospheric dust falling on solar panels can decrease their efficiency to the point of rendering the rover unusable. And as the Apollo missions to the moon showed, lunar dust adhesion can hinder manned and unmanned lunar exploration activities. Taking advantage of the electrical activity on both planetary system bodies, dust removal technologies are now being developed that use electrostatic and dielectrophoretic forces to produce controlled dust motion. This paper presents a short review of the theoretical and semiempirical models that have been developed for the lunar and Martian electrical environments.

Mortality from non‐malignant respiratory diseases among people with silicosis in Hong Kong: exposure–response analyses for exposure to silica dust

PubMed Central

Tse, L A; Yu, I T S; Leung, C C; Tam, W; Wong, T W

2007-01-01

Objectives To examine the exposure–response relationships between various indices of exposure to silica dust and the mortality from non‐malignant respiratory diseases (NMRDs) or chronic obstructive pulmonary diseases (COPDs) among a cohort of workers with silicosis in Hong Kong. Methods The concentrations of respirable silica dust were assigned to each industry and job task according to historical industrial hygiene measurements documented previously in Hong Kong. Exposure indices included cumulative dust exposure (CDE) and mean dust concentration (MDC). Penalised smoothing spline models were used as a preliminary step to detect outliers and guide further analyses. Multiple Cox's proportional hazard models were used to estimate the dust effects on the risk of mortality from NMRDs or COPDs after truncating the highest exposures. Results 371 of the 853 (43.49%) deaths occurring among 2789 workers with silicosis during 1981–99 were from NMRDs, and 101 (27.22%) NMRDs were COPDs. Multiple Cox's proportional hazard models showed that CDE (p = 0.009) and MDC (p<0.001) were significantly associated only with NMRD mortality. Subgroup analysis showed that deaths from NMRDs (p<0.01) and COPDs (p<0.05) were significantly associated with both CDE and MDC among underground caisson workers and among those ever employed in other occupations with high exposure to silica dust. No exposure–response relationship was observed for surface construction workers with low exposures. A clear upward trend for both NMRDs and COPDs mortality was found with increasing severity of radiological silicosis. Conclusion This study documented an exposure–response relationship between exposure to silica dust and the risk of death from NMRDs or COPDs among workers with silicosis, except for surface construction workers with low exposures. The risk of mortality from NMRDs increased significantly with the progression of International Labor Organization categories, independent of dust effects. PMID:16973737

A multistressor, multitrait approach to assessing the effects of wind and dust on Eucalyptus tereticornis.

PubMed

Leonard, Ryan J; McArthur, Clare; Hochuli, Dieter F

2016-08-01

Plants are routinely subjected to multiple environmental stressors, and the ability to respond to these stressors determines species survival and ecological breadth. Despite stressors such as wind and dust significantly influencing plant development, morphology, and chemistry, the combined influence of these factors is yet to be investigated. We used a manipulative glasshouse approach to compare the morphological, physiological, and biomechanical responses of Eucalyptus tereticornis to the independent and combined effects of wind and dust. Wind decreased both E. tereticornis height and stem flexural stiffness. Additionally, wind had no effect on leaf physiology, nor did dust have any significant effect on any of the traits measured. Our results suggest that wind and dust in combination may have an additive effect on several plant traits and provide new insight into the effects and importance of studying wind, dust, and different stress combinations. © 2016 Botanical Society of America.

Retrieving the Height of Smoke and Dust Aerosols by Synergistic Use of Multiple Satellite Sensors

NASA Technical Reports Server (NTRS)

Lee, Jaehwa; Hsu, N. Christina; Bettenhausen, Corey; Sayer, Andrew M.; Seftor, Colin J.; Jeong, Myeong-Jae

2016-01-01

The Aerosol Single scattering albedo and Height Estimation (ASHE) algorithm was first introduced in Jeong and Hsu (2008) to provide aerosol layer height and single scattering albedo (SSA) for biomass burning smoke aerosols. By using multiple satellite sensors synergistically, ASHE can provide the height information over much broader areas than lidar observations alone. The complete ASHE algorithm uses aerosol data from MODIS or VIIRS, OMI or OMPS, and CALIOP. A simplified algorithm also exists that does not require CALIOP data as long as the SSA of the aerosol layer is provided by another source. Several updates have recently been made: inclusion of dust layers in the retrieval process, better determination of the input aerosol layer height from CALIOP, improvement in aerosol optical depth (AOD) for nonspherical dust, development of quality assurance (QA) procedure, etc.

A Dielectric-Filled Waveguide Antenna Element for 3D Imaging Radar in High Temperature and Excessive Dust Conditions

PubMed Central

Xu, Ding; Li, Zhiping; Chen, Xianzhong; Wang, Zhengpeng; Wu, Jianhua

2016-01-01

Three-dimensional information of the burden surface in high temperature and excessive dust industrial conditions has been previously hard to obtain. This paper presents a novel microstrip-fed dielectric-filled waveguide antenna element which is resistant to dust and high temperatures. A novel microstrip-to-dielectric-loaded waveguide transition was developed. A cylinder and cuboid composite structure was employed at the terminal of the antenna element, which improved the return loss performance and reduced the size. The proposed antenna element was easily integrated into a T-shape multiple-input multiple-output (MIMO) imaging radar system and tested in both the laboratory environment and real blast furnace environment. The measurement results show that the proposed antenna element works very well in industrial 3D imaging radar. PMID:27556469

The Effect of Martian Dust on Radiator Performance

NASA Technical Reports Server (NTRS)

Hollingsworth, D. Keith; Witte, Larry C.; Hinke, Jaime; Hulbert, Kathryn

2004-01-01

Experiments were performed in which the effective emittance of three types of radiator Coatings was measured as Martian dust simulant was added to the radiator face. The apparatus consisted of multiple radiator coupons on which Carbondale Red Clay dust was deposited. The coupons were powered by electric heaters, using a guard-heating configuration to achieve the accuracy required for acceptable emittance calculations. The apparatus was containing in a vacuum chamber that featured a liquid-nitrogen cooled shroud that simulated the Martian sky temperature. Radiator temperatures ranged from 250 to 350 K with sky temperatures from 185 to 248 K. Results show that as dust was added to the radiator surfaces, the effective emittance of the high - emittance coatings decreased from near 0.9 to a value of about 0.5. A low-emittance control surface, polished aluminum, demonstrated a rise in effective emittance for thin dust layers, and then a decline as the dust layer thickened. This behavior is attributed to the conductive resistance caused by the dust layer.

Characteristics and transport of organochlorine pesticides in urban environment: air, dust, rain, canopy throughfall, and runoff.

PubMed

Zhang, Wei; Ye, Youbin; Hu, Dan; Ou, Langbo; Wang, Xuejun

2010-11-01

Characteristics and transport of organochlorine pesticides (OCPs) in urban multiple environments, including air, dust, rain, canopy throughfall, and runoff water, are explored in this study. Hexachlorocyclohexanes (HCHs) dominated in both air and rain water, and dichlorodiphenyltrichloroethane (DDT) related substances showed a higher affinity to dust. Relatively high concentrations of DDT and dichlorodiphenyldichloroethylene (DDE) in air, rain and dust imply that technical DDT in the environment has been degrading, and there may be unknown local or regional emission sources that contain DDTs in the study area. Source identification showed that DDTs in Beijing urban environments with a fresh signature may originate from the atmospheric transport from remote areas. The ratio of α-/γ-HCH in dust, rain, canopy throughfall and runoff were close to 1, indicating the possible use of lindane. OCPs in runoff were transported from various sources including rain, dust, and canopy throughfall. In runoff, DDTs and hexachlorobenzene (HCB) were mainly transported from dust, and HCHs were mainly from rain and canopy throughfall.

Expanding relativistic shells and gamma-ray burst temporal structure

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

Fenimore, E.E.; Madras, C.D.; Nayakshin, S.

1996-12-01

Many models of gamma-ray bursts (GRBs) involve a shell expanding at extreme relativistic speeds. The shell of material expands in a photon-quiet phase for a period {ital t}{sub 0} and then becomes gamma-ray active, perhaps due to inhomogeneities in the interstellar medium or the generation of shocks. Based on kinematics, we relate the envelope of the emission of the event to the characteristics of the photon-quiet and photon-active phases. We initially assume local spherical symmetry wherein, on average, the same conditions prevail over the shell`s surface within angles the order of {Gamma}{sup {minus}1}, where {Gamma} is the Lorentz factor formore » the bulk motion. The contribution of the curvature to the temporal structure is comparable to the contribution from the overall expansion. As a result, GRB time histories from a shell should have an envelope similar to {open_quotes}FRED{close_quotes} (fast rise, exponential decay) events in which the rise time is related to the duration of the photon-active phase and the fall time is related to the duration of the photon-quiet phase. This result depends only on local spherical symmetry and, since most GRBs do not have such envelopes, we introduce the {open_quotes}shell symmetry{close_quotes} problem: the observed time history envelopes of most GRBs do not agree with that expected for a relativistic expanding shell. Although FREDs have the signature of a relativistic shell, they may not be due to a single shell, as required by some cosmological models. Some FREDs have precursors in which the peaks are separated by more than the expansion time required to explain FRED shape. Such a burst is most likely explained by a central engine; that is, the separation of the multiple peaks occurs because the central site produced multiple releases of energy on timescales comparable to the duration of the event. (Abstract Truncated)« less

A thermodynamic and mechanical model for the earliest Solar System: Formation via 3-d collapse of dust in the pre-Solar nebula

NASA Astrophysics Data System (ADS)

Criss, R. E.; Hofmeister, A.

2012-12-01

The fundamental and shared rotational characteristics of the Solar System (nearly circular, co-planar orbits and mostly upright axial spins of the planets) record conditions of origin, yet are not explained by prevailing 2-dimensional disk models. Current planetary spin and orbital rotational energies (R.E.) each nearly equal and linearly depend on gravitational self-potential of formation (Ug), revealing mechanical energy conservation. We derive ΔUg ˜= ΔR.E. and stability criteria from thermodynamic principles, and parlay these relationships into a detailed model of simultaneous accretion of the protoSun and planets from the dust-bearing pre-solar nebula (PSN). Gravitational heating is insignificant because Ug is negative, the 2nd law of thermodynamics must be fulfilled, and ideal gas conditions pertain until the objects were nearly fully formed. Combined conservation of angular momentum and mechanical energy during 3-dimensional collapse of spheroidal dust shells in a contracting nebula provides ΔR.E. ˜= R.E. for the central body, whereas for formation of orbiting bodies, ΔR.E.depends on the contraction of orbits during collapse. Orbital data for the inner planets follow 0.04xR.E.f ˜= -Ug which confirms conservation of angular momentum. Measured spins of the youngest stars confirm that R.E.˜= -Ug. Heat production occurs after nearly final sizes are reached via mechanisms such as shear during differential rotation and radioactivity. We focus on the dilute stage, showing that the PSN was compositionally graded due to light molecules diffusing preferentially, providing the observed planetary chemistry, and set limits on PSN mass, density, and temperature. From measured planetary masses and orbital characteristics, accounting for dissipation of spin, we deduce mechanisms and the sequence of converting a 3-d dusty cloud to the present 2-d Solar System, and infer the evolution of dust and gas densities. Duration of events is obtained from the time-dependent virial theorem. As the PSN slowly contracted, collapse of pre-solar dust in spheroidal shells simultaneously formed rocky protoplanets embedded in a dusty debris disk, creating their nearly circular co-planar orbits and upright axial spins with the same sense as orbital rotation, which were then enhanced via subsequent local contraction of nearby nebulae. Because rocky kernels at great distance out-competed the pull of the co-accreting star, gas giants formed in the outer reaches within ~3 Ma as PSN contraction hastened. This pattern repeated to form satellite systems. The PSN imploded, once constricted to within Jupiter's orbit. Afterwards, disk debris slowly spiraled toward the protoSun, cratering and heating intercepted surfaces. Our conservative 3-d model, which allows for different behaviors of gas and dust, explains key Solar System characteristics (spin, orbits, gas giants and their compositions) and second-order features (dwarf planets, comet mineralogy, satellite system sizes).

Generation of multiple toroidal dust vortices by a non-monotonic density gradient in a direct current glow discharge plasma

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

Kaur, Manjit, E-mail: manjit@ipr.res.in; Bose, Sayak; Chattopadhyay, P. K.

2015-09-15

Observation of two well-separated dust vortices in an unmagnetized parallel plate DC glow discharge plasma is reported in this paper. A non-monotonic radial density profile, achieved by an especially designed cathode structure using a concentric metallic disk and ring of different radii, is observed to produce double dust tori between cathode and anode. PIV analysis of the still images of the double tori shows oppositely rotating dust structures between the central disk and the ring. Langmuir probe measurements of background plasma shows a non-uniform plasma density profile between the disk and the ring. Location and sense of rotation of themore » dust vortices coincides with the location and direction of the radial gradient in the ion drag force caused by the radial density gradient. The experimentally observed dust vorticity matches well with the calculated one using hydrodynamic formulations with shear in ion drag dominating over the dust charge gradient. These results corroborate that a radial gradient in the ion drag force directed towards cathode is the principal cause of dust rotation.« less

Atmospheric and surface temperatures and airborne dust amounts during late southern summer from Mariner 9 IRIS data

NASA Technical Reports Server (NTRS)

Santee, M.; Crisp, D.

1992-01-01

The temperature structure and dust loading of the Martian atmosphere are investigated using thermal emission spectra recorded in 1972 by the Mariner 9 infrared interferometer spectrometer (IRIS). The analysis focuses on a subset of data consisting of approximately 2400 spectra obtained near the end of the southern summer season (L(sub s) equal to 343 deg to 348 deg), after the global dust storm had largely abated and airborne dust amounts were subsiding to background values. Simultaneous retrieval of the vertical distribution of both atmospheric temperature and dust optical depth is accomplished through an iterative procedure which is performed on each individual spectrum. The atmospheric transmittances are calculated using a Voigt quasi-random band model, which includes absorption by CO2 and dust, but neglects the effects of multiple scattering. Vertical profiles of temperature and dust optical depth are obtained using modified algorithms. These profiles are used to construct global maps of temperature and dust optical depth as functions of latitude (+/- 90 deg), altitude (approximately 0-50 km), and local time of day.

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.

Super-massive binary black holes in galaxies. Dynamical models and observed structures in Arp 5, 87, 214, 240, and NGC 4027, 6946

NASA Astrophysics Data System (ADS)

Anosova, Joanna P.

2017-06-01

On 14 Sept, 2015 The LIGO reported the first direct detection of gravitational waves and the first direct observation of a binary black hole. These observations demonstrate the existence of binary black holes in stellar systems predicted by Einstein in his general theory of relativity a century earlier.A lot of violent and complicated phenomena take place on different scales in the Universe. Many of them may be caused by multiple centers of gravitational attraction: planetary rings, accretion discs of various scales, peculiar structures of single galaxies and interacting galaxies. In this work, we show that various features of celestial objects can be understood by assuming the existence of two dominant centers of gravity in stellar systems.We study numerically the dynamical evolution of models with the central super-massive binary black holes and extended shells with numerous low-mass particles inside and around the orbits of binaries. These particles could be star clusters or gas and dust complexes. We consider several tens of thousands of initial conditions for the general three-body problem and compile them. We studied the dynamical evolution of all spherical shells together and separately. Our method permits us to study the individual trajectories of particles, their close double and triple approaches, and inspect the time-depending structures in the models. Multiple runs of the models allow us to classify the numerous strong triple interactions of the binary components with low-mass particles; frequently, the "gravitational slingshot" effect occurs in the center of systems. Such strong interactions of bodies are results in various structures with "dumb-bell" bars, close and open spirals, different types of flows, jets etc. These structures are often very similar the observed structures of galaxies.We found some combinations of the initial conditions and model parameters that produce at some time similar structures as that found in the galaxies Arp 5, 87, 214, 240, and NGC 4027, 6946. Our Figures show results of such comparison and the past and future evolution of our models.

Assessment of rangeland ecosystem conditions, Salt Creek watershed and Dugout Ranch, southeastern Utah

USGS Publications Warehouse

Bowker, M.A.; Miller, M.E.; Belote, R.T.

2012-01-01

Increasingly, dry rangelands are being valued for multiple services beyond their traditional value as a forage production system. Additional ecosystem services include the potential to store carbon in the soil and plant biomass. In addition, dust emissions from rangelands might be considered an ecosystem detriment, the opposite of an ecosystem service. Dust emitted may have far-reaching impacts, for example, reduction of local air quality, as well as altering regional water supplies through effects on snowpack. Using an extensive rangeland monitoring dataset in the greater Canyonlands region (Utah, USA), we developed a method to estimate indices of the provisioning of three ecosystem services (forage production, dust retention, C storage) and one ecosystem property (nativeness), taking into account both ecosystem type and alternative states within that ecosystem type. We also integrated these four indices into a multifunctionality index. Comparing the currently ungrazed Canyonlands National Park watersheds to the adjacent Dugout Ranch pastures, we found clearly higher multifunctionality was attained in the Park, and that this was primarily driven by greater C-storage and better dust retention. It is unlikely to maximize all benefits and minimize all detriments at the same time. Some goods and services may have synergistic interactions; for example, managing for carbon storage will increase plant and biocrust cover likely lowering dust emission. Likewise, some may have antagonistic interactions. For instance, if carbon is consumed as biomass for livestock production, then carbon storage may be reduced. Ultimately our goal should be to quantify the monetary consequences of specific land use practices for multiple ecosystem services and determine the best land use and adaptive management practices for attaining multiple ecosystem services, minimizing economic detriments, and maximizing economic benefits from multi-commodity rangelands. Our technique is the first step toward this goal, allowing the simultaneous consideration of multiple targeted ecosystem services and properties.

Asian Dust Observed During the KORUS Air Quality Mission Creates Significant Super-Micron NO3-, NH4+, and SO42- Aerosols.

NASA Astrophysics Data System (ADS)

Heim, E. W.; Dibb, J. E.; Scheuer, E. M.

2017-12-01

The KORUS mission was a collaborative effort between the Korean Institute of Environmental Research and NASA. KORUS provided a comprehensive assessment of air quality in Korea during early 2016. The intensive sampling campaign was timed to assess local photochemistry during increasing solar insolation and biogenic emissions; after the April peak in outflow of pollution and dust from central China. Chinese outflow is well characterized by Silica-Calcium rich dust. Despite the effort to avoid the period with strongest dust outflow, Ca2+ was well represented in all bulk (particle diameters up to 4.5 micron) aerosol filter samples < 3 kilometers altitude (m = 0.640 ug/m3, s = 0.759, n=880). In particular, four flights were heavily impacted by Chinese outflow :(m = 1.607 ug/m3, s = 1.149, n = 152). Back trajectories from the flight tracks of these 4 flights indicate transport from desert regions in north central China. This dust presents a basic surface for the abundant anthropogenic acids (HNO3, H2SO4) to interact with. In combination with abundant anthropogenic NH3 these acids react with CaCO3 contained in the dust in cyclic reactions that form dust cores covered in a shell of acid-base reaction products. The difference between bulk filter measurements and submicron measurements of NH4+, SO42, and NO3- made by AMS indicates substantial super-micron fractions of these anthropogenic ions at times during KORUS-AQ. During the dustiest samples (Ca2+ > 1.5ug/m3) we see marked increases in super-micron concentration of NH4+, SO42-, and NO3-, m = 1.113 ug/m3 , 2.621 ug/m3 , 4.413 ug/m3, with the super-micron contribution to total concentration averaging 47%, 45%, and 81% respectively. In contrast, low dust days (Ca2+ < 0.2ug/m3) the super-micron concentrations averaged 0.262 ug/m3, 0.510 ug/m3, -0.029 ug/m3, respectively and accounted for just 20%, 14%, and 8% of total mass. During the dust events, samples that have trajectories passing over industrial centers in eastern China approached equivalence balance between Ca2++ NH4+ and SO42-+NO3-. In contrast dusty samples that did not pass over these industrial centers during transport to the West Sea and Korea maintained excess cations, dominantly Ca2+. This suggests that dust can act as an important carrier of Chinese pollution to Korea when this saturated dust reaches the peninsula.

Simulating galactic dust grain evolution on a moving mesh

NASA Astrophysics Data System (ADS)

McKinnon, Ryan; Vogelsberger, Mark; Torrey, Paul; Marinacci, Federico; Kannan, Rahul

2018-05-01

Interstellar dust is an important component 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 dust grains implemented in the moving-mesh hydrodynamics code AREPO suited for cosmological galaxy formation simulations. We employ a particle-based method for dust subject to dynamical forces including drag and gravity. The drag force is implemented using a second-order semi-implicit integrator and validated using several dust-hydrodynamical test problems. Each dust 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 dust physical processes, including accretion, sputtering, shattering, and coagulation. We present a novel scheme for stochastically forming dust during stellar evolution and new methods for sub-cycling of dust physics time-steps. Using this model, we simulate an isolated disc galaxy to study the impact of dust physical processes that shape the interstellar grain size distribution. We demonstrate, for example, how dust 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 dust 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.

The effects of transported Asian dust on the composition and concentration of ambient fungi in Taiwan

NASA Astrophysics Data System (ADS)

Chao, H. Jasmine; Chan, Chang-Chuan; Rao, Carol Y.; Lee, Chung-Te; Chuang, Ying-Chih; Chiu, Yueh-Hsiu; Hsu, Hsiao-Hsien; Wu, Yi-Hua

2012-03-01

This study was conducted to evaluate the effects of transported Asian dust and other environmental parameters on the levels and compositions of ambient fungi in the atmosphere of northern Taiwan. We monitored Asian dust events in Taipei County, Taiwan from January 2003 to June 2004. We used duplicate Burkard portable air samplers to collect ambient fungi before, during, and after dust events. Six transported Asian dust events were monitored during the study period. Elevated concentrations of Aspergillus ( A. niger, specifically), Coelomycetes, Rhinocladiella, Sporothrix and Verticillium were noted ( p < 0.05) during Asian dust periods. Botryosporium and Trichothecium were only recovered during dust event days. Multiple regression analysis showed that fungal levels were positively associated with temperature, wind speed, rainfall, non-methane hydrocarbons and particulates with aerodynamic diameters ≤10 μm (PM10), and negatively correlated with relative humidity and ozone. Our results demonstrated that Asian dust events affected ambient fungal concentrations and compositions in northern Taiwan. Ambient fungi also had complex dynamics with air pollutants and meteorological factors. Future studies should explore the health impacts of ambient fungi during Asian dust events, adjusting for the synergistic/antagonistic effects of weather and air pollutants.

Large-scale aerosol-assisted synthesis of biofriendly Fe2O3 yolk-shell particles: a promising support for enzyme immobilization

NASA Astrophysics Data System (ADS)

Patel, Sanjay K. S.; Choi, Seung Ho; Kang, Yun Chan; Lee, Jung-Kul

2016-03-01

Multiple-shelled Fe2O3 yolk-shell particles were synthesized using the spray drying method and intended as a suitable support for the immobilization of commercial enzymes such as glucose oxidase (GOx), horseradish peroxidase (HRP), and laccase as model enzymes. Yolk-shell particles have an average diameter of 1-3 μm with pore diameters in the range of 16 to 28 nm. The maximum immobilization of GOx, HRP, and laccase resulted in the enzyme loading of 292, 307 and 398 mg per g of support, respectively. After cross-linking of immobilized laccase by glutaraldehyde, immobilization efficiency was improved from 83.5% to 90.2%. Km and Vmax values were 41.5 μM and 1722 μmol min-1 per mg protein for cross-linked laccase and those for free laccase were 29.3 μM and 1890 μmol min-1 per mg protein, respectively. The thermal stability of the enzyme was enhanced up to 18-fold upon cross-linking, and the enzyme retained 93.1% of residual activity after ten cycles of reuse. The immobilized enzyme has shown up to 32-fold higher stability than the free enzyme towards different solvents and it showed higher efficiency than free laccase in the decolorization of dyes and degradation of bisphenol A. The synthesized yolk-shell particles have 3-fold higher enzyme loading efficiency and lower acute toxicity than the commercial Fe2O3 spherical particles. Therefore, the use of unique yolk-shell structure Fe2O3 particles with multiple-shells will be promising for the immobilization of various enzymes in biotechnological applications with improved electrochemical properties. To the best of our knowledge, this is the first report on the use of one pot synthesized Fe2O3 yolk-shell structure particles for the immobilization of enzymes.Multiple-shelled Fe2O3 yolk-shell particles were synthesized using the spray drying method and intended as a suitable support for the immobilization of commercial enzymes such as glucose oxidase (GOx), horseradish peroxidase (HRP), and laccase as model enzymes. Yolk-shell particles have an average diameter of 1-3 μm with pore diameters in the range of 16 to 28 nm. The maximum immobilization of GOx, HRP, and laccase resulted in the enzyme loading of 292, 307 and 398 mg per g of support, respectively. After cross-linking of immobilized laccase by glutaraldehyde, immobilization efficiency was improved from 83.5% to 90.2%. Km and Vmax values were 41.5 μM and 1722 μmol min-1 per mg protein for cross-linked laccase and those for free laccase were 29.3 μM and 1890 μmol min-1 per mg protein, respectively. The thermal stability of the enzyme was enhanced up to 18-fold upon cross-linking, and the enzyme retained 93.1% of residual activity after ten cycles of reuse. The immobilized enzyme has shown up to 32-fold higher stability than the free enzyme towards different solvents and it showed higher efficiency than free laccase in the decolorization of dyes and degradation of bisphenol A. The synthesized yolk-shell particles have 3-fold higher enzyme loading efficiency and lower acute toxicity than the commercial Fe2O3 spherical particles. Therefore, the use of unique yolk-shell structure Fe2O3 particles with multiple-shells will be promising for the immobilization of various enzymes in biotechnological applications with improved electrochemical properties. To the best of our knowledge, this is the first report on the use of one pot synthesized Fe2O3 yolk-shell structure particles for the immobilization of enzymes. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr00346j

Near-infrared tunable multiple broadband perfect absorber base on VO2 semi-shell arrays photonic microstructure and gold reflector

NASA Astrophysics Data System (ADS)

Liang, Jiran; Li, Peng; Zhou, Liwei; Guo, Jinbang; Zhao, Yirui

2018-01-01

We proposed a metamaterial absorber which is aimed to achieve a multiple broadband absorption and tunable absorption peak in the near-infrared region. The absorber is based on VO2 semi-shell coated on the top of silica nano-particle array supported on the gold-reflective layer. Measured results show that the absorber has the multiple broadband with the absorption magnitudes more than 95% in the near infrared region. The absorption peaks can be tuned through the VO2 phase transition from metallic phase to insulator phase in the short wavelength (before λ = 1500 nm), when VO2 is at the metallic state, an absorption band appears in the long wavelength (after λ = 1500 nm). The simulation results closely match those of measured. The absorption intensity becomes stronger and absorption peaks have red shift with the increase of thickness of VO2 semi-shell. Thus, this designed tunable absorption intensity and position absorber based on VO2 can be a good choice for enhancing the performance of multiple band, this would be beneficial to the field of photo detectors, sensor and solar cell.

Urban dust in the Guanzhong basin of China, part II: A case study of urban dust pollution using the WRF-Dust model.

PubMed

Li, Nan; Long, Xin; Tie, Xuexi; Cao, Junji; Huang, Rujin; Zhang, Rong; Feng, Tian; Liu, Suixin; Li, Guohui

2016-01-15

We developed a regional dust dynamical model (WRF-Dust) to simulate surface dust concentrations in the Guanzhong (GZ) basin of China during two typical dust 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 dust 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 dust emissions have been introduced in a regional dust model in large cities of China. Our results show that by including the detailed dust sources, model performance at simulating dust pollutions in the GZ basin is significantly improved. For example, the simulated dust 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 dust 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 dust 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.

Radiative transfer modeling of dust-coated Pancam calibration target materials: Laboratory visible/near-infrared spectrogoniometry

USGS Publications Warehouse

Johnson, J. R.; Sohl-Dickstein, J.; Grundy, W.M.; Arvidson, R. E.; Bell, J.F.; Christensen, P.R.; Graff, T.; Guinness, E.A.; Kinch, K.; Morris, Robert; Shepard, M.K.

2006-01-01

Laboratory visible/near-infrared multispectral observations of Mars Exploration Rover Pancam calibration target materials coated with different thicknesses of Mars spectral analog dust were acquired under variable illumination geometries using the Bloomsburg University Goniometer. The data were fit with a two-layer radiative transfer model that combines a Hapke formulation for the dust with measured values of the substrate interpolated using a He-Torrance approach. We first determined the single-scattering albedo, phase function, opposition effect width, and amplitude for the dust using the entire data set (six coating thicknesses, three substrates, four wavelengths, and phase angles 3??-117??). The dust exhibited single-scattering albedo values similar to other Mars analog soils and to Mars Pathfinder dust and a dominantly forward scattering behavior whose scattering lobe became narrower at longer wavelengths. Opacity values for each dust thickness corresponded well to those predicted from the particles sizes of the Mars analog dust. We then restricted the number of substrates, dust thicknesses, and incidence angles input to the model. The results suggest that the dust properties are best characterized when using substrates whose reflectances are brighter and darker than those of the deposited dust and data that span a wide range of dust thicknesses. The model also determined the dust photometric properties relatively well despite limitations placed on the range of incidence angles. The model presented here will help determine the photometric properties of dust deposited on the MER rovers and to track the multiple episodes of dust deposition and erosion that have occurred at both landing sites. Copyright 2006 by the American Geophysical Union.

Multiple generations of grain aggregation in different environments preceded solar system body formation.

PubMed

Ishii, Hope A; Bradley, John P; Bechtel, Hans A; Brownlee, Donald E; Bustillo, Karen C; Ciston, James; Cuzzi, Jeffrey N; Floss, Christine; Joswiak, David J

2018-06-26

The solar system formed from interstellar dust and gas in a molecular cloud. Astronomical observations show that typical interstellar dust consists of amorphous ( a -) silicate and organic carbon. Bona fide physical samples for laboratory studies would yield unprecedented insight about solar system formation, but they were largely destroyed. The most likely repositories of surviving presolar dust are the least altered extraterrestrial materials, interplanetary dust particles (IDPs) with probable cometary origins. Cometary IDPs contain abundant submicron a- silicate grains called GEMS (glass with embedded metal and sulfides), believed to be carbon-free. Some have detectable isotopically anomalous a- silicate components from other stars, proving they are preserved dust inherited from the interstellar medium. However, it is debated whether the majority of GEMS predate the solar system or formed in the solar nebula by condensation of high-temperature (>1,300 K) gas. Here, we map IDP compositions with single nanometer-scale resolution and find that GEMS contain organic carbon. Mapping reveals two generations of grain aggregation, the key process in growth from dust grains to planetesimals, mediated by carbon. GEMS grains, some with a- silicate subgrains mantled by organic carbon, comprise the earliest generation of aggregates. These aggregates (and other grains) are encapsulated in lower-density organic carbon matrix, indicating a second generation of aggregation. Since this organic carbon thermally decomposes above ∼450 K, GEMS cannot have accreted in the hot solar nebula, and formed, instead, in the cold presolar molecular cloud and/or outer protoplanetary disk. We suggest that GEMS are consistent with surviving interstellar dust, condensed in situ, and cycled through multiple molecular clouds. Copyright © 2018 the Author(s). Published by PNAS.

Numerical Prediction of Dust. Chapter 10

NASA Technical Reports Server (NTRS)

Benedetti, Angela; Baldasano, J. M.; Basart, S.; Benincasa, F.; Boucher, O.; Brooks, M.; Chen, J. P.; Colarco, P. R.; Gong, S.; Huneeus, N.;

The First Reported Infrared Emission from the SN1006 Remnant

NASA Technical Reports Server (NTRS)

Winkler, P. Frank; Williams, Brian J.; Blair, William P.; Borkowski, Kazimierz J.; Ghavamian, Parviz; Long, Knox S.; Raymond, John C.; Reynolds, Stephen P.

2012-01-01

We report results of infrared imaging and spectroscopic observations of the SN 1006 remnant, carried out with the Spitzer Space Telescope. The 24 m image from MIPS clearly shows faint filamentary emission along the northwest rim of the remnant shell, nearly coincident with the Balmer filaments that delineate the present position of the expanding shock. The 24 m emission traces the Balmer filaments almost perfectly, but lies a few arcsec within, indicating an origin in interstellar dust heated by the shock. Subsequent decline in the IR behind the shock is presumably due largely to grain destruction through sputtering. The emission drops far more rapidly than current models predict, however, even for a higher proportion of small grains than would be found closer to the Galactic plane. The rapid drop may result in part from a grain density that has always been lowera relic effect from an earlier epoch when the shock was encountering a lower densitybut higher grain destruction rates still seem to be required. Spectra from three positions along the NW filament from the IRS instrument all show only a featureless continuum, consistent with thermal emission from warm dust. The dust-to-gas mass ratio in the pre-shock interstellar medium is lower than that expected for the Galactic ISM-as has also been observed in the analysis of IR emission from other SNRs but whose cause remains unclear. As with other SNIa remnants, SN1006 shows no evidence for dust grain formation in the supernova ejecta.

Graphitic carbon nitride nanosheet@metal-organic framework core-shell nanoparticles for photo-chemo combination therapy

NASA Astrophysics Data System (ADS)

Chen, Rui; Zhang, Jinfeng; Wang, Yu; Chen, Xianfeng; Zapien, J. Antonio; Lee, Chun-Sing

2015-10-01

Recently, nanoscale metal-organic frameworks (NMOFs) have started to be developed as a promising platform for bioimaging and drug delivery. On the other hand, combination therapies using multiple approaches are demonstrated to achieve much enhanced efficacy. Herein, we report, for the first time, core-shell nanoparticles consisting of a photodynamic therapeutic (PDT) agent and a MOF shell while simultaneously carrying a chemotherapeutic drug for effective combination therapy. In this work, core-shell nanoparticles of zeolitic-imadazolate framework-8 (ZIF-8) as shell embedded with graphitic carbon nitride (g-C3N4) nanosheets as core are fabricated by growing ZIF-8 in the presence of g-C3N4 nanosheets. Doxorubicin hydrochloride (DOX) is then loaded into the ZIF-8 shell of the core-shell nanoparticles. The combination of the chemotherapeutic effects of DOX and the PDT effect of g-C3N4 nanosheets can lead to considerably enhanced efficacy. Furthermore, the red fluorescence of DOX and the blue fluorescence of g-C3N4 nanosheets provide the additional function of dual-color imaging for monitoring the drug release process.Recently, nanoscale metal-organic frameworks (NMOFs) have started to be developed as a promising platform for bioimaging and drug delivery. On the other hand, combination therapies using multiple approaches are demonstrated to achieve much enhanced efficacy. Herein, we report, for the first time, core-shell nanoparticles consisting of a photodynamic therapeutic (PDT) agent and a MOF shell while simultaneously carrying a chemotherapeutic drug for effective combination therapy. In this work, core-shell nanoparticles of zeolitic-imadazolate framework-8 (ZIF-8) as shell embedded with graphitic carbon nitride (g-C3N4) nanosheets as core are fabricated by growing ZIF-8 in the presence of g-C3N4 nanosheets. Doxorubicin hydrochloride (DOX) is then loaded into the ZIF-8 shell of the core-shell nanoparticles. The combination of the chemotherapeutic effects of DOX and the PDT effect of g-C3N4 nanosheets can lead to considerably enhanced efficacy. Furthermore, the red fluorescence of DOX and the blue fluorescence of g-C3N4 nanosheets provide the additional function of dual-color imaging for monitoring the drug release process. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr04436g

One-pot synthesis of iniferter-bound polystyrene core nanoparticles for the controlled grafting of multilayer shells

NASA Astrophysics Data System (ADS)

Marchyk, Nataliya; Maximilien, Jacqueline; Beyazit, Selim; Haupt, Karsten; Sum Bui, Bernadette Tse

2014-02-01

A novel approach using one-pot synthesis for the production of uniform, iniferter-bound polystyrene core nanoparticles of size 30-40 nm is described. Conventional oil-in-water emulsion polymerisation of styrene and divinylbenzene, combining a hybrid initiation system (thermal and UV), triggered sequentially, was employed to form the surface-bound thiocarbamate iniferters in situ. The iniferter cores were then used as seeds for re-initiating further polymerisation by UV irradiation to produce water-compatible core-shell nanoparticles. Grafting of various shell-types is demonstrated: linear polymers of poly(N-isopropylacrylamide) brushes, crosslinked polymers bearing different surface charges and molecularly imprinted polymers. The shell thickness was readily tuned by varying the monomers' concentration and polymerisation time. Our method is straightforward and in addition, gives access to the preparation of fluorescent seeds and the possibility of grafting nanosized multiple shells. The core-shell nanoparticles were fully characterised by dynamic light scattering, transmission electron microscopy, Fourier transform infrared spectroscopy and microelemental analysis.A novel approach using one-pot synthesis for the production of uniform, iniferter-bound polystyrene core nanoparticles of size 30-40 nm is described. Conventional oil-in-water emulsion polymerisation of styrene and divinylbenzene, combining a hybrid initiation system (thermal and UV), triggered sequentially, was employed to form the surface-bound thiocarbamate iniferters in situ. The iniferter cores were then used as seeds for re-initiating further polymerisation by UV irradiation to produce water-compatible core-shell nanoparticles. Grafting of various shell-types is demonstrated: linear polymers of poly(N-isopropylacrylamide) brushes, crosslinked polymers bearing different surface charges and molecularly imprinted polymers. The shell thickness was readily tuned by varying the monomers' concentration and polymerisation time. Our method is straightforward and in addition, gives access to the preparation of fluorescent seeds and the possibility of grafting nanosized multiple shells. The core-shell nanoparticles were fully characterised by dynamic light scattering, transmission electron microscopy, Fourier transform infrared spectroscopy and microelemental analysis. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr05295h

Effect on quality of life of the mixed house dust mite/weed pollen extract immunotherapy.

PubMed

Li, Lisha; Guan, Kai

2016-07-01

Although many patients with allergic rhinitis have symptoms due to sensitization to more than one kind of allergens, and mixed allergen extracts are widely used for immunotherapy, there are few published trials. Our study aimed to evaluate the effect of multiple-allergen immunotherapy on improving the symptoms and quality of life of allergic rhinitis patients. We performed a 1-year single-center observation study of subcutaneous immunotherapy using house dust mite extract (n = 12), weed pollen extract (n = 21), or mixed house dust mite/weed pollen extract (n = 11) in 44 allergic rhinitis patients. All the allergens responsible for the symptom of each patient were included in his immunotherapy. Symptom score, medication score, and quality of life of the patients were evaluated before and after 1-year immunotherapy. Quality of life was evaluated with the Rhinoconjunctivitis Quality of Life Questionnaire. In all 3 groups receiving subcutaneous immunotherapy, significant improvement of symptom score, medication score, and quality of life was found vs. baseline at 1 year, irrespective of the allergen used. In the weed pollen season, the changes of quality of life questionnaire score after 1-year treatment were not significantly different between the weed pollen group (1.55 ± 1.24) and the mixed house dust mite/weed pollen group (1.14 ± 1.01). The same happened in the nonpollen seasons, during which dust mite immunotherapy (1.23 ± 1.63) and mixed immunotherapy (0.60 ± 0.47) did not show significantly different effect on the quality of life. The multiple-allergen immunotherapy might be effective in polysensitized allergic rhinitis patients, and could improve their quality of life. Our result did not show significant difference between the effects of multiple-allergen immunotherapy and mono-allergen immunotherapy.

Asymptotic approximations for pure bending of thin cylindrical shells

NASA Astrophysics Data System (ADS)

Coman, Ciprian D.

2017-08-01

A simplified partial wrinkling scenario for in-plane bending of thin cylindrical shells is explored by using several asymptotic strategies. The eighth-order boundary eigenvalue problem investigated here originates in the Donnel-Mushtari-Vlasov shallow shell theory coupled with a linear membrane pre-bifurcation state. It is shown that the corresponding neutral stability curve is amenable to a detailed asymptotic analysis based on the method of multiple scales. This is further complemented by an alternative WKB approximation that provides comparable information with significantly less effort.

An Investigation of Dust Storms Observed with the Mars Color Imager

NASA Technical Reports Server (NTRS)

Guzewich, Scott D.; Toigo, Anthony D.; Wang, Huiqun

2017-01-01

Daily global imaging by the Mars Color Imager (MARCI) continues the record of the Mars Orbiter Camera (MOC) and has allowed creation of a long-duration record of Martian dust storms. We observe dust storms over the first two Mars years of the MARCI record, including tracking individual storms over multiple sols, as well as tracking the growth and recession of the seasonal polar caps. Using the combined 6 Mars year record of textured dust storms (storms with visible textures on the observed dust cloud tops), we study the relationship between textured dust storm activity and meteorology (as simulated by the MarsWRF general circulation model) and surface properties. We find that textured dust storms preferentially occur in places and seasons with above average surface wind stress. Textured dust storm occurrence also has a modest linear anti-correlation with surface albedo (0.43) and topography (0.40). Lastly, we perform an empirical orthogonal function (EOF) analysis on the distribution of occurrence of textured dust storms and find that over 50 of the variance in textured dust storm activity can be explained by two EOF modes. We associate the first EOF mode with cap-edge storms just before Ls = 180deg and the second EOF mode with flushing dust storms that occur from Ls = 180-210deg and again near Ls = 320deg.

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.

NASA's Phoenix Lander on Mars, Nearly a Decade Later

NASA Image and Video Library

2018-02-20

This is one of two images taken nearly a decade apart of NASA's Mars Phoenix Lander and related hardware around the mission's May 25, 2008, landing site on far-northern Mars. By late 2017, dust had obscured much of what was visible two months after the landing. Both images were taken by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter. The one with three patches of darker ground -- where landing events removed dust -- was taken on July 20, 2008. It is Fig. 1, an excerpt of HiRISE observation PSP_009290_2485. The one with a more even coating of pale dust throughout the area was taken on Dec. 21, 2017. It is Fig. 2, an excerpt of HiRISE observation ESP_053451_2485. Both cover an area roughly 300 meters wide at 68 degrees north latitude, 234 degrees east longitude, and the two are closely matched in viewing and illumination geometry, from about five Martian years apart in northern hemisphere summers. An animation comparing the two images shows a number of changes between mid-2008 and late 2017. The lander (top) appears darker, and is now covered by dust. The dark spot created by the heat shield impact (right) is brighter, again due to dust deposition. The back shell and parachute (bottom) shows a darker parachute and brighter area of impact disturbance, thanks again to deposits of dust. We also see that the parachute has shifted in the wind, moving to the east. In August 2008, Phoenix completed its three-month mission studying Martian ice, soil and atmosphere. The lander worked for two additional months before reduced sunlight caused energy to become insufficient to keep the lander functioning. The solar-powered robot was not designed to survive through the dark and cold conditions of a Martian arctic winter. An animation and both images are available at https://photojournal.jpl.nasa.gov/catalog/PIA22223

Time dependent response of low velocity impact induced composite conical shells under multiple delamination

NASA Astrophysics Data System (ADS)

Dey, Sudip; Karmakar, Amit

2014-02-01

This paper presents the time dependent response of multiple delaminated angle-ply composite pretwisted conical shells subjected to low velocity normal impact. The finite element formulation is based on Mindlin's theory incorporating rotary inertia and effects of transverse shear deformation. An eight-noded isoparametric plate bending element is employed to satisfy the compatibility of deformation and equilibrium of resultant forces and moments at the delamination crack front. A multipoint constraint algorithm is incorporated which leads to asymmetric stiffness matrices. The modified Hertzian contact law which accounts for permanent indentation is utilized to compute the contact force, and the time dependent equations are solved by Newmark's time integration algorithm. Parametric studies are conducted with respect to triggering parameters like laminate configuration, location of delamination, angle of twist, velocity of impactor, and impactor's displacement for centrally impacted shells.

Dawning of the N =32 Shell Closure Seen through Precision Mass Measurements of Neutron-Rich Titanium Isotopes

NASA Astrophysics Data System (ADS)

Leistenschneider, E.; Reiter, M. P.; Ayet San Andrés, S.; Kootte, B.; Holt, J. D.; Navrátil, P.; Babcock, C.; Barbieri, C.; Barquest, B. R.; Bergmann, J.; Bollig, J.; Brunner, T.; Dunling, E.; Finlay, A.; Geissel, H.; Graham, L.; Greiner, F.; Hergert, H.; Hornung, C.; Jesch, C.; Klawitter, R.; Lan, Y.; Lascar, D.; Leach, K. G.; Lippert, W.; McKay, J. E.; Paul, S. F.; Schwenk, A.; Short, D.; Simonis, J.; Somà, V.; Steinbrügge, R.; Stroberg, S. R.; Thompson, R.; Wieser, M. E.; Will, C.; Yavor, M.; Andreoiu, C.; Dickel, T.; Dillmann, I.; Gwinner, G.; Plaß, W. R.; Scheidenberger, C.; Kwiatkowski, A. A.; Dilling, J.

2018-02-01

A precision mass investigation of the neutron-rich titanium isotopes Ti-5551 was performed at TRIUMF's Ion Trap for Atomic and Nuclear science (TITAN). The range of the measurements covers the N =32 shell closure, and the overall uncertainties of the Ti-5552 mass values were significantly reduced. Our results conclusively establish the existence of the weak shell effect at N =32 , narrowing down the abrupt onset of this shell closure. Our data were compared with state-of-the-art ab initio shell model calculations which, despite very successfully describing where the N =32 shell gap is strong, overpredict its strength and extent in titanium and heavier isotones. These measurements also represent the first scientific results of TITAN using the newly commissioned multiple-reflection time-of-flight mass spectrometer, substantiated by independent measurements from TITAN's Penning trap mass spectrometer.

Cumulative exposure to dust causes accelerated decline in lung function in tunnel workers

PubMed Central

Ulvestad, B; Bakke, B; Eduard, W; Kongerud, J; Lund, M

2001-01-01

OBJECTIVES—To examine whether underground construction workers exposed to tunnelling pollutants over a follow up period of 8 years have an increased risk of decline in lung function and respiratory symptoms compared with reference subjects working outside the tunnel atmosphere, and relate the findings to job groups and cumulative exposure to dust and gases.
METHODS—96 Tunnel workers and a reference group of 249 other heavy construction workers were examined in 1991 and re-examined in 1999. Exposure measurements were carried out to estimate personal cumulative exposure to total dust, respirable dust, α-quartz, oil mist, and nitrogen dioxide. The subjects answered a questionnaire on respiratory symptoms and smoking habits, performed spirometry, and had chest radiographs taken. Radiological signs of silicosis were evaluated (International Labour Organisation (ILO) classification). Atopy was determined by a multiple radioallergosorbent test (RAST).
RESULTS—The mean exposure to respirable dust and α-quartz in tunnel workers varied from 1.2-3.6 mg/m3 (respirable dust) and 0.019-0.044 mg/m3 (α-quartz) depending on job task performed. Decrease in forced expiratory volume in 1 second (FEV1) was associated with cumulative exposure to respirable dust (p<0.001) and α-quartz (p=0.02). The multiple regression model predicted that in a worker 40 years of age, the annual decrease in FEV1 would be 25 ml in a non-exposed non-smoker, 35 ml in a non-exposed smoker, and 50-63 ml in a non-smoking tunnel worker (depending on job). Compared with the reference group the odds ratio for the occurrence of new respiratory symptoms during the follow up period was increased in the tunnel workers and associated with cumulative exposure to respirable dust.
CONCLUSIONS—Cumulative exposures to respirable dust and α-quartz are the most important risk factors for airflow limitation in underground heavy construction workers, and cumulative exposure to respirable dust is the most important risk factor for respiratory symptoms. The finding of accelerated decline in lung function in tunnel workers suggests that better control of exposures is needed.


Keywords: heavy construction; respirable dust; lung function PMID:11555688

The origin of extended interstellar shells around Wolf-Rayet stars having bright optical ring nebulae

NASA Technical Reports Server (NTRS)

Nichols, J. S.; Fesen, R. A.

1994-01-01

Investigations of the interstellar environment around Wolf-Rayet (WR) stars have lead to the discovery of extended shells of gas and dust 50-100 pc in diameter in the lines of sight toward three WR stars. In this paper, several origins for these extended shells are discussed. While positional coincidences cannot be excluded, the locations of the WR stars near the projected centers of the shells, the detection of only shortward-shifted, high-velocity UV absorption line components in their IUE spectra, plus commonality of some WR star properties which are rare in the general WR star population suggest some casual connections between the WR stars and formation of interstellar shells. To access whether the high-velocity UV interstellar absorption lines are a frequent phenomenon related to WR stellar winds, we present a survey of such features in all WR stars observed with IUE through 1991. Of 35 stars studied, only four are found to have components with velocity displacements greater than 45 km/s which are not attributable to previously identified OB association superbubbles. The means a surprising 82% of non-OB association WR stars show no evidence of high-velocity gas in their lines of sight at IUE's spectral resolution, suggesting that high-velocity interstellar absorption lines are not a common consequence of Wolf-Rayet star stellar winds alone. We review the properties of three WR stars (HD 50896, HD 96548, and HD 192163) which may reside inside extended interstellar shells and find that they are similar in terms of spectral class (WN5-8), presence of an optical ring nebula, and reported photometric variability. Evaluation of possible origins of the extended shells suggests these three stars are in a post X-ray binary stage of high-mass binary star evolution. If this is correct, then the large interstellar shells detected might be evidence of either supernova remnant shells generated by the explosion of the binary's primary star, or non-conservative mass transfer during a Roche Lobe overflow stage of the binary after the supernova explosion. In either of these cases the bright optical ring nebulae associated with these three WR stars may signify recent Roche Lobe overflows consistent with spectroscopic abundance analysis.

Modelling the structure and kinematics of the Firework nebula: The nature of the GK Persei nova shell and its jet-like feature

NASA Astrophysics Data System (ADS)

Harvey, E.; Redman, M. P.; Boumis, P.; Akras, S.

2016-10-01

Aims: The shaping mechanisms of old nova remnants are probes for several important and unexplained processes, such as dust formation and the structure of evolved star nebulae. To gain a more complete understanding of the dynamics of the GK Per (1901) remnant, an examination of symmetry of the nova shell is explored, followed by a kinematical analysis of the previously detected jet-like feature in the context of the surrounding fossil planetary nebula. Methods: Faint-object high-resolution echelle spectroscopic observations and imaging were undertaken covering the knots which comprise the nova shell and the surrounding nebulosity. New imaging from the Aristarchos telescope in Greece and long-slit spectra from the Manchester Echelle Spectrometer instrument at the San Pedro Mártir observatory in Mexico were obtained, supplemented with archival observations from several other optical telescopes. Position-velocity arrays are produced of the shell, and also individual knots, and are then used for morpho-kinematic modelling with the shape code. The overall structure of the old knotty nova shell of GK Per and the planetary nebula in which it is embedded is then analysed. Results: Evidence is found for the interaction of knots with each other and with a wind component, most likely the periodic fast wind emanating from the central binary system. We find that a cylindrical shell with a lower velocity polar structure gives the best model fit to the spectroscopy and imaging. We show in this work that the previously seen jet-like feature is of low velocity. Conclusions: The individual knots have irregular tail shapes; we propose here that they emanate from episodic winds from ongoing dwarf nova outbursts by the central system. The nova shell is cylindrical, not spherical, and the symmetry axis relates to the inclination of the central binary system. Furthermore, the cylinder axis is aligned with the long axis of the bipolar planetary nebula in which it is embedded. Thus, the central binary system is responsible for the bipolarity of the planetary nebula and the cylindrical nova shell. The gradual planetary nebula ejecta versus sudden nova ejecta is the reason for the different degrees of bipolarity. We propose that the "jet" feature is an illuminated lobe of the fossil planetary nebula that surrounds the nova shell.

Empirical Model for Evaluating PM10 Concentration Caused by River Dust Episodes

PubMed Central

Lin, Chao-Yuan; Chiang, Mon-Ling; Lin, Cheng-Yu

2016-01-01

Around the estuary of the Zhuo-Shui River in Taiwan, the waters recede during the winter, causing an increase in bare land area and exposing a large amount of fine earth and sand particles that were deposited on the riverbed. Observations at the site revealed that when northeastern monsoons blow over bare land without vegetation or water cover, the fine particles are readily lifted by the wind, forming river dust, which greatly endangers the health of nearby residents. Therefore, determining which factors affect river dust and constructing a model to predict river dust concentration are extremely important in the research and development of a prototype warning system for areas at risk of river dust emissions. In this study, the region around the estuary of the Zhuo-Shui River (from the Zi-Qiang Bridge to the Xi-Bin Bridge) was selected as the research area. Data from a nearby air quality monitoring station were used to screen for days with river dust episodes. The relationships between PM10 concentration and meteorological factors or bare land area were analyzed at different temporal scales to explore the factors that affect river dust emissions. Study results showed that no single factor alone had adequate power to explain daily average or daily maximum PM10 concentration. Stepwise regression analysis of multiple factors showed that the model could not effectively predict daily average PM10 concentration, but daily maximum PM10 concentration could be predicted by a combination of wind velocity, temperature, and bare land area; the coefficient of determination for this model was 0.67. It was inferred that river dust episodes are caused by the combined effect of multiple factors. In addition, research data also showed a time lag effect between meteorological factors and hourly PM10 concentration. This characteristic was applied to the construction of a prediction model, and can be used in an early warning system for local residents. PMID:27271642

Empirical Model for Evaluating PM10 Concentration Caused by River Dust Episodes.

PubMed

Lin, Chao-Yuan; Chiang, Mon-Ling; Lin, Cheng-Yu

2016-06-02

Around the estuary of the Zhuo-Shui River in Taiwan, the waters recede during the winter, causing an increase in bare land area and exposing a large amount of fine earth and sand particles that were deposited on the riverbed. Observations at the site revealed that when northeastern monsoons blow over bare land without vegetation or water cover, the fine particles are readily lifted by the wind, forming river dust, which greatly endangers the health of nearby residents. Therefore, determining which factors affect river dust and constructing a model to predict river dust concentration are extremely important in the research and development of a prototype warning system for areas at risk of river dust emissions. In this study, the region around the estuary of the Zhuo-Shui River (from the Zi-Qiang Bridge to the Xi-Bin Bridge) was selected as the research area. Data from a nearby air quality monitoring station were used to screen for days with river dust episodes. The relationships between PM10 concentration and meteorological factors or bare land area were analyzed at different temporal scales to explore the factors that affect river dust emissions. Study results showed that no single factor alone had adequate power to explain daily average or daily maximum PM10 concentration. Stepwise regression analysis of multiple factors showed that the model could not effectively predict daily average PM10 concentration, but daily maximum PM10 concentration could be predicted by a combination of wind velocity, temperature, and bare land area; the coefficient of determination for this model was 0.67. It was inferred that river dust episodes are caused by the combined effect of multiple factors. In addition, research data also showed a time lag effect between meteorological factors and hourly PM10 concentration. This characteristic was applied to the construction of a prediction model, and can be used in an early warning system for local residents.

Interactions Between Mineral Dust, Climate, and Ocean Ecosystems

NASA Technical Reports Server (NTRS)

Gasso, Santiago; Grassian, Vicki H.; Miller, Ron L.

2010-01-01

Over the past decade, technological improvements in the chemical and physical characterization of dust have provided insights into a number of phenomena that were previously unknown or poorly understood. In addition, models are now incorporating a wider range of physical processes, which will allow us to better quantify the climatic and ecological impacts of dust. For example, some models include the effect of dust on oceanic photosynthesis and thus on atmospheric CO 2 (Friedlingstein et al. 2006). The impact of long-range dust transport, with its multiple forcings and feedbacks, is a relatively new and complex area of research, where input from several disciplines is needed. So far, many of these effects have only been parameterized in models in very simple terms. For example, the representation of dust sources remains a major uncertainty in dust modeling and estimates of the global mass of airborne dust. This is a problem where Earth scientists could make an important contribution, by working with climate scientists to determine the type of environments in which easily erodible soil particles might have accumulated over time. Geologists could also help to identify the predominant mineralogical composition of dust sources, which is crucial for calculating the radiative and chemical effects of dust but is currently known for only a few regions. Understanding how climate and geological processes control source extent and characterizing the mineral content of airborne dust are two of the fascinating challenges in future dust research.

Unexpectedly large mass loss during the thermal pulse cycle of the red giant star R Sculptoris.

PubMed

Maercker, M; Mohamed, S; Vlemmings, W H T; Ramstedt, S; Groenewegen, M A T; Humphreys, E; Kerschbaum, F; Lindqvist, M; Olofsson, H; Paladini, C; Wittkowski, M; de Gregorio-Monsalvo, I; Nyman, L-A

2012-10-11

The asymptotic-giant-branch star R Sculptoris is surrounded by a detached shell of dust and gas. The shell originates from a thermal pulse during which the star underwent a brief period of increased mass loss. It has hitherto been impossible to constrain observationally the timescales and mass-loss properties during and after a thermal pulse--parameters that determine the lifetime of the asymptotic giant branch and the amount of elements returned by the star. Here we report observations of CO emission from the circumstellar envelope and shell around R Sculptoris with an angular resolution of 1.3″. What was previously thought to be only a thin, spherical shell with a clumpy structure is revealed to also contain a spiral structure. Spiral structures associated with circumstellar envelopes have been previously seen, leading to the conclusion that the systems must be binaries. Combining the observational data with hydrodynamic simulations, we conclude that R Sculptoris is a binary system that underwent a thermal pulse about 1,800 years ago, lasting approximately 200 years. About 3 × 10(-3) solar masses of material were ejected at a velocity of 14.3 km s(-1) and at a rate around 30 times higher than the pre-pulse mass-loss rate. This shows that about three times more mass was returned to the interstellar medium during and immediately after the pulse than previously thought.

Mesoporous multi-shelled ZnO microspheres for the scattering layer of dye sensitized solar cell with a high efficiency

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

Xia, Weiwei; Mei, Chao; Zeng, Xianghua, E-mail: xhzeng@yzu.edu.cn

2016-03-14

Both light scattering and dye adsorbing are important for the power conversion efficiency PCE performance of dye sensitized solar cell (DSSC). Nanostructured scattering layers with a large specific surface area are regarded as an efficient way to improve the PCE by increasing dye adsorbing, but excess adsorbed dye will hinder light scattering and light penetration. Thus, how to balance the dye adsorbing and light penetration is a key problem to improve the PCE performance. Here, multiple-shelled ZnO microspheres with a mesoporous surface are fabricated by a hydrothermal method and are used as scattering layers on the TiO{sub 2} photoanode ofmore » the DSSC in the presence of N719 dye and iodine–based electrolyte, and the results reveal that the DSSCs based on triple shelled ZnO microsphere with a mesoporous surface exhibit an enhanced PCE of 7.66%, which is 13.0% higher than those without the scattering layers (6.78%), indicating that multiple-shelled microspheres with a mesoporous surface can ensure enough light scattering between the shells, and a favorable concentration of the adsorbed dye can improve the light penetration. These results may provide a promising pathway to obtain the high efficient DSSCs.« less

Numerical simulation of stress-strain state of electrophoretic shell molds

NASA Astrophysics Data System (ADS)

Sviridov, A. V.; Odinokov, V. I.; Dmitriev, E. A.; Evstigneev, A. I.; Bashkov, O. V.

2017-10-01

In the foundry engineering, castings obtained in one-piece non-gas-generating high-refractory electrophoretic shell molds (ShM) by investment patterns (IP) have an increased rejects percentage associated with low deformation resistance and crack resistance of the SM at different stages of their formation and manufacturing. Crack resistance of the ShM based on IP depends mainly on their stress-strain state (SSS) at various stages of mold forming. SSS decrease significantly improves their crack resistance and decreases their rejects percentage of castings occurring due to clogging and surface defects. In addition, the known methods of decreasing the SSS are still poorly understood. Thus, current research trends are to determine SSS at each stage of ShM forming and develop the ways to decrease it. Theoretical predicting of crack formation in multiple-layer axisymmetric shell molds is given in the work [1], and SSS of multiple-layer axisymmetric shell molds is given in the work [2]. Monolayer electrophoretic ShM had a lack of concern in this field, thus it became an argument for the present workMathematical Model of ShM SSS

Ordered three- and five-ply nanocomposites from ABC block terpolymer microphase separation with niobia and aluminosilicate sols

PubMed Central

Stefik, Morgan; Mahajan, Surbhi; Sai, Hiroaki; Epps, Thomas H.; Bates, Frank S.; Gruner, Sol M; DiSalvo, Francis J.; Wiesner, Ulrich

2009-01-01

We report the first use of a non-frustrated block terpolymer for the synthesis of highly ordered oxide nanocomposites containing multiple plies. The morphological behavior of 15 ISO-oxide nanocomposites was investigated spanning a large range of compositions along the ƒI=ƒS isopleth using aluminosilicate and niobia sols. Morphologies were determined by TEM and SAXS measurements. Four morphologies were identified, including core-shell hexagonal, core-shell double gyroid, three-domain lamellae, and core-shell inverse-hexagonal, in order of increasing O+oxide vol fraction. All of the resulting nanocomposites had three- or five-ply morphologies containing domains that were continuous in one, two, or three dimensions. The five-ply core-shell double gyroid phase was only found to be stable when the O+oxide domain was a minority. Removal of the polymer enabled simple and direct synthesis of mesoporous oxide materials while retaining the ordered network structure. We believe that advances in the synthesis of multi-ply nanocomposites will lead to advanced materials and devices containing multiple plies of functional materials. PMID:20209023

Ordered three- and five-ply nanocomposites from ABC block terpolymer microphase separation with niobia and aluminosilicate sols.

PubMed

Stefik, Morgan; Mahajan, Surbhi; Sai, Hiroaki; Epps, Thomas H; Bates, Frank S; Gruner, Sol M; Disalvo, Francis J; Wiesner, Ulrich

2009-11-24

We report the first use of a non-frustrated block terpolymer for the synthesis of highly ordered oxide nanocomposites containing multiple plies. The morphological behavior of 15 ISO-oxide nanocomposites was investigated spanning a large range of compositions along the ƒ(I)=ƒ(S) isopleth using aluminosilicate and niobia sols. Morphologies were determined by TEM and SAXS measurements. Four morphologies were identified, including core-shell hexagonal, core-shell double gyroid, three-domain lamellae, and core-shell inverse-hexagonal, in order of increasing O+oxide vol fraction. All of the resulting nanocomposites had three- or five-ply morphologies containing domains that were continuous in one, two, or three dimensions. The five-ply core-shell double gyroid phase was only found to be stable when the O+oxide domain was a minority. Removal of the polymer enabled simple and direct synthesis of mesoporous oxide materials while retaining the ordered network structure. We believe that advances in the synthesis of multi-ply nanocomposites will lead to advanced materials and devices containing multiple plies of functional materials.

C-Shell Cookbook

NASA Astrophysics Data System (ADS)

Currie, Malcolm J.

This cookbook describes the fundamentals of writing scripts using the UNIX C shell. It shows how to combine Starlink and private applications with shell commands and constructs to create powerful and time-saving tools for performing repetitive jobs, creating data-processing pipelines, and encapsulating useful recipes. The cookbook aims to give practical and reassuring examples to at least get you started without having to consult a UNIX manual. However, it does not offer a comprehensive description of C-shell syntax to prevent you from being overwhelmed or intimidated. The topics covered are: how to run a script, defining shell variables, prompting, arithmetic and string processing, passing information between Starlink applications, obtaining dataset attributes and FITS header information, processing multiple files and filename modification, command-line arguments and options, and loops. There is also a glossary.

The Molecular and Dust Envelope of HD 56126

NASA Astrophysics Data System (ADS)

Meixner, M.; Zalucha, A.; Ueta, T.; Fong, D.; Justtanont, K.

2004-10-01

We present millimeter interferometry images of the CO J=1-0 line emission arising in the circumstellar envelope of HD 56126 (=IRAS 07134+1005), which is one of the best-studied 21 μm proto-planetary nebulae (PPNs). The CO emission extends from 1.2" to 7" in radius from the central star and appears consistent with a simple expanding envelope, as expected for a post-AGB star. The CO envelope is very clumpy with no apparent fast wind to explain these microstructures that must have arisen during the AGB mass loss. We quantitatively model the molecular envelope using a radiative transfer code that we have modified for detached shells. Our best-fit model reveals that two sequential winds created the circumstellar envelope of HD 56126: an AGB wind that lasted 6500 yr with a mass-loss rate of 5.1×10-6 Msolar yr-1 and a more intense superwind that lasted 840 yr with a mass-loss rate of 3×10-5 Msolar yr-1 and that ended the star's life on the AGB 1240 yr ago. The total mass of this envelope is 0.059 Msolar, which indicates a lower limit progenitor mass for the system of 0.66 Msolar, quite reasonable for this low-metallicity star that probably resides in the thick disk of the Galaxy. Comparison with images of the dust emission reveals a structure similar to that of the gas in the inner regions. Using 2-D UST, we model the dust emission of this source so that the model is consistent with the CO emission model and find a total dust mass of 7.8×10-4 Msolar, a superwind-dust mass-loss rate of 1.9×10-7 Msolar yr-1 and an AGB-dust mass-loss rate of 9.6×10-8 Msolar yr-1. We derive an average gas-to-dust mass ratio of 75, which is consistent with ISM values but low for what most consider for carbon stars. Our results indicate that TiC nanocrystals are probably not the carrier of the 21 μm feature.

SOFIA/FORCAST Observations of the Luminous Blue Variables in the Galactic Center

NASA Astrophysics Data System (ADS)

Lau, Ryan M.; Herter, T. L.; Morris, M.; Adams, J. D.

2014-01-01

Three Luminous Blue Variables (LBVs) are located in the vicinity of the Quintuplet Cluster in the Galactic Center: the Pistol star, G0.120-0.048, and qF362. We present imaging at 19, 25, 31, and 37 μm of the region containing these three LBVs obtained with SOFIA using FORCAST. We study the similarities and differences between the three LBVs and address the influence of the hot, massive stars in the adjacent Quintuplet Cluster and the local ambient medium in affecting the morphology, composition, and energetics of dust in the nebulae produced from their outflows. We observe the thermal emission from the Pistol nebula, the asymmetric, compressed shell of hot dust surrounding the Pistol star and provide the first detection of thermal emission from the symmetric, hot dust envelope surrounding G0.120-0.048. However, we do not detect any emission from hot dust surrounding qF362. The Pistol and G0.120-0.048 nebulae share an identical size scale of ˜ 0.7 pc which suggests that they have similar dynamical timescales (˜ 8000 yrs) assuming similar expansion velocities of ˜ 90 km/s. The Pistol nebula exhibits a temperature gradient decreasing from north to south with values ranging from 140 - 150 K. The G0.120-0.048 nebula, which is spherically symmetric about the star, exhibits an average dust temperature of ˜ 100 K. Fits to the spectral energy distribution (SED) of the Pistol nebula with the DustEm Radiative Transfer code indicate that the nebula is composed of separate distributions of large grains (≥ 500 Å) and small grains (˜ 10 Å). DustEm model fits to the G0.120-0.048 nebula SED indicate that it contains grains smaller than 500 Å which suggests it may also contain a population of small grains. The models predict that both nebulae have a total gas mass of ˜ 2.5 M⊙ (assuming Mg/Md = 100), and a total IR luminosity of ˜ 8 × 10^5 L⊙ for the Pistol and ˜ 10^5 L⊙ for G0.120-0.048.

Subaru adaptive-optics high-spatial-resolution infrared K- and L'-band imaging search for deeply buried dual AGNs in merging galaxies

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

Imanishi, Masatoshi; Saito, Yuriko, E-mail: masa.imanishi@nao.ac.jp

2014-01-01

We present the results of infrared K- (2.2 μm) and L'-band (3.8 μm) high-spatial-resolution (<0.''2) imaging observations of nearby gas- and dust-rich infrared luminous merging galaxies, assisted by the adaptive optics system on the Subaru 8.2 m telescope. We investigate the presence and frequency of red K – L' compact sources, which are sensitive indicators of active galactic nuclei (AGNs), including AGNs that are deeply buried in gas and dust. We observed 29 merging systems and confirmed at least one AGN in all but one system. However, luminous dual AGNs were detected in only four of the 29 systems (∼14%),more » despite our method's being sensitive to buried AGNs. For multiple nuclei sources, we compared the estimated AGN luminosities with supermassive black hole (SMBH) masses inferred from large-aperture K-band stellar emission photometry in individual nuclei. We found that mass accretion rates onto SMBHs are significantly different among multiple SMBHs, such that larger-mass SMBHs generally show higher mass accretion rates when normalized to SMBH mass. Our results suggest that non-synchronous mass accretion onto SMBHs in gas- and dust-rich infrared luminous merging galaxies hampers the observational detection of kiloparsec-scale multiple active SMBHs. This could explain the significantly smaller detection fraction of kiloparsec-scale dual AGNs when compared with the number expected from simple theoretical predictions. Our results also indicate that mass accretion onto SMBHs is dominated by local conditions, rather than by global galaxy properties, reinforcing the importance of observations to our understanding of how multiple SMBHs are activated and acquire mass in gas- and dust-rich merging galaxies.« less

Mesospheric dust observations during the MAXIDUSTY campaign

NASA Astrophysics Data System (ADS)

Antonsen, Tarjei; Havnes, Ove; Fredriksen, Åshild; Friedrich, Martin; Sternovsky, Zoltan; Plane, John; Hartquist, Tom; Olsen, Sveinung; Eilertsen, Yngve; Trondsen, Espen; Mann, Ingrid; Hedin, Jonas; Gumbel, Jörg; Moen, Jøran; Latteck, Ralph; Baumgarten, Gerd; Höffner, Josef; Williams, Bifford; Hoppe, Ulf-Peter; Karlberg, Jan-Ove

2017-04-01

The MAXIDUSTY rocket payloads, launched from Andøya June 30 and July 8 2016, were equipped with dust impact detectors aiming to characterize mesospheric dust charge state, mass distribution of impact fragments and NLC/PMSE structure. One of the main scientific objectives for the campaign was to confirm that material of meteoric origin is abundant inside the icy mesospheric dust particles. The rockets were launched simultaneously with PMSE and NLC (MAXIDUSTY-1) and PMSE (MAXIDUSTY-1B) respectively, and radar measurements were made coincident with the rocket flight path. We report here on the initial results from the rocket probes and remote soundings, with emphasis on the dust impact detector results. Results from the Multiple Dust Detector (MUDD) confirm that NLC ice particles probably have a relatively high content of meteoric smoke particles with a filling factor of up to several percent. Comparisons of the DUSTY faraday bucket and PMSE show that there is no simple correlation between the two.

A map of dust reddening to 4.5 kpc from Pan-STARRS1

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

Schlafly, E. F.; Rix, H.-W.; Martin, N. F.

2014-07-01

We present a map of the dust reddening to 4.5 kpc derived from Pan-STARRS1 stellar photometry. The map covers almost the entire sky north of declination –30° at a resolution of 7'-14', and is based on the estimated distances and reddenings to more than 500 million stars. The technique is designed to map dust in the Galactic plane, where many other techniques are stymied by the presence of multiple dust clouds at different distances along each line of sight. This reddening-based dust map agrees closely with the Schlegel et al. (SFD) far-infrared emission-based dust map away from the Galactic plane,more » and the most prominent differences between the two maps stem from known limitations of SFD in the plane. We also compare the map with Planck, finding likewise good agreement in general at high latitudes. The use of optical data from Pan-STARRS1 yields reddening uncertainty as low as 25 mmag E(B – V).« less

Level and distribution of employee exposures to total and respirable wood dust in two Canadian sawmills.

PubMed

Teschke, K; Hertzman, C; Morrison, B

1994-03-01

Personal respirable (N = 230) and total (N = 237) dust measurements were made in two coastal British Columbia sawmills using a sampling strategy that randomly selected workers from all jobs in the mills over two seasons. Information about job title, department, season, weather conditions, location of the job relative to wood-cutting machines, and control measures also was collected at the time of sampling. Only 16 respirable wood dust samples were above the detection limit of 0.08 mg/m3; all 16 had levels < or = 0.20 mg/m3. Total wood dust concentrations were also low (36% less than the detection limit), with a mean of 0.51 mg/m3, and ranging from < 0.08 to 52 mg/m3. Measurements of exposure taken close to chippers, planers, and multiple saws had the highest total wood dust levels. Sawmill department and booth enclosures also were associated with wood dust concentrations, while local exhaust ventilation and weather conditions were not. Wood dust levels in this study were generally lower than in other studies of this industry, but most sawmill investigations report mean wood dust concentrations lower than those measured in the furniture and cabinetmaking industries, where concerns about wood dust exposures initially were raised.

Dust Density Distribution and Imaging Analysis of Different Ice Lines in Protoplanetary Disks

NASA Astrophysics Data System (ADS)

Pinilla, P.; Pohl, A.; Stammler, S. M.; Birnstiel, T.

2017-08-01

Recent high angular resolution observations of protoplanetary disks at different wavelengths have revealed several kinds of structures, including multiple bright and dark rings. Embedded planets are the most used explanation for such structures, but there are alternative models capable of shaping the dust in rings as it has been observed. We assume a disk around a Herbig star and investigate the effect that ice lines have on the dust evolution, following the growth, fragmentation, and dynamics of multiple dust size particles, covering from 1 μm to 2 m sized objects. We use simplified prescriptions of the fragmentation velocity threshold, which is assumed to change radially at the location of one, two, or three ice lines. We assume changes at the radial location of main volatiles, specifically H2O, CO2, and NH3. Radiative transfer calculations are done using the resulting dust density distributions in order to compare with current multiwavelength observations. We find that the structures in the dust density profiles and radial intensities at different wavelengths strongly depend on the disk viscosity. A clear gap of emission can be formed between ice lines and be surrounded by ring-like structures, in particular between the H2O and CO2 (or CO). The gaps are expected to be shallower and narrower at millimeter emission than at near-infrared, opposite to model predictions of particle trapping. In our models, the total gas surface density is not expected to show strong variations, in contrast to other gap-forming scenarios such as embedded giant planets or radial variations of the disk viscosity.

A multiyear dust devil vortex survey using an automated search of pressure time series

NASA Astrophysics Data System (ADS)

Jackson, Brian; Lorenz, Ralph

2015-03-01

Dust devils occur in arid climates on the Earth and ubiquitously on Mars, where they likely dominate the supply of atmospheric dust and influence climate. Martian dust devils have been studied with a combination of orbiting and landed spacecraft, while most studies of terrestrial dust devils have involved manned monitoring of field sites, which can be costly both in time and personnel. As an alternative approach, we describe a multiyear in situ survey of terrestrial dust devils using pressure loggers deployed at El Dorado Playa in Nevada, USA, a site known for dust devil activity. Analogous to previous surveys for Martian dust devils, we conduct a posthoc analysis of the barometric data to search for putative dust devil pressure dips using a new automated detection algorithm. We investigate the completeness and false positive rates of our new algorithm and conduct several statistically robust analyses of the resulting population of dips. We also investigate possible seasonal, annual, and spatial variability of the putative dust devil dips, possible correlations with precipitation, and the influence of sample size on the derived population statistics. Our results suggest that large numbers of dips (>1000) collected over multiple seasons are probably required for accurate assessment of the underlying dust devil population. Correlating long-term barometric time series with other data streams (e.g., solar flux measurements from photovoltaic cells) can uniquely elucidate the natures and origins of dust devils, and accurately assessing their influence requires consideration of the full distribution of dust devil properties, rather than average values.

Ocean acidification alters the material properties of Mytilus edulis shells

PubMed Central

Fitzer, Susan C.; Zhu, Wenzhong; Tanner, K. Elizabeth; Phoenix, Vernon R.; Kamenos, Nicholas A.; Cusack, Maggie

2015-01-01

Ocean acidification (OA) and the resultant changing carbonate saturation states is threatening the formation of calcium carbonate shells and exoskeletons of marine organisms. The production of biominerals in such organisms relies on the availability of carbonate and the ability of the organism to biomineralize in changing environments. To understand how biomineralizers will respond to OA the common blue mussel, Mytilus edulis, was cultured at projected levels of pCO2 (380, 550, 750, 1000 µatm) and increased temperatures (ambient, ambient plus 2°C). Nanoindentation (a single mussel shell) and microhardness testing were used to assess the material properties of the shells. Young's modulus (E), hardness (H) and toughness (KIC) were measured in mussel shells grown in multiple stressor conditions. OA caused mussels to produce shell calcite that is stiffer (higher modulus of elasticity) and harder than shells grown in control conditions. The outer shell (calcite) is more brittle in OA conditions while the inner shell (aragonite) is softer and less stiff in shells grown under OA conditions. Combining increasing ocean pCO2 and temperatures as projected for future global ocean appears to reduce the impact of increasing pCO2 on the material properties of the mussel shell. OA may cause changes in shell material properties that could prove problematic under predation scenarios for the mussels; however, this may be partially mitigated by increasing temperature. PMID:25540244

The Contribution of Ionizing Stars to the Far-Infrared and Radio Emission in the Galaxy

NASA Astrophysics Data System (ADS)

Terebey, S.; Fich, M.; Taylor, R.

1999-12-01

A summary of research activities carried out in this eighth and final progress report. The final report includes: this summary document, copies of three published research papers, plus a draft manuscript of a fourth research paper entitled "The Contribution of Ionizing Stars to the FarInfrared and Radio Emission in the Milky Way; Evidence for a Swept-up Shell and Diffuse Ionized Halo around the W4 Chimney/Supershell." The main activity during the final quarterly reporting period was research on W4, including analysis of the radio and far-infrared images, generation of shell models, a literature search, and preparation of a research manuscript. There will be additional consultation with co-authors prior to submission of the paper to the Astrophysical Journal. The results will be presented at the 4th Tetons Summer Conference on "Galactic Structure, Stars, and the ISM" in May 2000. In this fourth and last paper we show W4 has a swept-up partially ionized shell of gas and dust which is powered by the OCl 352 star cluster. Analysis shows there is dense interstellar material directly below the shell, evidence that that the lower W4 shell "ran into a brick wall" and stalled, whereas the upper W4 shell achieved "breakout" to form a Galactic chimney. An ionized halo is evidence of Lyman continuum leakage which ionizes the WIM (warm ionized medium). It has long been postulated that the strong winds and abundant ionizing photons from massive stars are responsible for much of the large scale structure in the interstellar medium (ISM), including the ISM in other galaxies. However standard HII region theory predicts few photons will escape the local HII region. The significance of W4 and this work is it provides a direct example of how stellar winds power a galactic chimney, which in turn leads to a low density cavity from which ionizing photons can escape to large distances to ionize the WIM.

The Contribution of Ionizing Stars to the Far-Infrared and Radio Emission in the Galaxy

NASA Technical Reports Server (NTRS)

Terebey, S.; Fich, M.; Taylor, R.

1999-01-01

A summary of research activities carried out in this eighth and final progress report. The final report includes: this summary document, copies of three published research papers, plus a draft manuscript of a fourth research paper entitled "The Contribution of Ionizing Stars to the FarInfrared and Radio Emission in the Milky Way; Evidence for a Swept-up Shell and Diffuse Ionized Halo around the W4 Chimney/Supershell." The main activity during the final quarterly reporting period was research on W4, including analysis of the radio and far-infrared images, generation of shell models, a literature search, and preparation of a research manuscript. There will be additional consultation with co-authors prior to submission of the paper to the Astrophysical Journal. The results will be presented at the 4th Tetons Summer Conference on "Galactic Structure, Stars, and the ISM" in May 2000. In this fourth and last paper we show W4 has a swept-up partially ionized shell of gas and dust which is powered by the OCl 352 star cluster. Analysis shows there is dense interstellar material directly below the shell, evidence that that the lower W4 shell "ran into a brick wall" and stalled, whereas the upper W4 shell achieved "breakout" to form a Galactic chimney. An ionized halo is evidence of Lyman continuum leakage which ionizes the WIM (warm ionized medium). It has long been postulated that the strong winds and abundant ionizing photons from massive stars are responsible for much of the large scale structure in the interstellar medium (ISM), including the ISM in other galaxies. However standard HII region theory predicts few photons will escape the local HII region. The significance of W4 and this work is it provides a direct example of how stellar winds power a galactic chimney, which in turn leads to a low density cavity from which ionizing photons can escape to large distances to ionize the WIM.

IRC +10 216 in 3D: morphology of a TP-AGB star envelope

NASA Astrophysics Data System (ADS)

Guélin, M.; Patel, N. A.; Bremer, M.; Cernicharo, J.; Castro-Carrizo, A.; Pety, J.; Fonfría, J. P.; Agúndez, M.; Santander-García, M.; Quintana-Lacaci, G.; Velilla Prieto, L.; Blundell, R.; Thaddeus, P.

2018-02-01

During their late pulsating phase, AGB stars expel most of their mass in the form of massive dusty envelopes, an event that largely controls the composition of interstellar matter. The envelopes, however, are distant and opaque to visible and NIR radiation: their structure remains poorly known and the mass-loss process poorly understood. Millimeter-wave interferometry, which combines the advantages of longer wavelength, high angular resolution and very high spectral resolution is the optimal investigative tool for this purpose. Mm waves pass through dust with almost no attenuation. Their spectrum is rich in molecular lines and hosts the fundamental lines of the ubiquitous CO molecule, allowing a tomographic reconstruction of the envelope structure. The circumstellar envelope IRC +10 216 and its central star, the C-rich TP-AGB star closest to the Sun, are the best objects for such an investigation. Two years ago, we reported the first detailed study of the CO(2-1) line emission in that envelope, made with the IRAM 30-m telescope. It revealed a series of dense gas shells, expanding at a uniform radial velocity. The limited resolution of the telescope (HPBW 11″) did not allow us to resolve the shell structure. We now report much higher angular resolution observations of CO(2-1), CO(1-0), CN(2-1) and C4H(24-23) made with the SMA, PdB and ALMA interferometers (with synthesized half-power beamwidths of 3″, 1″ and 0.3″, respectively). Although the envelope appears much more intricate at high resolution than with an 11″ beam, its prevailing structure remains a pattern of thin, nearly concentric shells. The average separation between the brightest CO shells is 16″ in the outer envelope, where it appears remarkably constant. Closer to the star (<40″), the shell pattern is denser and less regular, showing intermediary arcs. Outside the small (r< 0.3'') dust formation zone, the gas appears to expand radially at a constant velocity, 14.5 km s-1, with small turbulent motions. Based on that property, we have reconstructed the 3D structure of the outer envelope and have derived the gas temperature and density radial profiles in the inner (r< 25'') envelope. The shell-intershell density contrast is found to be typically 3. The over-dense shells have spherical or slightly oblate shapes and typically extend over a few steradians, implying isotropic mass loss. The regular spacing of shells in the outer envelope supports the model of a binary star system with a period of 700 yr and a near face-on elliptical orbit. The companion fly-by triggers enhanced episodes of mass loss near periastron. The densification of the shell pattern observed in the central part of the envelope suggests a more complex scenario for the last few thousand years. This work was based on observations carried out with the IRAM, SMA and ALMA telescopes. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain). The Submillimeter Array is a joint project between the Smithsonian Astrophysical Observatory (USA) and the Academia Sinica Institute of Astronomy and Astrophysics (Taiwan) and is funded by the Smithsonian Institution and the Academia Sinica. This paper makes use of the ALMA data: ADS/JAO.ALMA#2013.1.01215.S & ADS/JAO.ALMA#2013.1.00432.S. ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada), NSC and ASIAA (Taiwan) and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ.

ALMA data suggest the presence of spiral structure in the inner wind of CW Leonis

NASA Astrophysics Data System (ADS)

Decin, L.; Richards, A. M. S.; Neufeld, D.; Steffen, W.; Melnick, G.; Lombaert, R.

2015-02-01

Context. Evolved low-mass stars lose a significant fraction of their mass through stellar winds. While the overall morphology of the stellar wind structure during the asymptotic giant branch (AGB) phase is thought to be roughly spherically symmetric, the morphology changes dramatically during the post-AGB and planetary nebula phase, during which bipolar and multi-polar structures are often observed. Aims: We aim to study the inner wind structure of the closest well-known AGB star CW Leo. Different diagnostics probing different geometrical scales have implied a non-homogeneous mass-loss process for this star: dust clumps are observed at milli-arcsec scale, a bipolar structure is seen at arcsecond-scale, and multi-concentric shells are detected beyond 1''. Methods: We present the first ALMA Cycle 0 band 9 data around 650 GHz (450 μm) tracing the inner wind of CW Leo. The full-resolution data have a spatial resolution of 0.̋42 × 0.̋24, allowing us to study the morpho-kinematical structure of CW Leo within ~6''. Results: We have detected 25 molecular emission lines in four spectral windows. The emission of all but one line is spatially resolved. The dust and molecular lines are centered around the continuum peak position, which is assumed to be dominated by stellar emission. The dust emission has an asymmetric distribution with a central peak flux density of ~2 Jy. The molecular emission lines trace different regions in the wind acceleration region and imply that the wind velocity increases rapidly from about 5 R⋆, almost reaching the terminal velocity at ~11 R⋆. The images prove that vibrational lines are excited close to the stellar surface and that SiO is a parent molecule. The channel maps for the brighter lines show a complex structure; specifically, for the 13CO J = 6-5 line, different arcs are detected within the first few arcseconds. The curved structure in the position-velocity (PV) map of the 13CO J = 6-5 line can be explained by a spiral structure in the inner wind of CW Leo, probably induced by a binary companion. From modelling the ALMA data, we deduce that the potential orbital axis for the binary system lies at a position angle of ~10-20° to the north-east and that the spiral structure is seen almost edge-on. We infer an orbital period of 55 yr and a binary separation of 25 au (or ~8.2 R⋆). We tentatively estimate that the companion is an unevolved low-mass main-sequence star. Conclusions: A scenario of a binary-induced spiral shell can explain the correlated structure seen in the ALMA PV images of CW Leo. Moreover, this scenario can also explain many other observational signatures seen at different spatial scales and in different wavelength regions, such as the bipolar structure and the almost concentric shells. ALMA data hence for the first time provide the crucial kinematical link between the dust clumps seen at milli-arcsecond scale and the almost concentric arcs seen at arcsecond scale. Appendix A is available in electronic form at http://www.aanda.org

Evidence for Reduced, Carbon-rich Regions in the Solar Nebula from an Unusual Cometary Dust Particle

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

De Gregorio, Bradley T.; Stroud, Rhonda M.; Nittler, Larry R.

Geochemical indicators in meteorites imply that most formed under relatively oxidizing conditions. However, some planetary materials, such as the enstatite chondrites, aubrite achondrites, and Mercury, were produced in reduced nebular environments. Because of large-scale radial nebular mixing, comets and other Kuiper Belt objects likely contain some primitive material related to these reduced planetary bodies. Here, we describe an unusual assemblage in a dust particle from comet 81P/Wild 2 captured in silica aerogel by the NASA Stardust spacecraft. The bulk of this ∼20 μ m particle is comprised of an aggregate of nanoparticulate Cr-rich magnetite, containing opaque sub-domains composed of poorlymore » graphitized carbon (PGC). The PGC forms conformal shells around tiny 5–15 nm core grains of Fe carbide. The C, N, and O isotopic compositions of these components are identical within errors to terrestrial standards, indicating a formation inside the solar system. Magnetite compositions are consistent with oxidation of reduced metal, similar to that seen in enstatite chondrites. Similarly, the core–shell structure of the carbide + PGC inclusions suggests a formation via FTT reactions on the surface of metal or carbide grains in warm, reduced regions of the solar nebula. Together, the nanoscale assemblage in the cometary particle is most consistent with the alteration of primary solids condensed from a C-rich, reduced nebular gas. The nanoparticulate components in the cometary particle provide the first direct evidence from comets of reduced, carbon-rich regions that were present in the solar nebula.« less

A Multi-Year Dust Devil Vortex Survey Using an Automated Search of Pressure Time-Series

NASA Astrophysics Data System (ADS)

Jackson, Brian K.; Lorenz, Ralph

2014-11-01

Dust devils occur in arid climates on the Earth and ubiquitously on Mars, where they likely dominate the supply of atmospheric dust and influence climate. Martian dust devils have been studied with a combination of orbiting and landed spacecraft, while most studies of terrestrial dust devils have involved manned monitoring of field sites, which can be costly both in time and personnel. As an alternative approach, we describe a multi-year in-situ survey of terrestrial dust devils using pressure loggers deployed at El Dorado Playa in Nevada, USA, a site known for dust devil activity. Analogous to previous surveys for Martian dust devils, we conduct a post-hoc analysis of the barometric data to search for putative dust devil pressure dips using a new automated detection algorithm. We investigate the completeness and false positive rates of our new algorithm and conduct several statistically robust analyses of the resulting population of dips. We also investigate seasonal, annual, and spatial variability of the putative dust devil dips, possible correlations with precipitation, and the influence of sample size on the derived population statistics. Our results suggest that large numbers of dips (> 1,000) collected over multiple seasons are probably required for accurate assessment of the underlying dust devil population. Correlating long-term barometric time-series with other data streams (e.g., solar flux measurements from photovoltaic cells) can uniquely elucidate the natures and origins of dust devils, and accurately assessing their influence requires consideration of the full distribution of dust devil properties, rather than average values. For example, our results suggest the dust flux from the average terrestrial devil is nearly 1,000 times smaller than the (more representative) population-weighted average flux. If applicable to Martian dust devils, such corrections may help resolve purported discrepancies between the dust fluxes estimated from dust devil studies and those required to maintain the atmospheric dust concentration.

Long-lived Dust Asymmetries at Dead Zone Edges in Protoplanetary Disks

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

Miranda, Ryan; Li, Hui; Li, Shengtai

A number of transition disks exhibit significant azimuthal asymmetries in thermal dust emission. One possible origin for these asymmetries is dust trapping in vortices formed at the edges of dead zones. We carry out high-resolution, two-dimensional hydrodynamic simulations of this scenario, including the effects of dust feedback. We find that, although feedback weakens the vortices and slows down the process of dust accumulation, the dust distribution in the disk can nonetheless remain asymmetric for many thousands of orbits. We show that even after 10{sup 4} orbits, or 2.5 Myr when scaled to the parameters of Oph IRS 48 (a significantmore » fraction of its age), the dust is not dispersed into an axisymmetric ring, in contrast to the case of a vortex formed by a planet. This is because accumulation of mass at the dead zone edge constantly replenishes the vortex, preventing it from being fully destroyed. We produce synthetic dust emission images using our simulation results. We find that multiple small clumps of dust may be distributed azimuthally. These clumps, if not resolved from one another, appear as a single large feature. A defining characteristic of a disk with a dead zone edge is that an asymmetric feature is accompanied by a ring of dust located about twice as far from the central star.« less

Photoexcitation Cascade and Quantum-Relativistic Jets in Graphene

NASA Astrophysics Data System (ADS)

Lewandowski, Cyprian; Levitov, L. S.

2018-02-01

In Dirac materials linear band dispersion blocks momentum-conserving interband transitions, creating a bottleneck for electron-hole pair production and carrier multiplication in the photoexcitation cascade. Here we show that the decays are unblocked and the bottleneck is relieved by subtle many-body effects involving multiple off-shell e -h pairs. The decays result from a collective behavior due to simultaneous emission of many soft pairs. We discuss characteristic signatures of the off-shell pathways, in particular the sharp angular distribution of secondary carriers, resembling relativistic jets in high-energy physics. The jets can be directly probed using solid-state equivalent of particle detectors. Collinear scattering enhances carrier multiplication, allowing for emission of as many as ˜10 secondary carriers per single absorbed photon.

A new look at dust and clouds in the Mars atmosphere - Analysis of emission-phase-function sequences from global Viking IRTM observations

NASA Technical Reports Server (NTRS)

Clancy, R. T.; Lee, Steven W.

1991-01-01

The present analysis of emission-phase function (EPF) observations from the IR thermal mapper aboard the Viking Orbiter encompasses polar latitudes, and Viking Lander sites, and spans a wide range of solar longitudes. A multiple scattering radiative transfer model which incorporates a bidirectional phase function for the surface and atmospheric scattering by dust and clouds yields surface albedos and dust and ice optical properties and optical depths for the variety of Mars conditions. It is possible to fit all analyzed EPF sequences corresponding to dust scattering with an albedo of 0.92, rather than the 0.86 given by Pollack et al. on the bases of Viking Lander observations.

Proteomic Characterization of the World Trade Center dust-activated mdig and c-myc signaling circuit linked to multiple myeloma

PubMed Central

Wu, Kai; Li, Lingzhi; Thakur, Chitra; Lu, Yongju; Zhang, Xiangmin; Yi, Zhengping; Chen, Fei

2016-01-01

Several epidemiological studies suggested an increased incidence rate of multiple myeloma (MM) among first responders and other individuals who exposed to World Trade Center (WTC) dust. In this report, we provided evidence showing that WTC dust is potent in inducing mdig protein and/or mRNA in bronchial epithelial cells, B cells and MM cell lines. An increased mdig expression in MM bone marrow was observed, which is associated with the disease progression and prognosis of the MM patients. Through integrative genomics and proteomics approaches, we further demonstrated that mdig directly interacts with c-myc and JAK1 in MM cell lines, which contributes to hyperactivation of the IL-6-JAK-STAT3 signaling important for the pathogenesis of MM. Genetic silencing of mdig reduced activity of the major downstream effectors in the IL-6-JAK-STAT3 pathway. Taken together, these data suggest that WTC dust may be one of the key etiological factors for those who had been exposed for the development of MM by activating mdig and c-myc signaling circuit linked to the IL-6-JAK-STAT3 pathway essential for the tumorigenesis of the malignant plasma cells. PMID:27833099

Airborne dust and soil particles at the Phoenix landing site, Mars

NASA Astrophysics Data System (ADS)

Madsen, M. B.; Drube, L.; Goetz, W.; Leer, K.; Falkenberg, T. V.; Gunnlaugsson, H. P.; Haspang, M. P.; Hviid, S. F.; Ellehøj, M. D.; Lemmon, M. T.

2009-04-01

The three iSweep targets on the Phoenix lander instrument deck utilize permanent magnets and 6 different background colors for studies of airborne dust [1]. The name iSweep is short for Improved Sweep Magnet experiments and derives from MER heritage [2, 3] as the rovers carried a sweep magnet, which is a very strong ring magnet built into an aluminum structure. Airborne dust is attracted and held by the magnet and the pattern formed depends on magnetic properties of the dust. The visible/near-infrared spectra acquired of the iSweep are rather similar to typical Martian dust and soil spectra. Because of the multiple background colors of the iSweeps the effect of the translucence of thin dust layers can be studied. This is used to estimate the rate of dust accumulation and will be used to evaluate light scattering properties of the particles. Some particles raised by the retro-rockets during the final descent came to rest on the lander deck and spectra of these particles are studied and compared with those of airborne dust and with spectra obtained from other missions. High resolution images acquired by the Optical Microscope (OM) [4] showed subtle differences between different Phoenix soil samples in terms of particle size and color. Most samples contain orange dust (particles smaller than 10 micrometer) as their major component and silt-sized (50-80 micrometer large) subrounded particles. Both particle types are substantially magnetic. Based on results from the Mars Exploration Rovers, the magnetization of the silt-sized particles is believed to be caused by magnetite. Morphology, texture and color of these particles (ranging from colorless, red-brown to almost black) suggest a multiple origin: The darkest particles probably represent lithic fragments, while the brighter ones could be impact or volcanic glasses. [1] Leer K. et al. (2008) JGR, 113, E00A16. [2] Madsen M.B. et al. (2003) JGR, 108, 8069. [3] Madsen M.B. et al. (2008) JGR (in print). [4] Hecht M.H. et al. (2008) JGR, 113, E00A22.

VizieR Online Data Catalog: GRAMS carbon-star model grid (Srinivasan+, 2011)

NASA Astrophysics Data System (ADS)

Srinivasan, S.; Sargent, B. A.; Meixner, M.

2011-07-01

Synthetic spectra and photometry for the GRAMS carbon-star set of radiative transfer models is provided in FITS form. Also included are various stellar and dust shell parameters related to the models. For each model, a 130-wavelength spectrum for the bare photosphere and one for the star+dust spectrum are available. The fluxes are in F_nu (Jansky) and are computed at the LMC distance (distance modulus = 18.5mag). Synthetic photometry is computed for 34 narrow- and broad-band filters which, in order, are: U, B, V, I, J, H, Ks, IRAC36, IRAC45, IRAC5_8, IRAC8_0, MIPS24, MIPS70, MIPS160, AKARIN2, AKARIN3, AKARIN4, AKARIS7, AKARIS9W, AKARIS11, AKARIL15, AKARIL18W, AKARIL24, WISEW1, WISEW2, WISEW3 and WISEW4 (see the footnotes in the article for more about these filters). Please read the FITS header for more information on the data. (2 data files).

Retrospective environmental biomonitoring - Mussel Watch expanded

NASA Astrophysics Data System (ADS)

Schöne, Bernd R.; Krause, Richard A.

2016-09-01

Monitoring bioavailable contaminants and determining baseline conditions in aquatic environments has become an important aspect of ecology and ecotoxicology. Since the mid-1970s and the initiation of the Mussel Watch program, this has been successfully accomplished with bivalve mollusks. These (mostly) sessile organisms reliably and proportionately record changes of a range of organic and inorganic pollutants occurring in the water, food or sediment. The great majority of studies have measured the concentration of pollutants in soft tissues and, to a much lesser extent, in whole shells or fractions thereof. Both approaches come with several drawbacks. Neither soft tissues nor whole shells can resolve temporal changes of the pollution history, except through the analysis of multiple specimens collected at different times. Soft tissues and shell fractions provide time-averaged data spanning months or years, and whole shells time-averaged data over the entire lifespan of the animal. Even with regular sampling of multiple specimens over long intervals of time, the resulting chronology may not faithfully resolve short-term changes of water quality. Compounding the problem, whole shell averages tend to be non-arithmetic and non-linear, because shell growth rate varies through seasons and lifetime, and different shell layers often vary ultrastructurally and can thus be chemically different from each other. Mussel Watch could greatly benefit from the potential of bivalve shells in providing high-resolution, temporally aligned archives of environmental variability. So far, only circa a dozen studies have demonstrated that the sclerochronological approach - i.e., combined growth pattern and high-resolution chemical analyses - can provide sub-seasonally to annually resolved time-series documenting the history of pollution over centuries and even millennia. On the other hand, the sclerochronological community has failed to fully appreciate that the formation of the shell and its chemical composition is controlled by the soft parts and that a robust interpretation of the shell record requires a detailed understanding of bivalve physiology, behavior and ecology. This review attempts to bring together the Mussel Watch and sclerochronology communities and lay the foundation of a new subdiscipline of the Mussel Watch: retrospective environmental biomonitoring. For this purpose, we provide an overview of seminal work from both fields and outline potential future research directions.

A detailed view of the gas shell around R Sculptoris with ALMA

NASA Astrophysics Data System (ADS)

Maercker, M.; Vlemmings, W. H. T.; Brunner, M.; De Beck, E.; Humphreys, E. M.; Kerschbaum, F.; Lindqvist, M.; Olofsson, H.; Ramstedt, S.

2016-02-01

Context. During the asymptotic giant branch (AGB) phase, stars undergo thermal pulses - short-lived phases of explosive helium burning in a shell around the stellar core. Thermal pulses lead to the formation and mixing-up of new elements to the stellar surface. They are hence fundamental to the chemical evolution of the star and its circumstellar envelope. A further consequence of thermal pulses is the formation of detached shells of gas and dust around the star, several of which have been observed around carbon-rich AGB stars. Aims: We aim to determine the physical properties of the detached gas shell around R Sculptoris, in particular the shell mass and temperature, and to constrain the evolution of the mass-loss rate during and after a thermal pulse. Methods: We analyse 12CO(1-0), 12CO(2-1), and 12CO(3-2) emission, observed with the Atacama Large Millimeter/submillimeter Array (ALMA) during Cycle 0 and complemented by single-dish observations. The spatial resolution of the ALMA data allows us to separate the detached shell emission from the extended emission inside the shell. We perform radiative transfer modelling of both components to determine the shell properties and the post-pulse mass-loss properties. Results: The ALMA data show a gas shell with a radius of 19.̋5 expanding at 14.3 km s-1. The different scales probed by the ALMA Cycle 0 array show that the shell must be entirely filled with gas, contrary to the idea of a detached shell. The comparison to single-dish spectra and radiative transfer modelling confirms this. We derive a shell mass of 4.5 × 10-3 M⊙ with a temperature of 50 K. Typical timescales for thermal pulses imply a pulse mass-loss rate of 2.3 × 10-5 M⊙ yr-1. For the post-pulse mass-loss rate, we find evidence for a gradual decline of the mass-loss rate, with an average value of 1.6 × 10-5 M⊙ yr-1. The total amount of mass lost since the last thermal pulse is 0.03 M⊙, a factor four higher compared to classical models, with a sharp decline in mass-loss rate immediately after the pulse. Conclusions: We find that the mass-loss rate after a thermal pulse has to decline more slowly than generally expected from models of thermal pulses. This may cause the star to lose significantly more mass during a thermal pulse cycle, which affects the lifetime on the AGB and the chemical evolution of the star, its circumstellar envelope, and the interstellar medium.

Temporal characteristics of electrostatic surface waves in a cold complex plasma containing collision-dominated ion flow

NASA Astrophysics Data System (ADS)

Lee, Myoung-Jae; Jung, Young-Dae

2017-03-01

The influence of electron-ion collision frequency and dust charge on the growth rate of two-stream instability of the electrostatic surface wave propagating at the interface of semi-infinite complex plasma whose constituents are electrons, negatively charged dust, and streaming ions. It is found that the surface wave can be unstable if the multiplication of wave number and ion flow velocity is greater than the total plasma frequency of electrons and dusts. The analytical solution of the growth rate is derived as a function of collision frequency, dust charge, and ion-to-electron density ratio. It is found that the growth rate is inversely proportional to the collision rate, but it is enhanced as the number of electrons residing on the dust grain surface is increased. The growth rate of surface wave is compared to that of the bulk wave.

Innovative space x-ray telescopes

NASA Astrophysics Data System (ADS)

Hudec, R.; Inneman, A.; Pina, L.; Sveda, L.; Ticha, H.; Brozek, V.

2017-11-01

We report on the progress in innovative X-ray mirror development with focus on requirements of future X-ray astronomy space projects. Various future projects in X-ray astronomy and astrophysics will require large lightweight but highly accurate segments with multiple thin shells or foils. The large Wolter 1 grazing incidence multiple mirror arrays, the Kirkpatrick-Baez modules, as well as the large Lobster-Eye X-ray telescope modules in Schmidt arrangement may serve as examples. All these space projects will require high quality and light segmented shells (shaped, bent or flat foils) with high X-ray reflectivity and excellent mechanical stability.

A facile single-step synthesis of ternary multicore magneto-plasmonic nanoparticles.

PubMed

Benelmekki, Maria; Bohra, Murtaza; Kim, Jeong-Hwan; Diaz, Rosa E; Vernieres, Jerome; Grammatikopoulos, Panagiotis; Sowwan, Mukhles

2014-04-07

We report a facile single-step synthesis of ternary hybrid nanoparticles (NPs) composed of multiple dumbbell-like iron-silver (FeAg) cores encapsulated by a silicon (Si) shell using a versatile co-sputter gas-condensation technique. In comparison to previously reported binary magneto-plasmonic NPs, the advantage conferred by a Si shell is to bind the multiple magneto-plasmonic (FeAg) cores together and prevent them from aggregation at the same time. Further, we demonstrate that the size of the NPs and number of cores in each NP can be modulated over a wide range by tuning the experimental parameters.

Applications of Electrified Dust and Dust Devil Electrodynamics to Martian Atmospheric Electricity

NASA Astrophysics Data System (ADS)

Harrison, R. G.; Barth, E.; Esposito, F.; Merrison, J.; Montmessin, F.; Aplin, K. L.; Borlina, C.; Berthelier, J. J.; Déprez, G.; Farrell, W. M.; Houghton, I. M. P.; Renno, N. O.; Nicoll, K. A.; Tripathi, S. N.; Zimmerman, M.

2016-11-01

Atmospheric transport and suspension of dust frequently brings electrification, which may be substantial. Electric fields of 10 kV m-1 to 100 kV m-1 have been observed at the surface beneath suspended dust in the terrestrial atmosphere, and some electrification has been observed to persist in dust at levels to 5 km, as well as in volcanic plumes. The interaction between individual particles which causes the electrification is incompletely understood, and multiple processes are thought to be acting. A variation in particle charge with particle size, and the effect of gravitational separation explains to, some extent, the charge structures observed in terrestrial dust storms. More extensive flow-based modelling demonstrates that bulk electric fields in excess of 10 kV m-1 can be obtained rapidly (in less than 10 s) from rotating dust systems (dust devils) and that terrestrial breakdown fields can be obtained. Modelled profiles of electrical conductivity in the Martian atmosphere suggest the possibility of dust electrification, and dust devils have been suggested as a mechanism of charge separation able to maintain current flow between one region of the atmosphere and another, through a global circuit. Fundamental new understanding of Martian atmospheric electricity will result from the ExoMars mission, which carries the DREAMS (Dust characterization, Risk Assessment, and Environment Analyser on the Martian Surface)—MicroARES ( Atmospheric Radiation and Electricity Sensor) instrumentation to Mars in 2016 for the first in situ electrical measurements.

Applications of Electrified Dust and Dust Devil Electrodynamics to Martian Atmospheric Electricity

NASA Technical Reports Server (NTRS)

Harrison, R. G.; Barth, E.; Esposito, F.; Merrison, J.; Montmessin, F.; Aplin, K. L.; Borlina, C.; Berthelier, J J.; Deprez, G.; Farrell, William M.;

Forecast errors in dust vertical distributions over Rome (Italy): Multiple particle size representation and cloud contributions

NASA Astrophysics Data System (ADS)

Kishcha, P.; Alpert, P.; Shtivelman, A.; Krichak, S. O.; Joseph, J. H.; Kallos, G.; Katsafados, P.; Spyrou, C.; Gobbi, G. P.; Barnaba, F.; Nickovic, S.; PéRez, C.; Baldasano, J. M.

2007-08-01

In this study, forecast errors in dust vertical distributions were analyzed. This was carried out by using quantitative comparisons between dust vertical profiles retrieved from lidar measurements over Rome, Italy, performed from 2001 to 2003, and those predicted by models. Three models were used: the four-particle-size Dust Regional Atmospheric Model (DREAM), the older one-particle-size version of the SKIRON model from the University of Athens (UOA), and the pre-2006 one-particle-size Tel Aviv University (TAU) model. SKIRON and DREAM are initialized on a daily basis using the dust concentration from the previous forecast cycle, while the TAU model initialization is based on the Total Ozone Mapping Spectrometer aerosol index (TOMS AI). The quantitative comparison shows that (1) the use of four-particle-size bins in the dust modeling instead of only one-particle-size bins improves dust forecasts; (2) cloud presence could contribute to noticeable dust forecast errors in SKIRON and DREAM; and (3) as far as the TAU model is concerned, its forecast errors were mainly caused by technical problems with TOMS measurements from the Earth Probe satellite. As a result, dust forecast errors in the TAU model could be significant even under cloudless conditions. The DREAM versus lidar quantitative comparisons at different altitudes show that the model predictions are more accurate in the middle part of dust layers than in the top and bottom parts of dust layers.

Multiple piece turbine airfoil

DOEpatents

Kimmel, Keith D

2010-11-09

A turbine airfoil, such as a rotor blade or a stator vane, for a gas turbine engine, the airfoil formed as a shell and spar construction with a plurality of hook shaped struts each mounted within channels extending in a spanwise direction of the spar and the shell to allow for relative motion between the spar and shell in the airfoil chordwise direction while also fanning a seal between adjacent cooling channels. The struts provide the seal as well as prevent bulging of the shell from the spar due to the cooling air pressure. The hook struts have a hooked shaped end and a rounded shaped end in order to insert the struts into the spar.

Nevirapine Loaded Core Shell Gold Nanoparticles by Double Emulsion Solvent Evaporation: In vitro and In vivo Evaluation.

PubMed

Dalvi, Bhagyashree R; Siddiqui, Ejaz A; Syed, Asad S; Velhal, Shilpa M; Ahmad, Absar; Bandivdekar, Atmaram B; Devarajan, Padma V

2016-01-01

HIV/AIDS is a macrophage resident infection localized in the reticuloendothelial system and remote locations of brain and bone marrow. We present core shell nanoparticles of gold(AuNPs) and nevirapine(NVP) for targeted delivery to the multiple HIV reservoirs. The aim of the study was to design core shell NVP loaded AuNPs with high drug loading and to evaluate biodistribution of the nanoparticles in possible HIV reservoirs in vivo. A specific objective was to assess the possible synergy of AuNPs with NVP on anti-HIV activity in vitro. Core shell nanoparticles were prepared by double emulsion solvent evaporation method and characterized. Glyceryl monostearate-nevirapine-gold nanoparticles(GMS-NVP-AuNPs) revealed high entrapment efficiency (>70%), high loading (~40%), particle size <250 nm and zeta potential -35.9± 1.41mv and exhibited sustained release with good stability. Surface plasmon resonance indicated shell formation while SEM coupled EDAX confirmed the presence of Au. TEM confirmed formation of spherical core shell nanoparticles. GMS-NVP-AuNPs revealed low hemolysis (<10 %) and serum stability upto 6 h. GMS-NVP-AuNPs exhibited rapid, high and sustained accumulation in the possible HIV reservoir organs, including the major organs of liver, spleen, lymph nodes, thymus and also remote locations of brain, ovary and bone marrow. High cell viability and enhanced uptake in PBMC's and TZM-bl cells were observed. While uptake in PBMC's proposed monocytes/macrophages enabled brain delivery. GMS-NVP-AuNPs demonstrated synergistic anti-HIV activity. The superior anti-HIV activity in vitro coupled with extensive localization of the nanoparticles in multiple HIV reservoirs suggests great promise of the core shell GMS-NVP-AuNPs for improved therapy of HIV.

Design and intestinal mucus penetration mechanism of core-shell nanocomplex.

PubMed

Zhang, Xin; Cheng, Hongbo; Dong, Wei; Zhang, Meixia; Liu, Qiaoyu; Wang, Xiuhua; Guan, Jian; Wu, Haiyang; Mao, Shirui

2018-02-28

The objective of this study was to design intestinal mucus-penetrating core-shell nanocomplex by functionally mimicking the surface of virus, which can be used as the carrier for peroral delivery of macromolecules, and further understand the influence of nanocomplex surface properties on the mucosal permeation capacity. Taking insulin as a model drug, the core was formed by the self-assembly among positively charged chitosan, insulin and negatively charged sodium tripolyphosphate, different types of alginates were used as the shell forming material. The nanocomplex was characterized by dynamic light scattering (DLS), atomic force microscopy (AFM) and FTIR. Nanocomplex movement in mucus was recorded using multiple particle tracking (MPT) method. Permeation and uptake of different nanocomplex were studied in rat intestine. It was demonstrated that alginate coating layer was successfully formed on the core and the core-shell nanocomplex showed a good physical stability and improved enzymatic degradation protection. The mucus penetration and MPT study showed that the mucus penetration capacity of the nanocomplex was surface charge and coating polymer structure dependent, nanocomplex with negative alginate coating had 1.6-2.5 times higher mucus penetration ability than that of positively charged chitosan-insulin nanocomplex. Moreover, the mucus penetration ability of the core-shell nanocomplex was alginate structure dependent, whereas alginate with lower G content and lower molecular weight showed the best permeation enhancing ability. The improvement of intestine permeation and intestinal villi uptake of the core-shell nanocomplex were further confirmed in rat intestine and multiple uptake mechanisms were involved in the transport process. In conclusion, core-shell nanocomplex composed of oppositely charged materials could provide a strategy to overcome the mucus barrier and enhance the mucosal permeability. Copyright © 2018 Elsevier B.V. All rights reserved.

Multiscale structure and damage tolerance of coconut shells.

PubMed

Gludovatz, B; Walsh, F; Zimmermann, E A; Naleway, S E; Ritchie, R O; Kruzic, J J

2017-12-01

We investigated the endocarp of the fruit of Cocos nucifera (i.e., the inner coconut shell), examining the structure across multiple length scales through advanced characterization techniques and in situ testing of mechanical properties. Like many biological materials, the coconut shell possesses a hierarchical structure with distinct features at different length scales that depend on orientation and age. Aged coconut was found to have a significantly stronger (ultimate tensile strength, UTS = 48.5MPa), stiffer (Young's modulus, E = 1.92GPa), and tougher (fracture resistance (R-curve) peak of K J = 3.2MPa m 1/2 ) endocarp than the younger fruit for loading in the latitudinal orientation. While the mechanical properties of coconut shell were observed to improve with age, they also become more anisotropic: the young coconut shell had the same strength (17MPa) and modulus (0.64GPa) values and similar R-curves for both longitudinal and latitudinal loading configurations, whereas the old coconut had 82% higher strength for loading in the latitudinal orientation, and >50% higher crack growth toughness for cracking on the latitudinal plane. Structural aspects affecting the mechanical properties across multiple length scales with aging were identified as improved load transfer to the cellulose crystalline nanostructure (identified by synchrotron x-ray diffraction) and sclerification of the endocarp, the latter of which included closing of the cell lumens and lignification of the cell walls. The structural changes gave a denser and mechanically superior micro and nanostructure to the old coconut shell. Additionally, the development of anisotropy was attributed to the formation of an anisotropic open channel structure throughout the shell of the old coconut that affected both crack initiation during uniaxial tensile tests and the toughening mechanisms of crack trapping and deflection during crack propagation. Copyright © 2017 Elsevier Ltd. All rights reserved.

Density profile of strongly correlated spherical Yukawa plasmas

NASA Astrophysics Data System (ADS)

Bonitz, M.; Henning, C.; Ludwig, P.; Golubnychiy, V.; Baumgartner, H.; Piel, A.; Block, D.

2006-10-01

Recently the discovery of 3D-dust crystals [1] excited intensive experimental and theoretical activities [2-4]. Details of the shell structure of these crystals has been very well explained theoretically by a simple model involving an isotropic Yukawa-type pair repulsion and an external harmonic confinement potential [4]. On the other hand, it has remained an open question how the average radial density profile, looks like. We show that screening has a dramatic effect on the density profile, which we derive analytically for the ground state. Interestingly, the result applies not only to a continuous plasma distribution but also to simulation data for the Coulomb crystals exhibiting the above mentioned shell structure. Furthermore, excellent agreement between the continuum model and shell models is found [5]. [1] O. Arp, D. Block, A. Piel, and A. Melzer, Phys. Rev. Lett. 93, 165004 (2004). [2] H. Totsuji, C. Totsuji, T. Ogawa, and K. Tsuruta, Phys. Rev. E 71, 045401 (2005) [3] P. Ludwig, S. Kosse, and M. Bonitz, Phys. Rev. E 71, 046403 (2005) [4] M. Bonitz, D. Block, O. Arp, V. Golubnychiy, H. Baumgartner, P. Ludwig, A. Piel, and A. Filinov, Phys. Rev. Lett. 96, 075001 (2006) [5] C. Henning, M. Bonitz, A. Piel, P. Ludwig, H. Baumgartner, V. Golubnichiy, and D. Block, submitted to Phys. Rev. E

The Expanding Bipolar Shell of the Helium Nova V445 Puppis

NASA Astrophysics Data System (ADS)

Woudt, P. A.; Steeghs, D.; Karovska, M.; Warner, B.; Groot, P. J.; Nelemans, G.; Roelofs, G. H. A.; Marsh, T. R.; Nagayama, T.; Smits, D. P.; O'Brien, T.

2009-11-01

From multi-epoch adaptive optics imaging and integral field unit spectroscopy, we report the discovery of an expanding and narrowly confined bipolar shell surrounding the helium nova V445 Puppis (Nova Puppis 2000). An equatorial dust disc obscures the nova remnant, and the outflow is characterized by a large polar outflow velocity of 6720 ± 650 km s-1 and knots moving at even larger velocities of 8450 ± 570 km s-1. We derive an expansion parallax distance of 8.2 ± 0.5 kpc and deduce a pre-outburst luminosity of the underlying binary of log L/L sun = 4.34 ± 0.36. The derived luminosity suggests that V445 Puppis probably contains a massive white dwarf accreting at high rate from a helium star companion making it part of a population of binary stars that potentially lead to supernova Ia explosions due to accumulation of helium-rich material on the surface of a massive white dwarf.

K-shell Photoabsorption of Oxygen Ions

NASA Technical Reports Server (NTRS)

Garcia, J.; Mendoza, C.; Bautista, M. A.; Gorczyca, T. W.; Kallman, T. R.; Palmeri, P.

2005-01-01

The high spectral resolutions of the Chandra and XMM-Newton X-ray observatories have unveiled the useful diagnostic possibilities of oxygen K absorption. To mention a few, strong O VII and O VIII edges are almost ubiquitous in the spectra of Seyfert 1 galaxies which have been used by Lee et al. (2001) to predict of a warm dust absorber along the line of sight; although this conclusion has been criticized in the light of a data reanalysis (SA0 et al. 2003), Steenbrugge et al. (2003) have detected inner-shell transitions of O III-O VI in the spectrum of NGC 5548 that point to a warm absorber that spans three orders of magnitude in ionization parameter. Moreover, Behar et al. (2003) have stressed that, in the case of both Seyfert 1 and Seyfert 2 galaxies, a broad range of oxygen charge states are usually observed along the line of sight that must be fitted simultaneously, and may imply strong density gradients of 2-4 orders of magnitude over short distances.

Genesis Spacecraft Science Canister Preliminary Inspection and Cleaning

NASA Technical Reports Server (NTRS)

Hittle, J. D.; Calaway, M. J.; Allton, J. H.; Warren, J. L.; Schwartz, C. M.; Stansbery, E. K.

2006-01-01

The Genesis science canister is an aluminum cylinder (75 cm diameter and 35 cm tall) hinged at the mid-line for opening. This canister was cleaned and assembled in an ISO level 4 (Class 10) clean room at Johnson Space Center (JSC) prior to launch. The clean solar collectors were installed and the canister closed in the cleanroom to preserve collector cleanliness. The canister remained closed until opened on station at Earth-Sun L1 for solar wind collection. At the conclusion of collection, the canister was again closed to preserve collector cleanliness during Earth return and re-entry. Upon impacting the dry Utah lakebed at 300 kph the science canister integrity was breached. The canister was returned to JSC. The canister shell was briefly examined, imaged, gently cleaned of dust and packaged for storage in anticipation of future detailed examination. The condition of the science canister shell noted during this brief examination is presented here. The canister interior components were packaged and stored without imaging due to time constraints.

A Multi-Wavelength Survey of Intermediate-Mass Star-Forming Regions

NASA Astrophysics Data System (ADS)

Lundquist, Michael J.; Kobulnicky, Henry A.; Kerton, Charles R.

2015-01-01

Current research into Galactic star formation has focused on either massive star-forming regions or nearby low-mass regions. We present results from a survey of Galactic intermediate-mass star-forming regions (IM SFRs). These regions were selected from IRAS colors that specify cool dust and large PAH contribution, suggesting that they produce stars up to but not exceeding about 8 solar masses. Using WISE data we have classified 984 candidate IM SFRs as star-like objects, galaxies, filamentary structures, or blobs/shells based on their mid-infrared morphologies. Focusing on the blobs/shells, we combined follow-up observations of deep near-infrared (NIR) imaging with optical and NIR spectroscopy to study the stellar content, confirming the intermediate-mass nature of these regions. We also gathered CO data from OSO and APEX to study the molecular content and dynamics of these regions. We compare these results to those of high-mass star formation in order to better understand their role in the star-formation paradigm.

From Lobster Shells to Plastic Objects: A Bioplastics Activity

ERIC Educational Resources Information Center

Hudson, Reuben; Glaisher, Samuel; Bishop, Alexandra; Katz, Jeffrey L.

2015-01-01

A multiple day activity for students to create large-scale plastic objects from the biopolymer chitin (major component of lobster, crab, and shrimp shells) is described. The plastic objects created are durable and made from benign materials, making them suitable for students to take home to play with. Since the student-created plastic objects are…

Aethalometer multiple scattering correction Cref for mineral dust aerosols

NASA Astrophysics Data System (ADS)

Di Biagio, Claudia; Formenti, Paola; Cazaunau, Mathieu; Pangui, Edouard; Marchand, Nicolas; Doussin, Jean-François

2017-08-01

In this study we provide a first estimate of the Aethalometer multiple scattering correction Cref for mineral dust aerosols. Cref is an empirical constant used to correct the aerosol absorption coefficient measurements for the multiple scattering artefact of the Aethalometer; i.e. the filter fibres on which aerosols are deposited scatter light and this is miscounted as absorption. The Cref at 450 and 660 nm was obtained from the direct comparison of Aethalometer data (Magee Sci. AE31) with (i) the absorption coefficient calculated as the difference between the extinction and scattering coefficients measured by a Cavity Attenuated Phase Shift Extinction analyser (CAPS PMex) and a nephelometer respectively at 450 nm and (ii) the absorption coefficient from a MAAP (Multi-Angle Absorption Photometer) at 660 nm. Measurements were performed on seven dust aerosol samples generated in the laboratory by the mechanical shaking of natural parent soils issued from different source regions worldwide. The single scattering albedo (SSA) at 450 and 660 nm and the size distribution of the aerosols were also measured. Cref for mineral dust varies between 1.81 and 2.56 for a SSA of 0.85-0.96 at 450 nm and between 1.75 and 2.28 for a SSA of 0.98-0.99 at 660 nm. The calculated mean for dust is 2.09 (±0.22) at 450 nm and 1.92 (±0.17) at 660 nm. With this new Cref the dust absorption coefficient by the Aethalometer is about 2 % (450 nm) and 11 % (660 nm) higher than that obtained by using Cref = 2.14 at both 450 and 660 nm, as usually assumed in the literature. This difference induces a change of up to 3 % in the dust SSA at 660 nm. The Cref seems to be independent of the fine and coarse particle size fractions, and so the obtained Cref can be applied to dust both close to sources and following transport. Additional experiments performed with pure kaolinite minerals and polluted ambient aerosols indicate Cref of 2.49 (±0.02) and 2.32 (±0.01) at 450 and 660 nm (SSA = 0.96-0.97) for kaolinite, and Cref of 2.32 (±0.36) at 450 nm and 2.32 (±0.35) at 660 nm for pollution aerosols (SSA = 0.62-0.87 at 450 nm and 0.42-0.76 at 660 nm).

Observation of Dust Stream Formation Produced by Low Current, High Voltage Cathode Spots

NASA Technical Reports Server (NTRS)

Foster, John E.

2004-01-01

Macro-particle acceleration driven by low current, high voltage cathode spots has been investigated. The phenomenon was observed to occur when nanometer and micrometer-sized particles in the presence of a discharge plasma were exposed to a high voltage pulse. The negative voltage pulse initiates the formation of multiple, high voltage, low current cathode spots which provides the mechanism of actual acceleration of the charged dust particles. Dust streams generated by this process were detected using laser scattering techniques. The particle impact craters observed at the surface of downstream witness badges were documented using SEM and light microscopy.

Architected Lattices with High Stiffness and Toughness via Multicore-Shell 3D Printing.

PubMed

Mueller, Jochen; Raney, Jordan R; Shea, Kristina; Lewis, Jennifer A

2018-03-01

The ability to create architected materials that possess both high stiffness and toughness remains an elusive goal, since these properties are often mutually exclusive. Natural materials, such as bone, overcome such limitations by combining different toughening mechanisms across multiple length scales. Here, a new method for creating architected lattices composed of core-shell struts that are both stiff and tough is reported. Specifically, these lattices contain orthotropic struts with flexible epoxy core-brittle epoxy shell motifs in the absence and presence of an elastomeric silicone interfacial layer, which are fabricated by a multicore-shell, 3D printing technique. It is found that architected lattices produced with a flexible core-elastomeric interface-brittle shell motif exhibit both high stiffness and toughness. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

WHAT DOES A SUBMILLIMETER GALAXY SELECTION ACTUALLY SELECT? THE DEPENDENCE OF SUBMILLIMETER FLUX DENSITY ON STAR FORMATION RATE AND DUST MASS

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

Hayward, Christopher C.; Keres, Dusan; Jonsson, Patrik

2011-12-20

We perform three-dimensional dust radiative transfer (RT) calculations on hydrodynamic simulations of isolated and merging disk galaxies in order to quantitatively study the dependence of observed-frame submillimeter (submm) flux density on galaxy properties. We find that submm flux density and star formation rate (SFR) are related in dramatically different ways for quiescently star-forming galaxies and starbursts. Because the stars formed in the merger-induced starburst do not dominate the bolometric luminosity and the rapid drop in dust mass and more compact geometry cause a sharp increase in dust temperature during the burst, starbursts are very inefficient at boosting submm flux densitymore » (e.g., a {approx}> 16 Multiplication-Sign boost in SFR yields a {approx}< 2 Multiplication-Sign boost in submm flux density). Moreover, the ratio of submm flux density to SFR differs significantly between the two modes; thus one cannot assume that the galaxies with highest submm flux density are necessarily those with the highest bolometric luminosity or SFR. These results have important consequences for the bright submillimeter-selected galaxy (SMG) population. Among them are: (1) The SMG population is heterogeneous. In addition to merger-driven starbursts, there is a subpopulation of galaxy pairs, where two disks undergoing a major merger but not yet strongly interacting are blended into one submm source because of the large ({approx}> 15'' or {approx}130 kpc at z = 2) beam of single-dish submm telescopes. (2) SMGs must be very massive (M{sub *} {approx}> 6 Multiplication-Sign 10{sup 10} M{sub Sun }). (3) The infall phase makes the SMG duty cycle a factor of a few greater than what is expected for a merger-driven starburst. Finally, we provide fitting functions for SCUBA and AzTEC submm flux densities as a function of SFR and dust mass and bolometric luminosity and dust mass; these should be useful for calculating submm flux density in semi-analytic models and cosmological simulations when performing full RT is computationally not feasible.« less

FAR-ULTRAVIOLET OBSERVATIONS OF THE SPICA NEBULA AND THE INTERACTION ZONE

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

Choi, Yeon-Ju; Min, Kyoung-Wook; Lim, Tae-Ho

2013-09-01

We report the analysis results of far-ultraviolet (FUV) observations, made for a broad region around {alpha} Vir (Spica) including the interaction zone of Loop I and the Local Bubble. The whole region was optically thin and a general correlation was seen between the FUV continuum intensity and the dust extinction, except in the neighborhood of the bright central star, indicating the dust scattering nature of the FUV continuum. We performed Monte Carlo radiative transfer simulations to obtain the optical parameters related to the dust scattering as well as to the geometrical structure of the region. The albedo and asymmetry factormore » were found to be 0.38 {+-} 0.06 and 0.46 {+-} 0.06, respectively, in good agreement with the Milky Way dust grain models. The distance to and the thickness of the interaction zone were estimated to be 70{sup +4}{sub -8} pc and 40{sup +8}{sub -10} pc, respectively. The diffuse FUV continuum in the northern region above Spica was mostly the result of scattering of the starlight from Spica, while that in the southern region was mainly due to the background stars. The C IV {lambda}{lambda}1548, 1551 emission was found throughout the whole region, in contrast to the Si II* {lambda}1532 emission which was bright only within the H II region. This indicates that the C IV line arises mostly at the shell boundaries of the bubbles, with a larger portion likely from the Loop I than from the Local Bubble side, whereas the Si II* line is from the photoionized Spica Nebula.« less

Mid-Infrared Interferometric Monitoring of Evolved Stars: The Dust Shell Around the Mira Variable RR Aquilae at 13 Epochs

DTIC Science & Technology

2011-01-01

photometric and interferometric data. 15. SUBJECT TERMS 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT Same as Report (SAR) 18. NUMBER OF...λ = 2.2 μm, Δλ = 0.4 μm) angular size with the Infrared Optical Telescope Array ( IOTA ). The uniform disk diameter (UD) of θUD = 10.73 ± 0.66 mas at...with IOTA in the H-band, and classified RR Aql as a target with no detectable asymmetries. The IRAS flux at 12 μm is 332 Jy. The light curve in the V

Ocean acidification alters the material properties of Mytilus edulis shells.

PubMed

Fitzer, Susan C; Zhu, Wenzhong; Tanner, K Elizabeth; Phoenix, Vernon R; Kamenos, Nicholas A; Cusack, Maggie

2015-02-06

Ocean acidification (OA) and the resultant changing carbonate saturation states is threatening the formation of calcium carbonate shells and exoskeletons of marine organisms. The production of biominerals in such organisms relies on the availability of carbonate and the ability of the organism to biomineralize in changing environments. To understand how biomineralizers will respond to OA the common blue mussel, Mytilus edulis, was cultured at projected levels of pCO2 (380, 550, 750, 1000 µatm) and increased temperatures (ambient, ambient plus 2°C). Nanoindentation (a single mussel shell) and microhardness testing were used to assess the material properties of the shells. Young's modulus (E), hardness (H) and toughness (KIC) were measured in mussel shells grown in multiple stressor conditions. OA caused mussels to produce shell calcite that is stiffer (higher modulus of elasticity) and harder than shells grown in control conditions. The outer shell (calcite) is more brittle in OA conditions while the inner shell (aragonite) is softer and less stiff in shells grown under OA conditions. Combining increasing ocean pCO2 and temperatures as projected for future global ocean appears to reduce the impact of increasing pCO2 on the material properties of the mussel shell. OA may cause changes in shell material properties that could prove problematic under predation scenarios for the mussels; however, this may be partially mitigated by increasing temperature. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

Dust reddening and extinction curves toward gamma-ray bursts at z > 4

NASA Astrophysics Data System (ADS)

Bolmer, J.; Greiner, J.; Krühler, T.; Schady, P.; Ledoux, C.; Tanvir, N. R.; Levan, A. J.

2018-01-01

Context. Dust is known to be produced in the envelopes of asymptotic giant branch (AGB) stars, the expanded shells of supernova (SN) remnants, and in situ grain growth within the interstellar medium (ISM), although the corresponding efficiency of each of these dust formation mechanisms at different redshifts remains a topic of debate. During the first Gyr after the Big Bang, it is widely believed that there was not enough time to form AGB stars in high numbers, hence the dust at this epoch is expected to be purely from SNe or subsequent grain growth in the ISM. The time period corresponding to z 5-6 is thus expected to display the transition from SN-only dust to a mixture of both formation channels as is generally recognized at present. Aims: Here we aim to use afterglow observations of gamma-ray bursts (GRBs) at redshifts larger than z > 4 to derive host galaxy dust column densities along their line of sight and to test if a SN-type dust extinction curve is required for some of the bursts. Methods: We performed GRB afterglow observations with the seven-channel Gamma-Ray Optical and Near-infrared Detector (GROND) at the 2.2 m MPI telescope in La Silla, Chile (ESO), and we combined these observations with quasi-simultaneous data gathered with the XRT telescope on board the Swift satellite. Results: We increase the number of measured AV values for GRBs at z > 4 by a factor of 2-3 and find that, in contrast to samples at mostly lower redshift, all of the GRB afterglows have a visual extinction of AV < 0.5 mag. Analysis of the GROND detection thresholds and results from a Monte Carlo simulation show that although we partly suffer from an observational bias against highly extinguished sight-lines, GRB host galaxies at 4 < z < 6 seem to contain on average less dust than at z 2. Additionally, we find that all of the GRBs can be modeled with locally measured extinction curves and that the SN-like dust extinction curve, as previously found toward GRB 071025, provides a better fit for only two of the afterglow SEDs. However, because of the lack of highly extinguished sight lines and the limited wavelength coverage we cannot distinguish between the different scenarios. For the first time we also report a photometric redshift of zphot = 7.88-0.94+0.75 for GRB 100905A, making it one of the most distant GRBs known to date.

Lunar Dust: Characterization and Mitigation

NASA Technical Reports Server (NTRS)

Hyatt. Mark J.; Feighery, John

2007-01-01

Lunar dust is a ubiquitous phenomenon which must be explicitly addressed during upcoming human lunar exploration missions. Near term plans to revisit the moon as a stepping stone for further exploration of Mars, and beyond, places a primary emphasis on characterization and mitigation of lunar dust. Comprised of regolith particles ranging in size from tens of nanometers to microns, lunar dust is a manifestation of the complex interaction of the lunar soil with multiple mechanical, electrical, and gravitational effects. The environmental and anthropogenic factors effecting the perturbation, transport, and deposition of lunar dust must be studied in order to mitigate it's potentially harmful effects on exploration systems. The same hold true for assessing the risk it may pose for toxicological health problems if inhaled. This paper presents the current perspective and implementation of dust knowledge management and integration, and mitigation technology development activities within NASA's Exploration Technology Development Program. This work is presented within the context of the Constellation Program's Integrated Lunar Dust Management Strategy. This work further outlines the scientific basis for lunar dust behavior, it's characteristics and potential effects, and surveys several potential strategies for its control and mitigation both for lunar surface operations and within the working volumes of a lunar outpost. The paper also presents a perspective on lessons learned from Apollo and forensics engineering studies of Apollo hardware.

Foraminifer Shell Weight and Fragmentation: A Quantitative Study of the Influence of Temperature, [CO32-] and Dissolution on Proxies of the Marine Carbonate System

NASA Astrophysics Data System (ADS)

Mekik, F.; Pourmand, A.; Ward, B. M.

2015-12-01

Quantifying the various components of the marine carbonate system is important for understanding anthropogenic ocean acidification, and the rates and magnitudes of ocean acidification/ alkalization events in Earth's past. We performed multiple statistical analyses (factor analysis, partial correlations, multiple regression analysis and independent samples t -tests) on core top data using the Globorotalia menardii fragmentation index (MFI) in 89 core tops from across the tropical Pacific, Atlantic and Indian Oceans, the fragmentation trend of four species of foraminifers (Globorotalia truncatulinoides, G. menardii, Neogloboquadrina dutertrei and Pulleniatina obliquiloculata) in the EEP, tropical Atlantic and tropical Indian Ocean core tops, and Globorotalia menardii shell weight in a suite of 25 core tops the EEP in order to isolate the effects of surface ocean parameters such as temperature and [CO32-] from dissolution in sediments. Surface ocean parameters showed no significant effect on the G. menardii fragmentation index. We found no statistically significant influence of habitat water temperature or [CO32-] on foraminifer fragmentation in any of four species. While we found a strong influence of habitat water [CO32-] on the size normalized shell weight proxy in N. dutertrei and Pulleniatina obliquiloculata in our previous work, we found a much reduced influence of [CO32-] on the shell weight of G. menardii, which is most influenced by shell dissolution.

Electrodynamic Dust Shield for Space Applications

NASA Technical Reports Server (NTRS)

Mackey, P. J.; Johansen, M. R.; Olsen, R. C.; Raines, M. G.; Phillips, J. R., III; Pollard, J. R. S.; Calle, C. I.

2016-01-01

The International Space Exploration Coordination Group (ISECG) has chosen dust 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 dust on both human and robotic missions. During manned Apollo missions, dust 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 dust 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 dust 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 Dust Shield (EDS) to remove dust 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 (one-sixth g) in which Apollo Lunar dust samples were successfully removed from glass shields while under vacuum (10(exp -6) kPa).

Dust Observations by Faraday Cups Onboard Spektr-R

NASA Astrophysics Data System (ADS)

Pavlu, J.; Kociscak, S.; Safrankova, J.; Nemecek, Z.; Prech, L.

2017-12-01

Dust of both interstellar and interplanetary origins was reported in many in-situ experiments devoted to dust detection during past tens of years. Recently, a number of reports employed unintended devices to observe dust (Voyager, Cassini, STEREO …). Most of such observations is based on impact ionization occurring when hypervelocity grains hit a surface being vaporized together with a portion of the surface material. The thermal ionization generates a plasma plume and the dust detection is based on collection of plasma particles by, e.g., antennas. In this contribution, we apply a similar approach to dust impact detection using the multi Faraday cup instrument (BMSW) onboard the Spektr-R spacecraft. It is orbiting the Earth along the highly elliptical trajectory with perigee of 2 and apogee of 50 Re. The BMSW instrument consists of 6 Faraday cups measuring local environmental properties with a rate as high as 30 Hz, i.e., high enough to detect aforementioned plasma plumes. The advantages of the multiple Faraday cup instrument include an easy recognition of dust impacts among plasma disturbances/solitons — dust grain impact can be detected only by one Faraday cup at a given time. We analyze Faraday cup waveforms applying simple criteria on impact spike shape and find a number of dust impact candidates. Based on this experience, we suggest a modification of future devices with a similar detection system.

Laboratory Studies of the Cloud Droplet Activation Properties and Corresponding Chemistry of Saline Playa Dust

NASA Astrophysics Data System (ADS)

Gaston, C.; Pratt, K.; Suski, K. J.; May, N.; Gill, T. E.; Prather, K. A.

2016-12-01

Saline playas (dried lake beds) emit large quantities of dust that can facilitate the activation of cloud droplets. Despite the potential importance of playa dust for cloud formation, several models assume that dust is non-hygroscopic highlighting the need for measurements to clarify the role of dust from multiple sources in aerosol-cloud-climate interactions. Here we present water uptake measurements onto playa dust represented by the hygroscopicity parameter κ, which ranged from 0.002 ± 0.001 to 0.818 ± 0.094. Single-particle measurements made using an aircraft-aerosol time-of-flight mass spectrometer (A-ATOFMS) revealed the presence of halite, sodium sulfates, and sodium carbonates that were strongly correlated with κ underscoring the role that dust composition plays in water uptake. Predictions of κ made using bulk chemical techniques generally showed good agreement with measured values; however, several samples were poorly predicted using bulk particle composition. The lack of measurements/model agreement using this method and the strong correlations between κ and single-particle data are suggestive of chemical heterogeneities as a function of particle size and/or chemically distinct particle surfaces that dictate the water uptake properties of playa dust particles. Overall, our results highlight the ability of playa dust particles to act as cloud condensation nuclei that should be accounted for in models.

Identification of dust storm source areas in West Asia using multiple environmental datasets.

PubMed

Cao, Hui; Amiraslani, Farshad; Liu, Jian; Zhou, Na

2015-01-01

Sand and Dust storms are common phenomena in arid and semi-arid areas. West Asia Region, especially Tigris-Euphrates alluvial plain, has been recognized as one of the most important dust source areas in the world. In this paper, a method is applied to extract SDS (Sand and Dust Storms) sources in West Asia region using thematic maps, climate and geography, HYSPLIT model and satellite images. Out of 50 dust storms happened during 2000-2013 and collected in form of MODIS images, 27 events were incorporated as demonstrations of the simulated trajectories by HYSPLIT model. Besides, a dataset of the newly released Landsat images was used as base-map for the interpretation of SDS source regions. As a result, six main clusters were recognized as dust source areas. Of which, 3 clusters situated in Tigris-Euphrates plain were identified as severe SDS sources (including 70% dust storms in this research). Another cluster in Sistan plain is also a potential source area. This approach also confirmed six main paths causing dust storms. These paths are driven by the climate system including Siberian and Polar anticyclones, monsoon from Indian Subcontinent and depression from north of Africa. The identification of SDS source areas and paths will improve our understandings on the mechanisms and impacts of dust storms on socio-economy and environment of the region. Copyright © 2014 Elsevier B.V. All rights reserved.

Dust Density Distribution and Imaging Analysis of Different Ice Lines in Protoplanetary Disks

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

Pinilla, P.; Pohl, A.; Stammler, S. M.

Recent high angular resolution observations of protoplanetary disks at different wavelengths have revealed several kinds of structures, including multiple bright and dark rings. Embedded planets are the most used explanation for such structures, but there are alternative models capable of shaping the dust in rings as it has been observed. We assume a disk around a Herbig star and investigate the effect that ice lines have on the dust evolution, following the growth, fragmentation, and dynamics of multiple dust size particles, covering from 1 μ m to 2 m sized objects. We use simplified prescriptions of the fragmentation velocity threshold,more » which is assumed to change radially at the location of one, two, or three ice lines. We assume changes at the radial location of main volatiles, specifically H{sub 2}O, CO{sub 2}, and NH{sub 3}. Radiative transfer calculations are done using the resulting dust density distributions in order to compare with current multiwavelength observations. We find that the structures in the dust density profiles and radial intensities at different wavelengths strongly depend on the disk viscosity. A clear gap of emission can be formed between ice lines and be surrounded by ring-like structures, in particular between the H{sub 2}O and CO{sub 2} (or CO). The gaps are expected to be shallower and narrower at millimeter emission than at near-infrared, opposite to model predictions of particle trapping. In our models, the total gas surface density is not expected to show strong variations, in contrast to other gap-forming scenarios such as embedded giant planets or radial variations of the disk viscosity.« less

High concentrations of heavy metals in neighborhoods near ore smelters in northern Mexico.

PubMed Central

Benin, A L; Sargent, J D; Dalton, M; Roda, S

1999-01-01

In developing countries, rapid industrialization without environmental controls has resulted in heavy metal contamination of communities. We hypothesized that residential neighborhoods located near ore industries in three northern Mexican cities would be heavily polluted with multiple contaminants (arsenic, cadmium, and lead) and that these sites would be point sources for the heavy metals. To evaluate these hypotheses, we obtained samples of roadside surface dust from residential neighborhoods within 2 m of metal smelters [Torreón (n = 19)] and Chihuahua (n = 19)] and a metal refinery [Monterrey (n = 23)]. Heavy metal concentrations in dust were mapped with respect to distance from the industrial sites. Correlation between dust metal concentration and distance was estimated with least-squares regression using log-transformed data. Median dust arsenic, cadmium, and lead concentrations were 32, 10, and 277 microg/g, respectively, in Chihuahua; 42, 2, and 467 microg/g, respectively, in Monterrey, and 113, 112, and 2,448 microg/g, respectively, in Torreón. Dust concentrations of all heavy metals were significantly higher around the active smelter in Torreón, where more than 90% of samples exceeded Superfund cleanup goals. At all sites, dust concentrations were inversely related to distance from the industrial source, implicating these industries as the likely source of the contamination. We concluded that residential neighborhoods around metal smelting and refining sites in these three cities are contaminated by heavy metals at concentrations likely to pose a health threat to people living nearby. Evaluations of human exposure near these sites should be conducted. Because multiple heavy metal pollutants may exist near smelter sites, researchers should avoid attributing toxicity to one heavy metal unless others have been measured and shown not to coexist. Images Figure 1 Figure 2-3 Figure 4-5 Figure 6-7 Figure 8 PMID:10090706

Combing Visible and Infrared Spectral Tests for Dust Identification

NASA Technical Reports Server (NTRS)

Zhou, Yaping; Levy, Robert; Kleidman, Richard; Remer, Lorraine; Mattoo, Shana

2016-01-01

The MODIS Dark Target aerosol algorithm over Ocean (DT-O) uses spectral reflectance in the visible, near-IR and SWIR wavelengths to determine aerosol optical depth (AOD) and Angstrom Exponent (AE). Even though DT-O does have "dust-like" models to choose from, dust is not identified a priori before inversion. The "dust-like" models are not true "dust models" as they are spherical and do not have enough absorption at short wavelengths, so retrieved AOD and AE for dusty regions tends to be biased. The inference of "dust" is based on postprocessing criteria for AOD and AE by users. Dust aerosol has known spectral signatures in the near-UV (Deep blue), visible, and thermal infrared (TIR) wavelength regions. Multiple dust detection algorithms have been developed over the years with varying detection capabilities. Here, we test a few of these dust detection algorithms, to determine whether they can be useful to help inform the choices made by the DT-O algorithm. We evaluate the following methods: The multichannel imager (MCI) algorithm uses spectral threshold tests in (0.47, 0.64, 0.86, 1.38, 2.26, 3.9, 11.0, 12.0 micrometer) channels and spatial uniformity test [Zhao et al., 2010]. The NOAA dust aerosol index (DAI) uses spectral contrast in the blue channels (412nm and 440nm) [Ciren and Kundragunta, 2014]. The MCI is already included as tests within the "Wisconsin" (MOD35) Cloud mask algorithm.

AT Cnc: A SECOND DWARF NOVA WITH A CLASSICAL NOVA SHELL

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

Shara, Michael M.; Mizusawa, Trisha; Zurek, David

2012-10-20

We are systematically surveying all known and suspected Z Cam-type dwarf novae for classical nova shells. This survey is motivated by the discovery of the largest known classical nova shell, which surrounds the archetypal dwarf nova Z Camelopardalis. The Z Cam shell demonstrates that at least some dwarf novae must have undergone classical nova eruptions in the past, and that at least some classical novae become dwarf novae long after their nova thermonuclear outbursts, in accord with the hibernation scenario of cataclysmic binaries. Here we report the detection of a fragmented 'shell', 3 arcmin in diameter, surrounding the dwarf novamore » AT Cancri. This second discovery demonstrates that nova shells surrounding Z Cam-type dwarf novae cannot be very rare. The shell geometry is suggestive of bipolar, conical ejection seen nearly pole-on. A spectrum of the brightest AT Cnc shell knot is similar to that of the ejecta of the classical nova GK Per, and of Z Cam, dominated by [N II] emission. Galaxy Evolution Explorer FUV imagery reveals a similar-sized, FUV-emitting shell. We determine a distance of 460 pc to AT Cnc, and an upper limit to its ejecta mass of {approx}5 Multiplication-Sign 10{sup -5} M {sub Sun }, typical of classical novae.« less

NO2 Gas Sensing Properties of Multiple Networked ZnGa2O4 Nanorods Coated with TiO2.

PubMed

An, Soyeon; Park, Sunghoon; Ko, Hyunsung; Jin, Changhyun; Lee, Chongmu

2015-01-01

The NO2 gas sensing properties of ZnGa2O4-TiO2 heterostructure nanorods was examined. ZnGa2O4-core/TiO2-shell nanorods were fabricated by the thermal evaporation of a mixture of Zn and GaN powders and the sputter deposition of TiO2. Multiple networked ZnGa2O4-core/TiO2-shell nanorod sensors showed the response of 876% at 10 ppm NO2 at 300 degrees C. This response value at 10 ppm NO2 is approximately 4 times larger than that of bare ZnGa2O4 nanorod sensors. The response values obtained by the ZnGa2O4-core/TiO2-shell nanorods in this study are more than 13 times higher than those obtained previously by the SnO2-core/ZnO-shell nanofibers at 5% NO2. The significant enhancement in the response of ZnGa2O4 nanorods to NO2 gas by coating them with TiO2 can be explained based on the space-charge model.

Gene-by-environment effect of house dust mite on purinergic receptor P2Y12 (P2RY12) and lung function in children with asthma.

PubMed

Bunyavanich, S; Boyce, J A; Raby, B A; Weiss, S T

2012-02-01

Distinct receptors likely exist for leukotriene (LT)E(4), a potent mediator of airway inflammation. Purinergic receptor P2Y12 is needed for LTE(4)-induced airways inflammation, and P2Y12 antagonism attenuates house dust mite-induced pulmonary eosinophilia in mice. Although experimental data support a role for P2Y12 in airway inflammation, its role in human asthma has never been studied. To test for association between variants in the P2Y12 gene (P2RY12) and lung function in human subjects with asthma, and to examine for gene-by-environment interaction with house dust mite exposure. Nineteen single nucleotide polymorphisms (SNPs) in P2RY12 were genotyped in 422 children with asthma and their parents (n = 1266). Using family based methods, we tested for associations between these SNPs and five lung function measures. We performed haplotype association analyses and tested for gene-by-environment interactions using house dust mite exposure. We used the false discovery rate to account for multiple comparisons. Five SNPs in P2RY12 were associated with multiple lung function measures (P-values 0.006–0.025). Haplotypes in P2RY12 were also associated with lung function (P-values 0.0055–0.046). House dust mite exposure modulated associations between P2RY12 and lung function, with minor allele homozygotes exposed to house dust mite demonstrating worse lung function than those unexposed (significant interaction P-values 0.0028–0.040). The P2RY12 variants were associated with lung function in a large family-based asthma cohort. House dust mite exposure caused significant gene-by-environment effects. Our findings add the first human evidence to experimental data supporting a role for P2Y12 in lung function. P2Y12 could represent a novel target for asthma treatment.

Fill-Tube-Induced Mass Perturbations on X-Ray-Driven, Ignition-Scale, Inertial-Confinement-Fusion Capsule Shells and the Implications for Ignition Experiments

DOE PAGES

Bennett, G. R.; Herrmann, M. C.; Edwards, M. J.; ...

2007-11-13

We present on the first inertial-confinement-fusion ignition facility, the target capsule will be DT filled through a long, narrow tube inserted into the shell. μg-scale shell perturbations Δm' arising from multiple, 10–50 μm-diameter, hollow SiO 2 tubes on x-ray-driven, ignition-scale, 1-mg capsules have been measured on a subignition device. Finally, simulations compare well with observation, whence it is corroborated that Δm' arises from early x-ray shadowing by the tube rather than tube mass coupling to the shell, and inferred that 10–20 μm tubes will negligibly affect fusion yield on a full-ignition facility.

Correlations of neutron multiplicity and γ -ray multiplicity with fragment mass and total kinetic energy in spontaneous fission of Cf 252

DOE PAGES

Wang, Taofeng; Li, Guangwu; Zhu, Liping; ...

2016-01-08

The dependence of correlations of neutron multiplicity ν and γ-ray multiplicity M γ in spontaneous fission of 252Cf on fragment mass A* and total kinetic energy (TKE) have been investigated by employing the ratio of M γ/ν and the form of M γ(ν). We show for the first time that M γ and ν have a complex correlation for heavy fragment masses, while there is a positive dependence of Mγ for light fragment masses and for near-symmetric mass splits. The ratio M γ/ν exhibits strong shell effects for neutron magic number N=50 and near doubly magic number shell closure atmore » Z=50 and N=82. The γ-ray multiplicity Mγ has a maximum for TKE=165-170 MeV. Above 170 MeV M γ(TKE) is approximately linear, while it deviates significantly from a linear dependence at lower TKE. The correlation between the average neutron and γ-ray multiplicities can be partly reproduced by model calculations.« less

Core excitations across the neutron shell gap in 207Tl

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

Wilson, E.; Podolyák, Zs.; Grawe, H.

2015-05-05

The single closed-neutron-shell, one proton–hole nucleus 207Tl was populated in deep-inelastic collisions of a 208Pb beam with a 208Pb target. The yrast and near-yrast level scheme has been established up to high excitation energy, comprising an octupole phonon state and a large number of core excited states. Based on shell-model calculations, all observed single core excitations were established to arise from the breaking of the N=126 neutron core. While the shell-model calculations correctly predict the ordering of these states, their energies are compressed at high spins. It is concluded that this compression is an intrinsic feature of shell-model calculations usingmore » two-body matrix elements developed for the description of two-body states, and that multiple core excitations need to be considered in order to accurately calculate the energy spacings of the predominantly three-quasiparticle states.« less

Electrosprayed core-shell polymer-lipid nanoparticles for active component delivery

NASA Astrophysics Data System (ADS)

Eltayeb, Megdi; Stride, Eleanor; Edirisinghe, Mohan

2013-11-01

A key challenge in the production of multicomponent nanoparticles for healthcare applications is obtaining reproducible monodisperse nanoparticles with the minimum number of preparation steps. This paper focus on the use of electrohydrodynamic (EHD) techniques to produce core-shell polymer-lipid structures with a narrow size distribution in a single step process. These nanoparticles are composed of a hydrophilic core for active component encapsulation and a lipid shell. It was found that core-shell nanoparticles with a tunable size range between 30 and 90 nm and a narrow size distribution could be reproducibly manufactured. The results indicate that the lipid component (stearic acid) stabilizes the nanoparticles against collapse and aggregation and improves entrapment of active components, in this case vanillin, ethylmaltol and maltol. The overall structure of the nanoparticles produced was examined by multiple methods, including transmission electron microscopy and differential scanning calorimetry, to confirm that they were of core-shell form.

Dynamic strength of cylindrical fiber-glass shells and basalt plastic shells under multiple explosive loading

NASA Astrophysics Data System (ADS)

Syrunin, M. A.; Fedorenko, A. G.

2006-08-01

We have shown experimentally that, for cylindrical shells made of oriented fiberglass platic and basalt plastic there exists a critical level of deformations, at which a structure sustains a given number of explosions from the inside. The magnitude of critical deformation for cylindrical fiberglass shells depends linearly on the logarithm of the number of loads that cause failure. For a given type of fiberglass, there is a limiting level of explosive action, at which the number of loads that do not lead to failure can be sufficiently large (more than ˜ 102). This level is attained under loads, which are an order of magnitude lower than the limiting loads under a single explosive action. Basalt plastic shells can be repeatedly used even at the loads, which cause deformation by ˜ 30-50% lower than the safe value ˜ 3.3.5% at single loading.

Non-parametric representation and prediction of single- and multi-shell diffusion-weighted MRI data using Gaussian processes

PubMed Central

Andersson, Jesper L.R.; Sotiropoulos, Stamatios N.

2015-01-01

Diffusion MRI offers great potential in studying the human brain microstructure and connectivity. However, diffusion images are marred by technical problems, such as image distortions and spurious signal loss. Correcting for these problems is non-trivial and relies on having a mechanism that predicts what to expect. In this paper we describe a novel way to represent and make predictions about diffusion MRI data. It is based on a Gaussian process on one or several spheres similar to the Geostatistical method of “Kriging”. We present a choice of covariance function that allows us to accurately predict the signal even from voxels with complex fibre patterns. For multi-shell data (multiple non-zero b-values) the covariance function extends across the shells which means that data from one shell is used when making predictions for another shell. PMID:26236030

X-RAY EMISSION FROM THE WOLF-RAYET BUBBLE S 308

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

Toala, J. A.; Guerrero, M. A.; Chu, Y.-H.

The Wolf-Rayet (WR) bubble S 308 around the WR star HD 50896 is one of the only two WR bubbles known to possess X-ray emission. We present XMM-Newton observations of three fields of this WR bubble that, in conjunction with an existing observation of its northwest quadrant, map most of the nebula. The X-ray emission from S 308 displays a limb-brightened morphology, with a central cavity {approx}22' in size and a shell thickness of {approx}8'. This X-ray shell is confined by the optical shell of ionized material. The spectrum is dominated by the He-like triplets of N VI at 0.43more » keV and O VII at 0.57 keV, and declines toward high energies, with a faint tail up to 1 keV. This spectrum can be described by a two-temperature optically thin plasma emission model (T{sub 1} {approx} 1.1 Multiplication-Sign 10{sup 6} K, T{sub 2} {approx} 13 Multiplication-Sign 10{sup 6} K), with a total X-ray luminosity {approx}2 Multiplication-Sign 10{sup 33} erg s{sup -1} at the assumed distance of 1.5 kpc.« less

Seasonal and occupational trends of five organophosphate pesticides in house dust.

PubMed

Smith, Marissa N; Workman, Tomomi; McDonald, Katie M; Vredevoogd, Melinda A; Vigoren, Eric M; Griffith, William C; Thompson, Beti; Coronado, Gloria D; Barr, Dana; Faustman, Elaine M

2017-07-01

Since 1998, the University of Washington's Center for Child Environmental Health Risks Research has followed a community-based participatory research strategy in the Lower Yakima Valley of Washington State to assess pesticide exposure among families of Hispanic farmworkers. As a part of this longitudinal study, house dust samples were collected from both farmworker and non-farmworker households, across three agricultural seasons (thinning, harvest and non-spray). The household dust samples were analyzed for five organophosphate pesticides: azinphos-methyl, phosmet, malathion, diazinon, and chlorpyrifos. Organophosphate pesticide levels in house dust were generally reflective of annual use rates and varied by occupational status and agricultural season. Overall, organophosphate pesticide concentrations were higher in the thinning and harvest seasons than in the non-spray season. Azinphos-methyl was found in the highest concentrations across all seasons and occupations. Farmworker house dust had between 5- and 9-fold higher concentrations of azinphos-methyl than non-farmworker house dust. Phosmet was found in 5-7-fold higher concentrations in farmworker house dust relative to non-farmworker house dust. Malathion and chlorpyriphos concentrations in farmworker house dust ranged between 1.8- and 9.8-fold higher than non-farmworker house dust. Diazinon showed a defined seasonal pattern that peaked in the harvest season and did not significantly differ between farmworker and non-farmworker house dust. The observed occupational differences in four out of five of the pesticide residues measured provides evidence supporting an occupational take home pathway, in which workers may bring pesticides home on their skin or clothing. Further, these results demonstrate the ability of dust samples to inform the episodic nature of organophosphate pesticide exposures and the need to collect multiple samples for complete characterization of exposure potential.

Cosmic dust and space debris; Proceedings of the Topical Meetings and Workshop 6 of the 26th COSPAR Plenary Meeting, Toulouse, France, June 30-July 11, 1986

NASA Technical Reports Server (NTRS)

Mcdonnell, J. A. M. (Editor); Hanner, M. S. (Editor); Kessler, D. J. (Editor)

1986-01-01

These proceedings encompass topics in the fields of extraterrestrial material samples, IRAS solar system and dust model results, and earth orbit debris. Attention is given to chemical fractionation during high velocity impact, particle deceleration and survival in multiple thin foil targets, and IRAS studies of asteroids, comets, cometary tails, the zodiacal background, and the three-dimensional modeling of interplanetary dust. Also discussed are the evolution of an earth orbit debris cloud, orbital debris due to future space activities, collision probabilities in geosynchronous orbits, and a bitelescopic survey of low altitude orbital debris.

Quasiballistic quantum transport through Ge/Si core/shell nanowires

NASA Astrophysics Data System (ADS)

Kotekar-Patil, D.; Nguyen, B.-M.; Yoo, J.; Dayeh, S. A.; Frolov, S. M.

2017-09-01

We study signatures of ballistic quantum transport of holes through Ge/Si core/shell nanowires at low temperatures. We observe Fabry-Pérot interference patterns as well as conductance plateaus at integer multiples of 2e 2/h at zero magnetic field. Magnetic field evolution of these plateaus reveals relatively large effective Landé g-factors. Ballistic effects are observed in nanowires with silicon shell thickness of 1-3 nm, but not in bare germanium wires. These findings inform the future development of spin and topological quantum devices which rely on ballistic sub-band-resolved transport.

Comparative analysis of early ontogeny in Bursatella leachii and Aplysia californica

PubMed Central

Vue, Zer; Capo, Thomas R.; Bardales, Ana T.

2014-01-01

Opisthobranch molluscs exhibit fascinating body plans associated with the evolution of shell loss in multiple lineages. Sea hares in particular are interesting because Aplysia californica is a well-studied model organism that offers a large suite of genetic tools. Bursatella leachii is a related tropical sea hare that lacks a shell as an adult and therefore lends itself to comparative analysis with A. californica. We have established an enhanced culturing procedure for B. leachii in husbandry that enabled the study of shell formation and loss in this lineage with respect to A. californica life staging. PMID:25538871

Quasiballistic quantum transport through Ge/Si core/shell nanowires

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

Kotekar-Patil, D.; Nguyen, B-M; Yoo, J.

We study signatures of ballistic quantum transport of holes through Ge/Si core/shell nanowires at low temperatures. We observe Fabry–Pérot interference patterns as well as conductance plateaus at integer multiples of 2e 2/h at zero magnetic field. Magnetic field evolution of these plateaus reveals relatively large effective Landé g-factors. Ballistic effects are observed in nanowires with silicon shell thickness of 1–3 nm, but not in bare germanium wires. These findings inform the future development of spin and topological quantum devices which rely on ballistic sub-band-resolved transport.

Quasiballistic quantum transport through Ge/Si core/shell nanowires

DOE PAGES

Kotekar-Patil, D.; Nguyen, B-M; Yoo, J.; ...

2017-09-04

We study signatures of ballistic quantum transport of holes through Ge/Si core/shell nanowires at low temperatures. We observe Fabry–Pérot interference patterns as well as conductance plateaus at integer multiples of 2e 2/h at zero magnetic field. Magnetic field evolution of these plateaus reveals relatively large effective Landé g-factors. Ballistic effects are observed in nanowires with silicon shell thickness of 1–3 nm, but not in bare germanium wires. These findings inform the future development of spin and topological quantum devices which rely on ballistic sub-band-resolved transport.

Expanding shell and star formation in the infrared dust bubble N6

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

Yuan, Jing-Hua; Li, Jin Zeng; Liu, Hongli

2014-12-10

We have carried out a multiwavelength study of the infrared dust bubble N6 to extensively investigate the molecular environs and star-forming activities therein. Mapping observations in {sup 12}CO J = 1-0 and {sup 13}CO J = 1-0 performed with the Purple Mountain Observatory 13.7 m telescope have revealed four velocity components. Comparison between distributions of each component and the infrared emission suggests that three components are correlated with N6. There are 10 molecular clumps detected. Among them, five have reliable detections in both {sup 12}CO and {sup 13}CO and have similar LTE and non-LTE masses ranging from 200 to highermore » than 5000 M {sub ☉}. With larger gas masses than virial masses, these five clumps are gravitationally unstable and have the potential to collapse to form new stars. The other five clumps are only reliably detected in {sup 12}CO and have relatively small masses. Five clumps are located on the border of the ring structure, and four of them are elongated along the shell. This is well in agreement with the collect-and-collapse scenario. The detected velocity gradient reveals that the ring structure is still under expansion owing to stellar winds from the exciting star(s). Furthermore, 99 young stellar objects (YSOs) have been identified based on their infrared colors. A group of YSOs reside inside the ring, indicating active star formation in N6. Although no confirmative features of triggered star formation are detected, the bubble and the enclosed H II region have profoundly reconstructed the natal cloud and altered the dynamics therein.« less

Exotic Metal Molecules in Oxygen-rich Envelopes: Detection of AlOH (X1Σ+) in VY Canis Majoris

NASA Astrophysics Data System (ADS)

Tenenbaum, E. D.; Ziurys, L. M.

2010-03-01

A new interstellar molecule, AlOH, has been detected toward the envelope of VY Canis Majoris (VY CMa), an oxygen-rich red supergiant. Three rotational transitions of AlOH were observed using the facilities of the Arizona Radio Observatory (ARO). The J = 9 → 8 and J = 7 → 6 lines at 1 mm were measured with the ARO Submillimeter Telescope, while the J = 5 → 4 transition at 2 mm was observed with the ARO 12 m antenna on Kitt Peak. The AlOH spectra exhibit quite narrow line widths of 16-23 km s-1, as found for NaCl in this source, indicating that the emission arises from within the dust acceleration zone of the central circumstellar outflow. From a radiative transfer analysis, the abundance of AlOH relative to H2 was found to be ~1 × 10-7 for a source size of 0.26'' or 22 R* . In contrast, AlCl was not detected with f <= 5 × 10-8. AlOH is likely formed just beyond the photosphere via thermodynamic equilibrium chemistry and then disappears due to dust condensation. The AlOH/AlO abundance ratio found in VY CMa is ~17. Therefore, AlOH appears to be the dominant gas-phase molecular carrier of aluminum in this oxygen-rich shell. Local thermodynamic equilibrium calculations predict that the monohydroxides should be the major carriers of Al, Ca, and Mg in O-rich envelopes, as opposed to the oxides or halides. The apparent predominance of aluminum-bearing molecules in VY CMa may reflect proton addition processes in H-shell burning.

Diagnostics and characterization of nanodust and nanodusty plasmas★

NASA Astrophysics Data System (ADS)

Greiner, Franko; Melzer, Andrè; Tadsen, Benjamin; Groth, Sebastian; Killer, Carsten; Kirchschlager, Florian; Wieben, Frank; Pilch, Iris; Krüger, Harald; Block, Dietmar; Piel, Alexander; Wolf, Sebastian

2018-05-01

Plasmas growing or containing nanometric dust particles are widely used and proposed in plasma technological applications for production of nano-crystals and surface deposition. Here, we give a compact review of in situ methods for the diagnostics of nanodust and nanodusty plasmas, which have been developed in the framework of the SFB-TR24 to fully characterize these systems. The methods include kinetic Mie ellipsometry, angular-resolved Mie scattering, and 2D imaging Mie ellipsometry to get information about particle growth processes, particle sizes and particle size distributions. There, also the role of multiple scattering events is analyzed using radiative transfer simulations. Computed tomography and Abel inversion techniques to get the 3D dust density profiles of the particle cloud will be presented. Diagnostics of the dust dynamics yields fundamental dust and plasma properties like particle charges and electron and ion densities. Since nanodusty plasmas usually form dense dust clouds electron depletion (Havnes effect) is found to be significant.

Dust Particle Dynamics in The Presence of Highly Magnetized Plasmas

NASA Astrophysics Data System (ADS)

Lynch, Brian; Konopka, Uwe; Thomas, Edward; Merlino, Robert; Rosenberg, Marlene

2016-10-01

Complex plasmas are four component plasmas that contain, in addition to the usual electrons, ions, and neutral atoms, macroscopic electrically charged (nanometer to micrometer) sized ``dust'' 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 dust 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 dust particle gx B deflection and, from that deflection, determine the dust 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.

Millennial-scale variations in dustiness recorded in Mid-Atlantic sediments from 0 to 70 ka

NASA Astrophysics Data System (ADS)

Middleton, Jennifer L.; Mukhopadhyay, Sujoy; Langmuir, Charles H.; McManus, Jerry F.; Huybers, Peter J.

2018-01-01

Sedimentary records of dust deposition in the subtropical Atlantic provide important constraints on millennial- and orbital-scale variability in atmospheric circulation and North African aridity. Constant flux proxies, such as extraterrestrial helium-3, yield dust flux records that are independent of the biases caused by lateral sediment transport and limited resolution that may be associated with age-model-derived mass accumulation rates. However, Atlantic dust records constrained using constant flux proxies are sparsely distributed and generally limited to the past 20 ka. Here we extend the Atlantic record of North African dust deposition to 70 ka using extraterrestrial helium-3 and measurements of titanium, thorium, and terrigenous helium-4 in two sediment cores collected at 26°N and 29°N on the Mid-Atlantic Ridge and compare results to model estimates for dust deposition in the subtropical North Atlantic. Dust proxy fluxes between 26°N and 29°N are well correlated, despite variability in lateral sediment transport, and underscore the utility of extraterrestrial helium-3 for constraining millennial-scale variability in dust deposition. Similarities between Mid-Atlantic dust flux trends and those observed along the Northwest African margin corroborate previous interpretations of dust flux variability over the past 20 ka and suggest that long distance transport and depositional processes do not overly obscure the signal of North African dust emissions. The 70 ka Mid-Atlantic record reveals a slight increase in North African dustiness from Marine Isotope Stage 4 through the Last Glacial Maximum and a dramatic decrease in dustiness associated with the African Humid Period. On the millennial-scale, the new records exhibit brief dust maxima coincident with North Atlantic cold periods such as the Younger Dryas, and multiple Heinrich Stadials. The correlation between Mid-Atlantic dust fluxes and previous constraints on North African aridity is high. However, precipitation exerts less control on dust flux variability prior to the African Humid Period, when wind variability governs dust emissions from consistently dry dust source regions. Thus, the Mid-Atlantic dust record supports the hypothesis that both aridity and wind strength drive dust flux variability across changing climatic conditions.

Searching for Cool Dust in the Mid-to-far Infrared: The Mass-loss Histories of the Hypergiants μ Cep, VY CMa, IRC+10420, and ρ Cas

NASA Astrophysics Data System (ADS)

Shenoy, Dinesh; Humphreys, Roberta M.; Jones, Terry J.; Marengo, Massimo; Gehrz, Robert D.; Helton, L. Andrew; Hoffmann, William F.; Skemer, Andrew J.; Hinz, Philip M.

2016-03-01

We present mid- and far-IR imaging of four famous hypergiant stars: the red supergiants μ Cep and VY CMa, and the warm hypergiants IRC +10420 and ρ Cas. Our 11-37 μm SOFIA/FORCAST imaging probes cool dust not detected in visual and near-IR imaging studies. Adaptive optics 8-12 μm imaging of μ Cep and IRC +10420 with MMT/MIRAC reveals extended envelopes that are the likely sources of these stars’ strong silicate emission features. We find μ Cep’s mass-loss rate to have declined by about a factor of five over a 13,000 year history, ranging from 5 × 10-6 down to ˜1× 10-6 M⊙ yr-1. The morphology of VY CMa indicates a cooler dust component coincident with the highly asymmetric reflection nebulae seen in the visual and near-IR. The lack of cold dust at greater distances around VY CMa indicates that its mass-loss history is limited to the last ˜1200 years, with an average rate of 6 × 10-4 M⊙ yr-1. We find two distinct periods in the mass-loss history of IRC +10420 with a high rate of 2 × 10-3 M⊙ yr-1 until approximately 2000 years ago, followed by an order of magnitude decrease in the recent past. We interpret this change as evidence of its evolution beyond the RSG stage. Our new infrared photometry of ρ Cas is consistent with emission from the expanding dust shell ejected in its 1946 eruption, with no evidence of newer dust formation from its more recent events. Based on observations obtained with: (1) the NASA/DLR Stratospheric Observatory for Infrared Astronomy (SOFIA). SOFIA is jointly operated by the Universities Space Research Association, Inc. (USRA), under NASA contract NAS2-97001, and the Deutsches SOFIA Institut (DSI) under DLR contract 50 OK 0901 to the University of Stuttgart; and (2) the MMT Observatory on Mt. Hopkins, AZ, a joint facility of the Smithsonian Institution and the University of Arizona.

Dead Star Rumbles

NASA Technical Reports Server (NTRS)

2005-01-01

[figure removed for brevity, see original site] Composite of Supernova Remnant Cassiopeia A This Spitzer Space Telescope composite shows the supernova remnant Cassiopeia A (white ball) and surrounding clouds of dust (gray, orange and blue). It consists of two processed images taken one year apart. Dust features that have not changed over time appear gray, while those that have changed are colored blue or orange. Blue represents an earlier time and orange, a later time.

These observations illustrate that a blast of light from Cassiopeia A is waltzing outward through the dusty skies. This dance, called an 'infrared echo,' began when the remnant erupted about 50 years ago.

Cassiopeia A is the remnant of a once massive star that died in a violent supernova explosion 325 years ago. It consists of a dead star, called a neutron star, and a surrounding shell of material that was blasted off as the star died. This remnant is located 10,000 light-years away in the northern constellation Cassiopeia.

An infrared echo is created when a star explodes or erupts, flashing light into surrounding clumps of dust. As the light zips through the dust clumps, it heats them up, causing them to glow successively in infrared, like a chain of Christmas bulbs lighting up one by one. The result is an optical illusion, in which the dust appears to be flying outward at the speed of light. This apparent motion can be seen here by the shift in colored dust clumps.

Echoes are distinct from supernova shockwaves, which are made up material that is swept up and hurled outward by exploding stars.

This infrared echo is the largest ever seen, stretching more than 50 light-years away from Cassiopeia A. If viewed from Earth, the entire movie frame would take up the same amount of space as two full moons.

Hints of an older infrared echo from Cassiopeia A's supernova explosion hundreds of years ago can also be seen.

The earlier Spitzer image was taken on November 30, 2003, and the later, on December 2, 2004.

Recalescence during crystallization of stardust: Resolution of the amorphous interstellar medium paradox

NASA Astrophysics Data System (ADS)

Whittington, A. G.; Sehlke, A.; Speck, A. K.

2017-12-01

Dust that coalesces to form planetary systems originates around dying stars, before passing into the interstellar medium (ISM). Historically, observations of broad smooth features in the 10-µm region suggested that dust in circumstellar regions, and in the ISM, was mostly amorphous rather than crystalline. With improved space telescope capabilities, crystalline silicates were discovered in the circumstellar regions around both young and old stars, although they remain undetected in the ISM. Despite intensive study the precise conditions that lead to the formation of crystalline silicates are still unknown, and their absence in the ISM remains problematic. Here we show that recalescence (spontaneous reheating) of rapidly crystallizing dust can explain the formation and apparent disappearance of crystalline silicates in space. We have documented recalescence in rapidly crystallizing Mg-rich silicate melts, with local heating at the crystallization front exceeding 160˚C in some cases. In circumstellar dust shells, amorphous grains with similar compositions condense at temperatures near their glass transition, and if they crystallize, they will recalesce. The higher temperature (T) of newly crystallized dust allows crystalline spectral features to be seen, because flux emitted depends on T4. After cooling to ambient temperature, crystalline spectral features in the ISM are concealed by volumetrically dominant amorphous dust. Our results explain the existence of crystalline silicate pre-solar grains, which are older than the solar system, and have implications for radiative transfer modeling and hydrodynamics of dusty environments, which are sensitive to small variations in optical properties. Our observations of mm-scale temperature differences up to 100˚C in cooling lava suggest that thermal imaging of basaltic lava flows needs to be conducted with mm-scale spatial resolution (see figure; crucible is 5mm diameter). Temperatures recorded with low spatial resolution, which average cooler melt and hotter crystals in a single pixel, will systematically overestimate the temperature of the liquid phase. Only the surface of a lava flow is likely to cool quickly enough for recalescence to occur, but this is precisely the part of the lava that is monitored by thermal imaging.

Electrodynamic Dust Shield for Space Applications

NASA Technical Reports Server (NTRS)

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.

2016-01-01

Dust 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 Dust Shield (EDS) to remove dust 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 component 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.

Effect Of Long-Period Earthquake Ground Motions On Nonlinear Vibration Of Shells With Variable Thickness

NASA Astrophysics Data System (ADS)

Abdikarimov, R.; Bykovtsev, A.; Khodzhaev, D.; Research Team Of Geotechnical; Structural Engineers

2010-12-01

Long-period earthquake ground motions (LPEGM) with multiple oscillations have become a crucial consideration in seismic hazard assessment because of the rapid increase of tall buildings and special structures (SP).Usually, SP refers to innovative long-span structural systems. More specifically, they include many types of structures, such as: geodesic showground; folded plates; and thin shells. As continuation of previous research (Bykovtsev, Abdikarimov, Khodzhaev 2003, 2010) analysis of nonlinear vibrations (NV) and dynamic stability of SP simulated as shells with variable rigidity in geometrically nonlinear statement will be presented for two cases. The first case will represent NV example of a viscoelastic orthotropic cylindrical shell with radius R, length L and variable thickness h=h(x,y). The second case will be NV example of a viscoelastic shell with double curvature, variable thickness, and bearing the concentrated masses. In both cases we count, that the SP will be operates under seismic load generated by LPEGM with multiple oscillations. For different seismic loads simulations, Bykovtsev’s Model and methodology was used for generating LPEGM time history. The methodology for synthesizing LPEGM from fault with multiple segmentations was developed by Bykovtev (1978-2010) and based on 3D-analytical solutions by Bykovtsev-Kramarovskii (1987&1989) constructed for faults with multiple segmentations. This model is based on a kinematics description of displacement function on the fault and included in consideration of all possible combinations of 3 components of vector displacement (two slip vectors and one tension component). The opportunities to take into consideration fault segmentations with both shear and tension vector components of displacement on the fault plane provide more accurate LPEGM evaluations. Radiation patterns and directivity effects were included in the model and more physically realistic results for simulated LPEGM were considered. The system of nonlinear integro-differential equations (NIDE) with variable coefficients concerning a deflection w=w(x,y) and displacements u=u(x,y), v=v(x,y) was used for construction mathematical model of the problem. The Kichhoff-Love hypothesis was used as basis for description physical and geometrical relations and construction of a discrete model of nonlinear problems dynamic theory of viscoelasticity. The most effective variational Bubnov-Galerkin method was used for obtaining Volterra type system of NIDE. The integration of the obtained equations system was carried out with the help of the numerical method based on quadrature formula. The computer codes on algorithmic language Delphi were created for investigation amplitude-time, deflected mode and torque-time characteristic of vibrations of the viscoelastic shells. For real composite materials at wide ranges of change of physical-mechanical and geometrical parameters the behavior of shells were investigated. Calculations were carried out at different laws of change of thickness. Results will be presented as graphs and tables.

Wind-Stress Dust Lifting in a Mars Global Circulation Model: Representation across Resolutions

NASA Astrophysics Data System (ADS)

Chapman, R.; Lewis, S.; Balme, M. R.; Steele, L.

2017-12-01

The formation of Martian dust storms is believed to be driven by dust lifting by near-surface wind stress (NSWS). Accurately representing this dust lifting within Mars Global Circulation Models (MGCMs) is important in order to gain a full understanding of the Martian dust storm cycle. Parameterisations of dust lifting by NSWS exist within several MGCMs; implementations differ but they all follow a similar design, so progress within one model is relevant to the entire field. Few studies have explored in detail how the results of these parameterisations can be affected by changing the horizontal resolution of the model. An accurate parameterisation of dust lifting by NSWS will lift a representative dust mass, reproducing characteristic dust optical depths in the atmosphere. The geographical distribution of the dust lifting by NSWS will also change throughout the year, affecting patterns of dust storm formation and development. Currently, suitable values for dust lifting parameters must be identified at every new model resolution. Resolutions of 5° latitude x 5° longitude are often used to model the Martian climate, as thermal tides and long-term weather patterns can be well represented at this resolution. However, smaller scale phenomena (such as near-surface winds driven by local topography) cannot be accurately depicted at this resolution. We use the LMD-UK MGCM to complete multi-year simulations across multiple model resolutions. Our experiments range from `low' resolution 5° lat x 5° lon to `high' resolution 1° lat x 1° lon. In experiments with fixed, constant lifting parameters, we find that higher resolution simulations lift more dust, but that this trend is asymptotic. At low resolutions, dust lifting increases proportionately with the increase in number of horizontal gridboxes. However, at high resolutions, doubling the number of gridboxes results only in a 30% increase in the total dust mass lifted. Geographical and temporal distributions of dust lifting are investigated, as well as the total dust lifted, in order to assess the optimum parameters for each resolution, and to develop a calibration scheme for this dust lifting across model resolutions. The scheme is verified through comparison with spacecraft observations of dust optical depths and dust storm locations.

Assimilation of MODIS Dark Target and Deep Blue Observations in the Dust Aerosol Component of NMMB-MONARCH version 1.0

NASA Technical Reports Server (NTRS)

Di Tomaso, Enza; Schutgens, Nick A. J.; Jorba, Oriol; Perez Garcia-Pando, Carlos

2017-01-01

A data assimilation capability has been built for the NMMB-MONARCH chemical weather prediction system, with a focus on mineral dust, 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 dust emission scheme. Experiments showed that MODIS AOD retrievals using the Dark Target algorithm can help NMMB-MONARCH to better characterize atmospheric dust. This is particularly true for the analysis of the dust 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 dust 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 dust in the long-range Atlantic transport and degradation of the temporal evolution of dust 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 dust is a first step towards data assimilation with a complete aerosol prediction system that includes multiple aerosol species.

Dust Flux Monitor Instrument for the Stardust mission to comet Wild 2

NASA Astrophysics Data System (ADS)

Tuzzolino, A. J.; Economou, T. E.; McKibben, R. B.; Simpson, J. A.; McDonnell, J. A. M.; Burchell, M. J.; Vaughan, B. A. M.; Tsou, P.; Hanner, M. S.; Clark, B. C.; Brownlee, D. E.

2003-10-01

The Dust Flux Monitor Instrument (DFMI) is part of the Stardust instrument payload. The prime goal of the DFMI is to measure the particle flux, intensity profile, and mass distribution during passage through the coma of comet Wild 2 in January 2004. This information is valuable for assessment of spacecraft risk and health and also for interpretation of the laboratory analysis of dust captured by the Aerogel dust collectors and returned to Earth. At the encounter speed of 6.1 km/s, the DFMI measurements will extend over the particle mass range of 8 decades, from 10-11 to >10-3 g. A secondary science goal is to measure the particle flux and mass distribution during the ~7 year interplanetary portions of the mission, where, in addition to measurements of the background interplanetary dust over the radial range 0.98 AU to 2.7 AU, multiple opportunities exist for possible detection by the DFMI of interplanetary meteor-stream particles and interstellar dust. The DFMI consists of two different dust detector systems: a polyvinylidene fluoride (PVDF) Dust Sensor Unit (SU), which measures particles with mass <~10-4 g, and a Dual Acoustic Sensor System (DASS), which utilizes two quartz piezoelectric accelerometers mounted on the first two layers of the spacecraft Whipple dust shield to measure the flux of particles with mass >10-4 g. The large Whipple shield structures provide the large effective sensitive area required for detection of the expected low flux of high-mass particles.

Assimilation of MODIS Dark Target and Deep Blue observations in the dust aerosol component of NMMB-MONARCH version 1.0

NASA Astrophysics Data System (ADS)

Di Tomaso, Enza; Schutgens, Nick A. J.; Jorba, Oriol; Pérez García-Pando, Carlos

2017-03-01

A data assimilation capability has been built for the NMMB-MONARCH chemical weather prediction system, with a focus on mineral dust, 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 dust emission scheme. Experiments showed that MODIS AOD retrievals using the Dark Target algorithm can help NMMB-MONARCH to better characterize atmospheric dust. This is particularly true for the analysis of the dust 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 dust 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 dust in the long-range Atlantic transport and degradation of the temporal evolution of dust 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 dust is a first step towards data assimilation with a complete aerosol prediction system that includes multiple aerosol species.

Multiple-collision analysis of characteristic X-rays from low-energy Ar 2+ travelling in solid targets

NASA Astrophysics Data System (ADS)

Cipolla, Sam J.; Mildebrath, Mark E.

1983-12-01

The density of atoms in a solid target fosters a multiple-collision mechanism that leads to the production of an equilibrium fraction of L-shell vacancies in an incident heavy ion. It is then possiblein a subsequent ion-atom collision in the solid for an L-vacancy to be transferred to the K-shell of a target atom via rotational coupling of the 2p π-2p σ molecular orbitals formed in the ion-atom quasimolecule. The vacancy-transfer cross section and the equilibrium fraction and lifetime of the vacancies can be found by using an appropriate multiple-collision analysis of the characteristic target and projectile X-rays. Results will be presented for 160-380 keV Ar 2+ incident of targets of Mg, Al, and Si.

Lunar Dust Mitigation Technology Development

NASA Technical Reports Server (NTRS)

Hyatt, Mark J.; Deluane, Paul B.

2008-01-01

NASA s plans for implementing the Vision for Space Exploration include returning to the moon as a stepping stone for further exploration of Mars, and beyond. Dust on the lunar surface has a ubiquitous presence which must be explicitly addressed during upcoming human lunar exploration missions. While the operational challenges attributable to dust during the Apollo missions did not prove critical, the comparatively long duration of impending missions presents a different challenge. Near term plans to revisit the moon places a primary emphasis on characterization and mitigation of lunar dust. Comprised of regolith particles ranging in size from tens of nanometers to microns, lunar dust is a manifestation of the complex interaction of the lunar soil with multiple mechanical, electrical, and gravitational effects. The environmental and anthropogenic factors effecting the perturbation, transport, and deposition of lunar dust must be studied in order to mitigate it s potentially harmful effects on exploration systems. This paper presents the current perspective and implementation of dust knowledge management and integration, and mitigation technology development activities within NASA s Exploration Technology Development Program. This work is presented within the context of the Constellation Program s Integrated Lunar Dust Management Strategy. The Lunar Dust Mitigation Technology Development project has been implemented within the ETDP. Project scope and plans will be presented, along with a a perspective on lessons learned from Apollo and forensics engineering studies of Apollo hardware. This paper further outlines the scientific basis for lunar dust behavior, it s characteristics and potential effects, and surveys several potential strategies for its control and mitigation both for lunar surface operations and within the working volumes of a lunar outpost.

Factors influencing on the bioaccessibility of polybrominated diphenyl ethers in size-specific dust from air conditioner filters.

PubMed

Yu, Yingxin; Yang, Dan; Wang, Xinxin; Huang, Ningbao; Zhang, Xinyu; Zhang, Dongping; Fu, Jiamo

2013-11-01

Size-specific concentrations and bioaccessibility of polybrominated diphenyl ethers (PBDEs) in dust from air conditioner filters were measured, and the factors influencing the PBDE bioaccessibility were determined. Generally, the PBDE concentrations increased with decreasing dust particle size, and BDE209 (deca-BDE) was generally the predominant congener. The bioaccessibility ranged from 20.3% to 50.8% for tri- to hepta-BDEs, and from 5.1% to 13.9% for BDE209 in dust fractions of varied particle size. The bioaccessibility of most PBDE congeners decreased with increasing dust particle size. The way of being of PBDE (adsorbed to dust surface or incorporated into polymers) in dust significantly influenced the bioaccessibility. There was a significant negative correlation between the tri- to hepta-BDE bioaccessibility and organic matter (OM) contents in dust. Furthermore, tri- to hepta-BDE bioaccessibility increased with increasing polarity of OMs, while with decreasing aromaticity of OMs. The tri- to hepta-BDE bioaccessibility significantly positively correlated with the surface areas and pore volumes of dust. Using multiple linear regression analysis, it was found that the OM contents and pore volumes of dust were the most important factors to influence the tri- to hepta-BDE bioaccessibility and they could be used to estimate the bioaccessibility of tri- to hepta-BDEs according to the following equation: bioaccessibility (%)=45.05-0.49 × OM%+1.79 × pore volume. However, BDE209 bioaccessibility did not correlate to any of these factors. Copyright © 2013 Elsevier Ltd. All rights reserved.

Application of Synchrotron Microprobe Methods to Solid-Phase Speciation of Metals and Metalloids in House Dust

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

S Walker; H Jamieson; P Rasmussen

2011-12-31

Determination of the source and form of metals in house dust is important to those working to understand human and particularly childhood exposure to metals in residential environments. We report the development of a synchrotron microprobe technique for characterization of multiple metal hosts in house dust. We have applied X-ray fluorescence for chemical characterization and X-ray diffraction for crystal structure identification using microfocused synchrotron X-rays at a less than 10 {micro}m spot size. The technique has been evaluated by application to archived house dust samples containing elevated concentrations of Pb, Zn, and Ba in bedroom dust, and Pb and Asmore » in living room dust. The technique was also applied to a sample of soil from the corresponding garden to identify linkages between indoor and outdoor sources of metals. Paint pigments including white lead (hydrocerussite) and lithopone (wurtzite and barite) are the primary source of Pb, Zn, and Ba in bedroom dust, probably related to renovation activity in the home at the time of sampling. The much lower Pb content in the living room dust shows a relationship to the exterior soil and no specific evidence of Pb and Zn from the bedroom paint pigments. The technique was also successful at confirming the presence of chromated copper arsenate treated wood as a source of As in the living room dust. The results of the study have confirmed the utility of this approach in identifying specific metal forms within the dust.« less

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

Gas Inside the 97 AU Cavity around the Transition Disk Sz 91

NASA Astrophysics Data System (ADS)

Canovas, H.; Schreiber, M. R.; Cáceres, C.; Ménard, F.; Pinte, C.; Mathews, G. S.; Cieza, L.; Casassus, S.; Hales, A.; Williams, J. P.; Román, P.; Hardy, A.

2015-05-01

We present ALMA (Cycle 0) band 6 and band 3 observations of the transition disk Sz 91. The disk inclination and position angle are determined to be i = 49.°5 ± 3.°5°and PA = 18.°2 ± 3.°5 and the dusty and gaseous disk are detected up to ˜220 and ˜400 AU from the star, respectively. Most importantly, our continuum observations indicate that the cavity size in the millimeter-sized dust distribution must be ˜97 AU in radius, the largest cavity observed around a T Tauri star. Our data clearly confirm the presence of 12CO (2-1) well inside the dust cavity. Based on these observational constraints we developed a disk model that simultaneously accounts for the 12CO and continuum observations (i.e., gaseous and dusty disk). According to our model, most of the millimeter emission comes from a ring located between 97 and 140 AU. We also find that the dust cavity is divided into an innermost region largely depleted of dust particles ranging from the dust sublimation radius up to 85 AU, and a second, moderately dust-depleted region, extending from 85 to 97 AU. The extremely large size of the dust cavity, the presence of gas and small dust particles within the cavity, and the accretion rate of Sz 91 are consistent with the formation of multiple (giant) planets.

On the Role of Dust in the Universe

NASA Astrophysics Data System (ADS)

Martin, P. G.

2004-05-01

This article is a personal discourse on the various aspects of dust in the universe, its so-called role. My conclusion is that dust does make a difference. It directly alters the way we view the universe. It also changes the nature of the universe that we see. Finally, it is woven into the big picture of our own place in the universe and our understanding and responses. In arriving at this conclusion I explore a range of topics: the curse of extinction, dust as a photon converter, diversity, Galactic ecology, and a cosmic bawdy house. I also reflect on dust and (in)humanity. I argue that we must advance the post-Copernican enlightenment, so that a coherent understanding of our place in the universe, the big picture, becomes widely held, to provide a basis for improving life here and now, bringing humans into harmony with one another, other living fauna and flora, and the shared environment. Countering pernicious trends to the contrary will require a social revolution to accompany the scientific, through ``ideas transfer.'' This is much more challenging than propagating technology. Astronomers, particularly those versed in the beauties and multiple dimensions of dust in the universe, have an opportunity to participate, indeed to intervene. Since ``dust is us,'' this too is a role of dust in the universe, arguably the most profound if it is accepted that continued human existence has any importance.

Combined Dust Detection Algorithm by Using MODIS Infrared Channels over East Asia

NASA Technical Reports Server (NTRS)

Park, Sang Seo; Kim, Jhoon; Lee, Jaehwa; Lee, Sukjo; Kim, Jeong Soo; Chang, Lim Seok; Ou, Steve

2014-01-01

A new dust detection algorithm is developed by combining the results of multiple dust detectionmethods using IR channels onboard the MODerate resolution Imaging Spectroradiometer (MODIS). Brightness Temperature Difference (BTD) between two wavelength channels has been used widely in previous dust detection methods. However, BTDmethods have limitations in identifying the offset values of the BTDto discriminate clear-sky areas. The current algorithm overcomes the disadvantages of previous dust detection methods by considering the Brightness Temperature Ratio (BTR) values of the dual wavelength channels with 30-day composite, the optical properties of the dust particles, the variability of surface properties, and the cloud contamination. Therefore, the current algorithm shows improvements in detecting the dust loaded region over land during daytime. Finally, the confidence index of the current dust algorithm is shown in 10 × 10 pixels of the MODIS observations. From January to June, 2006, the results of the current algorithm are within 64 to 81% of those found using the fine mode fraction (FMF) and aerosol index (AI) from the MODIS and Ozone Monitoring Instrument (OMI). The agreement between the results of the current algorithm and the OMI AI over the non-polluted land also ranges from 60 to 67% to avoid errors due to the anthropogenic aerosol. In addition, the developed algorithm shows statistically significant results at four AErosol RObotic NETwork (AERONET) sites in East Asia.

Probing the Extreme Environment of the Galactic Center with Observations from SOFIA/FORCAST

NASA Astrophysics Data System (ADS)

Lau, Ryan M.; Herter, Terry L.; Morris, Mark; Adams, Joseph D; Becklin, Eric E.

2014-06-01

In this thesis we present a study of the inner 40 pc of the Galactic center addressing the dense, dusty torus around Sgr A*, dust production around massive stars, and massive star formation. Observations of warm dust emission from the Galactic center were performed using the Faint Object Infrared Camera for the SOFIA Telescope (FORCAST). A dense, molecular torus referred to as the Circumnuclear Disk (CND) orbits Sgr A* with an inner radius of ~1.4 pc and extending to ~7 pc. The inner edge of the CND, which we refer to as the Circumnuclear Ring (CNR), exhibits features of a classic HII region and appears consistent with the prevailing paradigm in which the dust is heated by the Central cluster of hot, young stars. We do not detect any star formation occurring in the CNR; however, we reveal the presence of density “clumps” along the inner edge of the CNR. These clumps are not dense enough to be stable against tidal shear from Sgr A* and will be sheared out before completing a full orbit 10^5 yrs). Three Luminous Blue Variables (LBVs) are located in and near the Quintuplet Cluster 40 pc in projection from Sgr A*: qF362, the Pistol star, G0.120-0.048 (LBV3). FORCAST observation reveal the asymmetric, compressed shell of hot dust surrounding the Pistol Star and provide the first detection of the thermal emission from the symmetric, hot dust envelope surrounding LBV3. However, no detection of hot dust associated with qF362 is made. We argue that the Pistol star and LBV3 are identical “twins” that exhibit contrasting nebulae due to the external influence of their different environments. G-0.02-0.07, a complex consisting of three compact HII regions and one ultracompact HII region, is located at the edge of a molecular cloud 6 pc in projection to the east of Sgr A* and contains the most recent episode of star formation in the Galactic center. We probe the dust morphology, energetics, and composition of the regions to study the star forming conditions of a molecular cloud in the strong gravitational potential of Sgr A*.

Enhanced carrier multiplication in engineered quasi-type-II quantum dots

PubMed Central

Cirloganu, Claudiu M.; Padilha, Lazaro A.; Lin, Qianglu; Makarov, Nikolay S.; Velizhanin, Kirill A.; Luo, Hongmei; Robel, Istvan; Pietryga, Jeffrey M.; Klimov, Victor I.

2014-01-01

One process limiting the performance of solar cells is rapid cooling (thermalization) of hot carriers generated by higher-energy solar photons. In principle, the thermalization losses can be reduced by converting the kinetic energy of energetic carriers into additional electron-hole pairs via carrier multiplication (CM). While being inefficient in bulk semiconductors this process is enhanced in quantum dots, although not sufficiently high to considerably boost the power output of practical devices. Here we demonstrate that thick-shell PbSe/CdSe nanostructures can show almost a fourfold increase in the CM yield over conventional PbSe quantum dots, accompanied by a considerable reduction of the CM threshold. These structures enhance a valence-band CM channel due to effective capture of energetic holes into long-lived shell-localized states. The attainment of the regime of slowed cooling responsible for CM enhancement is indicated by the development of shell-related emission in the visible observed simultaneously with infrared emission from the core. PMID:24938462

Trans-Pacific transport of dust aerosols from East Asia: Insights gained from multiple observations and modeling.

PubMed

Guo, Jianping; Lou, Mengyun; Miao, Yucong; Wang, Yuan; Zeng, Zhaoliang; Liu, Huan; He, Jing; Xu, Hui; Wang, Fu; Min, Min; Zhai, Panmao

2017-11-01

East Asia is one of the world's largest sources of dust and anthropogenic pollution. Dust particles originating from East Asia have been recognized to travel across the Pacific to North America and beyond, thereby affecting the radiation incident on the surface as well as clouds aloft in the atmosphere. In this study, integrated analyses are performed focusing on one trans-Pacific dust episode during 12-22 March 2015, based on space-borne, ground-based observations, reanalysis data combined with Hybrid Single Particle Lagrangian Integrated Trajectory Model (HYSPLIT), and the Weather Research and Forecasting Model coupled with Chemistry (WRF-Chem). From the perspective of synoptic patterns, the location and strength of Aleutian low pressure system largely determined the eastward transport of dust plumes towards western North America. Multi-sensor satellite observations reveal that dust aerosols in this episode originated from the Taklimakan and Gobi Deserts. Moreover, the satellite observations suggest that the dust particles can be transformed to polluted particles over the East Asian regions after encountering high concentration of anthropogenic pollutants. In terms of the vertical distribution of polluted dust particles, at the very beginning, they were mainly located in the altitudes ranging from 1 km to 7 km over the source region, then ascended to 2 km-9 km over the Pacific Ocean. The simulations confirm that these elevated dust particles in the lower free troposphere were largely transported along the prevailing westerly jet stream. Overall, observations and modeling demonstrate how a typical springtime dust episode develops and how the dust particles travel over the North Pacific Ocean all the way to North America. Copyright © 2017 Elsevier Ltd. All rights reserved.

Assessments of the contribution of land use change to the dust emission in Central Asia

NASA Astrophysics Data System (ADS)

Xi, X.; Sokolik, I. N.

2015-12-01

While the dust emission from arid and semi-arid regions is known as a natural process induced by wind erosion, human may affect the dust emission directly through land use disturbances and indirectly by climate change. There has been much debate on the relative importance of climate change and land use to the global dust budget, as past estimates on the proportion of dust contributed by land use, in particular agricultural practices, remains very uncertain. This to the large extent stems from the way how human-made dust sources are identified and how they are treated in models. This study attempts to assess the land use contribution to the dust emission in Central Asia during 2000-2014 by conducting multiple experiments on the total emission in the WRF-Chem-DuMo model, and applying two methods to separate the natural and anthropogenic sources. The model experiments include realistic treatments of agriculture (e.g., expansion and abandonment) and water body changes (e.g., Aral Sea desiccation) in the land cover map of WRF-Chem-DuMo, but impose no arbitrary labeling of dust source type or adjustment to the erosion threshold. Intercomparison of the model experiments will be focused on the magnitude, interannual variability, and climate sensitivity of dust fluxes resulting from the selections of surface input data and dust flux parameterizations. Based on annual land use intensity maps, the sensitivity of the anthropogenic dust proportion to selection of the threshold value will be evaluated. In conjunction with the empirical method, satellite-derived annual land classifications will be used to track the land cover dynamics, and separate potential human-made source areas.

Nanolaminate Mirrors With "Piston" Figure-Control Actuators

NASA Technical Reports Server (NTRS)

Lowman, Andrew; Redding, David; Hickey, Gregory; Knight, Jennifer; Moynihan, Philip; Lih, Shyh0Shiuh; Barbee, Troy

2003-01-01

Efforts are under way to develop a special class of thin-shell curved mirrors for high-resolution imaging in visible and infrared light in a variety of terrestrial or extraterrestrial applications. These mirrors can have diameters of the order of a meter and include metallic film reflectors on nanolaminate substrates supported by multiple distributed piezoceramic gpiston h-type actuators for micron-level figure control. Whereas conventional glass mirrors of equivalent size and precision have areal mass densities between 50 and 150 kg/sq m, the nanolaminate mirrors, including not only the reflector/ shell portions but also the actuators and the backing structures needed to react the actuation forces, would have areal mass densities that may approach .5 kg/m2. Moreover, whereas fabrication of a conventional glass mirror of equivalent precision takes several years, the reflector/shell portion of a nanolaminate mirror can be fabricated in less than a week, and its actuation system can be fabricated in 1 to 2 months. The engineering of these mirrors involves a fusion of the technological heritage of multisegmented adaptive optics and deformable mirrors with more recent advances in metallic nanolaminates and in mathematical modeling of the deflections of thin, curved shells in response to displacements by multiple, distributed actuators. Because a nanolaminate shell is of the order of 10 times as strong as an otherwise identical shell made of a single, high-strength, non-nanolaminate metal suitable for mirror use, a nanolaminate mirror can be made very thin (typically between 100 and 150 m from the back of the nanolaminate substrate to the front reflecting surface). The thinness and strength of the nanolaminate are what make it possible to use distributed gpiston h-type actuators for surface figure control with minimal local concentrated distortion (called print-through in the art) at the actuation points.

A new approach to the method of source-sink potentials for molecular conduction

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

Pickup, Barry T., E-mail: B.T.Pickup@sheffield.ac.uk, E-mail: P.W.Fowler@sheffield.ac.uk; Fowler, Patrick W., E-mail: B.T.Pickup@sheffield.ac.uk, E-mail: P.W.Fowler@sheffield.ac.uk; Borg, Martha

2015-11-21

We re-derive the tight-binding source-sink potential (SSP) equations for ballistic conduction through conjugated molecular structures in a form that avoids singularities. This enables derivation of new results for families of molecular devices in terms of eigenvectors and eigenvalues of the adjacency matrix of the molecular graph. In particular, we define the transmission of electrons through individual molecular orbitals (MO) and through MO shells. We make explicit the behaviour of the total current and individual MO and shell currents at molecular eigenvalues. A rich variety of behaviour is found. A SSP device has specific insulation or conduction at an eigenvalue ofmore » the molecular graph (a root of the characteristic polynomial) according to the multiplicities of that value in the spectra of four defined device polynomials. Conduction near eigenvalues is dominated by the transmission curves of nearby shells. A shell may be inert or active. An inert shell does not conduct at any energy, not even at its own eigenvalue. Conduction may occur at the eigenvalue of an inert shell, but is then carried entirely by other shells. If a shell is active, it carries all conduction at its own eigenvalue. For bipartite molecular graphs (alternant molecules), orbital conduction properties are governed by a pairing theorem. Inertness of shells for families such as chains and rings is predicted by selection rules based on node counting and degeneracy.« less

Broadband absorption and enhanced photothermal conversion property of octopod-like Ag@Ag2S core@shell structures with gradually varying shell thickness.

PubMed

Jiang, Qian; Zeng, Wenxia; Zhang, Canying; Meng, Zhaoguo; Wu, Jiawei; Zhu, Qunzhi; Wu, Daxiong; Zhu, Haitao

2017-12-19

Photothermal conversion materials have promising applications in many fields and therefore they have attracted tremendous attention. However, the multi-functionalization of a single nanostructure to meet the requirements of multiple photothermal applications is still a challenge. The difficulty is that most nanostructures have specific absoprtion band and are not flexible to different demands. In the current work, we reported the synthesis and multi-band photothermal conversion of Ag@Ag 2 S core@shell structures with gradually varying shell thickness. We synthesized the core@shell structures through the sulfidation of Ag nanocubes by taking the advantage of their spatially different reactivity. The resulting core@shell structures show an octopod-like mopgorlogy with a Ag 2 S bulge sitting at each corner of the Ag nanocubes. The thickness of the Ag 2 S shell gradually increases from the central surface towards the corners of the structure. The synthesized core@shell structures show a broad band absorption spectrum from 300 to 1100 nm. Enhanced photothermal conversion effect is observed under the illuminations of 635, 808, and 1064 nm lasers. The results indicate that the octopod-like Ag@Ag 2 S core@shell structures have characteristics of multi-band photothermal conversion. The current work might provide a guidance for the design and synthesis of multifunctional photothermal conversion materials.

Consumer Product Chemicals in Indoor Dust: A Quantitative Meta-analysis of U.S. Studies

PubMed Central

2016-01-01

Indoor dust is a reservoir for commercial consumer product chemicals, including many compounds with known or suspected health effects. However, most dust exposure studies measure few chemicals in small samples. We systematically searched the U.S. indoor dust literature on phthalates, replacement flame retardants (RFRs), perfluoroalkyl substances (PFASs), synthetic fragrances, and environmental phenols and estimated pooled geometric means (GMs) and 95% confidence intervals for 45 chemicals measured in ≥3 data sets. In order to rank and contextualize these results, we used the pooled GMs to calculate residential intake from dust ingestion, inhalation, and dermal uptake from air, and then identified hazard traits from the Safer Consumer Products Candidate Chemical List. Our results indicate that U.S. indoor dust consistently contains chemicals from multiple classes. Phthalates occurred in the highest concentrations, followed by phenols, RFRs, fragrance, and PFASs. Several phthalates and RFRs had the highest residential intakes. We also found that many chemicals in dust share hazard traits such as reproductive and endocrine toxicity. We offer recommendations to maximize comparability of studies and advance indoor exposure science. This information is critical in shaping future exposure and health studies, especially related to cumulative exposures, and in providing evidence for intervention development and public policy. PMID:27623734

Light Scattering by Fractal Dust Aggregates. I. Angular Dependence of Scattering

NASA Astrophysics Data System (ADS)

Tazaki, Ryo; Tanaka, Hidekazu; Okuzumi, Satoshi; Kataoka, Akimasa; Nomura, Hideko

2016-06-01

In protoplanetary disks, micron-sized dust grains coagulate to form highly porous dust aggregates. Because the optical properties of these aggregates are not completely understood, it is important to investigate how porous dust aggregates scatter light. In this study, the light scattering properties of porous dust aggregates were calculated using a rigorous method, the T-matrix method, and the results were then compared with those obtained using the Rayleigh-Gans-Debye (RGD) theory and Mie theory with the effective medium approximation (EMT). The RGD theory is applicable to moderately large aggregates made of nearly transparent monomers. This study considered two types of porous dust aggregates—ballistic cluster-cluster agglomerates (BCCAs) and ballistic particle-cluster agglomerates. First, the angular dependence of the scattered intensity was shown to reflect the hierarchical structure of dust aggregates; the large-scale structure of the aggregates is responsible for the intensity at small scattering angles, and their small-scale structure determines the intensity at large scattering angles. Second, it was determined that the EMT underestimates the backward scattering intensity by multiple orders of magnitude, especially in BCCAs, because the EMT averages the structure within the size of the aggregates. It was concluded that the RGD theory is a very useful method for calculating the optical properties of BCCAs.

Characterization and Modeling of Dust Emissions from an Instrumented Mine Tailings Site

NASA Astrophysics Data System (ADS)

Betterton, E. A.; Stovern, M.; Saez, A.; Csavina, J. L.; Felix Villar, O. I.; Field, J. P.; Rine, K. P.; Russell, M. R.; Saliba, P.

2012-12-01

Mining operations are potential sources of airborne particulate metal and metalloid contaminants through both direct smelter emissions and wind erosion of mine tailings. The warmer, drier conditions predicted for the Southwestern US by climate models may make contaminated atmospheric dust and aerosols increasingly important, due to potential deleterious effects on human health and ecology. Dust emissions and dispersion of contaminants from the Iron King Mine tailings in Dewey-Humboldt, Arizona, a Superfund site, are currently being investigated through in situ field measurements and computational fluid dynamics modeling. These tailings are heavily contaminated with lead and arsenic. We report on the chemical characterization of atmospheric dust and aerosol sampled near the mine tailings. Instrumented eddy flux towers were also setup on the mine tailings to give both spatial and temporal dust observations. The eddy flux towers have multiple DUSTTRAK monitors as well as weather stations. These in situ observations allow us to assess spatial distribution of suspended particulate. Using the DUSTTRAK flux tower observations at 10-second resolution in conjunction with a computational fluid dynamics model, we have been able to model dust transport from the mine tailings to downwind areas. In order to improve the accuracy of the dust transport simulations both regional topographical features and local weather patterns have been incorporated into the model simulations.

LIGHT SCATTERING BY FRACTAL DUST AGGREGATES. I. ANGULAR DEPENDENCE OF SCATTERING

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

Tazaki, Ryo; Tanaka, Hidekazu; Okuzumi, Satoshi

2016-06-01

In protoplanetary disks, micron-sized dust grains coagulate to form highly porous dust aggregates. Because the optical properties of these aggregates are not completely understood, it is important to investigate how porous dust aggregates scatter light. In this study, the light scattering properties of porous dust aggregates were calculated using a rigorous method, the T -matrix method, and the results were then compared with those obtained using the Rayleigh–Gans–Debye (RGD) theory and Mie theory with the effective medium approximation (EMT). The RGD theory is applicable to moderately large aggregates made of nearly transparent monomers. This study considered two types of porousmore » dust aggregates—ballistic cluster–cluster agglomerates (BCCAs) and ballistic particle–cluster agglomerates. First, the angular dependence of the scattered intensity was shown to reflect the hierarchical structure of dust aggregates; the large-scale structure of the aggregates is responsible for the intensity at small scattering angles, and their small-scale structure determines the intensity at large scattering angles. Second, it was determined that the EMT underestimates the backward scattering intensity by multiple orders of magnitude, especially in BCCAs, because the EMT averages the structure within the size of the aggregates. It was concluded that the RGD theory is a very useful method for calculating the optical properties of BCCAs.« less

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

Zhu Zhaohuan; Dong Ruobing; Nelson, Richard P.

By carrying out two-dimensional two-fluid global simulations, we have studied the response of dust to gap formation by a single planet in the gaseous component of a protoplanetary disk-the so-called dust filtration mechanism. We have found that a gap opened by a giant planet at 20 AU in an {alpha} = 0.01, M-dot =10{sup -8} M{sub Sun} yr{sup -1} disk can effectively stop dust particles larger than 0.1 mm drifting inward, leaving a submillimeter (submm) dust cavity/hole. However, smaller particles are difficult to filter by a gap induced by a several M{sub J} planet due to (1) dust diffusion andmore » (2) a high gas accretion velocity at the gap edge. Based on these simulations, an analytic model is derived to understand what size particles can be filtered by the planet-induced gap edge. We show that a dimensionless parameter T{sub s} /{alpha}, which is the ratio between the dimensionless dust stopping time and the disk viscosity parameter, is important for the dust filtration process. Finally, with our updated understanding of dust filtration, we have computed Monte Carlo radiative transfer models with variable dust size distributions to generate the spectral energy distributions of disks with gaps. By comparing with transitional disk observations (e.g., GM Aur), we have found that dust filtration alone has difficulties depleting small particles sufficiently to explain the near-IR deficit of moderate M-dot transitional disks, except under some extreme circumstances. The scenario of gap opening by multiple planets studied previously suffers the same difficulty. One possible solution is to invoke both dust filtration and dust growth in the inner disk. In this scenario, a planet-induced gap filters large dust particles in the disk, and the remaining small dust particles passing to the inner disk can grow efficiently without replenishment from fragmentation of large grains. Predictions for ALMA have also been made based on all these scenarios. We conclude that dust filtration with planet(s) in the disk is a promising mechanism to explain submm observations of transitional disks but it may need to be combined with other processes (e.g., dust growth) to explain the near-IR deficit of some systems.« less

Drilling predation on molluscs in the northern Adriatic Sea: Spatial variability and temporal trends over the last millennia

NASA Astrophysics Data System (ADS)

Dengg, Markus; Wurzer, Sandra; Gallmetzer, Ivo; Haselmair, Alexandra; Zuschin, Martin

2016-04-01

Competition and predation are essential ecological factors influencing biodiversity. In a palaeontological context, the rate of predatory interactions between animal species is difficult to reconstruct because traces of predation are rarely incorporated into the fossil record. In the marine environment, the calcareous shells of molluscs, however, have good, long-time preservation potential, and predation in this group is often exerted by carnivorous gastropods that drill holes into mollusc shells. The prey's perforated shells remain in the sediment and can be used to study rates and intensities of predatory interactions in past marine molluscan communities. Differences in drilling frequencies along a sediment core not only reflect changes in local species richness and predation pressure, but may also mirror ecosystem changes through space and time. This makes the analysis of drilling predation an important tool when investigating the historical ecology of marine habitats. We used 1.5-m-long sediment cores from seven shelf locations spread throughout the northern Adriatic Sea basin to investigate regional and down-core variations in drilling frequencies. In total, about 54,000 bivalve and 40,000 gastropod shells were analysed to determine the following parameters: 1) overall drill frequency (DF), the proportion of shells drilled by predators; 2) edge drill frequency (EDF, only in bivalve shells), the proportion of shells with drilling traces at the shell edge; 3) multiple drill frequency (MDF), the percentage of individuals with more than one drill hole, 4) incomplete drill frequency (IDF), the percentage of shells unsuccessfully drilled; 5) prey effectiveness (PE), the proportion of individuals resisting the predator's attacks. Total drill frequency across all cores is 18% for bivalves and 13% for gastropods, but there are marked regional differences, with minima in the Po Delta (5%) and maxima in Panzano Bay (24%). Edge-drilled shells and multiple drill holes on single shells are very rare and occur on less than 1% of the investigated specimens. Also very low (< 1%) is the percentage of incomplete drill holes, except for the sampling location at the Brijuni Islands, Croatia (4%). Drilling frequencies show stronger differences between localities than along individual cores. Significant correlations exist between drilling intensities and prey species ecotype (especially for bivalves): commensals, parasitic and suspension-feeding species are more frequently drilled than other feeding types, as are infaunal species compared to species with epifaunal life habits. Despite the strong spatial variation in drilling intensities, the DF values of our samples are comparable to those typical for Cenozoic shelf environments.

Dust Tolerant Commodity Transfer Interface Mechanisms for Planetary Surfaces

NASA Technical Reports Server (NTRS)

Townsend, Ivan I.; Mueller, Robert P.; Tamasy, Gabor J.

2014-01-01

Regolith is present on most planetary surfaces such as Earth's moon, Mars, and Asteroids. If human crews and robotic machinery are to operate on these regolith covered surfaces, they must face the consequences of interacting with regolith fines which consist of particles below 100 microns in diameter down to as small as submicron scale particles. Such fine dust will intrude into mechanisms and interfaces causing a variety of problems such as contamination of clean fluid lines, jamming of mechanisms and damaging connector seals and couplings. Since multiple elements must be assembled in space for system level functionality, it will be inevitable that interfaces will be necessary for structural connections, and to pass commodities such as cryogenic liquid propellants, purge and buffer gases, water, breathing air, pressurizing gases, heat exchange fluids, power and data. When fine regolith dust is present in the environment it can be lofted into interfaces where it can compromise the utility of the interface by preventing the connections from being successfully mated, or by inducing fluid leaks or degradation of power and data transmission. A dust tolerant, hand held "quick-disconnect" cryogenic fluids connector housing has been developed at NASA KSC which can be used by astronaut crews to connect flex lines that will transfer propellants and other useful fluids to the end user. In addition, a dust tolerant, automated, cryogenic fluid, multiple connector, power and data interface mechanism prototype has been developed, fabricated and demonstrated by NASA at Kennedy Space Center (KSC). The design and operation of these prototypes are explained and discussed.

Do climate variables and human density affect Achatina fulica (Bowditch) (Gastropoda: Pulmonata) shell length, total weight and condition factor?

PubMed

Albuquerque, F S; Peso-Aguiar, M C; Assunção-Albuquerque, M J T; Gálvez, L

2009-08-01

The length-weight relationship and condition factor have been broadly investigated in snails to obtain the index of physical condition of populations and evaluate habitat quality. Herein, our goal was to describe the best predictors that explain Achatina fulica biometrical parameters and well being in a recently introduced population. From November 2001 to November 2002, monthly snail samples were collected in Lauro de Freitas City, Bahia, Brazil. Shell length and total weight were measured in the laboratory and the potential curve and condition factor were calculated. Five environmental variables were considered: temperature range, mean temperature, humidity, precipitation and human density. Multiple regressions were used to generate models including multiple predictors, via model selection approach, and then ranked with AIC criteria. Partial regressions were used to obtain the separated coefficients of determination of climate and human density models. A total of 1.460 individuals were collected, presenting a shell length range between 4.8 to 102.5 mm (mean: 42.18 mm). The relationship between total length and total weight revealed that Achatina fulica presented a negative allometric growth. Simple regression indicated that humidity has a significant influence on A. fulica total length and weight. Temperature range was the main variable that influenced the condition factor. Multiple regressions showed that climatic and human variables explain a small proportion of the variance in shell length and total weight, but may explain up to 55.7% of the condition factor variance. Consequently, we believe that the well being and biometric parameters of A. fulica can be influenced by climatic and human density factors.

Cauchy horizon stability in a collapsing spherical dust cloud: II. Energy bounds for test fields and odd-parity gravitational perturbations

NASA Astrophysics Data System (ADS)

Ortiz, Néstor; Sarbach, Olivier

2018-01-01

We analyze the stability of the Cauchy horizon associated with a globally naked, shell-focussing singularity arising from the complete gravitational collapse of a spherical dust cloud. In a previous work, we have studied the dynamics of spherical test scalar fields on such a background. In particular, we proved that such fields cannot develop any divergences which propagate along the Cauchy horizon. In the present work, we extend our analysis to the more general case of test fields without symmetries and to linearized gravitational perturbations with odd parity. To this purpose, we first consider test fields possessing a divergence-free stress-energy tensor satisfying the dominant energy condition, and we prove that a suitable energy norm is uniformly bounded in the domain of dependence of the initial slice. In particular, this result implies that free-falling observers co-moving with the dust particles measure a finite energy of the field, even as they cross the Cauchy horizon at points lying arbitrarily close to the central singularity. Next, for the case of Klein–Gordon fields, we derive point-wise bounds from our energy estimates which imply that the scalar field cannot diverge at the Cauchy horizon, except possibly at the central singular point. Finally, we analyze the behaviour of odd-parity, linear gravitational and dust perturbations of the collapsing spacetime. Similarly to the scalar field case, we prove that the relevant gauge-invariant combinations of the metric perturbations stay bounded away from the central singularity, implying that no divergences can propagate in the vacuum region. Our results are in accordance with previous numerical studies and analytic work in the self-similar case.

Most probable mixing state of aerosols in Delhi NCR, northern India

NASA Astrophysics Data System (ADS)

Srivastava, Parul; Dey, Sagnik; Srivastava, Atul Kumar; Singh, Sachchidanand; Tiwari, Suresh

2018-02-01

Unknown mixing state is one of the major sources of uncertainty in estimating aerosol direct radiative forcing (DRF). Aerosol DRF in India is usually reported for external mixing and any deviation from this would lead to high bias and error. Limited information on aerosol composition hinders in resolving this issue in India. Here we use two years of aerosol chemical composition data measured at megacity Delhi to examine the most probable aerosol mixing state by comparing the simulated clear-sky downward surface flux with the measured flux. We consider external, internal, and four combinations of core-shell (black carbon, BC over dust; water-soluble, WS over dust; WS over water-insoluble, WINS and BC over WINS) mixing. Our analysis reveals that choice of external mixing (usually considered in satellite retrievals and climate models) seems reasonable in Delhi only in the pre-monsoon (Mar-Jun) season. During the winter (Dec-Feb) and monsoon (Jul-Sep) seasons, 'WS coating over dust' externally mixed with BC and WINS appears to be the most probable mixing state; while 'WS coating over WINS' externally mixed with BC and dust seems to be the most probable mixing state in the post-monsoon (Oct-Nov) season. Mean seasonal TOA (surface) aerosol DRF for the most probable mixing states are 4.4 ± 3.9 (- 25.9 ± 3.9), - 16.3 ± 5.7 (- 42.4 ± 10.5), 13.6 ± 11.4 (- 76.6 ± 16.6) and - 5.4 ± 7.7 (- 80.0 ± 7.2) W m- 2 respectively in the pre-monsoon, monsoon, post-monsoon and winter seasons. Our results highlight the importance of realistic mixing state treatment in estimating aerosol DRF to aid in policy making to combat climate change.

A Year in the Life of an Infrared Echo

NASA Technical Reports Server (NTRS)

2005-01-01

[figure removed for brevity, see original site] Figure 1: Supernova Remnant Cassiopeia A One Year Apart

These Spitzer Space Telescope images, taken one year apart, show the supernova remnant Cassiopeia A (yellow ball) and surrounding clouds of dust (reddish orange). The pictures illustrate that a blast of light from Cassiopeia A is waltzing outward through the dusty skies. This dance, called an 'infrared echo,' began when the remnant erupted about 50 years ago.

Cassiopeia A is the remnant of a once massive star that died in a violent supernova explosion 325 years ago. It consists of a dead star, called a neutron star, and a surrounding shell of material that was blasted off as the star died. This remnant is located 10,000 light-years away in the northern constellation Cassiopeia.

Infrared echoes are created when a star explodes or erupts, flashing light into surrounding clumps of dust. As the light zips through the dust clumps, it heats them up, causing them to glow successively in infrared, like a chain of Christmas bulbs lighting up one by one. The result is an optical illusion, in which the dust appears to be flying outward at the speed of light. Echoes are distinct from supernova shockwaves, which are made up material that is swept up and hurled outward by exploding stars.

This infrared echo is the largest ever seen, stretching more than 50 light-years away from Cassiopeia A. If viewed from Earth, the entire movie frame would take up the same amount of space as two full moons.

Hints of an older infrared echo from Cassiopeia A's supernova explosion hundreds of years ago can also be seen.

The top Spitzer image was taken on November 30, 2003, and the bottom, on December 2, 2004.

Infrared Photometric Properties of 709 Candidate Stellar Bowshock Nebulae

NASA Astrophysics Data System (ADS)

Kobulnicky, Henry A.; Schurhammer, Danielle P.; Baldwin, Daniel J.; Chick, William T.; Dixon, Don M.; Lee, Daniel; Povich, Matthew S.

2017-11-01

Arcuate infrared nebulae are ubiquitous throughout the Galactic Plane and are candidates for partial shells, bubbles, or bowshocks produced by massive runaway stars. We tabulate infrared photometry for 709 such objects using images from the Spitzer Space Telescope, the Wide-field Infrared Explorer, and the Herschel Space Observatory (HSO). Of the 709 objects identified at 24 or 22 μm, 422 are detected at the HSO 70 μm bandpass. Of these, only 39 are detected at HSO 160 μm. The 70 μm peak surface brightnesses are 0.5-2.5 Jy arcmin-2. Color temperatures calculated from the 24 to 70 μm ratios range from 80 to 400 K. Color temperatures from 70 to 160 μm ratios are systematically lower, 40-200 K. Both of these temperature are, on average, 75% higher than the nominal temperatures derived by assuming that dust is in steady-state radiative equilibrium. This may be evidence of stellar wind bowshocks sweeping up and heating—possibly fragmenting but not destroying—interstellar dust. Infrared luminosity correlates with standoff distance, R 0, as predicted by published hydrodynamical models. Infrared spectral energy distributions are consistent with interstellar dust exposed to either single radiant energy density, U={10}3{--}{10}5 (in more than half of the objects) or a range of radiant energy densities U min = 25 to U max = 103-105 times the mean interstellar value for the remainder. Hence, the central OB stars dominate the energetics, making these enticing laboratories for testing dust models in constrained radiation environments. The spectral energy densities are consistent with polycyclic aromatic hydrocarbon fractions {q}{PAH}≲ 1 % in most objects.

Cross-shell excitations in Si 31

DOE PAGES

Tai, P. -L.; Tabor, S. L.; Lubna, R. S.; ...

2017-07-28

The Si-31 nucleus was produced through the O-18(18O, an) fusion-evaporation reaction at E-lab = 24 MeV. Evaporated a particles from the reaction were detected and identified in the Microball detector array for channel selection. Multiple gamma-ray coincidence events were detected in Gammasphere. The energy and angle information for the alpha particles was used to determine the Si-31 recoil kinematics on an event-by-event basis for a more accurate Doppler correction. A total of 22 new states and 52 new gamma transitions were observed, including 14 from states above the neutron separation energy. The positive-parity states predicted by the shell-model calculations inmore » the sd model space agree well with experiment. The negative-parity states were compared with shell-model calculations in the psdpf model space with some variations in the N = 20 shell gap. The best agreement was found with a shell gap intermediate between that originally used for A approximate to 20 nuclei and that previously adapted for P-32,P-34. This variation suggests the need for a more universal cross-shell interaction.« less

[Effect of the harvest season on the composition of raw and fermented cotyledons of 2 varieties of cacao and shell fractions].

PubMed

de Dios Alvarado, J; Villacís, F E; Zamora, G F

1983-06-01

A study was carried out wherein during the period August 1979 to January 1980, samples of raw and fermented cacao were analyzed monthly. These included two varieties: Arriba, taken from a farm in "Quevedo", and the EET-19, grown in "Pichilingüe" by the Instituto Nacional de Investigaciones Agropecuarias (INIAP). Taking the ear of cacao as a basis, the weight of its main parts was determined. The proximal composition was established in the cotyledons, with significant statistical differences in regard to moisture, protein, and ether extract content according to the month of harvest. As to the fermentation process, differences in moisture, ether extract and ash content were detected; differences in the ether extract and ash content were found between the two varieties. The fat extracted from the cotyledons presented different iodine, saponification and acidity index values between the raw and fermented samples, but none were determined between the varieties; as far as the month of harvest is concerned, differences in the acidity index were observed. The percentage composition of the main fatty acids is reported (palmitic, stearic, oleic, and linoleic acids). In order to suggest possible industrial ways of utilizing the cacao shell by-product which is discarded by the shelling machine, the chemical characteristics of five fractions were determined based on the functioning of the shelling machine. The moisture, protein, ether extract, ash, crude fiber, theobromine, and caffeine contents varied among the fractions, and it was dependent on the broken "nibs" content. Differences in the protein, ether extract, and ash content, according to the months of production, were found. Obviously, the high fat content in fractions A (fine dust) and B (fine ground), which varied from 30 to 11 g/100 g, merits its extraction; the remainder meal has a valuable protein and alkaloid content. The chemical characteristics of the fat extracted from the shell of two fractions were similar to the fat extracted from the cotyledons.

DUST EXTINCTION FROM BALMER DECREMENTS OF STAR-FORMING GALAXIES AT 0.75 {<=} z {<=} 1.5 WITH HUBBLE SPACE TELESCOPE/WIDE-FIELD-CAMERA 3 SPECTROSCOPY FROM THE WFC3 INFRARED SPECTROSCOPIC PARALLEL SURVEY

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

Dominguez, A.; Siana, B.; Masters, D.

Spectroscopic observations of H{alpha} and H{beta} emission lines of 128 star-forming galaxies in the redshift range 0.75 {<=} z {<=} 1.5 are presented. These data were taken with slitless spectroscopy using the G102 and G141 grisms of the Wide-Field-Camera 3 (WFC3) on board the Hubble Space Telescope as part of the WFC3 Infrared Spectroscopic Parallel survey. Interstellar dust extinction is measured from stacked spectra that cover the Balmer decrement (H{alpha}/H{beta}). We present dust extinction as a function of H{alpha} luminosity (down to 3 Multiplication-Sign 10{sup 41} erg s{sup -1}), galaxy stellar mass (reaching 4 Multiplication-Sign 10{sup 8} M {sub Sunmore » }), and rest-frame H{alpha} equivalent width. The faintest galaxies are two times fainter in H{alpha} luminosity than galaxies previously studied at z {approx} 1.5. An evolution is observed where galaxies of the same H{alpha} luminosity have lower extinction at higher redshifts, whereas no evolution is found within our error bars with stellar mass. The lower H{alpha} luminosity galaxies in our sample are found to be consistent with no dust extinction. We find an anti-correlation of the [O III] {lambda}5007/H{alpha} flux ratio as a function of luminosity where galaxies with L {sub H{alpha}} < 5 Multiplication-Sign 10{sup 41} erg s{sup -1} are brighter in [O III] {lambda}5007 than H{alpha}. This trend is evident even after extinction correction, suggesting that the increased [O III] {lambda}5007/H{alpha} ratio in low-luminosity galaxies is likely due to lower metallicity and/or higher ionization parameters.« less

A cloud collision model for water maser excitation.

PubMed

Tarter, J C; Welch, W J

1986-06-01

High-velocity collisions between small, dense, neutral clouds or between a dense cloud and a dense shell can provide the energy source required to excite H2O maser emission. The radiative precursor from the surface of the collisional shock front rapidly diffuses through the cloud, heating the dust grains but leaving the H2 molecules cool. Transient maser emission occurs as the conditions for the Goldreich and Kwan "hot-dust cold-gas" maser pump scheme are realized locally within the cloud. In time the local maser action quenches due to the heating of the H2 molecules by collisions against the grains. Although this model cannot explain the very long-lived steady maser features, it is quite successful in explaining a number of the observed properties of the high-velocity features in such sources as Orion, W51, and W49. In particular, it provides a natural explanation for the rapid time variations, the narrow line widths, juxtaposition of high- and low-velocity features, and the short lifetimes which are frequently observed for the so-called high-velocity maser "bullets" thought to be accelerated by strong stellar winds.

Microcrystals and Amorphous Material in Comets and Primitive Meteorites: Keys to Understanding Processes in the Early Solar System

NASA Technical Reports Server (NTRS)

Nuth, J. A.; Brearley, A. J.; Scott, E. R. D.

2004-01-01

Comets, fine-grained matrices of chondrites, and chondritic interplanetary dust particles (IDPs) are each composed of both crystalline and amorphous silicates. The primitive solar nebula, in which comets and asteroids accreted, was formed from the collapsed core of a Giant Molecular Cloud, that, in turn, condensed from materials present in the interstellar medium (ISM). Despite observations that reveal the presence of crystalline magnesium silicate minerals in the shells of very high mass-loss-rate stars [1,2], typical silicate grains in the ISM are most likely to be amorphous, given their relatively long residence time in such a high radiation environment. An upper limit of 3% crystalline grains can be derived from their non-detection in spectra of ISM solids [3]. If the vast majority of grains that enter the primitive solar nebula are amorphous, then the observation of crystalline dust in comets and primitive chondrite matrices indicates the action of specific processes required to transform the amorphous starting materials into the crystals that are observed.

An infrared ring around the magnetar SGR 1900+14.

PubMed

Wachter, S; Ramirez-Ruiz, E; Dwarkadas, V V; Kouveliotou, C; Granot, J; Patel, S K; Figer, D

2008-05-29

Magnetars are a special class of slowly rotating (period approximately 5-12 s) neutron stars with extremely strong magnetic fields (>10(14 )G)--at least an order of magnitude larger than those of the 'normal' radio pulsars. The potential evolutionary links and differences between these two types of object are still unknown; recent studies, however, have provided circumstantial evidence connecting magnetars with very massive progenitor stars. Here we report the discovery of an infrared elliptical ring or shell surrounding the magnetar SGR 1900+14. The appearance and energetics of the ring are difficult to interpret within the framework of the progenitor's stellar mass loss or the subsequent evolution of the supernova remnant. We suggest instead that a dust-free cavity was produced in the magnetar environment by the giant flare emitted by the source in August 1998. Considering the total energy released in the flare, the theoretical dust-destruction radius matches well with the observed dimensions of the ring. We conclude that SGR 1900+14 is unambiguously associated with a cluster of massive stars, thereby solidifying the link between magnetars and massive stars.

Mid-Infrared Long-Baseline Interferometry of the Symbiotic Mira Star RX Pup with the VLTI/MIDI Instrument

NASA Astrophysics Data System (ADS)

Driebe, T.; Hofmann, K.-H.; Ohnaka, K.; Schertl, D.; Weigelt, G.

2007-11-01

We present mid-infrared long-baseline interferometric observations of the symbiotic Mira star RX Pup obtained with the VLTI/MIDI instrument within the framework of the Science Demonstration Time (SDT) program in February 2004. Four visibility measurements have been carried out using the unit telescopes UT2 and UT3, with projected baseline lengths ranging from 34.7 to 46.5 m. All visibility measurements show a distinct wavelength dependence: a rather steep decrease between 8 and 10 μm, and a shallower monotonic increase longward of 10 μm. For the corresponding uniform disk diameter, this visibility shape translates into a diameter increase by a factor of 2 from 25 to 50 mas between 8 and 10 μm and an almost wavelength-independent diameter between 10 and 13 μm. As we show by means of radiative transfer modeling with the code dusty, this wavelength dependence measured with VLTI/MIDI can be interpreted as the mid-infrared signature of a circumstellar dust shell which is dominated by silicate dust.

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

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

Nag, Somnath; Singh, A. K.; Hagemann, G. B.

In this paper, high-spin states in 124Xe have been populated using the 80Se( 48Ca, 4n) reaction at a beam energy of 207 MeV and high-multiplicity, γ-ray coincidence events were measured using the Gammasphere spectrometer. Six high-spin rotational bands with moments of inertia similar to those observed in neighboring nuclei have been observed. The experimental results are compared with calculations within the framework of the Cranked Nilsson-Strutinsky model. Finally, it is suggested that the configurations of the bands involve excitations of protons across the Z = 50 shell gap coupled to neutrons within the N = 50 - 82 shell ormore » excited across the N = 82 shell closure.« less

THE IMPACT OF ACCURATE EXTINCTION MEASUREMENTS FOR X-RAY SPECTRAL MODELS

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

Smith, Randall K.; Valencic, Lynne A.; Corrales, Lia, E-mail: lynne.a.valencic@nasa.gov

Interstellar extinction includes both absorption and scattering of photons from interstellar gas and dust grains, and it has the effect of altering a source's spectrum and its total observed intensity. However, while multiple absorption models exist, there are no useful scattering models in standard X-ray spectrum fitting tools, such as XSPEC. Nonetheless, X-ray halos, created by scattering from dust grains, are detected around even moderately absorbed sources, and the impact on an observed source spectrum can be significant, if modest, compared to direct absorption. By convolving the scattering cross section with dust models, we have created a spectral model asmore » a function of energy, type of dust, and extraction region that can be used with models of direct absorption. This will ensure that the extinction model is consistent and enable direct connections to be made between a source's X-ray spectral fits and its UV/optical extinction.« less

Mars dust and cloud opacities and scattering properties

NASA Technical Reports Server (NTRS)

Clancy, R. T.; Lee, S. W.

1992-01-01

We have recently completed an analysis of the visible emission-phase function (EPF) sequences obtained with the solar-band channel of the Infrared Thermal Mapping (IRTM) instrument onboard the two Viking Orbiters. Roughly 100 of these EPF sequences were gathered during the 1977-1980 period, in which the total broadband (.3-3.0 microns) reflectances of the atmosphere/surface above specific locations on Mars were measured versus emission angle as the spacecraft passed overhead. A multiple scattering radiative transfer program was employed to model the EPF observations in terms of the optical depths of dust/clouds, their single scattering albedos and phase functions, and the Lambert albedos and phase coefficient of the underlying surfaces. Due to the predominance of atmospheric scattering at large atmospheric pathlengths and/or large dust opacities, we were able to obtain strong constraints on the scattering properties of dust/clouds and their opacities for a wide range of latitudes, longitudes, and seasons on Mars.

Hubble Hatches Image of Rotten Egg Nebula Shocks

NASA Technical Reports Server (NTRS)

2001-01-01

Some 5,000 light years (2,900 trillion miles) from Earth, in the constellation Puppis, is the 1.4 light years (more than 8 trillion miles) long Calabash Nebula, referred to as the Rotten Egg Nebula because of its sulfur content which would produce an awful odor if one could smell in space. This image of the nebula captured by NASA's Hubble Space Telescope (HST) depicts violent gas collisions that produced supersonic shock fronts in a dying star. Stars, like our sun, will eventually die and expel most of their material outward into shells of gas and dust These shells eventually form some of the most beautiful objects in the universe, called planetary nebulae. The yellow in the image depicts the material ejected from the central star zooming away at speeds up to one and a half million kilometers per hour (one million miles per hour). Due to the high speeds of the gas, shock-fronts are formed on impact and heat the surrounding gas. Although computer calculations have predicted the existence and structure of such shocks for some time, previous observations have not been able to prove the theory.

History of Hubble Space Telescope (HST)

NASA Image and Video Library

2001-08-24

Some 5,000 light years (2,900 trillion miles) from Earth, in the constellation Puppis, is the 1.4 light years (more than 8 trillion miles) long Calabash Nebula, referred to as the Rotten Egg Nebula because of its sulfur content which would produce an awful odor if one could smell in space. This image of the nebula captured by NASA's Hubble Space Telescope (HST) depicts violent gas collisions that produced supersonic shock fronts in a dying star. Stars, like our sun, will eventually die and expel most of their material outward into shells of gas and dust These shells eventually form some of the most beautiful objects in the universe, called planetary nebulae. The yellow in the image depicts the material ejected from the central star zooming away at speeds up to one and a half million kilometers per hour (one million miles per hour). Due to the high speeds of the gas, shock-fronts are formed on impact and heat the surrounding gas. Although computer calculations have predicted the existence and structure of such shocks for some time, previous observations have not been able to prove the theory.

BLOWING COSMIC BUBBLES

NASA Technical Reports Server (NTRS)

2002-01-01

This NASA Hubble Space Telescope image reveals an expanding shell of glowing gas surrounding a hot, massive star in our Milky Way Galaxy. This shell is being shaped by strong stellar winds of material and radiation produced by the bright star at the left, which is 10 to 20 times more massive than our Sun. These fierce winds are sculpting the surrounding material - composed of gas and dust - into the curve-shaped bubble. Astronomers have dubbed it the Bubble Nebula (NGC 7635). The nebula is 10 light-years across, more than twice the distance from Earth to the nearest star. Only part of the bubble is visible in this image. The glowing gas in the lower right-hand corner is a dense region of material that is getting blasted by radiation from the Bubble Nebula's massive star. The radiation is eating into the gas, creating finger-like features. This interaction also heats up the gas, causing it to glow. Scientists study the Bubble Nebula to understand how hot stars interact with the surrounding material. Credit: Hubble Heritage Team (AURA/STScI/NASA)

The spectrum of the variable planetary nebula IC 4997

NASA Technical Reports Server (NTRS)

Hyung, Siek; Aller, Lawrence H.; Feibelman, Walter A.

1994-01-01

The compact, dusty, presumably young planetary nebula (PN) IC 4997 has been studied extensively since the variability of the lambda 4363/lambda 4340 ratio was established in 1956. Since 1938, other nebular lines have shown changes. IC 4997 is also unique because of the great density range revealed by its spectrum which goes in excitation from Mg I to (Ar IV). We present a detailed listing of spectral lines from 360 to 1005 nm. The diagnostic diagram shows that the spectrum can be interpreted only in terms of strata with a huge density gamut. Essential spectral features can be reproduced approximately by a model consisting of a geometrically thin shell of density around 10(exp 7) atoms cm(exp -3), surrounded by a much larger shell with a density of about 10(exp 4) atoms cm(exp -3). The actual, certainly more complex structure can be evaluated only when high resolution spatial imaging is at hand. The usual method of getting abundances from N(ion)/N(H(+)) and ionization correction factors (ICFs) cannot be applied here. It is argued that a reasonable theoretical model that represents the spectrum provides a valid initial approximation to nebular abundances. We propose that the chemical composition of IC 4997 does not differ greatly from that of the Sun. The finally adopted model suggests that the ejection of the material destined to form the inner shell occurred between 1900 and 1960, but observational evidence of such an ejection event is lacking. Perhaps the shell was accelerated. A need for further study is emphasized, especially the role of dust which appears to contribute 2% of the total mass. More attention to this object is recommended. An accurate measurement of its distance is especially desirable.

A Multi-wavelength Study of Star Formation Activity in the S235 Complex

NASA Astrophysics Data System (ADS)

Dewangan, L. K.; Ojha, D. K.; Luna, A.; Anandarao, B. G.; Ninan, J. P.; Mallick, K. K.; Mayya, Y. D.

2016-03-01

We have carried out an extensive multi-wavelength study to investigate the star formation process in the S235 complex. The S235 complex has a spherelike shell appearance at wavelengths longer than 2 μm and harbors an O9.5V type star approximately at its center. A near-infrared extinction map of the complex traces eight subregions (having AV > 8 mag), and five of them appear to be distributed in an almost regularly spaced manner along the spherelike shell surrounding the ionized emission. This picture is also supported by the integrated 12CO and 13CO intensity maps and by Bolocam 1.1 mm continuum emission. The position-velocity analysis of CO reveals an almost semi-ringlike structure, suggesting an expanding H II region. We find that the Bolocam clump masses increase as we move away from the location of the ionizing star. This correlation is seen only for those clumps that are distributed near the edges of the shell. Photometric analysis reveals 435 young stellar objects (YSOs), 59% of which are found in clusters. Six subregions (including five located near the edges of the shell) are very well correlated with the dust clumps, CO gas, and YSOs. The average values of Mach numbers derived using NH3 data for three (East 1, East 2, and Central E) out of these six subregions are 2.9, 2.3, and 2.9, indicating these subregions are supersonic. The molecular outflows are detected in these three subregions, further confirming the ongoing star formation activity. Together, all these results are interpreted as observational evidence of positive feedback of a massive star.

The Spatial Distribution of Complex Organic Molecules in the L1544 Pre-stellar Core.

PubMed

Jiménez-Serra, Izaskun; Vasyunin, Anton I; Caselli, Paola; Marcelino, Nuria; Billot, Nicolas; Viti, Serena; Testi, Leonardo; Vastel, Charlotte; Lefloch, Bertrand; Bachiller, Rafael

2016-10-10

The detection of complex organic molecules (COMs) toward cold sources such as pre-stellar cores (with T<10 K), has challenged our understanding of the formation processes of COMs in the interstellar medium. Recent modelling on COM chemistry at low temperatures has provided new insight into these processes predicting that COM formation depends strongly on parameters such as visual extinction and the level of CO freeze out. We report deep observations of COMs toward two positions in the L1544 pre-stellar core: the dense, highly-extinguished continuum peak with A V ≥30 mag within the inner 2700 au; and a low-density shell with average A V ~7.5-8 mag located at 4000 au from the core's center and bright in CH 3 OH. Our observations show that CH 3 O, CH 3 OCH 3 and CH 3 CHO are more abundant (by factors ~2-10) toward the low-density shell than toward the continuum peak. Other COMs such as CH 3 OCHO, c-C 3 H 2 O, HCCCHO, CH 2 CHCN and HCCNC show slight enhancements (by factors ≤3) but the associated uncertainties are large. This suggests that COMs are actively formed and already present in the low-density shells of pre-stellar cores. The modelling of the chemistry of O-bearing COMs in L1544 indicates that these species are enhanced in this shell because i) CO starts freezing out onto dust grains driving an active surface chemistry; ii) the visual extinction is sufficiently high to prevent the UV photo-dissociation of COMs by the external interstellar radiation field; and iii) the density is still moderate to prevent severe depletion of COMs onto grains.

The Spatial Distribution of Complex Organic Molecules in the L1544 Pre-stellar Core

PubMed Central

Jiménez-Serra, Izaskun; Vasyunin, Anton I.; Caselli, Paola; Marcelino, Nuria; Billot, Nicolas; Viti, Serena; Testi, Leonardo; Vastel, Charlotte; Lefloch, Bertrand; Bachiller, Rafael

2016-01-01

The detection of complex organic molecules (COMs) toward cold sources such as pre-stellar cores (with T<10 K), has challenged our understanding of the formation processes of COMs in the interstellar medium. Recent modelling on COM chemistry at low temperatures has provided new insight into these processes predicting that COM formation depends strongly on parameters such as visual extinction and the level of CO freeze out. We report deep observations of COMs toward two positions in the L1544 pre-stellar core: the dense, highly-extinguished continuum peak with AV ≥30 mag within the inner 2700 au; and a low-density shell with average AV ~7.5-8 mag located at 4000 au from the core’s center and bright in CH3OH. Our observations show that CH3O, CH3OCH3 and CH3CHO are more abundant (by factors ~2-10) toward the low-density shell than toward the continuum peak. Other COMs such as CH3OCHO, c-C3H2O, HCCCHO, CH2CHCN and HCCNC show slight enhancements (by factors ≤3) but the associated uncertainties are large. This suggests that COMs are actively formed and already present in the low-density shells of pre-stellar cores. The modelling of the chemistry of O-bearing COMs in L1544 indicates that these species are enhanced in this shell because i) CO starts freezing out onto dust grains driving an active surface chemistry; ii) the visual extinction is sufficiently high to prevent the UV photo-dissociation of COMs by the external interstellar radiation field; and iii) the density is still moderate to prevent severe depletion of COMs onto grains. PMID:27733899

Correlation between diffusion kurtosis and NODDI metrics in neonates and young children

NASA Astrophysics Data System (ADS)

Ahmed, Shaheen; Wang, Zhiyue J.; Chia, Jonathan M.; Rollins, Nancy K.

2016-03-01

Diffusion Tensor Imaging (DTI) uses single shell gradient encoding scheme for studying brain tissue diffusion. NODDI (Neurite Orientation Dispersion and Density Imaging) incorporates a gradient scheme with multiple b-values which is used to characterize neurite density and coherence of neuron fiber orientations. Similarly, the diffusion kurtosis imaging also uses a multiple shell scheme to quantify non-Gaussian diffusion but does not assume a tissue model like NODDI. In this study we investigate the connection between metrics derived by NODDI and DKI in children with ages from 46 weeks to 6 years. We correlate the NODDI metrics and Kurtosis measures from the same ROIs in multiple brain regions. We compare the range of these metrics between neonates (46 - 47 weeks), infants (2 -10 months) and young children (2 - 6 years). We find that there exists strong correlation between neurite density vs. mean kurtosis, orientation dispersion vs. kurtosis fractional anisotropy (FA) in pediatric brain imaging.

High exposure to respirable dust and quartz in a labour-intensive coal mine in Tanzania.

PubMed

Mamuya, Simon H D; Bråtveit, Magne; Mwaiselage, Julius; Mashalla, Yohana J S; Moen, Bente E

2006-03-01

Labour-intensive mines are numerous in several developing countries, but dust exposure in such mines has not been adequately characterized. The aim of this study was to identify and quantify the determinants of respirable dust and quartz exposure among underground coal mine workers in Tanzania. Personal respirable dust samples (n = 134) were collected from 90 underground workers in June-August 2003 and July-August 2004. The development team had higher exposure to respirable dust and quartz (geometric means 1.80 and 0.073 mg m(-3), respectively) than the mining team (0.47 and 0.013 mg m(-3)), the underground transport team (0.14 and 0.006 mg m(-3)) and the underground maintenance team (0.58 and 0.016 mg m(-3)). The percentages of samples above the threshold limit values (TLVs) of 0.9 mg m(-3) for respirable bituminous coal dust and 0.05 mg m(-3) for respirable quartz, respectively, were higher in the development team (55 and 47%) than in the mining team (20 and 9%). No sample for the underground transport team exceeded the TLV. Drilling in the development was the work task associated with the highest exposure to respirable dust and quartz (17.37 and 0.611 mg m(-3), respectively). Exposure models were constructed using multiple regression model analysis, with log-transformed data on either respirable dust or quartz as the dependent variable and tasks performed as the independent variables. The models for the development section showed that blasting and pneumatic drilling times were major determinants of respirable dust and quartz, explaining 45.2 and 40.7% of the variance, respectively. In the mining team, only blasting significantly determined respirable dust. Immediate actions for improvements are suggested to include implementing effective dust control together with improved training and education programmes for the workers. Dust and quartz in this underground mine should be controlled by giving priority to workers performing drilling and blasting in the development sections of the mine.

Applying geochemical signatures of atmospheric dust to distinguish current mine emissions from legacy sources

NASA Astrophysics Data System (ADS)

Dong, Chenyin; Taylor, Mark Patrick

2017-07-01

Resolving the source of environmental contamination is the critical first step in remediation and exposure prevention. Australia's oldest silver-zinc-lead mine at Broken Hill (>130 years old) has generated a legacy of contamination and is associated with persistent elevated childhood blood lead (Pb) levels. However, the source of environmental Pb remains in dispute: current mine emissions; remobilized mine-legacy lead in soils and dusts; and natural lead from geological weathering of the gossan ore body. Multiple lines of evidence used to resolve this conundrum at Broken Hill include spatial and temporal variations in dust Pb concentrations and bioaccessibility, Pb isotopic compositions, particle morphology and mineralogy. Total dust Pb loading (mean 255 μg/m2/day) and its bioaccessibility (mean 75% of total Pb) is greatest adjacent to the active mining operations. Unweathered galena (PbS) found in contemporary dust deposits contrast markedly to Pb-bearing particles from mine-tailings and weathered gossan samples. Contemporary dust particles were more angular, had higher sulfur content and had little or no iron and manganese. Dust adjacent to the mine has Pb isotopic compositions (208Pb/207Pb: 2.3197; 206Pb/207Pb: 1.0406) that are a close match (99%) to the ore body with values slightly lower (94%) at the edge of the city. The weight of evidence supports the conclusion that contemporary dust Pb contamination in Broken Hill is sourced primarily from current mining activities and not from weathering or legacy sources.

Quality of life of coal dust workers without pneumoconiosis in mainland China.

PubMed

Yu, Hong-Mei; Ren, Xiao-Wei; Chen, Qian; Zhao, Jing-Yi; Zhu, Ting-Juan; Guo, Zhi-Xi

2008-01-01

The purpose of this cross-sectional study was to evaluate the quality of life (QOL) of coal dust workers without pneumoconiosis in mainland China. Three hundred five coal dust workers and 200 non-dust workers without pneumoconiosis from five coal mines in Shanxi province were enrolled in this study. The Chinese World Health Organization Quality of Life-brief version (WHOQOL-BREF) questionnaire was used. Socio-demographic, working, and health factors were also collected. Multiple stepwise regression analysis was used to identify significant factors related to the four domain scores of WHOQOL-BREF. All functional domains of the Chinese WHOQOL-BREF were significantly worse in coal dust workers compared to non-dust workers except for psychological health. For the physical domain of QOL, educational level, working hours, and work danger were the significant factors. In the psychological domain, types of job, welfare satisfaction, work danger, hobbies, smoking, one-child family, and marital status were the predictive factors. Working hours, welfare satisfaction, educational level, and birthplace were the predictive factors for the social domain of QOL. Finally, the predictors for the environmental domain of QOL were types of job, working hours, welfare satisfaction, work danger, self-reported social status, smoking, and drinking. Coal dust workers without pneumoconiosis had worse QOL than non-dust workers but their subjective feelings were positive. There were four distinct models for the various domains of QOL. Corresponding health policies could be developed to improve their QOL.

EXTENDED NEUTRAL HYDROGEN IN THE ALIGNED SHELL GALAXIES Arp 230 AND MCG -5-7-1: FORMATION OF DISKS IN MERGING GALAXIES?

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

Schiminovich, David; Van Gorkom, J. H.; Van der Hulst, J. M.

2013-02-01

As part of an ongoing study of the neutral hydrogen (H I) morphology and kinematics of 'shell' elliptical galaxies, we present Very Large Array observations of two shell galaxies with aligned shells, Arp 230 and MCG -5-7-1. Our data provide the first H I images of Arp 230 and deeper images of MCG -5-7-1 than previously reported. Optical images of Arp 230 reveal a bright, aligned, interleaved shell system, making it an ideal candidate for 'phase-wrapped' shell formation following a radial encounter with a smaller companion. The fainter, non-interleaved shells of MCG -5-7-1 do not clearly favor a particular formationmore » scenario. The H I we detect in both galaxies extends to nearly the same projected distance as the optical shells. In Arp 230 this gas appears to be anti-correlated with the aligned shells, consistent with our expectations for phase-wrapped shells produced in a radial encounter. In MCG -5-7-1, we observe gas associated with the shells making a 'spatial wrapping' or looping scenario more plausible. Although the extended gas component in both galaxies is unevenly distributed, the gas kinematics are surprisingly regular, looking almost like complete disks in rotation. We use the H I kinematics and optical data to determine mass-to-light ratios M/L{sub B} of 2.4{sup +3.0}{sub -0.5} (at 13.5 kpc, 4.5 R{sub e} ) for Arp 230 and M/L{sub B} of 30 {+-} 7 (at 40 kpc, 7 R{sub e} ) in MCG -5-7-1. In both systems we find that this ratio changes as a function of radius, indicating the presence of a dark halo. By comparing orbital and precession timescales, we conclude that the potentials are slightly flattened. We infer a 5%-10% flattening for Arp 230 and less flattening in the case of MCG -5-7-1. Finally, we present images of the H I associated with the inner disk or (polar) ring of each galaxy and discuss possible explanations for their different present-day star formation rates. We detect total H I masses of 1.1 Multiplication-Sign 10{sup 9} M{sub Sun} in Arp 230 and 3.7 Multiplication-Sign 10{sup 9} M{sub Sun} in MCG -5-7-1. Both systems have H I masses, scale sizes, and regular kinematics similar to those of non-aligned shell galaxies we have previously studied (Cen A and NGC 2865). Furthermore, we (re-)emphasize in this paper that shell galaxies such as MCG -5-7-1, along with previously studied galaxies NGC 5128 (Cen A) and NGC 2865, are unique in that they provide evidence of recent accretion with gas and collisionless stars showing clear association, though the displacement suggests the presence of significant gas-dynamical interaction.« less

Shell architecture: a novel proxy for paleotemperature reconstructions?

NASA Astrophysics Data System (ADS)

Milano, Stefania; Nehrke, Gernot; Wanamaker, Alan D., Jr.; Witbaard, Rob; Schöne, Bernd R.

2017-04-01

Mollusk shells are unique high-resolution paleoenvironmental archives. Their geochemical properties, such as oxygen isotope composition (δ18Oshell) and element-to-calcium ratios, are routinely used to estimate past environmental conditions. However, the existing proxies have certain drawbacks that can affect paleoreconstruction robustness. For instance, the estimation of water temperature of brackish and near-shore environments can be biased by the interdependency of δ18Oshell from multiple environmental variables (water temperature and δ18Owater). Likely, the environmental signature can be masked by physiological processes responsible for the incorporation of trace elements into the shell. The present study evaluated the use of shell structural properties as alternative environmental proxies. The sensitivity of shell architecture at µm and nm-scale to the environment was tested. In particular, the relationship between water temperature and microstructure formation was investigated. To enable the detection of potential structural changes, the shells of the marine bivalves Cerastoderma edule and Arctica islandica were analyzed with Scanning Electron Microscopy (SEM), nanoindentation and Confocal Raman Microscopy (CRM). These techniques allow a quantitative approach to the microstructural analysis. Our results show that water temperature induces a clear response in shell microstructure. A significant alteration in the morphometric characteristics and crystallographic orientation of the structural units was observed. Our pilot study suggests that shell architecture records environmental information and it has potential to be used as novel temperature proxy in near-shore and open ocean habitats.

Robust and Stable Cu Nanowire@Graphene Core-Shell Aerogels for Ultraeffective Electromagnetic Interference Shielding.

PubMed

Wu, Shiting; Zou, Mingchu; Li, Zhencheng; Chen, Daqin; Zhang, Hui; Yuan, Yongjun; Pei, Yongmao; Cao, Anyuan

2018-06-01

Cu nanowires (CuNWs) are considered as a promising candidate to develop high performance metal aerogels, yet the construction of robust and stable 3D porous structures remains challenging which severely limits their practical applications. Here, graphene-hybridized CuNW (CuNW@G) core-shell aerogels are fabricated by introducing a conformal polymeric coating and in situ transforming it into multilayered graphene seamlessly wrapped around individual CuNWs through a mild thermal annealing process. The existence of the outer graphene shell reinforces the 3D bulk structure and significantly slows down the oxidation process of CuNWs, resulting in improved mechanical property and highly stable electrical conductivity. When applied in electromagnetic interference shielding, the CuNW@G core-shell aerogels exhibit an average effectiveness of ≈52.5 dB over a wide range (from 8.2 to 18 GHz) with negligible degradation under ambient conditions for 40 d. Mechanism analysis reveals that the graphene shell with functional groups enables dual reflections on the core-shell and a multiple dielectric relaxation process, leading to enhanced dielectric loss and energy dissipation within the core-shell aerogels. The flexible core-shell-structured CuNW@G aerogels, with superior mechanical robustness and electrical stability, have potential applications in many areas such as advanced energy devices and functional composites. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Shell thickness-dependent microwave absorption of core-shell Fe3O4@C composites.

PubMed

Du, Yunchen; Liu, Wenwen; Qiang, Rong; Wang, Ying; Han, Xijiang; Ma, Jun; Xu, Ping

2014-08-13

Core-shell composites, Fe3O4@C, with 500 nm Fe3O4 microspheres as cores have been successfully prepared through in situ polymerization of phenolic resin on the Fe3O4 surface and subsequent high-temperature carbonization. The thickness of carbon shell, from 20 to 70 nm, can be well controlled by modulating the weight ratio of resorcinol and Fe3O4 microspheres. Carbothermic reduction has not been triggered at present conditions, thus the crystalline phase and magnetic property of Fe3O4 micropsheres can be well preserved during the carbonization process. Although carbon shells display amorphous nature, Raman spectra reveal that the presence of Fe3O4 micropsheres can promote their graphitization degree to a certain extent. Coating Fe3O4 microspheres with carbon shells will not only increase the complex permittivity but also improve characteristic impedance, leading to multiple relaxation processes in these composites, thus the microwave absorption properties of these composites are greatly enhanced. Very interestingly, a critical thickness of carbon shells leads to an unusual dielectric behavior of the core-shell structure, which endows these composites with strong reflection loss, especially in the high frequency range. By considering good chemical homogeneity and microwave absorption, we believe the as-fabricated Fe3O4@C composites can be promising candidates as highly effective microwave absorbers.

Constraining the Origin of Impact Craters on Al Foils from the Stardust Interstellar Dust Collector

NASA Technical Reports Server (NTRS)

Stroud, Rhonda M.; Achilles, Cheri; Allen, Carlton; Ansari, Asna; Bajt, Sasa; Bassim, Nabil; Bastien, Ron S.; Bechtel, H. A.; Borg, Janet; Brenker, Frank E.;

THE DUST ENVIRONMENT OF MAIN-BELT COMET P/2012 T1 (PANSTARRS)

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

Moreno, F.; Pozuelos, F.; Cabrera-Lavers, A.

2013-06-20

The Main-Belt Comet P/2012 T1 (PANSTARRS) has been imaged using the 10.4 m Gran Telescopio Canarias and the 4.2 m William Herschel Telescope at six epochs in the period from 2012 November to 2013 February, with the aim of monitoring its dust environment. The dust tails' brightness and morphology are best interpreted in terms of a model of sustained dust emission spanning four to six months. The total dust mass ejected is estimated at {approx}6-25 Multiplication-Sign 10{sup 6} kg. We assume a time-independent power-law size distribution function, with particles in the micrometer to centimeter size range. Based on the qualitymore » of the fits to the isophote fields, an anisotropic emission pattern is favored against an isotropic one, in which the particle ejection is concentrated toward high latitudes ({+-}45 Degree-Sign to {+-}90 Degree-Sign ) in a high-obliquity object (I = 80 Degree-Sign ). This seasonally driven ejection behavior, along with the modeled particle ejection velocities, are in remarkable agreement to those we found for P/2010 R2 (La Sagra).« less

AI canis minoris, a pulsating low-mass supergiant at an early transition phase from the AGB to the post-AGB stage of evolution

NASA Astrophysics Data System (ADS)

Arkhipova, V. P.; Ikonnikova, N. P.; Esipov, V. F.; Komissarova, G. V.

2017-06-01

The U BV photometry and low-resolution spectroscopy for the semiregular variable AI CMi, a candidate for post-AGB objects, performed in 1996-2016 and 2000-2013, respectively, are presented. The star showed multiperiodic brightness variations with an amplitude up to 1\\underset{\\cdot}{m} 5 in the V band, a significant (up to 0\\underset{\\cdot}{m} 4) bluing of the B - V and U - B colors as the star faded, and a change of its spectrum from G5 I to K3-5 I, depending on its brightness. A possible long-term fading of AI CMi below 8\\underset{\\cdot}{m} 5 in the period from May 2013 to early 2015 is observed in the light curve. The colors in this episode did not change the pattern of their unusual behavior with brightness. The main feature of the spectrum for AI CMi is the appearance and strengthening of TiO absorption bands as its brightness declines, which are atypical in the spectra of ordinary G5-K3 supergiants. The bluing of the B - V and U - B colors is interpreted as the blanketing of stellar radiation predominantly in V (and to a lesser extent in B) by the TiO absorption bands whose intensity increases dramatically with decreasing brightness. Another cause of the bluing can be the scattering of stellar radiation by small dust particles in the gas-dust shell of AI CMi. The star's continuum-normalized spectra over the period from 2000 to 2013 in the wavelength range 4200 to 7700 or 9200 Å are presented. These were taken at different phases of the pulsation cycle and clearly demonstrate the behavior of the TiO absorption bands depending on the V magnitude and B - V color. The equivalent widths of individual TiO bands weremeasured, and their correlation with the photometric parameters of the star is shown. AI CMi belongs to the O-rich branch of AGB/post-AGB supergiants and has a luminosity of 4000 L ⊙ at a distance of 1500 ± 700 pc. The mass of AI CMi is most likely small and close to the lower mass limit for post-AGB stars. The connection of the star's pulsational activity and nonstationary wind with the formation of its molecular and dust shells is discussed briefly.

Origin and diversity of testate amoebae shell composition: Example of Bullinularia indica living in Sphagnum capillifolium.

PubMed

Delaine, Maxence; Bernard, Nadine; Gilbert, Daniel; Recourt, Philippe; Armynot du Châtelet, Eric

2017-06-01

Testate amoebae are free-living shelled protists that build a wide range of shells with various sizes, shapes, and compositions. Recent studies showed that xenosomic testate amoebae shells could be indicators of atmospheric particulate matter (PM) deposition. However, no study has yet been conducted to assess the intra-specific mineral, organic, and biologic grain diversity of a single xenosomic species in a natural undisturbed environment. This study aims at providing new information about grain selection to develop the potential use of xenosomic testate amoebae shells as bioindicators of the multiple-origin mineral/organic diversity of their proximal environment. To fulfil these objectives, we analysed the shell content of 38 Bullinularia indica individuals, a single xenosomic testate amoeba species living in Sphagnum capillifolium, by scanning electron microscope (SEM) coupled with X-ray spectroscopy. The shells exhibited high diversities of mineral, organic, and biomineral grains, which confirms their capability to recycle xenosomes. Mineral grain diversity and size of B. indica matched those of the atmospheric natural mineral PM deposited in the peatbog. Calculation of grain size sorting revealed a discrete selection of grains agglutinated by B. indica. These results are a first step towards understanding the mechanisms of particle selection by xenosomic testate amoebae in natural conditions. Copyright © 2017 Elsevier GmbH. All rights reserved.

The influence of HCl concentration and demineralization temperature of Atrina pectinata shells on quality of chitin

NASA Astrophysics Data System (ADS)

Nugroho, Intan Lazuardi; Pursetyo, Kustiawan Tri; Masithah, Endang Dewi

2017-02-01

Atrina pectinata is one of shells species widely consumed by people, which means the high consumption will generate the availability of shells in the environment as waste. Chitin can be produced from the shells. Shells contain quite high minerals that it should be demineralized to reduce the mineral content from the shells. This study aimed to determine the effect of HCl concentration and temperature affect chitin characteristics as the result of demineralization process from pen shells. The method based on two steps, there were demineralization and deproteination. This study used Completely Randomized Design (CRD) with two factors, including HCl concentration (2N, 4N, and 6N) and temperature (33°C and 60°C) which consists six combination treatments and three replications. Data was analyzed by using Analysis of Variance (ANOVA) and followed by Duncan's Multiple Range Test. The results showed that interaction of HCl concentration and temperature has significant effect (p<0.05) to ash content of chitin. The use concentration of 6N and 33°C produced the lowest ash content. Characteristics chitin resulted from the treatment of 6N and 33°C produced ash content 25.33% ± 6.82, moisture content 3.67% ± 1.10, yield 0.72% ± 0.12 and protein content 5.86%.

In-Flight Aeroelastic Stability of the Thermal Protection System on the NASA HIAD, Part I: Linear Theory

NASA Technical Reports Server (NTRS)

Goldman, Benjamin D.; Dowell, Earl H.; Scott, Robert C.

2014-01-01

Conical shell theory and piston theory aerodynamics are used to study the aeroelastic stability of the thermal protection system (TPS) on the NASA Hypersonic Inflatable Aerodynamic Decelerator (HIAD). Structural models of the TPS consist of single or multiple orthotropic conical shell systems resting on several circumferential linear elastic supports. The shells in each model may have pinned (simply-supported) or elastically-supported edges. The Lagrangian is formulated in terms of the generalized coordinates for all displacements and the Rayleigh-Ritz method is used to derive the equations of motion. The natural modes of vibration and aeroelastic stability boundaries are found by calculating the eigenvalues and eigenvectors of a large coefficient matrix. When the in-flight configuration of the TPS is approximated as a single shell without elastic supports, asymmetric flutter in many circumferential waves is observed. When the elastic supports are included, the shell flutters symmetrically in zero circumferential waves. Structural damping is found to be important in this case. Aeroelastic models that consider the individual TPS layers as separate shells tend to flutter asymmetrically at high dynamic pressures relative to the single shell models. Several parameter studies also examine the effects of tension, orthotropicity, and elastic support stiffness.

Radio observations of globulettes in the Carina nebula

NASA Astrophysics Data System (ADS)

Haikala, L. K.; Gahm, G. F.; Grenman, T.; Mäkelä, M. M.; Persson, C. M.

2017-06-01

Context. The Carina nebula hosts a large number of globulettes. An optical study of these tiny molecular clouds shows that the majority are of planetary mass, but there are also those with masses of several tens up to a few hundred Jupiter masses. Aims: We seek to search for, and hopefully detect, molecular line emission from some of the more massive objects; in case of successful detection we aim to map their motion in the Carina nebula complex and derive certain physical properties. Methods: We carried out radio observations of molecular line emission in 12CO and 13CO (2-1) and (3-2) of 12 globulettes in addition to positions in adjacent shell structures using APEX. Results: All selected objects were detected with radial velocities shifted relative to the emission from related shell structures and background molecular clouds. Globulettes along the western part of an extended dust shell show a small spread in velocity with small velocity shifts relative to the shell. This system of globulettes and shell structures in the foreground of the bright nebulosity surrounding the cluster Trumpler 14 is expanding with a few km s-1 relative to the cluster. A couple of isolated globulettes in the area move at similar speed. Compared to similar studies of the molecular line emission from globulettes in the Rosette nebula, we find that the integrated line intensity ratios and line widths are very different. The results show that the Carina objects have a different density/temperature structure than those in the Rosette nebula. In comparison the apparent size of the Carina globulettes is smaller, owing to the larger distance, and the corresponding beam filling factors are small. For this reason we were unable to carry out a more detailed modelling of the structure of the Carina objects in the way as performed for the Rosette objects. Conclusions: The Carina globulettes observed are compact and denser than objects of similar mass in the Rosette nebula. The distribution and velocities of these globulettes suggest that they have originated from eroding shells and elephant trunks. Some globulettes in the Trumpler 14 region are quite isolated and located far from any shell structures. These objects move at a similar speed as the globulettes along the shell, suggesting that they once formed from cloud fragments related to the same foreground shell. Based on observations collected with the Atacama Pathfinder Experiment (APEX), Llano Chajnantor, Chile (O-091.F-9316A and O-094.F-9312A).The final reduced radio data (FITS format) are available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/602/A61

The Lunar Environment: Determining the Health Effects of Exposure to Moon Dusts

NASA Technical Reports Server (NTRS)

Khan-Mayberry, Noreen

2007-01-01

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 dust capable of entering habitats and vehicle compartments, where it can result in crewmember health problems. During the Apollo missions, lunar dusts 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 dust, NASA formed the Lunar Airborne Dust 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 dusts, including an extremely fine respirable component. These dusts 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 dusts has surface properties that are unlike any Earth based analog. These distinctive properties are why lunar dusts are of great toxicological interest. Understanding how these reactive components 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 dusts will determine the human risk criteria for lunar dust exposure and produce a lunar health standard. LADTAG s analysis of lunar dusts and lunar dust simulants will include detailed lunar particle characterizations, determining the properties of particle activation, reactivation of lunar dust, the process of dust passivation and discerning the pathology of lunar dust exposure via inhalation, intratracheal instillation, cell culture exposure, dermal exposure and ocular exposure. The resulting health standard will be time-based and will vary by the duration and type of exposure. It may also be necessary to set multiple standards for different types of lunar dust, as well as for dust in its activated form vs. aged & passivated dust. This standard, set to protect the health of our robust astronaut crews, will not only impact NASA medical operations, but engineering designs as well. The data from our multidisciplinary research are vital in developing remediation devices and environmental monitors. Ultimately, the engineering and safety groups will design and develop countermeasures for space vehicles, suits, rovers and habitats that will be sustained within the limits of the health standard.

Use of Probability Distribution Functions for Discriminating Between Cloud and Aerosol in Lidar Backscatter Data

NASA Technical Reports Server (NTRS)

Liu, Zhaoyan; Vaughan, Mark A.; Winker, Davd M.; Hostetler, Chris A.; Poole, Lamont R.; Hlavka, Dennis; Hart, William; McGill, Mathew

2004-01-01

In this paper we describe the algorithm hat will be used during the upcoming Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) mission for discriminating between clouds and aerosols detected in two wavelength backscatter lidar profiles. We first analyze single-test and multiple-test classification approaches based on one-dimensional and multiple-dimensional probability density functions (PDFs) in the context of a two-class feature identification scheme. From these studies we derive an operational algorithm based on a set of 3-dimensional probability distribution functions characteristic of clouds and aerosols. A dataset acquired by the Cloud Physics Lidar (CPL) is used to test the algorithm. Comparisons are conducted between the CALIPSO algorithm results and the CPL data product. The results obtained show generally good agreement between the two methods. However, of a total of 228,264 layers analyzed, approximately 5.7% are classified as different types by the CALIPSO and CPL algorithm. This disparity is shown to be due largely to the misclassification of clouds as aerosols by the CPL algorithm. The use of 3-dimensional PDFs in the CALIPSO algorithm is found to significantly reduce this type of error. Dust presents a special case. Because the intrinsic scattering properties of dust layers can be very similar to those of clouds, additional algorithm testing was performed using an optically dense layer of Saharan dust measured during the Lidar In-space Technology Experiment (LITE). In general, the method is shown to distinguish reliably between dust layers and clouds. The relatively few erroneous classifications occurred most often in the LITE data, in those regions of the Saharan dust layer where the optical thickness was the highest.

Records of River Variation in the Shells of Freshwater Bivalves

NASA Astrophysics Data System (ADS)

Carroll, M.; Romanek, C.

2005-12-01

The skeletons of hard-shelled invertebrates such as corals and bivalves are commonly used in marine settings as archives of environmental information. They are less commonly used in freshwater settings where variability in water chemistry makes it more difficult to calibrate chemical proxies such as the Sr:Ca in a shell. Our objective is to evaluate whether trace element concentrations in freshwater bivalve shells contain information on environmental conditions. Multiple elements (Ba, Cu, Mn and Sr) were analyzed within the shells of modern bivalves from four streams on DOE's Savannah River Site in S.C. Laser Ablation ICP-MS was used to measure elemental concentrations across five aragonitic shells from each site. These elements were chosen because they are present in detectable concentrations (ppm) in the shell and they have been suggested as useful proxies for temperature, rainfall, productivity and pollution. Results were compared to historical monthly site records of water chemistry and chemical analyses of water samples collected from the streams where the clams were found. The average shell concentrations of Sr and Mn were significantly different between sites and increased proportionally to water concentration. This was not observed for Ba and Cu. For example, the Ba concentrations of shells collected at a site downstream of a lake were higher than those for shells from stream sites with significantly higher dissolved Ba concentrations. Copper was only detected at dark growth lines with the number of lines and shell material between them varying between shells within the same stream. Intrashell profiles of Ba, Sr and Mn concentrations exhibited cyclical variation. The magnitude of cyclical variation for Mn and Sr within a shell corresponds with the annual variation in monthly water sample concentrations. Again, this pattern was not observed for Ba, especially in shells from the site downstream of a lake. This supports suggestions that particulate organic matter, to which Ba preferentially partitions, plays a role in bivalve Ba uptake. Finally, variations in Ba, Cu, Mn and Sr profiles across shells are not in unison. The individual elemental responses to biological and physicochemical effects suggest that the elemental records in freshwater bivalve shells can be interpreted as environmental proxies.

Field measurements of horizontal forward motion velocities of terrestrial dust devils: Towards a proxy for ambient winds on Mars and Earth

NASA Astrophysics Data System (ADS)

Balme, M. R.; Pathare, A.; Metzger, S. M.; Towner, M. C.; Lewis, S. R.; Spiga, A.; Fenton, L. K.; Renno, N. O.; Elliott, H. M.; Saca, F. A.; Michaels, T. I.; Russell, P.; Verdasca, J.

2012-11-01

Dust devils - convective vortices made visible by the dust and debris they entrain - are common in arid environments and have been observed on Earth and Mars. Martian dust devils have been identified both in images taken at the surface and in remote sensing observations from orbiting spacecraft. Observations from landing craft and orbiting instruments have allowed the dust devil translational forward motion (ground velocity) to be calculated, but it is unclear how these velocities relate to the local ambient wind conditions, for (i) only model wind speeds are generally available for Mars, and (ii) on Earth only anecdotal evidence exists that compares dust devil ground velocity with ambient wind velocity. If dust devil ground velocity can be reliably correlated to the ambient wind regime, observations of dust devils could provide a proxy for wind speed and direction measurements on Mars. Hence, dust devil ground velocities could be used to probe the circulation of the martian boundary layer and help constrain climate models or assess the safety of future landing sites. We present results from a field study of terrestrial dust devils performed in the southwest USA in which we measured dust devil horizontal velocity as a function of ambient wind velocity. We acquired stereo images of more than a 100 active dust devils and recorded multiple size and position measurements for each dust devil. We used these data to calculate dust devil translational velocity. The dust devils were within a study area bounded by 10 m high meteorology towers such that dust devil speed and direction could be correlated with the local ambient wind speed and direction measurements. Daily (10:00-16:00 local time) and 2-h averaged dust devil ground speeds correlate well with ambient wind speeds averaged over the same period. Unsurprisingly, individual measurements of dust devil ground speed match instantaneous measurements of ambient wind speed more poorly; a 20-min smoothing window applied to the ambient wind speed data improves the correlation. In general, dust devils travel 10-20% faster than ambient wind speed measured at 10 m height, suggesting that their ground speeds are representative of the boundary layer winds a few tens of meters above ground level. Dust devil ground motion direction closely matches the measured ambient wind direction. The link between ambient winds and dust devil ground velocity demonstrated here suggests that a similar one should apply on Mars. Determining the details of the martian relationship between dust devil ground velocity and ambient wind velocity might require new in situ or modelling studies but, if completed successfully, would provide a quantitative means of measuring wind velocities on Mars that would otherwise be impossible to obtain.