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1

Electron microscopy of atmospheric particles  

NASA Astrophysics Data System (ADS)

Electron microscopy coupled with energy dispersive spectrometry (EM/EDS) is a powerful tool for single particle analysis. However, the accuracy with which atmospheric particle compositions can be quantitatively determined by EDS is often hampered by substrate-particle interactions, volatilization losses in the low pressure microscope chamber, electron beam irradiation and use of inaccurate quantitation factors. A pseudo-analytical solution was derived to calculate the temperature rise due to the dissipation of the electron energy on a particle-substrate system. Evaporative mass loss for a spherical cap-shaped sulfuric acid particle resting on a thin film supported by a TEM grid during electron beam impingement has been studied. Measured volatilization rates were found to be in very good agreement with theoretical predictions. The method proposed can also be used to estimate the vapor pressure of a species by measuring the decay of X-ray intensities. Several types of substrates were studied. We found that silver-coated silicon monoxide substrates give carbon detection limits comparable to commercially available substrates. An advantage of these substrates is that the high thermal conductivity of the silver reduces heating due to electron beam impingement. In addition, exposure of sulfuric acid samples to ammonia overnight substantially reduces sulfur loss in the electron beam. Use of size-dependent k-factors determined from particles of known compositions shows promise for improving the accuracy of atmospheric particle compositions measured by EM/EDS. Knowledge accumulated during the course of this thesis has been used to analyze atmospheric particles (Minneapolis, MN) selected by the TDMA and collected by an aerodynamic focusing impactor. 'Less' hygroscopic particles, which do not grow to any measurable extent when humidified to ~90% relative humidity, included chain agglomerates, spheres, flakes, and irregular shapes. Carbon was the predominant element detected in these particles. The 'more' hygroscopic particles appear to be liquid spheres and contained sulfur, oxygen, and sometimes cations such as sodium and potassium. In addition, carbon was sometimes found in the more hygroscopic particles.

Huang, Po-Fu

2

Spontaneous fission of atmospheric aerosol particles  

NASA Astrophysics Data System (ADS)

We show that spontaneous division of atmospheric aerosol particles is thermodynamically possible, in spite of the corresponding increase in surface area, when there is a highly compressed organic surfactant coating on the particle. This class of atmospheric aerosol is thought to be present (and potentially important) in both marine and urban atmospheres. Fully-coated particles have been suggested to have played a role in the origin of cell-based life. The possibility of their spontaneous division has important implications for atmospheric chemistry, radiative transfer and the evolution of life on Earth.

Donaldson, D.; Tuck, A. F.; Vaida, V.

2002-05-01

3

Particle Formation (Nucleation) in the Martian Atmosphere  

NASA Astrophysics Data System (ADS)

We have studied ice particle formation via heterogeneous nucleation in the present atmospheric conditions of Mars for both one-component (water OR carbon dioxide) and two-component (water AND carbon dioxide) cases.

Määttänen, A.; Vehkamäki, H.; Lauri, A.; Napari, I.; Merikallio, S.; Kauhanen, J.; Savijärvi, H.; Kulmala, M.

2006-10-01

4

Particle precipitation impacts on the atmosphere  

NASA Astrophysics Data System (ADS)

Understanding the Earth's climate system and how it responds to changes is one of the largest challenges faced by society. Being able to understand past climate and to better predict how the Earth's climate will change in the future requires good understanding of both natural and anthropogenic sources of climate forcing. In addition to solar irradiance, energetic particle forcing from the Sun can have a significant impact on the atmosphere, with the effect being focused on the polar regions. This presentation will focus on this type of solar forcing and discuss the influence of energetic particle precipitation (EPP) on the polar atmosphere. During solar storms the level of particle precipitation into the atmosphere can increase by several orders of magnitude, and some level of EPP is nearly continuously present. In the atmosphere EPP causes ionisation in the middle atmosphere (20-100 km). This effect is confined to polar regions, where particles are guided by the geomagnetic field. In the atmosphere enhanced ionisation leads to increased production of NOx and HOx. These are gases, which participate in catalytic ozone destruction. HOx has a short-lived effect on the atmosphere; NOx on the other hand is mainly destroyed by photodissociation. Hence during polar winter, when little or no sunlight is present, NOx impact on the atmosphere can be long lasting. For example, following a series of solar storms in 2003, a 60% ozone depletion in the Arctic upper stratosphere was observed a month after the storms. Consequently, the EPP effect on the atmosphere has the potential to be long lasting (months to years). Dynamical coupling mechanisms between atmospheric layers can further provide coupling between this form of space weather and lower atmosphere and thus have indirect implications to polar climate. Recently, the analysis of meteorological data and chemistry-climate model results have indicated that during the winter season polar surface temperatures show variability depending on the level of NOx produced by EPP. Understanding this link between particle forcing from the Sun and climate requires a close examination of the dynamical and chemical coupling mechanisms connecting particle forcing driven changes in the atmosphere to changes in climate variables. In addition, the characteristics of EPP, particularly the energy spectrum and precipitation fluxes of electrons, crucial in determining the initial impact on atmosphere, are not well known.

Seppälä, A.

2012-04-01

5

Vapor scavenging by atmospheric aerosol particles  

SciTech Connect

Particle growth due to vapor scavenging was studied using both experimental and computational techniques. Vapor scavenging by particles is an important physical process in the atmosphere because it can result in changes to particle properties (e.g., size, shape, composition, and activity) and, thus, influence atmospheric phenomena in which particles play a role, such as cloud formation and long range transport. The influence of organic vapor on the evolution of a particle mass size distribution was investigated using a modified version of MAEROS (a multicomponent aerosol dynamics code). The modeling study attempted to identify the sources of organic aerosol observed by Novakov and Penner (1993) in a field study in Puerto Rico. Experimentally, vapor scavenging and particle growth were investigated using two techniques. The influence of the presence of organic vapor on the particle`s hydroscopicity was investigated using an electrodynamic balance. The charge on a particle was investigated theoretically and experimentally. A prototype apparatus--the refractive index thermal diffusion chamber (RITDC)--was developed to study multiple particles in the same environment at the same time.

Andrews, E.

1996-05-01

6

Alternative pathway for atmospheric particles growth  

PubMed Central

Credible climate change predictions require reliable fundamental scientific knowledge of the underlying processes. Despite extensive observational data accumulated to date, atmospheric aerosols still pose key uncertainties in the understanding of Earth’s radiative balance due to direct interaction with radiation and because they modify clouds’ properties. Specifically, major gaps exist in the understanding of the physicochemical pathways that lead to aerosol growth in the atmosphere and to changes in their properties while in the atmosphere. Traditionally, the driving forces for particle growth are attributed to condensation of low vapor pressure species following atmospheric oxidation of volatile compounds by gaseous oxidants. The current study presents experimental evidence of an unaccounted-for new photoinduced pathway for particle growth. We show that heterogeneous reactions activated by light can lead to fast uptake of noncondensable Volatile Organic Compounds (VOCs) at the surface of particles when only traces of a photosensitizer are present in the seed aerosol. Under such conditions, size and mass increase; changes in the chemical composition of the aerosol are also observed upon exposure to volatile organic compounds such as terpenes and near-UV irradiation. Experimentally determined growth rate values match field observations, suggesting that this photochemical process can provide a new, unaccounted-for pathway for atmospheric particle growth and should be considered by models.

Monge, Maria Eugenia; Rosen?rn, Thomas; Favez, Olivier; Muller, Markus; Adler, Gabriela; Abo Riziq, Ali; Rudich, Yinon; Herrmann, Hartmut; George, Christian; D'Anna, Barbara

2012-01-01

7

Mode resolved density of atmospheric aerosol particles  

NASA Astrophysics Data System (ADS)

In this study, we investigate the mode resolved density of ultrafine atmospheric particles measured in boreal forest environment. The method used here enables us to find the distinct density information for each mode in atmospheric fine particle population: the density values for nucleation, Aitken, and accumulation mode particles are presented. The experimental data was gained during 2 May 2005 19 May 2005 at the boreal forest measurement station "SMEAR II" in Hyytiälä, Southern Finland. The density values for accumulation mode varied from 1.1 to 2 g/cm3 (average 1.5 g/cm3) and for Aitken mode from 0.4 to 2 g/cm3 (average 0.97 g/cm3). As an overall trend during the two weeks campaign, the density value of Aitken mode was seen to gradually increase. With the present method, the time dependent behaviour of the particle density can be investigated in the time scale of 10 min. This allows us to follow the density evolution of the nucleation mode particles during the particle growth process following the nucleation burst. The density of nucleation mode particles decreased during the growth process. The density values for 15 nm particles were 1.2 1.5 g/cm3 and for grown 30 nm particles 0.5 1 g/cm3. These values are consistent with the present knowledge that the condensing species are semi-volatile organics, emitted from the boreal forest.

Kannosto, J.; Virtanen, A.; Lemmetty, M.; Mäkelä, J. M.; Keskinen, J.; Junninen, H.; Hussein, T.; Aalto, P.; Kulmala, M.

2008-09-01

8

Mode resolved density of atmospheric aerosol particles  

NASA Astrophysics Data System (ADS)

In this study, we investigate the mode resolved density of ultrafine atmospheric particles measured in boreal forest environment. The method used here enables us to find the distinct density information for each mode in atmospheric fine particle population: the density values for nucleation, Aitken, and accumulation mode particles are presented. The experimental data was gained during 2 May 2005-19 May 2005 at the boreal forest measurement station "SMEAR II" in Hyytiälä, southern Finland. The density values for accumulation mode varied from 1.1 to 2 g/cm3 (average 1.5 g/cm3) and for Aitken mode from 0.4 to 2 g/cm3 (average 0.97 g/cm3. As an overall trend during the two weeks campaign, the density value of Aitken mode was seen to gradually increase. With the present method, the time dependent behaviour of the particle density can be investigated in time scale of 10 min. This allows us the follow the density evolution of the nucleation mode particles during the particle growth process following the nucleation burst. The density of nucleation mode particles decreased during the growth process. The density values for 15 nm particles were 1.2-1.5 g/cm3 and for grown 30 nm particles 0.5-1 g/cm3. These values are consistent with the present knowledge that the condensing species are semi volatile organics, emitted from the Boreal forest.

Kannosto, J.; Lemmetty, M.; Virtanen, A.; Mäkelä, J. M.; Keskinen, J.; Junninen, H.; Hussein, T.; Aalto, P.; Kulmala, M.

2008-04-01

9

Phase of atmospheric secondary organic material affects its reactivity  

PubMed Central

The interconversion of atmospheric organic particles among solid, semisolid, and liquid phases is of keen current scientific interest, especially for particles of secondary organic material (SOM). Herein, the influence of phase on ammonia uptake and subsequent particle-phase reactions was investigated for aerosol particles of adipic acid and ?-pinene ozonolysis SOM. The nitrogen content of the particles was monitored by online mass spectrometry for increasing ammonia exposure. Solid and semisolid adipic acid particles were inert to the ammonia uptake for low RH (< 5%). For the solid particles, ammonia exposure at high relative humidity (RH; > 94%) induced a first-order deliquescence phase transition into aqueous particles. Solid particles exposed to supersaturated (RH > 100%) conditions and cycled back to high RH (> 94%), thereby becoming acidic metastable particles, underwent a gradual second-order transition upon ammonia exposure to form aqueous, partially neutralized particles. For ?-pinene SOM, ammonia exposure at low RH increased the particle-phase ammonium content by a small amount. Mass spectrometric observations suggest a mechanism of neutralization and co-condensation of acidic gas-phase species, consistent with a highly viscous semisolid upon which adsorption occurs. At high RH the ammonium content increased greatly, indicative of rapid diffusion and absorption in a liquid environment. The mass spectra indicated the production of organonitrogen compounds, possibly by particle-phase reactive chemistry. The present results demonstrate that phase can be a key regulator of the reactivity of atmospheric SOM particles.

Kuwata, Mikinori; Martin, Scot T.

2012-01-01

10

Characterization of Atmospheric Organic Nitrates in Particles  

NASA Astrophysics Data System (ADS)

Aerosols in the atmosphere significantly affect climate, human health and visibility. Knowledge of aerosol composition is necessary to understand and then predict the specific impacts of aerosols in the atmosphere. It is known that organic nitrates are present in particles, but there is limited knowledge of the individual compounds and quantity. This is in part due to the lack of a wide variety of proven analytical techniques for particulate organic nitrates. In this study, several known organic nitrates, as well as those present in complex mixtures formed from oxidation of "Ñ-pinene, were studied using a variety of techniques. These include Fourier Transform infrared spectroscopy (FTIR) of samples collected by impaction on ZnSe discs. Samples were also collected on quartz fiber filters and the extracts analyzed by electrospray mass spectrometry (ESI- MS), atmospheric pressure chemical ionization mass spectrometry (APCI-MS), HPLC-UV, LC-MS and GC-MS. In addition, real-time analysis was provided by SPLAT-II and aerosol mass spectrometry (AMS). FTIR analysis of particles collected on ZnSe discs provides information on the ratio of organic nitrate to total organic content, while the analysis of filter extracts allows identification of specific organic nitrates. These are compared to the particle mass spectrometry data and the implications for detecting and measuring particulate organic nitrate in air is discussed.

Bruns, E. A.; Alexander, M. L.; Perraud, V.; Yu, Y.; Ezell, M.; Johnson, S. N.; Zellenyuk, A.; Imre, D.; Finlayson-Pitts, B. J.

2008-12-01

11

Particle Suspension Mechanisms - Supplemental Material  

SciTech Connect

This supplemental material provides a brief introduction to particle suspension mechanisms that cause exfoliated skin cells to become and remain airborne. The material presented here provides additional context to the primary manuscript and serves as background for designing possible future studies to assess the impact of skin cells as a source of infectious aerosols. This introduction is not intended to be comprehensive and interested readers are encouraged to consult the references cited.

Dillon, M B

2011-03-03

12

[Discovery of anatase in atmospheric inhalable particles and its significance].  

PubMed

Laser Raman microprobe (LRM) is a reliable technique for phase identification to analyze the molecular composition and microstructure on 1 microm2 area of samples, and therefore, it is well-suited for identifying the mineral phases of single fine particles. In the present paper, we utilized LRM to identify the mineral phases of the single inhalable particles (PM10) from samples in Beijing City and compared the Raman microscopic spectra of samples with the standard spectra of mineral and inorganic material of Renishaw's database. Then we confirmed, for the first time, that the mineral phase of Ti-rich particles in the environmental atmosphere is the anatase TiO2, whose Raman spectrum has a strong O-Ti-O band at 638 cm(-1) and two medium O-Ti-O bands at 398 and 517 cm(-1) respectively. Thus it ensures the existence of TiO2 particles in PM10. Anatase is an important photocatalyst which can speed up the heterogeneous reaction between mineral particles, especially the calcium carbonates, when carried by these particles. Furthermore, the crystal structure of anatase, relative humidity of environment and the surface pH value can significantly influence the photocatalysis of anatase in atmosphere. PMID:19810533

Zheng, Nan; Wang, He-Jin

2009-06-01

13

Apparatus for Studying Atmospheric Degradation of Materials.  

National Technical Information Service (NTIS)

A simple, flexible test facility has been devised which is suitable for examining the effects of trace gases on the degradation of materials under conditions approximating to those of free atmospheric exposure. (Author)

K. E. Johnson A. F. Bromley

1973-01-01

14

Partitioning of atmospheric particle-in-cell models to multiprocessors  

Microsoft Academic Search

A design methodology for developing a multiprocessor computer system to solve atmospheric Particle in Cell models was formulated. The atmospheric Particle in Cell model is a subset of the class of fluid dynamics problems called Particle in Cell (PIC). The PIC class of problems requires very large data arrays to track the flow of mass through a two or three

B. S. Lawver

1982-01-01

15

ATMOSPHERIC PROCESSES AND EFFECTS ON MATERIALS  

EPA Science Inventory

These two chapters summarize the effects expected from the depletion of stratospheric ozone by the presence of CFCs. he two areas considered by these two reports are materials damage and atmospheric processes. ncreased UV can affect materials in the following ways: (1) corrosion ...

16

Chemistry and composition of atmospheric aerosol particles.  

PubMed

For more than two decades a cadre of physical chemists has focused on understanding the formation processes, chemical composition, and chemical kinetics of atmospheric aerosol particles and droplets with diameters ranging from a few nanometers to ?10,000 nm. They have adapted or invented a range of fundamental experimental and theoretical tools to investigate the thermochemistry, mass transport, and chemical kinetics of processes occurring at nanoscale gas-liquid and gas-solid interfaces for a wide range of nonideal, real-world substances. State-of-the-art laboratory methods devised to study molecular spectroscopy, chemical kinetics, and molecular dynamics also have been incorporated into field measurement instruments that are deployed routinely on research aircraft, ships, and mobile laboratories as well as at field sites from megacities to the most remote jungle, desert, and polar locations. These instruments can now provide real-time, size-resolved aerosol particle physical property and chemical composition data anywhere in Earth's troposphere and lower stratosphere. PMID:22404591

Kolb, Charles E; Worsnop, Douglas R

2012-01-30

17

Images reveal that atmospheric particles can undergo liquid-liquid phase separations  

SciTech Connect

A large fraction of submicron atmospheric particles contains both organic material and inorganic salts. As the relative humidity cycles in the atmosphere, these mixed particles can undergo a range of phase transitions, possibly including liquid-liquid phase separation. If liquid-liquid phase separation occurs, the gas-particle partitioning of atmospheric semi-volatile organic compounds, the scattering and absorption of solar radiation, and the uptake of reactive gas species on atmospheric particles will be affected, with important implications for climate predictions. The actual occurrence of these types of phase transitions within individual atmospheric particles has been considered uncertain, in large part because of the absence of observations for real-world samples. Here, using optical and fluorescence microscopy, we observe the coexistence of two non-crystalline phases in particles generated from real-world samples collected on multiple days in Atlanta, Georgia, and in particles generated in the laboratory using atmospheric conditions. These results reveal that atmospheric particles can undergo liquid-liquid phase separations. Using a box model, we show that liquid-liquid phase separation can result in increased concentrations of gas-phase NO3 and N2O5 in the Atlanta region, due to decreased particle uptake of N2O5.

You, Yuan; Renbaum-Wolff, Lindsay; Carreras-Sospedra, Marc; Hanna, Sarah; Hiranuma, Naruki; Kamal, Saeid; Smith, Mackenzie L.; Zhang, Xiaolu; Weber, Rodney; Shilling, John E.; Dabdub, Donald; Martin, Scot T.; Bertram, Allan K.

2012-07-30

18

Images reveal that atmospheric particles can undergo liquid-liquid phase separations  

PubMed Central

A large fraction of submicron atmospheric aerosol particles contains both organic material and inorganic salts. As the relative humidity cycles in the atmosphere and the water content of the particles correspondingly changes, these mixed particles can undergo a range of phase transitions, possibly including liquid–liquid phase separation. If liquid–liquid phase separation occurs, the gas-particle partitioning of atmospheric semivolatile organic compounds, the scattering and absorption of solar radiation, and the reactive uptake of gas species on atmospheric particles may be affected, with important implications for climate predictions. The actual occurrence of liquid–liquid phase separation within individual atmospheric particles has been considered uncertain, in large part because of the absence of observations for real-world samples. Here, using optical and fluorescence microscopy, we present images that show the coexistence of two noncrystalline phases for real-world samples collected on multiple days in Atlanta, GA as well as for laboratory-generated samples under simulated atmospheric conditions. These results reveal that atmospheric particles can undergo liquid–liquid phase separations. To explore the implications of these findings, we carried out simulations of the Atlanta urban environment and found that liquid–liquid phase separation can result in increased concentrations of gas-phase NO3 and N2O5 due to decreased particle uptake of N2O5.

You, Yuan; Renbaum-Wolff, Lindsay; Carreras-Sospedra, Marc; Hanna, Sarah J.; Hiranuma, Naruki; Kamal, Saeid; Smith, Mackenzie L.; Zhang, Xiaolu; Weber, Rodney J.; Shilling, John E.; Dabdub, Donald; Martin, Scot T.; Bertram, Allan K.

2012-01-01

19

Energetic charged-particle interactions with atmospheres and surfaces  

Microsoft Academic Search

The surfaces of interstellar and interplanetary grains, planetary satellites, ring particles, asteroids, Mercury and the Moon, etc. are all directly exposed to radiation bombardment, as are the upper atmospheres of the planets and large satellites. The sources of this radiation include the solar wind, magnetospheric plasmas, cosmic rays, solar energetic particles and U.V. photons. The interaction of these particles with

R. E. Johnson

1990-01-01

20

Interaction between SO 2 and submicron atmospheric particles  

Microsoft Academic Search

In the atmosphere, oxidation of sulfur dioxide (SO2) to sulfate may occur in the gas phase, in cloud or fog droplets, or in the aerosol phase on the surface or inside aerosol particles. While aerosol phase reactions have been studied in the case of supermicron sea-salt and crustal particles, very few investigations regarding submicron particles are available. In this paper,

Veli-Matti Kerminen; Liisa Pirjola; Michael Boy; Arkke Eskola; Kimmo Teinilä; Lauri Laakso; Ari Asmi; Jukka Hienola; Antti Lauri; Veera Vainio; Kari Lehtinen; Markku Kulmala

2000-01-01

21

Effects of Particle Beams in the Solar Atmosphere  

NASA Astrophysics Data System (ADS)

This work addresses the observational and physical effects of particle beams in the solar atmosphere. Mainly electron beams are considered. Describing acceleration mechanisms of superthermal particles, the main attention is devoted to effects influencing the particle beam propagation. The collisional energy losses and pitch angle scattering, the return current effects, and the mirroring in the converging magnetic field in specific situations are considered. Furthermore, the processes connected with the particle beam bombardment of dense layers of the solar atmosphere are briefly described. Finally, some open questions are summarized.

Karlicky, M.

22

Compound Identification of Atmospheric Particles. Final Report, October 1980.  

National Technical Information Service (NTIS)

This study tested the usefulness of several modern surface analytic techniques for compound identification of atmospheric particles, emphasis being on sulfur species. Using scanning electron microscopy (SEM) and x-ray fluorescence (energy dispersive x-ray...

D. Lichtman

1980-01-01

23

Highly charged cloud particles in the atmosphere of Venus  

Microsoft Academic Search

The accumulation of charges on cloud particles by the charge transfer of ions and attachment of electrons in the atmosphere of Venus is investigated in the present work. Three cloud layers between 45 and 70 km exist in the atmosphere of Venus. Ions and electrons are produced by the interaction of galactic cosmic rays with the neutral molecules. Ion to

Marykutty Michael; Sachchida Nand Tripathi; W. J. Borucki; R. C. Whitten

2009-01-01

24

Material flammability in space exploration atmospheres  

NASA Astrophysics Data System (ADS)

In order to reduce the risk of decompression sickness associated with extravehicular activity, NASA is designing the next generation of exploration vehicles with a different cabin pressure and oxygen concentration than used previously. This work explores how the flammability of solid materials changes in this new environment. One method to evaluate material flammability is by its ease of ignition. To this end, piloted ignition delay tests were conducted in a small-scale wind tunnel subject to this new space exploration atmosphere (SEA -- 58.6 kPa and 32% oxygen) and compared to similar tests in standard atmospheric conditions. In these tests, polymethylmethacylate (PMMA) was exposed to a range of oxidizer flow velocities and externally applied heat fluxes. It was found that the ignition time was reduced by 27% in the intended space exploration atmosphere. It was also noted that the critical heat flux for ignition decreases in exploration atmospheres. These results show that materials are more susceptible to ignition than in current spacecraft atmospheres. To further explore the effect of pressure and oxygen concentration, tests were performed for a wide range of pressures and oxygen concentrations. In all oxygen concentrations tested, the ignition delay time was seen to decrease with pressure, reach a minimum, and then increase with further reduction in pressure creating a classic u-shaped curve. No ignition was seen at sufficiently low pressures. The no ignition pressure depended on the oxygen concentration. Increasing the oxygen concentration uniformly decreases the ignition time; however, no significant differences were seen in oxygen concentrations above 24%. These results indicate there are several competing mechanisms controlling the ignition time. By reducing the pressure, the heat transfer coefficient and the mass flow rate of fuel to reach the lean flammability limit are reduced. Conversely, a reduction in pressure increases the gas-phase chemical induction time. The competition between these three mechanisms is responsible for the u-shaped dependence of ignition time on total pressure. In addition to gaining insight into the effect of pressure on piloted ignition, these results have practical applications including high altitude structures and airplane cabins.

McAllister, Sara Suzanne

25

The effect of atmospheric pollution on building materials  

NASA Astrophysics Data System (ADS)

This chapter surveys main effects of atmospheric pollution on building materials. It summarises these effects on stone, bricks, mortar, concrete, glass, metals (iron, zinc, copper, bronze, aluminium, lead and silver), polymers, paints and timber. Special attention is paid to stone because of its extensive use as building material in the cultural heritage. In general, main damaging agent is sulfur dioxide which leads to sulfation of many materials, particularly carbonate-bearing stones. However, the decline of sulfur dioxide in cities means that the recognition of the prime role of this pollutant presents something of a dilemma. It is increasingly necessary to consider other substances that can contribute to material decay e.g. nitrogen oxides, chlorides and ozone, either acting as synergistic to the sulfation reaction or as main decay agents, such as the case of aluminium and polymers. Particulate matter often from diesel vehicles can also accelerate the oxidation of SO2 on the surface (traditionally sulfur dioxide with Fe-rich particles) and blacken the materials surface in the case of soot. These processes contribute to the formation of black-crusts when embedded in the gypsum layer resulting from the material sulfation, but again the rate in the modem atmosphere is a matter of much research.

Grossi, C. M.; Brimblecombe, P.

2002-11-01

26

Aerosol formation: atmospheric particles from organic vapours.  

PubMed

Aerosol particles produced over forested areas may affect climate by acting as nuclei for cloud condensation, but their composition (and hence the chemical species that drive their production) remains an open question. Here we show, to our knowledge for the first time, that these newly formed particles (3-5 nm in diameter) are composed primarily of organic species, such as cis-pinonic acid and pinic acid, produced by oxidation of terpenes in organic vapours released from the canopy. PMID:11932734

O'Dowd, Colin D; Aalto, Pasi; Hmeri, Kaarle; Kulmala, Markku; Hoffmann, Thorsten

2002-04-01

27

The radiation in the atmosphere during major solar particle events  

NASA Astrophysics Data System (ADS)

Major solar particle events can give rise to greatly enhanced radiation throughout the entire atmosphere including at aircraft altitudes. These particle events are very hard to predict and their effect on aircraft is difficult to calculate. A comprehensive model of the energetic radiation in the atmosphere has been developed based on a response matrix of the atmosphere to energetic particle incidence. This model has previously been used to determine the spectral form of several ground level neutron events including February 1956 and September/October 1989. Significant validation of the model has been possible using CREAM data flying onboard Concorde during the September/October 1989 events. Further work has been carried out for the current solar maximum, including estimates of the solar particle spectra during the July 2000, April 2001, and October 2003 events and comparisons of predicted atmospheric measurements with limited flight data. Further CREAM data have been obtained onboard commercial airlines and high altitude business jets during quiet time periods. In addition, the atmospheric radiation model, along with solar particle spectra, have been used to calculate the neutron flux and dose rates along several commercial aircraft flight paths including London to Los Angeles. The influence of rigidity cut-off suppression by geomagnetic storms is examined and shows that the received flight dose during disturbed periods can be significantly enhanced compared with quiet periods.

Clucas, Simon N.; Dyer, Clive S.; Lei, Fan

28

The radiation in the atmosphere during major solar particle events  

NASA Astrophysics Data System (ADS)

Major solar particle events can give rise to greatly enhanced radiation throughout the entire atmosphere including at aircraft altitudes. These particle events are very hard to predict and their effect on aircraft is difficult to calculate. A comprehensive model of the energetic radiation in the atmosphere has been developed based on a response matrix of the atmosphere to energetic particle incidence. This model has previously been used to determine the spectral form of several ground level neutron events including February 56 and September/October 1989. Significant validation of the model has been possible using CREAM data flying onboard Concorde during the September/October 1989 events. Further work has been carried out for this solar maximum, including estimates of the solar particle spectra during the July 2000, April 2001, and October 2003 events and comparisons of predicated atmospheric measurements with limited flight data. Further CREAM data has being obtained onboard commercial airlines and high altitude business jets during quiet time periods. In addition, the atmospheric radiation model, along with solar particle spectra, have been used to calculate the neutron flux and dose rates along several commercial aircraft flight paths including London - LA. The influence of suppression on cut-off rigidity by geomagnetic storms is examined and shows that the received flight dose during disturbed periods can be significantly enhanced compared with quiet periods.

Clucas, S.; Dyer, C.; Lei, F.

29

Charged and Neutral Particle Interactions on Aerospace Materials  

SciTech Connect

Various candidate aircraft and spacecraft materials were analyzed and compared in a neutron environment using the Monte Carlo N-Particle (MCNP) transport code and in Galactic Cosmic Ray (GCR) and Trapped environments using the HZETRN code. These candidate materials are being used in aerospace vehicles, have been tested in particle beams, or seemed reasonable to analyze in this manner before deciding to manufacture and test them. This analysis shows that hydrogen bearing materials are better than the metal alloys for reducing the number of reflected and transmitted particles. It also shows that neutrons above 1 MeV are reflected out of the face of the slab better when larger quantities of carbon are present in the material. If a neutron absorber is added to the material, fewer neutrons are transmitted through and reflected from the material. This analysis focused on combinations of scatterers and absorbers to optimize these reaction channels on the higher energy neutron component. The absorber addition did not substantially change the charged particle transmission from the value obtained for polyethylene. The ultimate goal of this type of analysis is the selection of a layered material or material type that will optimize dose, dose equivalent, and electronic error rates inside the vehicle (and outside the vehicle if necessary for the mission). This analysis focuses on how the different material types and additives behave in the atmospheric and space related particle fields. As a secondary issue, as the amount of hydrogen bearing materials increase, larger fluxes of thermal neutrons are expected. It has been observed experimentally that large thicknesses of hydrogen bearing materials increase the error rates per neutron that occurs in SRAM memory chips. This effect is still being investigated, but it has been narrowed down to the larger mean neutron energy produced by the hydrogen bearing material. (authors)

Singleterry, R.C. Jr.; Thibeault, Sheila A. [NASA Langley Research Center, Hampton, VA 23681 (United States); Wilkins, Richard; Huff, Harold [Center for Applied Radiation Research, Prairie View A and M University, Prairie View, TX 77446 (United States)

2002-07-01

30

Some inner physical properties of material particles  

Microsoft Academic Search

It is shown that the Maxwell equations, which usually apply only outside material particles, apply also inside, giving standing or trapped wave solutions, both for electromagnetic field and for charge and current densities. The quantum mechanical function and the amplitude u-function apply inside and outside particles.

Claude Elbaz

1987-01-01

31

Stereochemical transfer to atmospheric aerosol particles accompanying the oxidation of biogenic volatile organic compounds  

NASA Astrophysics Data System (ADS)

Asymmetric emission profiles of the stereoisomers of plant-derived volatile organic compounds vary with season, geography, plant type, and stress factors. After oxidation of these compounds in the atmosphere, the low-vapor pressure products ultimately contribute strongly to the particle-phase material of the atmosphere. In order to explore the possibility of stereochemical transfer to atmospheric aerosol particles during the oxidation of biogenic volatile organic compounds, second-order coherent vibrational spectra were recorded of the particle-phase organic material produced by the oxidation of different stereoisomeric mixes of ?-pinene. The spectra show that the stereochemical configurations are not scrambled but instead are transferred from the gas-phase molecular precursors to the particle-phase molecules. The spectra also show that oligomers formed in the particle phase have a handed superstructure that depends strongly and nonlinearly on the initial stereochemical composition of the precursors. Because the stereochemical mix of the precursors for a material can influence the physical and chemical properties of that material, our findings suggest that chirality is also important for such properties of plant-derived aerosol particles.

Ebben, Carlena J.; Zorn, Soeren R.; Lee, Seung-Bok; Artaxo, Paulo; Martin, Scot T.; Geiger, Franz M.

2011-08-01

32

Dust Particle Effects on TPS Qualification for Martian Atmosphere  

NASA Astrophysics Data System (ADS)

Two experimental investigations were carried out in DLR's arc heated facility L2K using particle loaded CO2/N2 flow simulating a dust storm scenario in the Martian atmosphere. Precise particle velocity measurements were performed in the shock layer of a flat-faced cylinder model during the first test campaign. Using the L2F measurement technique the particle deceleration could be measured almost down to the model's surface for two different types of particles. In the second campaign dust erosion tests were performed. For different dust particles the influence of particle erosion on mass loss and surface degradation was measured. The measured data can be used for validation or modification of existing models for gas-particle interaction and surface erosion.

Esser, B.; Gülhan, A.; Koch, U.; Keller, K.; Beversdorff, M.

2009-01-01

33

Thermodynamics Of Common Atmospheric Particles On The Nanoscale  

NASA Astrophysics Data System (ADS)

A significant fraction of atmospheric particles are hygroscopic by nature and exhibit the properties of deliquescence and efflorescence. Recent field studies have observed large nucleation events of hygroscopic particles and note discrepancies between predicted and observed particle growth rates after nucleation. These growth rates are governed, in part, by the thermodynamic properties of particles only a few nanometers in diameter. However, little thermodynamic information is currently available for nanometer?sized particles. The Kelvin relation indicates that the surface tension of a particle less than 100nm in diameter can dramatically affect the thermodynamics, and surface states may begin to influence the bulk physical properties in these small particles with high surface to volume ratios. In this context, we are investigating the thermodynamic properties, including pre-deliquescence water adsorption, deliquescence, efflorescence, and supersaturated particle compositions of nanoparticles with mobility diameters in the range of 5 to 50 nm. We have developed a temperature and humidity-controlled laboratory-based Nano Differential Mobility Analyzer (NDMA) system to characterize the hygroscopic properties of the common atmospheric salt particles as a function of size. Two different aerosol generation systems have been used to cover the full size range. The first system (less than 20nm diameter) relies on an Atomizer (TSI 3076) to produce particles which are size?selected using an initial DMA. For particle sizes smaller than 20 nm, the Electrospray Aerosol Generator (EAG, TSI 3480) has been employed as a particle source. The EAG characteristically provides narrow size distributions, comparable to the monodisperse size distribution from a DMA, but with higher number concentrations. Once generated, the monodisperse aerosol flow is then conditioned with respect to humidity at a constant temperature and subsequently analyzed using a TSI Ultrafine CPC (Model 3010) modified for Pulse-Height Analysis. The dry particle sizes are also continually monitored by an external SMPS system (TSI 3936) to rectify errors in the calculated growth factor resulting from any drift in the dry particle size. The size changes of the humidified particles are directly correlated with the relative humidity and temperature. Our results of ammonium sulfate particles from 5 - 50 nm in diameter are consistent with those predicted from the Kelvin relation. The particle size affects both deliquescence and efflorescence of the homogeneous salt particles: the deliquescence relative humidity increases and the efflorescence decreases as particles become smaller. In addition, although the smaller the particle size the more significant water adsorption, the sharp deliquescence phase transition was obvious regardless of the particle sizes. The implications with respect to these observations will be further discussed at the presentation.

Onasch, T.; Han, J.; Oatis, S.; Brechtel, F.; Imre, D. G.

2002-12-01

34

Dispersion of aerosol particles in the atmosphere: Fukushima  

NASA Astrophysics Data System (ADS)

Investigation of dispersion and deposition of aerosol particles in the atmosphere is an essential issue, because they have an effect on the biosphere and atmosphere. Moreover, aerosol particles have different transport properties and chemical and physical transformations in the atmosphere compared to gas phase air pollutants. The motion of a particle is described by a set of ordinary differential equations. The large-scale dynamics in the horizontal direction can be described by the equations of passive scalar advection, but in the vertical direction a well-defined terminal velocity should be taken into account as a term added to the vertical wind component. In the planetary boundary layer turbulent diffusion has an important role in the particle dispersion, which is taken into account by adding stochastic terms to the deterministic equations above. Wet deposition is also an essential process in the lower levels of the atmosphere, however, its precise parameterization is a challenge. For the simulations the wind field and other necessary data were taken from the ECMWF ERA-Interim database. In the case of the Fukushima Daiichi nuclear disaster (March-April 2011) radioactive aerosol particles were also released in the planetary boundary layer. Simulations (included the continuous and varying emission from the nuclear power plant) will be presented for the period of 14-23 March. Results show that wet deposition also has to be taken into consideration in the lower levels of the atmosphere. Furthermore, dynamical system characteristics are evaluated for the aerosol particle dynamics. The escape rate of particles was estimated both with and without turbulent diffusion, and in both cases when there was no wet deposition and also when wet deposition was taken into consideration.

Haszpra, Tímea; Lagzi, István; Tél, Tamás

2013-04-01

35

Gas Dispersion and Immobile Gas Volume in Solid and Porous Particle Biofilter Materials at Low Air Flow Velocities  

Microsoft Academic Search

Gas-phase dispersion in granular biofilter materials with a wide range of particle sizes was investigated using atmospheric air and nitrogen as tracer gases. Two types of materials were used: (1) light extended clay aggregates (LECA), consisting of highly porous particles, and (2) gravel, consisting of solid particles. LECA is a commercial material that is used for insulation, as a soil

Prabhakar Sharma; Tjalfe G. Poulsen; Linsey Marr; Krzysztof Pikon´; Krzysztof Gaska; Lingjuan Wang; Edgar Oviedo-Rondon; John Small; Zifei Liu; Brian Sheldon; Gerald Havenstein; C. Williams; Di Tian; Daniel Cohan; Sergey Napelenok; Michelle Bergin; Yongtao Hu; Michael Chang; Armistead Russell; Ye Xu; Guohe Huang; Xiaosheng Qin; Kuo-Pin Yu; Grace Lee; Guo-Hao Huang; William Vizuete; Leiran Biton; Harvey Jeffries; Evan Couzo; Yi-Chi Chien; Chenju Liang; Shou-Heng Liu; Shu-Hua Yang; Maciej Kryza; Malgorzata Werner; Marek Blas; Anthony Dore; Mieczyslaw Sobik; Daniel Olsen; Morgan Kohls; Gregg Arney; Kaushlendra Singh; L. Risse; K. C. Das; John Worley; Sidney Thompson; Bryan Comer; James Corbett; J. Hawker; Karl Korfmacher; Earl Lee; Chris Prokop; James Winebrake

2010-01-01

36

Clouds and climate: Ability of atmospheric particles to uptake water  

Microsoft Academic Search

Atmospheric aerosols have significant impacts on human health, visibility and climate. Their interactions with water alter deposition within the human respiratory system, change particle optical properties, and change cloud microphysics by serving as cloud condensation nuclei (CCN). These clouds have a considerable influence on climate by reflecting incoming solar radiation, which provides a negative forcing, or cooling effect on earth's

Gabriella Joy Engelhart Farnham

2010-01-01

37

Optical properties, morphology and elemental composition of atmospheric particles at T1 supersite on MILAGRO campaign  

NASA Astrophysics Data System (ADS)

Atmospheric particles were sampled at T1 supersite during MILAGRO campaign, in March 2006. T1 was located at the north of Mexico City (MC). Aerosol sampling was done by placing copper grids for Transmission Electron Microscope (TEM) on the last five of an 8-stage MOUDI cascade impactor. Samples were obtained at different periods to observe possible variations on morphology. Absorption and scattering coefficients, as well as particle concentrations (0.01-3 ?m aerodynamic diameter) were measured simultaneously using a PSAP absorption photometer, a portable integrating nephelometer, and a CPC particle counter. Particle images were acquired at different magnifications using a CM 200 Phillips TEM-EDAX system, and then calculated the border-based fractal dimension. Also, Energy Dispersive X-Ray Spectroscopy (EDS) was used to determine the elemental composition of particles. The morphology of atmospheric particles for two aerodynamic diameters (0.18 and 1.8 ?m) was compared using border-based fractal dimension to relate it to the other particle properties, because T1-generated particles have optical, morphological and chemical properties different from those transported by the MC plume. Particles sampled under MC pollution influence showed not much variability, suggesting that more spherical particles (border-based fractal dimension close to 1.0) are more common in larger sizes (d50 = 1.8 ?m), which may be attributed to aerosol aging and secondary aerosol formation. Between 06:00 and 09:00 a.m., smaller particles (d50 = 0.18 ?m) had more irregular shapes resulting in higher border-based fractal dimensions (1.2-1.3) for samples with more local influence. EDS analysis in d50 = 0.18 ?m particles showed high contents of carbonaceous material, Si, Fe, K, and Co. Perhaps, this indicates an impact from industrial and vehicle emissions on atmospheric particles at T1.

Carabali, G.; Mamani-Paco, R.; Castro, T.; Peralta, O.; Herrera, E.; Trujillo, B.

2012-03-01

38

Heterogeneous ice nucleation and water uptake by field-collected atmospheric particles below 273 K  

NASA Astrophysics Data System (ADS)

Ice formation induced by atmospheric particles through heterogeneous nucleation is not well understood. Onset conditions for heterogeneous ice nucleation and water uptake by particles collected in Los Angeles and Mexico City were determined as a function of temperature (200-273 K) and relative humidity with respect to ice (RHice). Four dominant particle types were identified including soot associated with organics, soot with organic and inorganics, inorganic particles of marine origin coated with organic material, and Pb/Zn-containing particles apportioned to emissions relevant to waste incineration. Single particle characterization was provided by micro-spectroscopic analyses using computer controlled scanning electron microscopy with energy dispersive analysis of X-rays (CCSEM/EDX) and scanning transmission X-ray microscopy with near edge X-ray absorption fine structure spectroscopy (STXM/NEXAFS). Above 230 K, significant differences in onsets of water uptake and immersion freezing of different particle types were observed. Below 230 K, particles exhibited high deposition ice nucleation efficiencies and formed ice atRHicewell below homogeneous ice nucleation limits. The data suggest that water uptake and immersion freezing are more sensitive to changes in particle chemical composition compared to deposition ice nucleation. The data demonstrate that anthropogenic and marine influenced particles, exhibiting various chemical and physical properties, possess distinctly different ice nucleation efficiencies and can serve as efficient IN at atmospheric conditions typical for cirrus and mixed-phase clouds.

Wang, Bingbing; Laskin, Alexander; Roedel, Tobias; Gilles, Mary K.; Moffet, Ryan C.; Tivanski, Alexei V.; Knopf, Daniel A.

2012-09-01

39

Heterogeneous ice nucleation and water uptake by field-collected atmospheric particles below 273 K  

NASA Astrophysics Data System (ADS)

Ice formation induced by atmospheric particles through heterogeneous nucleation is not well understood. Onset conditions for heterogeneous ice nucleation and water uptake by particles collected in Los Angeles and Mexico City were determined as a function of temperature (200-273 K) and relative humidity with respect to ice (RHice). Four dominant particle types were identified including soot associated with organics, soot with organic and inorganics, inorganic particles of marine origin coated with organic material, and Pb/Zn-containing particles apportioned to emissions relevant to waste incineration. Single particle characterization was provided by micro-spectroscopic analyses using computer controlled scanning electron microscopy with energy dispersive analysis of X-rays (CCSEM/EDX) and scanning transmission X-ray microscopy with near edge X-ray absorption fine structure spectroscopy (STXM/NEXAFS). Above 230 K, significant differences in onsets of water uptake and immersion freezing of different particle types were observed. Below 230 K, particles exhibited high deposition ice nucleation efficiencies and formed ice atRHicewell below homogeneous ice nucleation limits. The data suggest that water uptake and immersion freezing are more sensitive to changes in particle chemical composition compared to deposition ice nucleation. The data demonstrate that anthropogenic and marine influenced particles, exhibiting various chemical and physical properties, possess distinctly different ice nucleation efficiencies and can serve as efficient IN at atmospheric conditions typical for cirrus and mixed-phase clouds.

Wang, Bingbing; Laskin, Alexander; Roedel, Tobias; Gilles, Mary K.; Moffet, Ryan C.; Tivanski, Alexei V.; Knopf, Daniel A.

2011-11-01

40

Black carbon particles in the urban atmosphere in Beijing  

NASA Astrophysics Data System (ADS)

A study of the concentration of black carbon particles and its variation in the urban atmosphere has been carried out since 1996 in the Beijing area. The measurements were done in the late autumn and early winter each year, the period before and after domestic heating activities begin. The results show the presence of black carbon particles at the high level that vary over a large range in the urban atmosphere in Beijing. The mean value of daily average concentration for the whole observation period of 1996 2004 is 20.0 ?g m-3. An evident decrease of black carbon particle concentration in the Beijing area is observed after 2000, and the daily average concentration of black carbon particles is estimated to be 16.0 ?g m-3 with a variation range of 2.10 50.50 ?g m-3 for the period of 2000 2004. The observation method and main variation behavior characteristics of black carbon particles in the urban atmosphere in the Beijing area are given and discussed.

Wang, Gengchen; Bai, Jianhui; Kong, Qinxin; Emilenko, Alexander

2005-09-01

41

Discrimination of airborne material particles from light scattering (TAOS) patterns  

NASA Astrophysics Data System (ADS)

Two-dimensional angle-resolved optical scattering (TAOS) is an experimental method which collects the intensity pattern of monochromatic light scattered by a single, micron-sized airborne particle. In general, the interpretation of these patterns and the retrieval of the particle refractive index, shape or size alone, are difficult problems. The solution proposed herewith relies on a learning machine (LM): rather than identifying airborne particles from their scattering patterns, TAOS patterns themselves are classified. The LM consists of two interacting modules: a feature extraction module and a linear classifier. Feature extraction relies on spectrum enhancement, which includes the discrete cosine Fourier transform and non-linear operations. Linear classification relies on multivariate statistical analysis. Interaction enables supervised training of the LM. The application described in this article aims at discriminating the TAOS patterns of single bacterial spores (Bacillus subtilis) from patterns of atmospheric aerosol and diesel soot particles. The latter are known to interfere with the detection of bacterial spores. Classification has been applied to a data set with more than 3000 TAOS patterns from various materials. Some classification experiments are described, where the size of training sets has been varied as well as many other parameters which control the classifier. By assuming all training and recognition patterns to come from the respective reference materials only, the most satisfactory classification result corresponds to ? 20% false negatives from Bacillus subtilis particles and <= 11% false positives from environmental and diesel particles.

Crosta, Giovanni F.; Pan, Yong-Le; Videen, Gorden; Aptowicz, Kevin B.; Chang, Richard K.

2013-05-01

42

Observation of nitrate coatings on atmospheric mineral dust particles  

NASA Astrophysics Data System (ADS)

Nitrate compounds have received much attention because of their ability to alter the hygroscopic properties and cloud condensation nuclei (CCN) activity of mineral dust particles in the atmosphere. However, very little is known about specific characteristics of ambient nitrate-coated mineral particles on an individual particle scale. In this study, sample collection was conducted during brown haze and dust episodes between 24 May and 21 June 2007 in Beijing, northern China. Sizes, morphologies, and compositions of 332 mineral dust particles together with their coatings were analyzed using transmission electron microscopy (TEM) coupled with energy-dispersive X-ray (EDX) microanalyses. Structures of some mineral particles were verified using selected-area electron diffraction (SAED). TEM observation indicates that approximately 90% of the collected mineral particles are covered by visible coatings in haze samples whereas only 5% are coated in the dust sample. 92% of the analyzed mineral particles are covered with Ca-, Mg-, and Na-rich coatings, and 8% are associated with K- and S-rich coatings. The majority of coatings contain Ca, Mg, O, and N with minor amounts of S and Cl, suggesting that they are possibly nitrates mixed with small amounts of sulfates and chlorides. These nitrate coatings are strongly correlated with the presence of alkaline mineral components (e.g., calcite and dolomite). CaSO4 particles with diameters from 10 to 500 nm were also detected in the coatings including Ca(NO3)2 and Mg(NO3)2. Our results indicate that mineral particles in brown haze episodes were involved in atmospheric heterogeneous reactions with two or more acidic gases (e.g., SO2, NO2, HCl, and HNO3). Mineral particles that acquire hygroscopic nitrate coatings tend to be more spherical and larger, enhancing their light scattering and CCN activity, both of which have cooling effects on the climate.

Li, W. J.; Shao, L. Y.

2009-03-01

43

Size and composition distribution of atmospheric particles in southern California  

SciTech Connect

Continuous measurements of single particle size and chemical composition in the atmosphere are made using aerosol time-of-flight mass spectrometers (ATOFMS) operated alongside more conventional reference air sampling instruments at a network of three urban air monitoring sites in southern California. Electrical aerosol analyzers and optical particle counters are employed to acquire continuous particle size distribution data, and inertial impactor and bulk filter samples with 4-h resolution are taken for determination of particle size and chemical composition. Filter and impactor samples also are taken upwind of the air basin at Santa Catalina Island in order to characterize background air quality. The airborne particle size and composition distribution as measured by the cascade impactors at inland sites differ from that over the ocean principally due to depletion of sea salt particles accompanied by the addition of fine carbon-containing particles and secondary aerosol nitrate. Data from the ATOFMS systems create a continuous time series of sodium-, ammonium-, nitrate-, and carbon-containing particle counts that provide a high-resolution view of differences in particle composition as a function of location in the air basin. Results show that the characteristic peak in the Los Angeles area aerosol mass distribution in the 0.2--0.3-{micro}m size range observed during the 1987 SCAQS experiments has been reduced, consistent with reductions in diesel soot and elemental carbon emissions since that time.

Hughes, L.S.; Allen, J.O.; Kleeman, M.J. [and others

1999-10-15

44

The atmospheric radiation response to solar-particle-events.  

PubMed

High-energy solar particles, produced in association with solar flares and coronal mass ejections, occasionally bombard the earth's atmosphere. resulting in radiation intensities additional to the background cosmic radiation. Access of these particles to the earth's vicinity during times of geomagnetic disturbances are not adequately described by using static geomagnetic field models. These solar fluxes are also often distributed non uniformly in space, so that fluxes measured by satellites obtained at great distances from the earth and which sample large volumes of space around the earth cannot be used to predict fluxes locally at the earth's surface. We present here a method which uses the ground-level neutron monitor counting rates as adjoint sources of the flux in the atmosphere immediately above them to obtain solar-particle effective dose rates as a function of position over the earth's surface. We have applied this approach to the large September 29-30, 1989 ground-level event (designated GLE 42) to obtain the magnitude and distribution of the solar-particle effective dose rate from an atypically large event. The results of these calculations clearly show the effect of the softer particle spectra associated with solar particle events, as compared with galactic cosmic rays, results in a greater sensitivity to the geomagnetic field, and, unlike cosmic rays, the near-absence of a "knee" near 60 degrees geomagnetic latitude. PMID:14727666

O'Brien, K; Sauer, H H

2003-01-01

45

Atmospheric cosmic rays and solar energetic particles at aircraft altitudes.  

PubMed

Galactic cosmic rays, which are thought to be produced and accelerated by a variety of mechanisms in the Milky Way galaxy, interact with the solar wind, the earth's magnetic field, and its atmosphere to produce hadron, lepton, and photon fields at aircraft altitudes that are quite unlike anything produced in the laboratory. The energy spectra of these secondary particles extend from the lowest possible energy to energies over an EeV. In addition to cosmic rays, energetic particles, generated on the sun by solar flares or coronal mass ejections, bombard the earth from time to time. These particles, while less energetic than cosmic rays, also produce radiation fields at aircraft altitudes which have qualitatively the same properties as cosmic rays. The authors have calculated atmospheric cosmic-ray angular fluxes, spectra, scalar fluxes, and ionization, and compared them with experimental data. Agreement with these data is seen to be good. These data have been used to calculate equivalent doses in a simplified human phantom at aircraft altitudes and the estimated health risks to aircraft crews. The authors have also calculated the radiation doses from several large solar energetic particle events (known as GLEs, or Ground Level Events), which took place in 1989, including the very large event known as GLE 42, which took place on September 29th and 30th of that year. The spectra incident on the atmosphere were determined assuming diffusive shock theory. Unfortunately, there are essentially no experimental data with which to compare these calculations. PMID:11542509

O'Brien, K; Friedberg, W; Sauer, H H; Smart, D F

1996-01-01

46

Atmospheric observations of new particle growth and shrinkage  

NASA Astrophysics Data System (ADS)

In subtropical central Taiwan, a total of fourteen new particle formation (NPF) events were identified at four sites that represent urban, coastal, mountain and downwind area, respectively. Among them, there were five particle shrinkage events showing the grown particles shrank back to the smallest measureable size of ~10 nm, thereby creating a unique "arch-like" shape in the size distribution contour plot. The particle shrinkage rates ranged from 5.1 to 7.6 nm h-1. The corresponding particle volume losses suggest that a notable fraction of the condensable species that contributed to growth was semi-volatile. The particle shrinkage was related to strong atmospheric dilution, high ambient temperature and low relative humidity, thus favoring the evaporation of semi-volatile species from the particulate phase to the gas phase. Our observations show that the new particle growth could be a reversible process, in which the evaporating semi-volatile species are important for the growth of new particles to sizes of environmental health concerns.

Young, Li-Hao; Lee, Shan-Hu; Kanawade, Vijay P.; Hsiao, Ta-Chih; Lee, Yungling L.; Hwang, Bing-Fang; Liou, Yi-Jyun; Hsu, Hui-Tsung; Tsai, Perng-Jy

2013-05-01

47

Material void opening computation using particle method  

SciTech Connect

When performing the calculation of material flow in two dimensional Eulerian coordinates, one always encounters the difficulties of modeling the void opening due to material failure such as fracture, spallation, or phase change. The present studies use one type of particle to represent the material and another type for the void space. According to the flow conditions, the void space may grow with crack propagation or may be recombined with the void space closed up when the volume decreases. The penetration of a copper rod into, and eventually through a steel plate, is calculated using the present code.

Lee, W.H.; Painter, J.W.

1988-01-01

48

Stable sulphate clusters as a source of new atmospheric particles  

PubMed

The formation of new atmospheric particles with diameters of 3-10 nm has been observed at a variety of altitudes and locations. Such aerosol particles have the potential to grow into cloud condensation nuclei, thus affecting cloud formation as well as the global radiation budget. In some cases, the observed formation rates of new particles have been adequately explained by binary nucleation, involving water and sulphuric acid, but in certain locations--particularly those within the marine boundary layer and at continental sites--observed ambient nucleation rates exceed those predicted by the binary scheme. In these locations, ambient sulphuric acid (H2SO4) levels are typically lower than required for binary nucleation, but are sufficient for ternary nucleation (sulphuric acid-ammonia-water). Here we present results from an aerosol dynamics model with a ternary nucleation scheme which indicate that nucleation in the troposphere should be ubiquitous, and yield a reservoir of thermodynamically stable clusters 1-3 nm in size. We suggest that the growth of these clusters to a detectable size (> 3 nm particle diameter) is restricted by the availability of condensable vapour. Observations of atmospheric particle formation and growth from a continental and a coastal site support this hypothesis, indicating that a growth process including ternary nucleation is likely to be responsible for the formation of cloud condensation nuclei. PMID:10716441

Kulmala; Pirjola; Makela

2000-03-01

49

Cohesive granular materials composed of nonconvex particles  

NASA Astrophysics Data System (ADS)

The macroscopic cohesion of granular materials made up of sticky particles depends on the particle shapes. We address this issue by performing contact dynamics simulations of 2D packings of nonconvex aggregates. We find that the macroscopic cohesion is strongly dependent on the strain and stress inhomogeneities developing inside the material. The largest cohesion is obtained for nearly homogeneous deformation at the beginning of unconfined axial compression and it evolves linearly with nonconvexity. Interestingly, the aggregates in a sheared packing tend to form more contacts with fewer neighboring aggregates as the degree of nonconvexity increases. We also find that shearing leads either to an isotropic distribution of tensile contacts or to the same privileged direction as that of compressive contacts.

Saint-Cyr, Baptiste; Radjai, Farhang; Delenne, Jean-Yves; Sornay, Philippe

2013-05-01

50

Characterization of Spatial Impact of Particles Emitted from a Cement Material Production Facility on Outdoor Particle Deposition in the Surrounding Community  

Microsoft Academic Search

The objective of this study was to estimate the contribution of a facility that processes steel production slag into raw material for cement production to local outdoor particle deposition in Camden, NJ. A dry deposition sampler that can house four 37-mm quartz fiber filters was developed and used for the collection of atmospheric particle deposits. Two rounds of particle collection

Chang Ho Yu; Zhihua Fan; Elizabeth McCandlish; Alan H. Stern; Paul J. Lioy

2011-01-01

51

Applicability of condensation particle counters to measure atmospheric clusters  

NASA Astrophysics Data System (ADS)

The ambient and laboratory molecular and ion clusters were investigated. Here we present data on the ambient concentrations of both charged and uncharged molecular clusters as well as the performance of a pulse height condensation particle counter (PH-CPC) and an expansion condensation particle counter (E-CPC). The ambient molecular cluster concentrations were measured using both instruments, and they were deployed in conjunction with ion spectrometers and other aerosol instruments in Hyytiälä, Finland at the SMEAR II station during 1 March to 30 June 2007. The observed cluster concentrations varied and were from ca. 1000 to 100 000 cm-3. Both instruments showed similar concentrations. The average size of detected clusters was approximately 1.8 nm. As the atmospheric measurements at sub 2-nm particles and molecular clusters are a challenging task, and we were most likely unable to detect the smallest clusters, the reported concentrations are our best estimates for minimum cluster concentrations in boreal forest environment.

Sipilä, M.; Lehtipalo, K.; Kulmala, M.; Petäjä, T.; Junninen, H.; Aalto, P. P.; Manninen, H. E.; Vartiainen, E.; Riipinen, I.; Kyrö, E.-M.; Curtius, J.; Kürten, A.; Borrmann, S.; O'Dowd, C. D.

2008-03-01

52

Applicability of condensation particle counters to measure atmospheric clusters  

NASA Astrophysics Data System (ADS)

This study presents an evaluation of a pulse height condensation particle counter (PH-CPC) and an expansion condensation particle counter (E-CPC) in terms of measuring ambient and laboratory-generated molecular and ion clusters. Ambient molecular cluster concentrations were measured with both instruments as they were deployed in conjunction with an ion spectrometer and other aerosol instruments in Hyytiälä, Finland at the SMEAR II station between 1 March and 30 June 2007. The observed cluster concentrations varied and ranged from some thousands to 100 000 cm-3. Both instruments showed similar (within a factor of ~5) concentrations. An average size of the detected clusters was approximately 1.8 nm. As the atmospheric measurement of sub 2-nm particles and molecular clusters is a challenging task, we conclude that most likely we were unable to detect the smallest clusters. Nevertheless, the reported concentrations are the best estimates to date for minimum cluster concentrations in a boreal forest environment.

Sipilä, M.; Lehtipalo, K.; Kulmala, M.; Petäjä, T.; Junninen, H.; Aalto, P. P.; Manninen, H. E.; Kyrö, E.-M.; Asmi, E.; Riipinen, I.; Curtius, J.; Kürten, A.; Borrmann, S.; O'Dowd, C. D.

2008-07-01

53

Source contributions to atmospheric fine carbon particle concentrations  

NASA Astrophysics Data System (ADS)

A Lagrangian particle-in-cell air quality model has been developed that facilitates the study of source contributions to atmospheric fine elemental carbon and fine primary total carbon particle concentrations. Model performance was tested using spatially and temporally resolved emissions and air quality data gathered for this purpose in the Los Angeles area for the year 1982. It was shown that black elemental carbon (EC) particle concentrations in that city were dominated by emissions from diesel engines including both on-highway and off-highway applications. Fine primary total carbon particle concentrations (TC=EC+organic carbon) resulted from the accumulation of small increments from a great variety of emission source types including both gasoline and diesel powered highway vehicles, stationary source fuel oil and gas combustion, industrial processes, paved road dust, fireplaces, cigarettes and food cooking (e.g. charbroilers). Strategies for black elemental carbon particle concentration control will of necessity need to focus on diesel engines, while controls directed at total carbon particle concentrations will have to be diversified over a great many source types.

Andrew Gray, H.; Cass, Glen R.

54

Clouds and climate: Ability of atmospheric particles to uptake water  

NASA Astrophysics Data System (ADS)

Atmospheric aerosols have significant impacts on human health, visibility and climate. Their interactions with water alter deposition within the human respiratory system, change particle optical properties, and change cloud microphysics by serving as cloud condensation nuclei (CCN). These clouds have a considerable influence on climate by reflecting incoming solar radiation, which provides a negative forcing, or cooling effect on earth's climate due to increased reflectivity. Our current understanding of the interactions of aerosols with clouds and climate is limited; the parameterizations needed for modeling predictions of climate can be aided by constraints from laboratory and in-situ experiments. Much of the uncertainty regarding the water uptake by atmospheric particles resides in organic aerosols. This thesis utilizes smog chamber techniques to study the CCN activity of biogenic secondary organic aerosol (SOA) including isoprene, monoterpene and sesquiterpene precursors. Particular emphasis is placed on comparison to Kohler theory, surface tension, solubility, droplet growth kinetics and volatility. The work also studies the CCN activity of a less controlled mixture of primary aerosol from biomass burning and the potential for transformation in the atmosphere via oxidation. Finally, this dissertation utilizes a dry-ambient aerosol size spectrometer (DAASS) to study the water content of aged atmospheric particles in a remote environment. We find monoterpene and isoprene SOA serve as good CCN. The water soluble component of sesquiterpene SOA has similar properties to those observed for monoterpene SOA meaning that a predictive understanding of SOA CCN may require knowledge of the water soluble fraction, but not its exact speciation. Sesquiterpene SOA CCN activity is particularly sensitive to temperature, suggesting that the CCN active fraction of the SOA is semi-volatile. Biomass burning experiments reveal that the CCN characteristics of primary aerosols converge through oxidative processing. This may support findings of SOA CCN activity with a common hygroscopicity parameter of approximately 0.1. Aged atmospheric particles under sub-saturated conditions remain wet even at low relative humidities. Water uptake by organics was small and generally consistent with laboratory observations. All of this work will help to constrain organic aerosol-water interactions and provide a more accurate assessment for visibility and climate issues.

Farnham, Gabriella Joy Engelhart

55

Ionization of the Earth's Upper Atmosphere in Large Energetic Particle Events  

Microsoft Academic Search

Energetic charged particles ionize the upper terrestrial atmosphere. Sofar, chemical consequences of precipitating particles have been discussed for solar protons with energies up to a few hundred MeV. We present a refined model for the interaction of energetic particles with the atmosphere based on a Monte-Carlo simulation. The model includes higher energies and other particle species, such as energetic solar

E. Wolff; J. Burrows; M. Kallenrode; M. von Koenig; K. F. Kuenzi; M. Quack

2001-01-01

56

Properties of submicron particles in Atmospheric Brown Clouds  

NASA Astrophysics Data System (ADS)

The Atmospheric Brown Clouds (ABC) is an important problem of this century. Investigations of last years and satellite data show that the ABC (or brown gas, smog, fog) cover extensive territories including the whole continents and oceans. The brown gas consists of a mixture of particles of anthropogenic sulfates, nitrates, organic origin, black carbon, dust, ashes, and also natural aerosols such as sea salt and mineral dust. The brown color is a result of absorption and scattering of solar radiation by the anthropogenic black carbon, ashes, the particles of salt dust, and nitrogen dioxide. The investigation of the ABC is a fundamental problem for prevention of degradation of the environment. At present in the CIS in-situ investigations of the ABC are carried out on Lidar Station Teplokluchenka (Kyrgyz Republic). Here, we present the results of experimental investigation of submicron (nanoscale) particles originating from the ABC and the properties of the particles. Samples of dust precipitating from the ABC were obtained at the area of Lidar Station Teplokluchenka as well as scientific station of the Russian Academy of Sciences near Bishkek. The data for determination of the grain composition were obtained with the aid of the scanning electron microscopes JEOL 6460 LV and Philips XL 30 FEG. Analysis of the properties of the particles was performed by means of the X-ray diffraction using diffractometer Siemens D5000. The images of the grains were mapped. The investigation allows us to get (after the image processing) the grain composition within the dust particle size range of 60 nm to 700 ?m. Distributions of nano- and microscale particles in sizes were constructed using Rozin-Rammler coordinates. Analysis of the distributions shows that the ABC contain submicron (nanoscale) particles; 2) at higher altitudes the concentration of the submicron (nanoscale) particles in the ABC is higher than at lower altitudes. The chemical compositions of the particles are shown to be close to those typical for the ABC. We present also the results of the study of morphology and mineralogical composition of the obtained particles as well as their magnetic properties. This study was supported by the Division of Earth Sciences, Russian Academy of Sciences (research program "Nanoscale particles in nature and technogenic products: conditions of existence, physical and chemical properties, and mechanisms of formation") and by ISTC (project No. KR-1522).

Adushkin, V. V.; Chen, B. B.; Dubovskoi, A. N.; Friedrich, F.; Pernik, L. M.; Popel, S. I.; Weidler, P. G.

2010-05-01

57

Gas/particle Partitioning and Particle Size Distributions of Polycyclic Aromatic Hydrocarbons (pahs) in the Atmosphere.  

NASA Astrophysics Data System (ADS)

This study applied three different gas/particle (G/P) separation mechanisms (diffusion, filtration and impaction) to investigate G/P partitioning and particle size distributions of polycyclic aromatic hydrocarbons (PAHs) in the atmosphere. Because some PAHs such as benzo (a) pyrene have been shown to be carcinogenic to humans and persistent in the environment, it is important to have reliable methods to measure PAH G/P partitioning and particle size distributions for the purpose of understanding their atmospheric processing and their impact to environmental and human health. The objectives of this study include: (1) Development of a diffusion separator (DS) to separate a known fraction of the gas phase from the aerosol: The calibration experiment results reveal that the G/P separation performance of the DS agrees well with diffusion theory. True gas PAH concentrations are calculated by the measured PAH concentrations in the core exit of the DS and the diffusion factor at the sampling temperature. (2) Evaluation of sampling artifacts associated with high volume samplers and their effectiveness in measuring PAH G/P partitioning in the atmosphere: The comparison between the DS, a filter/adsorbent sampler (FA) and a microorifice uniform deposit impactor (MOUDI) revealed both gaseous sorption onto filters and desorption from filters of the FA sampler for most PAHs. (3) Investigation of particle size distribution of PAHs in Chicago urban and Minnesota suburban areas: The results of MOUDI sampler showed that the PAH mass median diameters (MMDs) are smaller than atmospheric particle MMDs by 0.1-0.3 ?m in both areas. The calculated PAH dry deposition fluxes and Lake Michigan sediment accumulation rates indicates that the atmospheric dry deposition contributes 15-50% of PAHs to nearby Lake Michigan sediment.

Liu, Shi-Ping

58

Monitoring of atmospheric particles over an urban area  

NASA Astrophysics Data System (ADS)

It is known that optical properties of atmospheric aerosols are important for the Earth s radiation budget and global climate It is also known that Asia is the most complicated region for aerosol study because the dust particles come from continental desert area carbonaceous aerosols are produced by large Siberian biomass-burning plumes and small anthropogenic particles are emitted from the increasing industrial activities Simultaneous measurements of atmospheric aerosols and suspended particulate matter SPM have been undertaken at Kinki University campus in Higashi-Osaka in order to monitor the urban environment during more than two years The sun sky photometry has been made as a NASA AERONET station since 2002 and the SPM-613D Ki-moto Electric has been taking measurements of the SPM concentrations such as TSP PM 10 PM 2 5 and OBC at the same site since March 15 2004 This long term simul-taneous monitoring of aerosols and SPM provides us with typical aerosol types over an industrial city of Higashi-Osaka and the relationship between aerosol properties obtained from radiometry with AERONET and the SPM measurements as 1 The air quality of the Higashi-Osaka site is poor due to not only anthropogenic particles by local emissions such as diesel vehicles and chemical industries but also due to dust particles and biomass-burning aerosols by large scale climatic conditions 2 Fine anthropogenic particles dominate at Higashi-Osaka even during dust events It is of interest to mention that dust events at Higashi-Osaka seem to be

Mukai, S.; Sano, I.; Yasumoto, M.

59

Neutrons for probing the ice nucleation on atmospheric soot particles  

NASA Astrophysics Data System (ADS)

Soot resulting from combustion of kerosene in aircraft engines can act as condensation nuclei for water/ice in the atmosphere and promote the formation of contrails that turn into artificial cirrus clouds and affect the climate. The mechanisms of nucleation of water/ice particles are not well identified. Studies "in situ" are difficult to realize, so we try to determine by neutron diffraction the nucleation of water/ice adsorbed on soot collected at the outlet of an aircraft engine combustor within the conditions of the upper troposphere. The results are compared with those obtained on model laboratory soot. The comparison highlights the role of chemical impurities and structural defects of original aircraft engine soot on the nucleation of water/ice in atmospheric conditions.

Demirdjian, B.; Tishkova, V.; Ferry, D.

2012-11-01

60

Ozonation of isoproturon adsorbed on silica particles under atmospheric conditions  

NASA Astrophysics Data System (ADS)

The results on heterogeneous ozonation of a phenylurea pesticide, isoproturon, under atmospheric conditions are presented for the first time in the present study. The study was carried out using an experimental device previously adopted and validated for the heterogeneous reactivity of organics toward ozone (Pflieger et al., 2011). Isoproturon was adsorbed on silica particles via a liquid-to-solid equilibrium with a load far below a monolayer (0.02% by weight/surface coverage of 0.5%). The rate constants were estimated by measuring the consumption of the organic (dark, T = 26 °C, RH < 1%). The experimental data were fitted by both the modified Langmuir-Hinshelwood and the Eley-Rideal patterns, resulting in atmospheric lifetimes of heterogeneous ozonation of 4 and 6 days, respectively (for 40 ppb of O3). Parameters, such as the number and the quantity of pesticides adsorbed on the solid support, which can significantly influence the heterogeneous kinetics, were investigated as well. The results obtained suggest that the organic compound is adsorbed in multilayer aggregates on the aerosol even though submonolayer coverage is assumed. The presence of a second herbicide, trifluralin, together with isoproturon on the aerosol surface does not affect the kinetics of ozonation, indicating that both compounds are adsorbed on different surface sites of silica particles.

Pflieger, Maryline; Grgi?, Irena; Kitanovski, Zoran

2012-12-01

61

Investigating The Ionization of The Earth's Atmosphere At Large Energetic Particle Events  

Microsoft Academic Search

To investigate the influence of energetic particle events on the terrestrial atmosphere (e.g. due to ionization and\\/or hadronic interaction) a number of aspects are under consideration, such as the species of the precipitating particles, their energies, fluences as well as a repetition rate of events. In preparation of a refined model of precipitating charged particle interactions with the atmosphere, we

E. Wolff; J. Burrows; M.-B. Kallenrode; M. von König; K. F. Künzi; M. Quack

2002-01-01

62

Study of inlet materials for sampling atmospheric nitric acid  

Microsoft Academic Search

The adsorption of nitric acid (HNOâ) from a flowing gas stream is studied for a variety of wall materials to determine their suitability for use in atmospheric sampling instruments. Parts per billion level mixtures of HNOâ in synthetic air flow through tubes of different materials such that >80% of the molecules interact with the walls. A chemical ionization mass spectrometer

J. A. Neuman; L. G. Huey; T. B. Ryerson; D. W. Fahey

1999-01-01

63

The effect of atmospheric pollution on building materials  

Microsoft Academic Search

This chapter surveys main effects of atmospheric pollution on building materials. It summarises these effects on stone, bricks, mortar, concrete, glass, metals (iron, zinc, copper, bronze, aluminium, lead and silver), polymers, paints and timber. Special attention is paid to stone because of its extensive use as building material in the cultural heritage. In general, main damaging agent is sulfur dioxide

C. M. Grossi; P. Brimblecombe

2002-01-01

64

Chemical machining of Zerodur material with atmospheric pressure plasma jet  

Microsoft Academic Search

The material of Zerodur is widely used in high performance optics because of its excellent thermal stability characteristics. This paper deals with the development of an APPJ (Atmospheric Pressure Plasma Jet) chemical machining process for defect free and high efficiency machining of Zerodur. The APPJ chemical machining mechanism for multi-phase multi-composite materials is presented. The chemical property of the plasma

Y. X. Yao; B. Wang; J. H. Wang; H. L. Jin; Y. F. Zhang; S. Dong

2010-01-01

65

Wood-based building materials and atmospheric carbon emissions  

Microsoft Academic Search

This study investigates the global impact of wood as a building material by considering emissions of carbon dioxide to the atmosphere. Wood is compared with other materials in terms of stored carbon and emissions of carbon dioxide from fossil fuel energy used in manufacturing. An analysis of typical forms of building construction shows that wood buildings require much lower process

Andrew H Buchanan; S. Bry Levine

1999-01-01

66

Heterogeneous oxidation of atmospheric aerosol particles by gas-phase radicals  

Microsoft Academic Search

Atmospheric aerosol particles play pivotal roles in climate and air quality. Just as chemically reduced gases experience oxidation in the atmosphere, it is now apparent that solid and liquid atmospheric particulates are also subject to similar oxidative processes. The most reactive atmospheric gas-phase radicals, in particular the hydroxyl radical, readily promote such chemistry through surficial interactions. This Review looks at

I. J. George; J. P. D. Abbatt

2010-01-01

67

Hyperspectral material identification on radiance data using single-atmosphere or multiple-atmosphere modeling  

NASA Astrophysics Data System (ADS)

Reflectance-domain methods convert hyperspectral data from radiance to reflectance using an atmospheric compensation model. Material detection and identification are performed by comparing the compensated data to target reflectance spectra. We introduce two radiance-domain approaches, Single atmosphere Adaptive Cosine Estimator (SACE) and Multiple atmosphere ACE (MACE) in which the target reflectance spectra are instead converted into sensor-reaching radiance using physics-based models. For SACE, known illumination and atmospheric conditions are incorporated in a single atmospheric model. For MACE the conditions are unknown so the algorithm uses many atmospheric models to cover the range of environmental variability, and it approximates the result using a subspace model. This approach is sometimes called the invariant method, and requires the choice of a subspace dimension for the model. We compare these two radiance-domain approaches to a Reflectance-domain ACE (RACE) approach on a HYDICE image featuring concealed materials. All three algorithms use the ACE detector, and all three techniques are able to detect most of the hidden materials in the imagery. For MACE we observe a strong dependence on the choice of the material subspace dimension. Increasing this value can lead to a decline in performance.

Mariano, Adrian V.; Grossmann, John M.

2010-11-01

68

Heterogeneous Reactions On Mineral Dust Particles: Atmospheric Acids  

NASA Astrophysics Data System (ADS)

We report on laboratory experiments of heterogeneous reactions of atmospheric acids such as HNO3, HCl and CF3COOH on surrogates of suspended mineral dust particles. We have used model substrates such as polycrystalline CaCO3, Saharan and Arizona dust samples as well as Kaolinite powder. The rates of uptake, the reaction products and the reaction mechanisms have been studied in detail with special emphasis on the role of adsorbed H2O in regards to the reaction mechanism. The initial rates of uptake are large but saturate at increasing exposure to the acids. Atmospheric acids dissolve carbonate via carbonic acid into CO2 and H2O, the latter of which has not been detected for reaction with HCl, presumably because of the formation of a hygroscopic product (CaCl2). The reaction mechanism involves the formation of basic adsorption (reaction) sites which are maintained through the equilibrium CaCO3 + H2O ó Ca(OH)2 + CO2 which has been measured from rates of CO2 uptake. No reaction products have been observed on Kaolinite samples under conditions where significant amounts of HNO3 have been adsorbed. The uptake coefficients of the non-reactive adsorption are of the order of 0.2 and are independent of the amount of surface-bound H2O.

Santschi, Christian; Rossi, Michel J.

69

Derivation of damage functions for atmospheric degradation of materials  

SciTech Connect

The information in the pape is directed to those who develop and use damage functions that relate atmospheric degradation of materials to various causal agents in the atmosphere. Such relationships must be quantified mathematically as part of the overall cost-benefit considerations associated with possible pollution control strategies. Damage functions may be derived from theoretical considerations, from controlled experiments in environmental simulation chambers, from essentially uncontrolled field experiments, or from semicontrolled field experiments. The paper discusses optimum ways of combining these methods to improve the credibility and applicability of materials damage functions for use in assessments, with reference to some of the research performed for the National Acid Precipitation Assessment Program.

Haynie, F.H.; Lipfert, F.W.

1986-05-01

70

Particle beams in the solar atmosphere - General overview  

NASA Astrophysics Data System (ADS)

An overview of particle beams in the solar atmosphere is separated into discussions of (1) current-carrying beams, (2) current-neutralized electron beams, and (3) ion beams. The Alfven-Lawson limit on an electric current implies some severe limitations. Considerable progress has been made in understanding how electron beams in type III solar radio events propagate in a way that is consistent with the generation of Langmuir waves, but a completely consistent picture has not yet emerged. Such beams, and more importantly the electron beams that generate hard X-ray bursts require current neutralization; how the required return current is set up is still not entirely clear. There is direct evidence for ion beams with energies above about 10 MeV per nucleon from gamma-ray line emission; there is no unambiguous evidence for ion beams of lower energy. A mechanism is suggested for bulk energization of electrons due to dissipation of a parallel current in solar flares. Some outstanding problems concerning particle beams are identified.

Melrose, D. B.

1990-12-01

71

Investigating The Ionization of The Earth's Atmosphere At Large Energetic Particle Events  

NASA Astrophysics Data System (ADS)

To investigate the influence of energetic particle events on the terrestrial atmosphere (e.g. due to ionization and/or hadronic interaction) a number of aspects are under consideration, such as the species of the precipitating particles, their energies, fluences as well as a repetition rate of events. In preparation of a refined model of precipitating charged particle interactions with the atmosphere, we calculate the ionization in the earth's atmosphere for well- known recent events (e.g. the Bastille Day event on July 14, 2000) of high particle fluences by using computer simulations of the earth's atmosphere and in situ measured particle intensities. The changes in atmospheric chemistry derieved from this ionization are described in the accompanying contribution of M. von König et al. (Modelling the influence of large energetic particle events on the chemical composition of the middle and upper atmosphere). Although very effective for atmospheric chemistry, these events are too rare and too short-lived to contribute significantly to the atmospheric NOx budget on a long-time basis. However, McCracken et al. (2001) suggests from nitrate depositions in ice- cores that solar particle events have occured more frequently and with a higher in- tensity in historical times, and thus may have led to a greater impact than the events discussed above. Therefore, we evaluate the influence of large historical energetic particle events, such as NOx and Ozone behaviour due to atmospheric ionization at Carrington's white light flare in 1859.

Wolff, E.; Burrows, J.; Kallenrode, M.-B.; von König, M.; Künzi, K. F.; Quack, M.

72

Identification of molecular-cloud material in interplanetary dust particles.  

PubMed

Interplanetary dust particles (IDPs) collected in the Earth's stratosphere and meteorites are fragments of comets and asteroids. These are 'primitive' meteorites in part because they have preserved materials which predate the formation of the Solar System. The most primitive (least altered) meteorites contain a few parts per million of micrometre-sized dust which formed in the atmospheres of giant stars. Some meteorites have elevated D/H and 15N/14N ratios that are attributed to surviving interstellar organic molecules which have probably been strongly diluted and altered by parent-body processes. Most IDPs are chemically, mineralogically, and texturally primitive in comparison to meteorites. Here I show that H and N isotopic anomalies among fragile 'cluster' IDPs are far larger, more common, and less equilibrated than those previously observed in other IDPs or meteorites. In some cases, the D/H ratios that we measure reach the values of interstellar molecules, suggesting that molecular-cloud material has survived intact. These observations indicate that cluster IDPs are the most primitive class of Solar System materials currently available for laboratory analysis. PMID:10801119

Messenger, S

2000-04-27

73

Simulation of particle fluxes and cosmogenic nuclide production in the Earth's atmosphere  

Microsoft Academic Search

A purely physical model for the simulation of cosmic ray particle interactions with the Earth's atmosphere and subsequent production and transport of secondary particles is presented. Neutron and proton spectra as a function of the coordinate in the atmosphere were calculated using a GEANT\\/MCNP-based code system. The calculated neutron fluxes are in good agreement with experimental data based on neutron

J. Masarik; J. Beer

1999-01-01

74

Optical properties, morphology and elemental chemical composition of atmospheric particles at T1 supersite on MILAGRO campaign  

NASA Astrophysics Data System (ADS)

Atmospheric particles were sampled at T1 supersite (19°43' N latitude, 98°58' W longitude, and 2340 m above sea level) during MILAGRO campaign. T1 was located at the north of Mexico City Metropolitan Area (MCMA). Aerosol sampling was done by placing transmission electron microscope (TEM) copper grids on the last 5 stages of an 8-stage MOUDI cascade impactor (d50 = 1.8, 1.0, 0.56, 0.32, and 0.18 ?m). Samples were obtained at morning (06:00-09:00), noon (11:00-14:00), afternoon (16:00-19:00) and evening (21:00-24:00) local time. Absorption and scattering coefficients, and particles concentration (0.01-3 ?m aerodynamic diameter) were measured simultaneously using a PASP absorption photometer (operated at 550 nm), a portable integrating nephelometer (at 530 nm) and a CNI particle counter. TEM images of particles were acquired at different magnifications using a CM 200 Phillips TEM-EDAX system. The morphology of atmospheric particles for two aerodynamic diameters (0.18 and 1.8 ?m) was compared using border-based fractal dimension. Particles sampled under Mexico City pollution influence showed not much variability, suggesting the presence of more compact particles in smaller sizes (d50 = 1.8 ?m) at the site. The presence of higher numbers of compact particles can be attributed to aerosol aging and secondary aerosol formation, among others. Under early morning conditions, smaller particles (d50 = 0.18 ?m) had more irregular features resulting in a higher average fractal dimension. Energy dispersive X-ray spectroscopy (EDS) was used to determine the elemental composition of particles. EDS analysis in particles with d50 = 0.18 ?m showed a higher content of carbonaceous material and relevant amounts of Si, Fe, K, and Co. This may indicate an impact from industrial and vehicle's emissions on atmospheric particles.

Carabali, G.; Mamani-Paco, R.; Castro, T.; Peralta, O.; Herrera, E.; Trujillo, B.

2011-05-01

75

Status and potential of atmospheric plasma processing of materials  

SciTech Connect

This paper is a review of the current status and potential of atmospheric plasma technology for materials processing. The main focus is the recent developments in the area of dielectric barrier discharges with emphasis in the functionalization of polymers, deposition of organic and inorganic coatings, and plasma processing of biomaterials. A brief overview of both the equipment being used and the physicochemical reactions occurring in the gas phase is also presented. Atmospheric plasma technology offers major industrial, economic, and environmental advantages over other conventional processing methods. At the same time there is also tremendous potential for future research and applications involving both the industrial and academic world.

Pappas, Daphne [United States Army Research Laboratory, Aberdeen Proving Ground, Maryland 21005 (United States)

2011-03-15

76

Atmospheric giant particles (iberulites) from African desert soils and human health  

NASA Astrophysics Data System (ADS)

Earth is twice as dusty as in 19th century. The amount of soil dust in the Earth's atmosphere has doubled over the last century. The circum-Mediterranean area has one of the highest dust accretion rates in the world. The larger deserts (Sahara, Gobi, Badai Jaran, etc.) are the primary sources of mobilized desert-dust top soil that move great distances through the troposphere each year. Erosion, atmospheric transport, and dust-sized soil particles deposition to earth's surface are important process in aeolian environments. Atmospheric dust is associated to global climate change. Iberulites are giant microspherulitic particles (87.9 × 27.6 µm) rounded and reddish, generated in the atmosphere (troposphere) by coalescence of smaller particles, finally falling to the earth's surface. The name comes from the Iberian Peninsula where they were discovered. An iberulite is a co-association with axial geometry, consisting of well-defined mineral grains, together with non-crystalline compounds, structured around a coarse-grained core with a smectite rind, only one vortex and pinkish color formed in the troposphere by complex aerosol-water-gas interactions. Sedimentable dust ("dry deposition") in the city of Granada (Spain) for 17 African dust intrusion events occurring in the summer months of 2010 has been studied. In all samples were detected (SEM, stereomicroscope) iberulites. Total dust and the iberulites are composed mainly by mineral particles of different nature (XRD and SEM-EDX) and size less than 10µm (laser technique), implying dangerousness by inhalation. In the total dust the dominant mineral is dolomite [CaMg(CO3)2], abundant in the surroundings of the city; in the iberulites dominates the quartz (SiO2), which indicates Saharan origin. The iberulites and the total dust are associated with metals (ICP-MS) that have a capacity to transport electrons with a high toxic potential in the body. The concentration of Cu and Pb in total dust were 5 and 2.5 times higher than the soil background values of Granada province. In the iberulites we have detected (SEM-EDX) biological material (bacteria, diatoms, nanoplankton, etc.) which allows to emit a hypothesis about their role as vectors (atmospherical "shuttles") for alloctonous diseases. Recently has been observed the role of Saharan dust in the relationship between particulate matter and short-term daily mortality among the elderly in Madrid (Spain).

Párraga, Jesús; Delgado, Gabriel; Bech, Jaume; Martín-García, Juan Manuel; Delgado, Rafael

2013-04-01

77

Light scattering by systems of radially nonuniform atmospheric particles  

Microsoft Academic Search

The characteristics of light scattering by polydisperse systems of aerosol particles are analyzed under the assumption of a smooth nonuniformity of the refractive index. These characteristics are compared with those of polydisperse systems of uniform particles and two-layer particles. The total light extinction by such systems is shown to be insensitive to the internal structure of the particles, the degree

A. P. Prishivalko; V. A. Babenko

1979-01-01

78

Efficient Collection of Atmospheric Aerosols with a Particle Concentrator—Electrostatic Precipitator Sampler  

Microsoft Academic Search

A novel particle sampling methodology developed recently by our group (Han et al. 2008) has been extended in this article to collect atmospheric particles in electrostatic precipitators (ESPs) for chemical and biological–toxicological analysis. Particles are grown to super-micron droplets via condensation of ultrapure deionized water, and concentrated by virtual impaction in the versatile aerosol concentration enrichment system (VACES). The grown

Bangwoo Han; Neelakshi Hudda; Zhi Ning; Yong-Jin Kim; Constantinos Sioutas

2009-01-01

79

Particle size distributions of the cloud layer of the Venus atmosphere (The VEGA experiment)  

Microsoft Academic Search

Vega-probe measurements of particle size distributions in the Venus cloud layer indicate that only the accumulation mode operates on the nocturnal side of the planet; this mode is characteristic for aerosols formed through the transformation of gaseous components of the atmosphere into particles. This mode corresponds to the first mode in the Pioneer-Venus distributions; however, larger particles of the second

Iu. V. Zhulanov; L. M. Mukhin; D. F. Nenarokov; A. A. Lushnikov; I. V. Petrianov-Sokolov

1987-01-01

80

Atmospheric particle number size distribution in central Europe: Statistical relations to air masses and meteorology  

Microsoft Academic Search

Atmospheric particle number size distributions determined over 1.5 years at a central European site were statistically analyzed in terms of their relation to time of day, season, meteorology, and synoptic-scale air masses. All size distributions were decomposed into lognormal particle modes corresponding to the accumulation, Aitken, aged nucleation, and nucleation modes. The concentration of nucleation mode particles (30 nm) lacked

Wolfram Birmili; Alfred Wiedensohler; Jost Heintzenberg; Katrin Lehmann

2001-01-01

81

On the stationary charge distribution on aerosol particles in a bipolar ionic atmosphere  

Microsoft Academic Search

Summary By the «limiting sphere» method the combination coefficients for gaseous ions and aerosol particles were calculated, allowing for the jump in ion concentration at the surface of the particles. Hence the stationary charge distribution on aerosol particles in a symmetrical bipolar ionic atmosphere was determined. The use of the Boltzmann equation for this purpose proposed by some authors is

N. A. Fuchs

1963-01-01

82

Materials processing with atmospheric-pressure plasma jets  

Microsoft Academic Search

Summary form only given. Atmospheric-pressure plasma jets can be used for a wide range of materials processing applications, including surface cleaning and modification, selective etching, and thin-film deposition. The plasma source consists of two closely spaced electrodes through which helium and other gases flow (O2, CF4, etc.). A variety of electrode configurations can be used, and the source is suitable

R. Hicks; J. Jeong; S. Babayan; A. Schuetze; Jaeyoung Park; H. Herrmann; I. Henins; G. Selwyn

1998-01-01

83

Calorimetric particle detectors with superconducting absorber materials  

NASA Astrophysics Data System (ADS)

Massive superconducting absorbers of molybdenum and vanadium are used as low temperature calorimeter particle detectors. The high temperature resolution of the thermometry system, consisting of a superconducting phase transition thermometer monitored with a DC Squid, enables the detection of alpha particles with large single crystals. With a 35 g molybdenum single crystal, an energy resolution of 10 percent Full Width Half Maximum (FWHM) on 5.8 MeV alpha particles is obtained. The observed temperature rise of 1.2 mK is a factor of eight less than expected from the calculated heat capacity. Using a 15g vanadium single crystal, the energy resolution in 5.8 MeV alpha particles is 1.2 percent FWHM. In this case, the pulse height is a factor of five smaller than expected from the calculated heat capacity. A possible reason for the large deviations from the expected heat capacity is the presence of hydrogen dissolved in these transition metals, another reason might be the presence of surface impurities or defects.

Forster, G.; Ferger, P.; Feilitzsch, F. V.; Moessbauer, R. L.; Azgui, F.; Igalson, J.

1991-11-01

84

Permanent-magnet material applications in particle accelerators  

SciTech Connect

The modern charged particle accelerator has found application in a wide range of scientific research, industrial, medical, and defense fields. Researchers began to use permanent-magnet materials in particle accelerators soon after the invention of the alternating gradient principle, which showed that magnetic field could be used to control the transverse envelope of charged particle beams. The history of permanent-magnet use in accelerator physics and technology is outlined, current design methods and material properties of concern for particle accelerator applications are reviewed.

Kraus, R.H. Jr.

1992-07-01

85

Permanent-magnet material applications in particle accelerators  

SciTech Connect

The modern charged particle accelerator has found application in a wide range of scientific research, industrial, medical, and defense fields. Researchers began to use permanent-magnet materials in particle accelerators soon after the invention of the alternating gradient principle, which showed that magnetic field could be used to control the transverse envelope of charged particle beams. The history of permanent-magnet use in accelerator physics and technology is outlined, current design methods and material properties of concern for particle accelerator applications are reviewed.

Kraus, R.H. Jr.

1992-01-01

86

Atmospheric aging of Asian Dust particles during long range transport  

Microsoft Academic Search

Variations of mixing state and chemical constituents of Asian Dust (AD) particles having different transport pathways were investigated by measuring hygroscopicity and volatility of size-selected (1 ?m) dust particles, and their morphology and elemental composition in Gwangju, Korea. Also, hygroscopicity and volatility of possible candidate chemical species that can be included in the dust particles was measured in a laboratory

Jae-Seok Kim

2012-01-01

87

Secondary Cosmic Ray Particles Due to GCR Interactions in the Earth's Atmosphere  

SciTech Connect

Primary GCR interact with the Earth's atmosphere originating atmospheric showers, thus giving rise to fluxes of secondary particles in the atmosphere. Electromagnetic and hadronic interactions interplay in the production of these particles, whose detection is performed by means of complementary techniques in different energy ranges and at different depths in the atmosphere, down to the Earth's surface. Monte Carlo codes are essential calculation tools which can describe the complexity of the physics of these phenomena, thus allowing the analysis of experimental data. However, these codes are affected by important uncertainties, concerning, in particular, hadronic physics at high energy. In this paper we shall report some results concerning inclusive particle fluxes and atmospheric shower properties as obtained using the FLUKA transport and interaction code. Some emphasis will also be given to the validation of the physics models of FLUKA involved in these calculations.

Battistoni, G.; /Milan U. /INFN, Milan; Cerutti, F.; /CERN; Fasso, A.; /SLAC; Ferrari, A.; /CERN; Garzelli, M.V.; /Milan U. /INFN, Milan; Lantz, M.; /Goteborg, ITP; Muraro, S. /Milan U. /INFN, Milan; Pinsky, L.S.; /Houston U.; Ranft, J.; /Siegen U.; Roesler, S.; /CERN; Sala, P.R.; /Milan U. /INFN, Milan

2009-06-16

88

Sublimation of ice particles from rocket exhausts in the upper atmosphere  

NASA Astrophysics Data System (ADS)

The process of sublimation of ice particles from a rocket exhaust in the upper atmosphere is examined. Heating by solar radiation and losses of energy by means thermal radiation and sublimation are taken into account in the thermal balance of the ice particles. The time dependences of size and temperature of the ice particles are obtained. An estimation of water vapor concentration around the rocket trajectory is made. The process of sublimation of the rocket exhaust ice particles may be important for the interpretation of optical phenomena in the upper atmosphere connected with rocket launches and for propagation of disturbances at a large distance from the rocket.

Platov, Y. V.; Kosch, M. J.

2003-12-01

89

Studies of Physicochemical Processes in Atmospheric Particles and Acid Deposition.  

NASA Astrophysics Data System (ADS)

A comprehensive chemical mechanism for aqueous -phase atmospheric chemistry was developed and its detailed sensitivity analysis was performed. The main aqueous-phase reaction pathways for the system are the oxidation of S(IV) to S(VI) by H_2O_2 , OH, O_2 (catalysed by Fe ^{3+} and Mn^ {2+}), O_3 and HSO_sp{5}{-}. The gas-phase concentrations of SO_2, H_2O_2, HO _2, OH, O_3 HCHO, NH_3, HNO_3 and HCl and the liquid water content of the cloud are of primary importance. The Lagrangian model predictions for temperature profile, fog development, liquid water content, gas-phase concentrations of SO_2 , HNO_3, and NH_3 , pH, aqueous-phase concentrations of SO _sp{4}{2-}, NH _sp{4}{+} and NO _sp{3}{-}, and finally deposition rates of the above ions match well the observed values. A third model was developed to study the distribution of acidity and solute concentration among the various droplet sizes in a fog or a cloud. Significant solute concentration differences can occur in aqueous droplets inside a fog or a cloud. Fogs in polluted environments have the potential to increase aerosol sulfate concentrations, but at the same time to cause reductions in the aerosol concentration of nitrate, chloride, ammonium and sodium as well as in the total aerosol mass concentration. The sulfate producd during fog episodes favors the aerosol particles that have access to most of the fog liquid water. Aerosol scavenging efficiencies of around 80% were calculated for urban fogs. Sampling and subsequent mixing of fog droplets of different sizes may result in measured concentrations that are not fully representative of the fogwater chemical composition. Isoprene and beta-pinene, at concentration levels ranging from a few ppb to a few ppm were reacted photochemically with NO_ {x} in the Caltech outdoor smog chamber facility. Aerosol formation from the isoprene photooxidation was found to be negligible even under extreme ambient conditions due to the relatively high vapor pressure of its condensable products. Aerosol carbon yield from the beta -pinene photooxidation is as high as 8% and depends strongly on the initial HC/NO_{x} ratio. Monoterpene photooxidation can be a significant source of secondary aerosol in rural environments and in urban areas with extended natural vegetation. (Abstract shortened with permission of author.).

Pandis, Spyros N.

90

Control Experiment of Positively Charged Fine Particles at the Atmospheric Pressure  

NASA Astrophysics Data System (ADS)

It is already reported that the negatively charged fine particle flow was controlled by application of external electric field. The control of positively charged fine particles was examined in this experiment. The fine particles are able to take charges in the air under the atmospheric pressure by irradiation of UV light. The control of the positively charged fine particles has been attempted by the external electric field applied the negative potential. The fine particles for experiments are volcanic ashes, nylon 16, glass, and ice. Experiment was performed in the T-shaped glass chamber under the atmospheric pressure. The halogen lamp (500 W) was used to exit the electrons from particles by photo-emission. The ring and disk electrodes to control the positively charged particles were set at the bottom of chamber. The parallel electrodes were set at the middle of chamber and horizontal static electric fields (E = 0 ~ 210 V/cm) were created in order to estimate the charge of fine particles. The charges of particle were estimated by the deflection of particle trajectory in the static electric fields and particle velocity. The estimated charges were 104e ~ 5×106e and 103e ~ 105e for volcanic ashes and nylon 16, respectively. When positively charged particles were introduced into collecting electrodes, the fine particles are collected in the electrodes. The result of control of positively charged fine particles is shown in this conference.

Yokota, Toshiaki; Sato, Noriyoshi; Ando, Ayumi

2005-10-01

91

Recreational atmospheric pollution episodes: Inhalable metalliferous particles from firework displays  

Microsoft Academic Search

The use of fireworks creates an unusual and distinctive anthropogenic atmospheric pollution event. We report on aerosol samples collected during Las Fallas in Valencia, a 6-day celebration famous for its firework displays, and add comparative data on firework- and bonfire-contaminated atmospheric aerosol samples collected from elsewhere in Spain (Barcelona, L’Alcora, and Borriana) and during the Guy Fawkes celebrations in London.

Teresa Moreno; Xavier Querol; Andrés Alastuey; Mari Cruz Minguillón; Jorge Pey; Sergio Rodriguez; José Vicente Miró; Carles Felis; Wes Gibbons

2007-01-01

92

Particles on droplets: From fundamental physics to novel materials  

Microsoft Academic Search

We review the phenomenon of adsorption of colloidal particles at interfaces between two immiscible liquids, such as on the surfaces of droplets. Though the tendency of small particles to adsorb at liquid interfaces has been under investigation for nearly a century, attention to many aspects of the problem has recently grown, in part because of the tremendous potential for materials

C. Zeng; H. Bissig; A. D. Dinsmore

2006-01-01

93

1H NMR application for characterizing water-soluble organic compounds in urban atmospheric particles.  

PubMed

Water-soluble organic compounds (WSOC) in urban atmospheric particles separated by particle size were analyzed by 1H NMR. This is the first utilization of 1H NMR for characterizing WSOC in atmospheric particles. The WSOC dissolved in D2O were analyzed without a separation procedure. Twelve low molecular weight WSOC could be identified and their atmospheric concentrations determined. One of these, monomethyl hydrogen sulfate (MHS), was first detected in an urban area where no oil or coal power plant existed. Methanesulfonic acid (MSA) and hydroxymethanesulfonic acid (HMSA) were detected as major organosulfur compounds. Relatively high concentrations of these low molecular weight WSOC were observed in the particle diameter range of 0.43-1.1 microns. Many complex signals at 3-4 ppm in the NMR spectrum were seen only for the coarse particle samples (1.1 microns < particle diameter). Mannitol was believed to exist in the coarse particles as a major polyol corresponding to these signals. On the other hand, a large broad signal, observed at 2.5-3 ppm, was mostly present in the fine particles. Finally, it was believed that a major part of the WSOC in urban atmospheric fine particles is attributed to ketocarboxylic acids, ketodicarboxylic acids, and dicarboxylic acids. PMID:11452589

Suzuki, Y; Kawakami, M; Akasaka, K

2001-07-01

94

Superparamagnetic Fe3O4 particles formed by oxidation of pyrite heated in an anoxic atmosphere  

USGS Publications Warehouse

As a follow-up to previous gas analysis experiments in which pyrite was heated to 681 K in an anoxic (oxygen starved) atmosphere, the first oxidation product, FeSO4, was studied as a bulk material. No decomposition of FeSO4 to Fe3O4 was observed in the temperature range studied. The lack of decomposition of bulk FeSO4 to Fe3O4 suggests that FeS2 oxidizes directly to Fe3O4, or that FeSO4, FeS2 and O2 react together to form Fe3O4. Magnetic susceptibility and magnetization measurements, along with magnetic hysteresis curves, show that small particles of Fe3O4 form on the pyrite surface, rather than a continuous layer of bulk Fe3O4. A working model describing the oxidation steps is presented. ?? 1990.

Thorpe, A. N.; Senftle, F. E.; Talley, R.; Hetherington, S.; Dulong, F.

1990-01-01

95

PD-FiTE - an efficient method for calculating gas / liquid equilibria in atmospheric aerosol particles  

NASA Astrophysics Data System (ADS)

Assessing the impact of atmospheric aerosol particles on the environment requires adequate representation of appropriate key processes within large scale models. In the absence of primary particulate material, interactions between the atmospheric gaseous components and particles means that the chemical nature of the particles is largely determined by the availability of condensable gaseous material, such as sulphuric and nitric acids, and by the ambient environmental conditions. Gas to particle mass transfer of semi-volatile components,driven by a difference in equilibrium and actual partial pressures above an aerosol particle, is an important factor in determining the evolving chemical composition of the particle and is necessary for predicting aerosol loading and composition. The design of an appropriate framework required for parameterizations of key variables is challenging. These thermodynamic frameworks are often numerically very complex, resulting in significant computational expense. Three dimensional chemical and aerosol transport models demand that computational expense be kept at a minimum,resulting in a trade-off between accuracy and efficiency. To calculate the equilibrium vapour pressure above a solution requires treatment of solution nonideality. This is manifest through activity coefficients of components pertinent to each condensing specie. However, activity coefficients are complex functions of the solution composition. Parameterisation of activity coefficients provides the main focus of this work largely because reducing the numerical complexity whilst retaining a good level of accuracy is very challenging. The approach presented here, the hybrid Partial Derivative Fitted Taylor Expansion (PDFiTE) (Topping et al 2008), builds on previously reported work, with an aim to derive parameters for an accurate and computationally efficient framework through coupling with a complex thermodynamic model. Such a reduction in complexity is important as it is necessary to further include an as yet unspecified number of condensing organic species, thus increasing the computational burden of any existing framework. Using this coupled approach we derive optimised model parameters describing the interaction between different chemical components, resulting in a significant increase in computational performance, in some cases giving a four fold decrease in the required number of floating point operations, whilst remaining accurate. Overall, comparisons with the most accurate inorganic activity coefficient model available (Clegg et al1998) and an existing parameterisation (MTEM) (Zaveri et al 2005) indicate that the methodology behind PD-FiTE gives an increase in accuracy for calculating the vapour pressure of all condensing gases when averaged over the parameterisation space of the system H+-NH4+-Na+-SO42--HSO4--NO3--Cl-. Following this, the reduced parameterisation is coupled into a combined chemistry / microphysical aerosol model in a dynamical simulation of aerosol composition. This demonstrates the robustness of our model and also demonstrates the implications of its use. As a simple test case we investigate the response of a typical marine aerosol passing through a polluted environment. This shows the robustness of PD-FiTE and illustrates its usefulness in capturing the fine details of important phenomena such as the outgassing of HCl in response to HNO3 uptake by sea-salt particles. Further, since semi-volatile organic compounds are ubiquitous and secondary organic aerosol is thought to be a major fraction of submicron aerosol mass, the inclusion of organic compounds into the framework will be reported. References: Clegg, S. L., et al. (1992), Thermodynamics of Multicomponent, Miscible, Ionic-Solutions .2. Mixtures Including Unsymmetrical Electrolytes,Journal of Physical Chemistry, 96, 9470-9479. Topping, D.O. et al (2008). An Efficient and Accurate Scheme for the Partitioning of Atmospheric Semi-Volatile Components - 1 Inorganic Compounds. Submitted to Journal of Geophysical Research. Zaveri, R. A., et al. (2005),

Topping, D.; Lowe, D.; McFiggans, G.; Barley, M.

2009-04-01

96

Energetic Charged-Particle Interactions with Atmospheres and Surfaces  

Microsoft Academic Search

The surfaces of interstellar and interplanetary grains, planetary satellites, ring particles, asteroids, Mercury and the Moon, etc. are all directly exposed to radiations. Solar wind, magnetospheric plasmas, cosmic rays, solar energetic particles, and U.V. photons can all produce chemical and physical alterations. These alterations affect the surface reflection properties and can eject species into the gas phase affecting the ambient

Robert E. Johnson

1990-01-01

97

MEASURED ATMOSPHERIC NEW PARTICLE FORMATION RATES: IMPLICATIONS FOR NUCLEATION MECHANISMS  

Microsoft Academic Search

Measured production rates of tropospheric ultrafine particles (˜3nm diameter) are reported for the first time and are shown to be orders of magnitude greater than nucleation rates predicted by the binary theory of homogeneous nucleation for sulfuric acid and water. Furthermore, the functional dependence of observed particle formation rates on sulfuric acid vapor concentrations is much weaker than predicted by

R. J. WEBER; J. J. MARTI; P. H. McMURRY; F. L. EISELE; D. J. TANNER; A. JEFFERSON

1996-01-01

98

Interaction of Suspended Atmospheric Particles with Laser Radiation.  

National Technical Information Service (NTIS)

The laser flux required to initiate gas breakdown is lowered when the gas contains suspended particles. Initial breakdown in either the vaporized particle or in the shock-heated adjacent gas may result in a laser-supported detonation or in a subsonic ioni...

A. A. Boni J. R. Triplett

1972-01-01

99

Erosion tests of materials by energetic particle beams  

SciTech Connect

The internal components of magnetic fusion devices must withstand erosion from and high heat flux of energetic plasma particles. The selection of materials for the construction of these components is important to minimize contamination of the plasma. In order to study various materials' comparative resistance to erosion by energetic particles and their ability to withstand high heat flux, water-cooled copper swirl tubes coated or armored with various materials were subjected to bombardment by hydrogen and helium particle beams. Materials tested were graphite, titanium carbide (TiC), chromium, nickel, copper, silver, gold, and aluminum. Details of the experimental arrangement and methods of application or attachment of the materials to the copper swirl tubes are presented. Results including survivability and mass losses are discussed.

Schechter, D.E.; Tsai, C.C.; Sluss, F.; Becraft, W.R.; Hoffman, D.J.

1985-01-01

100

Scanning Electron Microanalysis and Analytical Challenges of Mapping Elements in Urban Atmospheric Particles  

EPA Science Inventory

Elemental mapping with energy-dispersive X-ray spectroscopy (EDX) associated with scanning electron microscopy is highly useful for studying internally mixed atmospheric particles. Presented is a study of individual particles from urban airsheds and the analytical challenges in q...

101

Trajectory Models for Heavy Particles in Atmospheric Turbulence: Comparison with Observations  

Microsoft Academic Search

The simplest ''random flight'' models for the paths of heavy particles in turbulence have been tested against previous observations of the deposition of glass beads from an elevated source in the atmospheric surface layer. For the bead sizes examined (diameter 50-100 mm), for which the ratio of particle inertial timescale to turbulence timescale t p\\/GL K 1, it was found

John D. Wilson

2000-01-01

102

Laboratory Study of Simulated Atmospheric Transformations of Chromium in Ultrafine Combustion Aerosol Particles  

Microsoft Academic Search

While atmospheric particles can have adverse health effects, the reasons for this toxicity are largely unclear. One possible reason is that the particles can contain toxic metals such as chromium. Chromium exists in the environment in two major oxidation states: III, which is an essential nutrient, and VI, which is highly toxic and carcinogenic. Currently little is known about the

Michelle Werner; Peter Nico; Bing Guo; Ian Kennedy; Cort Anastasio

2006-01-01

103

Study of inlet materials for sampling atmospheric nitric acid  

SciTech Connect

The adsorption of nitric acid (HNO{sub 3}) from a flowing gas stream is studied for a variety of wall materials to determine their suitability for use in atmospheric sampling instruments. Parts per billion level mixtures of HNO{sub 3} in synthetic air flow through tubes of different materials such that >80% of the molecules interact with the walls. A chemical ionization mass spectrometer with a fast time response and high sensitivity detects HNO{sub 3} that is not adsorbed on the tube walls. Less than 5% of available HNO{sub 3} is adsorbed on Teflon fluoropolymer tubing after 1 min of HNO{sub 3} exposure, whereas >70% is lost on walls made of stainless steel, glass, fused silica, aluminum, nylon, silica-steel, and silane-coated glass. Glass tubes exposed to HNO{sub 3} on the order of hours passivate with HNO{sub 3} adsorption dropping to zero. The adsorption of HNO{sub 3} on PFA Teflon tubing (PFA) is nearly temperature-independent from 10 to 80 C, but below {minus}10 C nearly all HNO{sub 3} that interacts with PFA is reversibly adsorbed. In ambient and synthetic air, humidity increases HNO{sub 3} adsorption. The results suggest that Teflon at temperatures above 10 C is an optimal choice for inlet surfaces used for in situ measurements of HNO{sub 3} in the ambient atmosphere.

Neuman, J.A.; Huey, L.G.; Ryerson, T.B.; Fahey, D.W. [NOAA, Boulder, CO (United States)]|[Univ. of Colorado/NOAA, Boulder, CO (United States). Cooperative Inst. for Research in Environmental Sciences

1999-04-01

104

[Atmospheric particle formation events in Nanjing during summer 2010].  

PubMed

Feature of aerosol particle number concentration, condition and impact factor of new particle formation (NPF) were investigated in Nanjing during summer. In this study, aerosol particle number concentration and gaseous pollutants (O3, SO2 and NO2) measurements were carried out by Wide-Range Particle Spectrometer (WPS) and Differential Optical Absorption Spectroscopy (DOAS) in July 2010. Combining with observations from Automatic Weather Station and Backward Trajectory Simulation, the condition and impact factor of NPF were discussed. Results showed that the averaged 10-500 nm particle number concentration was 1.7 x 10(4) cm(-3), similar to some typical observation values in North American and Europe; the 10-25 nm particle number concentration accounted for 25% of the total number concentration. Six NPF events occurred during observation. We analyzed that stable wind speed and direction, strong solar radiation promoted the NPF. The humidity during NPF event varied from 50% to 70%. Results indicated that clean ocean air mass brought from easterly and southerly wind promoted the NPF by Backward Trajectory Model Simulation. During the NPF event, the 10 - 25 nm particle number concentration positively correlated with the concentration of SO2, and negatively correlated with O3, whereas poorly correlated with NO2. PMID:22624358

Wang, Hong-Lei; Zhu, Bin; Shen, Li-Juan; Kang, Han-Qing; Diao, Yi-Wei

2012-03-01

105

Measurements of the Particle Size Distribution of the Atmospheric Aerosol: I. Introduction and Experimental Methods  

Microsoft Academic Search

Previous experimental measurements of particle size spectra of the atmospheric aerosol are reviewed. A four-stage impactor was used to sample the Baltimore aerosol in the size range above 0.4 microns in radius. Particle size was measured with an optical microscope. The size range below 0.1 microns was sampled with a novel rotating disk device and the particle size distribution was

S. K. Friedlander; Ralph E. Pasceri

1965-01-01

106

Non-ammonium reduced nitrogen species in atmospheric aerosol particles  

SciTech Connect

The traditional belief that ambient aerosol particles contain nitrogen predominantly in the form of inorganic ionic species such as NH/sub 4//sup +/ and NO/sub 3//sup -/ was challenged about 10 years ago by results from x-ray photoelectron spectroscopic analysis (ESCA) of California aerosol particles. A significant fraction (approx. 50%) of the reduced nitrogen was observed to have an oxidation state more reduced than ammonium, characteristic of organic nitrogen species. We have used a recently developed thermal evolved gas analysis method (NO/sub x/) in conjunction with ESCA to confirm the existence of these species in aerosol particles collected in both the United States and Europe. The agreement of EGA and ESCA analyses indicates that these species are found not only on the surface but also throughout the particles. 9 references, 6 figures.

Dod, R.L.; Gundel, L.A.; Benner, W.H.; Novakov, T.

1983-08-01

107

Simulation on particle crushing of tailings material under high pressure  

NASA Astrophysics Data System (ADS)

With continuous increase of the high tailings dam, it has an important practical and theoretical significance to study the mechanical characteristics of the tailings material under high pressures. It is indicated that strength envelopes of the tailings material have a remarkable nonlinear characteristics through the triaxial test under high pressures. A further study stated that the particle crushing has a critical effect on the mechanical behavior of the tailings material. In order to quantitatively research its influence, the grain size distribution of the tailings material is analyzed for pre-and post-test and the particle crushing of the tailings material is measured. The particle flow code is employed to simulate and monitor the sample during testing. Firstly, a model which considers the particle crushing is built under the plane strain condition. Then, a series of biaxial numerical tests of the tailings specimen are simulated by using the model. It is found that the simulation result agrees with the triaxial test. Finally, a law between the particle crushing and strain of the tailings material under different confining pressures is obtained.

Liu, Hai-ming; Liu, Yi-ming; Yang, Chun-he; Cao, Jing

2013-06-01

108

Erosion of aerospace materials by solid-particle impact  

NASA Astrophysics Data System (ADS)

The degradation of various aerospace window materials by the action of solid particle impact is investigated. Laboratory simulations of high velocity sand, dust and hail impacts have been carried out, and the damage assessed in terms of the reductions in optical and mechanical performance. A new erosion rig has been designed to cover the broad size and velocity range of airborne particulates encountered by moving craft, and an ice-firing gas-gun was used to simulate hail impacts. IR-transmitting materials studied include CVD diamond, sapphire and coated zinc sulphide. A radar-dome composite material was compared with polymethylmethacylate (PMMA) for hail impact. Nylon spheres were assessed as a convenient simulation for ice and were found to cause very similar damage over parts of the velocity range studied. The different damage mechanisms observed in these materials are discussed and the extent of degradation by multi-particle erosion related to the particle size and impact velocity.

Telling, Robert H.; Jilbert, G. H.; Field, John E.

1997-06-01

109

Formation and growth of atmospheric particles at a forest site in the southeast US  

NASA Astrophysics Data System (ADS)

Atmospheric particle size distribution measurements (10 <= aerodynamic diameter, Dp <= 250 nm), which took place above a loblolly pine plantation in the Southeast U.S. from November 2005 to September 2007, were made using Scanning Mobility Particle Sizer (SMPS). The size distributions were investigated to identify new particle formation and to classify the new particle formation episodes into different event classes based on the behavior of particle size distribution and particle growth pattern. About 69% of the observation days had nucleation. The event frequency was highest in spring and lowest in winter. The particle growth rate was highest in May (5.0 +/- 3.6 nm hr-1) and lowest in February (1.2 +/- 2.2 nm hr-1) with an annual average particle growth rate of 2.5 +/- 0.3 nm hr-1. Nucleation frequency and event types are examined along with associated meteorological and chemical conditions.

Pillai, Priya; Walker, John; Khlystov, Andrey; Aneja, Viney

2013-05-01

110

Studies of Physicochemical Processes in Atmospheric Particles and Acid Deposition  

Microsoft Academic Search

A comprehensive chemical mechanism for aqueous -phase atmospheric chemistry was developed and its detailed sensitivity analysis was performed. The main aqueous-phase reaction pathways for the system are the oxidation of S(IV) to S(VI) by H_2O_2 , OH, O_2 (catalysed by Fe ^{3+} and Mn^ {2+}), O_3 and HSO_sp{5}{-}. The gas-phase concentrations of SO_2, H_2O_2, HO _2, OH, O_3 HCHO, NH_3,

Spyros N. Pandis

1991-01-01

111

DETERMINATION OF THE STRONG ACIDITY OF ATMOSPHERIC FINE PARTICLES (  

EPA Science Inventory

This report is a standardized methodology description for the determination of strong acidity of fine particles (less than 2.5 microns) in ambient air using annular denuder technology. his methodology description includes two parts: art A - Standard Method and Part B - Enhanced M...

112

Behavior of alumina particles in atmospheric pressure plasma jets.  

National Technical Information Service (NTIS)

The distribution of Al(sub 2)O(sub 3) particle size, velocity and temperature was mapped over the flow field of a 31.5 kW plasma torch. The effects of varying the powder loading were studied. The powder feed rate was varied between .45 and 2.05 kg/hr inde...

J. R. Fincke W. D. Swank

1990-01-01

113

Modelling the formation of organic particles in the atmosphere  

NASA Astrophysics Data System (ADS)

Particle formation resulting from activation of inorganic stable clusters by a supersaturated organic vapour was investigated using a numerical model. The applied aerosol dynamic model included a detailed description of the activation process along with a treatment of the appropriate aerosol and gas-phase processes. The obtained results suggest that both gaseous sulphuric acid and organic vapours contribute to organic particle formation in continental background areas. The initial growth of freshly-nucleated clusters is driven mainly by condensation of gaseous sulphuric acid and by a lesser extent self-coagulation. After the clusters have reached sizes of around 2 nm in diameter, low-volatile organic vapours start to condense spontaneously into the clusters, thereby accelerating their growth to detectable sizes. A shortage of gaseous sulphuric acid or organic vapours limit, or suppress altogether, the particle formation, since freshly-nucleated clusters are rapidly coagulated away by pre-existing particles. The obtained modelling results were applied to explaining the observed seasonal cycle in the number of aerosol formation events in a continental forest site.

Anttila, T.; Kerminen, V.-M.; Kulmala, M.; Laaksonen, A.; O'Dowd, C. D.

2004-07-01

114

Heating of dust particles enclosed in icy material  

NASA Astrophysics Data System (ADS)

'Dirty ice' is known to exist on the surfaces of comet nuclei and on the surfaces of many natural satellites in the outer solar system. In this paper the thermal behavior of dark dust particles enclosed in icy material is studied under the assumption that a certain fraction of the solar radiation can penetrate the ice and heat the particle directly. It is found that the area contact between the particle and the ice must be quite small in order to heat even a 'large' particle significantly above the temperature of the surrounding bulk ice. Under realistic assumptions for the area contact parameter micron-sized particles become hardly hotter than the surrounding bulk ice.

Komle, N. I.; Ulamec, S.

1989-02-01

115

Discrete Particle Swarm Optimization with Scout Particles for Library Materials Acquisition  

PubMed Central

Materials acquisition is one of the critical challenges faced by academic libraries. This paper presents an integer programming model of the studied problem by considering how to select materials in order to maximize the average preference and the budget execution rate under some practical restrictions including departmental budget, limitation of the number of materials in each category and each language. To tackle the constrained problem, we propose a discrete particle swarm optimization (DPSO) with scout particles, where each particle, represented as a binary matrix, corresponds to a candidate solution to the problem. An initialization algorithm and a penalty function are designed to cope with the constraints, and the scout particles are employed to enhance the exploration within the solution space. To demonstrate the effectiveness and efficiency of the proposed DPSO, a series of computational experiments are designed and conducted. The results are statistically analyzed, and it is evinced that the proposed DPSO is an effective approach for the studied problem.

Lin, Bertrand M. T.

2013-01-01

116

Discrete particle swarm optimization with scout particles for library materials acquisition.  

PubMed

Materials acquisition is one of the critical challenges faced by academic libraries. This paper presents an integer programming model of the studied problem by considering how to select materials in order to maximize the average preference and the budget execution rate under some practical restrictions including departmental budget, limitation of the number of materials in each category and each language. To tackle the constrained problem, we propose a discrete particle swarm optimization (DPSO) with scout particles, where each particle, represented as a binary matrix, corresponds to a candidate solution to the problem. An initialization algorithm and a penalty function are designed to cope with the constraints, and the scout particles are employed to enhance the exploration within the solution space. To demonstrate the effectiveness and efficiency of the proposed DPSO, a series of computational experiments are designed and conducted. The results are statistically analyzed, and it is evinced that the proposed DPSO is an effective approach for the studied problem. PMID:24072983

Wu, Yi-Ling; Ho, Tsu-Feng; Shyu, Shyong Jian; Lin, Bertrand M T

2013-09-01

117

Molecular understanding of sulphuric acid-amine particle nucleation in the atmosphere.  

PubMed

Nucleation of aerosol particles from trace atmospheric vapours is thought to provide up to half of global cloud condensation nuclei. Aerosols can cause a net cooling of climate by scattering sunlight and by leading to smaller but more numerous cloud droplets, which makes clouds brighter and extends their lifetimes. Atmospheric aerosols derived from human activities are thought to have compensated for a large fraction of the warming caused by greenhouse gases. However, despite its importance for climate, atmospheric nucleation is poorly understood. Recently, it has been shown that sulphuric acid and ammonia cannot explain particle formation rates observed in the lower atmosphere. It is thought that amines may enhance nucleation, but until now there has been no direct evidence for amine ternary nucleation under atmospheric conditions. Here we use the CLOUD (Cosmics Leaving OUtdoor Droplets) chamber at CERN and find that dimethylamine above three parts per trillion by volume can enhance particle formation rates more than 1,000-fold compared with ammonia, sufficient to account for the particle formation rates observed in the atmosphere. Molecular analysis of the clusters reveals that the faster nucleation is explained by a base-stabilization mechanism involving acid-amine pairs, which strongly decrease evaporation. The ion-induced contribution is generally small, reflecting the high stability of sulphuric acid-dimethylamine clusters and indicating that galactic cosmic rays exert only a small influence on their formation, except at low overall formation rates. Our experimental measurements are well reproduced by a dynamical model based on quantum chemical calculations of binding energies of molecular clusters, without any fitted parameters. These results show that, in regions of the atmosphere near amine sources, both amines and sulphur dioxide should be considered when assessing the impact of anthropogenic activities on particle formation. PMID:24097350

Almeida, João; Schobesberger, Siegfried; Kürten, Andreas; Ortega, Ismael K; Kupiainen-Määttä, Oona; Praplan, Arnaud P; Adamov, Alexey; Amorim, Antonio; Bianchi, Federico; Breitenlechner, Martin; David, André; Dommen, Josef; Donahue, Neil M; Downard, Andrew; Dunne, Eimear; Duplissy, Jonathan; Ehrhart, Sebastian; Flagan, Richard C; Franchin, Alessandro; Guida, Roberto; Hakala, Jani; Hansel, Armin; Heinritzi, Martin; Henschel, Henning; Jokinen, Tuija; Junninen, Heikki; Kajos, Maija; Kangasluoma, Juha; Keskinen, Helmi; Kupc, Agnieszka; Kurtén, Theo; Kvashin, Alexander N; Laaksonen, Ari; Lehtipalo, Katrianne; Leiminger, Markus; Leppä, Johannes; Loukonen, Ville; Makhmutov, Vladimir; Mathot, Serge; McGrath, Matthew J; Nieminen, Tuomo; Olenius, Tinja; Onnela, Antti; Petäjä, Tuukka; Riccobono, Francesco; Riipinen, Ilona; Rissanen, Matti; Rondo, Linda; Ruuskanen, Taina; Santos, Filipe D; Sarnela, Nina; Schallhart, Simon; Schnitzhofer, Ralf; Seinfeld, John H; Simon, Mario; Sipilä, Mikko; Stozhkov, Yuri; Stratmann, Frank; Tomé, Antonio; Tröstl, Jasmin; Tsagkogeorgas, Georgios; Vaattovaara, Petri; Viisanen, Yrjo; Virtanen, Annele; Vrtala, Aron; Wagner, Paul E; Weingartner, Ernest; Wex, Heike; Williamson, Christina; Wimmer, Daniela; Ye, Penglin; Yli-Juuti, Taina; Carslaw, Kenneth S; Kulmala, Markku; Curtius, Joachim; Baltensperger, Urs; Worsnop, Douglas R; Vehkamäki, Hanna; Kirkby, Jasper

2013-10-06

118

Molecular understanding of sulphuric acid-amine particle nucleation in the atmosphere  

NASA Astrophysics Data System (ADS)

Nucleation of aerosol particles from trace atmospheric vapours is thought to provide up to half of global cloud condensation nuclei. Aerosols can cause a net cooling of climate by scattering sunlight and by leading to smaller but more numerous cloud droplets, which makes clouds brighter and extends their lifetimes. Atmospheric aerosols derived from human activities are thought to have compensated for a large fraction of the warming caused by greenhouse gases. However, despite its importance for climate, atmospheric nucleation is poorly understood. Recently, it has been shown that sulphuric acid and ammonia cannot explain particle formation rates observed in the lower atmosphere. It is thought that amines may enhance nucleation, but until now there has been no direct evidence for amine ternary nucleation under atmospheric conditions. Here we use the CLOUD (Cosmics Leaving OUtdoor Droplets) chamber at CERN and find that dimethylamine above three parts per trillion by volume can enhance particle formation rates more than 1,000-fold compared with ammonia, sufficient to account for the particle formation rates observed in the atmosphere. Molecular analysis of the clusters reveals that the faster nucleation is explained by a base-stabilization mechanism involving acid-amine pairs, which strongly decrease evaporation. The ion-induced contribution is generally small, reflecting the high stability of sulphuric acid-dimethylamine clusters and indicating that galactic cosmic rays exert only a small influence on their formation, except at low overall formation rates. Our experimental measurements are well reproduced by a dynamical model based on quantum chemical calculations of binding energies of molecular clusters, without any fitted parameters. These results show that, in regions of the atmosphere near amine sources, both amines and sulphur dioxide should be considered when assessing the impact of anthropogenic activities on particle formation.

Almeida, João; Schobesberger, Siegfried; Kürten, Andreas; Ortega, Ismael K.; Kupiainen-Määttä, Oona; Praplan, Arnaud P.; Adamov, Alexey; Amorim, Antonio; Bianchi, Federico; Breitenlechner, Martin; David, André; Dommen, Josef; Donahue, Neil M.; Downard, Andrew; Dunne, Eimear; Duplissy, Jonathan; Ehrhart, Sebastian; Flagan, Richard C.; Franchin, Alessandro; Guida, Roberto; Hakala, Jani; Hansel, Armin; Heinritzi, Martin; Henschel, Henning; Jokinen, Tuija; Junninen, Heikki; Kajos, Maija; Kangasluoma, Juha; Keskinen, Helmi; Kupc, Agnieszka; Kurtén, Theo; Kvashin, Alexander N.; Laaksonen, Ari; Lehtipalo, Katrianne; Leiminger, Markus; Leppä, Johannes; Loukonen, Ville; Makhmutov, Vladimir; Mathot, Serge; McGrath, Matthew J.; Nieminen, Tuomo; Olenius, Tinja; Onnela, Antti; Petäjä, Tuukka; Riccobono, Francesco; Riipinen, Ilona; Rissanen, Matti; Rondo, Linda; Ruuskanen, Taina; Santos, Filipe D.; Sarnela, Nina; Schallhart, Simon; Schnitzhofer, Ralf; Seinfeld, John H.; Simon, Mario; Sipilä, Mikko; Stozhkov, Yuri; Stratmann, Frank; Tomé, Antonio; Tröstl, Jasmin; Tsagkogeorgas, Georgios; Vaattovaara, Petri; Viisanen, Yrjo; Virtanen, Annele; Vrtala, Aron; Wagner, Paul E.; Weingartner, Ernest; Wex, Heike; Williamson, Christina; Wimmer, Daniela; Ye, Penglin; Yli-Juuti, Taina; Carslaw, Kenneth S.; Kulmala, Markku; Curtius, Joachim; Baltensperger, Urs; Worsnop, Douglas R.; Vehkamäki, Hanna; Kirkby, Jasper

2013-10-01

119

Mathematical modeling of atmospheric fine particle-associated primary organic compound concentrations  

NASA Astrophysics Data System (ADS)

An atmospheric transport model has been used to explore the relationship between source emissions and ambient air quality for individual particle phase organic compounds present in primary aerosol source emissions. An inventory of fine particulate organic compound emissions was assembled for the Los Angeles area in the year 1982. Sources characterized included noncatalyst- and catalyst-equipped autos, diesel trucks, paved road dust, tire wear, brake lining dust, meat cooking operations, industrial oil-fired boilers, roofing tar pots, natural gas combustion in residential homes, cigarette smoke, fireplaces burning oak and pine wood, and plant leaf abrasion products. These primary fine particle source emissions were supplied to a computer-based model that simulates atmospheric transport, dispersion, and dry deposition based on the time series of hourly wind observations and mixing depths. Monthly average fine particle organic compound concentrations that would prevail if the primary organic aerosol were transported without chemical reaction were computed for more than 100 organic compounds within an 80 km × 80 km modeling area centered over Los Angeles. The monthly average compound concentrations predicted by the transport model were compared to atmospheric measurements made at monitoring sites within the study area during 1982. The predicted seasonal variation and absolute values of the concentrations of the more stable compounds are found to be in reasonable agreement with the ambient observations. While model predictions for the higher molecular weight polycyclic aromatic hydrocarbons (PAH) are in agreement with ambient observations, lower molecular weight PAH show much higher predicted than measured atmospheric concentrations in the particle phase, indicating atmospheric decay by chemical reactions or evaporation from the particle phase. The atmospheric concentrations of dicarboxylic acids and aromatic polycarboxylic acids greatly exceed the contributions that are due to direct emissions from primary sources, confirming that these compounds are principally formed by atmospheric chemical reactions.

Rogge, Wolfgang F.; Hildemann, Lynn M.; Mazurek, Monica A.; Cass, Glen R.; Simoneit, Bernd R. T.

1996-08-01

120

Origin of nitrocatechols and alkylated-nitrocatechols in atmospheric aerosol particles  

NASA Astrophysics Data System (ADS)

Biomass burning constitutes one of the major sources of aerosol particles in most of the environments during winter. If a lot of information is available in the literature on the primary fraction of biomass burning aerosol particles, almost nothing is known regarding the formation of Secondary Organic Aerosol (SOA) from the chemical mixture emitted by this source. Recently methylated nitrocatechol have been identified in atmospheric particles collected in winter. These compounds are strongly associated with biomass burning tracers such as levoglucosan and are suspected to be of secondary origin since they can be formed through the oxidation of cresol significantly emitted by biomass burning. However, nitrocatechols are particularly difficult to analyze using classical techniques like HPLC-MS or GC-MS. In the present study, we adopt a new analytical approach. Direct analysis in real time (DART), introduced by Cody et al. (2005), allows direct analysis of gases, liquids, solids and materials on surfaces. Thus, for particles collected onto filters, the sample preparation step is simplified as much as possible, avoiding losses and reducing to the minimum the analytical procedure time. Two analytic modes can be used. In positive mode, [MH]+ ions are formed by proton transfer reaction ; whereas in negative ionization mode, [MH]-, M- and [MO2]- ions are formed. DART source enables soft ionization and produces simple mass spectra suitable for analysis of complex matrices, like organic aerosol, in only a few seconds. For this study, the DART source was coupled to a Q-ToF mass spectrometer (Synapt G2 HDMS, Waters), with a mass resolution up to 40 000. The analysis of atmospheric aerosol samples, collected in Marseille during winter 2011 (APICE project), with the DART/Q-ToF approach highlighted the abundance of nitrocatechols and alkylated nitrocatechols. Their temporal trends were also very similar to those of levoglucosan or dihydroabietic acid well known tracers of biomass burning aerosol. If their biomass burning origin's is clearly established, their secondary origin remains still not totally clear. Smog chamber experiments were then conducted in the PSI facilities to investigate the aging of biomass burning emissions. The analysis of samples collected during these experiments using the DART/Q-ToF approach, confirmed that nitrocatechols and methylated nitrocatechols originate from biomass burning processes. More importantly our results confirm that nitrocatechols and their methylated derivatives are quasi exclusively from secondary origin. Considering the abundance of biomass burning primary aerosol, and the large fraction of unexplained SOA, this result is of prime importance. Cody. R., Laramée J. Nilles J. and Durst H. : Direct Analysis in Real Time (DARTtm) Mass Spectrometry, JOEL news, 2005, 40, 1, 8-12. Kitanovski Z., Grgic I., Yasmeen F., Claeys M. and Cusak A.: Development of a liquid chromatographic method based on ultraviolet-visible and electrospray ionization mass spectrometric detection for the identification of nitrocatechols and related tracers ion biomass burning atmospheric organic aerosol, Rapid Communication in Mass Spectrometry, 2012, 26, 793-804. Iinuma Y., Boge O., Grafe R. and Herrmann H.: Methyl-nitrocatechols : Atmospheric tracer coumpounds for biomass burnig secondary organic aerosols, Environmental Science and Technology, 2010, 44, 8453-8459.

Marchand, Nicolas; Sylvestre, Alexandre; Ravier, Sylvain; Detournay, Anais; Bruns, Emily; Temime-Roussel, Brice; Slowik, Jay; El Haddad, Imad; Prevot, Andre

2013-04-01

121

Comparison of analytical methods for HULIS measurements in atmospheric particles  

NASA Astrophysics Data System (ADS)

Humic-Like Substances (HULIS) are a major contributor to the organic carbon in atmospheric aerosol. It would be necessary to standardise an analytical method that could be easily and routinely used for HULIS measurements. We present one of the first comparisons of two of the main methods in use to extract HULIS, using i) a weak anion exchanger (DEAE) and ii) the combination of two separation steps, one according to polarity (on C18) and the second according to acidity (with a strong anion exchanger SAX). The quantification is performed with a DOC analyzer, complemented by an investigation of the chemical structure of the extracted fractions by UV-Visible spectroscopy. The analytical performances of each method are determined and compared for humic substances standards. These methods are further applied to determine the water extractable HULIS (HULISWS) and the 0.1M NaOH alkaline extractable HULIS (HULIST) in atmospheric aerosol collected in an Alpine Valley during winter time. This comparison shows that the simpler DEAE isolation procedure leads to higher recoveries and better reproducibility and should therefore be recommended.

Baduel, C.; Voisin, D.; Jaffrezo, J. L.

2009-03-01

122

Size Distribution of Radon Daughter Particles in Uranium Mine Atmospheres  

Microsoft Academic Search

The size distribution of radon daughters was measured in several uranium mines using four compact diffusion batteries and a round jet cascade impactor. Simultaneously, measurements were made of uncombined fractions of radon daughters, radon concentration, working level and particle concentration. The size distributions found for radon daughters were log normal. The activity median diameters ranged from 0.09?µm to 0.3?µm with

A. C. GEORGE; L. HINCHLIFFE; R. SLADOWSKI

1975-01-01

123

Variation of the mixing state of Saharan dust particles with atmospheric transport  

NASA Astrophysics Data System (ADS)

Mineral dust is an important aerosol species in the Earth's atmosphere and has a major source within North Africa, of which the Sahara forms the major part. Aerosol Time of Flight Mass Spectrometry (ATOFMS) is first used to determine the mixing state of dust particles collected from the land surface in the Saharan region, showing low abundance of species such as nitrate and sulphate internally mixed with the dust mineral matrix. These data are then compared with the ATOFMS single particle mass spectra of Saharan dust particles detected in the marine atmosphere in the vicinity of the Cape Verde islands, which are further compared with those from particles with longer atmospheric residence sampled at a coastal station at Mace Head, Ireland. Saharan dust particles collected near the Cape Verde Islands showed increased internally mixed nitrate but no sulphate, whilst Saharan dust particles collected on the coast of Ireland showed a very high degree of internally mixed secondary species including nitrate, sulphate and methanesulphonate. This uptake of secondary species will change the pH and hygroscopic properties of the aerosol dust and thus can influence the budgets of other reactive gases, as well as influencing the radiative properties of the particles and the availability of metals for dissolution.

Dall'Osto, Manuel; Harrison, Roy M.; Highwood, Eleanor J.; O'Dowd, Colin; Ceburnis, Darius; Querol, Xavier; Achterberg, Eric P.

2010-08-01

124

Etching materials with an atmospheric-pressure plasma jet  

NASA Astrophysics Data System (ADS)

A plasma jet has been developed for etching materials at atmospheric pressure and between 100 and 0963-0252/7/3/005/img10C. Gas mixtures containing helium, oxygen and carbon tetrafluoride were passed between an outer, grounded electrode and a centre electrode, which was driven by 13.56 MHz radio frequency power at 50 to 500 W. At a flow rate of 0963-0252/7/3/005/img11, a stable, arc-free discharge was produced. This discharge extended out through a nozzle at the end of the electrodes, forming a plasma jet. Materials placed 0.5 cm downstream from the nozzle were etched at the following maximum rates: 0963-0252/7/3/005/img12 for Kapton (0963-0252/7/3/005/img13 and He only), 0963-0252/7/3/005/img14 for silicon dioxide, 0963-0252/7/3/005/img15 for tantalum and 0963-0252/7/3/005/img16 for tungsten. Optical emission spectroscopy was used to identify the electronically excited species inside the plasma and outside in the jet effluent.

Jeong, J. Y.; Babayan, S. E.; Tu, V. J.; Park, J.; Henins, I.; Hicks, R. F.; Selwyn, G. S.

1998-08-01

125

Characterizing Biological Particles in the Atmosphere at two Sites in Colorado  

NASA Astrophysics Data System (ADS)

The composition and distribution of primary biological aerosol particles (PBAPs) in the atmosphere is constantly changing due to both natural and anthropogenic activities. In this presentation, we will describe measurements aimed at better characterizing this population at Manitou Experimental Forest, in Pike National Forest in Colorado and in Fort Collins, CO. This work is part of the larger Biosphere-atmosphere Exchange of Aerosols within Cloud, Carbon and Hydrologic cycles, including Organics and Nitrogen (BEACHON) field study program, which is aimed at studying the connections between the biogeochemical cycling of carbon and water in semi-arid regions of the Western U.S. To this end, we are collecting PBAP with SKC impingers into water, which are subsequently analyzed by flow cytometery to determine the atmospheric biological particle concentration. Further, we are generating a gene library of the small subunit RNA genes to speciate the PBAPs in our collected samples using Sanger sequencing. These experiments are performed throughout the year to better understand seasonal variability of atmospheric microbial communities at the selected sites. A small handful of PBAPs have been found to be some of the best ice nucleators in the atmosphere, inducing ice nucleation as high as -2oC; these particles may play pivotal roles in influencing ice formation in cold clouds and, thereby, climate. Preliminary data will be presented aimed at better characterizing this important subset of biological particles.

Garcia, E.; Prenni, A. J.; Prenni, J.; Rivest, J.; Demott, P. J.; Kreidenweis, S. M.

2010-12-01

126

Model simulations of the impact of energetic particle precipitation onto the upper and middle atmosphere  

NASA Astrophysics Data System (ADS)

Solar eruptions and geomagnetic storms can produce fluxes of high-energy protons and elec-trons, so-called Solar Energetic Particle Events, which can enter the Earth's atmosphere espe-cially in polar regions. These particle fluxes primarily cause ionisation and excitation in the upper atmosphere, and thereby the production of HOx and NOx species, which are catalysts for the reduction of ozone. To simulate such particle events, ionisation rates, calculated by the Atmospheric Ionization Module Osnabrück AIMOS (University of Osnabrück), have been implemented into the Bremen 3D Chemistry and Transport Model. To cover altitudes up to the mesopause, the model is driven by meteorological data, provided by the Leibniz-Institute Middle Atmosphere Model LIMA (IAP Kühlungsborn). For several electron and proton events during the highly solar-active period 2003/2004, model calculations have been carried out. To investigate the accordance of modeled to observed changes for atmospheric constituents like NO, NO2 , HNO3 , N2 O5 , ClO, and O3 , results of these calculations will be compared to measurements by the Michelson Interferometer for Passive Atmospheric Sounding MIPAS (ENVISAT) instrument. Computed model results and comparisons with measurements will be presented.

Wieters, Nadine; Sinnhuber, Miriam; Winkler, Holger; Berger, Uwe; Maik Wissing, Jan; Stiller, Gabriele; Funke, Bernd; Notholt, Justus

127

Coulomb stable structures of charged dust particles in a dynamical trap at atmospheric pressure in air  

NASA Astrophysics Data System (ADS)

A mathematical simulation of a dust particle's behavior in the electrodynamic linear quadrupole trap with closing end electrodes allowed us to reveal several features of the phenomena. Regions of stable confinement of a single particle, in dependence of frequency and charge-to-mass ratio, were determined. With an increase of the medium's dynamical viscosity, the region for confining charged particles by the trap becomes wider. We obtained values of the maximum quantities of charged particles confined by the trap at atmospheric pressure in air. Firstly, we presented observations of ordered Coulomb structures of charged dust particles obtained in the quadrupole trap in air at atmospheric pressure. The structures consisted of positively charged oxide aluminum particles 10-15 ?m in size and hollow glass microspheres 30-50 ?m in diameter. The ordered structure could contain particles of different sizes and charges. The trap could confine a limited number of charged particles. The ordered structures of charged micro-particles obtained in the experiments can be used to study Coulomb systems without neutralizing the plasma background and action of ion and electron flows, which are always present in non-homogeneous plasma.

Vasilyak, L. M.; Vladimirov, V. I.; Deputatova, L. V.; Lapitsky, D. S.; Molotkov, V. I.; Pecherkin, V. Ya; Filinov, V. S.; Fortov, V. E.

2013-04-01

128

Investigation of abrasive action of atmospheric particles on the reflectance of mirrors  

SciTech Connect

The effect of atmospheric dust particles on the reflectance of solar-installation mirrors with front and rear reflection is investigated as a function of particle time, speed, dimensions, and angle of attack. It is shown that the atmospheric dust borne in the air and transported by the mountain-valley circulation winds characteristic of Central Asia present no danger to mirrors. Strong winds with driven dust (dust storms) cause damage to the surfaces of mirrors, especially those using front reflection. It is undesirable to locate solar installations in areas with frequent jet winds and loose soil (sand). 9 refs.

Zakhidov, R.A.; Ismanzhanov, A.

1980-01-01

129

Ionization of the Earth's Upper Atmosphere in Large Energetic Particle Events  

NASA Astrophysics Data System (ADS)

Energetic charged particles ionize the upper terrestrial atmosphere. Sofar, chemical consequences of precipitating particles have been discussed for solar protons with energies up to a few hundred MeV. We present a refined model for the interaction of energetic particles with the atmosphere based on a Monte-Carlo simulation. The model includes higher energies and other particle species, such as energetic solar electrons. Results are presented for well-known solar events, such as July 14, 2000, and are extrapolated to extremely large events, such as Carrington's white light flare in 1859, which from ice cores has been identified ass the largest impulsive NO3 event in the interval 1561 -- 1994 (McCracken et al., 2001).

Wolff, E.; Burrows, J.; Kallenrode, M.; von Koenig, M.; Kuenzi, K. F.; Quack, M.

2001-12-01

130

Method and apparatus for making articles from particle based materials  

DOEpatents

A method and apparatus for the production of articles made of a particle-based material; e.g., ceramics and sintered metals. In accordance with the invention, a thermally settable slurry containing a relatively high concentration of the particles is conveyed through an elongate flow area having a desired cross-sectional configuration. The slurry is heated as it is advanced through the flow area causing the slurry to set or harden in a shape which conforms to the cross-sectional configuration of the flow area. The material discharges from the flow area as a self-supporting solid of near net final dimensions. The article may then be sintered to consolidate the particles and provide a high density product.

Moorhead, Arthur J. (Knoxville, TN); Menchhofer, Paul A. (Oak Ridge, TN)

1995-01-01

131

Erosion of aerospace materials by solid-particle impact  

Microsoft Academic Search

The degradation of various aerospace window materials by the action of solid particle impact is investigated. Laboratory simulations of high velocity sand, dust and hail impacts have been carried out, and the damage assessed in terms of the reductions in optical and mechanical performance. A new erosion rig has been designed to cover the broad size and velocity range of

Robert H. Telling; G. H. Jilbert; John E. Field

1997-01-01

132

The measurement of alpha particle emissions from semiconductor memory materials  

Microsoft Academic Search

With the increasing concern for the affects of alpha particles on the reliability of semiconductor memories, an interest has arisen in characterizing semiconductor manufacturing materials for extremely low-level alpha-emitting contaminants. It is shown that four elements are of primary concern: uranium, thorium, radium, and polonium. Measurement of contamination levels are given relevance by first correlating them with alpha flux emission

D. P. Bouldin

1981-01-01

133

Non-silica aerogels as hypervelocity particle capture materials  

NASA Astrophysics Data System (ADS)

The Stardust sample return mission to the comet Wild 2 used silica aerogel as the principal cometary and interstellar particle capture and return medium. However, since both cometary dust and interstellar grains are composed largely of silica, using a silica collector complicates the science that can be accomplished with these particles. The use of non-silica aerogel in future extra-terrestrial particle capture and return missions would expand the scientific value of these missions. Alumina, titania, germania, zirconia, tin oxide, and resorcinol/formaldehyde aerogels were produced and impact tested with 20, 50, and 100?m glass microspheres to determine the suitability of different non-silica aerogels as hypervelocity particle capture mediums. It was found that non-silica aerogels do perform as efficient hypervelocity capture mediums, with alumina, zirconia, and resorcinol/formaldehyde aerogels proving to be the best of the materials tested.

Jones, Steven M.

2010-01-01

134

Particle-Induced X-Ray Emission Analysis of Atmospheric Aerosols  

Microsoft Academic Search

We are developing a research program in ion-beam analysis (IBA) of atmospheric aerosols at the Union College Ion-Beam Analysis Laboratory to study the transport, transformation, and effects of airborne pollution in Upstate New York. The simultaneous applications of the IBA techniques of particle-induced X-ray emission (PIXE), Rutherford back-scattering spectrometry (RBS), particle-induced gamma-ray emission (PIGE), and proton elastic scattering analysis (PESA)

Colin Gleason; Charles Harrington; Katie Schuff; Maria Battaglia; Robert Moore; Colin Turley; Michael Vineyard; Scott Labrake

2010-01-01

135

Concentration profiles of particles settling in the neutral and stratified atmospheric boundary layer  

Microsoft Academic Search

An expression for the vertical equilibrium concentration profile of heavy particles, including the effects of canopy on the\\u000a eddy diffusivity as well as corrections for atmospheric stability, is proposed. This expression is validated against measurements\\u000a of vertical concentration profiles of corn pollen above a corn field. The fitted theoretical profiles show that particle settling\\u000a is correctly accounted for. The sensitivity

Marcelo Chamecki; René van Hout; Charles Meneveau; Marc B. Parlange

2007-01-01

136

Characterization of individual atmospheric aerosol particles with SIMS and laser-SNMS  

Microsoft Academic Search

The surface chemistry of atmospheric aerosol particles is important in determining how these particles will effect human health, visibility, climate and precipitation chemistry. In previous work, it has been shown that ToF-SIMS can provide significant valuable information on both organic and inorganic constituents of the aerosol. It has been found, however, that ToF-SIMS with a Ga+ primary ion beam offers

R. E. Peterson; A. Nair; S. Dambach; H. F. Arlinghaus; B. J. Tyler

2006-01-01

137

Nuclear microprobe analysis and source apportionment of individual atmospheric aerosol particles  

NASA Astrophysics Data System (ADS)

In atmospheric aerosol research, one key issue is to determine the sources of the airborne particles. Bulk PIXE analysis coupled with receptor modeling provides a useful, but limited view of the aerosol sources influencing one particular site or sample. The scanning nuclear microprobe (SNM) technique is a microanalytical technique that gives unique information on individual aerosol particles. In the SNM analyses a 1.0 ?m size 2.4 MeV proton beam from the Oxford SNM was used. The trace elements with Z > 11 were measured by the particle induced X-ray emission (PIXE) method with detection limits in the 1-10 ppm range. Carbon, nitrogen and oxygen are measured simultaneously using Rutherford backscattering spectrometry (RBS). Atmospheric aerosol particles were collected at the Brazilian Antarctic Station and at biomass burning sites in the Amazon basin tropical rain forest in Brazil. In the Antarctic samples, the sea-salt aerosol particles were clearly predominating, with NaCl and CaSO4 as major compounds with several trace elements as Al, Si, P, K, Mn, Fe, Ni, Cu, Zn, Br, Sr, and Pb. Factor analysis of the elemental data showed the presence of four components: 1) soil dust particles; 2) NaCl particles; 3) CaSO4 with Sr; and 4) Br and Mg. Strontium, observed at 20-100 ppm levels, was always present in the CaSO4 particles. The hierarchical cluster procedure gave results similar to the ones obtained through factor analysis. For the tropical rain forest biomass burning aerosol emissions, biogenic particles with a high organic content dominate the particle population, while K, P, Ca, Mg, Zn, and Si are the dominant elements. Zinc at 10-200 ppm is present in biogenic particles rich in P and K. The quantitative aspects and excellent detection limits make SNM analysis of individual aerosol particles a very powerful analytical tool.

Artaxo, Paulo; Rabello, Marta L. C.; Watt, Frank; Grime, Geoff; Swietlicki, Erik

1993-04-01

138

Field-responsive smart composite particle suspension: materials and rheology  

NASA Astrophysics Data System (ADS)

Both electrorheological (ER) and magnetorheological (MR) fluids are known to be smart materials which can be rapidly and reversibly transformed from a fluid-like to a solid-like state within milliseconds by showing dramatic and tunable changes in their rheological properties under external electrical or magnetic field strength, respectively. Here, among various smart composite particles studied, recently developed core-shell structured polystyrene/graphene oxide composite based ER material as well as the dual-step functionally coated carbonyl iron composite based MR material are briefly reviewed along with their rheological characteristics under external fields.

Zhang, Wen Ling; Liu, Ying Dan; Choi, Hyoung Jin

2012-09-01

139

Particle-solid interactions and 21st century materials science  

NASA Astrophysics Data System (ADS)

The basic physics that governs the interaction of energetic ion beams with solids has its roots in the atomic and nuclear physics of the last century. The central formalism of Jens Lindhard, describing the ``particle-solid interaction'', provides a valuable quantitative guide to statistically meaningful quantities such as energy loss, ranges, range straggling, channeling effects, sputtering coefficients, and damage intensity and profiles. Modern materials modification (nanoscience, solid state dynamics) requires atomic scale control of the particle-solid interaction. Two recent experimental examples are discussed: (1) the control of the size distribution of nanocrystals formed in implanted materials and (2) the investigation of the site-specific implantation of hydrogen into silicon. Both cases illustrate unique solid-state configurations, created by ion implantation, that address issues of current materials science interest.

Feldman, L. C.; Lu?Pke, G.; Tolk, N. H.; Lopez, R.; Haglund, R. F.; Haynes, T. E.; Boatner, L. A.

2003-12-01

140

Atmospheric non-spherical particles optical properties from UV-polarization lidar and scattering matrix  

NASA Astrophysics Data System (ADS)

In this contribution, the optical backscattering properties of atmospheric non-spherical particles are analyzed after long-range transport with a highly sensitive and accurate UV-polarization lidar. Far from the source region, the aerosol cloud is considered as a mixture of spherical (s) and non-spherical (ns) particles. Aerosols UV-depolarization serves as an independent means to discriminate ns from s-atmospheric particles. Vertical profiles of aerosols backscattering coefficient ?a and UV-depolarization ratio ?a are provided for two ns-particles case studies, on volcanic ash and desert dust, in the troposphere of Lyon (45.76°N, 4.83°E, France). Achieved polarization-sensitivity and accuracy allows tracing different atmospheric layers with a 75 m-altitude resolution. The depolarization ratio ?a of the mixed (a) = {s, ns} aerosol cloud is then analyzed in the frame of the scattering matrix formalism. Observed ?a-values, which range from a few to 38.5% (19.5%) for volcanic ash (desert dust) particles, only equal the intrinsic depolarization ratio of ns-particles when there is no detectable s-particle, and in the presence of s-particles, ?a is always below ?a,ns. By coupling our accurate lidar measurements with scattering matrix, we retrieved vertical profiles of backscattering coefficient, specific to ash (dust) particles, which is new. This ash (dust) specificity is then discussed within our error bars. We hence developed a methodology giving access to the number concentration vertical profile of specific particulate matter in the troposphere.

Miffre, Alain; David, Grégory; Thomas, Benjamin; Rairoux, Patrick

2011-08-01

141

Atmospheric data over a solar cycle: no connection between galactic cosmic rays and new particle formation  

NASA Astrophysics Data System (ADS)

Aerosol particles affect the Earth's radiative balance by directly scattering and absorbing solar radiation and, indirectly, through their activation into cloud droplets. Both effects are known with considerable uncertainty only, and translate into even bigger uncertainties in future climate predictions. More than a decade ago, variations in galactic cosmic rays were suggested to closely correlate with variations in atmospheric cloud cover and therefore constitute a driving force behind aerosol-cloud-climate interactions. Later, the enhancement of atmospheric aerosol particle formation by ions generated from cosmic rays was proposed as a physical mechanism explaining this correlation. Here, we report unique observations on atmospheric aerosol formation based on measurements at the SMEAR II station, Finland, over a solar cycle (years 1996-2008) that shed new light on these presumed relationships. Our analysis shows that none of the quantities related to aerosol formation correlates with the cosmic ray-induced ionisation intensity (CRII). We also examined the contribution of ions to new particle formation on the basis of novel ground-based and airborne observations. A consistent result is that ion-induced formation contributes typically significantly less than 10% to the number of new particles, which would explain the missing correlation between CRII and aerosol formation. Our main conclusion is that galactic cosmic rays appear to play a minor role for atmospheric aerosol formation events, and so for the connected aerosol-climate effects as well.

Kulmala, M.; Riipinen, I.; Nieminen, T.; Hulkkonen, M.; Sogacheva, L.; Manninen, H. E.; Paasonen, P.; Petäjä, T.; Dal Maso, M.; Aalto, P. P.; Viljanen, A.; Usoskin, I.; Vainio, R.; Mirme, S.; Mirme, A.; Minikin, A.; Petzold, A.; Hõrrak, U.; Plaß-Dülmer, C.; Birmili, W.; Kerminen, V.-M.

2010-02-01

142

Atmospheric data over a solar cycle: no connection between galactic cosmic rays and new particle formation  

NASA Astrophysics Data System (ADS)

Aerosol particles affect the Earth's radiative balance by directly scattering and absorbing solar radiation and, indirectly, through their activation into cloud droplets. Both effects are known with considerable uncertainty only, and translate into even bigger uncertainties in future climate predictions. More than a decade ago, variations in galactic cosmic rays were suggested to closely correlate with variations in atmospheric cloud cover and therefore constitute a driving force behind aerosol-cloud-climate interactions. Later, the enhancement of atmospheric aerosol particle formation by ions generated from cosmic rays was proposed as a physical mechanism explaining this correlation. Here, we report unique observations on atmospheric aerosol formation based on measurements at the SMEAR II station, Finland, over a solar cycle (years 1996-2008) that shed new light on these presumed relationships. Our analysis shows that none of the quantities related to aerosol formation correlates with the cosmic ray-induced ionisation intensity (CRII). We also examined the contribution of ions to new particle formation on the basis of novel ground-based and airborne observations. A consistent result is that ion-induced formation contributes typically less than 10% to the number of new particles, which would explain the missing correlation between CRII and aerosol formation. Our main conclusion is that galactic cosmic rays appear to play a minor role for atmospheric aerosol formation, and so for the connected aerosol-climate effects as well.

Kulmala, M.; Riipinen, I.; Nieminen, T.; Hulkkonen, M.; Sogacheva, L.; Manninen, H. E.; Paasonen, P.; Petäjä, T.; Dal Maso, M.; Aalto, P. P.; Viljanen, A.; Usoskin, I.; Vainio, R.; Mirme, S.; Mirme, A.; Minikin, A.; Petzold, A.; Hõrrak, U.; Plaß-Dülmer, C.; Birmili, W.; Kerminen, V.-M.

2009-10-01

143

Counterion atmosphere and hydration patterns near a nucleosome core particle.  

PubMed

The chromatin folding problem is an exciting and rich field for modern research. On the most basic level, chromatin fiber consists of a collection of protein-nucleic acid complexes, known as nucleosomes, joined together by segments of linker DNA. Understanding how the cell successfully compacts meters of highly charged DNA into a micrometer size nucleus while still enabling rapid access to the genetic code for transcriptional processes is a challenging goal. In this work we shed light on the way mobile ions condense around the nucleosome core particle, as revealed by an extensive all-atom molecular dynamics simulation. On a hundred nanosecond time scale, the nucleosome exhibited only small conformational fluctuations. We found that nucleosomal DNA is better neutralized by the combination of histone charges and mobile ions compared with free DNA. We provide a detailed physical explanation of this effect using ideas from electrostatics in continuous media. We also discovered that sodium condensation around the histone core is dominated by an experimentally characterized acidic patch, which is thought to play a significant role in chromatin compaction by binding with basic histone tails. Finally, we found that the nucleosome is extensively permeated by over a thousand water molecules, which in turn allows mobile ions to penetrate deeply into the complex. Overall, our work sheds light on the way ionic and hydration interactions within a nucleosome may affect internucleosomal interactions in higher order chromatin fibers. PMID:19778017

Materese, Christopher K; Savelyev, Alexey; Papoian, Garegin A

2009-10-21

144

Large-eddy simulation of particle-laden atmospheric boundary layer  

NASA Astrophysics Data System (ADS)

Pollen dispersion in the atmospheric boundary layer (ABL) is numerically investigated using a hybrid large-eddy simulation (LES) Lagrangian approach. Interest in prediction of pollen dispersion stems from two reasons, the allergens in the pollen grains and increasing genetic manipulation of plants leading to the problem of cross pollination. An efficient Eulerian-Lagrangian particle dispersion algorithm for the prediction of pollen dispersion in the atmospheric boundary layer is outlined. The volume fraction of the dispersed phase is assumed to be small enough such that particle-particle collisions are negligible and properties of the carrier flow are not modified. Only the effect of turbulence on particle motion has to be taken into account (one-way coupling). Hence the continuous phase can be treated separate from the particulate phase. The continuous phase is determined by LES in the Eulerian frame of reference whereas the dispersed phase is simulated in a Lagrangian frame of reference. Numerical investigations are conducted for the convective, neutral and stable boundary layer as well different topographies. The results of the present study indicate that particles with small diameter size follow the flow streamlines, behaving as tracers, while particles with large diameter size tend to follow trajectories which are independent of the flow streamlines. Particles of ellipsoidal shape travel faster than the ones of spherical shape.

Ilie, Marcel; Smith, Stefan Llewellyn

2008-11-01

145

The effect of precipitating particles on middle atmospheric night time ozone during enhanced geomagnetic activity  

NASA Astrophysics Data System (ADS)

We have investigated the effect of precipitating particles on middle atmospheric ozone during a moderate geomagnetic storm in July 2009. It is expected that the number of precipitating particles increases with increasing geomagnetic activity, and that these precipitated particles will subsequently enhance the production of nitrosonium (NO+) and odd hydrogen (HOx) in the upper atmosphere. The lifetime of HOx and its associated ozone (O3) destruction is short, whilst NO+ can form long-lived odd nitrogen during times of high geomagnetic activity, (NOx), which can affect ozone over a longer time span, and hence a wider spatial range due to transport. We use the National Oceanic and Atmospheric Administration (NOAA) satellite data to identify and analyze the particles that precipitated over Antarctica during the moderate geomagnetic storm. To analyze the subsequent nitric oxide (NO) enhancement and O3 depletion we use a microwave radiometer stationed at Troll, Antarctica (72°S, 2.5°E, L=4.76). This microwave radiometer operating at 250 GHz gives high temporal and vertical resolution of the NO and O3 column. The Atmospheric Radiation Transfer Simulator (ARTS) and QPack have been employed to perform the inversions of the spectra. During the July storm that reached -79 nT on the Dst index, we observe radiation-belt particle precipitation over Troll, an NO increase, and a direct O3 depletion of 30% between 60 and 80 km altitude. This O3 depletion lasted for 9 days, and its centroid descended to 55 km altitude at a vertical velocity of 1-3 m/s. This work shows that moderate storms, which are common-place and occur even during solar minimum, can cause a significant and direct effect in the middle atmospheric ozone distribution.

Daae, M.; Espy, P. J.; Newnham, D.; Kleinknecht, N.; Clilverd, M.

2010-12-01

146

Investigations of the variability of dust particle sizes in the martian atmosphere using the NASA Ames General Circulation Model  

Microsoft Academic Search

We present a Mars General Circulation Model (GCM) numerical investigation of the physical processes (i.e., wind stress and dust devil dust lifting and atmospheric transport) responsible for temporal and spatial variability of suspended dust particle sizes. Measurements of spatial and temporal variations in airborne dust particles sizes in the martian atmosphere have been derived from Mars Global Surveyor (MGS) Thermal

Melinda A. Kahre; Jeffery L. Hollingsworth; Robert M. Haberle; James R. Murphy

2008-01-01

147

Three-dimensional simulations of the atmospheric cycle of desert dust particles using a general circulation model  

Microsoft Academic Search

A modeling of the atmospheric cycle of desert dust particles has been introduced within an atmospheric general circulation model. This approach, which allows a modeling of the full cycle of dust particles, should help to investigate the link between desert dust and climate and, in particular, to study how the dust transport can be affected by climatic changes (for example,

Sylvie Joussaume

1990-01-01

148

Material dependence of the wire-particle Casimir interaction  

NASA Astrophysics Data System (ADS)

We study the Casimir interaction between a metallic cylindrical wire and a metallic spherical particle by employing the scattering formalism. At large separations, we derive the asymptotic form of the interaction. In addition, we find the interaction between a metallic wire and an isotropic atom, both in the nonretarded and retarded limits. We identify the conditions under which the asymptotic Casimir interaction does not depend on the material properties of the metallic wire and the particle. Moreover, we compute the exact Casimir interaction between the particle and the wire numerically. We show that there is a complete agreement between the numerics and the asymptotic energies at large separations. For short separations, our numerical results show good agreement with the proximity force approximation.

Noruzifar, E.; Rodriguez-Lopez, P.; Emig, T.; Zandi, R.

2013-04-01

149

The Role of Organics in Atmospheric New Particle Formation and Growth  

NASA Astrophysics Data System (ADS)

Atmospheric aerosols impair visibility and human health, interfere with radiative transfer, and alter cloud formation. The major contributors include sulfate and organic aerosols from anthropogenic and biogenic activities, which are produced through a multitude of complex multiphase atmospheric processes by photochemical oxidation of emitted sulfur dioxide and volatile organic compounds (VOCs) into less volatile forms and gas-to-particle conversion. Aerosol nucleation events have been frequently observed under various tropospheric conditions and account for a major fraction of the total aerosol population, but the fundamental chemical processes responsible for aerosol nucleation and growth remain poorly understood. New particle formation occurs in two distinct stages, nucleation to form thermodynamically stable clusters and subsequent growth of the newly nucleated clusters by condensation or heterogeneous reactions to detectable particles that competes with capture and removal by coagulation with pre-existing particles. Sulfuric acid has been identified as a key species in new particle formation, but it is commonly recognized that binary nucleation of water and sulfuric acid is not efficient enough to explain measured nucleation events. Considerable uncertainty exists regarding the identity of other condensable species responsible for nucleation and growth of new particles. Currently available results of aerosol nucleation and growth from experimental, theoretical, and field studies are rather conflicting, hindering efforts to model formation and growth of secondary aerosols on the regional and global scales and to assess their atmospheric impacts. This talk will summarize recent progress in the understanding of the contributions of organics to atmospheric aerosol nucleation and growth. New experimental and theoretical results on this subject will be presented.

Zhang, R.; Zhang, J.; Khalizov, A. F.

2007-12-01

150

Novel applications of atmospheric pressure plasma on textile materials  

NASA Astrophysics Data System (ADS)

Various applications of atmospheric pressure plasma are investigated in conjunction with polymeric materials including paper, polypropylene non-woven fabric, and cotton. The effect of plasma on bulk and surface properties is examined by treating both cellulosic pulp and prefabricated paper with various plasma-gas compositions. After treatment, pulp is processed into paper and the properties are compared. The method of pulp preparation is found to be more significant than the plasma, but differences in density, strength, and surface roughness are apparent for the pulp vs. paper plasma treatments. The plasma is also used to remove sizes of PVA and starch from poly/cotton and cotton fabric respectively. In both cases plasma successfully removes a significant amount of size, but complete size removal is not achieved. Subsequent washes (PVA) or scouring (cotton) to remove the size are less successful than a control, suggesting the plasma is crosslinking the size that is not etched away. However, at short durations in cold water using an oxygen plasma, slightly more PVA is removed than with a control. For the starch sized samples, plasma and scouring are never as successful at removing starch as a conventional enzyme, but plasma improves dyeability without need for scouring. Plasma is also used to graft chemicals to the surface of polypropylene and cotton fabric. HTCC, an antimicrobial is grafted to polypropylene with successful grafting indicated by x-ray photoemission spectroscopy (XPS), dye tests, and Fourier transform infrared spectroscopy (FTIR). Antimicrobial activity of the grafted samples is also characterized. 3ATAC, a vinyl monomer is also grafted to polypropylene and to cotton. Additives including Mohr's salt, potassium persulfate, and diacrylate are assessed to increase yield. Successful grafting of 3ATAC is confirmed by XPS and dye testing. A combination of all three additives is identified as optimum for maximizing graft yield.

Cornelius, Carrie Elizabeth

151

BIOCOMPATIBLE FLUORESCENT MICROSPHERES: SAFE PARTICLES FOR MATERIAL PENETRATION STUDIES  

SciTech Connect

Biocompatible polymers with hydrolyzable chemical bonds have been used to produce safe, non-toxic fluorescent microspheres for material penetration studies. The selection of polymeric materials depends on both biocompatibility and processability, with tailored fluorescent properties depending on specific applications. Microspheres are composed of USFDA-approved biodegradable polymers and non-toxic fluorophores and are therefore suitable for tests where human exposure is possible. Micropheres were produced which contain unique fluorophores to enable discrimination from background aerosol particles. Characteristics that affect dispersion and adhesion can be modified depending on use. Several different microsphere preparation methods are possible, including the use of a vibrating orifice aerosol generator (VOAG), a Sono-Tek atomizer, an emulsion technique, and inkjet printhead. Applications for the fluorescent microspheres include challenges for biodefense system testing, calibrants for biofluorescence sensors, and particles for air dispersion model validation studies.

Farquar, G; Leif, R

2009-07-15

152

Atmospherically stable nanoscale zero-valent iron particles formed under controlled air contact: characteristics and reactivity.  

PubMed

Atmospherically stable NZVI (nanoscale zero-valent iron) particles were produced by modifying shell layers of Fe(H2) NZVI particles (RNIP-10DS) by using a controlled air contact method. Shell-modified NZVI particles were resistant to rapid aerial oxidation and were shown to have TCE degradation rate constants that were equivalent to 78% of those of pristine NZVI particles. Fe(H2) NZVI particles that were vigorously contacted with air (rapidly oxidized) showed a substantially compromised reactivity. Aging of shell-modified particles in water for one day resulted in a rate increase of 54%, implying that depassivation of the shell would play an important role in enhancing reactivity. Aging of shell-modified particles in air led to rate decreases by 14% and 46% in cases of one week and two months of aging, respectively. A series of instrumental analyses using transmission electron microscopy, X-ray diffractography, X-ray photoelectron spectroscopy, and X-ray absorption near-edge structure showed that the shells of modified NZVI particles primarily consisted of magnetite (Fe(3)O(4)). Analyses also implied that the new magnetite layer produced during shell modification was protective against shell passivation. Aging of shell-modified particles in water yielded another major mineral phase, goethite (alpha-FeOOH), whereas aging in air produced additional shell phases such as wustite (FeO), hematite (alpha-Fe(2)O(3)), and maghemite (gamma-Fe(2)O(3)). PMID:20136088

Kim, Hong-Seok; Ahn, Jun-Young; Hwang, Kyung-Yup; Kim, Il-Kyu; Hwang, Inseong

2010-03-01

153

The measurement of alpha particle emissions from semiconductor memory materials  

Microsoft Academic Search

With the increasing concern for the affects of alpha particles on the reliability of semiconductor memories, an interest has\\u000a arisen in characterizing semiconductor manufacturing materials for extremely low-level alpha-emitting contaminants. It is\\u000a shown that four elements are of primary concern: uranium, thorium, radium, and polonium. Measurement of contamination levels\\u000a are given relevance by first correlating them with alpha flux emission

D. P. Bouldin

1981-01-01

154

Field and laboratory studies of atmospheric reactive mercury: Gas-particle partitioning and sources  

NASA Astrophysics Data System (ADS)

Certain aspects of atmospheric reactive mercury (RM) source-receptor relationships are not well understood. The objective of this dissertation was to improve the understanding of these relationships in the following areas: (i) gas-particle partitioning, and; (ii) the local impacts of RM source emissions. A novel aerosol reactor was developed to study gas-particle partitioning of RM using synthetic atmospheric aerosol containing picogram concentrations of RM. The RM in the aerosol was collected in an offline mode with filters and sorbent, and analyzed with Thermal Desorption Analysis (TDA). The offline-TDA collection and analysis method was compared with a commercial real time ambient mercury analyzer and two wet analysis methods using ambient measurements. The offline-TDA method performed well in comparison to the established techniques. The dependencies of gas-particle partitioning coefficients upon temperature and particle composition were determined and parameterized from field studies and laboratory experiments. The volatility of RM increased with ambient temperature in urban aerosol and laboratory aerosol of ammonium sulfate and adipic acid. The dependence of RM gas-particle partitioning on particle composition were determined using synthetic atmospheric aerosol generated in the laboratory. RM partitioned predominantly to the particle phase in particles of sodium nitrate, sodium chloride and potassium chloride, but was much more volatile in particles made of ammonium sulfate, levoglucosan and adipic acid. The impacts of RM sources on local receptors were studied in southern Wisconsin and Mexico City. RM measurements were made over a year in Milwaukee, WI (urban) and Devil's Lake State Park, WI (rural). An urban excess of all three mercury species was detected in Milwaukee, WI. The urban excess was attributed to a higher density of mercury emissions in the Milwaukee, WI-Chicago, IL area. The impact of local sources of RM on both sites was found to dominate the atmospheric concentrations. PHg and RGM measurements were made in Mexico City over 2.5 weeks. Diurnal concentration variations with nocturnal maxima pointed to nightly transport of air into the city from the industrial area to the north. RM partitioned predominantly to the particle phase in most of the plumes.

Rutter, Andrew Philip

155

Soil-derived sulfate in atmospheric dust particles at Taklimakan desert  

NASA Astrophysics Data System (ADS)

Dust-associated sulfate is believed to be a key species which can alter the physical and chemical properties of dust particles in the atmosphere. Its occurrence in the particles has usually been considered to be the consequence of particles' aging in the air although it is present in some crustal minerals. Our observation at the north and south edge of Taklimakan desert, one of the largest dust sources in the Northern Hemisphere, during a dust episode in April 2008 revealed that sulfate in atmospheric dust samples most likely originated directly from surface soil. Its TSP, PM10 and PM2.5 content was proportional to samples' mass and comprised steadily about 4% in the differently sized samples, the ratio of elemental sulfur to iron was approximately constant 0.3, and no demonstrable influence of pollutants from fossil fuel combustion and biomass burning was detected. These results suggest that sulfate could be substantially derived from surface soil at the desert area and the lack of awareness of this origin may impede accurate results in any investigation of atmospheric sulfur chemistry associated with Taklimakan dust and its subsequent local, regional and global effects on the atmosphere.

Wu, Feng; Zhang, Daizhou; Cao, Junji; Xu, Hongmei; An, Zhisheng

2012-12-01

156

Harnessing Particle Modulation in an Electrodynamic Balance to Measure Optical Properties of Atmospheric Aerosols  

NASA Astrophysics Data System (ADS)

Aerosols play a key but complex role in the global energy budget. Observations of aerosols with high organic and carbonaceous content over large areas in the Indian Ocean signify the role of aerosols in our coupled climate system (1) and underscore the need to quantify their optical properties. To help achieve this, we have constructed an electrodynamic balance where isolated aerosols are levitated and investigated without any contamination by wall effects. The mass of the particle is measured by the DC electric field necessary to balance the gravitational force. Light scattering and Mie theory allow a precise determination of particle size and refractive index. We are also developing a novel technology that exploits particle modulation and lock in detection to measure optical absorption by a single aerosol particle. Both photo-acoustic and Raman spectroscopy are being used for this. We plan to present results on salt, carbonaceous, and mixed particles to demonstrate the feasibility of our approach. Models to calculate absorption by complex atmospheric particles will also be examined. (1) Ramanathan V, Crutzen PJ, Kiehl JT, Rosenfeld D, Atmosphere : Aerosols, climate, and the hydrological cycle, Science, 294, 2119-2124, 2001

Schmidt, C. C.; Dubey, M. K.; Stephens, J. R.

2002-05-01

157

Elemental and individual particle analysis of atmospheric aerosols from high Himalayas.  

PubMed

Atmospheric aerosols were collected during the scientific expedition to Mt. Qomolangma (Everest) in May-June, 2005. The elemental concentrations of the aerosols were determined by inductively coupled plasma mass spectrometry. This yielded data for the concentration of 14 elements: Na, Mg, Al, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, and Pb. The mean elemental concentrations were generally comparable with those from central Asia and the Arctic, while much higher than those from Antarctic. Size, morphology, and chemical composition of 900 individual aerosol particles were determined by scanning electron microscopy and energy-dispersive X-ray microanalysis. Based on morphology and elemental composition, the particles were clustered into eight groups: soot (8%), tar ball (3%), alumosilicates/silica (55%), calcium sulfate (16%), Ca/Mg carbonate (2%), Fe/Ti-rich particles (3%), Pb-rich particles (1%), and biological particles (12%). The sampling site, located at 6,520 m in the Himalayas, is particularly remote and located at high altitude. Nonetheless, high aerosol enrichment factors for copper, chromium, lead, nickel, vanadium, and zinc all suggest the influence of long-range transported pollution, while enrichment in calcium and the presence of alumino-silicates in individual particle analyses indicates a distinct mineral dust influence. The backward air mass trajectories showed that the northwestern part of India may contribute to the atmospheric aerosol in the central high Himalayas. PMID:19083111

Cong, Zhiyuan; Kang, Shichang; Dong, Shuping; Liu, Xiande; Qin, Dahe

2010-01-01

158

Polynuclear aromatic hydrocarbon degradation by heterogeneous reactions with N 2O 5 on atmospheric particles  

NASA Astrophysics Data System (ADS)

The degradation of particulate polynuclear aromatic hydrocarbons (PAH) on atmospheric soot particles in the presence of gas phase dinitrogen pentoxide (N 2O 5) was explored. Dilute diesel and wood soot particles containing PAH were reacted with˜10ppm of N 2O 5 in a 200 ? continuous stirred tank reactor (CSTR). To provide a stable source of particles for reaction in the CSTR, diesel or wood soot particles were injected at night into a 25 m 3 Teflon outdoor chamber. The large chamber served as a reservoir for the feed aerosol, and the aerosol could then be introduced at a constant flow rate into the CSTR. PAH-N 2O 5 heterogeneous rate constants for wood soot at 15°C ranged from2 × 10 -18to5 × 10 -18 cm 3 molecules -1 s -1. For diesel soot the rate constants at 16°C were higher and ranged from5 × 10 -18to30 × 10 -18 cm 3 molecules -1 s -1. Comparisons with other studies suggest that sunlight is the most important factor which influences PAH decay. This is followed by ozone, NO 2, N 2O 5 and nitric acid. The rate constants of nitro-PAH formation from a parent PAH and N 2O 5 were of the order of1 × 10 -19-1 × 10 -18 molecules -1s -1. The uncertainty associated with all of these rate constants is± a factor of 3. Given, however, the small magnitude of the rate constants and the low levels of N 2O 5 present in the atmosphere, we concluded that PAH heterogeneous reactions with gas phase N 2O 5 degrade particle-bound PAH or to form nitro-PAH from PAH are not very important. (Direct application of the specific rate constants derived in this study to ambient atmospheres should not be undertaken unless the ambient particle size distributions and chemical composition of the particles are similar to the ones reported in this study.)

Kamens, Richard M.; Guo, Jiazhen; Guo, Zhishi; McDow, Stephen R.

159

A review of measurement and modelling results of particle atmosphere-surface exchange  

NASA Astrophysics Data System (ADS)

Atmosphere-surface exchange represents one mechanism by which atmospheric particle mass and number size distributions are modified. Deposition velocities (vd) exhibit a pronounced dependence on surface type, due in part to turbulence structure (as manifest in friction velocity), with minima of approximately 0.01 and 0.2 cm s-1 over grasslands and 0.1-1 cm s-1 over forests. However, as noted over 20 yr ago, observations over forests generally do not support the pronounced minimum of deposition velocity (vd) for particle diameters of 0.1-2 ?m as manifest in theoretical predictions. Closer agreement between models and observations is found over less-rough surfaces though those data also imply substantially higher surface collection efficiencies than were originally proposed and are manifest in current models. We review theorized dependencies for particle fluxes, describe and critique model approaches and innovations in experimental approaches, and synthesize common conclusions of experimental and modelling studies. We end by proposing a number of research avenues that should be pursued in to facilitate further insights and development of improved numerical models of atmospheric particles.

Pryor, S. C.; Gallagher, M.; Sievering, H.; Larsen, S. E.; Barthelmie, R. J.; Birsan, F.; Nemitz, E.; Rinne, J.; Kulmala, M.; Grönholm, T.; Taipale, R.; Vesala, T.

2008-02-01

160

Mass-particle size distributions of atmospheric dust and the dry deposition of dust to the remote ocean  

NASA Astrophysics Data System (ADS)

Size-separated mineral aerosol samples were collected and analyzed to investigate the relationships between the mass-particle size distributions (MSDs) of dust particles and the dust loadings in the atmosphere. The data also were used to assess the changes in the MSDs of dust in relation to transport processes and especially the associated effects on dry deposition. Atmospheric dust concentrations, as indicated by aluminum or scandium, in samples collected from three sites in the remote North Atlantic were higher than those in samples collected during a cruise in the North Pacific on board the R/V Moana Wave. However, the mass median diameters (MMDs) for the North Pacific samples were both larger on average (˜3 ?m versus ˜2 ?m aerodynamic equivalent diameter) and more variable than those from the North Atlantic; this difference was attributed to wet conditions and particle aggregation over the North Pacific. In addition, for the ensemble of all samples the geometric standard deviations of the mass-particle size distributions, which are analogous to the sorting values used to characterize sedimentary materials, tended to vary inversely and nonlinearly with the mass median diameters. Model-derived dry deposition velocities for the samples were at most weakly related to either the dust concentrations or the MMDs. However, the dry deposition velocities for two subsets of samples were correlated with the geometric standard deviations of the distributions; this is further evidence that the mass flux of dust via dry deposition can be controlled by a relatively small fraction of aerodynamically large particles.

Arimoto, R.; Ray, B. J.; Lewis, N. F.; Tomza, U.; Duce, R. A.

1997-07-01

161

The error in satellite retrieved temperature profiles due to the effects of atmospheric aerosol particles  

SciTech Connect

Radiances were computed for the eight temperature-sounding IR channels of the SIR-B (Satellite Infrared Spectrometer) instrument for a clear model and two very hazy models of the atmosphere. Temperature profiles were retrieved from these radiances, using minimum information technique. Deviations of the retrieved profile from the true one occurred only for haze models, and were due only to the neglect of aerosol-particle absorption and scattering in the retrieval process. Since the atmosphere is typically much less hazy than these models represent, it is concluded that the error caused by neglect of aerosol effects is a small part of the rms error computed from radiosonde intercomparison analyses.

Stowe, L.L.; Fleming, H.E.

1980-01-01

162

29 CFR 1917.23 - Hazardous atmospheres and substances (see also § 1917.2 Hazardous cargo, material, substance or...  

Code of Federal Regulations, 2010 CFR

... 2010-07-01 false Hazardous atmospheres and substances (see also ç 1917.2 Hazardous cargo, material, substance or atmosphere). 1917.23 Section 1917.23...Operations § 1917.23 Hazardous atmospheres and substances (see also §...

2010-07-01

163

29 CFR 1917.23 - Hazardous atmospheres and substances (see also § 1917.2 Hazardous cargo, material, substance or...  

Code of Federal Regulations, 2013 CFR

... 2013-07-01 false Hazardous atmospheres and substances (see also ç 1917.2 Hazardous cargo, material, substance or atmosphere). 1917.23 Section 1917.23...Operations § 1917.23 Hazardous atmospheres and substances (see also §...

2013-07-01

164

29 CFR 1917.23 - Hazardous atmospheres and substances (see also § 1917.2 Hazardous cargo, material, substance or...  

Code of Federal Regulations, 2010 CFR

... 2009-07-01 false Hazardous atmospheres and substances (see also ç 1917.2 Hazardous cargo, material, substance or atmosphere). 1917.23 Section 1917.23...Operations § 1917.23 Hazardous atmospheres and substances (see also §...

2009-07-01

165

Effect on surface roughness of zerodur material in atmospheric pressure plasma jet processing  

Microsoft Academic Search

Zerodur material is considered as the ideal material in the high performance optic systems because of its excellent thermal stability characteristics. This paper deals with the impacting factors on the zerodur material surface roughness during atmospheric pressure plasma jet(APPJ) processing. At first, based on multiphase and multi-component in zerodur material, the effect on the zerodur surface chemical components and surface

H. L. Jin; B. Wang; F. H. Zhang

2010-01-01

166

Reactive Atmospheric Plasma Spraying of AlN Coatings: Influence of Aluminum Feedstock Particle Size  

NASA Astrophysics Data System (ADS)

Feedstock powder characteristics (size distribution, morphology, shape, specific mass, and injection rate) are considered to be one of the key factors in controlling plasma-sprayed coatings microstructure and properties. The influence of feedstock powder characteristics to control the reaction and coatings microstructure in reactive plasma spraying process (RPS) is still unclear. This study, investigated the influence of feedstock particle size in RPS of aluminum nitride (AlN) coatings, through plasma nitriding of aluminum (Al) feedstock powders. It was possible to fabricate AlN-based coatings through plasma nitriding of all kinds of Al powders in atmospheric plasma spray (APS) process. The nitriding ratio was improved with decreasing the particle size of feedstock powder, due to improving the nitriding reaction during flight. However, decreasing the particle size of feedstock powder suppressed the coatings thickness. Due to the loss of the powder during the injection, the excessive vaporization of fine Al particles and the completing nitriding reaction of some fine Al particles during flight. The feedstock particle size directly affects on the nitriding, melting, flowability, and the vaporization behaviors of Al powders during spraying. It concluded that using smaller particle size powders is useful for improving the nitriding ratio and not suitable for fabrication thick AlN coatings in reactive plasma spray process. To fabricate thick AlN coatings through RPS, enhancing the nitriding reaction of Al powders with large particle size during spraying is required.

Shahien, Mohammed; Yamada, Motohiro; Yasui, Toshiaki; Fukumoto, Masahiro

2011-03-01

167

A particle method for history-dependent materials  

SciTech Connect

A broad class of engineering problems including penetration, impact and large rotations of solid bodies causes severe numerical problems. For these problems, the constitutive equations are history dependent so material points must be followed; this is difficult to implement in an Eulerian scheme. On the other hand, purely Lagrangian methods typically result in severe mesh distortion and the consequence is ill conditioning of the element stiffness matrix leading to mesh lockup or entanglement. Remeshing prevents the lockup and tangling but then interpolation must be performed for history dependent variables, a process which can introduce errors. Proposed here is an extension of the particle-in-cell method in which particles are interpreted to be material points that are followed through the complete loading process. A fixed Eulerian grid provides the means for determining a spatial gradient. Because the grid can also be interpreted as an updated Lagrangian frame, the usual convection term in the acceleration associated with Eulerian formulations does not appear. With the use of maps between material points and the grid, the advantages of both Eulerian and Lagrangian schemes are utilized so that mesh tangling is avoided while material variables are tracked through the complete deformation history. Example solutions in two dimensions are given to illustrate the robustness of the proposed convection algorithm and to show that typical elastic behavior can be reproduced. Also, it is shown that impact with no slip is handled without any special algorithm for bodies governed by elasticity and strain hardening plasticity.

Sulsky, D.; Chen, Z.; Schreyer, H.L. [New Mexico Univ., Albuquerque, NM (United States)

1993-06-01

168

Method for the automated measurement of fine particle nitrate in the atmosphere  

SciTech Connect

An integrated collection and vaporization cell has been developed to provide automated, 10-min resolution monitoring of fine particle nitrate in the atmosphere. Particles are collected by a humidified impaction process and analyzed in place by flash vaporization and chemiluminescent detection of the evolved nitrogen oxides. Particle collection efficiency was measured between 95% and 100% for particles above 0.1 {micro}m. Evaporative losses for ammonium nitrate were 2 {+-} 4%. Average nitrate values from the automated system were compared to traditional denuder filter measurements in three cities, with correlation coefficients of greater than 0.97 and regression slopes ranging from 0.96 to 1.06. The detection limit is governed by the field blank, which for the Los Angeles area was 0.4 {micro}g/m{sup 3}. The system operated unattended for days at a time, with data recovery of 97%.

Stolzenburg, M.R.; Hering, S.V.

2000-03-01

169

A pin-on-disc investigation of novel nanoporous composite-based and conventional brake pad materials focussing on airborne wear particles  

Microsoft Academic Search

Wear particles originating from disc brakes contribute to particulate concentration in the urban atmosphere. In this work novel nanoporous composite-based and conventional brake materials were tested against cast-iron discs in a modified pin-on-disc machine. During testing airborne wear particles were measured online and collected on filters, which were analysed using SEM and EDX. The morphology of airborne wear particles containing

J. Wahlström; D. Gventsadze; L. Olander; E. Kutelia; L. Gventsadze; O. Tsurtsumia; U. Olofsson

2011-01-01

170

Coated or Embedded? Organic Matter as a Host for Individual Ambient Atmospheric Aerosol Particles (Invited)  

NASA Astrophysics Data System (ADS)

Organic matter is a prominent form of atmospheric aerosol particle. It commonly occurs with soot, sulfate, metals, or mineral dust in individual, internally mixed particles and is important when estimating radiative and health effects of aerosols. The details of these mini-assemblages are well observed when using transmission electron microscopy (TEM). When organic matter hosts soot particles, it enhances the light absorption of the soot and thus its warming effects. We determined the shapes of organic matter embedding soot using electron tomography (ET) with a transmission electron microscope, calculated the radiative forcing of such particles, and compared them to those of various coating and mixing models. Organic matter in particles collected from the vicinity of Mexico City (as part of the MILAGRO - Megacity Initiative: Local and Global Research Observations - campaign conducted in March 2006) also hosts metal-bearing nanoparticles that can include Fe, Zn, Mn, Pb, Hg, Sn, Cr, Ni, Ti, V, or Ag as major constituents. Nanoparticles of Hg are especially abundant. The nanoparticles are interesting because of their small sizes and high surface-to-volume ratios, both of which make them highly reactive in the human body and can cause negative health effects. In these and samples from other areas, we commonly find organic matter coating or otherwise associated with (hosting) inorganic aerosol particles of all types. Although the atmospheric community commonly speaks of coatings onto aerosol particles, in the case of organic matter, a more apt term might be embedding rather than coating. Finally, such hosting by organic matter can influence the climate and health effects of aerosol particles.

Buseck, P. R.; Adachi, K.

2009-12-01

171

Flux induced growth of atmospheric nano-particles by organic vapors  

NASA Astrophysics Data System (ADS)

Atmospheric aerosols play critical roles in air quality, public health, and visibility. In addition, they strongly influence climate by scattering solar radiation and by changing the reflectivity and lifetime of clouds. One major but still poorly understood source of atmospheric aerosol is new particle formation, which consists of the formation of thermodynamically stable clusters from trace gas molecules (homogeneous nucleation) followed by growth of these clusters to a detectable size (~3 nm). Because freshly nucleated clusters are most susceptible to loss due to high rate of coagulation with pre-existing aerosol population, the initial growth rate strongly influences the rate of new particle formation and ambient aerosol population. Whereas many field observations and modeling studies indicate that organics enhance the initial growth of the clusters and therefore new particle formation, thermodynamic considerations would suggest that the strong increase of equilibrium vapor concentration due to cluster surface curvature (Kelvin effect) may prevent ambient organics from condensing on these small clusters. Here the initial condensational growth of freshly nucleated clusters is described as heterogeneous nucleation of organic molecules onto these clusters. We find that the strong gradient in cluster population with respect to its size lead to positive cluster number flux, and therefore driving the growth of clusters substantially smaller than the Kelvin diameter, conventionally considered as the minimum particle size that can be grown through condensation. The conventional approach neglects this contribution from the cluster concentration gradient, and underestimates the rate of new particle formation by a factor of up to 60.

Wang, J.; McGraw, R. L.; Kuang, C.

2012-09-01

172

Nano- and Microscale Particles in Vortex Motions in Earth's Atmosphere and Ionosphere  

SciTech Connect

Vortex motions in the atmosphere are shown to be closely connected with dynamics of the dust nano- and microscale particles. The mechanism by which nano- and microscale particles are transported from the troposphere into the lower stratosphere by synoptic-scale vortices, simulated by the soliton solutions to the Charney-Obukhov equations (Rossby vortices), is described. Redistribution of dust particles in the ionosphere as a result of vortical motions is discussed. It is shown that excitation of acoustic-gravitational vortices at altitudes of 110-130 km as a result of development of acoustic-gravitational wave instability, associated with nonzero balance of heat fluxes, owing to solar radiation, water vapors condensation, infrared emission of the atmosphere, and thermal conductivity, leads to a substantial transportation of dust particles and their mixing at altitudes of 110-120 km. One of the ways of transportation of dust particles in the ionosphere is shown to be vertical flows (streamers), which are generated by dust vortices as a result of development of parametric instability.

Popel, S. I.; Izvekova, Yu. N. [Institute for Dynamics of Geospheres, Leninsky prospect 38, building 1, 119334 Moscow (Russian Federation); Shukla, P. K. [Institut fuer Theoretische Physik IV, Fakultaet fuer Physik und Astronomie, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany)

2010-12-14

173

Models for close-in atmospheric dispersion, explosive releases, and particle deposition  

SciTech Connect

Relatively simple models are presented to simulate close-in atmospheric dispersion, explosive releases, and particle deposition. Close-in generally refers to distances less than 50 m downwind from the source. These models assume simple gas dispersion (no chemical reactions, neutral buoyancy) and that particles behave as a gas expect they can be removed from the plume by a simple, deposition-velocity mechanism. These models have been combined into a QuickBASIC program (INEXPLC.BAS) and its PC executable form (INEXPLC.EXE). These programs, along with sample input and output files, are available from the author.

Bloom, S.G.

1993-10-06

174

Particle size distributions of currently used pesticides in a rural atmosphere of France  

NASA Astrophysics Data System (ADS)

This work presents first data on the particle size distributions of current-used pesticides in the atmosphere. Ambient air samples were collected using a cascade impactor distributed into four size fractions in a rural site of Centre Region (France). Most pesticides were accumulated in the fine (0.1-1 ?m) particle size fraction such as cyprodinil, pendimethalin, fenpropidin, fenpropimorph and spiroxamine. Other pesticides such as acetochlor and metolachlor presented a bimodal distribution with maximum concentrations in the ultrafine (0.03-0.1 ?m)-coarse (1-10 ?m) and in the ultrafine-fine size ranges, respectively. No pesticides were detected in the size fraction >10 ?m.

Coscollà, Clara; Yahyaoui, Abderrazak; Colin, Patrice; Robin, Corine; Martinon, Laurent; Val, Stéphanie; Baeza-Squiban, Armelle; Mellouki, Abdelwahid; Yusà, Vicent

175

Wavelength-dependent optical extinction of carbonaceous particles in atmospheric aerosols and interstellar dust.  

PubMed

Optical extinction spectra for particles of structurally disordered carbonaceous material (carbon black, soot) are discussed in terms of the effects of size and shape and the difference between coagulated and coalesced particles. For this purpose, the orientation-averaged specific extinction for several compact and open aggregates of spherical particles is calculated and compared with the specific extincton by homogeneous particles, i.e., volume-equivalent sphere and elongated spheroids. The extinction spectra are calculated for wavelengths from 0.2 to 1000 microm by use of the optical constants for the carbonaceous materials of Jäger et al. [Astron. Astrophys. 332, 291 (1998)] and Schnaiter et al. [Astrophys. J. 498, 486 (1998)]. Comparisons with the model case of particles composed of graphite and with measurements of diesel soot aerosols are made. PMID:12463258

Quinten, Michael; Kreibig, Uwe; Henning, Thomas; Mutschke, Harald

2002-11-20

176

Some inferences on the mechanism of atmospheric gas\\/particle partitioning of polycyclic aromatic hydrocarbons (PAH) at Zaragoza (Spain)  

Microsoft Academic Search

Gas\\/particle partitioning of pollutants is an important mechanism determining atmospheric processing and its impact to environmental and human health. In this paper, the gas–particle partitioning of polycyclic aromatic hydrocarbons (PAH) has been studied with the aim of determining the main mechanism of PAH partitioning in Zaragoza (Spain) aerosols. To reach this goal, the ambient concentrations of PAH (gas and particle

M. S. Callén; M. T. de la Cruz; J. M. López; R. Murillo; M. V. Navarro; A. M. Mastral

2008-01-01

177

Study of nitro-polycyclic aromatic hydrocarbons in fine and coarse atmospheric particles  

Microsoft Academic Search

The purpose of the present study was to evaluate six nitro-polycyclic aromatic hydrocarbons (NPAHs) in fine (<2.5?m) and coarse (2.5–10?m) atmospheric particles in an urban and industrial area located in the Metropolitan Area of Porto Alegre (MAPA), RS, Brazil. The method used was of NPAHs isolation and derivatization, and subsequent gas chromatography by electron capture detection (CG\\/ECD). Results revealed a

Elba Calesso Teixeira; Karine Oliveira Garcia; Larissa Meincke; Karen Alam Leal

2011-01-01

178

Femtosecond Laser Ablation Particle Introduction to a Liquid Sampling-Atmospheric Pressure Glow Discharge Ionization Source  

Microsoft Academic Search

This work describes the use of a compact, liquid sampling atmospheric pressure glow discharge (LS-APGD) ionization source to ionize metal particles within a laser ablation aerosol. Mass analysis was performed with a Thermo Scientific Exactive Mass Spectrometer which utilizes an orbitrap mass analyzer capable of producing mass resolution exceeding M\\/M > 160,000. The LS-APGD source generates a low-power plasma between

Anthony J. Carado; C. Derrick Quarles; Andrew M. Duffin; Charles J. Barinaga; Richard Russo; R. Kenneth Marcus; Gregory C. Eiden; David W. Koppenaal

2012-01-01

179

Modelling new particle formation from Jülich plant atmosphere chamber and CERN CLOUD chamber measurements  

NASA Astrophysics Data System (ADS)

An MALTE-BOX model is used to study the effects of oxidation of SO2 and BVOCs to new particle formation from Jülich Plant Atmosphere Chamber and CERN CLOUD chamber measurements. Several days of continuously measurements were chosen for the simulation. Our preliminary results show that H2SO4 is one of the critical compounds in nucleation process. Nucleation involving the oxidation of BVOCs shows better agreements with measurements.

Liao, Li; Boy, Michael; Mogensen, Ditte; Schobesberger, Siegfried; Franchin, Alessandro; Mentel, Thomas F.; Kleist, Einhard; Kiendler-Scharr, Astrid; Kulmala, Markku; dal Maso, Miikka

2013-05-01

180

Aging of organic materials around high-energy particle accelerators  

NASA Astrophysics Data System (ADS)

Around particle accelerators used for fundamental research on the basic structure of matter, materials and components are exposed to ionizing radiation caused by beam losses in the proton machines and by synchrotron radiation in the lepton machines. Furthermore, with the high-energy and high-intensity collisions produced from future colliders, radiation damage is also to be expected in particle-physics detectors. Therefore, for a safe and reliable operation, the radiation aging of most of the components has to be assessed prior to their selection. An extensive radiation-damage test program has been carried out at CERN for decades on a routine basis and many results have been published. The tests have mainly concentrated on magnet-coil insulations and cable-insulating materials; they are carried out in accordance with the IEC 544 standard which defines the mechanical tests to be performed and the methods of degradation evaluation. The mechanical tests are also used to assess the degradation of composite structural materials. Moreover, electrical properties of high-voltage insulations and optical properties of organic scintillators and wave guides have also been studied. Our long-term experience has pointed out many parameters to be taken into account for the estimate of the lifetime of components in the radiation environment of our accelerators. One of the main parameters is the dose-rate effect, but the influence of other parameters has sometimes to be taken into account.

Tavlet, M.

1997-08-01

181

Gas/particle concentrations and partitioning of PCBs in the atmosphere of Korea  

NASA Astrophysics Data System (ADS)

Air samples were taken in a rural area of Kyonggi-do of South Korea to investigate gas/particle concentration and partitioning. Gas/particle phase concentrations of polychlorinated biphenyls (PCBs) were measured over 48 h periods from September 2001 to July 2002. The average contribution (%) of gas to particle was about 90%, which suggests that in the atmosphere PCBs predominantly existed in the gas phase. The correlation coefficients ( r) between total PCBs and temperature (°C) showed negative correlation for particle phase and positive correlation for gas phase. The contribution (%) of PCB congeners to total PCBs in gas phase increased with decreasing chlorine substitution. The particle contribution (%) of PCB congeners increased for the less volatile congeners, i.e., those with the higher chlorine number. The coefficient of determination ( R2) between log ( Cparticle/ Cgas) and log KOA was 0.86, which implies that heavier PCB congeners exist more in particle phase than gas phase compared to lighter PCBs. Partitioning of PCBs between gas and particle phases correlated well with the sub-cooled liquid vapor pressure ( PoL) and the octanol-air partition coefficient ( KOA) for all samples, but the coefficient of determination ( R2) differed for each season.

Yeo, Hyun-Gu; Choi, Minkyu; Chun, Man-Young; Sunwoo, Young

182

Atmospheric amines - Part II. Thermodynamic properties and gas/particle partitioning  

NASA Astrophysics Data System (ADS)

Amines enter the atmosphere from a wide range of sources, but relatively little is known about their atmospheric behavior, especially their role in gas/particle partitioning. In Part I of this work ( Ge et al., 2011) a total of 154 amines, 32 amino acids and urea were identified as occurring in the atmosphere, based upon a survey of the literature. In this work we compile data for the thermodynamic properties of the amines which control gas/particle partitioning (Henry's Law constant, liquid vapor pressure, acid dissociation constant, activity coefficient and solubility in water), and also estimate the solid/gas dissociation constants of their nitrate and chloride salts. Prediction methods for boiling point, liquid vapor pressure, acid dissociation constant and the solubility of the amines in water are evaluated, and used to estimate values of the equilibrium constants where experimental data are lacking. Partitioning of amines into aqueous aerosols is strongly dependent upon pH and is greatest for acidic aerosols. For several common amines the tendency to partition to the particle phase is similar to or greater than that of ammonia. Our results are presented as tables of values of thermodynamic equilibrium constants, which are also incorporated into the Extended Aerosol Inorganics Model ( E-AIM, http://www.aim.env.uea.ac.uk/aim/aim.php) to enable gas/aerosol partitioning and other calculations to be carried out.

Ge, Xinlei; Wexler, Anthony S.; Clegg, Simon L.

2011-01-01

183

Trends on atmospheric new particle formation - 16 years of observations in boreal forest  

NASA Astrophysics Data System (ADS)

Research on new particle formation (NPF) in the atmosphere has been very active during the last two decades. This phenomenon has been observed in various environments around the world [1]. One of the longest and most comprehensive data sets of atmospheric aerosol properties is available from the University of Helsinki SMEAR II station in Hyytiälä, southern Finland [2]. Ambient aerosol size distributions have been measured at Hyytiälä since January 1996 with a DMPS system covering particle size range 3 - 1000 nm (3 - 500 nm until end of 2004; see Aalto et al., 2001 [3]). Aerosol measurements are complemented by measurements of basic meteorological variables, trace gas concentrations (SO2, O3, CO, CO2, NO, NOx), and quantities related to the soil and forest surrounding the station. Until end of 2011 we have observed 1337 days with regional NPF events, i.e. formation of new 3 nm particles followed by particle growth to sizes of 30-50 nm typically within 10-20 hours. The number of nucleation events detected at Hyytiälä varies from year to year in the range 60 - 120 per year. The reasons behind this quite substantial variation are not yet found. We have, however, established that the variation of the galactic cosmic ray intensity due to the 11 year solar cycle is not connected to the particle formation intensity at Hyytiälä [4]. Mean values and observed trends in the quantities relative to NPF are listed in Table 1. There is no significant trend in the formation rates of 3 nm particles. In contrast, the growth rates are increasing by 3% per year relative to their 16 year mean value. Concentrations of sulphuric acid, which is the most important precursor vapor in atmospheric NPF, can be approximated with a simple proxy model [5]. This proxy takes into account the source from SO2 and the condensation sink by pre-existing particles. Both the SO2 concentration and CS are decreasing in Hyytiälä, but the relative change in SO2 is larger. This leads to a decreasing trend of 4% per year also in the H2SO4 proxy concentration, and suggests that the observed increase in the particle growth rates could be caused by increased concentrations of organic compounds and their oxidation products. As the emissions of these biogenic organic compounds are highly temperature dependent, increasing global temperatures can lead to a larger fraction of newly formed particles reaching cloud condensation nuclei sizes and this way NPF becoming more significant to climate.

Nieminen, T.; Dal Maso, M.; Petäjä, T.; Aalto, P. P.; Kerminen, V.-M.; Hari, P.; Kulmala, M.

2012-04-01

184

49 CFR 195.581 - Which pipelines must I protect against atmospheric corrosion and what coating material may I use?  

Code of Federal Regulations, 2011 CFR

...must I protect against atmospheric corrosion and what coating material may I...HAZARDOUS LIQUIDS BY PIPELINE Corrosion Control § 195.581 Which pipelines...must I protect against atmospheric corrosion and what coating material may...

2011-10-01

185

49 CFR 195.581 - Which pipelines must I protect against atmospheric corrosion and what coating material may I use?  

Code of Federal Regulations, 2012 CFR

...must I protect against atmospheric corrosion and what coating material may I...HAZARDOUS LIQUIDS BY PIPELINE Corrosion Control § 195.581 Which pipelines...must I protect against atmospheric corrosion and what coating material may...

2012-10-01

186

Impact of cosmic rays and solar energetic particles on the Earth's ionosphere and atmosphere  

NASA Astrophysics Data System (ADS)

A brief review of the study during COST Action ES0803 of effects due to cosmic rays (CR) and solar energetic particles (SEP) in the ionosphere and atmosphere is presented. Models CORIMIA (COsmic Ray Ionization Model for Ionosphere and Atmosphere) and application of CORSIKA (COsmic Ray SImulations for KAscade) code are considered. They are capable to compute the cosmic ray ionization profiles at a given location, time, solar and geomagnetic activity. Intercomparison of the models, as well as comparison with direct measurements of the atmospheric ionization, validates their applicability for the entire atmosphere and for the different levels of the solar activity. The effects of CR and SEP can be very strong locally in the polar cap regions, affecting the physical-chemical and electrical properties of the ionosphere and atmosphere. Contributions here were also made by the anomalous CR, whose ionization is significant at high geomagnetic latitudes (above 65°-70°). Several recent achievements and application of CR ionization models are briefly presented. This work is the output from the SG 1.1 of the COST ES0803 action (2008-2012) and the emphasis is given on the progress achieved by European scientists involved in this collaboration.

Velinov, Peter I. Y.; Asenovski, Simeon; Kudela, Karel; Lastovicka, Jan; Mateev, Lachezar; Mishev, Alexander; Tonev, Peter

2013-03-01

187

Chemical imaging analysis of environmental particles using the focused ion beam/scanning electron microscopy technique: microanalysis insights into atmospheric chemistry of fly ash.  

PubMed

Airborne fly ash from coal combustion may represent a source of bioavailable iron (Fe) in the open ocean. However, few studies have focused on Fe speciation and distribution in coal fly ash. In this study, chemical imaging of fly ash has been performed using a dual-beam focused ion beam/scanning electron microscope (FIB/SEM) system for a better understanding of how simulated atmospheric processing can modify the morphology, chemical composition and element distribution within individual particles. A novel approach has been applied for cross-sectioning fly ash particles with the FIB in order to explore element distribution within the interior of individual particles. Our results indicate that simulated atmospheric processing can cause disintegration of aluminosilicate glass, a dominant material in fly ash particles. Fe present in the inner core of fly ash spheres within the aluminosilicate phase is more easily mobilized compared with Fe oxides present as surface aggregates on the exterior of fly ash spheres. Fe dissolution depends strongly on Fe speciation in fly ash particles. The approach for preparation of a cross-sectioned specimen described here opens up new opportunities for particle microanalysis, particularly with respect to inorganic refractive materials like fly ash and mineral dust. PMID:23207643

Chen, Haihan; Grassian, Vicki H; Saraf, Laxmikant V; Laskin, Alexander

2013-01-21

188

Influence of barrier material and surface roughness on atmospheric pressure uniform dielectric barrier discharge in air  

Microsoft Academic Search

Summary form only given. An atmospheric pressure uniform discharge has a great potential for improving surface treatment, efficiency of ozone generation, de-NOx and so on. So far, we have studied a stable generation of atmospheric pressure uniform discharge using dielectric barrier discharge device, and we already reported that by elevating barrier temperature or by using acrylic barrier material, the discharge

N. Osawa; Y. Mochizuki; Y. Yoshioka

2009-01-01

189

Probing new physics with long-lived charged particles produced by atmospheric and astrophysical neutrinos  

SciTech Connect

As suggested by some extensions of the standard model of particle physics, dark matter may be a super-weakly-interacting lightest stable particle, while the next-to-lightest particle (NLP) is charged and metastable. One could test such a possibility with neutrino telescopes, by detecting the charged NLPs produced in high-energy neutrino collisions with Earth matter. We study the production of charged NLPs by both atmospheric and astrophysical neutrinos; only the latter, which is largely uncertain and has not been detected yet, was the focus of previous studies. We compute the resulting fluxes of the charged NLPs, compare those of different origins and analyze the dependence on the underlying particle physics set-up. We point out that, even if the astrophysical neutrino flux is very small, atmospheric neutrinos, especially those from the prompt decay of charmed mesons, may provide a detectable flux of NLP pairs at neutrino telescopes such as IceCube. We also comment on the flux of charged NLPs expected from proton-nucleon collisions and show that, for theoretically motivated and phenomenologically viable models, it is typically subdominant and below detectable rates.

Ando, Shin'ichiro; Profumo, Stefano [California Institute of Technology, Pasadena, CA 91125 (United States); Beacom, John F [Department of Physics, Ohio State University, Columbus, OH 43210 (United States); Rainwater, David, E-mail: ando@tapir.caltech.edu, E-mail: beacom@mps.ohio-state.edu, E-mail: profumo@caltech.edu, E-mail: rain@pas.rochester.edu [Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627 (United States)

2008-04-15

190

Automated inspection of tubular material based on magnetic particle inspection  

NASA Astrophysics Data System (ADS)

Automatic industrial surface inspection methodology based on Magnetic Particle Inspection is developed from image acquisition to defect classification. First the acquisition system is optimized, then tubular material images are acquired, reconstructed then stored. The characteristics of the crack-like defects with respect to its geometric model and curvature are used as a priori knowledge for mathematical morphology and linear filtering. After the segmentation and binarization of the image, vast amount of defect candidates exist. Finally classification is performed with decision tree learning algorithm due to its robustness and speed. The parameters for mathematical morphology, linear filtering and classification are analyzed and optimized with Design Of Experiments based on Taguchi approach. The most significant parameters obtained may be analyzed and tuned further. Experiments are performed on tubular materials and evaluated by its accuracy and robustness by comparing ground truth and processed images. The result is promising with 97 % True Positive and only 0.01 % False Positive rate on the testing set.

Mahendra, Adhiguna; Stolz, Christophe; Meriaudeau, Fabrice; Petit, Sebastien; Noel, Alexandre; Degoutin, Fabien

2012-02-01

191

Study of nitro-polycyclic aromatic hydrocarbons in fine and coarse atmospheric particles  

NASA Astrophysics Data System (ADS)

The purpose of the present study was to evaluate six nitro-polycyclic aromatic hydrocarbons (NPAHs) in fine (< 2.5 ?m) and coarse (2.5-10 ?m) atmospheric particles in an urban and industrial area located in the Metropolitan Area of Porto Alegre (MAPA), RS, Brazil. The method used was of NPAHs isolation and derivatization, and subsequent gas chromatography by electron capture detection (CG/ECD). Results revealed a higher concentration of NPAHs, especially 3-nitrofluoranthene and 1-nitropyrene, in fine particles in the sampling sites studied within the MAPA. The diagnostic ratios calculated for PAHs and NPAHs identified the influence of heavy traffic, mainly of diesel emissions. The correlation of NPAHs with other pollutants (NOx, NO2, NO and O3) evidence the influence of vehicular emissions in the MAPA. The seasonal variation evidenced higher NPAHs concentrations in the fine particles during winter for most compounds studied.

Teixeira, Elba Calesso; Garcia, Karine Oliveira; Meincke, Larissa; Leal, Karen Alam

2011-08-01

192

Advanced Process Technology: Combi Materials Science and Atmospheric Processing (Fact Sheet)  

SciTech Connect

Capabilities fact sheet for the National Center for Photovoltaics: Process Technology and Advanced Concepts -- High-Throughput Combi Material Science and Atmospheric Processing that includes scope, core competencies and capabilities, and contact/web information.

Not Available

2011-06-01

193

Acoustic Properties and Durability of Liner Materials at Non-Standard Atmospheric Conditions.  

National Technical Information Service (NTIS)

This report documents the results of an experimental study on how acoustic properties of certain absorbing liner materials are affected by nonstandard atmospheric conditions. This study was motivated by the need to assess risks associated with incorporati...

K. K. Ahuja R. J. Gaeta J. S. Hsu

1994-01-01

194

Evidences for New Particle Formation in the Arctic as a Part of TOPSE Atmospheric Nucleation Event  

NASA Astrophysics Data System (ADS)

Simultaneous measurements of ultrafine particles and precursor gases show evidences of new particle formation over a wide range of latitude in the free tropospheric Arctic region. However, the exact mechanism of new particle formation is uncertain. In this study, in-situ measurements taken during deployment 3 (Flight 16, March 7, 2000, Churchill-Churchill, 13:25-18:33 GMT) as a part of Tropospheric Ozone Production about Spring Equinox (TOPSE) experiment, over Western Canada were used for comparison with the model predictions. Using a combination of satellite derived brightness temperature, air parcel backward trajectory information, in-situ measurements of aerosol and precursor gases and aerosol microphysical model [Tripathi et al., 2004] driven by parameterized ion induced nucleation [Modgil et al., 2005], we have investigated the plausible mechanism responsible for, and factors leading to, new particle formation in the middle to upper troposphere during TOPSE atmospheric nucleation event. The reasonable agreement between model predicted and observed ultrafine particles of diameter 3 to 4 nm and 3 to 8 nm suggest that new particle formation is likely to occur by ion induced nucleation mechanism during TOPSE nucleation event. A significant finding is that the lowering of pre-existing particle surface, in the region of cloud outflow, triggered particle nucleation in this region. These studies indicate that, at typical middle to upper tropospheric conditions of Arctic, ion mechanism is an important source of ultrafine particles and these freshly particles can grow to act as cloud condensation nuclei (CCN), which have implications for cloud radiative properties. References Modgil, M. S., Sanjeev Kumar, S. N. Tripathi, and E. R. Lovejoy, A parameterization of ion-induced nucleation of sulfuric acid and water for atmospheric conditions, J. Geophys. Res., In press, 2005. Tripathi, S. N., X. P. Vancassel, R. G. Grainger, and H. L. Rogers, A Fast Stratospheric Aerosol Microphysical Model (SAMM): H2SO4-H2O Aerosol Development and Validation, AOPP Memorandum 2004.1, Department of Physics, University of Oxford, 2004. http://www.atm.ox.ac.uk/main/research/technical.html

Tripathi, S. N.; Kanawade, V. P.

2005-12-01

195

The transmission of differing energy beta particles through various materials  

SciTech Connect

The transmission of beta particles is frequently calculated in the same fashion as that of gamma rays, where the mass attenuation coefficient is defined by the slope of the exponential function. Numerous authors have used this approximation including Evans (1955), Loevinger (1952), and Chabot et. al. (1988). Recent work by McCarthy et. al. (1995) indicated that the exponential function seemed to fit well over a particular region of the transmission curve. Upon further investigation, the author decided to verify McCarthy`s results by the use of different absorber materials and attempt to reproduce the experiments. A theoretical method will be used to estimate the transmission of the beta particles through the three absorbers, aluminum, zirconium, and iron. An alternate Monte Carlo code, the Electron Gamma Shower version 4 code (EGS4) will also be used to verify that the experiment is approximating a pencil beam of beta particles. Although these two methods offer a good cross check for the experimental data, they pose a conflict in regards to the type of beam that is to be generated. The experimental lab setup uses a collimated beam of electrons that will impinge upon the absorber, while the codes are written using a pencil beam. A minor discrepancy is expected to be observed in the experimental results and is currently under investigation by McCarthy. The results of this project supported the theory that the beta mass attenuation coefficient was accurately represented by the slope of an exponential function, but only for that particular region of the transmission curve that has a minimal absorber thickness. By fitting the data beyond 50% of the beta particle range this theory does not hold true. The theory generated by McCarthy (1995) and the EGS4 Monte Carlo code indicated that the transmission curve for a pencil beam was not accurately represented by an exponential function. The results of this experiment appeared to provide additional support to this assumption.

Quayle, D.R.

1996-04-01

196

In situ measurements of gas/particle-phase transitions for atmospheric semivolatile organic compounds.  

PubMed

An understanding of the gas/particle-phase partitioning of semivolatile compounds is critical in determining atmospheric aerosol formation processes and growth rates, which in turn affect global climate and human health. The Study of Organic Aerosol at Riverside 2005 campaign was performed to gain a better understanding of the factors responsible for aerosol formation and growth in Riverside, CA, a region with high concentrations of secondary organic aerosol formed through the phase transfer of low-volatility reaction products from the oxidation of precursor gases. We explore the ability of the thermal desorption aerosol gas chromatograph (TAG) to measure gas-to-particle-phase transitioning for several organic compound classes (polar and nonpolar) found in the ambient Riverside atmosphere by using in situ observations of several hundred semivolatile organic compounds. Here we compare TAG measurements to modeled partitioning of select semivolatile organic compounds. Although TAG was not designed to quantify the vapor phase of semivolatile organics, TAG measurements do distinguish when specific compounds are dominantly in the vapor phase, are dominantly in the particle phase, or have both phases present. Because the TAG data are both speciated and time-resolved, this distinction is sufficient to see the transition from vapor to particle phase as a function of carbon number and compound class. Laboratory studies typically measure the phase partitioning of semivolatile organic compounds by using pure compounds or simple mixtures, whereas hourly TAG phase partitioning measurements can be made in the complex mixture of thousands of polar/nonpolar and organic/inorganic compounds found in the atmosphere. PMID:20142511

Williams, Brent J; Goldstein, Allen H; Kreisberg, Nathan M; Hering, Susanne V

2010-02-08

197

Formation of bioorganic compounds in simulated planetary atmospheres by high energy particles or photons.  

PubMed

Various types of organic compounds have been detected in Jupiter, Titan, and cometary coma. It is probable that organic compounds were formed in primitive Earth and Mars atmospheres. Cosmic rays and solar UV are believed to be two major energy sources for organic formation in space. We examined energetics of organic formation in simulated planetary atmospheres. Gas mixtures including a C-source (carbon monoxide or methane) and a N-source (nitrogen or ammonia) was irradiated with the followings: High energy protons or electrons from accelerators, gamma-rays from 60Co, UV light from a deuterium lamp, and soft X-rays or UV light from an electron synchrotron. Amino acids were detected in the products of particles, gamma-rays and soft X-rays irradiation from each gas mixture examined. UV light gave, however, no amino acid precursors in the gas mixture of carbon monoxide, nitrogen and nitrogen. It gave only a trace of them in the gas mixture of carbon monoxide, ammonia and water or that of methane, nitrogen and water. Yield of amino acid precursors by photons greatly depended on their wavelength. These results suggest that nitrogen-containing organic compounds like amino acid precursors were formed chiefly with high energy particles, not UV photons, in Titan or primitive Earth/Mars atmospheres where ammonia is not available as a predominant N-source. PMID:11605633

Kobayashi, K; Masuda, H; Ushio, K I; Ohashi, A; Yamanashi, H; Kaneko, T; Takahashi, J I; Hosokawa, T; Hashimoto, H; Saito, T

2001-01-01

198

The importance of soot particles and nitrous acid in oxidizing SO 2 in atmospheric aqueous droplets  

NASA Astrophysics Data System (ADS)

Soot particles catalyze the oxidation of SO 2 H 2O, HSO 3-, and SO 2-3 species at the same rate; however, the rate of production of sulfate is not constant at a constant partial pressure of SO 2. The rate decreases as the pH decreases because the total concentration of S(IV) in aqueous droplets decreases as the pH decreases. The sulfate production rate has a complex dependence on the concentration of S(IV) and is not very sensitive to a change in SO 2 concentration at normal atmospheric conditions. The oxidation of SO 2 by HNO 2 in atmospheric water droplets first produces hydroxylamine disulfonate, which undergoes acid-catalyzed hydrolysis to form sulfate and hydroxylamine monosulfonate. The latter can react with HNO 2 and would then end up as nitrous oxide and sulfate Model calculations have been made comparing the relative importance of the sulfate production mechanism by soot particles and nitrous acid with other mechanisms involving liquid water. The results indicate that both soot and HNO 2 mechanisms can be very important when the lifetime of the atmospheric aqueous droplets is long.

Chang, S. G.; Toossi, R.; Novakov, T.

199

Carbonaceous particles in the atmosphere and precipitation of the Nam Co region, central Tibet.  

PubMed

A continuous air and precipitation sampling for carbonaceous particles was conducted in a field observatory beside Nam Co, Central Tibetan Plateau during July of 2006 through January of 2007. Organic carbon (OC) was the dominant composition of the carbonaceous particles both in the atmosphere (1660 ng/m3) and precipitation (476 ng/g) in this area, while the average elemental carbon (BC) concentrations in the atmosphere and precipitation were only 82 ng/m3 and 8 ng/g, respectively. Very high OC/BC ratio suggested local secondary organic carbon could be a dominant contribution to OC over the Nam Co region, while BC could be mainly originated from Southern Asia, as indicated by trajectory analysis and aerosol optical depth. Comparison between the BC concentrations measured in Lhasa, those at "Nepal Climate Observatory at Pyramid (NCO-P)" site on the southern slope of the Himalayas, and Nam Co suggested BC in the Nam Co region reflected a background with weak anthropogenic disturbances and the emissions from Lhasa might have little impact on the atmospheric environment here, while the pollutants from the Indo-Gangetic Basin of Southern Asia could be transported to the Nam Co region by both the summer monsoon and the westerly. PMID:21235163

Ming, Jing; Xiao, Cunde; Sun, Junying; Kang, Shichang; Bonasoni, Paolo

2010-01-01

200

Determination of iodine and bromine in coal and atmospheric particles by inductively coupled plasma mass spectrometry.  

PubMed

Bromine and iodine in atmospheric particles or coal can cause environmental problems such as destruction of ozone in the atmosphere; therefore, the presence of these compounds has recently received increased attention. Here, a rapid and reliable method for the simultaneous determination of total bromine and iodine using ICP-MS analysis is described. Samples were dissolved in mixtures of 5 mL of HNO(3) and 2 mL of H(2)O(2) in a high pressure microwave digester. The solution was then oxidized by per-sulfate (Na(2)S(2)O(8)) in addition to a small amount of silver nitrate, after which the total bromine and iodine were measured simultaneously by ICP-MS. The signal memory effects of bromine and iodine during analysis were effectively decreased by washing with a new mixture agent (2% alcohol acidic solution, pH 1-2 adjusted with HCl). The detection limits for bromine and iodine using this method were about 3.2 microg L(-1) and 1.1 microg L(-1), respectively. Additionally, the spike recoveries were between 78.7% and 121% for bromine and iodine analysis, while the relative standard deviations ranged from 4.3% to 9.7%, and from 1.5% to 3.4% for bromine and iodine, respectively. The results of this study indicate that the method described here is suitable for the analysis of micro-amounts of bromine and iodine in atmospheric particles and coal samples. PMID:20188948

Sun, Mingxing; Gao, Yunchuan; Wei, Biwen; Wu, Xiaowei

2009-12-23

201

Students 'Weigh' Atmospheric Pollution.  

ERIC Educational Resources Information Center

|Describes a procedure developed by students that measures the mass concentration of particles in a polluted urban atmosphere. Uses a portable fan and filters of various materials. Compares students' data with official data. (DDR)|

Caporaloni, Marina

1998-01-01

202

Asian dust particles converted into aqueous droplets under remote marine atmospheric conditions  

PubMed Central

The chemical history of dust particles in the atmosphere is crucial for assessing their impact on both the Earth’s climate and ecosystem. So far, a number of studies have shown that, in the vicinity of strong anthropogenic emission sources, Ca-rich dust particles can be converted into aqueous droplets mainly by the reaction with gaseous HNO3 to form Ca(NO3)2. Here we show that other similar processes have the potential to be activated under typical remote marine atmospheric conditions. Based on field measurements at several sites in East Asia and thermodynamic predictions, we examined the possibility for the formation of two highly soluble calcium salts, Ca(NO3)2 and CaCl2, which can deliquesce at low relative humidity. According to the results, the conversion of insoluble CaCO3 to Ca(NO3)2 tends to be dominated over urban and industrialized areas of the Asian continent, where the concentrations of HNO3 exceed those of HCl ([HNO3/HCl] >  ? 1). In this regime, CaCl2 is hardly detected from dust particles. However, the generation of CaCl2 becomes detectable around the Japan Islands, where the concentrations of HCl are much higher than those of HNO3 ([HNO3/HCl] <  ? 0.3). We suggest that elevated concentrations of HCl in the remote marine boundary layer are sufficient to modify Ca-rich particles in dust storms and can play a more important role in forming a deliquescent layer on the particle surfaces as they are transported toward remote ocean regions.

Tobo, Yutaka; Zhang, Daizhou; Matsuki, Atsushi; Iwasaka, Yasunobu

2010-01-01

203

A model for the atmospheric transport of sea-salt particles in coastal areas  

NASA Astrophysics Data System (ADS)

A model for the aerosol transport in the lower atmosphere is of great interest for studies on air and water quality. One of the difficulties of such a model is to provide the accurate source terms. In particular, for maritime environment, the production of particles generated at the air-sea interface by breaking waves largely varies in time and space (Piazzola et al., 2009). More particularly, near the coastal zone, the sea-spray aerosol fluxes depend on the development of the wave field. The present paper proposes some improvement of the model MACMod, published by Tedeschi and Piazzola (2011), which is dedicated to the transport of aerosol particles in the marine atmospheric boundary layer (MABL). Taking benefit of the experimental campaign MIRAMER conducted in the French Mediterranean in 2008, a new sea-spray source function has been introduced in the latter version of the model MACMod. This consists in a revisited version of the whitecap dependant formulation established by Monahan et al. (1986). The simulations were then validated using aerosol size distributions recorded on board the ship "Atalante" for different wind speeds. Error calculations show a good performance of the model since it predicts the aerosol concentration to within a maximum factor of 3 for particle radii between 0.5 to 5 ?m.

Demoisson, A.; Tedeschi, G.; Piazzola, J.

2013-10-01

204

Model for Single-Particle Erosion of Ductile Materials.  

National Technical Information Service (NTIS)

A model, based on engineering principles, is developed to predict surface erosion caused by the impact of a single particle. The particle trajectory is determined by solving the equations that govern the particle's motion during its contact with the surfa...

T. L. Urso

1985-01-01

205

Particle excitation, airglow and H2 vibrational disequilibrium in the atmosphere of Jupiter  

SciTech Connect

The extreme ultraviolet EUV emission produced by particle excitation of the hydrogen atmospheres of Jupiter and Saturn is examined using model calculations to determine the nature of the energy deposition process and the effect of such processes on atmospheric structure. Tasks ranging from examination of phenomenologically related processes on Saturn and Titan to analysis of experimental laboratory data required to allow accurate modeling of emissions from hydrogenic atmospheres are investigated. An explanation of the hydrogen H Ly(alpha) bulge in Jupiter's emission from the equatorial region is presented. It is proposed that Saturn, rather than Titan is the major source of the extended hydrogen cloud. The atomic hydrogen detected at the rings of Saturn may originate predominantly from the same source. A cross calibration is obtained between the Pioneer 10 EUV photometer and the Voyager EUV spectrometers, thus providing a direct measure of the temporal morphology of Jupiter between a minimum and a maximum in solar activity. Atomic and molecular data required for the research program are analyzed. An extrapolation of conditions in the upper atmospheres of Jupiter and Saturn produces a predicted condition at Uranus in terms of excitation and hydrogen escape rates that may be observed at Voyager-Uranus encounter.

Shemansky, D.E.

1984-09-01

206

Organic acids in different size classes of atmospheric particulate material  

Microsoft Academic Search

During fall and winter 1986-87, aerosol samples were collected with a 5-stage impactor in an urban, a suburban and a rural area in Central Europe. The weak acid content of aerosol particles was characterized by buffer capacity titrations, and organic acids were determined. C4-C6 dicarboxylic acids were found to be the main constituents of aerosol organic acids, with the highest

J. Ludwig; O. Klemm

1988-01-01

207

Characterization of Complex Organic Compounds Formed in Simulated Planetary Atmospheres by the Action of High Energy Particles  

NASA Astrophysics Data System (ADS)

A wide variety of organic compounds, which are not simple organics but also complex organics, have been found in planets and comets. We reported that complex organics was formed in simulated planetary atmospheres by the action of high energy particles. Here we characterized the experimental products by using chromatographic and mass spectrometric techniques. A gaseous mixture of CO, N2 and H2O was irradiated with high energy protons (major components of cosmic rays). Water-soluble non-volatile substances, which gave amino acids after acid-hydrolysis, were characterized by HPLC and mass spectrometry. Major part of the products were complex compounds with molecular weight of several hundreds. Amino acid precursors were produced even when no water was incorporated with the starting materials. It was suggested that complex molecules including amino acid precursors were formed not in solution from simple molecules like HCN, but directly in gaseous phase

Kobayashi, Kensei; Kaneko, Takeo; Saito, Takeshi

1999-01-01

208

Characterization of complex organic compounds formed in simulated planetary atmospheres by the action of high energy particles.  

PubMed

A wide variety of organic compounds, which are not simple organics but also complex organics, have been found in planets and comets. We reported that complex organics was formed in simulated planetary atmospheres by the action of high energy particles. Here we characterized the experimental products by using chromatographic and mass spectrometric techniques. A gaseous mixture of CO, N2 and H2O was irradiated with high energy protons (major components of cosmic rays). Water-soluble non-volatile substances, which gave amino acids after acid-hydrolysis, were characterized by HPLC and mass spectrometry. Major part of the products were complex compounds with molecular weight of several hundreds. Amino acid precursors were produced even when no water was incorporated with the starting materials. It was suggested that complex molecules including amino acid precursors were formed not in solution from simple molecules like HCN, but directly in gaseous phase. PMID:11543332

Kobayashi, K; Kaneko, T; Saito, T

1999-01-01

209

Dispersion of aerosol particles in the free atmosphere using ensemble forecasts  

NASA Astrophysics Data System (ADS)

The dispersion of aerosol particle pollutants is studied using 50 members of an ensemble forecast in the example of a hypothetical free atmospheric emission above Fukushima over a period of 2.5 days. Considerable differences are found among the dispersion predictions of the different ensemble members, as well as between the ensemble mean and the deterministic result at the end of the observation period. The variance is found to decrease with the particle size. The geographical area where a threshold concentration is exceeded in at least one ensemble member expands to a 5-10 times larger region than the area from the deterministic forecast, both for air column "concentration" and in the "deposition" field. We demonstrate that the root-mean-square distance of any particle from its own clones in the ensemble members can reach values on the order of one thousand kilometers. Even the centers of mass of the particle cloud of the ensemble members deviate considerably from that obtained by the deterministic forecast. All these indicate that an investigation of the dispersion of aerosol particles in the spirit of ensemble forecast contains useful hints for the improvement of risk assessment.

Haszpra, T.; Lagzi, I.; Tél, T.

2013-10-01

210

Impacts of the January 2005 solar particle events on middle atmospheric chlorine species  

NASA Astrophysics Data System (ADS)

It is well established that solar particle events (SPEs) are sources of significant chemical dis-turbances in the Earth's polar atmosphere. The observed SPE effects on nitrogen, hydrogen and oxygen compounds have been investigated in some detail in recent years, and they can be reproduced by atmospheric models using basic parametrizations for NOx and HOx produc-tion as a funtion of the particle impact ionisation. However, there are considerable differences between model predictions and measurements concerning several other trace gases including chlorine species. Two major SPEs occurred on January 17, and January 20, 2005. The latter had an exceptionally hard energy spectrum which caused maximum particle impact ionization at stratospheric altitudes. The Microwave Limb Sounder (MLS) instrument on-board the Aura satellite has measured a short-term decrease of HCl in the northern polar region corresponding to January 2005 SPEs. The peak HCl depletion is ˜300 ppt at 35-40 km. This is comparable to the depletion of messopheric HCl observed by the HALOE instrument during the July 2000 SPE. We will present simulation results of the University of Bremen Ion Chemistry (UBIC) model for the SPEs in January 2005 focusing on chlorine species. The simulations indicate that the observed short-term decrease of middle atmospheric HCl is due to a conversion into active chlorine species such as Cl, ClO and HOCl. The magnitude of the observed HCl loss can only be reproduced if reactions of negative chlorine species and the production of O(1 D) from the reaction N(2 D) + O2 are taken into account. The model results will be compared to MLS/Aura data of HCl, HOCl and ClO. Additionally, the impacts of the observed chlorine activation, e.g. on ozone, will be assessed.

Winkler, Holger; Sinnhuber, Miriam; Notholt, Justus; Maik Wissing, Jan; Kallenrode, May-Britt; Santee, Michelle

211

Relationship Between Particle and Plasma Properties and Coating Characteristics of Samaria-Doped Ceria Prepared by Atmospheric Plasma Spraying for Use in Solid Oxide Fuel Cells  

NASA Astrophysics Data System (ADS)

Samaria-doped ceria (SDC) has become a promising material for the fabrication of high-performance, intermediate-temperature solid oxide fuel cells (SOFCs). In this study, the in-flight characteristics, such as particle velocity and surface temperature, of spray-dried SDC agglomerates were measured and correlated to the resulting microstructures of SDC coatings fabricated using atmospheric plasma spraying, a manufacturing technique with the capability of producing full cells in minutes. Plasmas containing argon, nitrogen and hydrogen led to particle surface temperatures higher than those in plasmas containing only argon and nitrogen. A threshold temperature for the successful deposition of SDC on porous stainless steel substrates was calculated to be 2570 °C. Coating porosity was found to be linked to average particle temperature, suggesting that plasma conditions leading to lower particle temperatures may be most suitable for fabricating porous SOFC electrode layers.

Cuglietta, Mark; Kesler, Olivera

2012-06-01

212

The Landes experiment: Biosphere-atmosphere exchanges of ozone and aerosol particles above a pine forest  

SciTech Connect

An experiment to measure the transfer of trace gases in the lower atmosphere was performed in the forested area of {open_quotes} Les Landes {close_quotes} in southwestern France. This region is one of the largest remaining forests in western Europe, and consists predominantly of resinous trees (maritime pines). This experiment involved emission measurements of chemically reactive species, measurement methodologies, mechanisms for flux and the influence of these emissions on boundary layer chemistry. This paper presents preliminary results on the dry deposition of ozone and aerosol particles in the boundary layer. 28 refs., 15 figs.

Lamaud, E.; Labatut, A.; Lopez, A.; Fontan, J.; Druilhet, A. [Universite Paul Sabatier, Toulouse (France); Brunet, Y. [Institut National de la Recherche Agronomique, Villenave d`Ornon (France)

1994-08-20

213

Gas\\/particle partitioning of currently used pesticides in the atmosphere of Strasbourg (France)  

Microsoft Academic Search

Atmospheric particle (P) and gas (G) phase samples have been collected in Strasbourg (Northeast of France) using a high-volume\\u000a sampler equipped with a filter-XAD-2 resin plug between April 17 and May 29, 2007. Seventy-one currently used pesticides were\\u000a monitored in these samples, and 38 of them were detected at concentrations ranging from 0.07 ng\\/m3 for fenarimol to 40.30 ng\\/m3 for deltamethrin in

Claude Schummer; Elodie Mothiron; Brice M. R. Appenzeller; Robert Wennig; Maurice Millet

2010-01-01

214

Organic acids in different size classes of atmospheric particulate material  

NASA Astrophysics Data System (ADS)

During fall and winter 1986-87, aerosol samples were collected with a 5-stage impactor in an urban, a suburban and a rural area in Central Europe. The weak acid content of aerosol particles was characterized by buffer capacity titrations, and organic acids were determined. C4-C6 dicarboxylic acids were found to be the main constituents of aerosol organic acids, with the highest concentrations occurring during a winter-time smog period. Size distributions of single species showed a maximum in the accumulation mode, indicating that these compounds have gaseous precursors. It is suggested that these precursors are of anthropogenic origin.

Ludwig, J.; Klemm, O.

1988-11-01

215

Production, growth and properties of ultrafine atmospheric aerosol particles in an urban environment  

NASA Astrophysics Data System (ADS)

Number concentrations of atmospheric aerosol particles were measured by a flow-switching type differential mobility particle sizer in an electrical mobility diameter range of 6-1000 nm in 30 channels near central Budapest with a time resolution of 10 min continuously from 3 November 2008 to 2 November 2009. Daily median number concentrations of particles varied from 3.8 × 103 to 29 ×103 cm-3 with a yearly median of 11.8 × 103 cm-3. Contribution of ultrafine particles to the total particle number ranged from 58 to 92% with a mean ratio and standard deviation of (79 ± 6)%. Typical diurnal variation of the particle number concentration was related to the major emission patterns in cities, new particle formation, sinks of particles and meteorology. Shapes of the monthly mean number size distributions were similar to each other. Overall mean for the number median mobility diameter of the Aitken and accumulation modes were 26 and 93 nm, respectively, which are substantially smaller than for rural or background environments. The Aitken and accumulation modes contributed similarly to the total particle number concentrations at the actual measurement location. New particle formation and growth unambiguously occurred on 83 days, which represent 27% of all relevant days. Hence, new particle formation and growth are not rare phenomena in Budapest. Their frequency showed an apparent seasonal variation with a minimum of 7.3% in winter and a maximum of 44% in spring. New particle formation events were linked to increased gas-phase H2SO4 concentrations. In the studied area, new particle formation is mainly affected by condensation sink and solar radiation. The formation process seems to be not sensitive to SO2, which was present in a yearly median concentration of 6.7 ?g m-3. This suggests that the precursor gas was always available in excess. Formation rate of particles with a diameter of 6 nm varied between 1.65 and 12.5 cm-3 s-1 with a mean and standard deviation of (4.2 ± 2.5) cm-3 s-1. Seasonal dependency for the formation rate could not be identified. Growth curves of nucleated particles were usually superimposed on the characteristic diurnal pattern of road traffic direct emissions. The growth rate of the nucleation mode with a median diameter of 6 nm varied from 2.0 to 13.3 nm h-1 with a mean and standard deviation of (7.7 ± 2.4) nm h-1. There was an indicative tendency for larger growth rates in summer and for smaller values in winter. New particle formation events increased the total number concentration by a mean factor and standard deviation of 2.3 ± 1.1 relative to the concentration that occurred immediately before the event. Several indirect evidences suggest that the new particle formation events occurred at least over the whole city, and were of regional type. The results and conclusions presented are the first information of this kind for the region over one-year long time period.

Salma, I.; Borsós, T.; Weidinger, T.; Aalto, P.; Hussein, T.; Dal Maso, M.; Kulmala, M.

2011-02-01

216

Influence of humidity, sunlight, and temperature on the daytime decay of polyaromatic hydrocarbons on atmospheric soot particles  

Microsoft Academic Search

In this paper we have attempted to quantify the loss of polyaromatic hydrocarbons (PAH) on atmospheric soot particles with respect to the effects of humidity, solar radiation, and temperature. Dilute residential wood smoke and internal gasoline combustion emissions were individually aged in the presence of natural sunlight in 25-m³ outdoor Teflon film chambers. Soot particles were collected on filters and

Richard M. Kamens; Zhishi Guo; J. N. Fuicher; Douglas A. Bell

1988-01-01

217

Nanostructured Materials Synthesis Using Hypersonic Plasma Particle Deposition  

NASA Astrophysics Data System (ADS)

We (Work performed with P. H. McMurry, J. V. R. Heberlein, N. Rao and H. J. Lee) report a new deposition process in which ultrafine particles nucleate in a thermal plasma undergoing a supersonic expansion and are deposited on a substrate by hypersonic impaction. The objective of this process is to produce nanostructured material at high rates without having to collect and process a loose powder. Preliminary experiments in which silicon was synthesized by injecting vapor-phase silicon tetrachloride into an argon-hydrogen plasma produced in 20 minutes a deposit measuring approximately 1.3 mm thick and 5 mm in diameter, for a linear growth rate of about 1 um/s. In these experiments the plasma was generated by a DC torch operating at 200 A and 40 V. Flow rates were: argon, 35 slm; hydrogen, 4 slm; and SiCl_4, 0.2 slm. In previous experiments with similar operating conditions footnote N Rao, B. Micheel, D. Hansen, C. Fandrey, M. Bench, S. Girshick, J. Heberlein and P. McMurry, J. Mater. Res. 10, 2973 (1995); N. Rao, S. Girshick, J. Heberlein, P. McMurry, S. Jones, D. Hansen and B. Micheel, Plasma Chem. Plasma Process. 15, 581 (1995), the expansion of this mixture through a converging nozzle produced a silicon aerosol with a number-mean particle diameter of about 10 nm. In the present experiments the boron nitride nozzle was lengthened from 5 mm to 10 mm. The pressure was 66 kPa (500 torr) upstream of the nozzle and 0.3 kPa (2.5 torr) in the deposition chamber, driving a hypersonic flow which is capable of depositing particles down to about 3 nm in diameter by inertial impaction. The particle deposition process was recorded by a telemicroscope video camera, and deposits were characterized by scanning electron microscopy, x-ray diffraction, atomic force microscopy, and energy-dispersive x-ray analysis. The grain size of the deposit is expected to depend on substrate temperature, an effect which we are presently studying.

Girshick, Steven L.

1996-10-01

218

Special Issue for the 9th International Conference on Carbonaceous Particles in the Atmosphere  

SciTech Connect

Carbonaceous particles are a minor constituent of the atmosphere but have a profound effect on air quality, human health, visibility and climate. The importance of carbonaceous particles has been increasingly recognized and become a mainstream topic at numerous conferences. Such was not the case in 1978, when the 1st International Conference on Carbonaceous Particles in the Atmosphere (ICCPA), or ''Carbon Conference'' as it is widely known, was introduced as a new forum to bring together scientists who were just beginning to reveal the importance and complexity of carbonaceous particles in the environment. Table 1 lists the conference dates, venues in the series as well as the proceedings, and special issues resulting form the meetings. Penner and Novakov (Penner and Novakov, 1996) provide an excellent historical perspective to the early ICCPA Conferences. Thirty years later, the ninth in this conference series was held at its inception site, Berkeley, California, attended by 160 scientists from 31 countries, and featuring both new and old themes in 49 oral and 83 poster presentations. Topics covered such areas as historical trends in black carbon aerosol, ambient concentrations, analytic techniques, secondary aerosol formation, biogenic, biomass, and HULIS1 characterization, optical properties, and regional and global climate effects. The conference website, http://iccpa.lbl.gov/, holds the agenda, as well as many presentations, for the 9th ICCPA. The 10th ICCPA is tentatively scheduled for 2011 in Vienna, Austria. The papers in this issue are representative of several of the themes discussed in the conference. Ban-Weiss et al., (Ban-Weiss et al., accepted) measured the abundance of ultrafine particles in a traffic tunnel and found that heavy duty diesel trucks emit at least an order of magnitude more ultrafine particles than light duty gas-powered vehicles per unit of fuel burned. Understanding of this issue is important as ultrafine particles have been shown to adversely affect human health (Lighty et al., 2000; Pope and Dockery, 2006). Gan et al. (Gan et al., accepted) examined the indoor air quality aboard submarines and found that the diesel particulate matter concentrations exceeded the EPA 24 hour standard. Claeys et al. (Claeys et al., accepted) studied the importance and sources of secondary organic aerosol (SOA) in remote marine environment during a period of high biological activity. Methanesulphonate was the major SOA compound detected and there was no evidence for SOA from isoprene. The optical properties of gasoline and diesel vehicle particulate emissions and their relative contribution to radiative forcing was studied by Strawa et al. (Strawa et al., accepted).

Strawa, A.W.; Kirchstetter, T.W.; Puxbaum, H.

2009-12-11

219

?-Scale Variations Of Elemental Composition In Individual Atmospheric Particles By Means Of Synchrotron Radiation Based ?-XRF Analysis  

NASA Astrophysics Data System (ADS)

Atmospheric pollution poses a huge challenge especially for densely populated urban areas. Although a tremendous knowledge already exists on atmospheric particulate pollution, only very limited knowledge is available on mineral and chemical composition of single atmospheric particles because most studies on air pollution focus on total mass concentrations or bulk elemental analysis. However, it is of particular importance to investigate the properties of single particles since according to their individually composition they differ in their specific impact on climate change, negative environment and health effects, as well as accelerating the weathering of stone buildings in urban areas. Particles with sulfate and nitrate coatings together with sufficient moisture increase metal solubility and possibly catalyze further surface reactions on stone facades of buildings. From the viewpoint of health effects of aerosols it is important to consider agglomerations processes of fine anthropogenic and highly toxic particles with coarse geogenic and less toxic particles. With respect to fundamental research in mineralogy, processes forming composed coarse particles consisting of geogenic and anthropogenic substances are valuable to study since a new type of particle is produced. In this context, the important and still in detail unknown role of geogenic particles as catchers for anthropogenic aerosols can be investigated more closely. Coarse particles can provide a possible sink for fine particles. Moreover, the intermixture of particles from geogenic and anthropogenic sources and the spatial and temporal variations of contributions from different sources, which plays a decisive role in the study area of Beijing, can be clarified with this approach. For this study, particles were collected with the passive sampling device Sigma-2 and analyzed for particles from 3 to 96 ?m. The analyzed particles showed a very inhomogeneous distribution in their elemental composition. For this study, synchrotron radiation based ?-X-ray fluorescence analysis (?-SXRF) proved to be an excellent tool to investigate ?-scalic distributions of main and trace element concentrations within individual airborne particles.

Schleicher, N.; Kramar, U.; Norra, S.; Dietze, V.; Kaminski, U.; Cen, K.; Yu, Y.

2010-04-01

220

Effects of atmospheric pressure on DC resistance to tracking of polymer insulating materials  

Microsoft Academic Search

Polymer insulating materials are required for use in high altitude regions. For the use of polymer insulating materials in such regions, it must be confirmed whether the resistance to tracking at high altitudes is different from that at altitudes near the sea level. In this paper, an artificial atmospheric chamber was set up to investigate the resistance to tracking on

B. X. Du; Y. Yamano

2005-01-01

221

Low-temperature and low atmospheric pressure infrared reflectance spectroscopy of Mars soil analog materials  

Microsoft Academic Search

Infrared reflectance spectra of carefully selected Mars soil analog materials have been measured under low atmospheric pressures and temperatures. Chemically altered montmorillonites containing ferrihydrite and hydrated ferric sulfate complexes are examined, as well as synthetic ferrihydrite and a palagonitic soil from Haleakala, Maui. Reflectance spectra of these analog materials exhibit subtle visible to near-infrared features, which are indicative of nanophase

Janice L. Bishop; Carlé M. Pieters

1995-01-01

222

Low-temperature and low atmospheric pressure infrared reflectance spectroscopy of Mars soil analog materials  

Microsoft Academic Search

Infrared reflectance spectra of carefully selected Mars soil analog materials have been measured under low atmospheric pressures and temperatures. Chemically altered montmorillonites containing ferrihydrite and hydrated ferric sulfate complexes are examined, as well as synthetic ferrihydrate and a palagonitic soil from Haleakala, Maui. Reflectance spectra of these analog materials exhibit subtle visible to near-infrared features, which are indicative of nanophase

Janice L. Bishop; Carle M. Pieters

1995-01-01

223

Carbohydrate-like composition of submicron atmospheric particles and their production from ocean bubble bursting  

PubMed Central

Oceans cover over two-thirds of the Earth’s surface, and the particles emitted to the atmosphere by waves breaking on sea surfaces provide an important contribution to the planetary albedo. During the International Chemistry Experiment in the Arctic LOwer Troposphere (ICEALOT) cruise on the R/V Knorr in March and April of 2008, organic mass accounted for 15–47% of the submicron particle mass in the air masses sampled over the North Atlantic and Arctic Oceans. A majority of this organic component (0.1 - 0.4 ? m-3) consisted of organic hydroxyl (including polyol and other alcohol) groups characteristic of saccharides, similar to biogenic carbohydrates found in seawater. The large fraction of organic hydroxyl groups measured during ICEALOT in submicron atmospheric aerosol exceeded those measured in most previous campaigns but were similar to particles in marine air masses in the open ocean (Southeast Pacific Ocean) and coastal sites at northern Alaska (Barrow) and northeastern North America (Appledore Island and Chebogue Point). The ocean-derived organic hydroxyl mass concentration during ICEALOT correlated strongly to submicron Na concentration and wind speed. The observed submicron particle ratios of marine organic mass to Na were enriched by factors of ?102–?103 over reported sea surface organic to Na ratios, suggesting that the surface-controlled process of film bursting is influenced by the dissolved organic components present in the sea surface microlayer. Both marine organic components and Na increased with increasing number mean diameter of the accumulation mode, suggesting a possible link between organic components in the ocean surface and aerosol–cloud interactions.

Russell, Lynn M.; Hawkins, Lelia N.; Frossard, Amanda A.; Quinn, Patricia K.; Bates, Tim S.

2010-01-01

224

Formation and ultrasonic removal of fouling particle structures in a natural porous material  

Microsoft Academic Search

Formation and ultrasonic removal of fouling particle structures in a porous material (caused by the flow of a liquid with small through the material) was studied with natural sandstone. Fouling particles were generated inside the sandstone by changing the composition of the liquid from a 2% KCl brine solution to fresh water. The influence of liquid velocity, particle concentration and

Pietro Poesio; Gijs Ooms

2004-01-01

225

Molecular understanding of atmospheric particle formation from sulfuric acid and large oxidized organic molecules.  

PubMed

Atmospheric aerosols formed by nucleation of vapors affect radiative forcing and therefore climate. However, the underlying mechanisms of nucleation remain unclear, particularly the involvement of organic compounds. Here, we present high-resolution mass spectra of ion clusters observed during new particle formation experiments performed at the Cosmics Leaving Outdoor Droplets chamber at the European Organization for Nuclear Research. The experiments involved sulfuric acid vapor and different stabilizing species, including ammonia and dimethylamine, as well as oxidation products of pinanediol, a surrogate for organic vapors formed from monoterpenes. A striking resemblance is revealed between the mass spectra from the chamber experiments with oxidized organics and ambient data obtained during new particle formation events at the Hyytiälä boreal forest research station. We observe that large oxidized organic compounds, arising from the oxidation of monoterpenes, cluster directly with single sulfuric acid molecules and then form growing clusters of one to three sulfuric acid molecules plus one to four oxidized organics. Most of these organic compounds retain 10 carbon atoms, and some of them are remarkably highly oxidized (oxygen-to-carbon ratios up to 1.2). The average degree of oxygenation of the organic compounds decreases while the clusters are growing. Our measurements therefore connect oxidized organics directly, and in detail, with the very first steps of new particle formation and their growth between 1 and 2 nm in a controlled environment. Thus, they confirm that oxidized organics are involved in both the formation and growth of particles under ambient conditions. PMID:24101502

Schobesberger, Siegfried; Junninen, Heikki; Bianchi, Federico; Lönn, Gustaf; Ehn, Mikael; Lehtipalo, Katrianne; Dommen, Josef; Ehrhart, Sebastian; Ortega, Ismael K; Franchin, Alessandro; Nieminen, Tuomo; Riccobono, Francesco; Hutterli, Manuel; Duplissy, Jonathan; Almeida, João; Amorim, Antonio; Breitenlechner, Martin; Downard, Andrew J; Dunne, Eimear M; Flagan, Richard C; Kajos, Maija; Keskinen, Helmi; Kirkby, Jasper; Kupc, Agnieszka; Kürten, Andreas; Kurtén, Theo; Laaksonen, Ari; Mathot, Serge; Onnela, Antti; Praplan, Arnaud P; Rondo, Linda; Santos, Filipe D; Schallhart, Simon; Schnitzhofer, Ralf; Sipilä, Mikko; Tomé, António; Tsagkogeorgas, Georgios; Vehkamäki, Hanna; Wimmer, Daniela; Baltensperger, Urs; Carslaw, Kenneth S; Curtius, Joachim; Hansel, Armin; Petäjä, Tuukka; Kulmala, Markku; Donahue, Neil M; Worsnop, Douglas R

2013-10-07

226

Preliminary studies on the source of PM10 aerosol particles in the atmosphere of Shanghai City by analyzing single aerosol particles  

NASA Astrophysics Data System (ADS)

To identify the origin of PM10 (particulate matter with aerodynamic diameter equal to or less than 10 ?m) in the atmosphere of Shanghai City, single PM10 particles from two environmental monitor locations and six pollution emitter sources were measured by scanning nuclear microprobe techniques. Every PM10 particle is characterized by its micro-PIXE spectrum. The strategy of micro-PIXE spectra combined with the pattern recognition technique is applied to identify original sources of measured PM10 particles. The results of this investigation show that the most of the measured PM10 particles are derived from building construction sites, cement factories, vehicle exhaust, coal boilers and steel mills.

Li, X.; Zhu, J.; Guo, P.; Wang, J.; Qiu, Z.; Lu, R.; Qiu, H.; Li, M.; Jiang, D.; Li, Y.; Zhang, G.

2003-09-01

227

Evaluation of the atmospheric transport of marine-derived particles using long-chain unsaturated ketones  

SciTech Connect

Biomarker source information provided by long-chain alkenone (LCA) distribution patterns was used to assess the transport pathways of marine aerosols. The C{sub 37}-C{sub 39}LCA were found in significant amounts in aerosols collected in New Zealand. Their occurrence in the atmosphere stems from their introduction by bubble-bursting processes during wave breaking. The surface water temperatures calculated from the U{sub 37}{sup k} ratios suggested a local origin and short atmospheric residence times of the LCA. They were not detected in aerosol samples collected on American Samoa due to the absence of the source organisms in surface waters. The distribution of LCA was also investigated in size-fractionated aerosols over a range of < 0.5 to > 7.2 {mu}m equivalent diameter. Their distribution over the size spectrum demonstrated that they were only associated with large particles (d{sub eq} > 3.0 {mu}m), suggesting a direct injection of algal cells and/or their fragments into the atmosphere.

Sicre, M.A.; Gagosian, R.B.; Peltzer, E.T. (Woods Hole Oceanographic Institution, MA (United States))

1990-02-20

228

Temperature of particles heated in a fluidized bed of inert material  

NASA Astrophysics Data System (ADS)

The authors give formulas for calculating the heat- and mass-transfer coefficients for particles with a fluidized bed of inert material. A method is given for determining the temperature of the hot particle.

Baskakov, A. P.; Filippovskii, N. F.; Munts, V. A.; Ashikhmin, A. A.

1987-05-01

229

Atmosphere  

NSDL National Science Digital Library

What is this atmosphere that surrounds the Earth? This instructional tutorial, part of an interactive laboratory series for grades 8-12, introduces students to the structure, effects, and components of the atmosphere. Here students investigate the composition of the atmosphere; effects of temperature, pressure, and ozone; the greenhouse effect; and how Earth compares with other planets. Interactive activities present students with opportunities to explore ideas and answer questions about the atmosphere, including its structure, the making of ozone, rocket launching, and measuring the atmosphere. Pop-up boxes provide additional information on topics such as dust, rain, and atmospheric composition. Students complete a final written review of six questions about the atmosphere. Copyright 2005 Eisenhower National Clearinghouse

University of Utah. Astrophysics Science Project Integrating Research and Education (ASPIRE)

2003-01-01

230

Hygroscopic properties of smoke-generated organic aerosol particles emitted in the marine atmosphere  

NASA Astrophysics Data System (ADS)

During the Eastern Pacific Emitted Aerosol Cloud Experiment (E-PEACE), a plume of organic aerosol was produced by a smoke generator and emitted into the marine atmosphere from aboard the R/V Point Sur. In this study, the hygroscopic properties and the chemical composition of the plume were studied at plume ages between 0 and 4 h in different meteorological conditions. In sunny conditions, the plume particles had very low hygroscopic growth factors (GFs): between 1.05 and 1.09 for 30 nm and between 1.02 and 1.1 for 150 nm dry size at a relative humidity (RH) of 92%, contrasted by an average marine background GF of 1.6. New particles were produced in large quantities (several 10 000 cm-3), which lead to substantially increased cloud condensation nuclei (CCN) concentrations at supersaturations between 0.07 and 0.88%. Ratios of oxygen to carbon (O : C) and water-soluble organic mass (WSOM) increased with plume age: from < 0.001 to 0.2, and from 2.42 to 4.96 ?g m-3, respectively, while organic mass fractions decreased slightly (~ 0.97 to ~ 0.94). High-resolution aerosol mass spectrometer (AMS) spectra show that the organic fragment m/z 43 was dominated by C2H3O+ in the small, new particle mode and by C3H7+ in the large particle mode. In the marine background aerosol, GFs for 150 nm particles at 40% RH were found to be enhanced at higher organic mass fractions: an average GF of 1.06 was observed for aerosols with an organic mass fraction of 0.53, and a GF of 1.04 for an organic mass fraction of 0.35.

Wonaschütz, A.; Coggon, M.; Sorooshian, A.; Modini, R.; Frossard, A. A.; Ahlm, L.; Mülmenstädt, J.; Roberts, G. C.; Russell, L. M.; Dey, S.; Brechtel, F. J.; Seinfeld, J. H.

2013-10-01

231

Characterization of spatial impact of particles emitted from a cement material production facility on outdoor particle deposition in the surrounding community.  

PubMed

The objective of this study was to estimate the contribution of a facility that processes steel production slag into raw material for cement production to local outdoor particle deposition in Camden, NJ. A dry deposition sampler that can house four 37-mm quartz fiber filters was developed and used for the collection of atmospheric particle deposits. Two rounds of particle collection (3-4 weeks each) were conducted in 8-11 locations 200-800 m downwind of the facility. Background samples were concurrently collected in a remote area located -2 km upwind from the facility. In addition, duplicate surface wipe samples were collected side-by-side from each of the 13 locations within the same sampling area during the first deposition sampling period. One composite source material sample was also collected from a pile stored in the facility. Both the bulk of the source material and the < 38 microm fraction subsample were analyzed to obtain the elemental source profile. The particle deposition flux in the study area was higher (24-83 mg/m2 x day) than at the background sites (13-17 mg/m2day). The concentration of Ca, a major element in the cement source production material, was found to exponentially decrease with increasing downwind distance from the facility (P < 0.05). The ratio of Ca/Al, an indicator of Ca enrichment due to anthropogenic sources in a given sample, showed a similar trend. These observations suggest a significant contribution of the facility to the local particle deposition. The contribution of the facility to outdoor deposited particle mass was further estimated by three independent models using the measurements obtained from this study. The estimated contributions to particle deposition in the study area were 1.8-7.4% from the regression analysis of the Ca concentration in particle deposition samples against the distance from the facility, 0-11% from the U.S. Environmental Protection Agency (EPA) Chemical Mass Balance (CMB) source-receptor model, and 7.6-13% from the EPA Industrial Source Complex Short Term (ISCST3) dispersion model using the particle-size-adjusted permit-based emissions estimates. PMID:22070034

Yu, Chang Ho; Fan, Zhihua; McCandlish, Elizabeth; Stern, Alan H; Lioy, Paul J

2011-10-01

232

Basic properties of specific wood-based materials carbonised in a nitrogen atmosphere  

Microsoft Academic Search

The purpose of this study is to develop new porous carbon materials by carbonising wood-based materials. One of the advantages of wood-based materials used as precursors for porous carbon materials is the simple and cost-effective production technique. Moreover, it is possible to make adjustments for a wide range of macro- and micro-structures by selecting different densities and particle sizes. Compared

O. Treusch; A. Hofenauer; F. Tröger; J. Fromm; G. Wegener

2004-01-01

233

Femtosecond Laser Ablation Particle Introduction to a Liquid Sampling-Atmospheric Pressure Glow Discharge Ionization Source  

SciTech Connect

This work describes the use of a compact, liquid sampling – atmospheric pressure glow discharge (LS-APGD) ionization source to ionize metal particles within a laser ablation aerosol. Mass analysis was performed with a Thermo Scientific Exactive Mass Spectrometer which utilizes an orbitrap mass analyzer capable of producing mass resolution exceeding M/?M > 160,000. The LS-APGD source generates a low-power plasma between the surface of an electrolytic solution flowing at several µl min-1 through a fused silica capillary and a counter electrode consisting of a stainless steel capillary employed to deliver the laser ablation particles into the plasma. Sample particles of approximately 100 nm were generated with an Applied Spectra femtosecond laser located remotely and transported through 25 meters of polyurethane tubing by means of argon carrier gas. Samples consisted of an oxygen free copper shard, a disk of solder, and a one-cent U.S. coin. Analyte signal onset was readily detectable relative to the background signal produced by the carrier gas alone. The high mass resolution capability of the orbitrap mass spectrometer was demonstrated on the solder sample with resolution exceeding 90,000 for Pb and 160,000 for Cu. In addition, results from a laser ablation depth-profiling experiment of a one cent coin revealed retention of the relative locations of the ~10 µm copper cladding and zinc rich bulk layers.

Carado, Anthony J.; Quarles, C. Derrick; Duffin, Andrew M.; Barinaga, Charles J.; Russo, Richard; Marcus, R. Kenneth; Eiden, Gregory C.; Koppenaal, David W.

2012-01-16

234

SiC particle cracking in powder metallurgy processed aluminum matrix composite materials  

Microsoft Academic Search

Particle cracking is one of the key elements in the fracture process of particulate-reinforced metal-matrix composite (MMC)\\u000a materials. The present study quantitatively examined the amount of new surface area created by particle cracking and the number\\u000a fraction of cracked particles in a series of SiC-reinforced aluminum-matrix composite materials. These composite materials\\u000a were fabricated by liquid-phase sintering and contained 9 vol

B. Wang; G. M. Janowski; B. R. Patterson

1995-01-01

235

Production, growth and properties of ultrafine atmospheric aerosol particles in an urban environment  

NASA Astrophysics Data System (ADS)

Number concentrations of atmospheric aerosol particles were measured by a flow-switching type differential mobility particle sizer in an electrical mobility diameter range of 6-1000 nm in 30 channels near central Budapest with a time resolution of 10 min continuously from 3 November 2008 to 2 November 2009. Daily median number concentrations of particles varied from 3.8×103 to 29×103 cm-3 with a yearly median of 11.8×103 cm-3. Contribution of ultrafine particles to the total particle number ranged from 58 to 92% with a mean ratio and standard deviation of (79±6)%. Daily average number concentrations in various size fractions and contribution of ultrafine particles to the total particle number showed no seasonal dependency. Monthly mean number size distributions were similar to each other. Overall mean for the number median mobility diameter of the Aitken and accumulation modes were 26 and 93 nm, respectively, which are substantially smaller than for rural or background environments. The Aitken and accumulation modes contributed similarly to the total particle number concentrations at the actual measurement location. Median diameters of the Aitken and accumulation modes were shifted to larger values before nucleation started and over the growth process, which can be related to the presence of aged aerosol under the conditions that favour nucleation and growth. Particle concentrations were usually increased substantially after nucleations. Overall mean and standard deviation of the nucleation mode number concentrations were (10.4±2.8)×103 cm-3. Mean ratio and standard deviation of the nucleation mode number concentration to the total particle number concentration that was averaged for two hours just before the formation was detected was 2.3±1.1. Nucleation unambiguously occurred on 83 days, which represent 27% of all relevant days. Its frequency showed a remarkable seasonal variation with a minimum of 7.3% in winter and a maximum of 44% in spring. Formation rate of particles with a diameter of 6 nm varied between 1.65 and 12.5 cm-3 s-1 with a mean and standard deviation of (4.2±2.5) cm-3 s-1. Seasonal dependency for the formation rate could not be identified. Growth curves of nucleated particles were usually superimposed on the characteristic diurnal pattern of road traffic direct emissions. The growth rate of the nucleation mode with a median diameter of 6 nm varied from 2.0 to 13.3 nm h-1 with a mean and standard deviation of (7.7±2.4) nm h-1. There was an indicative tendency for larger growth rates in summer and for smaller values in winter. Several indirect evidences suggest that the nucleation events occurred at least over the whole city, and were of regional type.

Salma, I.; Borsós, T.; Weidinger, T.; Aalto, P.; Hussein, T.; Dal Maso, M.; Kulmala, M.

2010-06-01

236

Simulated atmospheric processing of iron oxyhydroxide minerals at low pH: Roles of particle size and acid anion in iron dissolution  

PubMed Central

A number of recent studies have shown that iron dissolution in Fe-containing dust aerosol can be linked to source material (mineral or anthropogenic), mineralogy, and iron speciation. All of these factors need to be incorporated into atmospheric chemistry models if these models are to accurately predict the impact of Fe-containing dusts into open ocean waters. In this report, we combine dissolution measurements along with spectroscopy and microscopy to focus on nanoscale size effects in the dissolution of Fe-containing minerals in low-pH environments and the importance of acid type, including HNO3, H2SO4, and HCl, on dissolution. All of these acids are present in the atmosphere, and dust particles have been shown to be associated with nitrate, sulfate, and/or chloride. These measurements are done under light and dark conditions so as to simulate and distinguish between daytime and nighttime atmospheric chemical processing. Both size (nano- versus micron-sized particles) and anion (nitrate, sulfate, and chloride) are found to play significant roles in the dissolution of ?-FeOOH under both light and dark conditions. The current study highlights these important, yet unconsidered, factors in the atmospheric processing of iron-containing mineral dust aerosol.

Rubasinghege, Gayan; Lentz, Robert W.; Scherer, Michelle M.; Grassian, Vicki H.

2010-01-01

237

Probing Heterogeneous Chemistry of Individual Atmospheric Particles Using Scanning Electron Microscopy and Energy-Dispersive X-ray Analysis  

SciTech Connect

In this paper, we demonstrate the utility of single-particle analysis to investigate the chemistry of isolated, individual particles of atmospheric relevance such as NaCl, sea salt, CaCO3, and SiO2. A variety of state-of-th-art scanning electron microscopy techniques, including environmental scanning electon microscopy and computer-controlled scanning electron microscopy/energy-dispersive X-ray analysis, were utilized for monitoring and quantifying phase transitions of individual particles, morphology, and compositional changes of individual particles as they react with nitric acid.

Krueger, Brenda J.; Grassian, Vicki H.; Iedema, Martin J.; Cowin, James P.; Laskin, Alexander

2003-10-01

238

Particle-size segregation of granular materials under shear  

NASA Astrophysics Data System (ADS)

Particle size segregation in avalanches occurs through shearing within the granular flow. In such a flow, large particles migrate upwards, their vacated spaces being filled by smaller particles. The Gray-Thornton continuum model is a scalar conservation law in two space variables and time, but with variable coefficients corresponding to the spatially dependent velocity in shear flow. Sharp interfaces separating different mixtures are shock wave solutions that typically form in finite time from smooth initial conditions. Shocks with more large particles below small are physically unstable, leading to time-dependent multidimensional patterns. An experiment in a Couette shear cell exhibits mixing and segregation predicted by theoretical solutions.

Shearer, Michael; May, Lindsay; Giffen, Nick; Daniels, Karen

2009-11-01

239

Atmospheric Ions: Chemical Composition, Diurnal Variation, and Insights into New Particle Formation  

NASA Astrophysics Data System (ADS)

Ions in the atmosphere are mainly produced by cosmic radiation (CR) and radioactive decay of radon. To a first approximation, when an ion collides with a neutral molecule, the charge will be transferred if energetically favorable. Typical lifetimes of ions are on the order of several minutes, giving the ions time to reach a pseudo steady state with most of the negative charges on the strongest acids (e.g. sulfuric, nitric, malonic acid), and the positive charges on the strongest bases (e.g. ammonia, amines, pyridines, quinolines), although these species may only be present in trace amounts. This feature makes the analysis of the ambient ions particularly interesting, as sulfuric acid, amines and organic acids are often mentioned as precursors for new atmospheric new particle formation. In this study, a recently developed high-resolution mass spectrometer (APi-TOF) has been deployed in spring at the SMEAR II station in Hyytiälä, Finland. The chemical composition and temporal behavior of both ambient negative and positive ions were measured with higher sensitivity and mass resolution than in previous studies. Several new molecules and clusters were identified, utilizing the high mass accuracy and the time behavior of the ion peaks. The negative ion spectrum is dominated by highly oxygenated species, both inorganic and organic, consistent with by photo-chemical production, leading to strong diurnal cycles. At high H2SO4 concentrations, HSO4- and its clusters with one and two neutral H2SO4 molecules dominate the negative ion spectrum. These periods occur simultaneously with new particle formation events in Hyytiälä, suggesting that the sulfuric acid clusters play an important role in the initial formation of new particles. At the highest H2SO4 concentrations, larger H2SO4 clusters contain ammonia and amine molecules. Other peaks, likely organic acids containing sulfate and/or nitrate species, are also observed with distinct diurnal cycles. New results from both ambient observations and laboratory experiments will be discussed in relation to understanding chemical composition of cluster formation and new particle formation.

Worsnop, D. R.; Schobesberger, S.; Ehn, M.; Junninen, H.; Sipila, M.; Petaja, T.; Kulmala, M. T.

2011-12-01

240

Comparison of fluid and particle-in-cell simulations on atmospheric pressure helium microdischarges  

NASA Astrophysics Data System (ADS)

Microdischarges at atmospheric pressure were studied by two computational methods. The first method is a typical one-dimensional fluid model in which the electron velocity distribution function is assumed to be Maxwellian and the energy equation is solved to determine the spatial profile of the electron temperature. The second method is a particle-in-cell (PIC) model with Monte-Carlo collisions (MCC). We compared the time-averaged density, electric field and power consumption profiles of helium microdischarges driven at 13.56 MHz and 2.45 GHz obtained with the two models. The agreement between the two models depends on the driving frequency. The kinetic information obtained from the PIC-MCC model indicates that the improved agreement at higher frequency is due to the evolution of the electron energy distribution function from a three-temperature distribution at 13.56 MHz to a close-to-Maxwellian distribution at 2.45 GHz.

Hong, Y. J.; Yoon, M.; Iza, F.; Kim, G. C.; Lee, J. K.

2008-12-01

241

A model for the atmospheric fate of sea salt particles incoastal areas  

NASA Astrophysics Data System (ADS)

Aerosol particles affect climate by scattering and absorbing radiation (Charlson et al., 1992), and may affect the heat budget. Among them, the particles generated at the air-sea interface by wave breaking represent a major component of the natural aerosol (Andreae, 1995). Sea-spray aerosols are mechanically produced by the interaction between wind and wave: when the wind speed increases beyond a critical value, waves break to dissipate the excess of energy. This is accompanied by the occurrence of whitecaps (Monahan and O'Muircheartaigh, 1980) and the primary marine aerosol production is directly related to the whitecap fraction. Air entrained into the water breaks up into bubbles, which may be transported to depths of several meters. When the bubbles rise and reach the surface, they burst and produce two kinds of droplets : film drops and jet drops (Blanchard, 1963; Blanchard, 1983; Resch and Afeti, 1991; Resch and Afeti, 1992). Sea-salts dominate atmospheric deposition in maritime regions (Gustafsson and Franzen, 1996; Farrell et al., 1995). However, the fate of marine aerosol particles in the marine atmosphere is still largely unknown. A model for the aerosol transport in coastal areas is then of great interest for a large number of applications among them, climate change and studies on air and water quality. Tedeschi and Piazzola (2011) presented the development of the Marine Aerosol Concentration Model (MACMod), which is a 2D unsteady model dedicated to the atmospheric transport of marine aerosols in the Marine Atmospheric Boundary Layer. However, such a transport model needs to implement an accurate source term for the sea-salt particles. Uncertainties on the sea-salt source function are still large (see Lewis and Schwartz, 2004). In particular, in coastal areas, the sea-spray production through breaking waves depends on both the fetch and the wind speed conditions. In this study, we propose to improve the MACMod model predictions by introducing an accurate sea-salt source function. To this end, the MACMOD model was implemented in the Mediterranean coast using aerosol data measured during an experimental campaign conducted in the French coastal Mediterranean area in 2008 on board the French oceanographic vessel "Atalante." Using the aerosol size distributions measured in different geographical locations south off the French coastal zone, a new source term has been introduced in MACMOD. The Monahan et al. (1986) formulation, depending both on the aerosol radius and the whitecap fraction, has been revisited. First, a separated approach is used for both the film and jet drops, accounting for the different radius modes. Then, a new sea-state dependent model is used for the whitecap fraction. The simulations were then validated with the help of aerosol size distributions recorded on board the ship "Atalante" for different meteorological conditions.

Demoisson, Ambre; Tedeschi, Gilles; Piazzola, Jacques

2013-04-01

242

Gas-to-Particle Conversion in Surface Discharge Nonthermal Plasmas and Its Implications for Atmospheric Chemistry  

PubMed Central

This paper presents some experimental data on gas-to-particle conversion of benzene using nonthermal plasma (NTP) technology and discusses the possibility of its technical application in atmospheric chemistry. Aerosol measurement using a differential mobility analyzer (DMA) revealed that the parts of benzene molecules were converted into a nanometer-sized aerosol. Aerosol formation was found to be highly related with the missing part in carbon balance. Scanning electron microscopy analysis showed that the aerosols formed in synthetic humid air are the collection of nanoparticles. The carbonyl band (C=O) was found to be an important chemical constituent in the aerosol. The potential of the NTP as an accelerated test tool in studying secondary organic aerosol (SOA) formation from VOCs will be also addressed.

Kim, Hyun-Ha; Ogata, Atsushi

2011-01-01

243

Heterogeneous Combustion Particles with Distinctive Light-Absorbing and Light-Scattering Phases as Mimics of Internally-Mixed Ambient Atmospheric Particles  

NASA Astrophysics Data System (ADS)

Particles with heterogeneously-distributed light-absorbing and light-scattering phases were generated from incomplete combustion or thermal decomposition to mimic real atmospheric particles with distinctive optical properties. Individual particles and particle populations were characterized microscopically. The purpose was to examine how optical property measurements of internally-mixed ambient air particles might vary based on the properties of laboratory-generated particles produced under controlled conditions. The project is an initial stage in producing reference samples for calibrating instrumentation for monitoring climatically-important atmospheric aerosols. Binary-phase particles containing black carbon (BC) and a metal or a metal oxide phase were generated from the thermal decomposition or partial combustion of liquid fuels at a variety of temperatures from 600 °C to 1100 °C. Fuels included mixtures of toluene or isooctane and iron pentacarbonyl or titanium tetrachloride. Scanning electron microscopy with energy-dispersive x-ray spectroscopy revealed that burning the fuels at different temperatures resulted in distinctive differences in morphology and carbon vs. metal/metal oxide composition. Particles from toluene/Fe(CO)5 thermal decomposition exhibited aggregated morphologies that were classified as dendritic, soot-like, globular, or composited (dendritic-globular). Particles from isooctane/TiCl4 combustion were typically spherical with surface adducts or aggregates. Diameters of the BC/TiO2 particles averaged 0.68 ?m to 0.70 ?m. Regardless of combustion temperature, the most abundant particles in each BC/TiO2 sample had an aspect ratio of 1.2. However, for the 600 °C and 900 °C samples the distribution of aspect ratios was skewed toward much larger ratios suggesting significant chainlike aggregation. Carbon and titanium compositions (wt.) for the 600 °C sample were 12 % and 53 %, respectively. In contrast, the composition trended in the opposite direction for the 900 °C sample with carbon at 57 % and titanium at 27 %.

Conny, J. M.; Ma, X.; Gunn, L. R.

2011-12-01

244

Simultaneous measurement of sphericity and scattering phase functions from single atmospheric aerosol particles in Las Cruces, NM  

NASA Astrophysics Data System (ADS)

We report upon the collection of elastic light scattering patterns with high angular resolution and large angular coverage from single atmospheric aerosol particles in Las Cruces, NM. Radiative forcing due to aerosols is a primary source of uncertainty in climate models. Characterization of tropospheric aerosols is carried out by inversion of optical measurements made remotely by land-based instruments and satellites. An integral part of the retrieval procedure is accounting for particle shape (i.e. nonsphericity). In-situ and laboratory measurements of aerosol particles play a critical role in validating and constraining the inversion procedure used in climate models. In this work, we utilize high angular resolution and large angular coverage scattering patterns to simultaneously calculate particle sphericity and the scattering phase of individual atmospheric particles. We examine the relationship between a particle's sphericity and its phase function. In addition, we explore the differences in phase function between nonspherical particles that have high sphericity (i.e. complex particles with overall round shape) and spherical particles. We conclude by commenting on the possible impacts of our findings on inversion procedures used in aerosol characterization.

Martin, Sean; Aptowicz, Kevin; Pan, Yong-Le; Chang, Richard; Pinnick, Ronald

2013-03-01

245

Effects of the Particle Size and the Firing Atmosphere on Electrical Properties in PNN-PZT Thick Films  

Microsoft Academic Search

Pb(Ni \\/3Nb \\/3)O3?PbZrO3?PbTiO3 (PNN-PZT) thick films were screen-printed on platinized alumina substrates and fired at 800–1000°C under PbO atmosphere or in air. Effects of the starting particle size and the firing atmosphere on the microstructure and electrical properties of the thick films were investigated. Attrition milling produced smaller particle size than ball milling. Thick films prepared from attrition-milled powders showed

CHAE IL CHEON; JEONG SEOG KIM; TAE SONG KIM

2004-01-01

246

Risk Assessment Related to Atmospheric Polycyclic Aromatic Hydrocarbons in Gas and Particle Phases near Industrial Sites  

PubMed Central

Background: Inhalation is one of the main means of human exposure to polycyclic aromatic hydrocarbons (PAHs) because of their ubiquitous presence in the atmosphere. However, most studies have considered only PAHs found in the particle phase and have omitted the contribution of the gas-phase PAHs to the risk. Objective: We estimated the lifetime lung cancer risk from PAH exposure by inhalation in people living next to the largest chemical site in Southern Europe and the Mediterranean area. Methods: We determined 18 PAHs in the atmospheric gas and particle phase. We monitored the PAHs for 1 year in three locations near the chemical site in different seasons. We used toxic equivalence factors to calculate benzo[a]pyrene (BaP) equivalents (BaP-eq) for individual PAHs and applied the World Health Organization unit risk (UR) for BaP (UR = 8.7 × 10–5) to estimate lifetime cancer risks due to PAH exposures. Results: We observed some spatial and seasonal variability in PAH concentrations. The contribution of gas-phase PAHs to the total BaP-eq value was between 34% and 86%. The total estimated average lifetime lung cancer risk due to PAH exposure in the study area was 1.2 × 10–4. Conclusions: The estimated risk was higher than values recommended by the World Health Organization and U.S. Environmental Protection Agency but lower than the threshold value of 10–3 that is considered an indication of definite risk according to similar risk studies. The results also showed that risk may be underestimated if the contributions of gas-phase PAHs are not considered.

Ramirez, Noelia; Cuadras, Anna; Marce, Rosa Maria

2011-01-01

247

Atmosphere-ionosphere conductivity enhancements during a hard solar energetic particle event  

NASA Astrophysics Data System (ADS)

On 20 January 2005, a solar energetic particle (SEP) event caused the largest recorded solar proton ground level event since 1956. Serendipitously, a balloon-borne experiment intended to measure effects of relativistic electron precipitation was aloft over Antarctica (˜32 km near 70°S, 345°E geographic) throughout the duration of the SEP event, including the fast (˜6 min) onset. The balloon instrumentation included dc electric field and scalar electrical conductivity sensors. The observed conductivity increased by nearly a factor of 20 above ambient with the SEP event onset and returned to within a factor of two above normal levels within 17 h. Results from a newly developed, globally applicable atmosphere-ionosphere conductivity model based on the Sodankylä Ion and Neutral Chemistry (SIC) model suggest that proton-induced ionization was directly responsible for the observed conductivity increase at the balloon. Model input for this event included estimates of ionization from energetic particle precipitation and rigidity cutoffs. Altitudes between 20 and 150 km were considered during model runs. The results show a maximum conductivity increase near 60 km of more than 600-fold directly after SEP event onset. Relatively small conductivity enhancements (two- to fivefold) are suggested to have occurred above 70 km as a result of SEP ionization, while almost no enhancement is thought to have occurred above 95 km. These results quantify the real effect that an SEP-event can have on atmosphere-ionosphere electrical conductivity on a large, nearly global scale and provide a detailed comparison to one of the few direct stratospheric conductivity observations made during an SEP event.

Kokorowski, M.; Seppälä, A.; Sample, J. G.; Holzworth, R. H.; McCarthy, M. P.; Bering, E. A.; Turunen, E.

2012-05-01

248

Influences of fireworks on chemical characteristics of atmospheric fine and coarse particles during Taiwan's Lantern Festival  

NASA Astrophysics Data System (ADS)

In recent years, the celebration activities of various folk-custom festivals have been getting more and more attention from the citizens in Taiwan. Festivities throughout the whole island are traditionally accompanied by loud and brightly colored firework displays. Among these activities, the firework displays during Taiwan's Lantern Festival in Kaohsiung harbor is one of the largest festivals in Taiwan each year. Therefore, it is of importance to investigate the influence of fireworks displays on the ambient air quality during the Taiwan's Lantern Festival. Field measurements of atmospheric particulate matter (PM) were conducted on February 9th-11th, 2009 during Taiwan's Lantern Festival in Kaohsiung City. Moreover, three kinds of fireworks powders obtained from the same manufacturing factory producing Kaohsiung Lantern Festival fireworks were burned in a self-designed combustion chamber to determine the physicochemical properties of the fireworks' particles and to establish the source profile of firework burning. Several metallic elements of PM during the firework display periods were notably higher than those during the non-firework periods. The concentrations of Mg, K, Pb, and Sr in PM2.5 during the firework periods were 10 times higher than those during the non-firework periods. Additionally, the Cl-/Na+ ratio was approximately 3 during the firework display periods as Cl- came from the chlorine content of the firework powder. Moreover, the OC/EC ratio increased up to 2.8. Results obtained from PCA and CMB receptor modeling showed that major sources of atmospheric particles during the firework display periods in Kaohsiung harbor were fireworks, vehicular exhausts, soil dusts and marine sprays. Particularly, on February 10th, the firework displays contributed approximately 25.2% and 16.6% of PM10 at two downwind sampling sites, respectively.

Tsai, Hsieh-Hung; Chien, Li-Hsing; Yuan, Chung-Shin; Lin, Yuan-Chung; Jen, Yi-Hsiu; Ie, Iau-Ren

2012-12-01

249

Middle atmosphere response to the solar cycle in irradiance and ionizing particle precipitation  

NASA Astrophysics Data System (ADS)

The impact of NOx and HOx production by three types of energetic particle precipitation (EPP), auroral zone medium and high energy electrons, solar proton events and galactic cosmic rays on the middle atmosphere is examined using a chemistry climate model. This process study uses ensemble simulations forced by transient EPP derived from observations with one-year repeating sea surface temperatures and fixed chemical boundary conditions for cases with and without solar cycle in irradiance. Our model results show a wintertime polar stratosphere ozone reduction of between 3 and 10 % in agreement with previous studies. EPP is found to modulate the radiative solar cycle effect in the middle atmosphere in a significant way, bringing temperature and ozone variations closer to observed patterns. The Southern Hemisphere polar vortex undergoes an intensification from solar minimum to solar maximum instead of a weakening. This changes the solar cycle variation of the Brewer-Dobson circulation, with a weakening during solar maxima compared to solar minima. In response, the tropical tropopause temperature manifests a statistically significant solar cycle variation resulting in about 4 % more water vapour transported into the lower tropical stratosphere during solar maxima compared to solar minima. This has implications for surface temperature variation due to the associated change in radiative forcing.

Semeniuk, K.; Fomichev, V. I.; McConnell, J. C.; Fu, C.; Melo, S. M. L.; Usoskin, I. G.

2011-05-01

250

Be-7 nuclei produced by galactic cosmic rays and solar energetic particles in the earth's atmosphere  

NASA Astrophysics Data System (ADS)

Be-7 radioactive nuclei with a half-life of 53.3 days result from spallation reactions of galactic cosmic rays(GCR) and solar energetic particles (SEP) with N and O nuclei in the Earth's atmosphere. We calculate the average global production of Be-7 in the atmosphere by GCR and SEP The result indicates that an intense SEP event produces a large amount of Be-7 in the polar stratosphere and part of them could be transported to the surface at lower latitudes. The ground-level measurement of Be-7 in Japan exhibits the possibility of enhancement in the Be-7 radioactivity associated with the intense SEP event on July 14, 2000. In addition, the present experiment shows seasonal variations in the surface Be-7 concentration which peaks in spring and autumn. We discuss the possible air mass mixing between the stratosphere and troposphere to explain the measured seasonal variations. The surface concentration of Pb-210 nuclei indicates a similar trend to that of Be-7 and we suggest two possible explanations.

Yoshimori, M.; Hirayama, H.; Mori, S.; Sasaki, K.; Sakurai, H.

251

Device for the UV irradiation of the surface of materials in an ozone-containing atmosphere  

SciTech Connect

A device is described for the UV irradiation of the surface of materials in an ozone-containing atmosphere. Processes are considered for removing adsorbed hydrocarbon compounds from the surface layer of polished single crystals and etching submicron polymer films. 6 refs., 2 figs.

Levina, O.V.; Pukhov, A.M. [S.I. Vavilov State Optical Institute, St. Petersburg (Russian Federation)

1994-05-01

252

Classification of multiple types of organic carbon composition in atmospheric particles by scanning transmission X-ray microscopy analysis  

Microsoft Academic Search

A scanning transmission X-ray microscope at the Lawrence Berkeley National Laboratory is used to measure organic functional group abundance and morphology of atmospheric aerosols. We present a summary of spectra, sizes, and shapes observed in 595 particles that were collected and analyzed between 2000 and 2006. These particles ranged between 0.1 and 12?m and represent aerosols found in a large

S. Takahama; S. Gilardoni; L. M. Russell; A. L. D. Kilcoyne

2007-01-01

253

Fluorescence spectra of atmospheric aerosol at Adelphi, Maryland, USA: measurement and classification of single particles containing organic carbon  

Microsoft Academic Search

We measured laser-induced fluorescence spectra from individual supermicron-sized atmospheric particles drawn into our laboratory at Adelphi, MD, an urban site in the Washington, DC metroplex. A virtural impactor concentrator is used along with an aerodynamic-focusing-nozzle which forms, within an optical chamber, a focused aerosol jet where single aerosol particles can be interrogated on-the-fly with a pulsed 266-nm-wavelength laser. Sample rates

Ronald G. Pinnick; Steven C. Hill; Yong-Le Pan; Richard K. Chang

2004-01-01

254

Characterisation of atmospheric deposited particles during a dust storm in urban areas of Eastern Australia.  

PubMed

The characteristics of dust particles deposited during the 2009 dust storm in the Gold Coast and Brisbane regions of Australia are discussed in this paper. The study outcomes provide important knowledge in relation to the potential impacts of dust storm related pollution on ecosystem health in the context that the frequency of dust storms is predicted to increase due to anthropogenic desert surface modifications and climate change impacts. The investigated dust storm contributed a large fraction of fine particles to the environment with an increased amount of total suspended solids, compared to dry deposition under ambient conditions. Although the dust storm passed over forested areas, the organic carbon content in the dust was relatively low. The primary metals present in the dust storm deposition were aluminium, iron and manganese, which are common soil minerals in Australia. The dust storm deposition did not contain significant loads of nickel, cadmium, copper and lead, which are commonly present in the urban environment. Furthermore, the comparison between the ambient and dust storm chromium and zinc loads suggested that these metals were contributed to the dust storm by local anthropogenic sources. The potential ecosystem health impacts of the 2009 dust storm include, increased fine solids deposition on ground surfaces resulting in an enhanced capacity to adsorb toxic pollutants as well as increased aluminium, iron and manganese loads. In contrast, the ecosystem health impacts related to organic carbon and other metals from dust storm atmospheric deposition are not considered to be significant. PMID:23712117

Gunawardena, Janaka; Ziyath, Abdul M; Bostrom, Thor E; Bekessy, Lambert K; Ayoko, Godwin A; Egodawatta, Prasanna; Goonetilleke, Ashantha

2013-05-25

255

Seasonal pollution characteristics of organic compounds in atmospheric fine particles in Beijing.  

PubMed

Beijing is a rapidly developing city with severe and unique air pollution problems. Organic matter is the most abundant fraction in fine particles in Beijing, occupying 30-50% of the total mass, indicating its key role in air pollution control. However, detailed chemical characterization of particulate organic matter in Beijing has never been reported. In this study, fine particles in the urban atmosphere in Beijing were investigated for its organic components by GC/MS technique. Over 100 individual organic compounds were identified and quantified in 25 PM2.5 samples from the summer, autumn and winter of 2002-2003. Alkanes, fatty acids, dicarboxylic acids, polycyclic aromatic hydrocarbons and some important tracer compounds (hopanes, levoglucosan and steroids) were the major constituents with the sum of their concentrations of 502, 1471 and 1403 ng m(-3) in summer, autumn and winter, respectively. Different organic compounds presented apparently different seasonal characteristics, reflecting their different dominant emission sources, such as coal combustion, biomass burning and cooking emission. The abundance and origin of these organic compounds are discussed to reveal seasonal air pollution characteristics of Beijing. PMID:16083946

He, Ling-Yan; Hu, Min; Huang, Xiao-Feng; Zhang, Yuan-Hang; Tang, Xiao-Yan

2005-08-03

256

Light absorbing material (soot) in rainwater and in aerosol particles in the Maldives  

NASA Astrophysics Data System (ADS)

Simultaneous measurements of soot (absorbing material at 528 nm) and inorganic ions in aerosol and precipitation at the Maldives Climate Observatory Hanimaadhoo during the period May 2005 to February 2007 have made it possible to calculate the washout ratio (WR) of these components as a measure of how efficiently they are scavenged by precipitation. On the basis of air trajectories the data have been separated into days with polluted air arriving from the Indian subcontinent in a northeasterly sector during winter and clean monsoon days with southerly flow from the Indian Ocean. The average soot concentration was a factor of 10 higher in the former situations. Despite considerable scatter for individual days, a systematic pattern emerged when the WR for the different components were compared with each other. During the monsoon season the WR for soot was similar to that of sulfate and other fine mode aerosol components, indicating that soot containing particles in these situations were efficient as cloud condensation nuclei. The origin of the light absorbing material during the monsoon season is unclear. During the polluted winter days, on the other hand, the WR for soot was three times smaller than that of sulfate. This indicates that, even after a travel time of several days, the soot containing particles from India have retained much of their hydrophobic property. The low WR and the infrequent rain during this season probably contribute to extending the atmospheric lifetime of soot well beyond several days. Surprisingly high concentrations of non-sea-salt calcium were measured during the monsoon season, substantially higher than during the winter season. The origin of these high values could be long-range transport from the Australian or African continents. Another possibility might be exopolymer gels derived from the ocean surface microlayer.

Granat, L.; EngströM, J. E.; Praveen, S.; Rodhe, H.

2010-08-01

257

Visibility of plasmonic particles embedded in transparent materials  

NASA Astrophysics Data System (ADS)

Recently, several experiments have shown that it is possible to visualize the optical near-field generated around individual plasmonic particles through the photo-induced structuration of polymer films. In this communication, we show that the particle visibility can be controlled at will down to the quasi-invisibility by tuning the incident wavelength around the plasmon frequency. This phenomenon occurs when the real part of the particle polarizability displays a sign change. This simple spectrally controlled visibility is an alternative to the more classical spatially controlled visibility approach.

Teulle, A.; Marty, R.; Girard, C.; Arbouet, A.; Dujardin, E.

2013-03-01

258

Space charge distribution measurement methods and particle loaded insulating materials  

NASA Astrophysics Data System (ADS)

In this paper the authors discuss the effects of particles (fillers) mixed in a composite polymer on the space charge measurement techniques. The origin of particle-induced spurious signals is determined and silica filled epoxy resin is analysed using the laser-induced-pressure-pulse (LIPP) method, the pulsed-electro-acoustic (PEA) method and the laser-induced-thermal-pulse (LITP) method. A spurious signal identified as the consequence of a piezoelectric effect of some silica particles is visible for all the method. Moreover, space charges are clearly detected at the epoxy/silica interface after a 10 kV mm-1 poling at room temperature for 2 h.

Holé, S.; Sylvestre, A.; Gallot Lavallée, O.; Guillermin, C.; Rain, P.; Rowe, S.

2006-03-01

259

Autofluorescence of atmospheric bioaerosols - fluorescent biomolecules, biological standard particles and potential interferences  

NASA Astrophysics Data System (ADS)

Primary biological aerosol particles (PBAP) such as pollen, fungal spores, bacteria, biogenic polymers and debris from larger organisms are known to influence atmospheric chemistry and physics, the biosphere and public health. PBAP account for up to ~30% of fine and up to ~70% of coarse particulate matter in urban, rural and pristine environment and are released with estimated emission rates of up to ~1000 Tg/a [1]. Continuous measurements of the abundance, variability and diversity of PBAP have been difficult until recently, however. The application of on-line instruments able to detect autofluorescence from biological particles in real-time has been a promising development for the measurement of PBAP concentrations and fluxes in different environments [2,3]. The detected fluorescent biological aerosol particles (FBAP) can be regarded as a subset of PBAP, although the exact relationship between PBAP and FBAP is still being investigated. Autofluorescence of FBAP is usually a superposition of fluorescence from a mixture of individual fluorescent molecules (fluorophores). Numerous biogenic fluorophores such as amino acids (e.g., tryptophan, tyrosine), coenzymes (e.g., NAD(P)H, riboflavin) and biopolymers (e.g., cellulose) emit fluorescent light due to heterocyclic aromatic rings or conjugated double bonds within their molecular structures. The tryptophan emission peak is a common feature of most bioparticles because the amino acid is a constituent of many proteins and peptides. The influence of the coenzymes NAD(P)H and riboflavin on the autofluorescence of bacteria can be regarded as an indicator for bacterial metabolism and has been utilized to discriminate between viable and non-viable organisms [4]. However, very little information is available about other essential biofluorophores in fungal spores and pollen. In order to better understand the autofluorescence behavior of FBAP, we have used fluorescence spectroscopy and fluorescence microscopy to analyze standard bioparticles (pollen, fungal spores, and bacteria) as well as atmospherically relevant chemical substances. We found varying levels of fluorescent emission and significant differences in the spectral properties of major PBAP classes. The combination will support the quantitative interpretation of data obtained by real-time FBAP instrumentation [5]. [1] Elbert, W., Taylor, P. E., Andreae, M. O., & Pöschl, U. (2007). Atmos. Chem. Phys., 7, 4569-4588. [2] Huffman, J. A., Treutlein, B., & Pöschl, U. (2010). Atmos. Chem. Phys., 10, 3215-3233. [3] Pöschl, U., et al. (2010). Science, 329, 1513-1516. [4] Lakowicz, J., Principles of fluorescence spectroscopy, Plenum publishers, New York, 1999. [5] Pöhlker, C., Huffman, J. A., & Pöschl, U., (2012). Atmos. Meas. Tech., 5, 37-71.

Pöhlker, C.; Huffmann, J. A.; Pöschl, U.

2012-04-01

260

Coupling of Particle Acceleration and Atmospheric Dynamic Response to Impulsive Energy Release in Solar Flares  

NASA Astrophysics Data System (ADS)

In solar flares, acceleration and transport of high-energy particles and fluid dynamics of the atmospheric plasma are interrelated processes coupled in a circular chain. Chromospheric evaporation, for example, can alter the density and temperature distribution along the flare loop, in particular in the acceleration site near the loop-top source. This produces a feedback on particle collisional heating, and more importantly on the energy release and acceleration process. This in turn will change the heating of the chromosphere and mass flows in the corona. In recent years, there have been increasing theoretical and observational motivations to investigate these coupled processes together in a self-consistent manner. We present here combined Fokker-­Planck modeling of particles and hydrodynamic simulation of flare plasma. We extended our earlier hybrid simulation (Liu, Petrosian, Mariska 2009) by feeding the updated plasma density and temperature at the loop-top source to the stochastic acceleration process. We find that the density enhancement causes the ratio of the electron plasma frequency to gyro-frequency to increase. This can lead to the reduction of the efficiency of electron acceleration and thus the quenching or spectral softening of nonthermal hard X-ray tails observed during the late stages of flares. This also affects the relative production of energetic electrons vs. protons (Petrosian and Liu 2004). We will compare our results with recent observations from RHESSI, SDO, and Hinode. We will also discuss their implications for cyclic spectral hardening, quasi-periodic flare pulsations, and recently imaged super-fast quasi-periodic coronal waves originating from flare kernels.

Liu, Wei; Petrosian, V.; Chen, Q.; Mariska, J.

2012-05-01

261

ESCAPING PARTICLE FLUXES IN THE ATMOSPHERES OF CLOSE-IN EXOPLANETS. I. MODEL OF HYDROGEN  

SciTech Connect

A multi-fluid model for an atomic hydrogen-proton mixture in the upper atmosphere of an extrasolar planet is presented when the continuity and momentum equations of each component have already been solved with an energy equation. The particle-number density, temperature distribution, and structure of velocity can be found by using the model. I chose two special objects, HD 209458b and HD 189733b, for discussion and concluded that their predicted mass-loss rates are consistent with those observed. The most important physical process in coupling each component is the charge exchange, which couples atomic hydrogen tightly with protons. Most of the hydrogen escapes from hot Jupiters as protons, especially in the young star-planet system. I found that the single-fluid model can describe the escape of particles when the mass-loss rate is higher than a few times 10{sup 9} g s{sup -1}, while below 10{sup 9} g s{sup -1} the multi-fluid model is more suitable because of the decoupling of particles. Assuming an energy limit, I found that the predicted mass-loss rates of HD 189733b are a factor of 10 larger than those calculated by my models because of a high degree of ionization. For ionized wind, which is mainly composed of protons, assuming an energy limit is no longer effective. I fitted the mass-loss rates of the ionized wind as a function of F{sub UV} by calculating the variation of the mass-loss rates with UV fluxes.

Guo, J. H., E-mail: guojh@ynao.ac.cn [National Astronomical Observatories/Yunnan Observatory, Chinese Academy of Sciences, P.O. Box 110, Kunming 650011 (China)

2011-06-01

262

Analysis of impact energy factors in ductile materials using single particle impact tests on gas gun  

Microsoft Academic Search

Wear is surface damage that involves progressive material loss due to relative motion between the contacting surfaces. Removal of material by action of impacting particles is known as erosion. Single particle impact tests were conducted using small particles (95–100?m) and impact velocity 90ms?1. A new technique has been developed to measure the impact crater using Laser Scanning Confocal Microscope (LSCM).

A. A. Cenna; K. C. Williams; M. G. Jones

2011-01-01

263

Particle-induced damage and subsequent healing of materials: Erosion, corrosion and self-healing coatings  

Microsoft Academic Search

This review summarizes research on particle-induced damage and the subsequent repair of metallic materials. Metallic materials are damaged by solid particle impact via two damage processes: repeated plastic deformation and cutting. At a certain low-impact velocity, the particle does not skid, resulting in only plastic deformation with no damage by cutting. The critical impact velocity has been theoretically derived. Self-healing

Akihiro Yabuki

2011-01-01

264

Grain boundary diffusional creep of materials containing particles  

Microsoft Academic Search

A theoretical treatment is presented which calculates the effect of grain boundary particles on diffusional creep for the case where the interfacial diffusivity is less than that in the grain boundary.

B. Burton; W. B. Beeré

1981-01-01

265

Promoted cell and material interaction on atmospheric pressure plasma treated titanium  

NASA Astrophysics Data System (ADS)

Surface carbon contamination is a natural phenomenon. However, it interferes with cell-biomaterial interaction. In order to eliminate the interference, atmospheric pressure plasma treatment was employed. Dielectric barrier discharge treatment of titanium surface for less than 10 min turned titanium super-hydrophilic. Adsorption of fibronectin which is the major cell adhesive protein increased after plasma treatment. Cell attachment parameters of osteoblast cells such as population, cell area, perimeter, Feret's diameter and cytoskeleton development were also enhanced. Cell proliferation increased on the plasma treated titanium. In conclusion, dielectric barrier discharge type atmospheric pressure plasma system is effective to modify titanium surface and the modified titanium promotes cell and material interactions.

Han, Inho; Vagaska, Barbora; Seo, Hyok Jin; Kang, Jae Kyeong; Kwon, Byeong-Ju; Lee, Mi Hee; Park, Jong-Chul

2012-03-01

266

Insitu measurements of laser-induced-fluorescence spectra of single atmospheric organic carbon aerosol particles for their partial classification. (Invited)  

NASA Astrophysics Data System (ADS)

Aerosols are ubiquitous in the earth’s atmosphere. Within the last two decades, the importance of organic carbon aerosols (OCAs) has been widely recognized. OCAs have both natural and anthropogenic sources and have effects ranging from atmospheric radiative forcing to human health. Improved methods for measuring and classifying OCAs are needed for better understanding their sources, transformation, and fate. In this talk we focus on the use of a relatively new technique for characterization of single OCA particles in atmospheric aerosol: ultraviolet laser-induced-fluorescence (UV-LIF). UV-LIF spectra of atmospheric aerosols measured at multiple sites with different regional climate (Adelphi, MD, New Haven, CT, and Las Cruces, NM) are reported. A hierarchical clustering method was used to cluster (approximately 90%) of the single-particle UV-LIF spectra into 8-10 groups (clusters). Some of these clusters have spectra that are similar to spectra of some important classes of atmospheric aerosol, such as humic/fulvic acids and humic-like substances, bacteria, cellulose, marine aerosol, and polycyclic aromatic hydrocarbons. The most highly populated clusters, and some of the less populated ones, appear at all sites. On average, spectra characteristic of humic/fulvic acids and humic-like-substances (HULIS) comprise 28-43% of fluorescent particles at all three sites; whereas cellulose-like spectra contribute only 1-3%.

Pinnick, R. G.; Pan, Y.; Hill, S.; Rosen, J. M.; Chang, R. K.

2009-12-01

267

Elemental analysis by PIXE and other IBA techniques and their application to source fingerprinting of atmospheric fine particle pollution  

Microsoft Academic Search

The PIXE technique in conjunction with PIGME, PESA and RBS has been used to routinely measure over 20 different elements present in fine particle atmospheric samples. PIXE provided data for selected elements from Al to U while the other techniques provided information on elements lighter than Al such as H, C, N, O, F and Na. Detection limits for the

David D. Cohen; Grahame M. Bailey; Ramesh Kondepudi

1996-01-01

268

Calibration of an optical particle counter to provide PM 2.5 mass for well-defined particle materials  

Microsoft Academic Search

A light scattering optical particle counter (OPC) was re-calibrated for a well-defined particle material, to convert optical equivalent size both into aerodynamic and volume equivalent diameters. For specific test dusts, the calibrated OPC provides a direct read-out dust mass vs. aerodynamic diameter and — by weighting the appropriate size bins with the standard transmission curve — as total PM2.5 mass.

J. Binnig; J. Meyer; G. Kasper

2007-01-01

269

Effect on surface roughness of zerodur material in atmospheric pressure plasma jet processing  

NASA Astrophysics Data System (ADS)

Zerodur material is considered as the ideal material in the high performance optic systems because of its excellent thermal stability characteristics. This paper deals with the impacting factors on the zerodur material surface roughness during atmospheric pressure plasma jet(APPJ) processing. At first, based on multiphase and multi-component in zerodur material, the effect on the zerodur surface chemical components and surface roughness is studied when the element contained Si is etched during the chemical machining process. The change of surface microcosmic topography is observed, it is proved that the technology of atmospheric pressure plasma jet can modify the surface roughness of zerodur material. Moreover, in consideration of the re-deposition phenomenon in the machining process, the composition of the re-deposition are studied and the genesis of the re-deposition were analysed. Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray spectrometry (EDX) were utilized to obtain the elemental composition of the sample powder residuum on zerodur surface. The relationship between substrate roughness and the process parameters is established based on the experimental results. Experimental results indicate that it is beneficial to add certain amount O2 to modify the surface roughness of zerodur material. This finding provides an important basis for the improvement of surface roughness in APPJ of zerodur material.

Jin, H. L.; Wang, B.; Zhang, F. H.

2010-05-01

270

Gas-particle partitioning of atmospheric Hg(II) and its effect on global mercury deposition  

NASA Astrophysics Data System (ADS)

Atmospheric deposition of Hg(II) represents a major input of mercury to surface environments. The phase of Hg(II) (gas or particle) has important implications for deposition. We use long-term observations of reactive gaseous mercury (RGM, the gaseous component of Hg(II)), particle-bound mercury (PBM, the particulate component of Hg(II)), fine particulate matter (PM2.5), and temperature (T) at five sites in North America to derive an empirical gas-particle partitioning relationship log10(K-1) = (10±1)-(2500±300)/T where K = (PBM/PM2.5)/RGM with PBM and RGM in common mixing ratio units, PM2.5 in ?g m-3, and T in K. This relationship is within the range of previous work but is based on far more extensive data from multiple sites. We implement this empirical relationship in the GEOS-Chem global 3-D Hg model to partition Hg(II) between the gas and particle phases. The resulting gas-phase fraction of Hg(II) ranges from over 90 % in warm air with little aerosol to less than 10 % in cold air with high aerosol. Hg deposition to high latitudes increases because of more efficient scavenging of particulate Hg(II) by precipitating snow. Model comparison to Hg observations at the North American surface sites suggests that subsidence from the free troposphere (warm air, low aerosol) is a major factor driving the seasonality of RGM, while elevated PBM is mostly associated with high aerosol loads. Simulation of RGM and PBM at these sites is improved by including fast in-plume reduction of Hg(II) emitted from coal combustion and by assuming that anthropogenic particulate Hg(p) behaves as semi-volatile Hg(II) rather than as a refractory particulate component. We improve the simulation of Hg wet deposition fluxes in the US relative to a previous version of GEOS-Chem; this largely reflects independent improvement of the washout algorithm. The observed wintertime minimum in wet deposition fluxes is attributed to inefficient snow scavenging of gas-phase Hg(II).

Amos, H. M.; Jacob, D. J.; Holmes, C. D.; Fisher, J. A.; Wang, Q.; Yantosca, R. M.; Corbitt, E. S.; Galarneau, E.; Rutter, A. P.; Gustin, M. S.; Steffen, A.; Schauer, J. J.; Graydon, J. A.; St. Louis, V. L.; Talbot, R. W.; Edgerton, E. S.; Zhang, Y.; Sunderland, E. M.

2012-01-01

271

A simplified approach for solving coagulation–diffusion equation to estimate atmospheric background particle number loading factors contributed by emissions from localized sources  

Microsoft Academic Search

Coagulation and condensation\\/evaporation combined with atmospheric dispersion are the main processes responsible for the evolution of aerosol particle size distributions and number concentrations emitted from localized sources. A crucial question is: what fraction of freshly emitted particles survive intra-coagulation effect to persist in the atmosphere and become available for further interaction with background aerosols?. The difficulty in estimating this quantity,

S. Anand; Y. S. Mayya

2011-01-01

272

Fabrication and morphology of spongelike polymer material based on cross-linked sulfonated polystyrene particles.  

PubMed

A novel spongelike polymer material has been fabricated by ?-ray induced polymerization of methylmethacrylate (MMA) in an emulsion containing cross-linked sulfonated polystyrene (CSP) particles. Scanning electron microscopy (SEM) images reveal that the spongelike structure is made up of interlinked nanosized PMMA particles with micrometer-sized CSP-PMMA particles embedded inside. The nitrogen adsorption isotherm discloses that the spongelike material has a high specific surface area of 29 m(2)/g and a narrow pore size distribution of 60-120 nm. The formation mechanism is discussed in this paper, which indicates that the key steps to form the spongelike material include a Pickering emulsion stabilized by the CSP particles, followed by the swelling process of MMA into these particles. This approach offers a more convenient alternative to prepare polymeric spongelike material without any etching procedure. PMID:22423984

Ji, Xiang; Wang, Mozhen; Xu, Dezhi; Ge, Xuewu; Liu, Huarong; Tang, Tao

2012-03-19

273

First Measurements of Neutral Atmospheric Cluster and 1–2 nm Particle Number Size Distributions During Nucleation Events  

SciTech Connect

Recent observations throughout the atmosphere have shown that nucleation occurs frequently (Kulmala et al. 2004). Modeling studies and observations have shown that nucleated particles contribute significantly to concentrations of cloud condensation nuclei (Spracklen et al. 2008), thereby affecting climate (IPCC 2007). Size-resolved measurements extending down to molecular dimensions can provide information on processes that lead to nucleation and would enable development and verification of theories for particle nucleation and growth in the atmosphere and other aerosol systems. This article describes measurements of the complete number size distribution, spanning the size range from vapor molecules and molecular clusters to submicrometer particles, during atmospheric nucleation events. The measurements used two new instruments, the cluster chemical ionization mass spectrometer (Cluster CIMS) and the DEG SMPS. The Cluster CIMS measures neutral molecular clusters from 50 to 900 amu. The DEG SMPS is a scanning mobility particle spectrometer (SMPS) equipped with a diethylene glycol (DEG)-based condensation particle counter (CPC) capable of 1.1 nm mobility diameter particle detection, and overlapping the sizes detected by the Cluster CIMS (Iida et al. 2009; Jiang et al. 2011). The Cluster CIMS distinguishes neutral clusters from ions formed by ion-induced clustering by varying the reaction time for ions with the sampled air (Zhao et al. 2010). It distinguishes clusters from high molecular weight gases by measuring the incremental signal at a specified mass detected during nucleation events. The clusters that were measured in this study contain sulfuric acid, which is known to participate in atmospheric nucleation (Kuang et al. 2008).

Jiang, J.; Kuang, C.; Zhao, J.; Chen, M.; Eisele, F. L.; Scheckman, J.; Williams, B. J.; McMurry, P. H.

2011-02-01

274

Rubber Particles from Recycled Tires in Cementitious Composite Materials.  

National Technical Information Service (NTIS)

In the present study, the influence of the shape of rubber particles on mechanical properties ofmortar was examinedby using rubber granules ofabout 2 mm in diameter (GR 2) and two sizes offibrous rubber (one being about 5.5 mm long and about 1.2 mm diamet...

C. F. Ferraris D. Raghavan H. Huynh

1996-01-01

275

Absorption of Beta Particles in Different Materials: An Undergraduate Experiment  

ERIC Educational Resources Information Center

|The absorption of beta rays from a radioactive source in different materials was investigated by the use of a simple setup based on a Geiger counter and a set of absorber sheets. The number of electrons traversing the material was measured as a function of its thickness. Detailed GEANT simulations were carried out to reproduce the obtained…

La Rocca, Paola; Riggi, Francesco

2009-01-01

276

Atmospheric Plasma Spraying Low-Temperature Cathode Materials for Solid Oxide Fuel Cells  

Microsoft Academic Search

Atmospheric plasma spraying (APS) is attractive for manufacturing solid oxide fuel cells (SOFCs) because it allows functional\\u000a layers to be built rapidly with controlled microstructures. The technique allows SOFCs that operate at low temperatures (500-700 °C)\\u000a to be fabricated by spraying directly onto robust and inexpensive metallic supports. However, standard cathode materials used\\u000a in commercial SOFCs exhibit high polarization resistances at

J. Harris; O. Kesler

2010-01-01

277

Adsorption and reactions of atmospheric constituents and pollutants on ice particles: an FTIR study  

NASA Astrophysics Data System (ADS)

Processes on icy particles attract much attention due to their importance for atmospheric science, ecology and astrophysics. In this work, adsorption and ecologically important reactions of some molecules on pure and mixed water icy films by means of FTIR spectroscopy have been investigated. The cell for spectral studies of adsorbed molecules at variable temperatures (55-370 K), described elsewhere1, enables one to run the spectra in the presence of gaseous adsorbate, and even to perform adsorption from the solution in some cryogenic solvents. For the studies of ice films, it was equipped with a device for water vapour sputtering from the heated capillaries and deposition onto the inner BaF2 or ZnSe windows of the cell, cooled by liquid nitrogen. Lower temperatures were obtained by pumping off evaporating nitrogen from the coolant volume. The estimated specific surface area of freshly deposited at 77 K water ice film was about 160 m2/g and decreases on raising the temperature together with the diminishing intensity of the bands of dangling OH (OD) groups at 3696 (2727) cm-1 until the latter disappear at 130 - 160 K when the changes of bulk absorption provide evidence for a phase transition from amorphous to polycrystalline ice. CO adsorption at 77 K results in two bands at 2153 and 2137 cm-1 assigned to molecules forming weak H-bond with the dangling hydroxyl groups and bound to unsaturated surface oxygen atoms, respectively2. The band of dangling hydroxyl groups moves to lower wavenumbers on adsorption of different molecules (hydrogen, nitrogen, methane, ozone, NO, ethane or chlorinated ethenes, etc.). The shift value depends on the nature of adsorbate. Besides this shift, spectra of adsorbed nitrogen and methane registered at 55 K reveal the adsorption intensity decrease at ~ 2650 cm-1 at the high-frequency slope of bulk adsorption, and increase at about 25 cm-1 below. We interpret this perturbation as a strengthening of H-bonds between surface water molecules, which act as adsorption sites either as a proton-donor or as a donor of the lone pair of electrons. Such adsorption-induced relaxation explains the dependence of physico-chemical properties of icy particles on the presence of atmospheric gases. Spectra HCN/D2O and ND3/D2O mixed icy films with low (1:10) dopant/water ratios do not manifest any changes in the acidic or basic properties of dangling hydroxyl groups or surface oxygen atoms, but reveal a difference in the proportion between the concentrations of these sites as compared with that for pure water ice. For high dopant concentrations (1:1), the dangling hydroxyls were not observed; the dominant adsorption sites for CO are likely to be the unsaturated oxygen atoms, while serious structural changes occur in the bulk of ices. Ecologically important reactions of atmospheric pollutants such as ozonolysis of ethene, chlorinated ethenes, hydrogen cyanide, and methyl bromide adsorbed on water ice film as well as the influence of UV radiation on this process have been studied in 77 - 200 K temperature range by FTIR spectroscopy. Ozone co-adsorption with ethene or C2H3Cl readily leads to ozonolysis reaction, which also starts for C2H2Cl2 isomers but only at temperatures elevated up to 120 - 150 K. Co-adsorption of O3 with HCN or CH3Br molecules in the dark does not lead to any noticeable spectral changes. Irradiation of HCN or CH3Br deposited on ice films in the presence of ozone leads to appearance of new bands revealing the formation of ozonolysis products. The same "synergetic effect" of simultaneous action of ozone and UV radiation at 77 K, was found for C2H2Cl2 isomers and C2Cl4, which are resistant against O3 even at higher temperatures. The obtained spectral dependence of photo-ozonolysis of C2Cl4 and HCN at 77 K shows that photoexcitation or photodissociation of ozone, evidently, accounts for the observed processes. The surface of ice particles, thus, plays the role of a condenser of atmospheric pollutants and acts as a micro- photoreactor in the atmospheric chemistry. Acknowledgments. The work was

Rudakova, A. V.; Marinov, I. L.; Poretskiy, M. S.; Tsyganenko, A. A.

2009-04-01

278

Modeling of in situ ultrafine atmospheric particle formation in the eastern United States  

NASA Astrophysics Data System (ADS)

The creation of new atmospheric particles from in situ nucleation influences climate through cloud-aerosol interactions and may negatively impact human health. Although recent observations show that nucleation is widespread in the eastern United States, the corresponding pathways remain uncertain. Combining extensive field measurements in Pittsburgh, Pennsylvania, with an aerosol dynamics and chemistry model assuming ternary NH3-H2SO4-H2O nuclei formation, we show excellent model-measurement agreement and predictive capability. The ternary NH3-H2SO4-H2O nucleation model is successful in predicting the presence or lack of nucleation on 19 out of 19 days with complete data sets in July 2001 and on 25 out of 29 days in January 2002. Reductions of ammonia emissions are predicted to decrease the frequency of nucleation events during both summer and winter, with a more dramatic effect during the summer. The response to changes in emissions of sulfur dioxide during the summer is counterintuitive. Reductions of sulfur dioxide and the resulting sulfate by up to 40% actually increase the frequency of the summer nucleation events. Modeling predicts the opposite effect in winter, with reductions of sulfur dioxide leading to fewer nucleation events.

Gaydos, Timothy M.; Stanier, Charles O.; Pandis, Spyros N.

2005-04-01

279

Levoglucosan, a tracer for cellulose in biomass burning and atmospheric particles  

NASA Astrophysics Data System (ADS)

The major organic components of smoke particles from biomass burning are monosaccharide derivatives from the breakdown of cellulose, accompanied by generally lesser amounts of straight-chain, aliphatic and oxygenated compounds and terpenoids from vegetation waxes, resins/gums, and other biopolymers. Levoglucosan and the related degradation products from cellulose can be utilized as specific and general indicator compounds for the presence of emissions from biomass burning in samples of atmospheric fine particulate matter. This enables the potential tracking of such emissions on a global basis. There are other compounds (e.g. amyrones, friedelin, dehydroabietic acid, and thermal derivatives from terpenoids and from lignin—syringaldehyde, vanillin, syringic acid, vanillic acid), which are additional key indicators in smoke from burning of biomass specific to the type of biomass fuel. The monosaccharide derivatives (e.g. levoglucosan) are proposed as specific indicators for cellulose in biomass burning emissions. Levoglucosan is emitted at such high concentrations that it can be detected at considerable distances from the original combustion source.

Simoneit, B. R. T.; Schauer, J. J.; Nolte, C. G.; Oros, D. R.; Elias, V. O.; Fraser, M. P.; Rogge, W. F.; Cass, G. R.

280

Identifying organic aerosol sources by comparing functional group composition in chamber and atmospheric particles  

PubMed Central

Measurements of submicron particles by Fourier transform infrared spectroscopy in 14 campaigns in North America, Asia, South America, and Europe were used to identify characteristic organic functional group compositions of fuel combustion, terrestrial vegetation, and ocean bubble bursting sources, each of which often accounts for more than a third of organic mass (OM), and some of which is secondary organic aerosol (SOA) from gas-phase precursors. The majority of the OM consists of alkane, carboxylic acid, hydroxyl, and carbonyl groups. The organic functional groups formed from combustion and vegetation emissions are similar to the secondary products identified in chamber studies. The near absence of carbonyl groups in the observed SOA associated with combustion is consistent with alkane rather than aromatic precursors, and the absence of organonitrate groups can be explained by their hydrolysis in humid ambient conditions. The remote forest observations have ratios of carboxylic acid, organic hydroxyl, and nonacid carbonyl groups similar to those observed for isoprene and monoterpene chamber studies, but in biogenic aerosols transported downwind of urban areas the formation of esters replaces the acid and hydroxyl groups and leaves only nonacid carbonyl groups. The carbonyl groups in SOA associated with vegetation emissions provides striking evidence for the mechanism of esterification as the pathway for possible oligomerization reactions in the atmosphere. Forest fires include biogenic emissions that produce SOA with organic components similar to isoprene and monoterpene chamber studies, also resulting in nonacid carbonyl groups in SOA.

Russell, Lynn M.; Bahadur, Ranjit; Ziemann, Paul J.

2011-01-01

281

Source identification of lead pollution in the atmosphere of Shanghai City by analyzing single aerosol particles (SAP)  

SciTech Connect

A new method combining the pattern recognition (PR) technique with micro-PIXE spectrum was used for direct assessment of lead pollution in the atmosphere of Shanghai City. Single aerosol particles (SAP) of PM{sub 10} (<10 {micro}m) were analyzed using the nuclear microprobe. Every particle is characterized with its micro-PICE spectrum, which can be considered its fingerprint. The PR technique was applied to trace a lead contaminated aerosol particle back to its source. The discrimination of different pollutant sources was enhanced with investigating the individual aerosol particles. The results showed that the lead contamination from automobile exhaust should not be neglected. The lead concentration with low level was detected in most unleaded gasoline particles; however, the highest lead level of 1,500 ppm was found in one of them. Furthermore, four other main pollutant sources contributing to the lead contamination in the Shanghai atmosphere were clearly identified by this method. They are the cement industry, the coal combustion, the oil combustion, and the metallurgic industry. Some other unidentified particles suggested that some more lead emitters might also exist in Shanghai.

Wang, J.; Guo, P.; Li, X. [and others

2000-05-15

282

Photons and particles emitted from cold atmospheric-pressure plasma inactivate bacteria and biomolecules independently and synergistically.  

PubMed

Cold atmospheric-pressure plasmas are currently in use in medicine as surgical tools and are being evaluated for new applications, including wound treatment and cosmetic care. The disinfecting properties of plasmas are of particular interest, given the threat of antibiotic resistance to modern medicine. Plasma effluents comprise (V)UV photons and various reactive particles, such as accelerated ions and radicals, that modify biomolecules; however, a full understanding of the molecular mechanisms that underlie plasma-based disinfection has been lacking. Here, we investigate the antibacterial mechanisms of plasma, including the separate, additive and synergistic effects of plasma-generated (V)UV photons and particles at the cellular and molecular levels. Using scanning electron microscopy, we show that plasma-emitted particles cause physical damage to the cell envelope, whereas UV radiation does not. The lethal effects of the plasma effluent exceed the zone of physical damage. We demonstrate that both plasma-generated particles and (V)UV photons modify DNA nucleobases. The particles also induce breaks in the DNA backbone. The plasma effluent, and particularly the plasma-generated particles, also rapidly inactivate proteins in the cellular milieu. Thus, in addition to physical damage to the cellular envelope, modifications to DNA and proteins contribute to the bactericidal properties of cold atmospheric-pressure plasma. PMID:24068175

Lackmann, Jan-Wilm; Schneider, Simon; Edengeiser, Eugen; Jarzina, Fabian; Brinckmann, Steffen; Steinborn, Elena; Havenith, Martina; Benedikt, Jan; Bandow, Julia E

2013-09-25

283

Source apportionment of fine atmospheric particles in Marseille: a one year study  

NASA Astrophysics Data System (ADS)

Marseille is the second most populated city in France with more than one million inhabitants. With traffic of about 88 million tons (Mt) in 2011, Marseille is also the most important port of the Mediterranean Sea, and also in the vicinity of the large petrochemical and industrial area of Fos-Berre, located 40 km northwest of the metropolitan area. For these reasons, Marseille area represents a challenging case study for source apportionment exercises, combining an active photochemistry and multiple emission sources, including fugitive emissions from industrial sources and shipping. In order to develop strategies for controlling and reducing air pollution, there is a need of source apportionment studies in order to better understand the influence of the different sources of aerosol particles. Within the framework of the EU-MED APICE project (Common Mediterranean strategy and local practical Actions for the mitigation of Port, Industries and Cities Emissions ; www.apice-project.eu), sources of atmospheric particles in Marseille were evaluated for a one-year period by a long monitoring campaign conducted at two sampling sites. PM2.5 were collected continuously on a 24h-basis in an urban background site from July 2011 to July 2012 and on a 48h-basis for the Eastern dock from November 2011 to July 2012 using high volume samplers (DA80) operating at a flow rate of 30m3 h-1. In this work, two different source apportionment models were used to explain the chemical observations, and to investigate the sources of organic aerosol in Marseille. Two sources apportionment models were used and combined to quantify the contribution of the main aerosol particles sources: CMB (Chemical Mass Balance) and PMF (Positive Matrix Factorization). Both models were used with organic molecular markers and metals/trace elements. Both approaches are able to identify major sources, the combination of these two commonly used receptor models offer interesting perspective, especially when the factors derived from PMF analysis are injected as source profiles in CMB calculation.

Marchand, Nicolas; Salameh, Dalia; Detournay, Anais; Wortham, Henri; Jaffrezo, Jean-Luc; Piot, Christine; Armengaud, Alexandre; Piga, Damien; Parra, Michael; Deveze, Magali

2013-04-01

284

Discrete Particle Swarm Optimization for Materials Budget Allocation in Academic Libraries  

Microsoft Academic Search

We formulate the problem of materials budget allocation for academic libraries by way of the mathematical programming model and design an effective algorithm using discrete particle swarm optimization to resolve the problem. The objective function is to maximize the average preferences of materials selection subjected to the constraints of material costs and required amounts in specified categories. For the comparison

Tsu-Feng Ho; Shyong Jian Shyu; Yi-Ling Wu; B. M. T. Lin

2010-01-01

285

Status of materials handbooks for particle accelerator and nuclear reactor applications  

Microsoft Academic Search

In support of research and development for accelerator applications, a materials handbook was developed in August of 1998 funded by the Accelerator Production of Tritium Project. This handbook, presently called Advanced Fuel Cycle Initiative (AFCI) Materials Handbook, Materials Data for Particle Accelerator Applications, has just issued Revision 5 and contains detailed information showing the effects of irradiation on many properties

Stuart Maloy; Berylene Rogers; Weiju Ren; Philip Rittenhouse

2008-01-01

286

Bell Test for the Free Motion of Material Particles  

SciTech Connect

We present a scheme to establish nonclassical correlations in the motion of two macroscopically separated massive particles without resorting to entanglement in their internal degrees of freedom. It is based on the dissociation of a diatomic molecule with two temporally separated Feshbach pulses generating a motional state of two counterpropagating atoms that is capable of violating a Bell inequality by means of correlated single-particle interferometry. We evaluate the influence of dispersion on the Bell correlation, showing it to be important but manageable in a proposed experimental setup. The latter employs Bose-Einstein condensation of fermionic lithium atoms, uses laser-guided atom interferometry, and seems to be within the reach of present-day technology.

Gneiting, Clemens; Hornberger, Klaus [Arnold Sommerfeld Center for Theoretical Physics, Ludwig-Maximilians-Universitaet Muenchen, Theresienstrasse 37, 80333 Munich (Germany)

2008-12-31

287

Phonon-mediated particle detection with superconducting detector materials  

NASA Astrophysics Data System (ADS)

It is shown that a calorimeter composed of a cylindrical-shape absorber of superconducting V metal, with 25 x 10 mm dimensions and weighing 15 g, is sensitive to thermal phonons that have been generated by the stopping and the absorption of a 5 MeV alpha-particle. A further improvement in energy resolution is expected via lowering of calorimeter operating temperature from 120 mK to 10-50 mK.

Azgui, F.; von Feilitzsch, F.; Forster, G.

1992-10-01

288

Particle Size Effects on Thermal Decomposition of Energetic Material  

Microsoft Academic Search

This work refers to a study of the thermal decomposition of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) by differential scanning calorimetry (DSC) under nonisothermal conditions, with heating rates from 5 to 20°C min. The influence of the particle size in the thermal decomposition of HMX was verified. The activation energy for the decomposition of each sample was calculated using the peak temperature shift methods, proposed

M. Fathollahi; S. M. Pourmortazavi; S. G. Hosseini

2007-01-01

289

Dynamics of Granular Materials and Particle-Laden Flows  

SciTech Connect

Rapid granular flows and particle-laden flows were studied in laboratory experiments, molecular dynamics simulations, and simulations of continuum equations. The research demonstrated that the inclusion of friction is crucial in realistic modeling of granular flows; hence extensive previous analyses and simulations by many researchers for frictionless particles must be reconsidered in the light of our work. We also made the first detailed comparison between experiment and the predictions of continuum theory for granular media (hydrodynamic equations). We found that shock waves easily form in granular flows since the speed of sound waves (pressure fluctuations) in a granular gas is small, typically 10 cm, while flow velocities are easily an order of magnitude larger. Our measurements on vertically oscillating granular layers led to the development of a novel technique for continuously separating particles of different sizes. Our study of craters formed by the impact of a projectile in a granular medium showed, surprisingly, that the time taken for a projectile to come to a rest in the granular layer is independent of the projectile’s impact energy. Another study supported by this grant examined a vertically oscillating layer of a mixture of cornstarch and water. The discovery of stable holes in the mixture was reported widely in the popular press, e.g., Science News [15 May 2004], “Imaging poking a liquid to create holes that persist like the holes in Swiss cheese. Incredible as that might sound, a group of scientists has done it.” Further experiments on glass spheres in an aqueous solution yielded the same holey fluid phenomenon, supporting our conjecture that such holes may occur in dense concentrations of particles in solution in industrial applications.

Swinney, Harry L.

2007-07-11

290

Particle number size distribution in the eastern Mediterranean: Formation and growth rates of ultrafine airborne atmospheric particles  

NASA Astrophysics Data System (ADS)

Particle number concentration was measured between June 2009 and June 2010 at Akrotiri research station in a rural/suburban region of western Crete (Greece). Overall, the available data covered 157 days during the aforementioned period of measurements. The objectives were to study the number size distribution characteristics of ambient aerosols and furthermore to identify new particle formation events and to evaluate particle formation rates and growth rates of the newborn particles. Aerosol particles with mobility diameters between 10 and 1100 nm were measured using a Scanning Mobility Particle Sizer (SMPS) system. Measurements were performed at ambient relative humidities. The median total particle number concentration was 525 #/cm3 whereas the number concentration ranged between 130 #/cm3 and 9597 #/cm3. The average percentage of particles with diameters between 10 nm and 100 nm (N10–100) to total particles was 53% during summer and spring, but reached 80% during winter. Maximum average contribution of nano-particles (10 nm < Dp < 50 nm) to total particles was recorded also in winter and was attributed partly to the effect of local heating. Furthermore, back trajectories (HYSPLIT model) showed that different air mass origins are linked to different levels of particle number concentrations, with higher values associated with air masses passing from polluted areas before reaching the Akrotiri station. Modal analysis of the measured size distribution data revealed a strong nucleation mode during winter (15–25 nm), which can be correlated with emissions from local sources (domestic heating). The nucleation mode was observed also during the spring campaigns and was partly linked to new particle formation events. On the contrary, an accumulation mode (80–120 nm) prevailed in the measurements during summer campaigns, when the station area was influenced by polluted air masses arriving mainly from Eastern Europe. In total, 13 new particle formation events were recorded during the 157 days of measurements. Nucleation events were associated with low values of N100 particle number concentration and reduced coagulation sinks. Mean growth and formation rates were calculated and showed values equal to 6 nm hr?1 and 13 cm?3 s?1, respectively.

Kopanakis, I.; Chatoutsidou, S. E.; Torseth, K.; Glytsos, T.; Lazaridis, M.

2013-10-01

291

Atmospheric Data over a Solar Cycle: No Connection between Galactic Cosmic Rays and Particle Formation in Boreal Forest  

NASA Astrophysics Data System (ADS)

Aerosol particles affect the Earth’s radiative balance by directly scattering and absorbing solar radiation and, indirectly, through their activation into cloud droplets. Both effects are known with considerable uncertainty only, and translate into even bigger uncertainties in future climate predictions. More than a decade ago, variations in galactic cosmic rays were suggested to closely correlate with variations in atmospheric cloud cover and therefore constitute a driving force behind aerosol-cloud-climate interactions. Later, the enhancement of atmospheric aerosol particle formation by ions generated from cosmic rays was proposed as a physical mechanism explaining this correlation. Here, we report unique observations on atmospheric aerosol formation based on measurements at the SMEAR II station, Finland, over a solar cycle (years 1996-2008) that shed new light on these presumed relationships. Our analysis shows that none of the quantities related to aerosol formation correlates with the cosmic ray-induced ionisation intensity (CRII, see Fig. 1). We also examined the contribution of ions to new particle formation on the basis of novel ground-based and airborne observations. A consistent result is that ion-induced formation contributes typically less than 10% to the number of new particles, which would explain the missing correlation between CRII and aerosol formation. Our main conclusion is that galactic cosmic rays appear to play a minor role for atmospheric aerosol formation, and so for the connected aerosol-climate effects as well. Figure 1. Particle formation events and CRII at the SMEAR II station in Hyytiälä, Finland during 1996-2008.

Riipinen, I.; Kulmala, M. T.; Nieminen, T.; Hulkkonen, M.; Sogacheva, L.; Manninen, H.; Paasonen, P.; Petdjd, T. T.; Dal Maso, M.; Aalto, P.; Viljanen, A.; Usoskin, I.; Vainio, R. O.; Mirme, S.; Mirme, A.; Minikin, A.; Petzold, A.; Horrak, U.; Plass-Duelmer, C.; Birmili, W.; Kerminen, V.

2009-12-01

292

Adaptive smoothed particle hydrodynamics for high strain hydrodynamics with material strength  

Microsoft Academic Search

This paper presents the implementation of an adaptive smoothed particle hydrodynamics (ASPH) method for high strain Lagrangian\\u000a hydrodynamics with material strength. In ASPH, the isotropic kernel in the standard SPH is replaced with an anisotropic kernel\\u000a whose axes evolve automatically to follow the mean particle spacing as it varies in time, space, and direction around each\\u000a particle. Except for the

M. B. Liu; G. R. Liu; K. Y. Lam

2006-01-01

293

Phase inversion of particle-stabilized materials from foams to dry water  

Microsoft Academic Search

Small particles attached to liquid surfaces arise in many products and processes, including crude-oil emulsions and food foams and in flotation, and there is a revival of interest in studying their behaviour. Colloidal particles of suitable wettability adsorb strongly to liquid-liquid and liquid-vapour interfaces, and can be sole stabilizers of emulsions and foams, respectively. New materials, including colloidosomes, anisotropic particles

Bernard P. Binks; Ryo Murakami

2006-01-01

294

Effects of lossy, layered filler particles on the bulk permittivity of a composite material  

NASA Astrophysics Data System (ADS)

The ability to control the frequency at which a dielectric material exhibits maximum loss (the relaxation frequency) is of interest in telecommunications and radar absorption. A theoretical investigation of the behaviour of the complex bulk permittivity of a composite material with coated, spheroidal filler particles is presented. In the model, the filler particles are replaced mathematically by electric multipole sources located at their centres (Harfield N 2000 J. Mater. Sci. 35 5809-16). It is shown how factors such as particle shape, orientation with respect to the applied electric field, thickness of coating and permittivity value of the individual phases influences the bulk permittivity of the composite material. For a composite with coated filler particles, one or two relaxation frequencies may be observed. Employing the theory of Pauly and Schwan (Hanai T 1968 Electrical properties of emulsions Emulsion Science ed P Sherman (London: Academic)), particular attention is paid to the way in which the relaxation frequencies are affected by the material parameters.

Bowler, N.

2004-02-01

295

Study of Particle Rebound Characteristics and Material Erosion at High Temperature.  

National Technical Information Service (NTIS)

The rebound characteristics of 15 micron mean diameter fly ash particles impacting several target materials were measured using Laser Doppler Velocimetry (LDV). Detailed results including the effects of various parameters were given in a previous report. ...

W. Tabakoff A. Hamed H. Eroglu

1988-01-01

296

A particle size distribution analysis of used HPLC column packing material  

Microsoft Academic Search

Particle size distribution analysis and scanning electron microscopy (SEM) were carried out on eight used HPLC columns containing either irregular silica based, spherical silica based or spherical polymer based packing material. Particle size distributions of the used irregular silica based columns were at least bimodat at the outlet ends and either biomodal or log-normal at the inlet ends with regular

T. D. Wilson; D. M. Simmons

1993-01-01

297

Use of natural particles for the removal of paint from aeronautical composite materials  

Microsoft Academic Search

Paint removal by blasting and its effects on the surface morphology of aeronautical composite materials are investigated. An ideal combination of the parameters for mechanical paint removal by blasting such as particle type, size, velocity and angle of incidence yields a stripped aircraft skin substrate with minimal or no damage. Natural particles, specifically white corn flour, seem to be a

Thu-Ha Guy; Hamid M. Lankarani; Jorge E. Talia

1991-01-01

298

Single particle friction on blister packaging materials used in dry powder inhalers  

Microsoft Academic Search

Using atomic force microscopy (AFM) the adhesion and sliding friction behaviour of single lactose particles attached directly to AFM cantilevers has been studied. Measurements were made on the two sides of a blister packaging material used in dry powder inhalers (DPI). Although no significant differences in adhesion were observed, clear differences in particle friction were evident, where one side offers

Matthew J. Bunker; Martyn C. Davies; Xinyong Chen; Michael B. James; Clive J. Roberts

2006-01-01

299

TCT characterization of different semiconductor materials for particle detection  

NASA Astrophysics Data System (ADS)

The development of digital semiconductor based X-ray detectors necessitates a detailed understanding of the applied sensor material. Under this premise a broad-band transient current technique (TCT) setup has been developed and used to characterize different semiconductors. The measurements are based on the generation of electrical charges within the sensor material and the subsequent time-resolved analysis of the charge carrier movement. From the recorded current pulses the charge collection efficiency, the charge carrier mobility and the electric field profile have been extracted. The examined materials are silicon p in n diodes, ohmic and Schottky contacted CdTe detectors, CdZnTe (CZT) crystals with Schottky contacts as well as two single-crystal CVD-diamonds.

Fink, J.; Lodomez, P.; Krüger, H.; Pernegger, H.; Weilhammer, P.; Wermes, N.

2006-09-01

300

Role of ceramic particles for developing wear resistant materials  

NASA Astrophysics Data System (ADS)

The present work emphasises on the study of two different ceramic particulates embedded in the soft alloy. The material is developed by spray atomization. The two ceramic particulates used for the study are SiC and ZrSiO4. The effect of particulate on hardness has been analyzed. Moreover, wear characteristics of the both developed material has been compared with the monolithic as cast alloy. The results of the ZrSiO4 reinforced composite shows lesser wear rate at 50°C and 150°C at low as well as high loads as compared to SiC reinforced Al-alloy.

Kaur, Kamalpreet; Pandey, O. P.

2013-06-01

301

The size effect of zircon particles on the friction characteristics of brake lining materials  

Microsoft Academic Search

This work investigated the effect of zircon particle size on the friction characteristics of brake lining materials. Four different sizes of commercially used zircon particles (nominally 1?m, 6?m, 75?m, and 150?m in diameter) were used to produce non-steel type lining materials. We focused on the level of the friction coefficient, the oscillation of friction force, and wear resistance of the

K. H. Cho; H. Jang; Y.-S. Hong; S. J. Kim; R. H. Basch; J. W. Fash

2008-01-01

302

Physical properties and structure of fine core–shell particles used as packing materials for chromatography  

Microsoft Academic Search

The recent development of new brands of packing materials made of fine porous-shell particles, e.g., Halo and Kinetex, has brought great improvements in potential column efficiency, demanding considerable progress in the design of chromatographic instruments. Columns packed with Halo and Kinetex particles provide minimum values of their reduced plate heights of nearly 1.5 and 1.2, respectively. These packing materials have

Fabrice Gritti; Irene Leonardis; Jude Abia; Georges Guiochon

2010-01-01

303

Interactions of mineral dust with pollution and clouds: An individual-particle TEM study of atmospheric aerosol from Saudi Arabia  

NASA Astrophysics Data System (ADS)

Aerosol particles from desert dust interact with clouds and influence climate on regional and global scales. The Riyadh (Saudi Arabia) aerosol campaign was initiated to study the effects of dust particles on cloud droplet nucleation and cloud properties. Here we report the results of individual-particle studies of samples that were collected from an aircraft in April 2007. We used analytical transmission electron microscopy, including energy-dispersive X-ray spectrometry, electron diffraction, and imaging techniques for the morphological, chemical, and structural characterization of the particles. Dust storms and regional background conditions were encountered during four days of sampling. Under dusty conditions, the coarse (supermicrometer) fraction resembles freshly crushed rock. The particles are almost exclusively mineral dust grains and include common rock-forming minerals, among which clay minerals, particularly smectites, are most abundant. Unaltered calcite grains also occur, indicating no significant atmospheric processing. The particles have no visible coatings but some contain traces of sulfur. The fine (submicrometer) fraction is dominated by particles of anthropogenic origin, primarily ammonium sulfate (with variable organic coating and some with soot inclusions) and combustion-derived particles (mostly soot). In addition, submicrometer, iron-bearing clay particles also occur, many of which are internally mixed with ammonium sulfate, soot, or both. We studied the relationships between the properties of the aerosol and the droplet microphysics of cumulus clouds that formed above the aerosol layer. Under dusty conditions, when a large concentration of coarse-fraction mineral particles was in the aerosol, cloud drop concentrations were lower and droplet diameters larger than under regional background conditions, when the aerosol was dominated by submicrometer sulfate particles.

Pósfai, Mihály; Axisa, Duncan; Tompa, Éva; Freney, Evelyn; Bruintjes, Roelof; Buseck, Peter R.

2013-03-01

304

Hygroscopic properties and water-soluble volume fraction of atmospheric particles in the diameter range from 50 nm to 3.8 mum during LACE 98  

Microsoft Academic Search

Hygroscopic properties of atmospheric aerosol particles in the Aitken, large, and giant particle range were studied during the Lindenberg Aerosol Characterization Experiment (LACE 98) in a rural area 80 km southeast of Berlin. The hygroscopic behavior of Aitken particles were determined in situ in four size classes (50, 100, 150, 250 nm) with a Hygroscopic Tandem Differential Mobility Analyzer for

B. Busch; K. Kandler; L. Schütz; C. Neusüß

2002-01-01

305

Vertical distribution of atmospheric particles and water vapor densities in the free troposphere: Lidar measurement in spring and summer in Nagoya, Japan  

Microsoft Academic Search

Density distributions of atmospheric water vapor and aerosol particles in the troposphere were observed from April to August 1994 in Nagoya, Japan, with a Raman-scattering lidar. In spring, highly concentrated particle layers were frequently observed in the free troposphere, and in summer air mass with high relative humidity was detected. These suggest the possibility that density distributions of aerosol particles

S. A. Kwon; Y. Iwasaka; T. Shibata; T. Sakai

1997-01-01

306

Generation of sub-micron particles and secondary pollutants from building materials by ozone reaction  

Microsoft Academic Search

This study reports results from two different experiments examining reactions between ozone and common building materials that can lead to the formation of secondary products and particulate-phase materials. Monitored species include sub-micron particles and volatile organic compounds (VOCs). In the first set of experiments, various building materials were placed in a 20L stainless-steel chamber and exposed to ozone. The materials

Taisuke Aoki; Shin-ichi Tanabe

2007-01-01

307

Free and combined amino compounds in atmospheric fine particles (PM 2.5) and fog waters from Northern California  

Microsoft Academic Search

Atmospheric fine particles (PM2.5) collected during August 1997–July 1998 and wintertime fog waters collected during 1997–1999 at Davis, California were analyzed for free and combined amino compounds. In both PM2.5 and fog waters, the average concentrations of combined amino compounds (CAC, e.g., proteins and peptides) were generally 4–5 times higher than those of free amino compounds (FAC, i.e., amino acids

Qi Zhang; Cort Anastasio

2003-01-01

308

Acoustic properties and durability of liner materials at non-standard atmospheric conditions  

NASA Astrophysics Data System (ADS)

This report documents the results of an experimental study on how acoustic properties of certain absorbing liner materials are affected by nonstandard atmospheric conditions. This study was motivated by the need to assess risks associated with incorporating acoustic testing capability in wind tunnels with semicryogenic high Reynolds number aerodynamic and/or low pressure capabilities. The study consisted of three phases: 1) measurement of acoustic properties of selected liner materials at subatmospheric pressure conditions, 2) periodic cold soak and high pressure exposure of liner materials for 250 cycles, and 3) determination of the effect of periodic cold soak on the acoustic properties of the liner materials at subatmospheric conditions and the effect on mechanical resiliency. The selected liner materials were Pyrell foam, Fiberglass, and Kevlar. A vacuum facility was used to create the subatmospheric environment in which an impedance tube was placed to measure acoustic properties of the test materials. An automated cryogenic cooling system was used to simulate periodic cold soak and high pressure exposure. It was found that lower ambient pressure reduced the absorption effectiveness of the liner materials to varying degrees. Also no significant change in the acoustic properties occurred after the periodic cold soak. Furthermore, mechanical resiliency tests indicated no noticeable change.

Ahuja, K. K.; Gaeta, R. J., Jr.; Hsu, J. S.

1994-11-01

309

Applications of Miniature Remotely Guided Aircraft to Monitoring and Sampling Atmospheric Pollutants and Toxic\\/Hazardous Materials  

Microsoft Academic Search

A two-year research project has been completed involving the development, and assessment of an atmospheric sampling system based on miniature remotely guided aircraft. The system is designed for short duration sampling of the atmosphere below 1,000 meters for pollutant, toxic, and hazardous materials. The development focused on two sampling methodologies to demonstrate the viability of the system; (a) gamma radiation

William W. Lund; Ronald Starkey

1990-01-01

310

LWS Studies of Gamma Rays Produced in the Earth's Atmosphere by Cosmic Rays and Solar Energetic Particle Events  

NASA Astrophysics Data System (ADS)

We summarize a three-year study of atmospheric gamma-ray line measurements conducted under the Living With a Star program. The observations were made by instruments on three satellites: SMM, Yohkoh, and RHESSI. They detected the 511-keV positron annihilation line produced in electromagnetic showers and de- excitation lines from 14N at 728, 1635, 2313, 3890, and 5106 keV, and from 16O at 6129 keV, as well as spallation lines near 4440 keV from 12C and 11B produced by neutron and proton interactions on Earth's atmosphere. The SMM studies focused on the variation of the cosmic-ray produced lines as a function of magnetic rigidity and solar cycle modulation. We found that the power-law spectral index of the secondary neutrons was relatively constant for the range of times and rigidity intervals sampled. The Yohkoh and RHESSI studies focused on atmospheric gamma rays produced by solar energetic particles interacting in the Earth's atmosphere following flares on 2000 July 14 and 2002 April 21, respectively. The SEP spectra estimated using gamma-ray line ratios were of comparable hardness with the spectrum measured by SMM for the 1989 October 20 intense event, consistent with measurements in space. Improved cross sections for the production of the nuclear lines offer better estimates of the spectra of SEPs impacting the atmosphere. Since the early observations, RHESSI has observed several more SEP events producing detectable fluxes of atmospheric gamma rays. These include large particle events in 2003 October/November and 2005 January.

Murphy, R. J.; Share, G. H.; Kozlovsky, B. Z.

2006-12-01

311

Automated technologies needed to prevent radioactive materials from reentering the atmosphere  

NASA Astrophysics Data System (ADS)

Project SIREN (Search, Intercept, Retrieve, Expulsion Nuclear) has been created to identify and evaluate the technologies and operational strategies needed to rendezvous with and capture aerospace radioactive materials (e.g., a distressed or spent space reactor core) before such materials can reenter the terrestrial atmosphere and then to safely move these captured materials to an acceptable space destination for proper disposal. A major component of the current Project SIREN effort is the development of an interactive technology model (including a computerized data base) that explores in building block fashion the interaction of the technologies and procedures needed to successfully accomplish a SIREN mission. This SIREN model will include appropriate national and international technology elements-both contemporary and projected into the next century. To permit maximum flexibility and use, the SIREN technology data base is being programmed for use on 386-class PC's.

Buden, David; Angelo, Joseph A., Jr.

312

A comparative study of the surface recombination of nitrogen atoms on various materials at atmospheric pressure  

NASA Astrophysics Data System (ADS)

The surface recombination of nitrogen atoms on various materials was investigated at atmospheric pressure. The afterglows of pure nitrogen discharge are injected into a surface loss test unit, whose path wall is composed of the materials to be examined. Measurement of the nitrogen atom densities at several points in the flowing afterglows reveals the temporal decay characteristics. The results are compared with two-dimensional numerical simulations to obtain the surface loss probability ?. Among the seven materials we studied (stainless steel, aluminium, titanium, alumina, Pyrex glass, aluminium nitride and boron nitride), stainless steel was found to have the highest ? value: 1.8 × 10-3 the lowest was for boron nitride: 4.8 × 10-5. The dependence of ? on surface roughness and temperature was also examined.

Oinuma, Gaku; Inanaga, Yasutaka; Tanimura, Yasuhiro; Kuzumoto, Masaki; Tabata, Yoichiro; Watanabe, Kensuke

2010-06-01

313

Thermal transients and convective particle motion in dense granular materials.  

PubMed

The mechanism of dry granular convection within dense granular flows is mostly neglected by current analytical heat equations describing such materials, for example, in geophysical analyses of shear gouge layers of earthquake and landslide rupture planes. In dry granular materials, the common assumption is that conduction by contact overtakes any other mode of heat transfer. Conversely, we discover that transient correlated motion of heated grains can result in a convective heat flux normal to the shear direction up to 3-4 orders magnitude larger than by contact conduction. Such a thermal efficiency, much higher than that of water, is appealing and might be common to other microscopically structured fluids such as granular pastes, emulsions, and living cells. PMID:21231360

Rognon, P; Einav, I

2010-11-17

314

Ice nucleation by surrogates for atmospheric mineral dust and mineral dust/sulfate particles at cirrus temperatures  

NASA Astrophysics Data System (ADS)

This study examines the potential role of some types of mineral dust and mineral dust with sulfuric acid coatings as heterogeneous ice nuclei at cirrus temperatures. Commercially-available nanoscale powder samples of aluminum oxide, alumina-silicate and iron oxide were used as surrogates for atmospheric mineral dust particles, with and without multilayer coverage of sulfuric acid. A sample of Asian dust aerosol particles was also studied. Measurements of ice nucleation were made using a continuous-flow ice-thermal diffusion chamber (CFDC) operated to expose size-selected aerosol particles to temperatures between -45 and -60°C and a range of relative humidity above ice-saturated conditions. Pure metal oxide particles supported heterogeneous ice nucleation at lower relative humidities than those required to homogeneously freeze sulfuric acid solution particles at sizes larger than about 50 nm. The ice nucleation behavior of the same metal oxides coated with sulfuric acid indicate heterogeneous freezing at lower relative humidities than those calculated for homogeneous freezing of the diluted particle coatings. The effect of soluble coatings on the ice activation relative humidity varied with the respective uncoated core particle types, but for all types the heterogeneous freezing rates increased with particle size for the same thermodynamic conditions. For a selected size of 200 nm, the natural mineral dust particles were the most effective ice nuclei tested, supporting heterogeneous ice formation at an ice relative humidity of approximately 135%, irrespective of temperature. Modified homogeneous freezing parameterizations and theoretical formulations are shown to have application to the description of heterogeneous freezing of mineral dust-like particles with soluble coatings.

Archuleta, C. M.; Demott, P. J.; Kreidenweis, S. M.

2005-10-01

315

New Particle Formation Observed During the HIAPER Progressive Science Missions: Atmospheric Dynamics, Surface Area, and Photochemisty on Nucleation  

NASA Astrophysics Data System (ADS)

High number concentrations of ultrafine particles were measured at the altitudes up to 14 km and latitudes from 18 ºN 52 ºN during the HIAPER Progressive Science Missions in December 2006. Particle sizes in the diameter from 4 to 2000 nm range were measured with the University of Denver nuclei mode aerosol sizing spectrometer (NMASS) and forward cavity aerosol spectrometer (FCAS). (1) About > 85 % of the total particles showed new particle formation feature, with the number concentrations from 4 to 9 nm of 670 ± 1270 cm-3 and total number concentrations of 920 ± 1470 cm-3. Our results show that particle formation takes place in the typical upper troposphere and lower stratosphere conditions. (2) Enhanced new particle formation was observed during the midlatitude tropopause folding where stratosphere and troposphere exchange takes place. Our observations are consistent with the sulfuric acid water binary homogeneous nucleation calculations, showing that atmospheric dynamics-induced air mixing can enhance nucleation rates substantially [Nilsson et al., 2003]. (3) Most of new particle formation events measured in the upper troposphere were also associated with strong vertical motion air uplifting that brings higher concentrations of SO2 and water vapor to higher altitudes where temperatures are lower, which creates an ideal condition for nucleation. (4) Surface area of preexisting aerosol particles is a critical factor for new particle formation. However, the measured ultrafine particle concentrations are a function of the ratio of sun exposure hours to surface area (when SO2 concentrations remain relatively constant), rather than a function of surface area alone.

Benson, D.; Young, L.; Montanaro, W.; Lee, S.; Wilson, J.; Jensen, J.; Stith, J.; Campos, T.; Rogers, D.

2006-12-01

316

Seasonal variations of number size distributions and mass concentrations of atmospheric particles in Beijing  

NASA Astrophysics Data System (ADS)

Particle number and mass concentrations were measured in Beijing during the winter and summer periods in 2003, together with some other parameters including black carbon (BC) and meteorological conditions. Particle mass concentrations exhibited low seasonality, and the ratio of PM2.5/PM10 in winter was higher than that in summer. Particle number size distribution (PSD) was characterized by four modes and exhibited low seasonality. BC was well correlated with the number and mass concentrations of accumulation and coarse particles, indicating these size particles are related to anthropogenic activities. Particle mass and number concentrations (except ultra-fine and nucleation particles) followed well the trends of BC concentration for the majority of the day, indicating that most particles were associated with primary emissions. The diurnal number distributions of accumulation and coarse mode particles were characterized by two peaks.

Yu, Jianhua; Guinot, Benjamin; Yu, Tong; Wang, Xin; Liu, Wenqing

2005-06-01

317

Models and methods for automated material identification in hyperspectral imagery acquired under unknown illumination and atmospheric conditions  

Microsoft Academic Search

The spectral radiance measured by an airborne imaging spectrometer for a material on the Earth's surface depends strongly on the illumination incident of the material and the atmospheric conditions. This dependence has limited the success of material-identification algorithms that rely on hyperspectral image data without associated ground-truth information. In this paper, the authors use a comprehensive physical model to show

Glenn Healey; David Slater

1999-01-01

318

Gas-particle interactions above a Dutch heathland: II. Concentrations and surface exchange fluxes of atmospheric particles  

NASA Astrophysics Data System (ADS)

Size-dependent particle number fluxes measured by eddy-covariance (EC) and continuous fluxes of ammonium (NH4+) measured with the aerodynamic gradient method (AGM) are reported for a Dutch heathland. Daytime deposition velocities (Vd) by EC with peak values of 5 to 10 mm s-1 increased with particle diameter (dp) over the range 0.1-0.5 ?m, and are faster than predicted by current models. With a mean Vd of 2.0 mm s-1 (daytime: 2.7; night-time 0.8 mm s-1) NH4+ fluxes by AGM are overall in agreement with former measurements and NH4+-N dry deposition amounts to 20% of the dry input of NH3-N over the measurement period. These surface exchange fluxes are analyzed together with simultaneous gas-phase flux measurements for indications of gas-particle interactions. On warm afternoons the apparent fluxes of acids and aerosol above the heathland showed several coinciding anomalies, all of which are consistent with NH4+ evaporation during deposition: (i) canopy resistances for HNO3 and HCl of up to 100 s m-1, (ii) simultaneous particle emission of small particles (Dp<0.18 ?m) and deposition of larger particles (Dp>0.18 ?m), (iii) NH4+ deposition faster than derived from size-distributions and size-segregated EC particle fluxes. These observations coincide with the observations of (i) surface concentration products of NH3 and HNO3 well below the thermodynamic equilibrium value and (ii) Damköhler numbers that indicate chemical conversion to be sufficiently fast to modify exchange fluxes. The measurements imply a removal rate of volatile NH4+ of 3-30×10-6s-1 averaged over the 1 km boundary-layer, while NH3 deposition is underestimated by typically 20 ng m-2 s-1 (28%) and flux reversal may occur.

Nemitz, E.; Sutton, M. A.; Wyers, G. P.; Otjes, R. P.; Mennen, M. G.; van Putten, E. M.; Gallagher, M. W.

2004-03-01

319

Gas-particle interactions above a Dutch heathland: II. Concentrations and surface exchange fluxes of atmospheric particles  

NASA Astrophysics Data System (ADS)

Size-dependent particle number fluxes measured by eddy-covariance (EC) and continuous fluxes of ammonium (NH4+) measured with the aerodynamic gradient method (AGM) are reported for a Dutch heathland. Daytime deposition velocities (Vd) by EC with peak values of 5 to 10 mm s-1 increased with particle diameter (dp) over the range 0.1-0.5 µm, and are faster than predicted by current models. With a mean Vd of 2.0 mm s-1 (daytime: 2.7; night-time 0.8 mm s-1) NH4+ fluxes by AGM are overall in agreement with former measurements and NH4+-N dry deposition amounts to 20% of the dry input of NH3-N over the measurement period. These surface exchange fluxes are analyzed together with simultaneous gas-phase flux measurements for indications of gas-particle interactions. On warm afternoons the apparent fluxes of acids and aerosol above the heathland showed several coinciding anomalies, all of which are consistent with NH4+ evaporation during deposition: (i) canopy resistances for HNO3 and HCl of up to 100 s m-1, (ii) simultaneous particle emission of small particles (Dp<0.18 µm) and deposition of larger particles (Dp>0.18 µm), (iii) NH4+ deposition faster than derived from size-distributions and size-segregated EC particle fluxes. These observations coincide with the observations of (i) surface concentration products of NH3 and HNO3 well below the thermodynamic equilibrium value and (ii) Damköhler numbers that indicate chemical conversion to be sufficiently fast to modify exchange fluxes. The measurements imply a removal rate of volatile NH4+ of 3-30×10-6 s-1 averaged over the 1 km boundary-layer, while NH3 deposition is underestimated by typically 20 ng m-2 s-1 (28%) and flux reversal may occur.

Nemitz, E.; Sutton, M. A.; Wyers, G. P.; Otjes, R. P.; Mennen, M. G.; van Putten, E. M.; Gallagher, M. W.

2004-07-01

320

ACIDIC DEPOSITION AND THE CORROSION AND DETERIORATION OF MATERIALS IN THE ATMOSPHERE: A BIBLIOGRAPHY, 1880-1982  

EPA Science Inventory

The bibliography contains more than 1300 article citations and abstracts on the effects of acidic deposition, air pollutants, and biological and meteorological factors on the corrosion and deterioration of materials in the atmosphere. The listing includes citations for the years ...

321

Materials performance in the atmospheric fluidized-bed cogeneration air heater experiment  

SciTech Connect

The Atmospheric Fluidized-Bed Cogeneration Air Heater Experiment (ACAHE) sponsored by the US Department of Energy (DOE) was initiated to assess the performance of various heat-exchanger materials to be used in fluidized-bed combustion air heater systems. Westinghouse Electric Corporation, through subcontracts with Babcock & Wilcox, Foster Wheeler, and ABB Combustion Engineering Systems, prepared specifications and hardware for the ACAHE tests. Argonne National Laboratory contracted with Rockwell International to conduct tests in the DOE atmospheric fluidized-bed combustion facility. This report presents an overview of the project, a description of the facility and the test hardware, the test operating conditions, a summary of the operation, and the results of analyzing specimens from several uncooled and cooled probes exposed in the facility. Extensive microstructural analyses of the base alloys, claddings, coatings, and weldments were performed on specimens exposed in several probes for different lengths of time. Alloy penetration data were determined for several of the materials as a function of specimen orientation and the exposure location in the combustor. Finally, the data were compared with earlier laboratory test data, and the long-term performance of candidate materials for air-heater applications was assessed.

Natesan, K.; Podolski, W.; Wang, D.Y.; Teats, F.G. [Argonne National Lab., IL (United States); Gerritsen, W.; Stewart, A.; Robinson, K. [Rockwell International Corp., Canoga Park, CA (United States)

1991-02-01

322

Materials performance in the atmospheric fluidized-bed cogeneration air heater experiment  

SciTech Connect

The Atmospheric Fluidized-Bed Cogeneration Air Heater Experiment (ACAHE) sponsored by the US Department of Energy (DOE) was initiated to assess the performance of various heat-exchanger materials to be used in fluidized-bed combustion air heater systems. Westinghouse Electric Corporation, through subcontracts with Babcock Wilcox, Foster Wheeler, and ABB Combustion Engineering Systems, prepared specifications and hardware for the ACAHE tests. Argonne National Laboratory contracted with Rockwell International to conduct tests in the DOE atmospheric fluidized-bed combustion facility. This report presents an overview of the project, a description of the facility and the test hardware, the test operating conditions, a summary of the operation, and the results of analyzing specimens from several uncooled and cooled probes exposed in the facility. Extensive microstructural analyses of the base alloys, claddings, coatings, and weldments were performed on specimens exposed in several probes for different lengths of time. Alloy penetration data were determined for several of the materials as a function of specimen orientation and the exposure location in the combustor. Finally, the data were compared with earlier laboratory test data, and the long-term performance of candidate materials for air-heater applications was assessed.

Natesan, K.; Podolski, W.; Wang, D.Y.; Teats, F.G. (Argonne National Lab., IL (United States)); Gerritsen, W.; Stewart, A.; Robinson, K. (Rockwell International Corp., Canoga Park, CA (United States))

1991-02-01

323

Particle induced damage on heads and discs due to fine particles of different materials  

Microsoft Academic Search

Fine particles of aluminum, stainless steel, silicon, slider ceramic (Al2O3-TiC) and sputtered alumina were introduced at the head\\/disc interface of hard disc drives. Experiments were conducted with discs made from aluminum and glass substrates. Glass substrates were much harder than aluminum substrates. It was found that the type of damage introduced on the disc and slider was to some extent

Lihong Zhang; Ramesh Koka; Yewwah Yuen; Edwin Lam

1999-01-01

324

SCIENTIFIC NOTE: On the transport of charged particles through spongy materials  

Microsoft Academic Search

Monte Carlo calculations are reported. These calculations show the anticipated decreased probability of the paths being found in the material for conditions of grazing incidence. However, at slightly larger angles of incidence, they show an increased probability of the trajectory being within the material. When averaged over randomly-oriented incident angles, these two effects exactly cancel. Thus, charged particles traversing a

R. M. Henkelman; B. R. Preiss

1981-01-01

325

Critical impact velocity in the solid particles impact erosion of metallic materials  

Microsoft Academic Search

Solid particles impact erosion of metallic materials proceeds through two kinds of damage processes. One is the removal of material due to repeated plastic deformation, and the other is cutting. These processes occur simultaneously and the ratio of each contribution to the total damage depends not only on the impact angle (the predominant parameter) but also on the impact velocity.

Akihiro Yabuki; Kazuo Matsuwaki; Masanobu Matsumura

1999-01-01

326

Squeeze flow characterization of particle-filled polymeric materials through image correlation  

Microsoft Academic Search

Particle-filled polymeric materials are common choices for thermal interface materials (TIMs). During assembly, TIMs are applied between the surfaces across which heat must be transported. The goal of the present work is to develop a test procedure that is consistent with the length scales characteristic of real thermal interfaces. A mechanical tester (Instron 5848 Micromechanical Tester) is employed with closed-loop

Nikhil Bajaj; Ganesh Subbarayan; Suresh V. Garimella

2010-01-01

327

The simulation of implantation of heavy charged particles in a crystalline material  

Microsoft Academic Search

We have studied the channeling effect in the ion implantation by simulating the collision of heavy charged particles with a crystalline material. In order to determine the penetration depth of fast heavy ions in crystalline material, we modified a model from pervious work and studied a situation where heavy As and P ions impinging on a crystal Si?100? surface. A

Önder Kabadayi

2009-01-01

328

Acoustical properties of materials made of vegetable particles with several scales of porosity  

Microsoft Academic Search

This article is devoted to the acoustical properties of hemp concrete, a “green” building material. In the study, hemp concretes made of different binders and different kinds of particles were characterised, and then modeled using equivalent-fluid models. Further, it is shown that the sound absorption of these materials can be controlled and significantly enhanced by means of suitable constituents and

P. Glé; E. Gourdon; L. Arnaud

2011-01-01

329

Impact of different energies of precipitating particles on NOx generation in the middle and upper atmosphere during geomagnetic storms  

NASA Astrophysics Data System (ADS)

Energetic particle precipitation couples the solar wind to the Earth's atmosphere and indirectly to Earth's climate. Ionisation and dissociation increases, due to particle precipitation, create odd nitrogen (NOx) and odd hydrogen (HOX) in the upper atmosphere, which can affect ozone chemistry. The long-lived NOx can be transported downwards into the stratosphere, particularly during the polar winter. Thus, the impact of NOx is determined by both the initial ionisation production, which is a function of the particle flux and energy spectrum, as well as transport rates. In this paper, we use the Sodankylä Ion and Neurtal Chemistry (SIC) model to simulate the production of NOx from examples of the most representative particle flux and energy spectra available today of solar proton events (SPE), auroral energy electrons, and relativistic electron precipitation (REP). Large SPEs are found to produce higher initial NOx concentrations than long-lived REP events, which themselves produce higher initial NOx levels than auroral electron precipitation. Only REP microburst events were found to be insignificant in terms of generating NOx. We show that the Global Ozone Monitoring by Occultation of Stars (GOMOS) observations from the Arctic winter 2003-2004 are consistent with NOx generation by a combination of SPE, auroral altitude precipitation, and long-lived REP events.

Turunen, Esa; Verronen, Pekka T.; Seppälä, Annika; Rodger, Craig J.; Clilverd, Mark A.; Tamminen, Johanna; Enell, Carl-Fredrik; Ulich, Thomas

2009-07-01

330

Atmospheric Black Carbon: Chemical Bonding and Structural Information of Individual Aerosol Particles  

Microsoft Academic Search

The formation of aerosols from both natural and anthropogenic sources affects the Earth's temperature and climate by altering the radiative properties of the atmosphere. Aerosols containing black carbon (BC) that are released into the atmosphere from the burning of biomass, natural fires and the combustion of coals, diesel and jet fuels, contribute a large positive component to this radiative forcing,

M. K. Gilles; A. V. Tivanski; R. J. Hopkins; B. D. Marten

2006-01-01

331

Atmospheric particle formation events at Värriö measurement station in Finnish Lapland 1998-2002  

Microsoft Academic Search

During the calendar years 1998-2002, 147 clear 8nm diameter particle formation events have been identified at the SMEAR I station in Värriö, northern Finland. The events have been classified in detail according to the particle formation rate, growth rate, event starting time, different trace gas concentrations and pre-existing particle concentrations as well as various meteorological conditions. The frequency of particle

H. Vehkamäki; M. Dal Maso; T. Hussein; R. Flanagan; A. Hyvärinen; J. Lauros; P. Merikanto; M. Mönkkönen; K. Pihlatie; K. Salminen; L. Sogacheva; T. Thum; T. M. Ruuskanen; P. Keronen; P. P. Aalto; P. Hari; Ü. Rannik; M. Kulmala

2004-01-01

332

Anthropogenic Influence on Secondary Aerosol Formation and Total Water-Soluble Carbon on Atmospheric Particles  

NASA Astrophysics Data System (ADS)

On a global scale, the atmosphere is an important source of nutrients, as well as pollutants, because of its interfaces with soil and water. Important compounds in the gaseous phase are in both organic and inorganic forms, such as organic acids, nitrogen, sulfur and chloride. In spite of the species in gas form, a huge number of process, anthropogenic and natural, are able to form aerosols, which may be transported over long distances. Sulfates e nitrates are responsible for rain acidity; they may also increase the solubility of organic compounds and metals making them more bioavailable, and also can act as cloud condensation nuclei (CCN). Aerosol samples (PM2.5) were collected in a rural and industrial area in Rio de Janeiro, Brazil, in order to quantify chemical species and evaluate anthropogenic influences in secondary aerosol formation and organic compounds. Samples were collected during 24 h every six days using a high-volume sampler from August 2010 to July 2011. The aerosol mass was determined by Gravimetry. The water-soluble ionic composition (WSIC) was obtained by Ion Chromatography in order to determine the major anions (NO3-, SO4= and Cl-); total water-soluble carbon (TWSC) was determined by a TOC analyzer. The average aerosol (PM2.5) concentrations ranged from 1 to 43 ug/m3 in the industrial site and from 4 to 35 ug/m3 in the rural area. Regarding anions, the highest concentrations were measured for SO42- (10.6 ?g/m3-12.6 ?g/m3); where the lowest value was found in the rural site and the highest in the industrial. The concentrations for NO3- and Cl- ranged from 4.2 ?g/m3 to 9.3 ?g/m3 and 3.1 ?g/m3 to 6.4 ?g /m3, respectively. Sulfate was the major species and, like nitrate, it is related to photooxidation in the atmosphere. Interestingly sulfate concentrations were higher during the dry period and could be related to photochemistry activity. The correlations between nitrate and non-sea-salt sulfate were weak, suggesting different sources for these species. The secondary aerosol represented an important fraction of total compounds in PM2.5 ranged from 16 to 18% for (NH4)2SO4 and 6 to 8% for NH4NO3. The values for TWSC ranged from 0.28 to 6.35 ?g/m3 in the industrial area and 0.12 to 7.49 ?g/m3 for rural area. The similarity between the areas regarding secondary aerosols formation and water-soluble carbon compounds is probably due to the particle size.

Gioda, Adriana; Mateus, Vinicius; Monteiro, Isabela; Taira, Fabio; Esteves, Veronica; Saint'Pierre, Tatiana

2013-04-01

333

PLASMA WINDOW FOR VACUUM - ATMOSPHERE INTERFACE AND FOCUSING LENS OF SOURCES FOR NON-VACUUM MATERIAL MODIFICATION.  

SciTech Connect

Material modifications by ion implantation, dry etching, and micro-fabrication are widely used technologies, all of which are performed in vacuum, since ion beams at energies used in these applications are completely attenuated by foils or by long differentially pumped sections, which ate currently used to interface between vacuum and atmosphere. A novel plasma window, which utilizes a short arc for vacuum-atmosphere interface has been developed. This window provides for sufficient vacuum atmosphere separation, as well as for ion beam propagation through it, thus facilitating non-vacuum ion material modification.

HERSHCOVITCH,A.

1997-09-07

334

Single particle impact tests using gas gun and analysis of high strain-rate impact events in ductile materials  

Microsoft Academic Search

Removal of material by the action of impinging particles is known as erosion. Based on the understanding of the material removal mechanisms in ductile materials, in normal impact, material removal occurs predominantly by deformation whereas in oblique impacts, material is removed through a combination of cutting and deformation. Although material can be removed in cutting by a single impact, material

A. A. Cenna; N. W. Page; E. Kisi; M. G. Jones

2011-01-01

335

Single-particle chemical characterization and source apportionment of iron-containing atmospheric aerosols in Asian outflow  

NASA Astrophysics Data System (ADS)

Using a single-particle mass spectrometer, the size and chemical composition of individual Fe-containing atmospheric aerosols (Fe aerosols) with diameter from 100 to 1800 nm were characterized during Asian outflow season (spring of 2008) in Okinawa Island, Japan and their sources were determined. Fe aerosols were classified into five unique particle types which were mixed with specific compound(s) and related to their sources (crustal, fly ash/K-biomass burning, elemental carbon, metals, and vanadium). Particle number-based contribution of the crustal particle type, which has been thought to be the main source of aerosol Fe, was quite small (2 ˜ 10%) in all size ranges, while anthropogenic Fe aerosols were the dominant contributor in this study. Fly ash/K-biomass burning type was the most abundant particle types, which contributed ˜50%. Metals and elemental carbon types contributed ˜20% and ˜10%, respectively. Contribution of vanadium type was variable (5 ˜ 50%), which is attributed to ship emission. The frequent appearance of lithium ion peak in the fly ash/K-biomass burning type strongly suggests that large fraction of the type is coal combustion origin, reflecting high coal usage in China. These results show that anthropogenic sources contributes significant portion of Fe aerosols in Asian outflow. Excluding the vanadium type, relative contribution of the remaining four particle types was constant over the course of study, which remained even when the total concentration of Fe aerosols changed and fraction of the Fe aerosols among atmospheric aerosols decreased significantly by the switch of air mass type into marine type. We concluded that the observed constant relative abundance reflected the relative source strength of Fe aerosols in Asian outflow, particularly emphasizing the importance of coal combustion source in East Asia.

Furutani, Hiroshi; Jung, Jinyoung; Miura, Kazuhiko; Takami, Akinori; Kato, Shungo; Kajii, Yoshizumi; Uematsu, Mitsuo

2011-09-01

336

Mechanistic modelling of Middle Eocene atmospheric carbon dioxide using fossil plant material  

NASA Astrophysics Data System (ADS)

Various proxies (such as pedogenic carbonates, boron isotopes or phytoplankton) and geochemical models were applied in order to reconstruct palaeoatmospheric carbon dioxide, partially providing conflicting results. Another promising proxy is the frequency of stomata (pores on the leaf surface used for gaseous exchange). In this project, fossil plant material from the Messel Pit (Hesse, Germany) is used to reconstruct atmospheric carbon dioxide concentration in the Middle Eocene by analyzing stomatal density. We applied the novel mechanistic-theoretical approach of Konrad et al. (2008) which provides a quantitative derivation of the stomatal density response (number of stomata per leaf area) to varying atmospheric carbon dioxide concentration. The model couples 1) C3-photosynthesis, 2) the process of diffusion and 3) an optimisation principle providing maximum photosynthesis (via carbon dioxide uptake) and minimum water loss (via stomatal transpiration). These three sub-models also include data of the palaeoenvironment (temperature, water availability, wind velocity, atmospheric humidity, precipitation) and anatomy of leaf and stoma (depth, length and width of stomatal porus, thickness of assimilation tissue, leaf length). In order to calculate curves of stomatal density as a function of atmospheric carbon dioxide concentration, various biochemical parameters have to be borrowed from extant representatives. The necessary palaeoclimate data are reconstructed from the whole Messel flora using Leaf Margin Analysis (LMA) and the Coexistence Approach (CA). In order to obtain a significant result, we selected three species from which a large number of well-preserved leaves is available (at least 20 leaves per species). Palaeoclimate calculations for the Middle Eocene Messel Pit indicate a warm and humid climate with mean annual temperature of approximately 22°C, up to 2540 mm mean annual precipitation and the absence of extended periods of drought. Mean relative air humidity was probably rather high, up to 77%. The combined results of the three selected plant taxa indicate values for atmospheric carbon dioxide concentration between 700 and 1100 ppm (probably about 900 ppm). Reference: Konrad, W., Roth-Nebelsick, A., Grein, M. (2008). Modelling of stomatal density response to atmospheric CO2. Journal of Theoretical Biology 253(4): 638-658.

Grein, Michaela; Roth-Nebelsick, Anita; Wilde, Volker; Konrad, Wilfried; Utescher, Torsten

2010-05-01

337

Three-dimensional particle tracking experiments in homogeneous and heterogeneous porous materials  

NASA Astrophysics Data System (ADS)

Small scale laboratory experiments were conducted to measure precisely three dimensional microscopic velocities of tracer particles in porous media. The experiments were based on flow visualization and image analysis and were designed and built to track nonreactive tracer particles inside a Matched Index of Refraction porous material. The MIR material was created by mixing a mineral oil (Paraffin) with borosilicate glass spheres in a (12x12x65cm 3) parallelepiped Pyrex glass column; all having the same index of refraction. By releasing tracer particles in the flowing oil and using appropriate illumination, the fluid motion becomes visible. The particle trajectories were obtained using three-dimensional particle tracking technique. This system is formed by two CCD cameras placed at the height of the middle section of the MIR porous material, with their optical axes perpendicular to each other and to the walls of the test section in the column. The simultaneous images taken from the two cameras were analyzed and their relevant 2D projected trajectories are matched stereoscopically to produce the accurate 3D trajectories. A Lagrangian description of the tracer particles motion was performed, and the coordinates and the velocity components of each tracer particle were determined. The tests were done in a homogeneous medium constructed by the same size diameter glass beads, and a heterogeneous medium constructed by mixing glass spheres with two different diameter sizes. Both one tracer particle tests and two tracer particle tests were carried in each of the homogeneous and heterogeneous materials. The experimental results were in general agreement with the nonergodic theoretical results and were compared with the average plume center position and the ensemble average of the plume second spatial moments.

Lachhab, Ahmed

338

Experimental investigation into shaping particle-reinforced material by WEDM-HS  

Microsoft Academic Search

Particle-reinforced material is a kind of difficult-to-machine material. In general, it is inefficient if conventional methods are used to shape it, with worse surface quality and serious wear of the cutting tool. In this paper, the machineability when the material is machined by wire EDM is studied. A method of orthogonal design has been adopted to determine the main factors

Z. N Guo; X Wang; Z. G Huang; T. M Yue

2002-01-01

339

The mechanical alignment of particles for use in fabricating superconducting and permanent magnetic materials  

DOEpatents

Invention is related to the manufacture of high-quality mechanically aligned superconducting materials using oriented platelet-shaped powder particles, fibers, crystals, and other oriented forms of the recently discovered high-{Tc} class of superconducting ceramics, as well as other superconducting materials. It is also related to the use of these oriented materials in the manufacture of high quality permanent magnetic materials. This pretreatment optimizes the final crystallographic orientation and, thus, properties in these constructs. Such materials as superconducting fibers, needles and platelets are utilized. 11 figs.

Nellis, W.J.; Maple, M.B.

1990-01-24

340

Adaptive binary material classification of an unknown object using polarimetric images degraded by atmospheric turbulence  

NASA Astrophysics Data System (ADS)

An improved binary material-classification algorithm using passive polarimetric imagery degraded by atmospheric turbulence is presented. The technique implements a modified version of an existing polarimetric blind-deconvolution algorithm in order to remove atmospheric distortion and correctly classify the unknown object. The classification decision, dielectric or metal in this case, is based on degree of linear polarization (DoLP) estimates provided by the blind-deconvolution algorithm augmented by two DoLP priors - one statistically modeling the polarization behavior of metals and the other statistically modeling the polarization behavior of dielectrics. The DoLP estimate which maximizes the log-likelihood function determines the image pixel's classification. The method presented here significantly improves upon a similar published polarimetric classification method by adaptively updating the DoLP priors as more information becomes available about the scene. This new adaptive method significantly extends the range of validity of the existing polarimetric classification technique to near-normal collection geometries where most polarimetric material classifiers perform poorly. In this paper, brief reviews of the polarimetric blind-deconvolution algorithm and the functional forms of the DoLP priors are provided. Also provided is the methodology for making the algorithm adaptive including three techniques for updating the DoLP priors using in-progress DoLP estimates. Lastly, the proposed technique is experimentally validated by comparing classification results of two dielectric and metallic samples obtained using the new method to those obtained using the existing technique.

Kim, Mu J.; Hyde, Milo W.

2012-10-01

341

Fluorescence spectra and elastic scattering characteristics of atmospheric aerosol in Las Cruces, New Mexico, USA: Variability of concentrations and possible constituents and sources of particles in various spectral clusters  

NASA Astrophysics Data System (ADS)

The UV-excited laser-induced-fluorescence (UV-LIF) spectra of single atmospheric particles and the three-band integrating-nephelometer elastic scattering of atmospheric aerosol were measured during four approximately 24-h periods on May 2007 in Las Cruces, New Mexico, USA. Aerosol scattering measurements in the nephelometer red channel (50-nm band centered at 700-nm) ranged from around 3-10 times the molecular (Rayleigh) scattering background. On average 22.8% of particles with size greater than about 1 ?m diameter have fluorescence above a preset fluorescence threshold. A hierarchical cluster analysis indicates that most of the single-particle UV-LIF spectra fall into about 10 categories (spectral clusters) as found previously at other geographic sites (Pinnick et al., 2004; Pan et al., 2007). The clusters include spectra characteristic of various humic/fulvic acids, humic-like-substances (HULIS), chemically aged terpenes, fungal spores, polycyclic aromatic hydrocarbons, bacteria, cellulose/pollens, and mixtures of various organic carbon compounds. By far the most populated cluster category is similar to those of chemically aged terpenes/humic-materials; on average this population comprises about 62% of fluorescent particles. Clusters with spectra similar to that of some HULIS aerosol contain on average 10.0% of particles; those characteristic of some fungal spores (or perhaps mixtures of aromatic organic compounds) 8.4% of particles; bacteria-like spectra 1.6% of particles; and cellulose/pollen-like spectra 0.8% of particles. Measurements of fluorescent particles over relatively short (24 min) periods reveal that the concentrations of particles in the most populated clusters are highly correlated, suggesting that the particles populating them derive from the same region; these particles might be composed of crustal material coated with secondary organic carbon. On the other hand, concentrations of particles having cellulose-like spectra are generally uncorrelated with those in any other cluster. No clear distinction in fluorescent aerosol characteristics can be seen for different air mass trajectories arriving at the sampling site, suggesting that fluorescent aerosol particles are primarily of local origin. Integrations of the single-particle UV-LIF spectra over approximate 24 h time intervals reveal two broad peaks around 350 nm and 450 nm (for 263 nm excitation); the 450 nm peak is somewhat similar to that measured previously for water soluble organic carbon derived from aerosol collections. The 350 nm peak apparently has not been seen before in measurements of aerosol collections and may derive from non-soluble primary biological aerosol particles such as fungal spores. Further measurements are needed to investigate in more detail the generality of these results.

Pinnick, R. G.; Fernandez, E.; Rosen, J. M.; Hill, S. C.; Wang, Y.; Pan, Y. L.

2013-02-01

342

Direct observation of aerosol particles in aged agricultural biomass burning plumes impacting urban atmospheres  

NASA Astrophysics Data System (ADS)

Emissions from agricultural biomass burning (ABB) in northern China have a significant impact on the regional and the global climate. According to the Giovanni's Aerosol optical depth (AOD) map, the monthly average AOD at 550 nm in northern China in 2007 shows a maximum value of 0.7 in June, suggesting that episodes of severe aerosol pollution occurred in this region. Aerosol particles were collected in urban Beijing during regional brown hazes from 12 to 30 June, 2007. Transmission electron microscopy with energy-dispersive X-ray spectrometry characterized the morphology, composition, and mixing state of aerosol particles. Potassium salts (K2SO4 and KNO3), ammonium sulfate, soot, and organic particles predominated in fine particles (diameter <1 ?m) collected from 12 to 20 June, 2007. In contrast, from 21 to 30 June, 2007, ammonium sulfate, soot, and organic particles were dominant. Potassium-dominant particles as a tracer of biomass burning, together with wildfire maps, show that intensive regional ABB in northern China from 10 to 20 June, 2007 contributed significantly to the regional haze. After long-range transport, ABB particles exhibited marked changes in their morphology, elemental composition, and mixing state. Heterogeneous reactions completely converted KCl particles from ABB into K2SO4 and KNO3. Soot particles were generally mixed with potassium salts, ammonium salts, and organic particles. In addition, the abundant aged organic particles and soluble salts emitted by ABB become more hygroscopic and increase their size during long-range transport, becoming in effect additional cloud condensation nuclei. The high AOD (average value at 2.2) during 12 to 20 June, 2007, in Beijing is partly explained by the hygroscopic growth of aged fine aerosol particles and by the strong absorption of internally mixed soot particles, both coming from regional ABB emissions.

Li, W. Y.; Shao, L. Y.

2010-04-01

343

ADPIC--A Three-Dimensional Particle-in-Cell Model for the Dispersal of Atmospheric Pollutants and its Comparison to Regional Tracer Studies  

Microsoft Academic Search

A hybrid Lagrangian-Eulerian atmospheric transport-diffusion model was developed to calculate the three-dimensional distribution of atmospheric pollutants in transient-region flow fields. This atmospheric diffusion particle-in-cell (ADPIC) code was validated against several existing closed-form analytical solutions including a puff release in steady, unidirectional shear flow, and a puff release with scale-dependent horizontal and vertical eddy diffusion coefficients. These tests showed that the

Rolf Lange

1978-01-01

344

Water-soluble organics in atmospheric particles: A critical review of the literature and application of thermodynamics to identify candidate compounds  

Microsoft Academic Search

Although organic compounds typically constitute a substantial fraction of the fine particulate matter (PM) in the atmosphere, their molecular composition remains poorly characterized. This is largely because atmospheric particles contain a myriad of diverse organic compounds, not all of which extract in a single solvent or elute through a gas chromatograph; therefore, a substantial portion typically remains unanalyzed. Most often

Pradeep Saxena; Lynn M. Hildemann

1996-01-01

345

Rice straw–wood particle composite for sound absorbing wooden construction materials  

Microsoft Academic Search

In this study, rice straw–wood particle composite boards were manufactured as insulation boards using the method used in the wood-based panel industry. The raw material, rice straw, was chosen because of its availability. The manufacturing parameters were: a specific gravity of 0.4, 0.6, and 0.8, and a rice straw content (10\\/90, 20\\/80, and 30\\/70 weight of rice straw\\/wood particle) of

Han-Seung Yang; Dae-Jun Kim; Hyun-Joong Kim

2003-01-01

346

Demonstration of papilloma virus particles in cervical and vaginal scrape material: a report of 10 cases.  

PubMed Central

The finding of virus particles by transmission electron microscopy (TEM) in fixed cervical and vaginal scrape material and their identification as papilloma viruses by negative staining is described. The colposcopic, cytological, and histological appearances in a group of 10 patients in whom virus particles were seen are discussed and the possibly considered of an association between papilloma virus infection and the development of cervical intraepithelial neoplasia (CIN) and multifocal intraepithelial neoplasia of the female lower genital tract. Images

Stanbridge, C M; Mather, J; Curry, A; Butler, E B

1981-01-01

347

Black carbon enrichment in atmospheric ice particle residuals observed in lower trophospheric mixed phase clouds  

SciTech Connect

The enrichment of black carbon (BC) in residuals of small ice particles was investigated during intensive experiments in winter 2004 and 2005 at the high alpine research station Jungfraujoch (3580 m asl, Switzerland). Two inlets were used to sample the bulk aerosol (residuals of cloud droplets and ice crystals as well as non-activated aerosol particles) and the residual particles of small ice crystals (diameter 5 - 20 m). An enrichment of the BC mass fraction in the ice particle residuals was observed by investigating the measured BC mass concentration as a fraction of the bulk (submicrometer) aerosol mass concentration sampled by the two inlets. On average, the BC mass fraction was 5% for the bulk aerosol and 14% for the ice particle residuals. The observed enrichment of BC in ice particle residuals suggests that BC may act as ice nuclei, with important implications for the indirect aerosol effect via glaciation of clouds.

Cozic, J.; Mertes, S.; Verheggen, B.; Cziczo, Dan; Gallavardin, S. J.; Walter, S.; Baltensperger, Urs; Weingartner, E.

2008-08-15

348

Trace elements in chondritic stratospheric particles - Zinc depletion as a possible indicator of atmospheric entry heating  

NASA Astrophysics Data System (ADS)

Major-element abundances in 11 C, C?, and TCA cosmic dust particles have been measured using SEM and TEM energy dispersive X-ray (EDX) systems. The Fe/Ni ratio, when coupled with major element abundances, appears to be a useful discriminator of cosmic particles. Three particles classified as C?, but having Fe/Ni peak height ratios similar to those measured on the powdered Allende meteorite sample in their HSC EDX spectra, exhibit chondritic minor-/trace-element abundance patterns, suggesting they are extraterrestrial. The one particle classified as C-type, but without detectable Ni in its JSC EDX spectrum, exhibits an apparently nonchondritic minor-/trace-element abundance pattern. A class of particles that are chondritic except for large depletions in the volatile elements Zn and S has been identified. It is likely that these particles condensed with a C1 abundance pattern and that Zn and S were removed by some subsequent process.

Flynn, G. J.; Sutton, S. R.

349

Particle-size requirements for bulk blend materials. Circular Z-146  

SciTech Connect

To provide bulk blenders with size-compatible granular materials and thus reduce segregation problems, it is desirable that producers of the materials be provided with a uniform particle-size distribution model at which to aim their production. A reasonable and somewhat recognized model is the average particle-size distribution found for DAP in the 1972 industry survey of The Fertilizer Institute Product Quality Committee. For reasonable adherence to this model, a material should be sized at least within the limits of the 6- to 16-mesh Tyler screens and should contain plus 8-mesh material to the extent of 25 to 45%. Materials matched to this extent would have Size Guide Numbers, by the CFI system, in the range of about 190 to 235. Satisfactory blends can be made outside this range, provided a reasonable matching of Size Guide Numbers is provided.

Hoffmeister, G.

1982-01-01

350

Composite material reinforced with atomized quasicrystalline particles and method of making same  

SciTech Connect

A composite material comprises an aluminum or aluminum alloy matrix having generally spherical, atomized quasicrystalline aluminum-transition metal alloy reinforcement particles disposed in the matrix to improve mechanical properties. A composite article can be made by consolidating generally spherical, atomized quaiscrystalline aluminum-transition metal alloy particles and aluminum or aluminum alloy particles to form a body that is cold and/or hot reduced to form composite products, such as composite plate or sheet, with interfacial bonding between the quasicrystalline particles and the aluminum or aluminum alloy matrix without damage (e.g. cracking or shape change) of the reinforcement particles. The cold and/or hot worked compositehibits substantially improved yield strength, tensile strength, Young's modulus (stiffness).

Biner, Suleyman B. (Ames, IA); Sordelet, Daniel J. (Ames, IA); Lograsso, Barbara K. (Ames, IA); Anderson, Iver E. (Ames, IA)

1998-12-22

351

Composite material reinforced with atomized quasicrystalline particles and method of making same  

DOEpatents

A composite material comprises an aluminum or aluminum alloy matrix having generally spherical, atomized quasicrystalline aluminum-transition metal alloy reinforcement particles disposed in the matrix to improve mechanical properties. A composite article can be made by consolidating generally spherical, atomized quaiscrystalline aluminum-transition metal alloy particles and aluminum or aluminum alloy particles to form a body that is cold and/or hot reduced to form composite products, such as composite plate or sheet, with interfacial bonding between the quasicrystalline particles and the aluminum or aluminum alloy matrix without damage (e.g. cracking or shape change) of the reinforcement particles. The cold and/or hot worked compositehibits substantially improved yield strength, tensile strength, Young's modulus (stiffness).

Biner, Suleyman B. (Ames, IA); Sordelet, Daniel J. (Ames, IA); Lograsso, Barbara K. (Ames, IA); Anderson, Iver E. (Ames, IA)

1998-12-22

352

Atmospheric radiative effects of an in situ measured Saharan dust plume and the role of large particles  

NASA Astrophysics Data System (ADS)

This work will present aerosol size distributions measured in a Saharan dust plume between 0.9 and 12 km altitude during the ACE-2 campaign 1997. The distributions contain a significant fraction of large particles of diameters from 4 to 30 ?m. Radiative transfer calculations have been performed using these data as input. Shortwave, longwave as well as total atmospheric radiative effects (AREs) of the dust plume are investigated over ocean and desert within the scope of sensitivity studies considering varied input parameters like solar zenith angle, scaled total dust optical depth, tropospheric standard aerosol profiles and particle complex refractive index. The results indicate that the large particle fraction has a predominant impact on the optical properties of the dust. A single scattering albedo of ?o=0.75-0.96 at 550 nm was simulated in the entire dust column as well as 0.76 within the Saharan dust layer at ~4 km altitude indicating enhanced absorption. The measured dust leads to cooling over the ocean but warming over the desert due to differences in their spectral surface albedo and surface temperature. The large particles absorb strongly and they contribute at least 20% to the ARE in the dusty atmosphere. From the measured size distributions modal parameters of a bimodal lognormal column volume size distribution were deduced, resulting in a coarse median diameter of ~9 ?m and a column single scattering albedo of 0.78 at 550 nm. A sensitivity study demonstrates that variabilities in the modal parameters can cause completely different AREs and emphasises the warming effect of the large mineral dust particles.

Otto, S.; de Reus, M.; Trautmann, T.; Thomas, A.; Wendisch, M.; Borrmann, S.

2007-09-01

353

Atmospheric radiative effects of an in-situ measured Saharan dust plume and the role of large particles  

NASA Astrophysics Data System (ADS)

This work will present aerosol size distributions measured in a Saharan dust plume between 0.9 and 12 km altitude during the ACE-2 campaign 1997. The distributions contain a significant fraction of large particles of diameters from 4 to 30 ?m. Radiative transfer calculations have been performed using these data as input. Shortwave, longwave as well as total atmospheric radiative effects (AREs) of the dust plume are investigated over ocean and desert within the scope of sensitivity studies considering varied input parameters like solar zenith angle, scaled total dust optical depth, tropospheric standard aerosol profiles and particle complex refractive index. The results indicate that the large particle fraction has a predominant impact on the optical properties of the dust. A single scattering albedo of ?o=0.75-0.96 at 550 nm was simulated in the entire dust column as well as 0.76 within the Saharan dust layer at ~4 km altitude indicating enhanced absorption. The measured dust leads to cooling over the ocean but warming over the desert due to differences in their spectral surface albedo and surface temperature. The large particles absorb strongly and they contribute at least 20% to the ARE in the dusty atmosphere. From the measured size distributions modal parameters of a bimodal lognormal column volume size distribution were deduced, resulting in a coarse median diameter of ~9 ?m and a column single scattering albedo of 0.78 at 550 nm. A sensitivity study demonstrates that variabilities in the modal parameters can cause completely different AREs and emphasises the warming effect of the large mineral dust particles.

Otto, S.; de Reus, M.; Trautmann, T.; Thomas, A.; Wendisch, M.; Borrmann, S.

2007-06-01

354

Production of “potential” cloud condensation nuclei associated with atmospheric new-particle formation in northern Finland  

Microsoft Academic Search

During a 33-month measurement period at a high-latitude background site in northern Finland, a total of 103 new particle formation events were observed. In 19 cases, movement of the air masses allowed the observation of particle formation and growth over a sufficiently long time to investigate the production of “potential” cloud condensation nuclei (CCN) resulting from new-particle formation. All the

H. Lihavainen; V.-M. Kerminen; M. Komppula; J. Hatakka; V. Aaltonen; M. Kulmala; Y. Viisanen

2003-01-01

355

Production of ``potential'' cloud condensation nuclei associated with atmospheric new-particle formation in northern Finland  

Microsoft Academic Search

During a 33-month measurement period at a high-latitude background site in northern Finland, a total of 103 new particle formation events were observed. In 19 cases, movement of the air masses allowed the observation of particle formation and growth over a sufficiently long time to investigate the production of ``potential'' cloud condensation nuclei (CCN) resulting from new-particle formation. All the

H. Lihavainen; V.-M. Kerminen; M. Komppula; J. Hatakka; V. Aaltonen; M. Kulmala; Y. Viisanen

2003-01-01

356

Hygroscopic mineral dust particles as influenced by chlorine chemistry in the marine atmosphere  

Microsoft Academic Search

Morphology and elemental compositions of individual dust particles were investigated with the use of Asian dust samples collected at a site along the Sea of Japan side of the archipelago. Our results indicate the preferential formation of chloride in Ca-containing dust particles (0.1 < Cl\\/Ca < 0.65) in cases when the particles contain little or no sulfate. Most of them

Yutaka Tobo; Daizhou Zhang; Naonobu Nakata; Maromu Yamada; Hiroko Ogata; Kazutaka Hara; Yasunobu Iwasaka

2009-01-01

357

An Investigation of the Effect of Particle Ionization on the Earth's Middle Atmosphere Using a Two-dimensional Model  

NASA Astrophysics Data System (ADS)

The amount of NO transported to the stratosphere is determined by mesospheric processes where uncertainties in the production, loss and transport of odd nitrogen exist. We have used the NRL 2 Dimensional model of atmospheric chemistry and dynamics to investigate aspects of the transport of odd nitrogen from the mesopause region to the upper stratosphere. An important aspect of the NOx transport problem is determining the influence of time varying middle energy electron ionization rates on the flux of odd nitrogen into the lower atmosphere. This problem is investigated with the two dimensional model employing a time dependent ionization source scaled to the measured particle energy incident on the atmosphere. The model results are guided by comparisons to HALOE measurements of mesospheric and stratospheric odd nitrogen. In particular we will use the data to provide information on the interannual and seasonal variability of odd nitrogen in the upper stratosphere/mesosphere. These data will be compared over several years with the model results employing the time dependent energy measurements to calculate the flux of odd nitrogen into the lower atmosphere. The effect of the enhanced odd nitrogen on upper stratospheric ozone will be discussed.

Rusch, D. W.; Randall, C. E.; Siskind, D. E.

2005-05-01

358

Development and characterization of an ion trap mass spectrometer for the on-line chemical analysis of atmospheric aerosol particles  

NASA Astrophysics Data System (ADS)

A novel Ion Trap Aerosol Mass Spectrometer (IT-AMS) for atmospheric particles has been developed and characterized. With this instrument the chemical composition of the non-refractory component of aerosol particles can be measured quantitatively. The set-up makes use of the well-characterized inlet and vaporization/ionization system of the Aerodyne Aerosol Mass Spectrometer (AMS). While the AMS uses either a linear quadrupole mass filter (Q-AMS) or a time-of-flight mass spectrometer (ToF-AMS) as the mass analyzer, the IT-AMS utilizes a three-dimensional quadrupole ion trap. The main advantages of an ion trap are the possibility of performing MSn-experiments as well as ion/molecule reaction studies. The mass analyzer has been built in-house together with major components of the electronics. The IT-AMS is operated under full PC control and can be used as a field instrument due to its compact size. A detailed description of the set-up is presented. Experiments show that a mass resolving power larger than 1500 can be reached. This value is high enough to separate different organic species at m/z 43. Calibrations with laboratory-generated aerosol particles indicate a linear relationship between signal response and aerosol mass concentration. These studies, together with estimates of the detection limits for particulate sulfate (0.65 [mu]g/m3) and nitrate (0.16 [mu]g/m3) demonstrate the suitability of the IT-AMS to measure atmospheric aerosol particles. An inter-comparison between the IT-AMS and a Q-AMS for nitrate in urban air yields good agreement. For laboratory-generated polystyrene latex particles a MS/MS-study using collision-induced dissociation (CID) with a daughter/parent ion yield of more than 60% has been performed. In the future, similar MS/MS-studies can be conducted for atmospheric particles and for the study of secondary aerosol formation in smog chamber experiments.

Kürten, Andreas; Curtius, Joachim; Helleis, Frank; Lovejoy, Edward R.; Borrmann, Stephan

2007-08-01

359

Black carbon enrichment in atmospheric ice particle residuals observed in lower tropospheric mixed phase clouds  

Microsoft Academic Search

The enrichment of black carbon (BC) mass in residuals of small ice crystals was investigated during intensive experiments in winter 2004 and 2005 at the high alpine research station Jungfraujoch (3580 m asl, Switzerland). Two inlets were used to sample the bulk aerosol (residuals of cloud droplets and ice crystals and nonactivated aerosol particles) and the residual particles of small

J. Cozic; S. Mertes; B. Verheggen; D. J. Cziczo; S. J. Gallavardin; S. Walter; U. Baltensperger; E. Weingartner

2008-01-01

360

Atmospheric particle formation events at Värriö measurement station in Finnish Lapland 1998 2002  

NASA Astrophysics Data System (ADS)

We have identified 147 clear 8 nm diameter particle formation events at the SMEAR I station in Värriö, northern Finland during calendar years 1998-2002. The events have been classified in detail according to the particle formation rate, growth rate, event starting time, different gas phase species concentrations and pre-existing particle concentrations as well as various meteorological conditions. Most of the events occurred during the spring months between March and May, suggesting that increasing biological activity might produce the precursor gases for particle formation. The apparent 8 nm particle formation rates were around 0.1/cm3s, and they were uncorrelated with growth rates that vary between 0.5 and 10 nm/h. The air masses, which had clearly elevated sulphur dioxide concentrations above 1.6 ppb came, as expected, from the direction of Nikel and Monschegorsk smelteries. Only 15 formation events can be explained by the pollution plume from these sources.

Vehkamäki, H.; dal Maso, M.; Hussein, T.; Flanagan, R.; Hyvärinen, A.; Lauros, J.; Merikanto, J.; Mönkkönen, P.; Pihlatie, M.; Salminen, K.; Sogacheva, L.; Thum, T.; Ruuskanen, T.; Keronen, P.; Aalto, P. P.; Hari, P.;  Lehtinen, K. E. J.;  Rannik, Ü.;  Kulmala, M.

2004-06-01

361

Preparation and Characterization of Barium Sulfate Particles as Contrast Materials for Surgery  

NASA Astrophysics Data System (ADS)

Barium sulfate particles were prepared from BaCl2 and Na2SO4 under various conditions to explore their potential application as contrast material in endovascular surgery. Ethanol was added for the stabilization of the suspension obtained. Particle characteristics of the samples were determined by SEM and light scattering, while the stability of the suspensions was characterized by sedimentation experiments. Particle characteristics were shown to depend very much on reaction conditions. Particles were obtained in spherical and plate like shape and in a variety of sizes. Primary particles of nanometer size formed aggregates in most cases. Some of the samples had bimodal particle size distribution. Particle characteristics determined from SEM micrographs, by laser light scattering measurements and calculated from sedimentation experiments often differed from each other. The discrepancy could be explained by the dissimilar behavior of various fractions and the different sensitivity of the measurements to them. Some of the samples showed aging phenomena in DMSO leading either to the formation of larger particles or to the break down of aggregates.

Figyelmesi, Árpád; Pukánszky, Béla, Jr.; Bagdi, Kristóf; Tóvölgyi, Zsuzsa; Varga, József; Botz, Lajos; Hudak, Stephan; Dóczi, Tamás; Pukánszky, Béla

362

Surface-quaternized chitosan particles as an alternative and effective organic antibacterial material.  

PubMed

Taking advantage of the large surface area that is covered with permanent positive charges of quaternary ammonium entities, this research aimed to develop environmentally friendly, organic antibacterial material from quaternized chitosan particles that may be applicable for biomedical devices, health and textile industries. The particles were formulated by ionic crosslinking of chitosan with tripolyphosphate followed by quaternization under heterogeneous conditions, via either direct methylation or reductive N-alkylation with a selected aldehyde followed by methylation. Sub-micron, spherical and positively charged quaternized chitosan particles were formed, as determined by (1)H NMR, FT-IR, PCS and TEM analysis. Antibacterial activity tests, performed by viable cell (colony) counts, suggested that all quaternized chitosan particles exhibited superior antibacterial activity against the model Gram-positive bacteria, Staphylococcus aureus, as compared to the native chitosan particles at neutral pH. Only some quaternized chitosan particles, especially those having a high charge density and bearing large alkyl substituent groups, were capable of suppressing the growth of the model Gram-negative bacteria, Escherichia coli. The inhibitory efficiency of the quaternized chitosan particles was quantified in terms of the minimum inhibitory concentration (MIC). Damaging impact of the quaternized chitosan particles on the bacteria was also qualitatively determined by microscopic observation of the bacterial morphology. PMID:22197736

Wiarachai, Oraphan; Thongchul, Nuttha; Kiatkamjornwong, Suda; Hoven, Voravee P

2011-12-03

363

The Material Analysis Particle Probe (MAPP) as an in-situ plasma-material interaction diagnostic in NSTX  

Microsoft Academic Search

The National Spherical Torus Experiment uses lithium as a plasma-facing surface to enhance plasma performance. Control of hydrogen recycling is dependent on surface chemistry of lithium depositions on graphite and metallic substrates. To characterize the surface chemistry evolution of the in-vessel surface during plasma irradiation a new Material Analysis Particle Probe (MAPP) has been designed that exposes in-situ samples to

Bryan Heim; Chase Taylor; Sami Ortoleva; Miguel Gonzalez; Jean Paul Allain; Henry Kugel; Robert Kaita; Charles Skinner

2010-01-01

364

Heterogeneous Reactions of NO3 Radicals With Polycyclic Aromatic Hydrocarbons and Alkane Monolayers as Proxies for Particles in the Atmosphere  

NASA Astrophysics Data System (ADS)

The nitrate radical NO3 is an important nighttime oxidant in the troposphere, especially in polluted urban areas. While homogeneous gas-phase reactions of NO3 with organic substances of atmospheric importance have been studied in detail, little research has focused on heterogeneous reactions of NO3 with atmospheric organic particles. As reaction rates, products, and mechanisms can be very different in heterogeneous reactions compared to the corresponding homogeneous reactions, there is a need for investigations on these heterogeneous processes. Reactions on atmospheric particulate matter can also have a major effect on important properties of aerosol particles (e.g. hydrophilicity, toxicity, and optical properties). Polycyclic aromatic hydrocarbons (PAHs) are atmospheric pollutants that result from incomplete combustion processes. Due to their abundance and toxicity, they are of high scientific interest. To gain insight into heterogeneous reactions of this class of compounds, solid films of four different PAHs were exposed to gas phase NO3 radicals using a flow tube reactor coupled to a chemical ionization mass spectrometer. The reactive uptake coefficient ? of these reactions was determined. Results show a very fast reaction of NO3 with PAHs (pyrene and fluoranthene: ? ? 0.2, benz[a]anthracene: ? = 0.06 ± 0.01) while reactions of N2O5, O3, NO2, and HNO3 with PAH surfaces are significantly slower (e.g. for pyrene + O3 ? ? 1.4 × 10-6). Although atmospheric concentrations of NO3 are lower compared to the other gas phase oxidants studied, NO3 heterogeneous reactions are still more important for the oxidation of PAHs in atmospheric particulate matter due to the higher reactivity of NO3. Self assembled monolayers (SAMs) are frequently used as model substrates for organic aerosol surfaces. To study heterogeneous reactions of alkane surfaces, a SAM of octadecanethiol on a gold substrate was exposed to NO3 radicals. Surface products were studied using X-ray photoelectron spectroscopy (XPS). No volatilization or destruction of the SAM was detected using XPS. Formation of hydroxyl-, carbonyl-, and carboxylic functional groups was observed.

Gross, S.; Knopf, D. A.; Mak, J.; Bertram, A. K.

2006-12-01

365

Hygroscopic properties of atmospheric aerosol particles over the Eastern Mediterranean: implications for regional direct radiative forcing under clean and polluted conditions  

Microsoft Academic Search

This work examines the effect of direct radiative forcing of aerosols in the eastern Mediterranean troposphere as a function of air mass composition, particle size distribution and hygroscopicity, and relative humidity (RH). During intensive field measurements on the island of Crete, Greece, the hygroscopic properties of atmospheric particles were determined using a Hygroscopicity Tandem Differential Mobility Analyzer (H-TDMA) and a

M. Stock; Y. F. Cheng; W. Birmili; A. Massling; B. Wehner; T. Müller; S. Leinert; N. Kalivitis; N. Mihalopoulos; A. Wiedensohler

2011-01-01

366

Exploration of Heterogeneous Chemistry in Model Atmospheric Particles Using Extended X-ray Absorption Fine Structure Analysis  

SciTech Connect

As models of the composition and heterogeneous chemical reactions of the troposphere undergo refinement, novel application of state-of-the-art analytical techniques will be necessary to propound realistic characterizations of mineral dust chemistry. In this study, strontium carbonate particles treated with gaseous nitric acid and nitrogen dioxide were examined with X-ray absorption fine structure analysis (EXAFS). The X-ray spectra of carbonate and nitrate standards were fitted to ab initio calculations, which were used to determine the structure and consistency of strontium nitrate formed on strontium carbonate. By examining differences in mean square radial displacement and lattice spacing values obtained for bulk Sr(NO3)2 as compared to Sr(NO3)2 formed on SrCO3, EXAFS proves effective as a tool for investigating the local structure and composition of heterogeneous aerosol particles. The implications of findings on reacted strontium carbonate for atmospheric models of calcium carbonate aerosol are discussed.

Bramante,J.; Hinrichs, R.; Brown, E.; Calvin, S.

2007-01-01

367

Simultaneous determination by ultra-performance liquid chromatography-atmospheric pressure chemical ionization time-of-flight mass spectrometry of nitrated and oxygenated PAHs found in air and soot particles.  

PubMed

An ultra-performance liquid chromatographic-atmospheric pressure chemical ionization time-of-flight mass spectrometric (UPLC-APCIToFMS) method for rapid analysis of twelve nitrated polycyclic aromatic hydrocarbons (NPAHs) and nine oxygenated polycyclic aromatic hydrocarbons (OPAHs) in particle samples has been developed. The extraction step using pressurized liquid extraction was optimized by experimental design methods and the concentrated extracts were analyzed without further clean-up. Matrix effects resulting in suppression or enhancement of the response during the ionization step were not observed. The suitability of the developed method is demonstrated by analysis of six different particle samples including standard reference materials, atmospheric particles collected by a high-volume sampler at an urban background site, and a soot sample from a burner. Results from these measurements showed clear differences between the different kinds of samples. Concentrations from reference materials are in good agreement with those from previous studies. Additionally a clear seasonal trend could be observed in atmospheric NPAH and OPAH concentrations found in real samples, with higher concentrations in winter. PMID:20101503

Mirivel, Giovanni; Riffault, Véronique; Galloo, Jean-Claude

2010-01-26

368

Influence of the Spray Angle on the Characteristics of Atmospheric Plasma Sprayed Hard Material Based Coatings  

NASA Astrophysics Data System (ADS)

This paper presents an investigation of the influence of the spray angle on thermally sprayed coatings. Spray beads were manufactured with different spray angles between 90 and 20° by means of atmospheric plasma spraying (APS) on heat-treated mild steel (1.0503). WC-12Co and Cr3C2-10(Ni20Cr) powders were employed as feedstock materials. Every spray bead was characterized by a Gaussian fit. This opens the opportunity to analyze the influence of the spray angle on coating properties. Furthermore, metallographic studies of the surface roughness, porosity, hardness, and morphology were carried out and the deposition efficiency as well as the tensile strength was measured. The thermally sprayed coatings show a clear dependence on the spray angle. A decrease in spray angle changes the thickness, width, and form of the spray beads. The coatings become rougher and their quality decreases.

Tillmann, Wolfgang; Vogli, Evelina; Krebs, Benjamin

2008-12-01

369

High frequency atmospheric cold plasma treatment system for materials surface processing  

NASA Astrophysics Data System (ADS)

The paper presents a new laboratory-made plasma treatment system. The power source which generates the plasma is based on a modern half-bridge type inverter circuit working at a frequency of 4 MHz, and giving an output power of about 200 W. The inverter is fed directly from the mains voltage and features high speed protection circuits for both over voltage and over current protection, making the system light and easy to operate. The output of the inverter is connected to the resonant circuit formed by a Tesla coil and the dielectric barrier discharge plasma chamber. The plasma is generated at atmospheric pressure in argon, helium or mixtures of helium and small quantities of argon. It is a cold discharge (Tgas < 150°C) with a homogeneous structure. The plasma generates chemically active species, especially O and OH, which could be important in various applications such as the treatment and processing of materials surfaces.

Tudoran, Cristian D.; Surducan, Vasile; Anghel, Sorin D.

2012-02-01

370

Characteristics and morphology of wear particles from laboratory testing of disk brake materials  

Microsoft Academic Search

The geometrical characteristics and morphology of wear particles generated from brake materials are important for environmental and tribological reasons. Low- and high-speed, pin-on-disk friction and wear testing of a commercial truck brake pad material against cast iron was conducted in which wear debris was collected. The sliding speed was held constant either at 0.275 or at 5m\\/s, and the nominal

Mohsen Mosleh; Peter J Blau; Delia Dumitrescu

2004-01-01

371

Sieveless particle size distribution analysis of particulate materials through computer vision  

SciTech Connect

This paper explores the inconsistency of length-based separation by mechanical sieving of particulate materials with standard sieves, which is the standard method of particle size distribution (PSD) analysis. We observed inconsistencies of length-based separation of particles using standard sieves with manual measurements, which showed deviations of 17 22 times. In addition, we have demonstrated the falling through effect of particles cannot be avoided irrespective of the wall thickness of the sieve. We proposed and utilized a computer vision with image processing as an alternative approach; wherein a user-coded Java ImageJ plugin was developed to evaluate PSD based on length of particles. A regular flatbed scanner acquired digital images of particulate material. The plugin determines particles lengths from Feret's diameter and width from pixel-march method, or minor axis, or the minimum dimension of bounding rectangle utilizing the digital images after assessing the particles area and shape (convex or nonconvex). The plugin also included the determination of several significant dimensions and PSD parameters. Test samples utilized were ground biomass obtained from the first thinning and mature stand of southern pine forest residues, oak hard wood, switchgrass, elephant grass, giant miscanthus, wheat straw, as well as Basmati rice. A sieveless PSD analysis method utilized the true separation of all particles into groups based on their distinct length (419 639 particles based on samples studied), with each group truly represented by their exact length. This approach ensured length-based separation without the inconsistencies observed with mechanical sieving. Image based sieve simulation (developed separately) indicated a significant effect (P < 0.05) on number of sieves used in PSD analysis, especially with non-uniform material such as ground biomass, and more than 50 equally spaced sieves were required to match the sieveless all distinct particles PSD analysis. Results substantiate that mechanical sieving, owing to handling limitations and inconsistent length-based separation of particles, is inadequate in determining the PSD of non-uniform particulate samples. The developed computer vision sieveless PSD analysis approach has the potential to replace the standard mechanical sieving. The plugin can be readily extended to model (e.g., Rosin Rammler) the PSD of materials, and mass-based analysis, while providing several advantages such as accuracy, speed, low cost, automated analysis, and reproducible results.

Igathinathane, C. [Mississippi State University (MSU); Pordesimo, L. O. [Mississippi State University (MSU); Columbus, Eugene P [ORNL; Batchelor, William D [ORNL; Sokhansanj, Shahabaddine [ORNL

2009-05-01

372

Occurrence and gas/particle partitioning of PAHs in the atmosphere from the North Pacific to the Arctic Ocean  

NASA Astrophysics Data System (ADS)

Gas- and particle-phase polycyclic aromatic hydrocarbons (PAHs) were collected in the atmosphere from the North Pacific to the Arctic Ocean to investigate their occurrence and gas/particle distribution. Significant linear correlations were observed between the gaseous concentrations of 9 PAHs and latitudes (r2 = 0.69). The regression of gaseous PAHs and 1/T also gave a certain extent correlation (r2 = 0.46). The gas/particle partition coefficients (KP) correlated well with the sub-cooled liquid vapor pressures (poL) of PAHs with slopes higher than the theoretical value of ?1, and the regressions of logKP–logpoL possessed a general tendency to intersect at a point (?2.52, ?1.60). The non-linear regression of logpoL and the particle fraction displayed a more significant correlation (r2 = 0.84) than the linear relation of logKP–logpoL (r2 = 0.69). The influence of soot on KP was investigated, and it was found that the predicted values derived from the soot-air model agreed relatively better with the field measurements than those calculated based on the Junge–Pankow model and the KOA-based model. The results indicated that soot played an important role on the partitioning of PAHs to aerosols, and the partitioning of PAHs is more sensitive to presence of elemental carbon compared to organic matter of the aerosol.

Wang, Zhen; Na, Guangshui; Ma, Xindong; Fang, Xiaodan; Ge, Linke; Gao, Hui; Yao, Ziwei

2013-10-01

373

The preparation of copper fine particle paste and its application as the inner electrode material of a multilayered ceramic capacitor  

Microsoft Academic Search

Well size-controlled copper fine particles (diameter: 100-300 nm) were used as the inner electrode material of multilayered ceramic capacitors (MLCCs). The particles were dispersed in terpineol to form a printing paste with 50 wt% copper particles. The MLCC precursor modules prepared by the layer-by-layer printing of copper and BaTiO3 particles were cosintered. Detailed observation of the particles, paste, and MLCCs

Tetsu Yonezawa; Shinsuke Takeoka; Hiroshi Kishi; Kiyonobu Ida; Masanori Tomonari

2008-01-01

374

Polycyclic aromatic hydrocarbons in urban atmosphere of Guangzhou, China: Size distribution characteristics and size-resolved gas-particle partitioning  

NASA Astrophysics Data System (ADS)

Size distributions of thirteen polycyclic aromatic hydrocarbons (PAHs), elemental carbon (EC), and organic carbon (OC) in the range of 0.01-18 ?m were measured using a nano Micro-Orifice Uniform Deposit Impactor (nano-MOUDI) in an urban location in Guangzhou, China in July 2006. PAH size distributions were fit with five modes and the respective mass median aerodynamic diameters (MMAD) are: Aitken mode (MMAD: ˜0.05 ?m), three accumulation modes AMI, AMII, AMIII (MMAD: 0.13-0.17 ?m, 0.4-0.45 ?m, and 0.9-1.2 ?m, respectively), and coarse mode (MMAD: 4-6 ?m). Seven-ring PAH was mainly in AMII and AMIII. Five- and six-ring PAHs were found to be abundant in all the three AM. Three- and four-ring PAHs had a significant presence in the coarse mode in addition to the three AM. Size-resolved gas-particle partition coefficients of PAHs (Kp) were estimated using measured EC and OC data. The Kp values of a given PAH could differ by a factor of up to ˜7 on particles in different size modes, with the highest Kp associated with the AMI particles and the lowest Kp associated with the coarse mode particles. Comparison of calculated overall Kp with measured Kp values in Guangzhou by Yang et al. (2010) shows that adsorption on EC appeared to be the dominant mechanism driving the gas-particle partitioning of three- and four-ring PAHs while absorption in OM played a dominant role for five- and six-ring PAHs. The calculated equilibrium timescales of repartitioning indicate that five- to seven-ring PAHs could not achieve equilibrium partitioning within their typical residence time in urban atmospheres, while three- and four-ring PAHs could readily reach new equilibrium states in particles of all sizes. A partitioning flux is therefore proposed to replace the equilibrium assumption in modeling PAH transport and fate.

Yu, Huan; Yu, Jian Zhen

2012-07-01

375

LEVOGLUCOSAN, A TRACER FOR CELLULOSE IN BIOMASS BURNING AND ATMOSPHERIC PARTICLES. (R823990)  

EPA Science Inventory

Abstract The major organic components of smoke particles from biomass burning are monosaccharide derivatives from the breakdown of cellulose, accompanied by generally lesser amounts of straight-chain, aliphatic and oxygenated compounds and terpenoids from vegetation wa...

376

Evidence for Propagation of Aerobic Bacteria in Particles Suspended in Gaseous Atmospheres.  

National Technical Information Service (NTIS)

One factor involved in the possibility that airborne microbes might contaminate the Jovian atmosphere, is whether microbes have the capacity to propagate in air. Prior to these studies, the evidence was that the airborne state was lethal to microbes. By m...

R. L. Dimmick M. A. Chatigny H. Wolochow P. Straat

1977-01-01

377

Focusing Particles with Diameters of 1 to 10 Microns into Beams at Atmospheric Pressure  

Microsoft Academic Search

We report on an ambient-pressure aerodynamic lens for particles in the 1–10 ? m diameter range, operating at a flow rate of about 1 lpm, that greatly increases the particle number density downstream of the lens. Intended for use with optical monitors, the lens's low pressure drop (10–30 Torr) minimizes pumping requirements and thus power consumption. Numerical modeling indicates that

Rensheng Deng; Xuefeng Zhang; Kenneth A. Smith; Joda Wormhoudt; David K. Lewis; Andrew Freedman

2008-01-01

378

SINGLE PARTICLE IMPACT BREAKAGE CHARACTERIZATION OF MATERIALS BY DROP WEIGHT TESTING  

Microsoft Academic Search

A drop weight tester was designed for the purpose of analyzing single particle impact breakage characteristics of different materials. Test results were evaluated through the breakage distributions of different size fractions at various impact energy levels. Breakage parameter t10 (Narayanan, 1986) is used to represent the degree of size reduction which is assumed to be represantative of the breakage product

Ömürden GENÇ; Levent ERGÜN; Hakan BENZER

2004-01-01

379

USE OF METAL- AND FLUORESCEIN-TAGGED MATERIALS TO STUDY SETTLED PARTICLES EXPOSURE PATHWAYS  

EPA Science Inventory

Through the use of ten size ranges of tagged materials (Antley et. al., 2000a), inductively coupled plasma- mass spectrometry (ICP-MS) and flourometry are being used to study the movement of settled particles in the indoor environment, exposure pathways, and the collection effi...

380

A particle size distribution analysis of stressed HPLC column packing material  

Microsoft Academic Search

A particle size distribution analysis has been completed on three different HPLC column packing materials including silica gel (Si60) and two bonded phases (RP8 and RP18). The stationary phases were subjected to 18 hours stress with 1 N or 3 N KOH and found to have quantitatively different distribution patterns initially, at 13 hours and finally at 18 hours although

T. D. Wilson; D. M. Simmons

1991-01-01

381

Harnessing Labile Bonds between Nanogels Particles to Create Self-Healing Materials  

Microsoft Academic Search

Using computational modeling, we demonstrate the self-healing behavior of novel materials composed of nanoscopic gel particles that are interconnected into a macroscopic network by both stable and labile bonds. Under mechanical stress, the labile bonds between the nanogels can break and readily reform with reactive groups on neighboring units. This breaking and reforming allows the units in the network to

German V. Kolmakov; Krzysztof Matyjaszewski; Anna C. Balazs

2009-01-01

382

Study of particle rebound characteristics and material erosion at high temperature  

SciTech Connect

The rebound characteristics of 15 micron mean diameter fly ash particles impacting several target materials were measured using Laser Doppler Velocimetry (LDV). Detailed results including the effects of various parameters were given in a previous report. This report focuses on the effects of new additional parameters on the rebound characteristics. First, the restitution parameters are reported at small impact angles (less than 15 degrees) for 410 stainless steel, 2024 aluminum, 6Al-4V titanium, INCO 718, RENE 41, AM 355, L605 cobalt and alumina (Al/sub 2/O/sub 3/). The fly ash rebound data for these target materials are then investigated in an effort to develop generalized correlations for the restitution coefficients. The effect of the target surface geometry on the rebound characteristics is investigated for 2024 aluminum as the next step. Finally, three-dimensional (3-D) rebound characteristics are presented for fly ash particles impacting INCO 718 and 2024 aluminum target materials. Semiempirical erosion rate equations are reported for 2024 aluminum, INCO 718, RENE 41 and AM355 alloys from the experimental erosion results for fly ash and silica sand particles at various particle velocities and material temperatures. 18 refs., 86 figs.

Tabakoff, W.; Hamed, A.; Eroglu, H.

1988-12-01

383

Molecular dynamics simulation studies of material modification by charged particle irradiation  

Microsoft Academic Search

Charged particle irradiation processes, such as ion beam deposition and electron beam irradiation are often used to modify the properties of various materials. However, detailed reaction mechanisms that lead to structural changes in the substrates are difficult to determine experimentally, as primarily indirect information is obtained using experimental methods. Computer simulation methods are complementary to experimental approaches and are able

Inkook Jang

2004-01-01

384

Effects of cement particle size distribution on performance properties of Portland cement-based materials  

SciTech Connect

The original size, spatial distribution, and composition of Portland cement particles have a large influence on hydration kinetics, microstructure development, and ultimate properties of cement-based materials. In this paper, the effects of cement particle size distribution on a variety of performance properties are explored via computer simulation and a few experimental studies. Properties examined include setting time, heat release, capillary porosity percolation, diffusivity, chemical shrinkage, autogenous shrinkage, internal relative humidity evolution, and interfacial transition zone microstructure. The effects of flocculation and dispersion of the cement particles in the starting microstructures on resultant properties are also briefly evaluated. The computer simulations are conducted using two cement particle size distributions that bound those commonly in use today and three different water-to-cement ratios: 0.5, 0.3, and 0.246. For lower water-to-cement ratio systems, the use of coarser cements may offer equivalent or superior performance, as well as reducing production costs for the manufacturer.

Bentz, D.P.; Garboczi, E.J.; Haecker, C.J.; Jensen, O.M.

1999-10-01

385

Use of natural particles for the removal of paint from aeronautical composite materials  

NASA Astrophysics Data System (ADS)

Paint removal by blasting and its effects on the surface morphology of aeronautical composite materials are investigated. An ideal combination of the parameters for mechanical paint removal by blasting such as particle type, size, velocity and angle of incidence yields a stripped aircraft skin substrate with minimal or no damage. Natural particles, specifically white corn flour, seem to be a good choice for paint removal by blasting. Since they are softer as well as smaller in size than other particles used for paint removal, they minimize the amount of damage to the surface of the composite. They are also cheaper and produce no harm to environment. The variation of the degree of surface roughness and the amount of broken fibers were correlated with some stripping parameters, such as particle impact angle and velocity. This defined an optimum environment for paint removal by blasting.

Guy, Thu-Ha; Lankarani, Hamid M.; Talia, Jorge E.

386

Novel building blocks for materials by design: Janus particles and other patchy colloids  

NASA Astrophysics Data System (ADS)

The emergent assembly of nonisotropically structured colloidal particles can lead to novel materials with requisite optical or mechanical properties. We have developed two models---one that includes detailed interactions between particles and another that coarse-grains the interactions---so as to explore the equilibrium and dynamics effected by varying interaction heterogeneities. In particular, we have performed a series of simulations of systems consisting of Janus particles---in which each of two hemispheres can be characterized by a single interaction type such as charge or degree of hydrophobicity. The equilibrium structure of Janus clusters has been the subject of experimental and theoretical studies by Grannick and coworkers. We find that the bulk Janus systems give rise to surprising equilibrium structure and dynamics which can be tuned through both the volume fraction and the interactions. The coarse-grained model provides surprisingly good agreement with the more detailed particle-model for the equilibrium structure while overestimating the relaxation rates.

Hernandez, Rigoberto; Hagy, Matthew C.

2012-02-01

387

Atmospheric particle formation events at Värriö measurement station in Finnish Lapland 1998-2002  

NASA Astrophysics Data System (ADS)

During the calendar years 1998-2002, 147 clear 8nm diameter particle formation events have been identified at the SMEAR I station in Värriö, northern Finland. The events have been classified in detail according to the particle formation rate, growth rate, event starting time, different trace gas concentrations and pre-existing particle concentrations as well as various meteorological conditions. The frequency of particle formation and growth events was highest during the spring months between March and May, suggesting that increasing biological activity might produce the precursor gases for particle formation. The apparent 8nm particle formation rates were around 0.1 /cm3s, and they were uncorrelated with growth rates that varied between 0.5 and 10nm/h. The air masses with clearly elevated sulphur dioxide concentrations (above 1.6ppb) came, as expected, from the direction of the Nikel and Monschegorsk smelters. Only 15 formation events can be explained by the pollution plume from these sources.

Vehkamäki, H.; Dal Maso, M.; Hussein, T.; Flanagan, R.; Hyvärinen, A.; Lauros, J.; Merikanto, P.; Mönkkönen, M.; Pihlatie, K.; Salminen, K.; Sogacheva, L.; Thum, T.; Ruuskanen, T. M.; Keronen, P.; Aalto, P. P.; Hari, P.; Lehtinen, K. E. J.; Rannik, Ü.; Kulmala, M.

2004-10-01

388

Seasonal variation of source contributions to atmospheric fine and coarse particles at suburban area in Istanbul, Turkey  

SciTech Connect

Daily samples of fine (PM2.5) and coarse (PM2.5-10) particles were collected from July 2002 to July 2003 to provide a better understanding of the elemental concentration and source contribution to both PM fractions. Sampling location represents suburban part of Istanbul metropolitan city. Samples were collected on Teflon filters using a 'Dichotomous Sampler.' Concentrations of Al, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, V, and Zn were measured by GFAAS, FAAS, and FAES techniques. Elemental variations of heating and nonheating seasons were discussed. Fossil fuel-related atmospheric metals dramatically increased during the heating season, while natural originated atmospheric metals increased during the nonheating season. Seasonal variations of source contributions were evaluated using factor analysis, which was separately applied to the collected fine and coarse particles data sets during heating and nonheating seasons (four data sets: PM2.5 heating, PM2.5 nonheating, PM2.5-10 heating, and PM2.5-10 nonheating). Significant seasonal differences in source contributions were observed. Four factor groups were extracted for PM2.5 dataset during the nonheating season, while five factor groups were extracted for all the other cases. Mineral dust transportation, traffic, and industry-related activities were classified as different factor groups in all the cases.

Karaca, F.; Alagha, O.; Erturk, F.; Yilmaz, Y.Z.; Ozkara, T. [Fatih University, Istanbul (Turkey). Dept. for Environmental Engineering

2008-06-15

389

Particle size distributions of oil mists in workplace atmospheres and their exposure concentrations to workers in a fastener manufacturing industry.  

PubMed

This study was set out to characterize size distributions of oil mists in three workplace atmospheres of the forming, threading, and heat treatment in a fastener manufacturing industry and to assess their exposures to workers. Particle size segregating samplings were conducted on the workplace atmospheres of the three selected industrial processes by using the modified Marple 8-stage cascade impactor (m-Marple). We found that mass median aerodynamic diameter (MMAD) of the fine mode and coarse mode fell to the range 0.309-0.501 microm and 8.16-13.0 microm, respectively. The fractions of inhaled particles exposed to different regions of the respiratory tracts found that the alveolar region was consistently higher than both head and tracheobronchial regions in all three studied exposure groups. Personal inhalable oil mist samplings were conducted on workers in the three selected processes revealed their exposure levels as: threading workers (2.11 mg/m3)>forming workers (1.58 mg/m3)>heat treatment workers (0.0801 mg/m3). The estimated respirable exposure concentrations for both forming and threading workers (1.34 mg/m3 and 1.40 mg/m3, respectively) were higher than the level known for "increased risk of pulmonary injury" (0.20 mg/m3) suggesting that appropriate control measures should be taken to reduce their exposures to the oil mists of the respirable fraction immediately. PMID:17222970

Chen, Mei-Ru; Tsai, Perng-Jy; Chang, Chih-Ching; Shih, Tung-Sheng; Lee, Wen-Jhy; Liao, Pao-Chi

2006-12-20

390

A study of gas/particle partitioning of SVOCs in the tropical atmosphere of Southeast Asia  

NASA Astrophysics Data System (ADS)

Gas- and particle-phase polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) were collected at a tropical site in Southeast Asia over 12-h periods during November and December 2006 to determine their gas/particle distributions by analyzing integrated quartz filter and polyurethane foam samples. Gas/particle partitioning coefficients, Kp, were calculated, and their relationship with the subcooled liquid vapor pressure pLo for both PAHs and PCBs was investigated. The regressions of log Kp vs. log pLo for most of samples gave high correlations for both PAHs and PCBs and the slopes were statistically shallower than -1, but they were relatively steeper than those obtained in temperate zones of the Northern Hemisphere. By comparison, the particle-bound fraction of low molecular weight (LMW) PAHs was underestimated by both Junge-Pankow adsorption and KOA (octanol-air partition coefficient) absorption models, while the predicted values agree relatively better with those observed ones for high molecular weight (HMW) PAHs. In addition, the adsorption onto the soot phase (elemental carbon) predicted accurately the gas/particle partitioning of PAHs, especially for LMW compounds. On the other hand, the KOA absorption model using the measured organic matter fraction ( fOM) value fitted the PCB data much better than the adsorption model did, indicating the sorption of nonpolar compounds to aerosols might be dominated by absorption into organic matters in this area.

He, Jun; Balasubramanian, Rajasekhar

391

A predictive model for adsorptive gas partitioning of SOCs on fine atmospheric inorganic dust particles  

SciTech Connect

The adsorptive gas/particle (G/P) partitioning of semivolatile organic compounds (SOCs) on inorganic Arizona road dust was studied using outdoor Teflon film chambers. Physicochemical parameters from SOC molecular structural information were implemented to describe nonspecific and specific interactions relating to G/P adsorption. Experimental partitioning data were successfully interpreted using physicochemical parameters such as vapor pressure, molecular polarizability, and solute solvation. To evaluate the effect of surface functional groups on the adsorptive G/P partitioning of SOCs, untreated and baked Arizona road dust particles were used. The partitioning coefficients, K{sub p}, for a range of different SOCs on baked dust particles and on untreated dust particles were measured from simultaneous experiments in two outdoor Teflon film chambers that were operated at the same temperature and humidity conditions. K{sub p} values for the two different surface properties of untreated and baked particles were better predicted by including solute solvation parameters than just by vapor pressure alone.

Jang, M.; Kamens, R.M. [Univ. of North Carolina, Chapel Hill, NC (United States). Dept. of Environmental Sciences and Engineering

1999-06-01

392

Sterilization of Materials with a One Atmosphere Uniform Glow Discharge Plasma.*  

NASA Astrophysics Data System (ADS)

The relatively recent development of the One Atmosphere Uniform Glow Discharge Plasma sterilization technique at the UTK Plasma Science Laboratory has produced initial results which indicate that the technique may have commercial potential. We have shown that active species in a OAUGDP can be applied to the sterilization of fabrics, films, solid materials, and microbiological culture media. With a OAUGDP, we can eliminate the vacuum system which enforces batch processing and requires a continuous input of electrical power. With a OAUGDP, the exposure time is as little as 15 seconds. Sterilization of microorganisms with a kill ratio of 10E6 or higher, can be achieved with minimal unwanted byproducts and at less expense, compared to such conventional sterilization methods as autoclaving, ethylene oxide, or low pressure plasma treatment. This paper discusses the sterilization mechanisms of this new technique, and compares its advantages and disadvantages with other widely used techniques. ^1 Department of Microbiology, UTK ^2 UTK Textiles and Nonwovens Development Center (TANDEC) Research supported in part by the UTK Textiles and Nonwovens Development Center and UTK Center for Materials Processing.

Ku, Yongmin; Brickman, C.; Tosh, K.; Kelly-Wintenberg, K.; Montie, T. C.; Tsai, P.; Wadsworth, L.; Roth, J. Reece

1996-11-01

393

Generation of sub-micron particles and secondary pollutants from building materials by ozone reaction  

NASA Astrophysics Data System (ADS)

This study reports results from two different experiments examining reactions between ozone and common building materials that can lead to the formation of secondary products and particulate-phase materials. Monitored species include sub-micron particles and volatile organic compounds (VOCs). In the first set of experiments, various building materials were placed in a 20 L stainless-steel chamber and exposed to ozone. The materials included expanded polystyrene, a natural rubber adhesive, cedar board, Japanese Cyprus board and silver fir board, as well as d-limonene, which is a known constituent of certain woods and cleaning products. The combination of ozone and either d-limonene, cedar board or cypress board produced sub-micron particles, with most of the increase occurring in the size range of 0.01- 0.5?m diameter. This was not observed for the other materials. In the case of cedar board, the consequence of ozone exposure over an extended time interval was monitored. As the exposure time elapsed, the concentration of sub-micron particles moderately decreased. In the second set of experiments, unwaxed or waxed plastic tiles were placed in the 20 L chamber and exposed to ozone. Sub-micron particles and organic compounds were measured during the course of the experiments. In the case of the waxed tile, the number of 0.01- 1.0?m size particles grew about 50×108particlesm-3; particle growth was significantly less for the un-waxed tile. For both the waxed and un-waxed tiles, the emission rates of heptane, nonane, nonanal, and decanal increased after ozone was added to the supply air. (However, it is not clear if some or all of this production was due to ozone reacting with the sorbent used for sampling or with compounds captured by the sorbent.) This study provides further evidence that ozone-initiated reactions with building materials can be a significant source of both sub-micron particles and secondary organic compounds in indoor environments.

Aoki, Taisuke; Tanabe, Shin-ichi

394

PARTICLES OF DIFFERENCE.  

SciTech Connect

It is no longer appropriate, if it ever was, to think of atmospheric aerosols as homogeneous spheres of uniform composition and size. Within the United States, and even more globally, not only the mass loading but also the composition, morphology, and size distribution of atmospheric aerosols are highly variable, as a function of location, and at a given location as a function of time. Particles of a given aerodynamic size may differ from one another, and even within individual particles material may be inhomogeneously distributed, as for example, carbon spherules imbedded in much larger sulfate particles. Some of the particulate matter is primary, that is, introduced into the atmosphere directly as particles, such as carbon particles in diesel exhaust. Some is secondary, that is, formed in the atmosphere by gas-to-particle conversion. Much of the material is inorganic, mainly sulfates and nitrates resulting mainly from energy-related emissions. Some of the material is carbonaceous, in part primary, in part secondary, and of this material some is anthropogenic and some biogenic. While the heterogeneity of atmospheric aerosols complicates the problem of understanding their loading and distribution, it may well be the key to its solution. By detailed examination of the materials comprising aerosols it is possible to infer the sources of these materials. It may be possible as well to identify specific health impairing agents. The heterogeneity of aerosol particles is thus the key to identifying their sources, to understanding the processes that govern their loading and properties, and to devising control strategies that are both effective and efficient. Future research must therefore take cognizance of differences among aerosol particles and use these differences to advantage.

SCHWARTZ,S.E.

2000-09-21

395

Determination of Element Abundances in Solar Atmosphere and Solar Flare Accelerated Particles Using Gamma Ray Spectroscopy  

Microsoft Academic Search

We determined elemental abundances in the solar atmosphere using SMM gamma ray line data. The abundances show a pronounced FIP (first ionization potential) effect. The abundance ratios of the low FIP to high FIP elements (Mg\\/O, Si\\/O, Fe\\/O) are enhanced compared to their photospheric values and are consistent with coronal values. On the other hand, the value of Ne\\/O (both

N. Mandzhavidze; R. Ramaty

1996-01-01

396

Seasonal Abundance of Particle-Phase Organic Pollutants in an Urban\\/Industrial Atmosphere  

Microsoft Academic Search

Polycyclic aromatic hydrocarbons (PAHs); their derivatives nitro, and methyl-PAHs; n-alkanes; and organic acids were investigated in the aerosol samples collected during two field campaigns conducted at three\\u000a sampling stations in an industrialized city in southern Italy. The main sources affecting the atmosphere and its toxicity\\u000a were investigated by means of the diagnostic ratios of: specific particulate-phase PAHs, marker compounds among

Patrizia Di Filippo; Carmela Riccardi; Donatella Pomata; Claudio Gariazzo; Francesca Buiarelli

2010-01-01

397

Lidar studies of particles and temperatures of the atmosphere: First results from National Central University lidar  

Microsoft Academic Search

With a Rayleigh and Mie scattering lidar, installed at the Central University in Chung-Li, Taiwan (25°N, 121°E), we studied the high clouds, aerosols, and temperatures of the atmosphere in the 15-60 km region since July, 1993. High clouds located near the tropopause were observed consistently. The clouds had stable structure and persisted for hours. One of the clouds presented had

J. B. Nee; G. B. Wang; P. C. Lee; S. B. Lin

1995-01-01

398

Lidar studies of particles and temperatures of the atmosphere: First results from National Central University lidar  

Microsoft Academic Search

With a Rayleigh and Mie scattering lidar, installed rat the Central University in Chung-Li, Taiwan (25øN, 121øE), we studied the high clouds, aerosols, and temperatures of the atmosphere in the i5-60 km region since July, 1993. High clouds located near the tropopause were observed consistently. The clouds had stable structure and persisted for hours. One of the clouds presented had

J. B. Nee; G. B. Wang; P. C. Lee; S. B. Lin

1995-01-01

399

Interferometric measurement of particle densities in cascaded arcs at atmospheric pressure  

Microsoft Academic Search

Two wavelength interferometry is applied to a cascaded arc burning in Ar, Xe and He at atmospheric pressure. The interferometer is of the Mach-Zehnder type with a He-Ne-laser as a light source. The refractive index of the plasma is measured at the wavelengths lambda 1=6328 AA and lambda 2=33912 AA and is compared to calculated data. A contribution of excited

D. Baum; J. Hackmann; J. Uhlenbusch

1975-01-01