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Sample records for particles characteristics role

  1. Characteristics and physiological role of surfactant-like particles secreted by entrocytes.

    PubMed

    Turan, Aasma; Gupta, Shiffalli; Mahmood, Akhtar

    2006-07-01

    Intestinal epithelium secretes novel unilamellar membranes having characteristics similar to lung surfactants and thus has been named Surfactant-like particles (SLP). The chemical analysis of the membranes revealed cholesterol/phospholipid molar ratio of 0.68-0.78, which is much distinct from that of the underlying microvillus membranes (1.34-1.49). The membrane contains 4-6 proteins with a molar weight of 30-120 kDa and is enriched with alkaline phosphatase, contains low amounts of disaccharidases but no Na+, K(+)-ATPase activity. The secretion of SLP is stimulated by fat feeding. Chronic ethanol ingestion also induces the formation of SLP in rat intestine. A number of physiological functions have been attributed to SLP, which include: (i) as a protective lubricant in intestinal lumen, (ii) a role in triacylglycerol transport, (iii) as a vehicle for the transport of luminal proteins into blood, (iv) as a stratum for the adhesion of microorganisms in intestinal lumen, and (v) a role in trans-signalling mechanism across the basolateral surface of enterocytes. PMID:16872040

  2. Instillation versus Inhalation of Multiwalled Carbon Nanotubes: Exposure-Related Health Effects, Clearance, and the Role of Particle Characteristics

    PubMed Central

    2015-01-01

    Inhaled multiwalled carbon nanotubes (MWCNTs) may cause adverse pulmonary responses due to their nanoscale, fibrous morphology and/or biopersistance. This study tested multiple factors (dose, time, physicochemical characteristics, and administration method) shown to affect MWCNT toxicity with the hypothesis that these factors will influence significantly different responses upon MWCNT exposure. The study is unique in that (1) multiple administration methods were tested using particles from the same stock; (2) bulk MWCNT formulations had few differences (metal content, surface area/functionalization); and (3) MWCNT retention was quantified using a specialized approach for measuring unlabeled MWCNTs in rodent lungs. Male Sprague–Dawley rats were exposed to original (O), purified (P), and carboxylic acid functionalized (F) MWCNTs via intratracheal instillation and inhalation. Blood, bronchoalveolar lavage fluid (BALF), and lung tissues were collected at postexposure days 1 and 21 for quantifying biological responses and MWCNTs in lung tissues by programmed thermal analysis. At day 1, MWCNT instillation produced significant BALF neutrophilia and MWCNT-positive macrophages. Instilled O- and P-MWCNTs produced significant inflammation in lung tissues, which resolved by day 21 despite MWCNT retention. MWCNT inhalation produced no BALF neutrophilia and no significant histopathology past day 1. However, on days 1 and 21 postinhalation of nebulized MWCNTs, significantly increased numbers of MWCNT-positive macrophages were observed in BALF. Results suggest (1) MWCNTs produce transient inflammation if any despite persistence in the lungs; (2) instilled O-MWCNTs cause more inflammation than P- or F-MWCNTs; and (3) MWCNT suspension media produce strikingly different effects on physicochemical particle characteristics and pulmonary responses. PMID:25144856

  3. Instillation versus inhalation of multiwalled carbon nanotubes: exposure-related health effects, clearance, and the role of particle characteristics.

    PubMed

    Silva, Rona M; Doudrick, Kyle; Franzi, Lisa M; TeeSy, Christel; Anderson, Donald S; Wu, Zheqiong; Mitra, Somenath; Vu, Vincent; Dutrow, Gavin; Evans, James E; Westerhoff, Paul; Van Winkle, Laura S; Raabe, Otto G; Pinkerton, Kent E

    2014-09-23

    Inhaled multiwalled carbon nanotubes (MWCNTs) may cause adverse pulmonary responses due to their nanoscale, fibrous morphology and/or biopersistance. This study tested multiple factors (dose, time, physicochemical characteristics, and administration method) shown to affect MWCNT toxicity with the hypothesis that these factors will influence significantly different responses upon MWCNT exposure. The study is unique in that (1) multiple administration methods were tested using particles from the same stock; (2) bulk MWCNT formulations had few differences (metal content, surface area/functionalization); and (3) MWCNT retention was quantified using a specialized approach for measuring unlabeled MWCNTs in rodent lungs. Male Sprague-Dawley rats were exposed to original (O), purified (P), and carboxylic acid functionalized (F) MWCNTs via intratracheal instillation and inhalation. Blood, bronchoalveolar lavage fluid (BALF), and lung tissues were collected at postexposure days 1 and 21 for quantifying biological responses and MWCNTs in lung tissues by programmed thermal analysis. At day 1, MWCNT instillation produced significant BALF neutrophilia and MWCNT-positive macrophages. Instilled O- and P-MWCNTs produced significant inflammation in lung tissues, which resolved by day 21 despite MWCNT retention. MWCNT inhalation produced no BALF neutrophilia and no significant histopathology past day 1. However, on days 1 and 21 postinhalation of nebulized MWCNTs, significantly increased numbers of MWCNT-positive macrophages were observed in BALF. Results suggest (1) MWCNTs produce transient inflammation if any despite persistence in the lungs; (2) instilled O-MWCNTs cause more inflammation than P- or F-MWCNTs; and (3) MWCNT suspension media produce strikingly different effects on physicochemical particle characteristics and pulmonary responses. PMID:25144856

  4. HVOF particle flow field characteristics

    SciTech Connect

    Swank, W.D.; Fincke, J.R.; Haggard, D.C.; Irons, G.; Bullock, R.

    1994-12-31

    The effect of varying fuel/oxygen mixture ratio and combustion chamber pressure on the sprayed particle temperature and velocity in the supersonic, high pressure HVOF process is examined. Particle temperature is shown to correlate to the fuel/oxygen mixture and particle velocity is a function of combustion chamber pressure. inconel 718 coatings were fabricated at the same conditions as the particle measurements. High particle velocities resulted in high micro hardness. Deposition efficiency is a function of both particle temperature and velocity. The optimal deposition efficiency occurs at an average particle temperature which is below the melting point of Inconel 718 and the lowest velocity investigated. Oxide content is a function of substrate temperature and not entrained air or excess combustion oxygen.

  5. Aerodynamic characteristics of popcorn ash particles

    SciTech Connect

    Cherkaduvasala, V.; Murphy, D.W.; Ban, H.; Harrison, K.E.; Monroe, L.S.

    2007-07-01

    Popcorn ash particles are fragments of sintered coal fly ash masses that resemble popcorn in low apparent density. They can travel with the flow in the furnace and settle on key places such as catalyst surfaces. Computational fluid dynamics (CFD) models are often used in the design process to prevent the carryover and settling of these particles on catalysts. Particle size, density, and drag coefficient are the most important aerodynamic parameters needed in CFD modeling of particle flow. The objective of this study was to experimentally determine particle size, shape, apparent density, and drag characteristics for popcorn ash particles from a coal-fired power plant. Particle size and shape were characterized by digital photography in three orthogonal directions and by computer image analysis. Particle apparent density was determined by volume and mass measurements. Particle terminal velocities in three directions were measured in water and each particle was also weighed in air and in water. The experimental data were analyzed and models were developed for equivalent sphere and equivalent ellipsoid with apparent density and drag coefficient distributions. The method developed in this study can be used to characterize the aerodynamic properties of popcorn-like particles.

  6. Ultrafine particle characteristics in seven industrial plants.

    PubMed

    Elihn, Karine; Berg, Peter

    2009-07-01

    Ultrafine particles are considered as a possible cause of some of the adverse health effects caused by airborne particles. In this study, the particle characteristics were measured in seven Swedish industrial plants, with a special focus on the ultrafine particle fraction. Number concentration, size distribution, surface area concentration, and mass concentration were measured at 10 different job activities, including fettling, laser cutting, welding, smelting, core making, moulding, concreting, grinding, sieving powders, and washing machine goods. A thorough particle characterization is necessary in workplaces since it is not clear yet which choice of ultrafine particle metric is the best to measure in relation to health effects. Job activities were given a different order of rank depending on what particle metric was measured. An especially high number concentration (130 x 10(3) cm(-3)) and percentage of ultrafine particles (96%) were found at fettling of aluminium, whereas the highest surface area concentration (up to 3800 mum(2) cm(-3)) as well as high PM10 (up to 1 mg m(-3)) and PM1 (up to 0.8 mg m(-3)) were found at welding and laser cutting of steel. The smallest geometric mean diameter (22 nm) was found at core making (geometric standard deviation: 1.9). PMID:19447849

  7. HVOF: Particle, flame diagnostics and coating characteristics

    SciTech Connect

    Kowalsky, K.A.; Marantz, D.R. ); Smith, M.F.; Oberkampf, W.L. )

    1990-01-01

    Dual focus laser velocimetry (L2F), photographic techniques, and pressure measurements were used to investigate particle and flame characteristics of a high velocity oxygen/fuel (HVOF) flame spray gun known as CDS''. Velocities of alumina, tungsten carbide, and Triballoy particles within the HVOF effluent stream have been measured using L2F techniques. Photographs of the exiting gases were used to determine the local Mach numbers within the gas stream. Measurements of Mach angles in the photographs were used to determine the actual gas velocity in the free jet of the device. Pressure measurements were made on the HVOF device which enabled calculations of the gas content, R, and the specific heat ratio, {kappa}. These calculations combined with estimates of gas temperature are used to calculate gas velocities at Mach 1 (nozzle exit). The HVOF device was used to produce dense WC/12 wt. % Co and Triballoy T-400 coatings. For the two gas flow conditions examined, higher hardness values and densities were observed for coatings deposited at the higher gas flow rates. 1 ref., 8 figs., 3 tabs.

  8. Characteristics of particle ropes in coal pipes

    SciTech Connect

    Levy, E.; Yilmaz, A.

    1998-07-01

    Particle ropes, regions in the flow with extremely high particle concentrations, are formed at elbows in coal pipes in pulverized coal boilers. This paper describes a study of the formation of ropes and of rope breakup and dispersion downstream of the elbow exit. The results show a strong influence of elbow radius on the rope formation process and rope dispersion. Average conveying velocity and air-to-fuel ratio also play a role in controlling rope strength at the elbow exit and rate of dispersion downstream of the elbow. The experiments and computer simulations both show a single elbow forms a stationary rope which is symmetrically positioned in the pipe at the outer wall. Ropes produced by two or more closely spaced elbows form a stationary rope which spirals around the pipe perimeter. Measurements with isokinetic extraction instruments have large negative bias errors resulting form the presence of strong ropes. This error decreases with distance from the elbow exit as the rope disintegrates and disperses.

  9. Characteristics of aerosolized ice forming marine biogenic particles

    NASA Astrophysics Data System (ADS)

    Alpert, Peter A.

    Ice particles are ubiquitous in the atmosphere existing as the sole constituents of glaciated cirrus clouds or coexisting with supercooled liquid droplets in mixed-phase clouds. Aerosol particles serving as heterogeneous ice nuclei for ice crystal formation impact the global radiative balance by modification of cloud radiative properties, and thus climate. Atmospheric ice formation is not a well understood process and represents great uncertainty for climate prediction. The oceans which cover the majority of the earth's surface host nearly half the total global primary productivity and contribute to the greatest aerosol production by mass. However, the effect of biological activity on particle aerosolization, particle composition, and ice nucleation is not well established. This dissertation investigates the link between marine biological activity, aerosol particle production, physical/chemical particle characteristics, and ice nucleation under controlled laboratory conditions. Dry and humidified aerosol size distributions of particles from bursting bubbles generated by plunging water jets and aeration through frits in a seawater mesocosm containing bacteria and/or phytoplankton cultures, were measured as a function of biological activity. Total particle production significantly increases primarily due to enhanced aerosolization of particles ≤100 nm in diameter attributable to the presence and growth of phytoplankton. Furthermore, hygroscopicity measurements indicate primary organic material associated with the sea salt particles, providing additional evidence for the importance of marine biological activity for ocean derived aerosol composition. Ice nucleation experiments show that these organic rich particles nucleate ice efficiently in the immersion and deposition modes, which underscores their importance in mixed-phase and cirrus cloud formation processes. In separate ice nucleation experiments employing pure cultures of Thalassiosira pseudonana, Nannochloris

  10. Some characteristics of fine beryllium particle combustion

    NASA Astrophysics Data System (ADS)

    Davydov, D. A.; Kholopova, O. V.; Kolbasov, B. N.

    2007-08-01

    Beryllium dust will be produced under plasma interaction with beryllium armor of the first wall in ITER. Exothermal reaction of this dust with water steam or air, which can leak into the reactor vacuum chamber in some accidents, gives concern in respect to reactor safety. Results of studies devoted to combustion of fine beryllium particles are reviewed in the paper. A chemically active medium and elevated temperature are prerequisite to the combustion of beryllium particles. Their ignition is hampered by oxide films, which form a diffusion barrier on the particle surface as a result of pre-flame oxidation. The temperature to initiate combustion of particles depends on flame temperature, particle size, composition of combustible mixture, heating rate and other factors. In mixtures enriched with combustible, the flame temperature necessary to ignite individual particles approaches the beryllium boiling temperature.

  11. CHARACTERISTICS OF SINGLE PARTICLE COAL COMBUSTION

    EPA Science Inventory

    The paper discusses the measurement of the burning history of single coal particles, using a two-color optical pyrometer. rom intensity traces at two wavelengths, information on burning times and temperatures, the duration of a volatile flame, and projected areas was obtained for...

  12. [Characteristic of Ultrafine Particles Transferring Through Building Envelopes].

    PubMed

    Sun, Zai; Chen, Qiu-fang; Cai, Zhi-liang; Yang, Wen-jun; Wang, Han

    2015-04-01

    Penetration and transmission characteristics of outdoor particulate matter through building envelope structure into indoor and its influencing factors were studied by experimental and numerical simulation methods. With the aid of fast mobility particle spectrometer (fast mobility particle sizer, FMPS), particle number concentrations were measured and particle penetration rates were obtained. The effects of slit size and flow pressure on the infiltration process were studied. Compared with numerical simulation and experimental results, the trend was consistent. Experiment and simulation results showed that when the slit was 1 mm high, the penetration rate of particulates with small particle size was small. Its leading influence factor was Brownian diffusion movement, with the increase of particle size, the penetration rate increased. Particle penetration rate was enhanced with the increase of inlet pressure and particle size, but decreased with the increase of slit length. Simulation results showed that the particle penetration rate was enhanced with the increase of slit height. Among all the factors, slit height was the dominant one. When the particle size was more than 30 nm, the penetration rate was close to 1. When the slit height was reduced to 0.25 mm, the penetration rate of particles with size of near 300 nm reached the maximum of 0.93. With the increase of the particle size, particle penetration rate showed a trend of decrease, and gravity settling began to dominate. The experiment result showed that when the slit height changed, the dominant factors of particles subsidence to the wall were changed. At low concentration in a certain range, the particle number concentration had little effect on the penetration rate. The range of particle number concentration of inside and outside I/O ratio was 0.69- 0.73. The correlation coefficient R2 was 0.99. The linear correlation was obvious. The particle penetration rate in slit straight way was significantly greater

  13. Fluidization characteristics of Biobone particles used for biocatalysts

    SciTech Connect

    Ellis, N.; Margaritis, A.; Briens, C.L.; Bergougnou, M.A.

    1996-01-01

    Liquid-solid fluidization characteristics of irregularly shaped Biobone particles were studied in a fluidized bioreactor column 2.35 m high and 0.1 m dia. The wet Biobone particles had a density of 1,890 kg/m{sup 3}. Two size ranges were studied: 1.70--2.36 mm and 1.25--2.36 mm. The Biobone is a natural cheap material composed of collagen, which is a strong protein structure, embedded with microcrystals of hydroxy apatite and calcium phosphate, and it is an excellent matrix of commercial importance used for the immobilization of enzymes, whole cells and other biocatalysts. Fluidization characteristics of Biobone particles, which include measurements of pressure drops, holdups, minimum fluidization velocities, particle entrainment, and residence time distributions at different water superficial velocities, are reported. Because of the highly irregular shape of Biobone particles, new fluidization behavior was observed, which was much different from the fluidization behavior of spherical particles reported in the literature. A new channeling index is proposed to quantify the channeling characteristics of fluidized Biobone particles, and a new parameter was developed to distinguish the transition between fixed and fluidized states of the Biobone particles. Fluidized bioreactor systems are used in bioprocessing for the production of high-value medicinal products, ethanol and beer production, food processing and beverage, wastewater treatment, and other environmental applications.

  14. Growing Characteristics of Fine Ice Particles in Surfactant Solution

    NASA Astrophysics Data System (ADS)

    Suzuki, Hiroshi; Nakayama, Kosuke; Komoda, Yoshiyuki; Usui, Hiromoto; Okada, Kazuto; Fujisawa, Ryo

    Time variation characteristics of ice particles in a surfactant solution have been investigated. The effect of surfactants on corrosion characteristics was also studied. The results were compared with those treated with poly(vinyl alcohol). From the results, the present surfactant, cetyl dimethyl betaine was not found to be effective on preventing Ostward ripening of ice particles as poly(vinyl alcohol) showed. Then, it was concluded some effective technology has to be installed with surfactants when this surfactant treatment is realized. On the corrosion characteristics, it was found that the present surfactant shows the same level as tap water.

  15. The local characteristic function of interplanetary particle propagation

    NASA Technical Reports Server (NTRS)

    Green, G.; Schlueter, W.

    1985-01-01

    An easily measurable intensity function which characterizes the interplanetary propagation of charged solar flare particles is presented. This function is nearly time invariant during a solar event despite the large variations of intensity and anisotropy, but varies from event to event. It characterizes the systematic and stochastic forces of the interplanetary magnetic field which focus and scatter the particles in pitch angle. The model of focused transport shows that this function is essentially determined by the local shape and amplitude of the pitch angle diffusion coefficient kappa (mu) and by the local value of the focusing length. The time profile of the solar particle injection is typically of negligible influence. The local characteristic function may be used as a powerful new tool for a systematic analysis of flare particle angular distributions, Examples are given.

  16. Particle rebound characteristics of turbomachinery cascade leading edge geometry

    NASA Astrophysics Data System (ADS)

    Siravuri, Sastri

    The objective of this research work is to investigate and understand the complex phenomena associated with the mechanism of particle impacts on turbomachinery cascade leading edge geometry. At present, there is a need for experimental work in basic and applied research to find out the parameters that are relevant to particle rebound characteristics on turbomachinery blades. In the present work, experiments were conducted with air velocity at 15 m/s (˜50 ft/sec) and at 30 m/s (˜100 ft/sec) using high-speed photography and Laser Doppler Velocimetry (LDV). Silica sand particles of 1000--1500 micron size were used for this study. In the present investigation, particle rebound data was obtained for cylindrical targets with radius of curvature representative of leading edge geometry (cylinder diameter = 4.5mm & 6.5 mm) using LDV. The numerical simulations, which are based on non-linear dynamic analysis, were also performed using the finite element code DYNA3-D. Several different material models viz elastic-elastic, elastic-plastic, elastic-plastic with friction & isotropic-elastic-plastic with dynamic friction and particle rotation were used in the DYNA3-D numerical analysis. The computational results include a time history of the displacement, stress and strain profiles through the particle collision. Numerical results are presented for the rebound conditions of spherical silica sand particle for different pre-collision velocities. The computed particle restitution coefficients, after they reach steady rebound conditions, are compared with experimental results obtained from LDV. A probabilistic model was developed to incorporate the uncertainties in the impact velocity in the numerical model. Histograms and Cumulative Distribution Functions (CDFs) for impact velocity were obtained from experimental LDV data. Ten randomly selected probabilities for each impact angle were used to calculate the impact velocity from cumulative distribution function. This randomly selected

  17. Rebound characteristics for ash particles impacting a planar surface

    NASA Astrophysics Data System (ADS)

    Dong, Ming; Li, Sufen; Han, Jian; Xie, Jun

    2013-06-01

    The formation of ash deposition on the heat transfer tubes in a boiler reduces the heat transfer coefficient by about 25%. Because of these fouling layers, the efficiency with which energy can be absorbed from flue gases is reduced. The growth of ash deposition is strongly dependent on the interaction of the incident particle with the surface of heat transfer tubes. In this study the interaction is modeled as the outcome of collision between an incident fly ash particle and planar surface that represents a heat transfer surface. The present paper focuses on the applicability of the experimental results to indicate the rebound characteristics of fly ash particles impacting a planar surface. This is studied by impaction experiments of fly ash particles from the power plant dust, under various particle diameters and with different velocities (ranging from 0.1 to 20 m/s). The experiments are carried out in an atmospheric column, and using a digital camera system, individual impacts are recorded. Furthermore, the measured coefficient of restitution values can be predicted by a dynamic simulation model.

  18. Fluoroalkyl-functionalized silica particles: synthesis, characterization, and wetting characteristics.

    PubMed

    Campos, Raymond; Guenthner, Andrew J; Haddad, Timothy S; Mabry, Joseph M

    2011-08-16

    Fluoroalkyl-functionalized silica particles for use in nonwetting surfaces were prepared by treatment of silica particles with fluoroalkyl-functional chlorosilanes. Both fumed and precipitated silica were studied, as well as the efficiency of surface coverage using mono-, di-, and trifunctional chlorosilanes. The most effective surface treatment was accomplished via the surface grafting of monofunctional chlorosilanes in the presence of preadsorbed dimethylamine under anhydrous conditions at room temperature. Confirmation of covalent attachment was accomplished via Fourier transform infrared (FT-IR) spectroscopy, while elemental analysis, thermogravimetric analysis, and nitrogen adsorption isotherms were used to determine grafting densities and additional key geometric characteristics of the grafted layer. The effect of residual silanol content on the moisture uptake properties of the modified silica particles was determined by measuring the water uptake of unbound particles, while liquid wetting properties were determined by dynamic contact angle analysis of elastomeric composites. Although residual silanol content was shown to effect wetting properties, results suggest that surface geometry dominates the performance of liquid-repellent surfaces. The potential use of fluoroalkyl-functionalized silica particles for hydrophobic and oleophobic applications is discussed. PMID:21728328

  19. Effect of magnesium on the burning characteristics of boron particles

    NASA Astrophysics Data System (ADS)

    Liu, Jian-zhong; Xi, Jian-fei; Yang, Wei-juan; Hu, You-rui; Zhang, Yan-wei; Wang, Yang; Zhou, Jun-hu

    2014-03-01

    Boron is an attractive fuel for propellants and explosives because of its high energy density. However, boron particles are difficult to combust because of inhibiting oxide layers that cover the particles. The use of magnesium as additives has been shown to promote boron oxidation. In this study, laser ignition facility and thermobalance were used to investigate the effect of magnesium on the burning characteristics of boron particles. The influences of magnesium addition on sample combustion flame, boron ignition delay time, boron combustion efficiency and initial temperature of boron oxidation. Results show that all Mg/B samples exhibit the same type of flame structure, i.e., a bright plume surrounded by green radiation which is interpreted as BO2 emission. The combustion flame intensity of a sample increases with the increasing magnesium content of boron particles. An increase in magnesium content results in a decrease and a subsequent increase in boron ignition delay time. (Mg/B)0.2 has a minimum ignition delay time of ~48 ms. Boron combustion efficiency increases with increasing magnesium addition. (Mg/B)0.5 shows a maximum boron combustion efficiency of ~64.2%. Magnesium addition decreases the initial temperature of boron oxidation.

  20. Electrostatic Characteristics of Materials Exposed to Martian Simulant Dust Particles

    NASA Astrophysics Data System (ADS)

    Calle, C. I.; Kim, H. S.; Young, S.; Jackson, D.; Lombardi, A. J.

    1998-11-01

    The Pathfinder mission to Mars identified Andesitic rock as the primary type of rock at the landing site. Several experiments were designed at NASA/Kennedy Space Center to determine the charging characteristics of common space materials exposed to small particles derived from those rocks. MARS-1, a Martian soil simulant prepared from Andesitic rocks by NASA/JSC was used in this work. Characterization of this simulant was made using scanning electron microscopy and inductively coupled argon plasma spectroscopy coupled with a carbon-sulfur detector. These results were compared to the Alpha Proton X-Ray Spectrometer analysis on Pathfinder. The simulant was found to be a suitable substitute for Martian soil for our purposes. Two experimental designs and methods to simulate the exposure of different materials to wind-blown dust were made. These designs permit dust particle delivery to samples at different speeds. Initial experiments made with these designs to determine their viability were promising.

  1. Particle characteristics and reduction behavior of synthetic magnetite

    NASA Astrophysics Data System (ADS)

    Ramadan, Wegdan; Zaki, Mohamed I.; Fouad, Nasr E.; Mekhemer, Gamal A. H.

    2014-04-01

    Two samples (S1 and S2) of magnetite were synthesized, using two different methods, and characterized by means of X-ray powder diffractometry, infrared and Mössbauer spectroscopy, N2 sorptiometry and electron microscopy. Particles of sample-S1 were found to be loosely agglomerated, micro-sized spheroids (200-350 nm) composed almost solely of highly aggregated (fused) crystallites (size averaged at 35 nm) of cubic-Fe3O4. In contrast, particles of sample-S2 were strongly agglomerated, nano-sized spheroids (25-30 nm) composed of slightly aggregated crystallites (size averaged at 11 nm) of cubic-Fe3O4 and noncrystalline domains made-up of FeO(OH) species. Temperature-programed reduction (TPR) profiles obtained for the two samples were similar in monitoring two peaks at >450 °C assignable to a two-step reduction of Fe3O4 (→FeO→Fe), but different in monitoring a peak at<450 °C only for the reduction of FeO(OH) (→Fe3O4) contained in sample-S2. However, curve fitting analysis of the TPR profiles and molecular stoichiometry calculations based on amounts of hydrogen consumed revealed that the two-step reduction of Fe3O4 is not straightforward. That is by resolving two consecutive pathways for each step and, hence, nonstoichiometric intermediate products whose composition was found to be critically controlled by the composition of the reducing gas atmosphere (5 or 80% H2/N2) and characteristics of the starting sample particles (chemical and phase composition, and, but to lesser extents, the agglomeration and average size).

  2. Personality Characteristics and Evaluation of Women's Role.

    ERIC Educational Resources Information Center

    Welsh, Mary C.; Hawker, James

    The relationships between several commonly utilized women's role questionnaires and several personality inventories was investigated. Undergraduates students (120 females, 80 males) completed several personality and sex-role questionnaires including the Personal Orientation Inventory (POI); Rotter's Locus of Control Scale (I-E), MAFERR Forms A, B,…

  3. Characteristics of sinking particles in the upper ocean at the Porcupine Abyssal Plain

    NASA Astrophysics Data System (ADS)

    Riley, Jennifer; Sanders, Richard; Achterberg, Eric

    2010-05-01

    Sinking particles play an important role in the biological carbon pump, transferring carbon from the surface to the deep ocean. Data from deep ocean sediment traps suggest biominerals influence particle settling velocity, by increasing their density. However it is unclear whether this biomineral facilitated sinking applies to the upper ocean and if shape also plays a critical role on the rate at which particles sink. Measurements of particle settling velocity, density and drag were made in order to determine their influences on the particle sinking rate in the upper water column. Samples were taken during a cruise in summer 2009 from the Porcupine Abyssal Plain (PAP site) in the northwest Atlantic. Particles were collected from the base of the mixed layer (approximately 50m) using the Marine Snow Catcher. This instrument samples 100L of water and collects any settling particles in a 5L base chamber over 2 - 3 hours. After settling, the top 95L of water was drained off and any particles collected in the base chamber were transferred to the lab. Particles were individually picked using a Pasteur pipette and subdivided, into categories on the basis of appearance. Settling experiments were conducted in a 2L glass measuring cylinder filled with surface sea water, kept at a constant temperature of 15° C. After each experiment particles were preserved individually in buffered formalin for high quality image analysis back on land. Calculations of both excess density and drag were undertaken using data from microscopic measurements. Five main particle categories were identified; (1) diffuse fluff aggregates, (2) dense fluff aggregates, (3) centred particles (fluff aggregated around a central biomineral test), (4) organisms (biomineralising protists including foraminifera) and (5) calcareous tests. Statistical analysis suggested a significant difference in the rate at which the centred and calcareous particles sank (approximately 248 m day-1 and 1070 m day-1respectively) in

  4. Influence of Coal Particle Size on Coal Adsorption and Desorption Characteristics

    NASA Astrophysics Data System (ADS)

    Zhang, Lei; Aziz, Naj; Ren, Ting; Nemcik, Jan; Tu, Shihao

    2014-10-01

    Accurate testing coal isotherm can play a significant role in the areas of coal seam gas drainage, outburst control, CO2 geo-sequestration, coalbed methane (CBM) and enhanced coalbed methane recovery (ECBM) etc. The effect of particle size on the CO2 and CH4 sorption capacity of bituminous coal from Illawarra, Australia was investigated at 35°C and at pressure up to 4 MPa. A unique indirect gravimetric apparatus was used to measure the gas adsorption and desorption isotherms of coal of different particle sizes ranging from around 150 urn to 16 mm. Langmuir model was used to analysis the experimental results of all gases. Coal particle size was found to have an apparent effect on the coal ash content and helium density results. Coal with larger particle size had higher ash content and higher helium density. The sorption isotherm was found to be highly sensitive with helium density of coal which was determined in the procedure of testing the void volume of sample cell. Hence, coal particle size had a significant influence on the coal sorption characteristics including sorption capacity and desorption hysteresis for CO2 and CH4, especially calculated with dry basis of coal. In this study, the 150-212 um (150 um) coal samples achieved higher sorption capacity and followed by 2.36-3.35 mm (2.4 mm), 8-9.5 mm (8 mm) and 16-19 mm (16 mm) particle size samples. However, the differences between different coal particles were getting smaller when the sorption isotherms are calculated with dry ash free basis. Test with 150 um coal samples were also found to have relatively smaller desorption hysteresis compared with the other larger particle size samples. The different results including adsorption/desorption isotherm, Langmuir parameters and coal hysteresis were all analysed with the CO2 and CH4 gases.

  5. Decoupling the Roles of Inertia and Gravity on Particle Dispersion

    NASA Technical Reports Server (NTRS)

    Groszmann, D. E.; Thompson, J. H.; Coppen, S. W.; Rogers, C. B.

    1999-01-01

    Inertial and gravitational forces determine a particle's motion in a turbulent flow field. Gravity plays the dominant role in this motion by pulling the particles through adjacent regions of fluid turbulence. To better understand and model how a particle's inertia effects its displacement, one must examine the dispersion in a turbulent flow in the absence of gravity. In this paper, we present the particle experiments planned for NASA's KC-135 Reduced-Gravity Aircraft, which generates microgravity conditions for about 20 seconds. We also predict the particle behavior using simulation and ground-based experiments. We will release particles with Stokes numbers of 0.1, 1, and 10 into an enclosed tank of near-isotropic, stationary, and homogenous turbulence. These particle Stoke numbers cover a broad range of flow regimes of interest. Two opposed grids oscillating back and forth generate the turbulent field in the tank with a range of turbulence scales that covers about three orders of magnitude and with turbulence intensities of about ten times the mean velocity. The motion of the particles will be tracked using a stereo image velocimetry technique.

  6. Encapsulation and Permeability Characteristics of Plasma Polymerized Hollow Particles

    PubMed Central

    Shahravan, Anaram; Matsoukas, Themis

    2012-01-01

    In this protocol, core-shell nanostructures are synthesized by plasma enhanced chemical vapor deposition. We produce an amorphous barrier by plasma polymerization of isopropanol on various solid substrates, including silica and potassium chloride. This versatile technique is used to treat nanoparticles and nanopowders with sizes ranging from 37 nm to 1 micron, by depositing films whose thickness can be anywhere from 1 nm to upwards of 100 nm. Dissolution of the core allows us to study the rate of permeation through the film. In these experiments, we determine the diffusion coefficient of KCl through the barrier film by coating KCL nanocrystals and subsequently monitoring the ionic conductivity of the coated particles suspended in water. The primary interest in this process is the encapsulation and delayed release of solutes. The thickness of the shell is one of the independent variables by which we control the rate of release. It has a strong effect on the rate of release, which increases from a six-hour release (shell thickness is 20 nm) to a long-term release over 30 days (shell thickness is 95 nm). The release profile shows a characteristic behavior: a fast release (35% of the final materials) during the first five minutes after the beginning of the dissolution, and a slower release till all of the core materials come out. PMID:22929119

  7. Role of quantum statistics in multi-particle decay dynamics

    SciTech Connect

    Marchewka, Avi; Granot, Er’el

    2015-04-15

    The role of quantum statistics in the decay dynamics of a multi-particle state, which is suddenly released from a confining potential, is investigated. For an initially confined double particle state, the exact dynamics is presented for both bosons and fermions. The time-evolution of the probability to measure two-particle is evaluated and some counterintuitive features are discussed. For instance, it is shown that although there is a higher chance of finding the two bosons (as oppose to fermions, and even distinguishable particles) at the initial trap region, there is a higher chance (higher than fermions) of finding them on two opposite sides of the trap as if the repulsion between bosons is higher than the repulsion between fermions. The results are demonstrated by numerical simulations and are calculated analytically in the short-time approximation. Furthermore, experimental validation is suggested.

  8. Characteristics of meso-particles formed in coagulation process causing irreversible membrane fouling in the coagulation-microfiltration water treatment.

    PubMed

    Ding, Q; Yamamura, H; Murata, N; Aoki, N; Yonekawa, H; Hafuka, A; Watanabe, Y

    2016-09-15

    In coagulation-membrane filtration water treatment processes, it is still difficult to determine the optimal coagulation condition to minimize irreversible membrane fouling. In microfiltration (MF), meso-particles (i.e., 20 nm-0.5 μm) are thought to play an important role in irreversible membrane fouling, especially their characteristics of particle number (PN) and zeta potential (ZP). In this study, a new nanoparticle tracker combined a high-output violet laser with a microscope was developed to identify the physicochemical characteristics of these microscopic and widely dispersed meso-particles. The effects of pH and coagulant dose on ZP and PN of micro-particles (i.e., >0.5 μm) and meso-particles were investigated, and then coagulation-MF tests were conducted. As the result, irreversible membrane fouling was best controlled for both types of membranes, while meso-particle ZP approached zero at around pH 5.5 for both types of natural water. Since PN was greatest under these conditions, ZP is more important in determining the extent of irreversible membrane fouling than PN. However, the acidic condition to neutralize meso-particles is not suitable for actual operation, as considering residual aluminum concentration, pipe corrosion, and chlorination efficiency. It is therefore necessary to investigate coagulants or other methods for the appropriate modification of meso-particle characteristics. PMID:27262117

  9. Suspended Particles: Their Role in Estuarine Biogeochemical Cycles

    NASA Astrophysics Data System (ADS)

    Turner, A.; Millward, G. E.

    2002-12-01

    Suspended particles are instrumental in controlling the reactivity, transport and biological impacts of substances in aquatic environments, and provide a crucial link for chemical constituents between the water column, bed sediment and food chain. This article reviews the role of suspended particles in the chemical and biological cycling of trace constituents (trace metals, organo-metallic compounds and hydrophobic organic micropollutants; HOMs) in estuaries, with particular emphasis on the effects of and changes to particle reactivity and composition. The partitioning (or distribution coefficient, KD ) and bioavailability of chemical constituents, and assimilation efficiency (AE) of such by bivalve suspension feeders, are identified as key parameters requiring definition for accurate biogeochemical modelling, and the discussion centres around the determination of and controls on these parameters. Particle-water interactions encompass a variety of physical, biological, electrostatic and hydrophobic effects, and are largely dependent on the character and concentration of suspended particles and salinity. The salinity-dependence results from the competing and complexing effects of seawater ions for trace metals, and the compression of water in the presence of dissolved seawater ions and consequent salting out of neutral solute (HOMs, organo-metallic compounds and some trace metal complexes). The extent of biological solubilization of chemical constituents from suspended particles is dependent on the nature of chemical components of the gastro-intestinal environment and their interactions with ingested particles, and the physiological (e.g. gut passage time) and chemical (e.g. redox conditions and pH) constraints imposed on these interactions. Generally, chemicals that associate with fine, organic-rich particles (or, for some HOMs, fine inorganic particles), and desorb at pH 5-6 and/or complex with digestive enzymes or surfactants are most readily solubilized in the

  10. Characteristics of particle coagulation in an underground parking lot.

    PubMed

    Zhao, Yu; Kato, Shinsuke; Zhao, Jianing

    2015-12-01

    Particles in vehicle exhaust plumes in underground parking lots have adverse health effects due to the enclosed environment in which they are released and the temperature difference between the tailpipe and ambient environment; at the same time, particle coagulation might be obvious near the tailpipe in an underground parking lot. In the present study, airflow and temperature fields were calculated using the Realizable k-ε model, and the Eulerian particle transport model was selected in the numerical simulation of particle concentration dispersion. Polydisperse thermal coagulation due to Brownian collisions was employed to calculate the particle coagulation. The results show that particle coagulation rate and half-time were significant within 1 m from the tailpipe. The variations in the particle coagulation rate and half-time were similar, but their directions were opposite. Air exhaust time was nearly four times longer than averaged half-time and 40 times longer than minimum half-time. The peak particle diameter increased approximately 1.43 times due to coagulation. A double particle concentration at the tailpipe caused the fourfold rise in the particle coagulation rate in the distance ranging less than 1 m from the tailpipe. An increase in exhaust velocity at the tailpipe could shorten the obvious range of particle coagulation along the centerline of the tailpipe from 1 to 0.8 m in the study. PMID:26490941

  11. Numerical simulation of gas and particle flow field characteristics in HVOF guns

    SciTech Connect

    Yang, X.; Eidelman, S.; Lottati, I.

    1995-12-31

    The particle flow field characteristics in an HVOF gun are examined using numerical simulation techniques. The authors consider the particle injection, acceleration, convection heat transfer, and particle barrel interaction processes in a TAFA JP-5000 HVOF gun. Details of particle trajectories and temperature history as a function of particle size and other parameters are simulated and analyzed. A parameter study is conducted for different particle size, particle injection direction, and particle velocity. The number of distinct particle injection regimes was predicted and analyzed. Particle velocity and temperature at the exit of the barrel are listed. Using numerical simulation, the injection condition can be designed as a function of the set of flow parameters as well as particle properties, including particle size and material properties, to optimize the thermal spray process. A companion paper by the same authors in this proceedings presents a comprehensive analysis of the gas flow conditions for the HVOF gun.

  12. [Emission characteristics of fine particles from grate firing boilers].

    PubMed

    Wang, Shu-Xiao; Zhao, Xiu-Juan; Li, Xing-Hua; Wei, Wei; Hao, Ji-Ming

    2009-04-15

    Grate firing boilers are the main type of Chinese industrial boilers, which accounts for 85% of the industrial boilers and is one of the most important emission sources of primary air pollutants in China. In this study, five boilers in three cities were selected and tested to measure the emission characteristics of PM2.5, and gaseous pollutants were applied by a compact dilution sampling system, which was developed for this field study. Results showed that particles mass size distributions for the five industrial boilers presented single peak or double peak, former peaks near 0.14 microm and the later peaks after 1.0 microm; the cyclone dust remover and wet scrubber dust remover had effective removal efficiencies not only to PM2.5, but also to PM1.0; and under the condition of same control techniques, grate firing boiler with high capacity has less PM2.5 emission than the boiler with low capacity. In the PM2.5 collected from flue gases, SO4(2-) was the most abundant ion, accounted for 20%-40% of the PM2.5; and C was the most abundant element (7.5%-31.8%), followed by S (8.4%-18.7%). Carbon balance method was applied to calculate the emission factors of these pollutants. The emission factors of PM2.5, NO, and SO2 were in the range of 0.046-0.486 g x kg(-1), 1.63-2.47 g x kg(-1), 1.35-9.95 g x kg(-1) respectively. The results are useful for the emission inventory development of industrial boilers and the source analysis of PM2.5 in atmospheric environment. PMID:19544990

  13. Characteristics Students View as Important in Nurse Faculty Role Models.

    ERIC Educational Resources Information Center

    Cooper, Geneva

    Nursing students' views concerning the behavior of faculty role models were studied. The sample consisted of 75 senior-level baccalaureate nursing students, 69 females and 6 males. The theoretical framework for the research was role theory and Bandura's social learning and modeling theory. The Clinical Instructor Characteristics Ranking Scale…

  14. Characteristic Vertical Patterns Of Particles, Oxygen, And Chlorophyll Pigments In The North Pacific Gyre

    NASA Astrophysics Data System (ADS)

    Pak, Hasong

    1984-09-01

    Characteristic vertical patterns of suspended particles, dissolved oxygen, and chlorophyll pigments in the North Pacific Gyre indicate that particle and oxygen maxima are found together in the upper part of the seasonal thermocline. The chlorophyll maximum is typically found 30 to 50 m below the particle maximum. The depth of the particle and oxygen maxima respond closely to changes in the mixed layer depth, but the chlorophyll maximum does not. The chlorophyll maximum is not only separated from the oxygen and particle maxima, but it is also little affected by changes in the surface mixed layer, suggesting that the chlorophyll maximum has its own origin different from that of the particle and oxygen maxima. Profiles of dissolved oxygen show that the high oxygen concentration layer extends to approximately 400 m, well below the euphotic zone, which points out that the primary source of the oxygen in this layer is the surface waters sunk in the high latitude Pacific and spread out in the gyre. Photosynthetical production of oxygen would be added on to the already oxygen rich water, but its net contribution appears relatively small since the oxygen concentration in the euphotic zone is not significantly higher than in the water below. Such a secondary role of the photosynthetic production of oxygen is also supported by the nutrient profiles; nutrient concentrations are uniformly low in the surface water down to the nutracline at approximately 120 m allowing only a low photosynthesis rate. The most significant change in the vertical pattern of beam attenuation coefficients is expected from the seasonal progress in the mixed layer since the attenuation maximum and the mixed layer are related.

  15. PARTICLE TRANSMISSION CHARACTERISTICS OF AN ANNULAR DENUDER AMBIENT SAMPLING SYSTEM

    EPA Science Inventory

    Transmission measurements have been performed on URG 2000-30B glass annular denuders at 10 LPM using monodisperse particles in the 0.01 - 1 um dia size range. hrough control of the aerosol charge state, particle losses due to diffusion and electrostatic effects were separately me...

  16. Hydrothermally synthesized titanate nanostructures: impact of heat treatment on particle characteristics and photocatalytic properties.

    PubMed

    Kiatkittipong, Kunlanan; Scott, Jason; Amal, Rose

    2011-10-01

    The role titanate particle structure plays in governing its characteristics upon calcining and their ensuing influence on photocatalytic performance was investigated. Titanate nanotubes and nanoribbons were prepared by hydrothermal treatment of Aeroxide P25 and then calcined at temperatures in the range 200 - 800 °C. Heat treatment directly transformed the nanotubes to anatase while nanoribbon transformation to anatase occurred via a TiO(2)(B) intermediate phase. The nanoribbon structure also provided an increased resistance to sintering, allowing for retention of the original {010} facet of the titanate nanosheets up to 800 °C. The changing material properties with calcining were found to influence the capacity of the particles to photodegrade oxalic acid and methanol. The nanotubes provided an optimum photoactivity following calcination at 500 °C with this point representing a transition between the relative dominance of crystal phase and surface area on performance. The comparatively smaller initial surface area of the nanoribbons consigned this characteristic to a secondary role in influencing photoactivity with the changes to crystal phase dominating the continually improving performance with calcination up to 800 °C. The structural stability imparted by the nanoribbon architecture during calcination, in particular its retention of the {010} facet at temperatures >700 °C, advanced its photocatalytic performance compared with the nanotubes. This was especially the case for methanol photooxidation whose primary degradation mechanism relies on hydroxyl radical attack and was facilitated by the {010} facet. The effect was not as pronounced for oxalic acid due to its higher adsorption on TiO(2) and therefore greater susceptibility to oxidation by photogenerated holes. This study demonstrates that, apart from modulating sintering effects and changes to crystal phase, the titanate nanostructure influences particle crystallography which can be beneficial for

  17. Characteristics of metal particles in Apollo 16 rocks

    NASA Technical Reports Server (NTRS)

    Misra, K. C.; Taylor, L. A.

    1975-01-01

    It is pointed out that FeNi metal particles, composed predominantly of kamacite and ranging in size from less than 1 micron to more than 2 mm across, are ubiquitous in the lunar samples returned by the Apollo and Luna missions. The metal particles seldom exceed 1% of the volume of a lunar sample. However, their study has proven to be of considerable potential value in a number of aspects of lunar petrogenesis related to thermal history, equilibration temperatures, reduction processes and oxygen fugacities during magmatic crystallization and subsolidus reduction and oxidation, and the meteoritic component of lunar rocks based on Ni-Co contents of individual metal particles. Detailed studies have been conducted of the textures and compositions of the metal particles in 19 Apollo 16 rock samples representing material from the North Ray and the South Ray ejecta and/or fall-back blankets. It was found that the textures and compositions of the metal particles in the Apollo 16 rocks can be correlated with their host petrology.

  18. Magnetorheological characteristics of carbon nanotube wrapped carbonyl iron particles

    NASA Astrophysics Data System (ADS)

    Fang, Fei Fei; Choi, Byung Il; Choi, Hyoung Jin

    2009-02-01

    Carbonyl iron (CI) based magnetorheological (MR) fluid exhibits serious dispersion defect in general due to large density mismatch between CI particles and continuous medium, which restricts further MR application. Thus, various strategies were explored either to reduce the density or to prevent CI particle aggregation. Among them, polymer coating technology becomes more prevalent due to favorable morphology obtained and effective decrease in density by introducing polymeric shell; nevertheless, coating polymer on the surface of CI particles is always influenced by the selected grafting agent, mole ratio of reactant or the temperature of reaction. In this work, considering self-assembling trend of carbon nanotube (CNT) which exhibits similar density with polymer but better magnetic property due to the iron catalyst, we constructed a dense nest composed of CNT on the surface of CI particles by using 4-aminobenzoic acid (PABA) as a grafting agent under sonication. Thickness and morphology of the CNT nest were found to be related with sonication duration via SEM/TEM images. MR performances (yield stress behavior, shear viscosity) of the CI/CNT particles based MR fluid were investigated via controlled shear rate and controlled shear stress methods. Finally, sedimentation observation was checked to be improved.

  19. Measurement of thermal radiation scattering characteristics of submicron refractory particles.

    NASA Technical Reports Server (NTRS)

    Jacobs, W. R.; Williams, J. R.

    1971-01-01

    The differential scattering parameter has been measured for 0.04-micron tungsten particles in hydrogen and nitrogen at temperatures to 1080 K. The differential scattering parameter has also been measured for 0.1 micron tungsten, three types of carbon particles, and fly ash in nitrogen at temperatures to 1000 K. The 0.04 micron tungsten shows a temperature dependent total scattering parameter varying from around 4000 sq cm per g at room temperature to 7000 sq cm per g at 1088 K. The temperatures over which data were obtained are not high enough to confirm the temperature dependence of the total scattering parameter of tungsten.

  20. Job characteristics, flow, and performance: the moderating role of conscientiousness.

    PubMed

    Demerouti, Evangelia

    2006-07-01

    The present article aims to show the importance of positive work-related experiences within occupational health psychology by examining the relationship between flow at work (i.e., absorption, work enjoyment, and intrinsic work motivation) and job performance. On the basis of the literature, it was hypothesized that (a) motivating job characteristics are positively related to flow at work and (b) conscientiousness moderates the relationship between flow and other ratings of (in-role and out-of-role) performance. The hypotheses were tested on a sample of 113 employees from several occupations. Results of moderated structural equation modeling analyses generally supported the hypotheses. Motivating job characteristics were predictive of flow, and flow predicted in-role and extra-role performance, for only conscientious employees. PMID:16834474

  1. MEASURED FINE PARTICLE COLLECTION CHARACTERISTICS OF FOUR NOVEL SCRUBBERS

    EPA Science Inventory

    The report gives results of performance tests to determine the fine particle collection of four novel scrubbers: a Lone Star Steel Steam-Hydro Scrubber, an Aronetics (Chemico) Two-Phase Jet Scrubber, an Entoleter Centrifield Scrubber, and a CEA Variable-Throat Venturi Scrubber. T...

  2. Particle dynamics and resistivity characteristics in bifurcated current sheets

    NASA Astrophysics Data System (ADS)

    Andriyas, Tushar

    Charged particle chaos and its collective effects in different magnetic geometries are investigated in a sequence of various numerical experiments. The fields generated by the particles as a result of interaction with the background electric and magnetic fields is not accounted for in the simulation. An X-line is first used to describe the geometry of the magnetotail prior to magnetic reconnection and a study of the behavior of charged particles is done from a microscopic viewpoint. Another important geometry in the magnetotail prior to substorm onset is Bifurcated Current Sheet. The same analysis is done for this configuration. The existence of at least one positive Lyapunov exponent shows that the motion of the particles is chaotic. By using statistical mechanics, the macroscopic properties of this chaotic motion are studied. Due to particles being charged, an electric field (perpendicular to the magnetic field in weak magnetic field region) accelerates the particles on average. Finite average velocity in the direction of electric field gives rise to an effective resistivity even in a collisionless regime such as solar corona and the magnetotail. Starting from initial velocities that are chosen randomly from a uniform distribution, the evolution of these distributions tends to a Maxwellian by the end of the simulation that is somewhat analogous to collisions in a Lorentz gas model. The effective resistivity due to such collisions is estimated. Ohmic heating is found to occur as a result of such an effective resistivity. Such collisions due to collective particle effects are essentially a different mechanism from classical collision notion. These experiments are done for two types of ions found in the plasma sheet prior to substorm onset, viz., protons and oxygen ions. Observational evidence of oxygen ions in the central plasma sheet, which flow out along open field lines from the ionosphere, were also simulated in the same manner. Oxygen ions have been found to

  3. Mexican-American Adolescents’ Gender-Typed Characteristics: The Role of Sibling and Friend Characteristics

    PubMed Central

    Wheeler, Lorey A.; Updegraff, Kimberly A.; Schaefer, David R.

    2016-01-01

    This study examined the role of sibling and friend characteristics in Mexican-American youth’s gender-typed characteristics (i.e., attitudes, interests, and leisure activities) in early versus middle adolescence using a sibling design. Mexican-American 7th graders (M = 12.51 years; SD = .58) and their older siblings (M = 15.48 years; SD = 1.57) from 246 families participated in home interviews and a series of seven nightly phone calls. Results revealed that younger/early adolescent siblings reported more traditional gender role attitudes than their older/middle adolescent siblings and older brothers were more traditional in their attitudes than older sisters. When comparing siblings’ gender-typed interests and leisure activities, boys reported more masculine orientations than girls and girls reported more feminine orientations than boys. Older brothers’ gender-typed characteristics were associated with the amount of time spent with and gender characteristics of their friendship group, but for younger brothers, sibling characteristics were associated with their gender-typed characteristics. In contrast, both sibling and friendship characteristics were significantly associated with older and younger sisters’ gender-typed characteristics. The discussion addressed the different correlates of older and younger sisters’ and brothers’ gender-typed characteristics. PMID:25539774

  4. Mexican-American Adolescents' Gender-Typed Characteristics: The Role of Sibling and Friend Characteristics.

    PubMed

    Perez-Brena, Norma J; Wheeler, Lorey A; Updegraff, Kimberly A; Schaefer, David R

    2015-07-01

    This study examined the role of sibling and friend characteristics in Mexican-American youth's gender-typed characteristics (i.e., attitudes, interests, and leisure activities) in early versus middle adolescence using a sibling design. Mexican-American 7th graders (M = 12.51 years; SD = .58) and their older siblings (M = 15.48 years; SD = 1.57) from 246 families participated in home interviews and a series of seven nightly phone calls. Results revealed that younger/early adolescent siblings reported more traditional gender role attitudes than their older/middle adolescent siblings and older brothers were more traditional in their attitudes than older sisters. When comparing siblings' gender-typed interests and leisure activities, boys reported more masculine orientations than girls and girls reported more feminine orientations than boys. Older brothers' gender-typed characteristics were associated with the amount of time spent with and gender characteristics of their friendship group, but for younger brothers, sibling characteristics were associated with their gender-typed characteristics. In contrast, both sibling and friendship characteristics were significantly associated with older and younger sisters' gender-typed characteristics. The discussion addressed the different correlates of older and younger sisters' and brothers' gender-typed characteristics. PMID:25539774

  5. Biogeochemical characteristics of sedimenting particles in Dona Paula Bay, India

    NASA Astrophysics Data System (ADS)

    D'souza, Fraddry; Garg, Anita; Bhosle, Narayan B.

    2003-10-01

    Sedimenting particles were collected at weekly intervals from October to May during 1995-1997 at a station in the coastal waters of Dona Paula Bay on the west coast of India. Sedimenting particles were analysed for concentration and composition of total sedimented particulate matter (TPM), biogenic silica (BSi) and total neutral carbohydrates (TCHO). TPM, BSi and TCHO fluxes showed seasonal and annual variations. Fluxes of BSi showed significant correlations with the fluxes of TCHO and fucose indicating that at the study site diatoms were associated with the production of carbohydrates. However, a high content of arabinose plus xylose (˜56% of TCHO without glucose) in some samples and their negative correlations with fucose may suggest terrestrial inputs. Sedimenting particles depleted in glucose content were enriched in rhamnose, fucose, xylose, mannose and galactose. A principal component analysis based on log-normalized wt% of monosaccharides established three factors that contributed 78% of total variance. The first factor was mostly controlled by the abundance of arabinose and xylose while the second and third factors were dependent on fucose, galactose, mannose and rhamnose. Carbohydrate composition data suggest that the nature and sources of organic matter at the study site varied over the period of study.

  6. Physical and chemical characteristics of interplanetary dust particles. Measurements by the micrometeoroid experiment on board HELIOS

    NASA Astrophysics Data System (ADS)

    Gruen, E.

    1981-08-01

    The micrometeoroid experiment onboard Helios allowed the measurement of physical and chemical characteristics of interplanetary dust particles between 0.3AU and 1AU solar distance. During the first 10 orbits of Helios 1,235 impacts of micrometeoroids were detected. Eighty-three particles were registered by the ecliptic sensor and 152 by the south sensor. Most of the particles detected by the ecliptic sensor impacted the sensor from the apex direction. The particles observed by the south impacted the sensor from all directions with a slightly enhanced flux from solar direction. The average of impact speed of particles was 15 km/s. From 1AU to 0.3AU, the observed particle flux increased by a factor 5 to 10. The orbits of the registered particles are highly eccentric, e or approximately 0.6, and some are hyperbolic. The mass spectra measured upon impact allow the classification of the chondritic and iron rich particles.

  7. Characteristics of defective phage particles of Pectobacterium carotovorum ZM1.

    PubMed

    Tovkach, F I; Ivanytsia, T V; Kushkina, A I

    2012-01-01

    It is shown for the first time that the expression products of defective prophages are typical of defective lysogenic systems of phytopathogenic Pectobacterium carotovorum. It is established that virus-like particles (LP) such as phage capsids are packing bacterial DNA which size is determined by pulse field gel electrophoresis separation. Based on data about capsid structures which are formed by the virulent mutant ZF40/421, there is made a suggestion about the forming mechanism of defective virions of P carotovorum. PMID:22545442

  8. Characteristics of alumina particles in dispersion-strengthened copper alloys

    NASA Astrophysics Data System (ADS)

    Zhang, Xue-hui; Li, Xiao-xian

    2014-11-01

    Two types of alumina dispersion-strengthened copper (ADSC) alloys were fabricated by a novel in-situ reactive synthesis (IRS) and a traditional internal oxidation (IO) process. The features of alumina dispersoids in these ADSC alloys were investigated by X-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy. It is found that nano-sized γ-Al2O3 particles of approximately 10 nm in diameter are homogeneously distributed in the IRS-ADSC composites. Meanwhile, larger-sized, mixed crystal structure alumina with rod-shaped morphology is embedded in the IO-ADSC alloy. The IRS-ADSC composites can obtain better mechanical and physical properties than the IO-ADSC composites; the tensile strength of the IRS-ADSC alloy can reach 570 MPa at room temperature, its electrical conductivity is 85% IACS, and the Rockwell hardness can reach 86 HRB.

  9. Gas-borne particles with tunable and highly controlled characteristics for nanotoxicology studies

    PubMed Central

    Svensson, Christian R.; Pagels, Joakim; Meuller, Bengt O.; Deppert, Knut; Rissler, Jenny

    2012-01-01

    For nanotoxicology investigations of air-borne particles to provide relevant results it is ever so important that the particle exposure of, for example cells, closely resembles the “real” exposure situation, that the dosimetry is well defined, and that the characteristics of the deposited nanoparticles are known in detail. By synthesizing the particles in the gas-phase and directly depositing them on lung cells the particle deposition conditions in the lung is closely mimicked. In this work we present a setup for generation of gas-borne nanoparticles of a variety of different materials with highly controlled and tunable particle characteristics, and demonstrate the method by generation of gold particles. Particle size, number concentration and mass of individual particles of the population are measured on-line by means of differential mobility analyzers (DMA) and an aerosol particle mass analyzer (APM), whereas primary particle size and internal structure are investigated by transmission electron microscopy. A method for estimating the surface area dose from the DMA-APM measurements is applied and we further demonstrate that for the setup used, a deposition time of around 1 h is needed for deposition onto cells in an air–liquid interface chamber, using electrostatic deposition, to reach a toxicological relevant surface area dose. PMID:22630037

  10. Characteristics of final particles in multiple Compton backscattering process

    NASA Astrophysics Data System (ADS)

    Potylitsyn, A.; Kol‘chuzhkin, A.

    2013-08-01

    An electron passing through a counter propagating intense laser beam can interact with a few laser photons with emission of a hard photon in each collision event. In contrast with the well-known nonlinear Compton backscattering process the above mentioned process may be named as multiple Compton backscattering process (MCBS). In this paper we have investigated the evolution of the electron energy distribution during MCBS process using Monte-Carlo (M-C) simulation. The main characteristics of such a distribution as mean energy and variance obtained by M-C technique were compared with analytical solutions of kinetic equations. We found the kinematic region where the analytical solutions are applicable with a good accuracy. A photon spectrum, even for the case when each electron emits one photon (in average) differs significantly from that described by the Klein-Nishina formula.

  11. Self-refreshing characteristics of an airborne particle sensor using a bridged paddle oscillator

    NASA Astrophysics Data System (ADS)

    Choi, Eunsuk; Lee, Seung-Beck; Park, Bonghyun; Sul, Onejae

    2016-05-01

    We report on the self-refreshing characteristics of a micromachined airborne particle sensor. The sensor consists of a bridge-type beam having an oscillating paddle-type particle collector at its center. When a positive potential is applied to the paddle, the sensor is able to attract and collect negatively charged airborne particles while oscillating close to its resonant frequency and thereby measure their density from the change in the oscillating phase at ˜10 pg resolution. When the applied potential is removed, the collected particles are detached from the sensor due to momentum transfer from the oscillating paddle, thus demonstrating a self-refreshing capability.

  12. Sources and characteristics of fine particles over the Yellow Sea and Bohai Sea using online single particle aerosol mass spectrometer.

    PubMed

    Fu, Huaiyu; Zheng, Mei; Yan, Caiqing; Li, Xiaoying; Gao, Huiwang; Yao, Xiaohong; Guo, Zhigang; Zhang, Yuanhang

    2015-03-01

    Marine aerosols over the East China Seas are heavily polluted by continental sources. During the Chinese Comprehensive Ocean Experiment in November 2012, size and mass spectra of individual atmospheric particles in the size range from 0.2 to 2.0 μm were measured on board by a single particle aerosol mass spectrometer (SPAMS). The average hourly particle number (PN) was around 4560±3240 in the South Yellow Sea (SYS), 2900±3970 in the North Yellow Sea (NYS), and 1700±2220 in the Bohai Sea (BS). PN in NYS and BS varied greatly over 3 orders of magnitude, while that in SYS varied slightly. The size distributions were fitted with two log-normal modes. Accumulation mode dominated in NYS and BS, especially during episodic periods. Coarse mode particles played an important role in SYS. Particles were classified using an adaptive resonance theory based neural network algorithm (ART-2a). Six particle types were identified with secondary-containing, aged sea-salt, soot-like, biomass burning, fresh sea-salt, and lead-containing particles accounting for 32%, 21%, 18%, 16%, 4%, and 3% of total PN, respectively. Aerosols in BS were relatively enriched in particles from anthropogenic sources compared to SYS, probably due to emissions from more developed upwind regions and indicating stronger influence of continental outflow on marine environment. Variation of source types depended mainly on origins of transported air masses. This study examined rapid changes in PN, size distribution and source types of fine particles in marine atmospheres. It also demonstrated the effectiveness of high-time-resolution source apportionment by ART-2a. PMID:25766014

  13. Vehicle and driving characteristics that influence in-cabin particle number concentrations.

    PubMed

    Hudda, Neelakshi; Kostenidou, Evangelia; Sioutas, Constantinos; Delfino, Ralph J; Fruin, Scott A

    2011-10-15

    In-transit microenvironments experience elevated levels of vehicle-related pollutants such as ultrafine particles. However, in-vehicle particle number concentrations are frequently lower than on-road concentrations due to particle losses inside vehicles. Particle concentration reduction occurs due to a complicated interplay between a vehicle's air-exchange rate (AER), which determines particle influx rate, and particle losses due to surfaces and the in-cabin air filter. Accurate determination of inside-to-outside particle concentration ratios is best made under realistic aerodynamic and AER conditions because these ratios and AER are determined by vehicle speed and ventilation preference, in addition to vehicle characteristics such as age. In this study, 6 vehicles were tested at 76 combinations of driving speeds, ventilation conditions (i.e., outside air or recirculation), and fan settings. Under recirculation conditions, particle number attenuation (number reduction for 10-1000 nm particles) averaged 0.83 ± 0.13 and was strongly negatively correlated with increasing AER, which in turn depended on speed and the age of the vehicle. Under outside air conditions, attenuation averaged 0.33 ± 0.10 and primarily decreased at higher fan settings that increased AER. In general, in-cabin particle number reductions did not vary strongly with particle size, and cabin filters exhibited low removal efficiencies. PMID:21928803

  14. Effect of flow characteristics on ultrafine particle emissions from range hoods.

    PubMed

    Tseng, Li-Ching; Chen, Chih-Chieh

    2013-08-01

    In order to understand the physical mechanisms of the production of nanometer-sized particulate generated from cooking oils, the ventilation of kitchen hoods was studied by determining the particle concentration, particle size distribution, particle dimensions, and hood's flow characteristics under several cooking scenarios. This research varied the temperature of the frying operation on one cooking operation, with three kinds of commercial cooking oils including soybean oil, olive oil, and sunflower oil. The variations of particle concentration and size distributions with the elevated cooking oil temperatures were presented. The particle concentration increases as a function of temperature. For oil temperatures ranging between 180°C and 210°C, a 5°C increase in temperature increased the number concentration of ultrafine particles by 20-50%. The maximum concentration of ultrafine particles was found to be approximately 6 × 10(6) particles per cm(3) at 260°C. Flow visualization techniques and particle distribution measurement were performed for two types of hood designs, a wall-mounted range hood and an island hood, at a suction flow rate of 15 m(3) min(-1). The flow visualization results showed that different configurations of kitchen hoods induce different aerodynamic characteristics. By comparing the results of flow visualizations and nanoparticle measurements, it was found that the areas with large-scale turbulent vortices are more prone to dispersion of ultrafine particle leakage because of the complex interaction between the shear layers and the suction movement that results from turbulent dispersion. We conclude that the evolution of ultrafine particle concentration fluctuations is strongly affected by the location of the hood, which can alter the aerodynamic features. We suggest that there is a correlation between flow characteristics and amount of contaminant leakage. This provides a comprehensive strategy to evaluate the effectiveness of kitchen hoods

  15. The ozone hole - The role of polar stratospheric cloud particles

    NASA Technical Reports Server (NTRS)

    Hamill, Patrick; Turco, R. P.

    1988-01-01

    The role of polar stratospheric clouds in the formation of the Antarctic ozone hole is considered. Several researchers have suggested that the decrease in ozone over Antarctica is related to the polar stratospheric clouds (PSCs) which had been observed in the antarctic winter stratosphere. Some of the pertinent characteristics of polar stratospheric clouds are discussed, and it is shown how these clouds may participate in the ozone destruction process. The satellite data for PSCs is analyzed, and statistical information regarding the number and maximum extinctions of these clouds is presented. Evidence that the polar stratospheric clouds are composed of frozen nitric acid is considered. It is suggested that the evaporation of the clouds, in late August and September, will release HOCl and HNO3 to the environment. This could be followed by the photodissociation of HOCl to OH and Cl, which would very effectively destroy ozone. However, the ozone destruction mechanism could be halted when enough of the evaporated nitric acid is photolized.

  16. Decoupling the Role of Inertia and Gravity on Particle Dispersion

    NASA Technical Reports Server (NTRS)

    Rogers, Chris; Squires, Kyle

    1996-01-01

    Turbulent gas flows laden with small, dense particles are encountered in a wide number of important applications in both industrial settings and aerodynamics applications. Particle interactions with the underlying turbulent flow are exceedingly complex and, consequently, difficult to accurately model. The difficulty arises primarily due to the fact that response of a particle to the local environment is dictated by turbulence properties in the reference frame moving with the particle (particle-Lagrangian). The particle-Lagrangian reference frame is in turn dependent upon the particle relaxation time (time constant) as well as gravitational drift. The combination of inertial and gravitational effects in this frame complicates our ability to accurately predict particle-laden flows since measurements in the particle-Lagrangian reference frame are difficult to obtain. Therefore, in this work we will examine separately the effects of inertia and gravitational drift on particle dispersion through a combination of physical and numerical experiments. In this study, particle-Lagrangian measurements will be obtained in physical experiments using stereo image velocimetry. Gravitational drift will be varied in the variable-g environments of the NASA DC-9 and in the zero-g environment at the drop tower at NASA-Lewis. Direct numerical simulations will be used to corroborate the measurements from the variable-g experiments. We expect that this work will generate new insight into the underlying physics of particle dispersion and will, in turn, lead to more accurate models of particle transport in turbulent flows.

  17. Optical characteristics of particles produced using electroerosion dispersion of titanium in hydrogen peroxide

    NASA Astrophysics Data System (ADS)

    Pyachin, S. A.; Burkov, A. A.; Makarevich, K. S.; Zaitsev, A. V.; Karpovich, N. F.; Ermakov, M. A.

    2016-07-01

    Titanium oxide particles are produced using electric-discharge dispersion of titanium in aqueous solution of hydrogen peroxide. Electron vacuum microscopy, X-ray diffraction, and diffuse reflection spectroscopy are used to study the morphology, composition, and optical characteristics of the erosion particles. It has been demonstrated that the particles consist of titanium and titanium oxides with different valences. The edge of the optical absorption is located in the UV spectral range. The band gap is 3.35 eV for indirect transitions and 3.87 eV for direct allowed transitions. The band gap decreases due to the relatively long heating in air at a temperature of 480-550°C, so that powder oxide compositions can be obtained, the optical characteristics of which are similar to optical characteristics of anatase. The erosion products are completely oxidized to rutile after annealing in air at a temperature of 1000°C.

  18. Laboratory Studies of Optical Characteristics and Condensation Processes of Cosmic Dust Particles

    NASA Technical Reports Server (NTRS)

    Spann, J. F., Jr.; Abbas, M. M.; Venturini, C. C.

    2000-01-01

    Information about the optical characteristics and physical processes involving cosmic dust particles is vital for interpretation of astronomical observations and an understanding of the formation and processing of dust in the evolutionary cycle of matter in the interstellar medium. Cosmic dust particles are formed in a variety of astrophysical environments such as in cool stellar outflows and circumstellar envelopes. Definitive knowledge of the nature, composition, and physical processes of cosmic dust grains, however, can only be inferred from astronomical observations through laboratory experiments on the analogs of hypothesized dust particles and with modeling calculations. Laboratory investigations of the nature, composition, and optical characteristics of cosmic dust particles are being, carried out at many institutions with a variety of experimental techniques. Despite a wealth of available data, however, many basic issues remain unresolved. An experimental facility based on suspension of dust particles in electrodynamic balance in a pressure/temperature controlled environment in a cavity has been operational at the NASA Marshall Space Flight Center, and is currently being employed for studies of dust particle charging mechanisms using electron beams and with UV radiation. In this paper, we discuss two general classes of experiments under planning stages that may be simultaneously carried out on this facility for cosmic dust investigations (i) Infrared optical characteristics (extinction coefficients and scattering phase functions) of the analogs of hypothesized of cosmic dust particles, such as natural and synthetic amorphous silicates with varying compositions, amorphous carbon grains, polycyclic aromatic hydrocarbons (PAHs), and icy core-mantle particles etc. The initial spectral range under consideration is 1-25 micrometers, to be extended to the far infrared region in the future (ii) Condensation of volatile gases on nucleus dust particles to be

  19. Emissions and Characteristics of Ice Nucleating Particles Associated with Laboratory Generated Nascent Sea Spray Aerosol

    NASA Astrophysics Data System (ADS)

    McCluskey, C. S.; Hill, T. C. J.; Beall, C.; Sultana, C. M.; Moore, K.; Cornwell, G.; Lee, C.; Al-Mashat, H.; Laskina, O.; Trueblood, J.; Grassian, V. H.; Prather, K. A.; Kreidenweis, S. M.; DeMott, P. J.

    2015-12-01

    Accurate emission rates and activity spectra of atmospheric ice nucleating particles (INPs) are required for proper representation of aerosol-cloud interactions in atmospheric modeling studies. However, few investigations have quantified or characterized oceanic INP emissions. In conjunction with the Center for Aerosol Impacts on the Climate and the Environment, we have directly measured changes in INP emissions and properties of INPs from nascent sea spray aerosol (SSA) through the evolution of phytoplankton blooms. Multiple offline and online instruments were used to monitor aerosol chemistry and size, and bulk water characteristics during two phytoplankton bloom experiments. Two methods were utilized to monitor the number concentrations of INPs from 0 to -34 °C: The online CSU continuous flow diffusion chamber (CFDC) and collections processed offline using the CSU ice spectrometer. Single particle analyses were performed on ice crystal residuals downstream of the CFDC, presumed to be INPs, via scanning transmission electron microscopy (STEM) and Raman microspectroscopy. Preliminary results indicate that laboratory-generated nascent SSA corresponds to number concentrations of INPs that are generally consistent with open ocean regions, based on current knowledge. STEM analyses revealed that the sizes of ice crystal residuals that were associated with nascent SSA ranged from 0.3 to 2.5 μm. Raman microspectroscopy analysis of 1 μm sized residuals found a variety of INP identities, including long chain organics, diatom fragments and polysaccharides. Our data suggest that biological processes play a significant role in ocean INP emissions by generating the species and compounds that were identified during these studies.

  20. Particle and field characteristics of the high-latitude plasma sheet boundary layer

    NASA Technical Reports Server (NTRS)

    Parks, G. K.; Mccarthy, M.; Fitzenreiter, R. J.; Ogilvie, K. W.; Etcheto, J.; Anderson, K. A.; Lin, R. P.; Anderson, R. R.; Eastman, T. E.; Frank, L. A.

    1984-01-01

    Particle and field data obtained by eight ISEE spacecraft experiments are used to define more precisely the characteristics of the high-latitude boundary region of the plasma sheet. A region immediately adjacent to the high-latitude plasma sheet boundary has particle and field characteristics distinctly different from those observed in the lobe and deeper in the central plasma sheet. Electrons over a broad energy interval are 'field-aligned' and bidirectional, whereas in the plasma sheet the distributions are more isotropic. The region supports intense ion flows, large-amplitude electric fields, and enhanced broad-band electrostatic noise.

  1. The effect of precipitation conditions and aging upon characteristics of particles precipitated from aqueous solutions

    SciTech Connect

    Rard, J.A.

    1989-10-01

    Precipitation of a dissolved species from aqueous solutions is one of the techniques used to grow particles with certain size or composition characteristics. Various factors affecting the particle properties for sparingly soluble substances are briefly discussed here, including homogeneous versus heterogeneous nucleation, the effect of relative supersaturation on the number of nuclei and their relative size, particle growth by way of Ostwald Ripening, the Ostwald Step Rule and nucleation of metastable phases, diffusion-controlled versus surface reaction-controlled growth, incorporation of dopants into the precipitate, and dendritic growth. 13 refs.

  2. Lower Permittivity Characteristic of Mesoporous-Alumina/Epoxy Composite due to Particle Porosity

    NASA Astrophysics Data System (ADS)

    Kurimoto, Muneaki; Murakami, Yoshinobu; Nagao, Masayuki

    Introduction of metal oxide nanoparticles to polymer composite material is known to have unique dielectric behavior and significant advantage in the electrical insulation performance of electrical power apparatus. This paper presents an attempt to derive the dielectric characteristics of polymer composite filled with the metal oxide particle which has mesoporous structure. Experiments were carried out in the epoxy composites filled with alumina microparticles which have the mesoporous structure (mesoporous-alumina/epoxy composites) with different particle content. Based on the measurement of the specific gravity of mesoporous-alumina/epoxy composites, the porosity of mesoporous-alumina particle in the epoxy matrix was found to be higher than that of nonporous-alumina particle. Furthermore, we evaluated relative permittivity of mesoporous-alumina/epoxy composites by measuring the capacitance of its specimens. As the results, we verified that the permittivity of mesoporous-alumina/epoxy composites was lower than that of nonporous-alumina/epoxy composites due to the particle porosity.

  3. Coalbed methane adsorption and desorption characteristics related to coal particle size

    NASA Astrophysics Data System (ADS)

    Yan-Yan, Feng; Wen, Yang; Wei, Chu

    2016-06-01

    Effects of particle size on CH4 and CO2 adsorption and desorption characteristics of coals are investigated at 308 K and pressures up to 5.0 MPa. The gas adsorption and desorption isotherms of coals with particle sizes ranging from 250 μm to 840 μm are measured via the volumetric method, and the Langmuir model is used to analyse the experimental results. Coal particle size is found to have an obvious effect on the coal pore structure. With the decrease of coal particle size in the process of grinding, the pore accessibility of the coal, including the specific surface area and pore volume, increases. Hence, coal with smaller particle size has higher specific surface area and higher pore volume. The ability of adsorption was highly related to the pore structure of coal, and coal particle size has a significant influence on coal adsorption/desorption characteristics, including adsorption capacity and desorption hysteresis for CH4 and CO2, i.e., coal with a smaller particle size achieves higher adsorption capacity, while the sample with a larger particle size has lower adsorption capacity. Further, coal with larger particle size is also found to have relatively large desorption hysteresis. In addition, dynamic adsorption performances of the samples are carried out at 298 K and at pressures of 0.1 MPa and 0.5 MPa, respectively, and the results indicate that with the increase of particle size, the difference between CO2 and CH4 adsorption capacities of the samples decreases. Project supported by the National Basic Research Program of China (Grant No. 2011CB201202).

  4. Flow characteristics in free impinging jet reactor by particle image velocimetry (PIV) investigation

    NASA Astrophysics Data System (ADS)

    Zhang, Jun; Liu, Youzhi; Qi, Guisheng; Jiao, Weizhou; Yuan, Zhiguo

    2016-08-01

    The flow characteristics in free impinging jet reactors (FIJRs) were investigated using particle image velocimetry (PIV). The effects of the Reynolds number (Re) and the ratio of jet distance to jet diameter (w/d) on flow behavior were discussed for equal volumetric flow rates of the two jets. The impingement plane, instantaneous velocity, mean velocity, and turbulent kinetic energy (TKE) distribution of FIJRs are measured from captured images using the PIV technique. As Re increases, the average diameter of the impingement plane linearly increases. The instability of the liquid is closely related to the jet velocity or the Re. However, the stagnation point is insensitive to the variation of the Re. The droplets break up from the turbulent liquid in the ‘wall-free’ environment of FIJRs, so that the liquid back-flow found in confined impinging jet reactors (CIJRs) is not observed. Increasing the Re from 1800–4100 or decreasing the w/d from 20–6 plays a similar role in increasing the TKE values and intensifying turbulence, which promotes the momentum transfer and mixing efficiency in FIJRs.

  5. Particle model analyses of N2O dilution with He on electrical characteristics of radio-frequency discharges

    NASA Astrophysics Data System (ADS)

    Younis, G.; Yousfi, M.; Despax, B.

    2009-05-01

    The electrical characteristics (voltage, electric field, charged particle densities, dissipated power, particle energy, etc.) are analyzed in the case of low pressure (0.5 and 1 Torr) radio-frequency (rf) discharges in nitrous oxide (N2O)/Helium (He) mixtures. An optimized and validated particle model has been used for these analyses in the case of gradual dilutions of N2O with He buffer gas. A specific care is carried on the power density evolution and variation which show a complex behavior as a function of He proportion (up to 85%). These analyses are based on a microscopic approach enabling one to show the contribution of the different inelastic processes mainly between electrons and respectively N2O and He gases. This approach enables also one to show the discharge region (the positive column or the plasma region) where the power is preferentially dissipated. The power density variation is found to be mainly proportional to the electron density variation. The latter is dependent on the different processes occurring between the charged particles [i.e., electrons, negative ions (O- and NO-), and positive ions (N2O+ and He+)] and the neutral gas mixture (N2O and He). Furthermore, the particle model shows the role of the electron-He collisions on the variation in the electron energy and distribution. This allows more particularly explaining the effects of N2O dilution with He on the dissipated power variation in terms of creation and loss of electrons through collision processes.

  6. Characteristics of Fine Particles in an Urban Atmosphere-Relationships with Meteorological Parameters and Trace Gases.

    PubMed

    Zhang, Tianhao; Zhu, Zhongmin; Gong, Wei; Xiang, Hao; Fang, Ruimin

    2016-01-01

    Atmospheric fine particles (diameter < 1 μm) attract a growing global health concern and have increased in urban areas that have a strong link to nucleation, traffic emissions, and industrial emissions. To reveal the characteristics of fine particles in an industrial city of a developing country, two-year measurements of particle number size distribution (15.1 nm-661 nm), meteorological parameters, and trace gases were made in the city of Wuhan located in central China from June 2012 to May 2014. The annual average particle number concentrations in the nucleation mode (15.1 nm-30 nm), Aitken mode (30 nm-100 nm), and accumulation mode (100 nm-661 nm) reached 4923 cm(-3), 12193 cm(-3) and 4801 cm(-3), respectively. Based on Pearson coefficients between particle number concentrations and meteorological parameters, precipitation and temperature both had significantly negative relationships with particle number concentrations, whereas atmospheric pressure was positively correlated with the particle number concentrations. The diurnal variation of number concentration in nucleation mode particles correlated closely with photochemical processes in all four seasons. At the same time, distinct growth of particles from nucleation mode to Aitken mode was only found in spring, summer, and autumn. The two peaks of Aitken mode and accumulation mode particles in morning and evening corresponded obviously to traffic exhaust emissions peaks. A phenomenon of "repeated, short-lived" nucleation events have been created to explain the durability of high particle concentrations, which was instigated by exogenous pollutants, during winter in a case analysis of Wuhan. Measurements of hourly trace gases and segmental meteorological factors were applied as proxies for complex chemical reactions and dense industrial activities. The results of this study offer reasonable estimations of particle impacts and provide references for emissions control strategies in industrial cities of developing

  7. Characteristics of Fine Particles in an Urban Atmosphere—Relationships with Meteorological Parameters and Trace Gases

    PubMed Central

    Zhang, Tianhao; Zhu, Zhongmin; Gong, Wei; Xiang, Hao; Fang, Ruimin

    2016-01-01

    Atmospheric fine particles (diameter < 1 μm) attract a growing global health concern and have increased in urban areas that have a strong link to nucleation, traffic emissions, and industrial emissions. To reveal the characteristics of fine particles in an industrial city of a developing country, two-year measurements of particle number size distribution (15.1 nm–661 nm), meteorological parameters, and trace gases were made in the city of Wuhan located in central China from June 2012 to May 2014. The annual average particle number concentrations in the nucleation mode (15.1 nm–30 nm), Aitken mode (30 nm–100 nm), and accumulation mode (100 nm–661 nm) reached 4923 cm−3, 12193 cm−3 and 4801 cm−3, respectively. Based on Pearson coefficients between particle number concentrations and meteorological parameters, precipitation and temperature both had significantly negative relationships with particle number concentrations, whereas atmospheric pressure was positively correlated with the particle number concentrations. The diurnal variation of number concentration in nucleation mode particles correlated closely with photochemical processes in all four seasons. At the same time, distinct growth of particles from nucleation mode to Aitken mode was only found in spring, summer, and autumn. The two peaks of Aitken mode and accumulation mode particles in morning and evening corresponded obviously to traffic exhaust emissions peaks. A phenomenon of “repeated, short-lived” nucleation events have been created to explain the durability of high particle concentrations, which was instigated by exogenous pollutants, during winter in a case analysis of Wuhan. Measurements of hourly trace gases and segmental meteorological factors were applied as proxies for complex chemical reactions and dense industrial activities. The results of this study offer reasonable estimations of particle impacts and provide references for emissions control strategies in industrial cities of

  8. Role of Surface Characteristics in Urban Meteorology and Air Quality

    NASA Astrophysics Data System (ADS)

    Sailor, David Jean

    Urbanization results in a landscape with significantly modified surface characteristics. The lower values of reflectivity to solar radiation, surface moisture availability, and vegetative cover, along with the higher values of anthropogenic heat release and surface roughness combine to result in higher air temperatures in urban areas relative to their rural counterparts. Through their role in the surface energy balance and surface exchange processes, these surface characteristics are capable of modifying the local meteorology. The impacts on wind speeds, air temperatures, and mixing heights are of particular importance, as they have significant implications in terms of urban energy use and air quality. This research presents several major improvements to the meteorological modeling methodology for highly heterogeneous terrain. A land-use data base is implemented to provide accurate specification of surface characteristic variability in simulations of the Los Angeles Basin. Several vegetation parameterizations are developed and implemented, and a method for including anthropogenic heat release into the model physics is presented. These modeling advancements are then used in a series of three-dimensional simulations which were developed to investigate the potential meteorological impact of several mitigation strategies. Results indicate that application of moderate tree-planting and urban-lightening programs in Los Angeles may produce summertime air temperature reductions on the order of 4^circ C with a concomitant reduction in air pollution. The analysis also reveals several mechanisms whereby the application of these mitigation strategies may potentially increase pollutant concentrations. The pollution and energy use consequences are discussed in detail.

  9. Role of surface characteristics in urban meteorology and air quality

    SciTech Connect

    Sailor, D.J.

    1993-08-01

    Urbanization results in a landscape with significantly modified surface characteristics. The lower values of reflectivity to solar radiation, surface moisture availability, and vegetative cover, along with the higher values of anthropogenic heat release and surface roughness combine to result higher air temperatures in urban areas relative to their rural counterparts. Through their role in the surface energy balance and surface exchange processes, these surface characteristics are capable of modifying the local meteorology. The impacts on wind speeds, air temperatures, and mixing heights are of particular importance, as they have significant implications in terms of urban energy use and air quality. This research presents several major improvements to the meteorological modeling methodology for highly heterogeneous terrain. A land-use data-base is implemented to provide accurate specification of surface characteristic variability in simulations of the Los Angeles Basin. Several vegetation parameterizations are developed and implemented, and a method for including anthropogenic heat release into the model physics is presented. These modeling advancements are then used in a series of three-dimensional simulations which were developed to investigate the potential meteorological impact of several mitigation strategies. Results indicate that application of moderate tree-planting and urban-lightening programs in Los Angeles may produce summertime air temperature reductions on the order of 4{degree}C with a concomitant reduction in air pollution. The analysis also reveals several mechanisms whereby the application of these mitigation strategies may potentially increase pollutant concentrations. The pollution and energy use consequences are discussed in detail.

  10. Combustion characteristics of fuel droplets with addition of nano and micron-sized aluminum particles

    SciTech Connect

    Gan, Yanan; Qiao, Li

    2011-02-15

    The burning characteristics of fuel droplets containing nano and micron-sized aluminum particles were investigated. Particle size, surfactant concentration, and the type of base fluid were varied. In general, nanosuspensions can last much longer than micron suspensions, and ethanol-based fuels were found to achieve much better suspension than n-decane-based fuels. Five distinctive stages (preheating and ignition, classical combustion, microexplosion, surfactant flame, and aluminum droplet flame) were identified for an n-decane/nano-Al droplet, while only the first three stages occurred for an n-decane/micron-Al droplet. For the same solid loading rate and surfactant concentration, the disruption and microexplosion behavior of the micron suspension occurred later with much stronger intensity. The intense droplet fragmentation was accompanied by shell rupture, which caused a massive explosion of particles, and most of them were burned during this event. On the contrary, for the nanosuspension, combustion of the large agglomerate at the later stage requires a longer time and is less complete because of formation of an oxide shell on the surface. This difference is mainly due to the different structure and characteristics of particle agglomerates formed during the early stage, which is a spherical, porous, and more-uniformly distributed aggregate for the nanosuspension, but it is a densely packed and impermeable shell for the micron suspension. A theoretical analysis was then conducted to understand the effect of particle size on particle collision mechanism and aggregation rate. The results show that for nanosuspensions, particle collision and aggregation are dominated by the random Brownian motion. For micron suspensions, however, they are dominated by fluid motion such as droplet surface regression, droplet expansion resulting from bubble formation, and internal circulation. And the Brownian motion is the least important. This theoretical analysis explains the

  11. Field-dependent characteristics of magnetorheological fluids containing corroded iron particles

    NASA Astrophysics Data System (ADS)

    Han, Young-Min; Kim, Soomin; Park, Young-Dai; Kang, Je-Won; Choi, Seung-Bok

    2015-11-01

    Magnetorheological (MR) devices in vehicle applications and robotic systems require both consistent control performance and reliable operation. However, corrosion of iron particles in MR fluid may occur during long-time operation. This corrosion behavior can significantly affect the performance and reliability of application devices or systems utilizing MR fluids. This study experimentally investigates the effect of the MR particle corrosion on the performance of MR fluids in terms of the field-dependent yield stress magnitude and shear stress controllability. MR particles are first corroded by two different liquids; water-sodium chloride solution and water-calcium chloride solution. The resulting MR particles are examined by scanning electron microscopy and their molar ratios are analyzed by energy dispersive x-ray analysis. Using the corroded MR particles, MR fluid is synthesized for evaluation of the effects on its characteristics. A rotational viscometer is used to measure the field-dependent shear stress and response time. The measured results are compared between the original MR fluid composed of the non-corroded iron particles and the MR fluid composed of the corroded iron particles. In addition, the effect of the corroded particles in MR fluid on the shear stress controllability is investigated in the time domain.

  12. Formation and characteristics of biomimetic mineralo-organic particles in natural surface water

    PubMed Central

    Wu, Cheng-Yeu; Martel, Jan; Wong, Tsui-Yin; Young, David; Liu, Chien-Chun; Lin, Cheng-Wei; Young, John D.

    2016-01-01

    Recent studies have shown that nanoparticles exist in environmental water but the formation, characteristics and fate of such particles remain incompletely understood. We show here that surface water obtained from various sources (ocean, hot springs, and soil) produces mineralo-organic particles that gradually increase in size and number during incubation. Seawater produces mineralo-organic particles following several cycles of filtration and incubation, indicating that this water possesses high particle-seeding potential. Electron microscopy observations reveal round, bacteria-like mineral particles with diameters of 20 to 800 nm, which may coalesce and aggregate to form mineralized biofilm-like structures. Chemical analysis of the particles shows the presence of a wide range of chemical elements that form mixed mineral phases dominated by calcium and iron sulfates, silicon and aluminum oxides, sodium carbonate, and iron sulfide. Proteomic analysis indicates that the particles bind to proteins of bacterial, plant and animal origins. When observed under dark-field microscopy, mineral particles derived from soil-water show biomimetic morphologies, including large, round structures similar to cells undergoing division. These findings have important implications not only for the recognition of biosignatures and fossils of small microorganisms in the environment but also for the geochemical cycling of elements, ions and organic matter in surface water. PMID:27350595

  13. Formation and characteristics of biomimetic mineralo-organic particles in natural surface water

    NASA Astrophysics Data System (ADS)

    Wu, Cheng-Yeu; Martel, Jan; Wong, Tsui-Yin; Young, David; Liu, Chien-Chun; Lin, Cheng-Wei; Young, John D.

    2016-06-01

    Recent studies have shown that nanoparticles exist in environmental water but the formation, characteristics and fate of such particles remain incompletely understood. We show here that surface water obtained from various sources (ocean, hot springs, and soil) produces mineralo-organic particles that gradually increase in size and number during incubation. Seawater produces mineralo-organic particles following several cycles of filtration and incubation, indicating that this water possesses high particle-seeding potential. Electron microscopy observations reveal round, bacteria-like mineral particles with diameters of 20 to 800 nm, which may coalesce and aggregate to form mineralized biofilm-like structures. Chemical analysis of the particles shows the presence of a wide range of chemical elements that form mixed mineral phases dominated by calcium and iron sulfates, silicon and aluminum oxides, sodium carbonate, and iron sulfide. Proteomic analysis indicates that the particles bind to proteins of bacterial, plant and animal origins. When observed under dark-field microscopy, mineral particles derived from soil-water show biomimetic morphologies, including large, round structures similar to cells undergoing division. These findings have important implications not only for the recognition of biosignatures and fossils of small microorganisms in the environment but also for the geochemical cycling of elements, ions and organic matter in surface water.

  14. Formation and characteristics of biomimetic mineralo-organic particles in natural surface water.

    PubMed

    Wu, Cheng-Yeu; Martel, Jan; Wong, Tsui-Yin; Young, David; Liu, Chien-Chun; Lin, Cheng-Wei; Young, John D

    2016-01-01

    Recent studies have shown that nanoparticles exist in environmental water but the formation, characteristics and fate of such particles remain incompletely understood. We show here that surface water obtained from various sources (ocean, hot springs, and soil) produces mineralo-organic particles that gradually increase in size and number during incubation. Seawater produces mineralo-organic particles following several cycles of filtration and incubation, indicating that this water possesses high particle-seeding potential. Electron microscopy observations reveal round, bacteria-like mineral particles with diameters of 20 to 800 nm, which may coalesce and aggregate to form mineralized biofilm-like structures. Chemical analysis of the particles shows the presence of a wide range of chemical elements that form mixed mineral phases dominated by calcium and iron sulfates, silicon and aluminum oxides, sodium carbonate, and iron sulfide. Proteomic analysis indicates that the particles bind to proteins of bacterial, plant and animal origins. When observed under dark-field microscopy, mineral particles derived from soil-water show biomimetic morphologies, including large, round structures similar to cells undergoing division. These findings have important implications not only for the recognition of biosignatures and fossils of small microorganisms in the environment but also for the geochemical cycling of elements, ions and organic matter in surface water. PMID:27350595

  15. Frictional and heat resistance characteristics of coconut husk particle filled automotive brake pad

    NASA Astrophysics Data System (ADS)

    Bahari, Shahril Anuar; Chik, Mohd Syahrizul; Kassim, Masitah Abu; Som Said, Che Mohamad; Misnon, Mohd Iqbal; Mohamed, Zulkifli; Othman, Eliasidi Abu

    2012-06-01

    The objective of this study was to determine the friction and heat resistance characteristics of automotive brake pad composed with different sizes and percentages of coconut husk particle. The materials used were phenolic resin (phenol formaldehyde) as binder, copper, graphite and brass as friction producer/modifiers, magnesium oxide as abrasive material, steel and barium sulfate as reinforcement while coconut husk particle as filler. To obtain particle, the coconut husk was ground and dried to 3% moisture content. Then the coconut husk particle was screened using 80 mesh (to obtain coarse dust) and 100 mesh (to obtain fine dust). Different percentages of particle, such as 10 and 30% were used in the mixture of brake pad materials. Then the mixture was hot-pressed to produce brake pad. Chase machine was used to determine the friction coefficient in friction resistance testing, while thermogravimetric analyzer (TGA) machine was used to determine the heat decomposition values in heat resistance testing. Results showed that brake pad with 100 mesh and 10% composition of coconut husk particle showed the highest friction coefficient. For heat resistance, brake pad with 100 mesh and 30% composition of coconut husk dust showed the highest decomposition temperature, due to the high percentage of coconut husk particle in the composition, thus increased the thermal stability. As a comparison, brake pad composed with coconut husk particle showed better heat resistance results than commercial brake pad.

  16. In situ real-time measurement of physical characteristics of airborne bacterial particles

    NASA Astrophysics Data System (ADS)

    Jung, Jae Hee; Lee, Jung Eun

    2013-12-01

    Bioaerosols, including aerosolized bacteria, viruses, and fungi, are associated with public health and environmental problems. One promising control method to reduce the harmful effects of bioaerosols is thermal inactivation via a continuous-flow high-temperature short-time (HTST) system. However, variations in bioaerosol physical characteristics - for example, the particle size and shape - during the continuous-flow inactivation process can change the transport properties in the air, which can affect particle deposition in the human respiratory system or the filtration efficiency of ventilation systems. Real-time particle monitoring techniques are a desirable alternative to the time-consuming process of microscopic analysis that is conventionally used in sampling and particle characterization. Here, we report in situ real-time optical scattering measurements of the physical characteristics of airborne bacteria particles following an HTST process in a continuous-flow system. Our results demonstrate that the aerodynamic diameter of bacterial aerosols decreases when exposed to a high-temperature environment, and that the shape of the bacterial cells is significantly altered. These variations in physical characteristics using optical scattering measurements were found to be in agreement with the results of scanning electron microscopy analysis.

  17. Functional Role of Infective Viral Particles on Metal Reduction

    SciTech Connect

    Coates, John D.

    2014-04-01

    A proposed strategy for the remediation of uranium (U) contaminated sites was based on the immobilization of U by reducing the oxidized soluble U, U(VI), to form a reduced insoluble end product, U(IV). Previous studies identified Geobacter sp., including G. sulfurreducens and G. metallireducens, as predominant U(VI)-reducing bacteria under acetate-oxidizing and U(VI)-reducing conditions. Examination of the finished genome sequence annotation of the canonical metal reducing species Geobacter sulfurreducens strain PCA and G. metallireduceans strain GS-15 as well as the draft genome sequence of G. uraniumreducens strain Rf4 identified phage related proteins. In addition, the completed genome for Anaeromyxobacter dehalogenans and the draft genome sequence of Desulfovibrio desulfuricans strain G20, two more model metal-reducing bacteria, also revealed phage related sequences. The presence of these gene sequences indicated that Geobacter spp., Anaeromyxobacter spp., and Desulfovibrio spp. are susceptible to viral infection. Furthermore, viral populations in soils and sedimentary environments in the order of 6.4×10{sup 6}–2.7×10{sup 10} VLP’s cm{sup -3} have been observed. In some cases, viral populations exceed bacterial populations in these environments suggesting that a relationship may exist between viruses and bacteria. Our preliminary screens of samples collected from the ESR FRC indicated that viral like particles were observed in significant numbers. The objective of this study was to investigate the potential functional role viruses play in metal reduction specifically Fe(III) and U(VI) reduction, the environmental parameters affecting viral infection of metal reducing bacteria, and the subsequent effects on U transport.

  18. Study of particle rebound characteristics and material erosion at high temperature

    SciTech Connect

    Tabakoff, W.; Hamed, A.; Eroglu, H.

    1988-12-01

    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.

  19. The role of particles in stabilising foams and emulsions.

    PubMed

    Hunter, Timothy N; Pugh, Robert J; Franks, George V; Jameson, Graeme J

    2008-03-18

    The use of particles as foam and emulsion stabilising species, with or without surfactants, has received great interest in recent years. The majority of work has studied the effects of particles as stabilisers in emulsion systems, but recent successes has widened consideration into foams, where industries such as flotation and food processing have encountered the effects of particle stabilisation for many years. This review seeks to clarify studies into emulsions, highlighting new research in this area, and relate similarities and differences to foam systems. Past research has focused on defining the interaction mechanisms of stability, such as principles of attachment energies, particle-particle forces at the interface and changes to the interfilm, with a view to ascertain conditions giving optimum stability. Studied conditions include effects of particle contact angle, aggregation formations, concentration, size and interactions of other species (i.e. surfactant). Mechanisms can be complex, but overall the principle of particles creating a steric barrier to coalescence, is a straitforward basis of interaction. Much research in emulsions can be applied to foam systems, however evidence would suggest foam systems are under a number of additional constraints, and the stability 'window' for particles is smaller, in terms of size and contact angle ranges. Also, because of increased density differences and interfilm perturbations in foam systems, retardation of drainage is often as important to stability as inhibiting coalescence. PMID:17904510

  20. The role of particle-size soil fractions in the adsorption of heavy metals

    NASA Astrophysics Data System (ADS)

    Mandzhieva, Saglara; Minkina, Tatiana; Pinsky, David; Batukaev, Abdulmalik; Kalinitchenko, Valeriy; Sushkova, Svetlana; Chaplygin, Viktor; Dikaev, Zaurbek; Startsev, Viktor; Bakoev, Serojdin

    2014-05-01

    Ion-exchange adsorption phenomena are important in the immobilization of heavy metals (HMs) by soils. Numerous works are devoted to the study of this problem. However, the interaction features of different particle-size soil fractions and their role in the immobilization of HMs studied insufficiently. Therefore, the assessment of the effect of the particle-size distribution on the adsorption properties of soils is a vital task. The parameters of Cu2+, Pb2+ and Zn2+ adsorption by chernozems of the south of Russia and their particle-size fractions were studied. In the particle-size fractions separated from the soils, the concentrations of Cu2+, Pb2+, and Zn2 decreased with the decreasing particle size. The parameters of the adsorption values of k (the constant of the affinity)and Cmax.(the maximum adsorption of the HMs) characterizing the adsorption of HMs by the southern chernozem and its particle-size fractions formed the following sequence: silt > clay > entire soil. The adsorption capacity of chernozems for Cu2+, Pb2+, and Zn2+ depending on the particle-size distribution decreased in the following sequence: clay loamy ordinary chernozem clay loamy southern chernozem> loamy southern chernozem> loamy sandy southern chernozem. According to the parameters of the adsorption by the different particle-size fractions, the heavy metal cations form a sequence analogous to that obtained for the entire soils: Cu2+ ≥ Pb2+ > Zn2+. The parameters of the heavy metal adsorption by similar particle-size fractions separated from different soils decreased in the following order: clay loamy chernozem> loamy chernozem> loamy sandy chernozem. The analysis of the changes in the parameters of the Cu2+, Pb2+, and Zn2+ adsorption by the studied soils and their particle-size fractions showed that the extensive adsorption characteristic - the maximum adsorption (Cmax.) - is a less sensitive parameter characterizing the adsorption capacity of the soils than the intensive characteristic of

  1. Study of particle rebound characteristics and material erosion at high temperature

    SciTech Connect

    Tabakoff, W.; Hamed, A.; Metwally, A.; Yeuan, J. . Dept. of Aerospace Engineering and Engineering Mechanics)

    1992-04-01

    In this research an investigation was conducted to study the ash particle rebound characteristics and the associated erosion behavior of alloys and coatings which are widely used in gas and steam turbines. A three-component LDV system was used to measure the restitution parameters of 15 micron mean diameter coal ash particles impacting superalloys and coating at different angles. The presented results show the variation of the particle restitution ratios with the impingement angle for the coated and uncoated surfaces. The experimental results were used to develop correlations for the restitution parameters for coated and uncoated superalloys. In addition, a theoretical model based on elastic-plastic theory has been developed to simulate single solid particle impacts on solid targets.

  2. Effect of carbonyl iron particles composition on the physical characteristics of MR grease

    NASA Astrophysics Data System (ADS)

    Mohamad, Norzilawati; Mazlan, Saiful Amri; Ubaidillah

    2016-03-01

    Magnetorheological (MR) grease is an extension of the study of magnetorheological materials. The MR grease can help to reduce the particles sedimentation problem occurred in the MR fluids. Within this study, an effort has been taken to investigate the effect of different weight compositions of carbonyl iron particles on the physical and chemical characteristics of the MR grease under off-state condition (no magnetic field). The MR grease is prepared by mixing carbonyl iron particles having a size range of 1 to 10 µm with commercial NPC Highrex HD-3 grease. Characterizations of MR grease are investigated using Vibrating Sample Magnetometer (VSM), Environmental Scanning Electron Microscopy (ESEM), Differential Scanning Calorimeter (DSC) and rheometer. The dependency of carbonyl iron particles weight towards the magnetic properties of MR grease and other characterizations are investigated.

  3. Decoupling the Role of Particle Inertia and Gravity on Particle Dispersion

    NASA Technical Reports Server (NTRS)

    Squires, Kyle D.

    2002-01-01

    Particle dispersion and the influence that particle momentum exchange has on the properties of a turbulent carrier flow in micro-gravity environments challenge present understanding and predictive schemes. The objective of this effort has been to develop and assess high-fidelity simulation tools for predicting particle transport within micro-gravity environments suspended in turbulent flows. The computational technique is based on Direct Numerical Simulation (DNS) of the incompressible Navier-Stokes equations. The particular focus of the present work is on the class of dilute flows in which particle volume fractions and inter-particle collisions are negligible. Particle motion is assumed to be governed by drag with particle relaxation times ranging from the Kolmogorov scale to the Eulerian timescale of the turbulence and particle mass loadings up to one. The velocity field was made statistically stationary by forcing the low wavenumbers of the flow. The calculations were performed using 96(exp 3) collocation points and the Taylor-scale Reynolds number for the stationary flow was 62. The effect of particles on the turbulence was included in the Navier-Stokes equations using the point-force approximation in which 96(exp 3) particles were used in the calculations. DNS results show that particles increasingly dissipate fluid kinetic energy with increased loading, with the reduction in kinetic energy being relatively independent of the particle relaxation time. Viscous dissipation in the fluid decreases with increased loading and is larger for particles with smaller relaxation times. Fluid energy spectra show that there is a non-uniform distortion of the turbulence with a relative increase in small-scale energy. The non-uniform distortion significantly affects the transport of the dissipation rate, with the production and destruction of dissipation exhibiting completely different behaviors. The spectrum of the fluid-particle energy exchange rate shows that the fluid

  4. The Role of Personality Characteristics in Young Adult Driving

    PubMed Central

    PATIL, SUJATA M.; SHOPE, JEAN THATCHER; RAGHUNATHAN, TRIVELLORE E.; BINGHAM, C. RAYMOND

    2007-01-01

    Background Motor vehicle injury is the major cause of mortality among young adults. Information about the individual characteristics of those who drive dangerously could enhance traffic safety programs. The goal of this research was to examine the association between various personality-related characteristics and risky driving behaviors. Methods Young adults in Michigan, USA (n = 5,362) were surveyed by telephone regarding several personality factors (risk-taking, hostility, aggression, tolerance of deviance, achievement expectations) and driving behaviors (competitive driving, risk-taking driving, high-risk driving, aggressive driving, and drink/driving). Michigan driver records were obtained to examine offenses, serious offenses, driving offense points, crashes and serious crashes in the three pre-interview years. Multivariate regression analyses, adjusting for age, race, and marital status were conducted separately by sex to identify personality factors related to driving. Results For men and women, greater risk-taking propensity, physical/verbal hostility, aggression, and tolerance of deviance were significant predictors of a competitive attitude toward driving, risk-taking driving, high-risk driving, driving aggression, and drink/driving. Greater risk-taking propensity, physical/verbal hostility, aggression, and to a small degree, expectations for achievement predicted higher numbers of offenses, serious offenses, and points. Conclusion Traffic safety policies and programs could be enhanced through recognition of the role personality factors play in driving behavior and the incorporation of this knowledge into the design and implementation of interventions that modify the behaviors associated with them. PMID:17114089

  5. The role of supersymmetry phenomenology in particle physics

    SciTech Connect

    Wells, James D.

    2000-12-14

    Supersymmetry phenomenology is an important component of particle physics today. I provide a definition of supersymmetry phenomenology, outline the scope of its activity, and argue its legitimacy. This essay derives from a presentation given at the 2000 SLAC Summer Institute.

  6. The role of particle collisions in pneumatic transport

    NASA Technical Reports Server (NTRS)

    Mastorakos, E.; Louge, M.; Jenkins, J. T.

    1989-01-01

    A model of dilute gas-solid flow in vertical risers is developed in which the particle phase is treated as a granular material, the balance equations for rapid granular flow are modified to incorporate the drag force from the gas, and boundary conditions, based on collisional exchanges of momentum and energy at the wall, are employed. In this model, it is assumed that the particle fluctuations are determined by inter-particle collisions only and that the turbulence of the gas is unaffected by the presence of the particles. The model is developed in the context of, but not limited to, steady, fully developed flow. A numerical solution of the resulting governing equations provides concentration profiles generally observed in dilute pneumatic flow, velocity profiles in good agreement with the measurements of Tsuji, et al. (1984), and an explanation for the enhancement of turbulence that they observed.

  7. Debris characteristics from a colloidal microjet target containing tin dioxide nano-particles

    NASA Astrophysics Data System (ADS)

    Higashiguchi, Takeshi; Suetake, Sumihiro; Senba, Yusuke; Sato, Yusuke; Hosotani, Akira; Takahashi, Yukari; Kubodera, Shoichi

    2007-03-01

    Characteristics of suprathermal ions and neutral particles from a laser-produced tin plasma by use of a colloidal microjet target containing tin dioxide (SnO II) nanoparticles were investigated. Suprathermal ion emissions were reduced by producing a low-density preplasma. Simultaneously, the maximum conversion efficiency of 1.2% at 13.5 nm with a bandwidth of 2% and a solid angle of 2π sr was observed. Neutral particles, however, were not suppressed under the optimum laser-plasma conditions.

  8. Formation characteristics of aerosol particles from pulverized coal pyrolysis in high-temperature environments

    SciTech Connect

    Wei-Hsin Chen; Shan-Wen Du; Hsi-Hsien Yang; Jheng-Syun Wu

    2008-05-15

    The formation characteristics of aerosol particles from pulverized coal pyrolysis in high temperatures are studied experimentally. By conducting a drop-tube furnace, fuel pyrolysis processes in industrial furnaces are simulated in which three different reaction temperatures of 1000, 1200, and 1400{sup o}C are considered. Experimental observations indicate that when the reaction temperature is 1000{sup o}C, submicron particles are produced, whereas the particle size is dominated by nanoscale for the temperature of 1400{sup o}C. Thermogravimetric analysis of the aerosol particles stemming from the pyrolysis temperature of 1000{sup o}C reveals that the thermal behavior of the aerosol is characterized by a three-stage reaction with increasing heating temperature: (1) a volatile-reaction stage, (2) a weak-reaction stage, and (3) a soot-reaction stage. However, with the pyrolysis temperature of 1400{sup o}C, the volatile- and weak-reaction stages almost merge together and evolve into a chemical-frozen stage. The submicron particles (i.e., 1000{sup o}C) are mainly composed of volatiles, tar, and soot, with the main component of the nanoscale particles (i.e., 1400{sup o}C) being soot. The polycyclic aromatic hydrocarbons (PAHs) contained in the aerosols are also analyzed. It is found that the PAH content in generated aerosols decreases dramatically as the pyrolysis temperature increases. 31 refs., 9 figs., 1 tab.

  9. The role of cometary particle coalescence in chemical evolution

    NASA Technical Reports Server (NTRS)

    Oberbeck, V. R.; Mckay, C. P.; Carle, G. C.; Valentin, J. R.; Scattergood, T. W.

    1989-01-01

    Important prebiotic organic compounds might have been transported to earth in dust or produced in vapor clouds resulting from atmospheric explosions or impacts of comets. These compounds coalesced in the upper atmosphere with particles ejected from craters formed by impacts of large objects. Coalescence during exposure to UV radiation concentrated organic monomers and enhanced formation of oligomers. Continuing coalescence added material to the growing particles and shielded prebiotic compounds from prolonged UV radiation. These particles settled into the lower atmosphere where they were scavenged by rain. Aqueous chemistry and evaporation of raindrops containing monomers in high temperature regions near the earth's surface also promoted continued formation of oligomers. Finally, these oligomers were deposited in the oceans where continued prebiotic evolution led to the most primitive cell. Results of present studies suggest that prebiotic chemical evolution may be an inevitable consequence of impacting comets during the late accretion of planets anywhere in the universe if oceans remained on those planetary surfaces.

  10. Gravitational radiation by point particle eccentric binary systems in the linearised characteristic formulation of general relativity

    NASA Astrophysics Data System (ADS)

    Cedeño Montaña, C. E.; de Araujo, J. C. N.

    2016-04-01

    We study a binary system composed of point particles of unequal masses in eccentric orbits in the linear regime of the characteristic formulation of general relativity, generalising a previous study found in the literature in which a system of equal masses in circular orbits is considered. We also show that the boundary conditions on the time-like world tubes generated by the orbits of the particles can be extended beyond circular orbits. Concerning the power lost by the emission of gravitational waves, it is directly obtained from the Bondi's News function. It is worth stressing that our results are completely consistent, because we obtain the same result for the power derived by Peters and Mathews, in a different approach, in their seminal paper of 1963. In addition, the present study constitutes a powerful tool to construct extraction schemes in the characteristic formalism to obtain the gravitational radiation produced by binary systems during the inspiralling phase.

  11. The characteristics of particle charging and deposition during powder coating processes with ultrafine powder

    NASA Astrophysics Data System (ADS)

    Meng, Xiangbo; Zhu, Jingxu Jesse; Zhang, Hui

    2009-03-01

    In a preceding work, the mechanisms of particle charging and deposition during powder coating processes were explored with coarse polyurethane powder. In this paper, the developed mechanisms were further examined with ultrafine polyurethane powder in order to meet the growing needs for ultrafine powder in finishing industries. This study first verified the previous findings in particle deposition, which account for a cone-shaped pattern formed by deposited particles on the substrate and a rise in particle accumulation in the fringe region. It was further demonstrated with ultrafine powder that, as disclosed by using coarse powder, the primary charging of in-flight particles competes with back corona in particle deposition processes, and the highest deposition efficiency is a compromise by balancing their effects. In comparison with coarse powder, ultrafine powder presents a faster reduction in the deposition rate with extended spraying duration, but shows some superiority in the uniformity of the deposited layer. In the case of charging characteristics of the deposited particles, it was further substantiated with ultrafine powder that the secondary charging mechanism takes predominance in determining the distribution of local charge-to-mass ratios. It was also disclosed that ultrafine powder shows a decreasing charge-to-mass ratio with increased charging voltage in the deposited layer, opposite to the increasing tendency of coarse powder. However, it was commonly demonstrated by both coarse and ultrafine powders that the charge-to-mass ratio of the deposited particles decreases with the extended spraying durations. In comparison, ultrafine powder is more likely to produce uniform charge-to-mass ratio distributions in the deposited layer, which contrast sharply with the ones associated with the coarse powder. In conclusion, it is believed that this study supplements the preceding study and is of great help in providing a comprehensive understanding of the mechanisms

  12. Settleability and characteristics of ferrate(VI)-induced particles in advanced wastewater treatment.

    PubMed

    Zheng, Lei; Deng, Yang

    2016-04-15

    Ferrate(VI) as an emerging water treatment agent has recently recaptured interests for advanced wastewater treatment. A large number of studies were published to report ferrate(VI)-driven oxidation for various water contaminants. In contrast, very few efforts were made to characterize ferrate(VI) resultant particles in water and wastewater. In this study, jar tests were performed to examine the settleability and characteristics of ferrate(VI)-induced iron oxide particles, particularly the non-settable fraction of these particles, after ferrate(VI) reduction in a biologically treated municipal wastewater. The particle settleability was evaluated through the measurement of turbidity and particulate iron concentration in the supernatant with the settling time. Results showed that a majority of ferrate(VI)-induced iron oxide aggregates remained suspended and caused an increased turbidity. For example, at a Fe(VI) dose of 5.0 mg/L and pH 7.50, 82% of the added iron remained in the supernatant and the turbidity was 8.97 NTU against the untreated sample turbidity (2.33 NTU) after 72-h settling. The poor settling property of these particles suggested that coagulation and flocculation did not perform well in the ferrate(VI) treatment. Particle size analysis and transmission electron microscopy (TEM) revealed that nano-scale particles were produced after ferrate(VI) decomposition, and gradually aggregated to form micro-scale larger particles in the secondary effluent. Zeta potentials of the non-settable ferrate(VI) resultant aggregates varied between -7.36 and -8.01 mV at pH 7.50 during the 72-h settling. The negative surface charges made the aggregates to be relatively stable in the wastewater matrix. PMID:26900976

  13. Deposition characteristics of copper particles on roughened substrates through kinetic spraying

    NASA Astrophysics Data System (ADS)

    Kumar, S.; Bae, Gyuyeol; Lee, Changhee

    2009-01-01

    In this paper, a systematic study of copper particle deposition behavior on polished and roughened surfaces (aluminum and copper) in kinetic spray process has been performed. The particle deformation behavior was simulated through finite element analysis (FEA) software ABAQUS explicit 6.7-2. The particle-substrate contact time, contact temperature and contact area upon impact have been estimated for smooth and three different roughened substrate cases. Copper powders were deposited on smooth and grit-blasted copper and aluminium substrates and characterized through scanning electron microscopy and Romulus bond strength analyzer. The results indicate that the deformation and the resultant bonding were higher for the roughened substrates than that of smooth. The characteristic factors for bonding are reported and discussed. Thus the substrate roughness appears to be beneficial for the initial deposition efficiency of the kinetic spray process.

  14. Effects of particle characteristics on performance of RR5K PETN

    SciTech Connect

    Rogers, J.W. Jr.; Duncan, A.A.

    1982-06-01

    A particle characterization of production lots of RR5K PETN has been completed. Prediction models were derived which identify those particle characteristics which influence sensitivity and performance. Those factors which have a positive influence on threshold burst current were also found to have a positive influence on transit time. The models may be useful in screening new lots of PETN prior to test firing. In general, large distributions of shapes and sizes, with the larger particles being needle-like or elongated, lead to low threshold burst currents and short transit times. The threshold burst current was also found to be inversely proportional to the temperature at which the units were test fired.

  15. Characteristics of shear layer with pyrolysing coal particles in one of the streams

    SciTech Connect

    Gollahalli, S.R.; Butuk, N.

    1998-07-01

    This article presents an experimental study of the growth and structure of a two-dimensional shear layer formed by two gas streams, one of which contained coal particles undergoing pyrolysis. Apparatus consisted of a low speed shear layer wind-tunnel designed to generate two gas streams, initially with uniform velocity profiles and isotropic turbulence, which mix at the end of a splitter plate. A fluidized bed injector system was used to introduce bituminous coal particles into one of the streams which was heated to cause their pyrolysis. The test section was optically accessible. The instrumentation included thermocouple, Pitot tube, laser velocimeter, and gas analyzers. Velocity profiles, temperature profiles, shear layer growth rate parameter, and turbulent intensity measurements were obtained. Results indicate that the presence of coal particles affect the velocity and decreases the shear layer growth rate (visible and vorticity thickness) significantly; however, the mass addition due to pyrolysis alone does not change the shear layer characteristics significantly.

  16. Role of cathode identity in liquid chromatography particle beam glow discharge mass spectrometry

    NASA Astrophysics Data System (ADS)

    Krishna, M. V. Balarama; Marcus, R. K.

    2008-06-01

    A detailed evaluation of the role of cathode identity on the analytical and spectral characteristics of various organic, organometallic and metal analytes using liquid chromatography-particle beam/glow discharge mass spectrometry (LC-PB/GDMS) has been carried out. A d.c. discharge, operating with argon as the support gas, was used throughout this work. In this study, Cu which has a relatively high sputtering rate, Ni which has moderate sputtering rate and Ta which has very low sputtering rate, are taken as cathode materials to study the ionization, fragmentation, and analytical characteristics of organic (caffeine, epigallocatechin gallate, peptide as representative compounds), organometallic (selenomethionine, triethyl lead chloride as representative compounds) and metal (Fe, La, Cs and Pb) species. A range of discharge gas pressures (26.6-106.4 Pa) and currents (0.2-1.5 mA) were investigated with the test cathodes to determine their influence on the spectral composition and overall analytical response for the various test species. Calibration plots were obtained for all of the species for each of the three cathodes to determine the respective limits of detection. Relative detection limits in the range of 0.02 to 15 ng mL - 1 (0.002-1.5 ng, absolute) for the test species were found to be in the order of Cu > Ni > Ta; which follows the order of the sputtering characteristics of the respective cathodes. These studies rendered information about the respective discharge parameters' role in choosing the most appropriate cathode identity in PB-GDMS for application in the areas of organic, organometallic and inorganic species analysis.

  17. Silica-graphene oxide hybrid composite particles and their electroresponsive characteristics.

    PubMed

    Zhang, Wen Ling; Choi, Hyoung Jin

    2012-05-01

    Silica-graphene oxide (Si-GO) hybrid composite particles were prepared by the hydrolysis of tetraethyl orthosilicate (TEOS) in the presence of hydrophilic GO obtained from a modified Hummers method. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images provided visible evidence of the silica nanoparticles grafted on the surface of GO, resulting in Si-GO hybrid composite particles. Energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) spectra indicated the coexistence of silica and GO in the composite particles. The Si-GO hybrid composite particles showed better thermal stability than that of GO according to thermogravimetric analysis (TGA). The electrorheological (ER) characteristics of the Si-GO hybrid composite based ER fluid were examined further by optical microscopy and a rotational rheometer in controlled shear rate mode under various electric field strengths. Shear stress curves were fitted using both conventional Bingham model and a constitutive Cho-Choi-Jhon model. The polarizability and relaxation time of the ER fluid from dielectric spectra measured using an LCR meter showed a good correlation with its ER characteristics. PMID:22486527

  18. Effect of non-Newtonian characteristics of blood on magnetic particle capture in occluded blood vessel

    NASA Astrophysics Data System (ADS)

    Bose, Sayan; Banerjee, Moloy

    2015-01-01

    Magnetic nanoparticles drug carriers continue to attract considerable interest for drug targeting in the treatment of cancer and other pathological conditions. Magnetic carrier particles with surface-bound drug molecules are injected into the vascular system upstream from the desired target site, and are captured at the target site via a local applied magnetic field. Herein, a numerical investigation of steady magnetic drug targeting (MDT) using functionalized magnetic micro-spheres in partly occluded blood vessel having a 90° bent is presented considering the effects of non-Newtonian characteristics of blood. An Eulerian-Lagrangian technique is adopted to resolve the hemodynamic flow and the motion of the magnetic particles in the flow using ANSYS FLUENT. An implantable infinitely long cylindrical current carrying conductor is used to create the requisite magnetic field. Targeted transport of the magnetic particles in a partly occluded vessel differs distinctly from the same in a regular unblocked vessel. Parametric investigation is conducted and the influence of the insert configuration and its position from the central plane of the artery (zoffset), particle size (dp) and its magnetic property (χ) and the magnitude of current (I) on the "capture efficiency" (CE) is reported. Analysis shows that there exists an optimum regime of operating parameters for which deposition of the drug carrying magnetic particles in a target zone on the partly occluded vessel wall can be maximized. The results provide useful design bases for in vitro set up for the investigation of MDT in stenosed blood vessels.

  19. Study of particle rebound characteristics and material erosion at high temperature

    SciTech Connect

    Tabakoff, W.; Hamed, A.; Metwally, A.; Yeuan, J.; Pasin, M. . Dept. of Aerospace Engineering and Engineering Mechanics)

    1990-10-01

    An experimental investigation was conducted to study the ash particle rebound characteristics and the associated erosion behavior of superalloys and aluminide coatings subjected to gas-particle flows at elevated temperatures. At three-component LDV system was used to measure the restitution parameters of 15 micron mean diameter coal ash particles impacting some widely used superalloys and coatings at different angles. Results show the variation restitution ratios with the impingement angle for the coated and uncoated superalloys. Experimental results were used to develop correlations for the restitution parameters for coated and uncoated superalloys. A theoretical model based on elastic-plastic theory has been developed to simulate single solid particle impacts on solid targets. The erosion behaviors of many superalloys and protective coatings have also been investigated experimentally at high temperatures using a specially designed erosion tunnel. Also, the cumulative effect of the impacting particle mass on the weight loss and erosion rate were investigated. Semi-empirical erosion equations were developed for these materials based on the experimental erosion data and correlations of the restitution parameters. Coatings tested include: platinum alimunides, cobalt aluminides, nickel aluminides, rhodium platinum aluminides, and chromium carbide. Superalloys tested were nickel base alloys Inco in-738 and Mar-M246, as well as Cobalt base alloys X40 and FSX-414. 10 refs., 86 figs., 5 tabs.

  20. The effect of ash and filter media characteristics on particle filtration efficiency in fluidized bed.

    PubMed

    Wey, Ming-Yen; Chen, Ke-Hao; Liu, Kuang-Yu

    2005-05-20

    The phenomenon of filtering particles by a fluidized bed is complex and the parameters that affect the control efficiency of filtration have not yet been clarified. The major objective of the study focuses on the effect of characteristics of ash and filter media on filtration efficiency in a fluidized bed. The performance of the fluidized bed for removal of particles in flue gas at various fluidized operating conditions, and then the mechanisms of collecting particles were studied. The evaluated parameters included (1) various ashes (coal ash and incinerator ash); (2) bed material size; (3) operating gas velocity; and (4) bed temperature. The results indicate that the removal efficiency of coal ash increases initially with gas velocity, then decreases gradually as velocity exceeds some specific value. Furthermore, the removal of coal ash enhance with silica sand size decreasing. When the fluidized bed is operated at high temperature, diffusion is a more important mechanism than at room temperature especially for small particles. Although the inertial impaction is the main collection mechanism, the "bounce off" effect when the particles collide with the bed material could reduce the removal efficiency significantly. Because of layer inversion in fluidized bed, the removal efficiency of incinerator ash is decreased with increasing of gas velocity. PMID:15885419

  1. Physicochemical characteristics and toxic effects of ozone-oxidized black carbon particles

    NASA Astrophysics Data System (ADS)

    Li, Qian; Shang, Jing; Zhu, Tong

    2013-12-01

    Black carbon (BC) or soot particles formed by combustion are ubiquitous in the atmosphere and have a significant effect on climate and human health. Oxidation can change the physicochemical characteristics of BC, thereby increasing its toxicity. The physicochemical properties of BC and ozone-oxidized BC are investigated in this study through transmission electron microscopy, X-ray photoelectron spectroscopy, diffuse reflectance infrared Fourier transform spectroscopy, ultraviolet-visible spectrophotometry, and electron paramagnetic resonance. The contents of oxygen-containing functional groups, hydrophilicity, water-soluble organic compounds, and free radicals increased after ozone treatment. The redox capacity and cytotoxicity of BC particles were enhanced by ozone oxidation as detected by dithiothreitol (DTT) and 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide assays. The redox activities of different BC particles are compared. Particle phase contributed significantly to total redox activity as detected by the DTT assay. Results indicate that BC particles that have undergone aging in the atmosphere may be more toxic and harmful to human health.

  2. Characteristics and sources of intermediate size particles in recovery boilers : final project report.

    SciTech Connect

    Baxter, Larry L.; Shaddix, Christopher R.; Verrill, Christopher L.; Wessel, Richard A.

    2005-02-01

    As part of the U.S. Department of Energy (DOE) Office of Industrial Technologies (OIT) Industries of the Future (IOF) Forest Products research program, a collaborative investigation was conducted on the sources, characteristics, and deposition of particles intermediate in size between submicron fume and carryover in recovery boilers. Laboratory experiments on suspended-drop combustion of black liquor and on black liquor char bed combustion demonstrated that both processes generate intermediate size particles (ISP), amounting to 0.5-2% of the black liquor dry solids mass (BLS). Measurements in two U.S. recovery boilers show variable loadings of ISP in the upper furnace, typically between 0.6-3 g/Nm{sup 3}, or 0.3-1.5% of BLS. The measurements show that the ISP mass size distribution increases with size from 5-100 {micro}m, implying that a substantial amount of ISP inertially deposits on steam tubes. ISP particles are depleted in potassium, chlorine, and sulfur relative to the fuel composition. Comprehensive boiler modeling demonstrates that ISP concentrations are substantially overpredicted when using a previously developed algorithm for ISP generation. Equilibrium calculations suggest that alkali carbonate decomposition occurs at intermediate heights in the furnace and may lead to partial destruction of ISP particles formed lower in the furnace. ISP deposition is predicted to occur in the superheater sections, at temperatures greater than 750 C, when the particles are at least partially molten.

  3. Characteristics of different fractions of microbial flocs and their role in membrane fouling.

    PubMed

    Lin, H J; Gao, W J; Leung, K T; Liao, B Q

    2011-01-01

    Characteristics of different fractions (small flocs vs. large flocs) of sludge flocs from a submerged anaerobic membrane bioreactor treating thermomechanical pulping (TMP) whitewater were determined using various analytic techniques, including extraction and chemical analysis of extracellular polymeric substances (EPS), particle size analyzer, and polymer chain reaction (PCR)-denaturing gradient gel electrophoresis (DGGE). The results showed that the fraction of smaller flocs contained a higher level of bound EPS and had a higher fractal dimension as compared to the fraction of larger flocs. PCR-DGGE analysis indicated that there were significant differences in microbial community between the fraction of smaller flocs and large flocs. The microbial community of the smaller flocs was similar to that of the sludge cake layers, indicating the pioneering role of the microbial community in smaller flocs in membrane fouling. These findings provide a new insight in the difference of membrane fouling potential between smaller flocs and larger flocs fraction. PMID:21252429

  4. The role of large particles in the formation of the radio echo

    NASA Technical Reports Server (NTRS)

    Salman, Y. M.

    1975-01-01

    The contribution to the total reflectivity of separate parts of a particle spectrum described by a gamma distribution is estimated. It is shown that the largest individual particles, whose percent concentration is 0.1 - 1, originate approximately 60 - 70% of the total reflectivity of the spectrum. Explanations are given of a number of effects which confirm the dominant role of large particles in the formation of the echo.

  5. Characteristics and Functional Roles of Opioids Originally Present in Vivo.

    PubMed

    Ozaki, Masanobu

    2016-01-01

    The characteristics and functional roles of opioids originally present in vivo (endogenous opioids) in guinea-pig ileum were investigated. The release of endogenous opioids was determined by the inhibitory twitch response evoked by 0.1 Hz stimulation after 10 Hz stimulation (post-tetanic twitch inhibition). The effects of peptidase inhibitors increased the post-tetanic twitch inhibition, prevented by β-funaltrexamine and nor-binaltorphimine, which are selective μ- and κ-opioid receptor subtype antagonists, respectively. Dopamine receptor antagonists (haloperidol, sultopride and domperidone) increased the post-tetanic twitch inhibition. These results suggest that dopamine receptors are involved in modulation of the ileal opioid system, so as to diminish endogenous opioid release by tetanic stimulation, and dopamine antagonists increase the opioid action, that might depend more on the increased release of endogenous opioids. The post-tetanic twitch inhibition was inhibited by adrenalectomy, and showed the supersensitivity of the opioid receptors, resulting from a decrease of endogenous opioids by adrenalectomy. These findings suggest that the increase in morphine-analgesia by adrenalectomy was due to this process. In the presence of naloxone, an opioid antagonist, an increase in basal tension after tetanic stimulation (10 Hz stimulation) (post-tetanic contraction) was observed, and was blocked by spantide, a substance P antagonist, and indomethacin, a prostaglandins-biosynthesis inhibitor. This contraction increased with morphine or peptidase inhibitor exposure, depending on the length of time the ileum was exposed to the morphine or peptidase inhibitor. Post-tetanic contraction might be a useful indicator of the formation of physical dependence to morphine or endogenous opioids in the ileum. PMID:27040344

  6. Geochemically structural characteristics of municipal solid waste incineration fly ash particles and mineralogical surface conversions by chelate treatment.

    PubMed

    Kitamura, Hiroki; Sawada, Takaya; Shimaoka, Takayuki; Takahashi, Fumitake

    2016-01-01

    Leaching behaviors of heavy metals contained in municipal solid waste incineration (MSWI) fly ash have been studied well. However, micro-characteristics of MSWI fly ash particles are still uncertain and might be non-negligible to describe their leaching behaviors. Therefore, this study investigated micro-characteristics of MSWI fly ash particles, especially their structural properties and impacts of chelate treatment on surface characteristics. According to SEM observations, raw fly ash particles could be categorized into four types based on their shapes. Because chelate treatment changed the surface of fly ash particles dramatically owing to secondary mineral formations like ettringite, two more types could be categorized for chelate-treated fly ash particles. Acid extraction experiments suggest that fly ash particles, tested in this study, consist of Si-base insoluble core structure, Al/Ca/Si-base semi-soluble matrices inside the body, and KCl/NaCl-base soluble aggregates on the surface. Scanning electron microscope (SEM) observations of the same fly ash particles during twice moistening treatments showed that KCl/NaCl moved under wet condition and concentrated at different places on the particle surface. However, element mobility depended on secondary mineral formations. When insoluble mineral like gypsum was generated and covered the particle surface, it inhibited element transfer under wet condition. Surface characteristics including secondary mineral formation of MSWI fly ash particles are likely non-negligible to describe trace element leaching behaviors. PMID:26336844

  7. The neutron and its role in cosmology and particle physics

    SciTech Connect

    Dubbers, Dirk; Schmidt, Michael G.

    2011-10-01

    Experiments with cold and ultracold neutrons have reached a level of precision such that problems far beyond the scale of the present standard model of particle physics become accessible to experimental investigation. Because of the close links between particle physics and cosmology, these studies also permit a deep look into the very first instances of our Universe. First addressed in this article, in both theory and experiment, is the problem of baryogenesis, the mechanism behind the evident dominance of matter over antimatter in the Universe. The question of how baryogenesis could have happened is open to experimental tests, and it turns out that this problem can be curbed by the very stringent limits on an electric dipole moment of the neutron, a quantity that also has deep implications for particle physics. Then the recent spectacular observation of neutron quantization in the Earth's gravitational field and of resonance transitions between such gravitational energy states is discussed. These measurements, together with new evaluations of neutron scattering data, set new constraints on deviations from Newton's gravitational law at the picometer scale. Such deviations are predicted in modern theories with extra dimensions that propose unification of the Planck scale with the scale of the standard model. These experiments start closing the remaining ''axion window'' on new spin-dependent forces in the submillimeter range. Another main topic is the weak-interaction parameters in various fields of physics and astrophysics that must all be derived from measured neutron-decay data. Up until now, about 10 different neutron-decay observables have been measured, much more than needed in the electroweak standard model. This allows various precise tests for new physics beyond the standard model, competing with or surpassing similar tests at high energy. The review ends with a discussion of neutron and nuclear data required in the synthesis of the elements during the

  8. Deciphering The Role of Plankton Taxa in Particle Flux

    NASA Astrophysics Data System (ADS)

    Neuer, Susanne; Amacher, Jessica; DeMartini, Francesca; Wilson, Stephanie

    2015-04-01

    The sinking of phytoplankton derived particulate organic matter to the deep ocean constitutes an important removal process of atmospheric CO2 and is termed the biological carbon pump. Understanding the taxon specific connection between phytoplankton communities in the euphotic zone and their contribution to particle flux is a high priority in current oceanographic research and provides a basis to evaluate how carbon export might change in a future ocean. Here we present results from DNA-based molecular studies that investigate the taxonomic composition of cyanobacterial and protist communities retrieved from shallow particle traps in comparison to those living in the euphotic zone. This research has been mainly carried out in the Sargasso Sea at the Bermuda Atlantic Time-series Study site (BATS). Trap material collected at this oligotrophic ocean site reveals a surprisingly high diversity of small, non-mineral ballasted taxa, some of which are over-represented compared to the euphotic zone communities. But the majority of clones in the traps belong to mostly heterotrophic protist taxa. By analyzing the fingerprints of prey DNA in guts and fecal pellets of dominant zooplankton grazers we find that there is a close link between prey utilization and the recovery of those taxa in the traps, showing the importance of fecal pellets in packaging and mediating their flux out of the euphotic zone.

  9. The Role of Precipitating Energetic Particles in Coupling Atmospheric Regions

    NASA Astrophysics Data System (ADS)

    Bailey, S. M.; Randall, C. E.; Solomon, S. C.; Yee, S.; Kozyra, J. U.; Baker, D. N.

    2010-12-01

    A key missing element in our understanding of the Sun-Earth system is the response of the atmosphere when precipitating particle energy is redistributed via dynamical, chemical, and radiative processes. Elucidating the coupling intrinsic to this response is a prerequisite for understanding and predicting variability in and across many atmospheric regions. A priority for future observations is the Energetic Particle Precipitation (EPP) Indirect Effect (IE), by which odd nitrogen compounds produced by EPP in the upper atmosphere descend to the stratosphere, perturbing ozone chemistry and thus the radiative balance of the middle atmosphere. It has been shown that EPP IE occurs nearly every year in both hemispheres, and is modulated by variability in both the EPP and atmospheric meteorology. In this talk, we will summarize the current state of knowledge of EPP IE, the observational evidence for it in the last few decades, and what is required of future observations. We will discuss the advantages and disadvantages of various measurement techniques for observing odd nitrogen and descent, along with uncertainties in the analysis methods.

  10. Characteristics of polycyclic aromatic hydrocarbons and their gas/particle partitioning from fugitive emissions in coke plants

    NASA Astrophysics Data System (ADS)

    Mu, Ling; Peng, Lin; Liu, Xiaofeng; Song, Chongfang; Bai, Huiling; Zhang, Jianqiang; Hu, Dongmei; He, Qiusheng; Li, Fan

    2014-02-01

    Coking is one of the most important emission sources of polycyclic aromatic hydrocarbons (PAHs) in China. However, there is little information available on the emission characteristics of PAHs from fugitive emission during coking, especially on the specific processes dominating the gas-particle partitioning of PAHs. In this study, emission characteristics and gas-particle partitioning of PAHs from fugitive emission in four typical coke plants (CPs) with different scales and techniques were investigated. The average concentrations of total PAHs from fugitive emission at CP2, CP3 and CP4 (stamp charging) were 146.98, 31.82, and 35.20 μg m-3, which were 13.38-, 2.90- and 3.20-fold higher, respectively, than those at CP1 (top charging, 10.98 μg m-3). Low molecular weight PAHs with 2-3 rings made up 75.3% of the total PAHs on average, and the contributions of particulate PAH to the total BaP equivalent concentrations (BaPeq) in each plant were significantly higher than the corresponding contributions to the total PAH mass concentrations. The calculated total BaPeq concentrations varied from 0.19 to 10.86 μg m-3 with an average of 3.14 μg m-3, and more efficient measures to control fugitive emission in coke plants should be employed to prevent or reduce the health risk to workers. Absorption into organic matter dominated the gas-particle partitioning for most of the PAHs including PhA, FluA, Chr, BbF, BkF and BaP, while adsorption on elemental carbon appeared to play a dominant role for AcPy, AcP and Flu.

  11. Particle characteristics of different materials after ultra-short pulsed laser (USPL) irradiation

    NASA Astrophysics Data System (ADS)

    Meister, Joerg; Schelle, Florian; Kowalczyk, Philip; Frentzen, Matthias

    2012-01-01

    The exposition of nanoparticles caused by laser application in dental health care is an open discussion. Based on the fact that nanoparticles can penetrate through the mucosa, the knowledge about particle characteristics after irradiation with an USPL is of high importance. Therefore, the aim of this study was to investigate the particle characteristics, especially the size of the ablated debris after USPL irradiation. The irradiation was carried out with an USP Nd:YVO4 laser with a center wavelength of 1064 nm. Based on the pulse duration of 8 ps and a pulse repetition rate of 500 kHz the laser emits an average power of 9 W. The materials investigated were dental tissues and dental restorative materials (composite and amalgam), ceramic and different metals (gold and aluminium). The samples were irradiated with a power density in the order of 300 GW/cm2 at distances of 5, 10, 15, and 20 mm. The debris was collected on an object plate. SEM pictures were used for analysis of the ablation debris. Depending on the irradiated material, we observed different kinds of structures: vitreous, flocculent, and pellet-like. The mean particle sizes were 10 x 10 up to 30 x 30 μm2. In addition, a cluster of ablated matter (nanometer range) distributed over the whole irradiated area was found. With increasing distances the cluster structure reduced from multi-layer to mono-layer clusters. Particle sizes in the micrometer and nanometer range were found after irradiation with an USPL. The nanoparticles create a cluster structure which is influenced by increasing distances.

  12. An in-pile testing program to study the performance characteristics of coated particle fuels

    SciTech Connect

    Wright, S.A. )

    1993-01-15

    Sandia National Laboratories is actively involved in testing coated particle nuclear fuels for the Space Nuclear Thermal Propulsion (SNTP) program managed by Phillips Laboratory. The testing program integrates the results of numerous in-pile and out-of-pile tests with modeling efforts to qualify fuel and fuel elements for the SNTP program. This paper briefly describes the capabilities of the Annular Core Research Reactor (in which the experiments are performed), the major in-pile tests, and the models used to determine the performance characteristics of the fuel and fuel elements.

  13. An in-pile testing program to study the performance characteristics of coated particle fuels

    SciTech Connect

    Wright, S.A.

    1992-01-01

    Sandia National Laboratories is actively involved in testing coated particle nuclear fuels for the Space Nuclear Thermal Propulsion (SNTP) program managed by Phillips Laboratory. The testing program integrates the results of numerous in-pile and out-of-pile tests with modeling efforts to qualify fuel and fuel elements for the SNTP program. This paper briefly describes the capabilities of the Annular Core Research Reactor (in which the experiments are performed), the major in-pile tests, and the models used to determine the performance characteristics of the fuel and fuel elements. 6 refs.

  14. The Dependence of Solar Energetic Particle Event Characteristics on Heliographic Longitude

    NASA Astrophysics Data System (ADS)

    Wiedenbeck, M. E.; Cohen, C. M.; Cummings, A. C.; Gómez-Herrero, R.; Haggerty, D. K.; Leske, R. A.; Mason, G. M.; Mewaldt, R. A.; Nitta, N. V.; Stone, E. C.; von Rosenvinge, T. T.

    2011-12-01

    Characteristics of solar energetic particle (SEP) events observed at 1 AU from the Sun are known to depend on the magnetic connection of the observer to the acceleration region as well as on whether the acceleration is associated with a shock ("gradual" SEP events) or with flare reconnection ("impulsive" events). Much of our present knowledge of the dependence of SEP event characteristics on heliographic longitude has been the result of single-spacecraft statistical studies that identified systematic correlations of various event properties (e.g., rise time, peak intensity, composition) with the location of the observer relative to the magnetic field line having the best connection to the solar source region. Several studies combining SEP observations made near Earth with data from spacecraft at other heliographic longitudes (Helios and various planetary missions) or latitudes (Ulysses) have also contributed. The two STEREO spacecraft, in conjunction with ACE and Wind operating near Earth, have enabled the first systematic study of the longitudinal dependence of SEP characteristics in individual events at 1 AU. The years 2007 through 2010, during which longitudinal separations of the STEREOs from Earth increased from 0o to nearly 90o, were characterized by a very low level of solar activity. These conditions allowed unusually sensitive measurements of a number of impulsive SEP events and led to the realization that particles accelerated in these events are frequently detectable over a range of longitudes much greater than expected from simple models in which flare-accelerated particles escape into the heliosphere along small clusters of open field lines involved in a reconnection event. Particle fluences, however, were found to have a strong dependence on separation from the well-connected longitude. Since early 2011, as solar activity has been on the increase, a number of gradual SEP events have been observed over the >180o range of heliographic longitudes now

  15. Submersible holocamera for detection of particle characteristics and motions in the ocean

    NASA Astrophysics Data System (ADS)

    Katz, J.; Donaghay, P. L.; Zhang, J.; King, S.; Russell, K.

    1999-08-01

    A submersible holographic camera has been developed for measuring the particle distributions, characteristics and motions within a sample volume in the ocean. Its main purpose is to provide data on the spatial distribution, size, shape, orientation, inter-particle relationships, turbulence, local shear and relative motion due to swimming and sinking of plankton. This battery powered, modular, self-contained system is remotely operated by a PC through fiber optic links. Data from on-board environmental sensors are used to select locations for recording holograms and relating the images to broader scale physical structures. The holocamera also has a buoyancy control system that allows deployment as a neutrally buoyant drifter or in a slow profiling mode. The instrument is currently configured for in-line holography, but it has been designed to be readily adaptable to off-axis holography. The cylindrical sample volume is 6.3 cm in diameter and its length can be varied from 10 to 68 cm. The light source is a pulsed ruby laser chosen predominantly because zooplankton are typically less sensitive to red light. The laser has independent dual flashlamps for maximum flexibility in selecting delay between exposures. About 300 single or multiple exposure holograms can be recorded during a single deployment. Data such as particle size, shape, orientation, distribution in space and velocity are obtained by reconstructing the holograms, scanning them with a video camera equipped with a microscope objective, digitizing the images and analyzing relevant data. Several recent field tests have demonstrated the system reliability and resolution. Particles with sizes as small as 10 μm and details on cell structures of larger particles in the 3-5 μm range could be identified and used for identifying and categorizing the particles. Sample single and double exposure images, the latter for measuring motion, and sample spatial distributions are provided. Methods for mapping the liquid

  16. Self-assembly of virus particles: The role of genome

    NASA Astrophysics Data System (ADS)

    Erdemci-Tandogan, Gonca; Wagner, Jef; Podgornik, Rudolf; Zandi, Roya

    2013-03-01

    A virus is an infectious agent that inserts its genetic material into the cell and hijacks the cell's machinery to reproduce. The simplest viruses are made of a protein shell (capsid) that protects its genome (DNA or RNA). Many plant and animal viruses can be assembled spontaneously from a solution of proteins and genetic material in different capsid shapes and sizes. This work focuses on the role of genome in the assembly of spherical RNA viruses. The RNA, a highly flexible polymer, is modeled by mean field approximations. Two RNA models are discussed: (i) A linear polymer model including a pairing affinity between RNA base pairs, and (ii) a branched polymer model. Polymer density and electrostatic potential profiles are obtained, and the relevant free energies are calculated from these profiles. The optimal length of the encapsidated chain is examined as a function of the model parameters. The osmotic pressure of the system is also discussed.

  17. Impact of polymer surface characteristics on the microrheological measurement quality of protein solutions - A tracer particle screening.

    PubMed

    Bauer, Katharina Christin; Schermeyer, Marie-Therese; Seidel, Jonathan; Hubbuch, Jürgen

    2016-05-30

    Microrheological measurements prove to be suitable to identify rheological parameters of biopharmaceutical solutions. These give information about the flow characteristics but also about the interactions and network structures in protein solutions. For the microrheological measurement tracer particles are required. Due to their specific surface characteristic not all are suitable for reliable measurement results in biopharmaceutical systems. In the present work a screening of melamine, PMMA, polystyrene and surface modified polystyrene as tracer particles were investigated at various protein solution conditions. The surface characteristics of the screened tracer particles were evaluated by zeta potential measurements. Furthermore each tracer particle was used to determine the dynamic viscosity of lysozyme solutions by microrheology and compared to a standard. The results indicate that the selection of the tracer particle had a strong impact on the quality of the microrheological measurement dependent on pH and additive type. Surface modified polystyrene was the only tracer particle that yielded good microrheological results for all tested conditions. The study indicated that the electrostatic surface charge of the tracer particle had a minor impact than its hydrophobicity. This characteristic was the crucial surface property that needs to be considered for the selection of a suitable tracer particle to achieve high measurement accuracy. PMID:27025292

  18. Solid particle impingement erosion characteristics of cylindrical surfaces, pre-existing holes and slits

    NASA Technical Reports Server (NTRS)

    Rao, P. V.; Buckley, D. H.

    1983-01-01

    The erosion characteristics of aluminum cylinders sand-blasted with both spherical and angular erodent particles were studied and compared with results from previously studied flat surfaces. The cylindrical results are discussed with respect to impact conditions. The relationship between erosion rate and pit morphology (width, depth, and width to depth ratio) is established. The aspects of (1) erosion rate versus time curves on cylindrical surfaces; (2) long-term exposures; and (3) erosion rate versus time curves with spherical and angular particles are presented. The erosion morphology and characteristics of aluminum surfaces with pre-existing circular cylindrical and conical holes of different sizes were examined using weight loss measurements, scanning electron microscopy, a profilometer, and a depth gage. The morphological features (radial and concentric rings) are discussed with reference to flat surfaces, and the erosion features with spherical microglass beads. The similarities and differences of erosion and morphological features are highlighted. The erosion versus time curves of various shapes of holes are discussed and are compared with those of a flat surface. The erosion process at slits is considered.

  19. Mass concentration and mineralogical characteristics of aerosol particles collected at Dunhuang during ACE-Asia

    NASA Astrophysics Data System (ADS)

    Shen, Z. X.; Cao, J. J.; Li, X. X.; Okuda, T.; Wang, Y. Q.; Zhang, X. Y.

    2006-03-01

    Measurements were performed in spring 2001 and 2002 to determine the characteristics of soil dust in the Chinese desert region of Dunhuang, one of the ground sites of the Asia-Pacific Regional Aerosol Characterization Experiment (ACE-Asia). The mean mass concentrations of total suspended particle matter during the spring of 2001 and 2002 were 317 mu g m(-3) and 307 mu g m(-3) respectively. Eleven dust storm events were observed with a mean aerosol concentration of 1095 mu g m(-3), while the non-dusty days with calm or weak wind speed had a background aerosol loading of 196 mu g m(-3) on average in the springtime. The main minerals detected in the aerosol samples by X-ray diffraction were illite, kaolinite, chlorite, quartz, feldspar, calcite and dolomite. Gypsum, halite and amphibole were also detected in a few samples. The mineralogical data also show that Asian dust is characterized by a kaolinite to chlorite (K/C) ratio lower than 1 whereas Saharan dust exhibits a K/C ratio larger than 2. Air mass back- trajectory analysis show that three families of pathways are associated with the aerosol particle transport to Dunhuang, but these have similar K/C ratios, which further demonstrates that the mineralogical characteristics of Asian dust are different from African dust.

  20. Response characteristics of laser diffraction particle size analyzers - Optical sample volume extent and lens effects

    NASA Technical Reports Server (NTRS)

    Hirleman, E. D.; Oechsle, V.; Chigier, N. A.

    1984-01-01

    The response characteristics of laser diffraction particle sizing instruments were studied theoretically and experimentally. In particular, the extent of optical sample volume and the effects of receiving lens properties were investigated in detail. The experimental work was performed with a particle size analyzer using a calibration reticle containing a two-dimensional array of opaque circular disks on a glass substrate. The calibration slide simulated the forward-scattering characteristics of a Rosin-Rammler droplet size distribution. The reticle was analyzed with collection lenses of 63 mm, 100 mm, and 300 mm focal lengths using scattering inversion software that determined best-fit Rosin-Rammler size distribution parameters. The data differed from the predicted response for the reticle by about 10 percent. A set of calibration factor for the detector elements was determined that corrected for the nonideal response of the instrument. The response of the instrument was also measured as a function of reticle position, and the results confirmed a theoretical optical sample volume model presented here.

  1. The Role of Structural Characteristics in Problematic Video Game Play: An Empirical Study

    ERIC Educational Resources Information Center

    King, Daniel L.; Delfabbro, Paul H.; Griffiths, Mark D.

    2011-01-01

    The research literature suggests that the structural characteristics of video games may play a considerable role in the initiation, development and maintenance of problematic video game playing. The present study investigated the role of structural characteristics in video game playing behaviour within a sample of 421 video game players aged…

  2. Changes In The Characteristics of Basaltic Particles During Different Transport Processes

    NASA Astrophysics Data System (ADS)

    Craddock, R. A.; Rose, T. R.

    2014-12-01

    The physical and chemical characteristics of the grains in sedimentary deposits can provide valuable clues about transport processes, distance traveled, and provenance. A fundamental physical characteristic is particle shape, which is diagnostic of transport process as well as the distance traveled. For example, it is possible to distinguish the emplacement process of sediments based entirely on the shape of the quartz grains in the deposit [e.g., Folk, 1980]. Such basic sedimentological concepts have been applied to our interpretation of surface materials on the terrestrial planets [e.g. Cabrol et al., 2014]. However, what we know about the nature of sedimentary materials is based primarily on sediments that have weathered from felsic rocks—granite. This is true because felsic materials compose most of the landmass on the Earth. Yet, the surface of Mars is composed predominately of mafic materials—basalt—and sedimentary particles derived from basalt are much different than those derived from granite. Instead of quartz, feldspar, and heavy minerals commonly found in most terrestrial sedimentary deposits, basaltic sediments are typically composed of varying amounts of olivine, pyroxene, plagioclase, and vitric and lithic fragments. Both the persistence of basaltic particles and their specific gravities are different than particles derived from granite. These differences are important because they will affect the characteristics of basaltic sediment as it is transported by wind, water, and ice, and currently we have little to no understanding as to how basaltic sediment will weather as a function of the transport mechanism and distance. We will present preliminary analyses of typical basaltic sediments that have been transported by a variety of geologic processes in Hawaii, including details about surface texture, componentry, and the influence different sedimentary processes may have on remote sensing data. The figure below shows examples of A) sediment

  3. [Synergistic effects of nano-sized magnetic particles and uncoupler to the characteristics of activated sludge].

    PubMed

    Gao, Li-ying; Tang, Bing; Liang, Ling-yan; Huang, Shao-song; Fu, Feng-lian; Luo, Jian-zhong

    2012-08-01

    For improving the performance and sludge settling property of an activated sludge reduction process with uncoupler, in this investigation, uncoupler and nano-sized magnetic particles were added simultaneously to a sequencing batch reactor for exploring their synergistic effects to the characteristics of activated sludge. The results showed that the volume reduction of sludge reached 41% with single 2,4,5-Trichlorophenol (TCP) Comparing with the control experiment, the biodegradability and settling properties of the activated sludge decreased. Under the actions of TCP combined with nano-sized magnetic particles, the volume reduction of sludge reached 34%, the removal efficiencies of COD, nitrogen, and phosphorus as well as the sludge settling property were not significantly influenced. After 31 d's operation, the dehydrogenase activity was improved by 10%-18% and exhibited an accumulative effect over time. It was observed with an optical microscope that the species and amounts of protozoon and metazoan increased and a compact structure of sludge floc was formed. The results also indicated that using nano-sized magnetic particles and uncoupler could restrict the yield of excess sludge and improve the performance of an activated sludge system. PMID:23213903

  4. [Particle emission characteristics of diesel bus fueled with bio-diesel].

    PubMed

    Lou, Di-Ming; Chen, Feng; Hu, Zhi-Yuan; Tan, Pi-Qiang; Hu, Wei

    2013-10-01

    With the use of the Engine Exhaust Particle Sizer (EEPS), a study on the characteristics of particle emissions was carried out on a China-IV diesel bus fueled with blends of 5% , 10% , 20% , 50% bio-diesel transformed from restaurant waste oil and China-IV diesel (marked separately by BD5, BD10, BD20, BD50), pure bio-diesel (BD100) and pure diesel (BD0). The results indicated that particulate number (PN) and mass (PM) emissions of bio-diesel blends increased with the increase in bus speed and acceleration; with increasing bio-diesel content, particulate emissions displayed a relevant declining trend. In different speed ranges, the size distribution of particulate number emissions (PNSD) was bimodal; in different acceleration ranges, PNSD showed a gradual transition from bimodal shape to unimodal when bus operation was switched from decelerating to accelerating status. Bio-diesel blends with higher mixture ratios showed significant reduction in PN emissions for accumulated modes, and the particulate number emission peaks moved towards smaller sizes; but little change was obtained in PN emissions for nuclei modes; reduction also occurred in particle geometric diameter (Dg). PMID:24364288

  5. Role of Surface Area, Primary Particle Size, and Crystal Phase on Titanium Dioxide Nanoparticle Dispersion Properties

    PubMed Central

    2011-01-01

    Characterizing nanoparticle dispersions and understanding the effect of parameters that alter dispersion properties are important for both environmental applications and toxicity investigations. The role of particle surface area, primary particle size, and crystal phase on TiO2 nanoparticle dispersion properties is reported. Hydrodynamic size, zeta potential, and isoelectric point (IEP) of ten laboratory synthesized TiO2 samples, and one commercial Degussa TiO2 sample (P25) dispersed in different solutions were characterized. Solution ionic strength and pH affect titania dispersion properties. The effect of monovalent (NaCl) and divalent (MgCl2) inert electrolytes on dispersion properties was quantified through their contribution to ionic strength. Increasing titania particle surface area resulted in a decrease in solution pH. At fixed pH, increasing the particle surface area enhanced the collision frequency between particles and led to a higher degree of agglomeration. In addition to the synthesis method, TiO2 isoelectric point was found to be dependent on particle size. As anatase TiO2 primary particle size increased from 6 nm to 104 nm, its IEP decreased from 6.0 to 3.8 that also results in changes in dispersion zeta potential and hydrodynamic size. In contrast to particle size, TiO2 nanoparticle IEP was found to be insensitive to particle crystal structure. PMID:27502650

  6. A role of aerosol particles in forming urban skyglow and skyglow from distant cities

    NASA Astrophysics Data System (ADS)

    Kocifaj, Miroslav; Kómar, Ladislav

    2016-05-01

    Aerosol particles may represent the largest uncertainty about skyglow change in many locations under clear-sky conditions. This is because aerosols are ubiquitous in the atmosphere and influence the ground-reaching radiation in different ways depending on their concentrations, origins, shapes, sizes, and compositions. Large particles tend to scatter in Fraunhofer diffraction regime, while small particles can be treated in terms of Rayleigh formalism. However, the role of particle microphysics in forming the skyglow still remains poorly quantified. We have shown in this paper that the chemistry is somehow important for backscattering from large particles that otherwise work as efficient attenuators of light pollution if composed of absorbing materials. The contribution of large particles to the urban skyglow diminishes as they become more spherical in shape. The intensity of backscattering from non-absorbing particles is more-or-less linearly decreasing function of particle radius even if number size distribution is inversely proportional to the fourth power of particle radius. This is due to single particle backscattering that generally increases steeply as the particle radius approaches large values. Forward scattering depends on the particle shape but is independent of the material composition, thus allowing for a simplistic analytical model of skyglow from distant cities. The model we have developed is based on mean value theorem for integrals and incorporates the parametrizable Garstang's emission pattern, intensity decay along optical beam path, and near-forward scattering in an atmospheric environment. Such model can be used by modellers and experimentalists for rapid estimation of skyglow from distant light sources.

  7. Investigating the role of particle shape on colloid transport and retention in saturated porous media (Invited)

    NASA Astrophysics Data System (ADS)

    Li, Y.; Seymour, M.; Chen, G.; Su, C.

    2011-12-01

    Mechanistic understanding of the transport and retention of nanoparticles in porous media is essential both for environmental applications of nanotechnology and assessing the potential environmental impacts of engineered nanomaterials. Engineered and naturally occurring nanoparticles can be found in various shapes including rod-shape carbon nanotubes that have high aspect ratios. Although it is expected that nonspherical shape could play an important role on their transport and retention behaviors, current theoretical models for particle transport in porous media, however, are mostly based on spherical particle shape. In this work, the effect of particle shape on its transport and retention in porous media was evaluated by stretching carboxylate-modified fluorescent polystyrene spheres into rod shapes with aspect ratios of 2:1 and 4:1. Quartz crystal microbalance with dissipation experiments (QCM-D) were conducted to measure the deposition rates of spherical and rod-shaped nanoparticles to the collector (poly-L-lysine coated silica sensor) surface under favorable conditions. Under unfavorable conditions, the retention of nanoparticles in a microfluidic flow cell packed with glass beads was studied with the use of laser scanning cytometry (LSC). Under favorable conditions, the spherical particles displayed a significantly higher deposition rate compared with that of the rod-shaped particles. Theoretical analysis based on Smoluchowski-Levich approximation indicated that the rod-shaped particles largely counterbalance the attractive energies due to higher hydrodynamic forces and torques experienced during their transport and rotation. Under unfavorable conditions, significantly more attachment was observed for rod-shaped particles than spherical particles, and the attachment rate of the rod-shaped particles showed an increasing trend with the increase in injection volume. Rod-shaped particles were found to be less sensitive to the surface charge heterogeneity change

  8. Investigating the role of particle shape on colloid transport and retention in saturated porous media (Invited)

    NASA Astrophysics Data System (ADS)

    Li, Y.; Seymour, M.; Chen, G.; Su, C.

    2013-12-01

    Mechanistic understanding of the transport and retention of nanoparticles in porous media is essential both for environmental applications of nanotechnology and assessing the potential environmental impacts of engineered nanomaterials. Engineered and naturally occurring nanoparticles can be found in various shapes including rod-shape carbon nanotubes that have high aspect ratios. Although it is expected that nonspherical shape could play an important role on their transport and retention behaviors, current theoretical models for particle transport in porous media, however, are mostly based on spherical particle shape. In this work, the effect of particle shape on its transport and retention in porous media was evaluated by stretching carboxylate-modified fluorescent polystyrene spheres into rod shapes with aspect ratios of 2:1 and 4:1. Quartz crystal microbalance with dissipation experiments (QCM-D) were conducted to measure the deposition rates of spherical and rod-shaped nanoparticles to the collector (poly-L-lysine coated silica sensor) surface under favorable conditions. Under unfavorable conditions, the retention of nanoparticles in a microfluidic flow cell packed with glass beads was studied with the use of laser scanning cytometry (LSC). Under favorable conditions, the spherical particles displayed a significantly higher deposition rate compared with that of the rod-shaped particles. Theoretical analysis based on Smoluchowski-Levich approximation indicated that the rod-shaped particles largely counterbalance the attractive energies due to higher hydrodynamic forces and torques experienced during their transport and rotation. Under unfavorable conditions, significantly more attachment was observed for rod-shaped particles than spherical particles, and the attachment rate of the rod-shaped particles showed an increasing trend with the increase in injection volume. Rod-shaped particles were found to be less sensitive to the surface charge heterogeneity change

  9. Chemical characteristics and source of size-fractionated atmospheric particle in haze episode in Beijing

    NASA Astrophysics Data System (ADS)

    Tan, Jihua; Duan, Jingchun; Zhen, Naijia; He, Kebin; Hao, Jiming

    2016-01-01

    The abundance, behavior, and source of chemical species in size-fractionated atmospheric particle were studied with a 13-stage low pressure impactor (ELPI) during high polluted winter episode in Beijing. Thirty three elements (Al, Ca, Fe, K, Mg, Na, Si, Sc, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Sr, Zr, Mo, Ag, Cd, In, Sn, Sb, Cs, Ba, Hg, Tl, and Pb) and eight water soluble ions (Cl-, NO3-, SO42 -, NH4+, Na+, K+, Ca2 +, and Mg2 +) were determined by ICP/MS and IC, respectively. The size distribution of TC (OC + EC) was reconstructed. Averagely, 51.5 ± 5.3% and 74.1 ± 3.7% of the total aerosol mass was distributed in the sub-micron (PM1) and fine particle (PM2.5), respectively. A significant shift to larger fractions during heavy pollution episode was observed for aerosol mass, NH4+, SO42 -, NO3-, K, Fe, Cu, Zn, Cd, and Pb. The mass size distributions of NH4+, SO42 -, NO3-, and K were dominated by accumulation mode. Size distributions of elements were classified into four main types: (I) elements were enriched within the accumulation mode (< 1 μm, Ge, Se, Ag, Sn, Sb, Cs, Hg, Ti, and Pb); (II) those mass (K, Cr, Mn, Cu, Zn, As, Mo, and Cd) was resided mainly within the accumulation mode, ranged from 1 to 2 μm; (III) Na, V, Co, Ni, and Ga were distributed among fine, intermediate, and coarse modes; and (IV) those which were mainly found within particles larger than 2.7 μm (Al, Mg, Si, Ca, Sc, Tl, Fe, Sr, Zr, and Ba). [H+]cor showed an accumulation mode at 600-700 nm and the role of Ca2 + should be fully considered in the estimation of acidity. The acidity in accumulation mode particles suggested that generally gaseous NH3 was not enough to neutralize sulfate completely. PMF method was applied for source apportionment of elements combined with water soluble ions. Dust, vehicle, aged coal combustion, and sea salt were identified, and the size resolved source apportionments were discussed. Aged coal combustion was the important source of fine particles and

  10. Student Characteristics and Choice of High School Remembrance Role.

    ERIC Educational Resources Information Center

    Holland, Alyce; Andre, Thomas

    1999-01-01

    Investigates variables related to how students choose to be remembered after high school. Reports sports participation, social activity participation, high school academic rank, mother's education, and masculinity were variables associated with four remembrance roles: brilliant student, most popular, athletic star, and leader. Concludes that…

  11. Characteristics of atmospheric particulate mercury in size-fractionated particles during haze days in Shanghai

    NASA Astrophysics Data System (ADS)

    Chen, Xiaojia; Balasubramanian, Rajasekhar; Zhu, Qiongyu; Behera, Sailesh N.; Bo, Dandan; Huang, Xian; Xie, Haiyun; Cheng, Jinping

    2016-04-01

    Atmospheric particulate mercury (PHg) is recognized as a global pollutant that requires regulation because of its significant impacts on both human health and wildlife. The haze episodes that occur frequently in China could influence the transport and fate of PHg. To examine the characteristics of PHg during haze and non-haze days, size-fractioned particles were collected using thirteen-stage Nano-MOUDI samplers (10 nm-18 μm) during a severe haze episode (from December 2013 to January 2014) in Shanghai. The PHg concentration on haze days (4.11 ± 0.53 ng m-3) was three times higher than on non-haze days (1.34 ± 0.15 ng m-3). The ratio of the PHg concentration to total gaseous mercury (TGM) ranged from 0.42 during haze days to 0.21 during non-haze days, which was possibly due to the elevated concentration of particles for gaseous elemental mercury (GEM) adsorption, elevated sulfate and nitrate contributing to GEM oxidation, and the catalytic effect of elevated water-soluble inorganic metal ions. PHg/PM10 during haze days (0.019 ± 0.004 ng/μg) was lower than during non-haze days (0.024 ± 0.002 ng/μg), and PHg/PM10 was significantly reduced with an increasing concentration of PM10, which implied a relatively lower growth velocity of mercury than other compositions on particles during haze days, especially in the diameter range of 0.018-0.032 μm. During haze days, each size-fractioned PHg concentration was higher than the corresponding fraction on non-haze days, and the dominant particle size was in the accumulation mode, with constant accumulation to a particle size of 0.56-1.0 μm. The mass size distribution of PHg was bimodal with peaks at 0.32-0.56 μm and 3.1-6.2 μm on non-haze days, and 0.56-1.0 μm and 3.1-6.2 μm on haze days. There was a clear trend that the dominant size for PHg in the fine modes shifted from 0.32-0.56 μm during non-haze days to 0.56-1.0 μm on haze days, which revealed the higher growth velocity of PHg on haze days due to the

  12. Role of Particle Focusing in Resistive-Pulse Technique: Direction-Dependent Velocity in Micropores.

    PubMed

    Qiu, Yinghua; Vlassiouk, Ivan; Hinkle, Preston; Toimil-Molares, Maria Eugenia; Levine, Alex J; Siwy, Zuzanna S

    2016-03-22

    Passage time through single micropores is an important parameter used to quantify the surface charge and zeta potential of particles. In the resistive-pulse technique, the measured time of pressure- or electric-field-induced translocation is assumed to be direction independent. This assumption is supported by the low velocities of the particles and the supporting fluid such that the transport reversibility known for Stokes flow is expected to apply. In this article, we present examples of micropores in which passage time of ∼400 nm diameter particles becomes direction-dependent; that is, the particles' translocation times from left to right and right to left are different. These pores are characterized by an undulating inner diameter such that at least one wider zone called a cavity separates two narrower regions of different lengths. We propose that the observed direction-dependence of the translocation velocity is caused by an asymmetric efficiency of particle focusing toward the pore axis, which leads to a direction-dependent set of particle trajectories. The reported pores present the simplest system in which time-broken symmetry has been observed. The results are of importance for sensing of particles and molecules by the resistive-pulse technique since pores used for detection are often characterized by finite roughness or noncylindrical shape. This article also points to the role of particle focusing in the magnitude and distribution of the translocation times. PMID:26901283

  13. Entrepreneurial leadership characteristics of SNEs emerge as their role develops.

    PubMed

    Ballein, K M

    1998-01-01

    Adapting to sweeping changes in health care organizations, senior nurse executives (SNEs) are redefining their roles--combining clinical skills, broad management understanding, and inspirational leadership to develop the skill set needed for success in today's unpredictable health care environment. Whether within the traditional organization as senior executives or outside it as individual small business owners, many SNEs are demonstrating creative, entrepreneurial leadership skills. CEOs value these but also emphasize the need for greater business and financial expertise from the SNE. PMID:9505706

  14. Numerical modeling of in-flight characteristics of inconel 625 particles during high-velocity oxy-fuel thermal spraying

    NASA Astrophysics Data System (ADS)

    Gu, S.; McCartney, D. G.; Eastwick, C. N.; Simmons, K.

    2004-06-01

    A computational fluid dynamics (CFD) model is developed to predict particle dynamic behavior in a high-velocity oxyfuel (HVOF) thermal spray gun in which premixed oxygen and propylene are burnt in a combustion chamber linked to a long, parallel-sided nozzle. The particle transport equations are solved in a Lagrangian manner and coupled with the two-dimensional, axisymmetric, steady state, chemically reacting, turbulent gas flow. Within the particle transport model, the total flow of the particle phase is modeled by tracking a small number of particles through the continuum gas flow, and each of these individual particles is tracked independently through the continuous phase. Three different combustion chamber designs were modeled, and the in-flight particle characteristics of Inconel were 625 studied. Results are presented to show the effect of process parameters, such as particle injection speed and location, total gas flow rate, fuel-to-oxygen gas ratio, and particle size on the particle dynamic behavior for a parallel-sided, 12 mm long combustion chamber. The results indicate that the momentum and heat transfer to particles are primarily influenced by total gas flow. The 12 mm long chamber can achieve an optimum performance for Inconel 625 powder particles ranging in diameter from 20 to 40 µm. At a particular spraying distance, an optimal size of particles is observed with respect to particle temperature. The effect of different combustion chamber dimensions on particle dynamics was also investigated. The results obtained for both a 22 mm long chamber and also one with a conical, converging design are compared with the baseline data for the 12 mm chamber.

  15. Turbulent flow characteristics in a randomly packed porous bed based on particle image velocimetry measurements

    NASA Astrophysics Data System (ADS)

    Patil, Vishal A.; Liburdy, James A.

    2013-04-01

    An experimental study was undertaken to better understand the turbulent flow characteristics within a randomly packed porous bed. A relatively low aspect ratio bed (bed width to spherical solid phase particle diameter of 4.67) with the fluid phase refractive index matched to that of the solid phase was used to obtain time resolved particle image velocimetry data. Care was taken to assure that data were outside of the wall affected region, and results are based on detailed time dependent velocity vector maps obtained at selected pores. In particular, four pores were identified that display a range of very disparate mean flow conditions which resemble channel-like flow, impinging flow, recirculating flow, and jet like flow. Velocity data were used for a range of pore Reynolds numbers, Repore, from 418 to 3964 to determine the following turbulence measures: (i) turbulent kinetic energy components, (ii) turbulent shear production rate, (iii) integral Eulerian length and time scales, and (iv) energy spectra. The pore Reynolds number is based on the porous bed hydraulic diameter, DH = ϕDB/(1 - ϕ) where ϕ is bed porosity and DB is solid phase bead diameter and average bed interstitial velocity, Vint = VDarcy/ϕ, where VDarcy = Q/Abed, with Q being the volumetric flow rate and Abed the bed cross section normal to the flow. Results show that when scaled with the bed hydraulic diameter, DH, and average interstitial velocity, Vint, these turbulence measures all collapse for Repore, beyond approximately 2800, except that the integral scales collapse at a lower value near 1300-1800. These results show that the pore turbulence characteristics are remarkably similar from pore to pore and that scaling based on bed averaged variables like DH and Vint characterizes their magnitudes despite very different mean flow conditions.

  16. Characteristics of beryllium exposure to small particles at a beryllium production facility.

    PubMed

    Virji, M Abbas; Stefaniak, Aleksandr B; Day, Gregory A; Stanton, Marcia L; Kent, Michael S; Kreiss, Kathleen; Schuler, Christine R

    2011-01-01

    Epidemiological studies have reported process-specific elevated prevalence of beryllium sensitization (BeS) and chronic beryllium disease (CBD) among workers. However, exposure-response relationships have been inconsistent, possibly due to incomplete characterization of many biologically relevant aspects of exposure, including particle size. In 1999, two surveys were conducted 3-5 months apart at a beryllium metal, oxide, and alloy production facility during which personal impactor samples (n = 198) and personal 37-mm closed-face cassette (CFC) 'total' samples (n = 4026) were collected. Among process areas, median particle mass median aerodynamic diameter ranged from 5 to 14 μm. A large fraction of the beryllium aerosol was in the nonrespirable size range. Respirable beryllium concentrations were among the highest for oxide production [geometric mean (GM) = 2.02 μg m⁻³, geometric standard deviation (GSD) = 1.3] and pebbles plant (GM = 1.05 μg m⁻³, GSD = 2.9), areas historically associated with high risk of BeS and CBD. The relationship between GM 'CFC total' and GM respirable beryllium for jobs varied by process areas; the rank order of the jobs showed high overall consistency (Spearman r = 0.84), but the overall correlation was moderate (Pearson r = 0.43). Total beryllium concentrations varied greatly within and between workers among process areas; within-worker variance was larger than between-worker variance for most processes. A review of exposure characteristics among process areas revealed variation in chemical forms and solubility. Process areas with high risk of BeS and CBD had exposure to both soluble and insoluble forms of beryllium. Consideration of biologically relevant aspects of exposure such as beryllium particle size distribution, chemical form, and solubility will likely improve exposure assessment. PMID:20805261

  17. Chemical characteristics of fine particles emitted from different gas cooking methods

    NASA Astrophysics Data System (ADS)

    See, Siao Wei; Balasubramanian, Rajasekhar

    Gas cooking is an important indoor source of fine particles (PM 2.5). The chemical characteristics of PM 2.5 emitted from different cooking methods, namely, steaming, boiling, stir-frying, pan-frying and deep-frying were investigated in a domestic kitchen. Controlled experiments were conducted to measure the mass concentration of PM 2.5 and its chemical constituents (elemental carbon (EC), organic carbon (OC), polycyclic aromatic hydrocarbons (PAHs), metals and ions) arising from these five cooking methods. To investigate the difference in particle properties of different cooking emissions, the amount and type of food, and the heat setting on the gas stove were kept constant during the entire course of the experiments. Results showed that deep-frying gave rise to the largest amount of PM 2.5 and most chemical components, followed by pan-frying, stir-frying, boiling, and steaming. Oil-based cooking methods released more organic pollutants (OC, PAHs, and organic ions) and metals, while water-based cooking methods accounted for more water-soluble (WS) ions. Their source profiles are also presented and discussed.

  18. Identification of characteristic mass spectrometric markers for primary biological aerosol particles and comparison with field data from submicron pristine aerosol particles

    NASA Astrophysics Data System (ADS)

    Freutel, F.; Schneider, J.; Zorn, S. R.; Drewnick, F.; Borrmann, S.; Hoffmann, T.; Martin, S. T.

    2009-04-01

    The contribution of primary biological aerosol (PBA) to the total aerosol particle concentration is estimated to range between 25 and 80%, depending on location and season. Especially in the tropical rain forest it is expected that PBA is a major source of particles in the supermicron range, and is also an important fraction of the submicron aerosol. PBA particles like plant fragments, pollen, spores, fungi, viruses etc. contain chemical compounds as proteins, sugars, amino acids, chlorophyll, and cellular material as cellulose. For this reason we have performed mass spectrometric laboratory measurements (Aerodyne C-ToF and W-ToF AMS, single particle laser ablation instrument SPLAT) on pure submicron aerosol particles containing typical PBA compounds in order to identify typical mass spectral patterns of these compounds and to explain the observed fragmentation patterns on the basis of molecular structures. These laboratory data were compared to submicron particle mass spectra obtained during AMAZE-08 (Amazonian Aerosol CharacteriZation Experiment, Brazil, February/March 2008). The results indicate that characteristic m/z ratios for carbohydrates (e.g., glucose, saccharose, levoglucosan, mannitol) can be identified, for example m/z = 60(C2H4O2+) or m/z = 61(C2H5O2+). Certain characteristic peaks for amino acids were also identified in the laboratory experiments. In the field data from AMAZE-08, these characteristic peaks for carbohydrates and amino acids were found, and their contribution to the total organic mass was estimated to about 5%. Fragment ions from peptides and small proteins were also identified in laboratory experiments. Larger proteins, however, seem to become oxidized to CO2+ to a large extend in the vaporizing process of the AMS. Thus, detection of proteins in atmospheric aerosol particles with the AMS appears to be difficult.

  19. Particle-In-Cell Simulation on the Characteristics of a Receiving Antenna in Space Plasma Environment

    SciTech Connect

    Miyake, Yohei; Usui, Hideyuki; Kojima, Hirotsugu; Omura, Yoshiharu

    2008-12-31

    We applied the electromagnetic Particle-In-Cell simulation to the analysis of receiving antenna characteristics in space plasma environment. In the analysis, we set up external waves in a simulation region and receive them with a numerical antenna model placed in the simulation region. Using this method, we evaluated the effective length of electric field antennas used for plasma wave investigations conducted by scientific spacecraft. We particularly focused on the effective length of an electric field instrument called MEFISTO for a future mission to Mercury: BepiColombo. We first confirmed that the effective length of the MEFISTO-type antenna is basically longer than that of a simple dipole antenna for both electrostatic and electromagnetic plasma waves. By applying the principle of a voltmeter, the effective length of the MEFISTO-type antenna is predicted to become identical to the separation between two sensor-conductor's midpoints. However, the numerical result revealed that the actual effective length becomes shorter than the prediction, which is caused by the shorting-out effect due to the presence of a center boom conductor between the two sensor conductors. Since the above effect is difficult to treat theoretically, the present numerical method is a powerful tool for further quantitative evaluation of the antenna characteristics.

  20. IN VITRO CARDIOTOXICITY OF AIR POLLUTION PARTICLES: ROLE OF BIOAVAILABLE CONSTITUENTS, OXIDATIVE STRESS AND TYROSINE PHOSPHORYLATION

    EPA Science Inventory

    IN VITRO CARDIOTOXICITY OF AIR POLLUTION PARTICLES: ROLE OF BIOAVAILABLE CONSTITUENTS, OXIDATIVE STRESS AND TYROSINE PHOSPHORYLATION.

    T. L. Knuckles1 R. Jaskot2, J. Richards2, and K.Dreher2.
    1Department of Molecular and Biomedical Sciences, College of Veterinary Medicin...

  1. Development of Spectral and Atomic Models for Diagnosing Energetic Particle Characteristics in Fast Ignition Experiments

    SciTech Connect

    MacFarlane, Joseph J

    2009-08-07

    This Final Report summarizes work performed under DOE STTR Phase II Grant No. DE-FG02-05ER86258 during the project period from August 2006 to August 2009. The project, “Development of Spectral and Atomic Models for Diagnosing Energetic Particle Characteristics in Fast Ignition Experiments,” was led by Prism Computational Sciences (Madison, WI), and involved collaboration with subcontractors University of Nevada-Reno and Voss Scientific (Albuquerque, NM). In this project, we have: Developed and implemented a multi-dimensional, multi-frequency radiation transport model in the LSP hybrid fluid-PIC (particle-in-cell) code [1,2]. Updated the LSP code to support the use of accurate equation-of-state (EOS) tables generated by Prism’s PROPACEOS [3] code to compute more accurate temperatures in high energy density physics (HEDP) plasmas. Updated LSP to support the use of Prism’s multi-frequency opacity tables. Generated equation of state and opacity data for LSP simulations for several materials being used in plasma jet experimental studies. Developed and implemented parallel processing techniques for the radiation physics algorithms in LSP. Benchmarked the new radiation transport and radiation physics algorithms in LSP and compared simulation results with analytic solutions and results from numerical radiation-hydrodynamics calculations. Performed simulations using Prism radiation physics codes to address issues related to radiative cooling and ionization dynamics in plasma jet experiments. Performed simulations to study the effects of radiation transport and radiation losses due to electrode contaminants in plasma jet experiments. Updated the LSP code to generate output using NetCDF to provide a better, more flexible interface to SPECT3D [4] in order to post-process LSP output. Updated the SPECT3D code to better support the post-processing of large-scale 2-D and 3-D datasets generated by simulation codes such as LSP. Updated atomic physics modeling to provide for

  2. Particle Morphology Effects on Flow Characteristics of PS304 Plasma Spray Coating Feedstock Powder Blend

    NASA Technical Reports Server (NTRS)

    Stanford, Malcolm K.; DellaCorte, Christopher; Eylon, Daniel

    2002-01-01

    The effects of BaF2-CaF 2 particle morphology on PS304 feedstock powder flow ability have been investigated. BaF2-CaF2 eutectic powders were fabricated by comminution (angular) and by gas atomization (spherical). The fluoride powders were added incrementally to the other powder constituents of the PS304 feedstock: nichrome, chromia, and silver powders. A linear relationship between flow time and concentration of BaF2-CaF2 powder was found. Flow of the powder blend with spherical BaF2-CaF2 was better than the angular BaF2-CaF2. Flow ability of the powder blend with angular fluorides decreased linearly with increasing fluoride concentration. Flow of the powder blend with spherical fluorides was independent of fluoride concentration. Results suggest that for this material blend, particle morphology plays a significant role in powder blend flow behavior, offering potential methods to improve powder flow ability and enhance the commercial potential. These findings may have applicability to other difficult-to-flow powders such as cohesive ceramics.

  3. Particle-In-Cell Simulations on Electric Field Antenna Characteristics in the Spacecraft Environment

    NASA Astrophysics Data System (ADS)

    Miyake, Y.; Usui, H.; Kojima, H.; Omura, Y.; Matsumoto, H.

    2006-12-01

    The Solar Terrestrial Physics (STP) group in Japan has organized a new magnetospheric mission named SCOPE whose objective is to investigate the scale-coupling process of plasma dynamics in the Terrestrial magnetosphere. For the sophisticated electric field measurements planned in the SCOPE mission, we have to investigate the antenna characteristics which are essential for the precise calibration of observed data. Particularly, (1) realistic antenna geometries including spacecraft body and (2) inhomogeneous plasma environment created by plasma-spacecraft interactions should be taken into consideration in the antenna analysis for application to the scientific mission. However, the analysis of the antenna impedance is very complex because the plasma is a dispersive and anisotropic medium, and thus it is too difficult to consider the realistic plasma environment near the spacecraft by the theoretical approaches. In the present study, we apply the Particle-In-Cell simulations to the antenna analysis, which enables us to treat the antenna model including a spacecraft body and analyze the effects of photoelectron emission on antenna characteristics. The present antenna model consists of perfect conducting antennas and spacecraft body, and the photoelectron emission from the sunlit surfaces is also modeled. Using these models, we first performed the electrostatic simulations and examined the photoelectron environment around the spacecraft. Next, the antenna impedance under the obtained photoelectron environment was examined by the electromagnetic simulations. Impedance values obtained in photoelectron environment were much different from those in free space, and they were analogous to the impedance characteristics of an equivalent electric circuit consisting of a resistance and capacitance connected in parallel. The validity of the obtained values has been examined by the comparison with the measurements by the scientific spacecraft.

  4. Role of radiation reaction forces in the dynamics of centrifugally accelerated particles

    SciTech Connect

    Dalakishvili, G. T.; Rogava, A. D.; Berezhiani, V. I.

    2007-08-15

    In this paper we study the influence of radiation reaction (RR) forces on the dynamics of centrifugally accelerated particles. It is assumed that the particles move along magnetic field lines anchored in the rotating central object. The common 'bead-on-the-wire' approximation is used. The solutions are found and analyzed for cases when the form of the prescribed trajectory (rigidly rotating field line) is approximated by: (a) straight line, and (b) Archimedes spiral. Dynamics of neutral and charged particles are compared with the emphasis on the role of RR forces in the latter case. It is shown that for charged particles there exist locations of stable equilibrium. It is demonstrated that for particular initial conditions RR forces cause centripetal motion of the particles: their 'falling' on the central rotating object. It is found that in the case of Archimedes spiral both neutral and charged particles can reach infinity where their motion has asymptotically force-free character. The possible importance of these processes for the acceleration of relativistic, charged particles by rotating magnetospheres in the context of the generation of nonthermal, high-energy emission of AGN and pulsars is discussed.

  5. Role of radiation reaction forces in the dynamics of centrifugally accelerated particles

    NASA Astrophysics Data System (ADS)

    Dalakishvili, G. T.; Rogava, A. D.; Berezhiani, V. I.

    2007-08-01

    In this paper we study the influence of radiation reaction (RR) forces on the dynamics of centrifugally accelerated particles. It is assumed that the particles move along magnetic field lines anchored in the rotating central object. The common “bead-on-the-wire” approximation is used. The solutions are found and analyzed for cases when the form of the prescribed trajectory (rigidly rotating field line) is approximated by: (a) straight line, and (b) Archimedes spiral. Dynamics of neutral and charged particles are compared with the emphasis on the role of RR forces in the latter case. It is shown that for charged particles there exist locations of stable equilibrium. It is demonstrated that for particular initial conditions RR forces cause centripetal motion of the particles: their “falling” on the central rotating object. It is found that in the case of Archimedes spiral both neutral and charged particles can reach infinity where their motion has asymptotically force-free character. The possible importance of these processes for the acceleration of relativistic, charged particles by rotating magnetospheres in the context of the generation of nonthermal, high-energy emission of AGN and pulsars is discussed.

  6. Particle therapy

    SciTech Connect

    Raju, M.R.

    1993-09-01

    Particle therapy has a long history. The experimentation with particles for their therapeutic application got started soon after they were produced in the laboratory. Physicists played a major role in proposing the potential applications in radiotherapy as well as in the development of particle therapy. A brief review of the current status of particle radiotherapy with some historical perspective is presented and specific contributions made by physicists will be pointed out wherever appropriate. The rationale of using particles in cancer treatment is to reduce the treatment volume to the target volume by using precise dose distributions in three dimensions by using particles such as protons and to improve the differential effects on tumors compared to normal tissues by using high-LET radiations such as neutrons. Pions and heavy ions combine the above two characteristics.

  7. The role of unsteady forces for sediment particles in bedload transport

    NASA Astrophysics Data System (ADS)

    Liu, Detian; Liu, Xiaofeng; Fu, Xudong

    2016-04-01

    In engineering, bedload transport is usually predicted by a variety of formulas, and huge uncertainty is found from case to case. One of the fundamental reasons is the lack of fully understanding the dynamic behavior of bedload particles. We explore the dynamic characteristics of sediment particles transported in turbulent open-channel flows. A numerical model of sediment transport is built by combining the large eddy simulation (LES) with discrete element model (DEM) using a fully four-way coupling method. Particular attention is paid to the hydrodynamic forces acting on bedload particles. The result shows that, in addition to drag force, the unsteady forces (i.e. Basset history force and added mass force) are important (40%~60% in the summation of all the time-averaged magnitude of forces) for fine sediment particles (with a diameter of 0.5 mm), which are usually ignored for computational complexity. While the lift force has been found to be significant for gravel particles (with a diameter of 31 mm)[1], it is not relatively dominant for such fine particles (less than 3% in the summation). This helps explaining why the prediction of the same formula change greatly from case to case. The comparison with experimental data also shows great potential of the current LES-DEM model for fundamental research in bedload transport. Reference: [1] Nino, Y., & Garcia, M. (1994). Gravel saltation 2. Modeling. Water Resources Research, 30(6), 1915-1924.

  8. A possible role for rat intestinal surfactant-like particles in transepithelial triacylglycerol transport.

    PubMed Central

    Mahmood, A; Yamagishi, F; Eliakim, R; DeSchryver-Kecskemeti, K; Gramlich, T L; Alpers, D H

    1994-01-01

    To further examine whether surfactant-like particles (DeSchryver-Kecskemeti, K., R. Eliakim, S. Carroll, W. F. Stenson, M. A. Moxley, and D. H. Alpers. 1989. J. Clin. Invest. 84:1355-1361) were involved in the transepithelial transport of lipid, alkaline phosphatase activity and surfactant-like particle content were measured in apical mucosal scrapings, enterocytes, lamina propria, and serum after inhibition of chylomicron transport. Serum triacylglycerol levels were decreased 60-76% by Pluronic L-81, fenfluramine, and choline deficiency compared with fat-fed controls. 5 h after triacylglycerol feed, alkaline phosphatase activity in all three experimental groups was decreased compared with controls by 52-69% in mucosal scrapings and by 33-72% in serum. A parallel decline (60%) in alkaline phosphatase activity occurred in the lamina propria of Pluronic-treated animals. Total particle content (measured by an ELISA using antiserum against purified particle) after Pluronic treatment was decreased in mucosal scrapings, lamina propria, and serum by 16, 22, and 29% at 3 h and by 33, 40, and 8%, respectively, at 5 h after fat feeding. In contrast, particle content was increased in enterocytes by 29% 3 h and by 8% 5 h after fat feeding. By electron microscopy, enterocytes from Pluronic- and fenfluramine-treated animals exhibited a two- to threefold increase in large intracellular cytoplasmic lipid globules and the appearance of lamellae in apposition, with a marked decrease in the number of surfactant-like particles overlying the brush border. These changes, produced by inhibition of chylomicron transport, in the distribution of surfactant-like particles and particle-bound alkaline phosphatase are consistent with a role for these particles in transepithelial triacylglycerol transport across and out of the enterocyte. Images PMID:8282824

  9. The roles of organics in New particle formation in the Megacity of Beijing, China

    NASA Astrophysics Data System (ADS)

    Hu, Min; Wang, Zhibin; Wu, Zhijun; Yue, Dingli; Zheng, Jun; Zhang, Renyi; Boy, Michael; Wiedensohler, Alfred

    2013-04-01

    The new particle formation (NPF) has been investigated in the high aerosol loading environment of Beijing since March 2004. The occurrence frequency is comparable with less aerosol loading environment, whereas the monthly or seasonal variations indicate location dependency. Simultaneously measurements of gaseous precursors of H2SO4 vapor and ammonia proved that the H2SO4-NH3-H2O ternary nucleation is an important mechanism for Beijing NPF, which is mainly constrained by the concentrations of the gaseous sulfuric acid and total particle surface area. The higher particle formation rates were observed on high aerosol loading days, followed up NPF, then high organic matter observed by AMS, which indicated the organic vapors should be involved in the new particle formation process. The roles of organics in the formation and growth of the NPF were focused on in the case of summer 2008, Olympic Games period, the particle formation rates show good correlations with sulfuric acid and organic vapors implying that both play an important role in the atmospheric new particle formation. The best fit between observed and modelled particle formation rates is achieved with the homogenous nucleation theory of sulfuric acid (both homomolecularly and hetermolecularly) with separate coefficients in J = KSA1[H2SO4]2 + KSA2[H2SO4][Org], in which the contributions of the sulfuric acid and the organics involving terms have been estimated as 43% and 57%, respectively. The growth of new particles contributed by condensation and neutralization of sulfuric acid, coagulation as well as organic compounds involved growth are discussed. The apparent growth rates vary from 3 to 11 nm h-1. Condensation of sulfuric acid and its subsequent neutralization by ammonia and coagulation contribute to the apparent particle growth on average 45±18% and 34±17%, respectively. The 30% higher concentration of sulfate than organic compounds in particles during the sulfur-rich NPF events but 20% lower

  10. The Characteristics, Roles and Functions of Institutional Research Professionals in the Southern Association for Institutional Research.

    ERIC Educational Resources Information Center

    Harrington, Charles; Chen, HongYu

    A study was done on the variation in characteristics, roles, and functions of institutional research professionals affiliated with the Southern Association for Institutional Research (SAIR). The study examined professional role identity, location of offices in the organizational hierarchy, breadth of institutional research activities undertaken,…

  11. Sex Role, Self-Esteem, and Leadership Characteristics of Male and Female Teachers and Administrators.

    ERIC Educational Resources Information Center

    Barrett, Diane L.; Bieger, George R.

    The incongruity between the stereotypical female role and the leader role accounts for the scarcity of female administrators in the United States. The solution seems to be androgyny, or the mixing of masculine and feminine characteristics. A recent survey sampled 28 male teachers, 25 female teachers, 27 male administrators, and 22 female…

  12. Flow Scales of Influence on the Settling Velocities of Particles with Varying Characteristics.

    PubMed

    Jacobs, Corrine N; Merchant, Wilmot; Jendrassak, Marek; Limpasuvan, Varavut; Gurka, Roi; Hackett, Erin E

    2016-01-01

    The settling velocities of natural, synthetic, and industrial particles were measured in a grid turbulence facility using optical measurement techniques. Particle image velocimetry and 2D particle tracking were used to measure the instantaneous velocities of the flow and the particles' trajectories simultaneously. We find that for particles examined in this study (Rep = 0.4-123), settling velocity is either enhanced or unchanged relative to stagnant flow for the range of investigated turbulence conditions. The smallest particles' normalized settling velocities exhibited the most consistent trends when plotted versus the Kolmogorov-based Stokes numbers suggesting that the dissipative scales influence their dynamics. In contrast, the mid-sized particles were better characterized with a Stokes number based on the integral time scale. The largest particles were largely unaffected by the flow conditions. Using proper orthogonal decomposition (POD), the flow pattern scales are compared to particle trajectory curvature to complement results obtained through dimensional analysis using Stokes numbers. The smallest particles are found to have trajectories with curvatures of similar scale as the small flow scales (higher POD modes) whilst mid-sized particle trajectories had curvatures that were similar to the larger flow patterns (lower POD modes). The curvature trajectories of the largest particles did not correspond to any particular flow pattern scale suggesting that their trajectories were more random. These results provide experimental evidence of the "fast tracking" theory of settling velocity enhancement in turbulence and demonstrate that particles align themselves with flow scales in proportion to their size. PMID:27513958

  13. Characteristics of atmospheric particles over urban city Osaka occasionally covered with photochemical smog

    NASA Astrophysics Data System (ADS)

    Sano, Itaru

    The photochemical smog events, which are affected by transported air pollutants, become to be more frequent and heavier in Japan. Thereby the photochemical smog is observed not only at urban areas but also at remote islands. The long range transported pollutant influences on the local atmospheric condition mixed with the locally emitted gases and particulates. It is known that intensive solar radiation in summer seasons changes the nitrogen oxide gases into oxidant through photochemical processes. This work intends to investigate what are the aerosol characteristics in photochemical smog events at Osaka. Osaka is a part of Kansai industrial area, which is the second megalopolis in Japan and surrounded by the backside mountains. Therefore lots of anthropogenic emissions often remain in the atmosphere over the cities. The radiometric observations with Cimel CE-318 sun/sky and the measurements of PM1, PM2.5 and PM10 mass concentration at Kinki University in Osaka provide us with effective information of atmospheric particles. The other in-situ measurements such as SOx, NOx, Ox, HC and weather conditions taken by local governmental office are available for analysis of photochemical smog events. Further a backward trajectory based on NOAA HYSPLIT looks promising to help us with our comprehensive investigation of long range transported pollutants.

  14. Radiological characteristics of charged particle interactions in the first clay-nanoparticle dichromate gel dosimeter

    NASA Astrophysics Data System (ADS)

    Taylor, M. L.; Maeyama, T.; Fukunishi, N.; Ishikawa, K. L.; Fukasaku, K.; Furuta, T.; Takagi, S.; Noda, S.; Himeno, R.; Fukuda, S.

    2013-06-01

    The incorporation of clay nanoparticles into gel dosimeters shows promise for significant diffusion reduction - but to what extent does the presence of the nano-clay influence charged particle interactions and, in particular, what is the impact on water equivalence? In this work, we quantify the radiological characteristics of electron, proton and carbon ion interactions in the RIKEN dichromate nanoclay gel and specifically evaluate the water equivalence over a broad energy range. Results indicate that the radiological properties are sufficiently representative of tissues that this low-diffusion gel could readily be used for validation of complex dose distributions. Electron and proton ranges are within 1 % of those in water. Mean effective atomic numbers for electron interactions in the range 10 keV - 10 GeV are within 1 % of those of water which, coupled with the similar mass density, ultimately means the overall impact on dose distributions is not great. The range of C6+ ions in the nanoclay gel is closer to that of water (< 4 %) than a common polymer gel dosimeter (< 7 %), though experimentally measured R1 values indicate an over-response at low doses.

  15. SETTLING AND COAGULATION CHARACTERISTICS OF FLUORESCENT PARTICLES DETERMINED BY FLOW CYTOMETRY AND FLUOROMETRY

    EPA Science Inventory

    A new technique for detecting particles in natural waters relies upon analysis of fluorescent emission by flow cytometry. luorescent pigment particles ranging in radius from 0.1 to 5 um are available in sufficient quantity to be useful as model particles. aboratory coagulation an...

  16. Experimental Analysis of Damping and Tribological Characteristics of Nano-CuO Particle Mixed Lubricant in Ball Bearings

    NASA Astrophysics Data System (ADS)

    Prakash, E.; Sivakumar, K.

    2015-12-01

    Experimental analysis of damping capacity and tribological characteristics of nano CuO added Servosystem 68 lubricant is attempted. CuO nano particles were synthesized by aqueous precipitation method and characterized. Prior to dispersion into lubricant, CuO nano particles were coated with 0.2 wt.% surfactant (Span-80) to stabilize the nano fluid. Tribological characteristics of particle added lubricant were tested in ASTM D 4172 four ball wear tester. Scanning electron microscopy test results of worn surfaces of nano CuO particle added lubricant were smoother than base lubricant. The particle added lubricant was applied in a new ball bearing and three defected ball bearings. When particle added lubricant was used, the ball defected bearing's vibration amplitude was reduced by 21.94% whereas it was 16.46% for new bearing and was ≤ 11% for other defected bearings. The formation of protection film of CuO over ball surface and regime of full film lubrication near the ball zone were observed to be reason for improved damping of vibrations.

  17. Surfactant effect on functionalized carbon nanotube coated snowman-like particles and their electro-responsive characteristics

    SciTech Connect

    Zhang, Ke; Liu, Ying Dan; Choi, Hyoung Jin

    2012-10-15

    The core–shell structured snowman-like (SL) microparticles coated by functionalized multi-walled carbon nanotube (MWNT) were prepared in the presence of different surfactants including cationic surfactant-cetyl trimethylammonium bromide (CTAB) and anionic surfactant-sodium lauryl sulfate (SDS). The effect of surfactants on adsorption onto SL particles was characterized by scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and conductivity. The cationic surfactant is found to be more effective than anionic surfactant for helping nanotube adsorbed onto microparticle due to the presence of electrostatic interaction between the functionalized MWNT and the surfactant. Furthermore, the MWNT/SL particles dispersed in silicone oil exhibited a typical fibril structure of the electrorheological characteristics under an applied electric field observed by an optical microscope (OM), in which the state of nanotubes wrapped on the particles strongly affects their electro-responsive characteristics.

  18. Characteristics of exhaled particle production in healthy volunteers: possible implications for infectious disease transmission

    PubMed Central

    Wurie, Fatima

    2013-01-01

    The size and concentration of exhaled particles may influence respiratory infection transmission risk. We assessed variation in exhaled particle production between individuals, factors associated with high production and stability over time. We measured exhaled particle production during tidal breathing in a sample of 79 healthy volunteers, using optical particle counter technology. Repeat measurements (several months after baseline) were obtained for 37 of the 79 participants.   Multilevel linear regression models of log transformed particle production measures were used to assess risk factors for high production.  Stability between measurements over time was assessed using Lin’s correlation coefficients. Ninety-nine percent of expired particles were <1μm in diameter. Considerable variation in exhaled particle production was observed between individuals and within individuals over time. Distribution of particle production was right skewed.  Approximately 90% of individuals produce <150 particles per litre in normal breathing.  A few individuals had measurements of over 1000 particles per litre (maximum 1456). Particle production increased with age (p<0.001) and was associated with high tree pollen counts. Particle production levels did not remain stable over time [rho 0.14 (95%CI -0.10, 0.38, p=0.238)]. Sub-micron particles conducive to airborne rather than droplet transmission form the great majority of exhaled particles in tidal breathing. There is a high level of variability between subjects but measurements are not stable over time. Production increases with age and may be influenced by airway inflammation caused by environmental irritants. Further research is needed to determine whether the observed variations in exhaled particle production affect transmission of respiratory infection. PMID:24555026

  19. MYOCARDIAL INJURY FROM INHALED COMBUSTION PARTICLES: IS THERE A ROLE FOR ZINC?

    EPA Science Inventory

    Myocardial injury from inhaled combustion particles: Is there a role for zinc?
    U.P.Kodavanti, PhD 1, C.F.Moyer, PhD, DVM 2, A.D.Ledbetter, BS 1, M.C.Schladweiler, BS
    1, P.S.Gilmour, PhD 1, R.Hauser, ScD, MPH 3, D.C.Christiani, MPH, MS 3, D.L.Costa, ScD
    1 and A.Ny...

  20. Flow Scales of Influence on the Settling Velocities of Particles with Varying Characteristics

    PubMed Central

    Jacobs, Corrine N.; Merchant, Wilmot; Jendrassak, Marek; Limpasuvan, Varavut; Gurka, Roi; Hackett, Erin E.

    2016-01-01

    The settling velocities of natural, synthetic, and industrial particles were measured in a grid turbulence facility using optical measurement techniques. Particle image velocimetry and 2D particle tracking were used to measure the instantaneous velocities of the flow and the particles’ trajectories simultaneously. We find that for particles examined in this study (Rep = 0.4–123), settling velocity is either enhanced or unchanged relative to stagnant flow for the range of investigated turbulence conditions. The smallest particles’ normalized settling velocities exhibited the most consistent trends when plotted versus the Kolmogorov-based Stokes numbers suggesting that the dissipative scales influence their dynamics. In contrast, the mid-sized particles were better characterized with a Stokes number based on the integral time scale. The largest particles were largely unaffected by the flow conditions. Using proper orthogonal decomposition (POD), the flow pattern scales are compared to particle trajectory curvature to complement results obtained through dimensional analysis using Stokes numbers. The smallest particles are found to have trajectories with curvatures of similar scale as the small flow scales (higher POD modes) whilst mid-sized particle trajectories had curvatures that were similar to the larger flow patterns (lower POD modes). The curvature trajectories of the largest particles did not correspond to any particular flow pattern scale suggesting that their trajectories were more random. These results provide experimental evidence of the “fast tracking” theory of settling velocity enhancement in turbulence and demonstrate that particles align themselves with flow scales in proportion to their size. PMID:27513958

  1. Physical and Optical/Radiative Characteristics of Small Particles in Tropical Cirrus

    NASA Technical Reports Server (NTRS)

    Pueschel, R. F.; Ferry, G. V.; Strawa, Anthony W.; Allen, D. A.; Howard, S. D.; Foster, T. C.; Hallett, J.; Arnott, W. P.

    1995-01-01

    Whether cirrus clouds heat or cool the Earth-atmosphere system depends on the relative importance of the cloud shortwave albedo effect and the cloud thermal greenhouse effect. Both an determined by the distribution of ice condensate with cloud particle size. The microphysics instrument package flown aboard the DC-8 In TOGA/COARE included an ice crystal replicator, a 2D Greyscale Cloud Particle Probe and a Forward Scattering Spectrometer Aerosol Probe. In combination. these instruments permitted particle size measurements between 0.5 micrometers and 2.6 mm diameter. Ice crystal replicas were used to validate signals from the electro-optical instruments. Typical results show a prevalence in tropical cirrus clouds of micron-sized particles, in addition to cloud particles that exceed 100 micrometer radius. The mechanism of their formation is growth of (hygroscopic, possibly ocean-derived) aerosol particles along the Kohler curves. The concentration of small particles is higher and less variable in space and time, and their tropospheric residence time is longer, than those of large cloud particles because of lower sedimentation velocities. Small particles shift effective cloud particle radii to sizes much smaller than the mean diameter of the cloud particles. This causes an increase in shortwave reflectivity and IR emissivity. and a decrease in transmissivity. In the cirrus outflow of tropical cyclone Oliver on 8 February, 1993, the reflectivity increases with altitude (decreasing temperature) stronger than does cloud emissivity, yielding enhanced radiative cooling at higher altitudes.

  2. The role of the Azores Archipelago in capturing and retaining incoming particles

    NASA Astrophysics Data System (ADS)

    Sala, Iria; Harrison, Cheryl S.; Caldeira, Rui M. A.

    2016-02-01

    The capacity of the Azores Archipelago to capture and retain incoming particles and organisms that are drifting with the oceanic currents was the main focus of this study. Using the Hybrid Coordinate Ocean Model coupled with the Connectivity Modeling System (an offline Lagrangian tool) a series of experiments were conducted to determine: i) the origin of the particles that reach the archipelago, ii) the capacity of each island sub-group to retain incoming particles and organisms, as well as the iii) oceanographic phenomena that lead to their transport and retention. The Gulf Stream (GS) and the westward propagating eddy corridors were identified as the main transport pathways affecting the Azores region. Eddy Kinetic Energy from altimetry data and Lyapunov exponent analysis suggest that eddies and filaments are the main delivery mechanisms. In the upper mixed layer, the GS and its associated eddies are a predominant regional oceanographic feature injecting particles from the north and west boundaries toward the Azores. The capacity to capture particles of each island sub-group was directly proportional to their size, while the retention time within the Azores region increased with depth, associated with the decrease in velocity of the intermediate water currents. This study opens new prospects to understand transport in the Mid-Atlantic (Azores) region and the islands' role in marine colonization, dispersal, fisheries recruitment and speciation.

  3. Microbiology and atmospheric processes: the role of biological particles in cloud physics

    NASA Astrophysics Data System (ADS)

    Möhler, O.; Demott, P. J.; Vali, G.; Levin, Z.

    2007-12-01

    As part of a series of papers on the sources, distribution and potential impact of biological particles in the atmosphere, this paper introduces and summarizes the potential role of biological particles in atmospheric clouds. Biological particles like bacteria or pollen may be active as both cloud condensation nuclei (CCN) and heterogeneous ice nuclei (IN) and thereby can contribute to the initial cloud formation stages and the development of precipitation through giant CCN and IN processes. The paper gives an introduction to aerosol-cloud processes involving CCN and IN in general and provides a short summary of previous laboratory, field and modelling work which investigated the CCN and IN activity of bacterial cells and pollen. Recent measurements of atmospheric ice nuclei with a continuous flow diffusion chamber (CFDC) and of the heterogeneous ice nucleation efficiency of bacterial cells are also briefly discussed. As a main result of this overview paper we conclude that a proper assessment of the impact of biological particles on tropospheric clouds needs new laboratory, field and modelling work on the abundance of biological particles in the atmosphere and their CCN and heterogeneous IN properties.

  4. Microbiology and atmospheric processes: the role of biological particles in cloud physics

    NASA Astrophysics Data System (ADS)

    Möhler, O.; Demott, P. J.; Vali, G.; Levin, Z.

    2007-08-01

    As part of a series of papers on the sources, distribution and potential impact of biological particles in the atmosphere, this paper introduces and summarizes the potential role of biological particles in atmospheric clouds. Biological particles like bacteria or pollen may be active as both cloud condensation nuclei (CCN) and heterogeneous ice nuclei (IN) and thereby can contribute to the initial cloud formation stages and the development of precipitation through giant CCN and IN processes. The paper gives an introduction to aerosol-cloud processes like CCN and IN in general and provides a short summary of previous laboratory, field and modelling work investigating the CCN and IN activity of bacterial cells and pollen. Recent measurements of atmospheric ice nuclei with a continuous flow diffusion chamber (CFDC) and of the heterogeneous ice nucleation efficiency of bacterial cells are also briefly discussed. As a main result of this overview paper we conclude that a proper assessment of the impact of biological particles on tropospheric clouds needs new laboratory, field and modelling work investigating the abundance of biological particles in the atmosphere and their CCN and heterogeneous IN properties.

  5. Dissolution kinetics of sub-millimeter Composition B detonation residues: role of particle size and particle wetting.

    PubMed

    Fuller, Mark E; Schaefer, Charles E; Andaya, Christina; Lazouskaya, Volha; Fallis, Steve; Wang, Chao; Jin, Yan

    2012-07-01

    The dissolution of the 2,4,6-trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) from microscale particles (<250μm) of the explosive formulation Composition B was examined and compared to dissolution from macroscopic particles (>0.5mm). The dissolution of explosives from detonation soot was also examined. The measured mass transfer coefficients for the microscale particles were one to two orders of magnitude greater than the macroscopic particles. When normalized to particle surface area, mass transfer coefficients of microscale and macroscale particles were similar, indicating that the bulk dissolution processes were similar throughout the examined size range. However, an inverse relationship was observed between the particle diameter and the RDX:TNT mass transfer rate coefficient ratio for dry-attritted particles, which suggests that RDX may be more readily dissolved (relative to TNT) in microscale particles compared to macroscale particles. Aqueous weathering of larger Composition B residues generated particles that possessed mass transfer coefficients that were on the order of 5- to 20-fold higher than dry-attritted particles of all sizes, even when normalized to particle surface area. These aqueous weathered particles also possessed a fourfold lower absolute zeta-potential than dry-attritted particles, which is indicative that they were less hydrophobic (and hence, more wettable) than dry-attritted particles. The increased wettability of these particles provides a plausible explanation for the observed enhanced dissolution. The wetting history and the processes by which particles are produced (e.g., dry physical attrition vs. aqueous weathering) of Composition B residues should be considered when calculating mass transfer rates for fate and transport modeling. PMID:22483856

  6. The role of low-volatility organic compounds in initial particle growth in the atmosphere

    NASA Astrophysics Data System (ADS)

    Tröstl, Jasmin; Chuang, Wayne K.; Gordon, Hamish; Heinritzi, Martin; Yan, Chao; Molteni, Ugo; Ahlm, Lars; Frege, Carla; Bianchi, Federico; Wagner, Robert; Simon, Mario; Lehtipalo, Katrianne; Williamson, Christina; Craven, Jill S.; Duplissy, Jonathan; Adamov, Alexey; Almeida, Joao; Bernhammer, Anne-Kathrin; Breitenlechner, Martin; Brilke, Sophia; Dias, Antònio; Ehrhart, Sebastian; Flagan, Richard C.; Franchin, Alessandro; Fuchs, Claudia; Guida, Roberto; Gysel, Martin; Hansel, Armin; Hoyle, Christopher R.; Jokinen, Tuija; Junninen, Heikki; Kangasluoma, Juha; Keskinen, Helmi; Kim, Jaeseok; Krapf, Manuel; Kürten, Andreas; Laaksonen, Ari; Lawler, Michael; Leiminger, Markus; Mathot, Serge; Möhler, Ottmar; Nieminen, Tuomo; Onnela, Antti; Petäjä, Tuukka; Piel, Felix M.; Miettinen, Pasi; Rissanen, Matti P.; Rondo, Linda; Sarnela, Nina; Schobesberger, Siegfried; Sengupta, Kamalika; Sipilä, Mikko; Smith, James N.; Steiner, Gerhard; Tomè, Antònio; Virtanen, Annele; Wagner, Andrea C.; Weingartner, Ernest; Wimmer, Daniela; Winkler, Paul M.; Ye, Penglin; Carslaw, Kenneth S.; Curtius, Joachim; Dommen, Josef; Kirkby, Jasper; Kulmala, Markku; Riipinen, Ilona; Worsnop, Douglas R.; Donahue, Neil M.; Baltensperger, Urs

    2016-05-01

    About half of present-day cloud condensation nuclei originate from atmospheric nucleation, frequently appearing as a burst of new particles near midday. Atmospheric observations show that the growth rate of new particles often accelerates when the diameter of the particles is between one and ten nanometres. In this critical size range, new particles are most likely to be lost by coagulation with pre-existing particles, thereby failing to form new cloud condensation nuclei that are typically 50 to 100 nanometres across. Sulfuric acid vapour is often involved in nucleation but is too scarce to explain most subsequent growth, leaving organic vapours as the most plausible alternative, at least in the planetary boundary layer. Although recent studies predict that low-volatility organic vapours contribute during initial growth, direct evidence has been lacking. The accelerating growth may result from increased photolytic production of condensable organic species in the afternoon, and the presence of a possible Kelvin (curvature) effect, which inhibits organic vapour condensation on the smallest particles (the nano-Köhler theory), has so far remained ambiguous. Here we present experiments performed in a large chamber under atmospheric conditions that investigate the role of organic vapours in the initial growth of nucleated organic particles in the absence of inorganic acids and bases such as sulfuric acid or ammonia and amines, respectively. Using data from the same set of experiments, it has been shown that organic vapours alone can drive nucleation. We focus on the growth of nucleated particles and find that the organic vapours that drive initial growth have extremely low volatilities (saturation concentration less than 10‑4.5 micrograms per cubic metre). As the particles increase in size and the Kelvin barrier falls, subsequent growth is primarily due to more abundant organic vapours of slightly higher volatility (saturation concentrations of 10‑4.5 to 10‑0

  7. The role of low-volatility organic compounds in initial particle growth in the atmosphere.

    PubMed

    Tröstl, Jasmin; Chuang, Wayne K; Gordon, Hamish; Heinritzi, Martin; Yan, Chao; Molteni, Ugo; Ahlm, Lars; Frege, Carla; Bianchi, Federico; Wagner, Robert; Simon, Mario; Lehtipalo, Katrianne; Williamson, Christina; Craven, Jill S; Duplissy, Jonathan; Adamov, Alexey; Almeida, Joao; Bernhammer, Anne-Kathrin; Breitenlechner, Martin; Brilke, Sophia; Dias, Antònio; Ehrhart, Sebastian; Flagan, Richard C; Franchin, Alessandro; Fuchs, Claudia; Guida, Roberto; Gysel, Martin; Hansel, Armin; Hoyle, Christopher R; Jokinen, Tuija; Junninen, Heikki; Kangasluoma, Juha; Keskinen, Helmi; Kim, Jaeseok; Krapf, Manuel; Kürten, Andreas; Laaksonen, Ari; Lawler, Michael; Leiminger, Markus; Mathot, Serge; Möhler, Ottmar; Nieminen, Tuomo; Onnela, Antti; Petäjä, Tuukka; Piel, Felix M; Miettinen, Pasi; Rissanen, Matti P; Rondo, Linda; Sarnela, Nina; Schobesberger, Siegfried; Sengupta, Kamalika; Sipilä, Mikko; Smith, James N; Steiner, Gerhard; Tomè, Antònio; Virtanen, Annele; Wagner, Andrea C; Weingartner, Ernest; Wimmer, Daniela; Winkler, Paul M; Ye, Penglin; Carslaw, Kenneth S; Curtius, Joachim; Dommen, Josef; Kirkby, Jasper; Kulmala, Markku; Riipinen, Ilona; Worsnop, Douglas R; Donahue, Neil M; Baltensperger, Urs

    2016-05-26

    About half of present-day cloud condensation nuclei originate from atmospheric nucleation, frequently appearing as a burst of new particles near midday. Atmospheric observations show that the growth rate of new particles often accelerates when the diameter of the particles is between one and ten nanometres. In this critical size range, new particles are most likely to be lost by coagulation with pre-existing particles, thereby failing to form new cloud condensation nuclei that are typically 50 to 100 nanometres across. Sulfuric acid vapour is often involved in nucleation but is too scarce to explain most subsequent growth, leaving organic vapours as the most plausible alternative, at least in the planetary boundary layer. Although recent studies predict that low-volatility organic vapours contribute during initial growth, direct evidence has been lacking. The accelerating growth may result from increased photolytic production of condensable organic species in the afternoon, and the presence of a possible Kelvin (curvature) effect, which inhibits organic vapour condensation on the smallest particles (the nano-Köhler theory), has so far remained ambiguous. Here we present experiments performed in a large chamber under atmospheric conditions that investigate the role of organic vapours in the initial growth of nucleated organic particles in the absence of inorganic acids and bases such as sulfuric acid or ammonia and amines, respectively. Using data from the same set of experiments, it has been shown that organic vapours alone can drive nucleation. We focus on the growth of nucleated particles and find that the organic vapours that drive initial growth have extremely low volatilities (saturation concentration less than 10(-4.5) micrograms per cubic metre). As the particles increase in size and the Kelvin barrier falls, subsequent growth is primarily due to more abundant organic vapours of slightly higher volatility (saturation concentrations of 10(-4.5) to 10

  8. Typical household vacuum cleaners: the collection efficiency and emissions characteristics for fine particles.

    PubMed

    Lioy, P J; Wainman, T; Zhang, J; Goldsmith, S

    1999-02-01

    The issue of fine particle (PM2.5) exposures and their potential health effects is a focus of scientific research because of the recently promulgated National Ambient Air Quality Standard for PM2.5. Before final implementation, the health and exposure basis for the standard will be reviewed by the U.S. Environmental Protection Agency within the next five years. As part of this process, it is necessary to understand total particle exposure issues and to determine the relative importance of the origin of PM2.5 exposure in various micro-environments. The results presented in this study examine emissions of fine particles from a previously uncharacterized indoor source: the residential vacuum cleaner. Eleven standard vacuum cleaners were tested for the emission rate of fine particles by their individual motors and for their efficiency in collecting laboratory-generated fine particles. An aerosol generator was used to introduce fine potassium chloride (KCl) particles into the vacuum cleaner inlet for the collection efficiency tests. Measurements of the motor emissions, which include carbon, and the KCl aerosol were made using a continuous HIAC/Royco 5130 A light-scattering particle detector. All tests were conducted in a metal chamber specifically designed to completely contain the vacuum cleaner and operate it in a stationary position. For the tested vacuum cleaners, fine particle motor emissions ranged from 9.6 x 10(4) to 3.34 x 10(8) particles/min, which were estimated to be 0.028 to 176 micrograms/min for mass emissions, respectively. The vast majority of particles released were in the range of 0.3-0.5 micron in diameter. The lowest particle emission rate was obtained for a vacuum cleaner that had a high efficiency (HEPA) filter placed after the vacuum cleaner bag and the motor within a sealed exhaust system. This vacuum cleaner removed the KCl particles that escaped the vacuum cleaner bag and the particles emitted by the motor. Results obtained for the KCl

  9. Physicochemical Characteristics of Dust Particles in HVOF Spraying and Occupational Hazards: Case Study in a Chinese Company

    NASA Astrophysics Data System (ADS)

    Huang, Haihong; Li, Haijun; Li, Xinyu

    2016-06-01

    Dust particles generated in thermal spray process can cause serious health problems to the workers. Dust particles generated in high velocity oxy-fuel (HVOF) spraying WC-Co coatings were characterized in terms of mass concentrations, particle size distribution, micro morphologies, and composition. Results show that the highest instantaneous exposure concentration of dust particles in the investigated thermal spray workshop is 140 mg/m3 and the time-weighted average concentration is 34.2 mg/m3, which are approximately 8 and 4 times higher than the occupational exposure limits in China, respectively. The large dust particles above 10 μm in size present a unique morphology of polygonal or irregular block of crushed powder, and smaller dust particles mainly exist in the form of irregular or flocculent agglomerates. Some heavy metals, such as chromium, cobalt, and nickel, are also found in the air of the workshop and their concentrations are higher than the limits. Potential occupational hazards of the dust particles in the thermal spray process are further analyzed based on their characteristics and the workers' exposure to the nanoparticles is assessed using a control banding tool.

  10. Seasonal variations and chemical characteristics of sub-micrometer particles (PM1) in Guangzhou, China

    NASA Astrophysics Data System (ADS)

    Tao, Jun; Shen, Zhenxing; Zhu, Chongshu; Yue, Jianhua; Cao, Junji; Liu, Suixin; Zhu, Lihua; Zhang, Renjian

    2012-11-01

    Daily samples of ambient sub-micrometer particles (PM1, particles with an aerodynamic diameter ≤ 1.0 μm) were collected from July 2009 to April 2010 at an urban site over Guangzhou in southern China. Mass concentrations of water-soluble inorganic ions, organic carbon (OC) and elemental carbon (EC) were determined to characterize the chemical composition of PM1. The mass concentration of PM1 ranged from 14.6 μg m- 3 to 143.3 μg m- 3, with an annual mean value of 52.4 ± 27.3 μg m- 3. Seasonally-averaged PM1 concentrations decreased in the order winter > autumn > spring > summer. The annual mean concentrations of OC and EC were 6.2 ± 3.5 and 5.0 ± 2.9 μg m- 3, respectively. The OC and EC concentrations were measured following the IMPROVE_A thermal/optical reflectance (TOR) protocol. Total carbonaceous aerosol (the sum of organic matter and elemental carbon) accounted for 23.0 ± 4.4% of PM1 mass. Clear seasonal variations in OC and EC suggested sources of these two constituents were remarkable difference among the four seasons. Seasonally averaged OC/EC ratios were 1.2, 1.7, 1.4, and 1.5, from spring to winter respectively. Low OC/EC ratios in comparison with other cities in China revealed that vehicle emissions play an important role in carbonaceous aerosol levels in Guangzhou. SO42 -, NO3- and NH4+ were the three major inorganic ions in PM1, collectively contributing 30.0% ± 6.3% of the PM1 mass. SO42 - and NH4+ were both the highest in autumn and the lowest in summer. In contrast, NO3- was the highest in winter. Sulfur oxidation ratio was positively correlated with solar radiation and O3, but negatively correlated with SO2. Nitrogen oxidation ratio was positively correlated with NO2, NH4+ and Cl-, but showed a negative correlation with temperature. By applying the IMPROVE equation, PM1 mass was reconstructed and showed that (NH4)2SO4, NH4NO3, OM and EC accounted for (30.7 ± 11.4) %, (9.7 ± 5.2) %, (22.6 ± 5.0) % and (9.7 ± 2.3) % of PM1, respectively

  11. A HIGH TEMPERATURE TEST FACILITY FOR STUDYING ASH PARTICLE CHARACTERISTICS OF CANDLE FILTER DURING SURFACE REGENERATION

    SciTech Connect

    Kang, B.S-J.; Johnson, E.K.; Rincon, J.

    2002-09-19

    Hot gas particulate filtration is a basic component in advanced power generation systems such as Integrated Gasification Combined Cycle (IGCC) and Pressurized Fluidized Bed Combustion (PFBC). These systems require effective particulate removal to protect the downstream gas turbine and also to meet environmental emission requirements. The ceramic barrier filter is one of the options for hot gas filtration. Hot gases flow through ceramic candle filters leaving ash deposited on the outer surface of the filter. A process known as surface regeneration removes the deposited ash periodically by using a high pressure back pulse cleaning jet. After this cleaning process has been done there may be some residual ash on the filter surface. This residual ash may grow and this may lead to mechanical failure of the filter. A High Temperature Test Facility (HTTF) was built to investigate the ash characteristics during surface regeneration at high temperatures. The system is capable of conducting surface regeneration tests of a single candle filter at temperatures up to 1500 F. Details of the HTTF apparatus as well as some preliminary test results are presented in this paper. In order to obtain sequential digital images of ash particle distribution during the surface regeneration process, a high resolution, high speed image acquisition system was integrated into the HTTF system. The regeneration pressure and the transient pressure difference between the inside of the candle filter and the chamber during regeneration were measured using a high speed PC data acquisition system. The control variables for the high temperature regeneration tests were (1) face velocity, (2) pressure of the back pulse, and (3) cyclic ash built-up time.

  12. Role of organic coating on carbonyl iron suspended particles in magnetorheological fluids

    NASA Astrophysics Data System (ADS)

    Jang, I. B.; Kim, H. B.; Lee, J. Y.; You, J. L.; Choi, H. J.; Jhon, M. S.

    2005-05-01

    Carbonyl iron (CI) has been widely used as a suspended particle in magnetorheological (MR) fluids. However, pristine CI-based MR fluids have several drawbacks, including severe sedimentation of the CI particles due to the large density difference with the carrier liquid, difficulties in redispersion after caking, abrasion of device surfaces during long-term operation, and rust of iron by oxidation. To overcome these shortcomings, we coated the CI particles with a poly(vinyl butyral) (PVB) shell. CI and CI-PVB particles were suspended in mineral oil and their MR characteristics were examined via a rotational rheometer in a parallel plate geometry equipped with a magnetic field supplier. Yield stress and flow response (shear stress and shear viscosity) were investigated at magnetic field strengths ranging from 0to343kA/m. Although the MR properties, such as yield stress and shear viscosity of CI-PVB based MR fluids, changed slightly compared with those of the pristine CI based MR fluid, the dispersion qualities (e.g., sedimentation stability) were noticeably improved.

  13. Desulfurization characteristics of rapidly hydrated sorbents with various adhesive carrier particles for a semidry CFB-FGD system.

    PubMed

    You, Changfu; Li, Yuan

    2013-03-19

    Semidry flue gas desulfurization (FGD) experiments were conducted using rapidly hydrated sorbents with four different adhesive carrier particles: circulation ash from a circulating fluidized bed boiler (CFBB circulation ash), fly ash from the first electrical field of the electrostatic precipitator of a circulating fluidized bed boiler (CFBB ESP ash), fly ash from a chain boiler (chain boiler ash), and river sand smaller than 1 mm. The influences of various adhesive carrier particles and operating conditions on the desulfurization characteristics of the sorbents were investigated, including sprayed water, reaction temperature, and the ratio of calcium to sulfur (Ca/S). The experimental results indicated that the rapidly hydrated sorbents had better desulfurization characteristics by using adhesive carrier particles which possessed better pore, adhesion, and fluidization characteristics. The desulfurization efficiency of the system increased as the reaction temperature decreased, it improved from 35% to 90% as the mass flow rate of the sprayed water increased from 0 to 10 kg/h, and it increased from 65.6% to 82.7% as Ca/S increased from 1.0 to 2.0. Based on these findings, a new semidry circulating fluidized bed (CFB)-FGD system using rapidly hydrated sorbent was developed. Using the rapidly hydrated sorbent, this system uses a cyclone separator instead of an ESP or a bag filter to recycle the sorbent particles, thereby decreasing the system flow resistance, saving investment and operating costs of the solids collection equipment. PMID:23398211

  14. Physicochemical characteristics, oxidative capacities and cytotoxicities of sulfate-coated, 1,4-NQ-coated and ozone-aged black carbon particles

    NASA Astrophysics Data System (ADS)

    Li, Qian; Shang, Jing; Liu, Jia; Xu, Weiwei; Feng, Xiang; Li, Rui; Zhu, Tong

    2015-02-01

    Black carbon (BC) particles play important roles in climate change, visibility impairment, atmospheric reaction process, and health effect. The aging processes of BC alter not only atmospheric composition, but also the physicochemical characteristics of BC itself, thus impacting the environment and health effects. Here, three types of BC including sulfate-coated, 1,4-naphthoquinone (1,4-NQ)-coated, and O3-aged BC are presented. The morphologies, structures, extraction components, the amount of water-soluble organic carbon (WSOC) and free radical intensities of the three types of BC particles are examined by transmission electron microscopy, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), ultraviolet-visible spectrophotometry, total organic carbon detector and electron paramagnetic resonance, respectively. Dithiothreitol (DTT) and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide assays are utilized to assess the changes in oxidative capacity and cytotoxicity towards murine alveolar macrophage cells. The orders of DTT activities and cytotoxicities of the particles are both arranged as follows: BC/1,4-NQ > BC/O3 > BC > BC/sulfate, mainly because 1,4-NQ owned high oxidative potential and cytotoxicity, while sulfate did not exhibit oxidative capacity and cytotoxicity. The insoluble components of particles contribute most of the total DTT activity, whereas either water or methanol extract is minor contributor. DTT activity was positively correlated with both WSOC content and free radical intensity, with the correlation between DTT activity and WSOC content was stronger than that between DTT activity and free radical intensity.

  15. Adsorption characteristics of 210Pb, 210Po and 7Be onto micro-particle surfaces and the effects of macromolecular organic compounds

    NASA Astrophysics Data System (ADS)

    Yang, Weifeng; Guo, Laodong; Chuang, Chia-Ying; Schumann, Dorothea; Ayranov, Marin; Santschi, Peter H.

    2013-04-01

    210Po, 210Pb and Be isotopes (e.g. 7Be and 10Be) have long been used as proxies of particle/sediment dynamics, carbon cycling, and oceanographic investigations of coupled processes. However, adsorption characteristics and interactions between these nuclides and particle surfaces remain poorly understood. Laboratory studies have been conducted to examine the adsorption of 210Po, 210Pb and 7Be onto micro-particles, including marine suspended particulate matter, kaolinite, Al2O3, SiO2, CaCO3, Fe2O3, MnO2, and chitin in natural seawater (<1 kDa), and the role of macromolecular organic compounds (MOCs), including humic acids (HA), acid polysaccharides (APS) and proteins (BSA) in regulating the adsorption process. In the absence of MOCs, the partition coefficients (Kd, reported in log Kd) range from 3.02 to 5.19 for 210Po, from 3.22 to 6.29 for 210Pb, and from 3.57 to 4.65 for 7Be. Ferric and manganese oxides are the strongest sorbents of 210Po and 210Pb, comparing with SiO2 and CaCO3. In the presence of the protein BSA, both SiO2 and CaCO3 preferentially adsorb 210Po over 210Pb, whereas the opposite effect was observed in the presence of acid polysaccharides, indicating that proteins could enhance the adsorption of 210Po and acid polysaccharides enhance the adsorption of 210Pb. The log Kd values of both 210Po and 210Pb in the presence of MOCs become similar (log Kd at ˜4.0) for all lithogenic and biogenic particles, suggesting that their adsorption is likely controlled by specific natural organic compounds associated with particle surfaces. For 7Be, the highest and lowest log Kd value was measured, in general, on SiO2 and CaCO3, respectively, consistent with field observations. Nevertheless, the log Kd values of 7Be varied little between particle types regardless of the presence or absence of MOCs, suggesting that the adsorption of Be on particle surfaces is less affected by particle composition or MOCs. These results indicate that 7Be and 10Be could quantitatively

  16. Flow characteristic of in-flight particles in supersonic plasma spraying process

    NASA Astrophysics Data System (ADS)

    Wei, Pei; Wei, Zhengying; Zhao, Guangxi; Du, Jun; Bai, Y.

    2015-10-01

    In this paper, a computational model based on supersonic plasma spraying (SAPS) is developed to describe the plasma jet coupled with the injection of carrier gas and particles for SAPS. Based on a high-efficiency supersonic spraying gun, the 3D computational model of spraying gun was built to study the features of plasma jet and its interactions with the sprayed particles. Further the velocity and temperature of in-flight particles were measured by Spray Watch 2i, the shape of in-flight particles was observed by scanning electron microscope. Numerical results were compared with the experimental measurements and a good agreement has been achieved. The flight process of particles in plasma jet consists of three stages: accelerated stage, constant speed stage and decelerated stage. Numerical and experimental indicates that the H2 volume fraction in mixture gas of Ar + H2 should keep in the range of 23-26 %, and the distance of 100 mm is the optimal spraying distance in Supersonic atmosphere plasma spraying. Particles were melted and broken into small child particles by plasma jet and the diameters of most child particles were less than 30 μm. In general, increasing the particles impacting velocity and surface temperature can decrease the coating porosity.

  17. Study of the comminution characteristics of coal by single particle breakage test device

    SciTech Connect

    Sahoo, R.

    2005-09-01

    Single-particle breakage tests of South Blackwater and Ensham coal from the Bowen Basin area in Queensland were conducted by a computer-monitored twin-pendulum device to measure the energy utilization pattern of the breakage particles. Three particle sizes (-16.0+13.2mm, -13.2+11.2mm, -11.2+9.5mm) of each coal were tested by a pendulum device at five input energy levels to measure the specific comminution energy. When particles were tested at constant input energy, the variation of comminution energy between the same size broken particles of Ensham coal was minimal, because Ensham coal is a softer and higher friability coal, which absorbs more input energy than harder coal during breakage tests. For different particle sizes, the specific comminution energy increases linearly with the input energy and the fineness of the breakage products increases with the specific comminution energy. The size distribution graphs are curved but approach linearity in the finer region. At a constant input energy, the twin pendulum breakage product results show that the fineness of the products increases with decrease in particle size and South Blackwater coal produced finer products than the Ensham coal. The t-curves are the family of size distribution curves, which can describe the product size distribution of the breakage particles during single-particle breakage tests.

  18. Technical Note: New methodology for measuring viscosities in small volumes characteristic of environmental chamber particle samples

    NASA Astrophysics Data System (ADS)

    Renbaum-Wolff, L.; Grayson, J. W.; Bertram, A. K.

    2013-01-01

    Herein, a method for the determination of viscosities of small sample volumes is introduced, with important implications for the viscosity determination of particle samples from environmental chambers (used to simulate atmospheric conditions). The amount of sample needed is < 1 μl, and the technique is capable of determining viscosities (η) ranging between 10-3 and 103 Pascal seconds (Pa s) in samples that cover a range of chemical properties and with real-time relative humidity and temperature control; hence, the technique should be well-suited for determining the viscosities, under atmospherically relevant conditions, of particles collected from environmental chambers. In this technique, supermicron particles are first deposited on an inert hydrophobic substrate. Then, insoluble beads (~1 μm in diameter) are embedded in the particles. Next, a flow of gas is introduced over the particles, which generates a shear stress on the particle surfaces. The sample responds to this shear stress by generating internal circulations, which are quantified with an optical microscope by monitoring the movement of the beads. The rate of internal circulation is shown to be a function of particle viscosity but independent of the particle material for a wide range of organic and organic-water samples. A calibration curve is constructed from the experimental data that relates the rate of internal circulation to particle viscosity, and this calibration curve is successfully used to predict viscosities in multicomponent organic mixtures.

  19. Technical Note: New methodology for measuring viscosities in small volumes characteristic of environmental chamber particle samples

    NASA Astrophysics Data System (ADS)

    Renbaum-Wolff, L.; Grayson, J. W.; Bertram, A. K.

    2012-10-01

    Herein, a method for the determination of viscosities of small sample volumes is introduced, with important implications for the viscosity determination of particle samples from environmental chambers (used to simulate atmospheric conditions). The amount of sample needed is < 1 μl, and the technique is capable of determining viscosities (η) ranging between 10-3 and 103 Pascal seconds (Pa s) in samples that cover a range of chemical properties and with real-time relative humidity and temperature control; hence, the technique should be well-suited for determining the viscosities, under atmospherically relevant conditions, of particles collected from environmental chambers. In this technique, supermicron particles are first deposited on an inert hydrophobic substrate. Then, insoluble beads (~1 μm in diameter) are embedded in the particles. Next, a flow of gas is introduced over the particles, which generates a shear stress on the particle surfaces. The sample responds to this shear stress by generating internal circulations, which are quantified with an optical microscope by monitoring the movement of the beads. The rate of internal circulation is shown to be a function of particle viscosity but independent of the particle material for a wide range of organic and organic-water samples. A calibration curve is constructed from the experimental data that relates the rate of internal circulation to particle viscosity, and this calibration curve is successfully used to predict viscosities in multicomponent organic mixtures.

  20. [Characteristics and Resources of Fly Ash Particles in the Snowpack of Jinfo Mountain, Chongqing].

    PubMed

    Yu, Zheng-liang; Yang, Ping-heng; Jing, Wei-li; Yuan, Dao-xian; Ren, Kun; Li, Lin-li

    2015-12-01

    Snow can preserve the atmospheric information, which makes it become a good media in studying regional environment. Jinfo Mountain with an elevation of 2251.1 m, located at the transition zone between Sichuan basin and Yunnan-Guizhou Plateau, is deeply affected by human activities, and snowfall is the main form of precipitation during the winter. While the literature focus on single spherical particles in this area is uncommon. Five snow samples were collected, and determined morphology and chemical composition of 132 single spherical particles by the scanning electron microscope couples with energy dispersive X-ray spectrometer (SEM-EDS). Results show that snowfall in Jinfo Mountain includes the massive fly ash particles with 1.64 µm in average diameter and 1.09 in average roundness which contains smooth particles, rough particles and soot particles, accounting for 80. 31% , 14. 39% and 5.30% of statistical particles respectively. Furthermore, on the basis of chemical information obtained from EDS, the fly ash particles counted in this research can be classified into 5 types, namely, Si-dominant particles, C-dominant particles, Fe-dominant particles, Al-dominant particles and Ti-dominant particles, which make up 34.09%, 49.24%, 12.88%, 2.27% and 1.52% respectively. In conclusion, it can be inferred, based on the analysis of meteorological information, the properties of fly ash particles, and backward air mass trajectory and dispersion analysis, that C-dominant fly ash mainly comes from daily life and industry activities, Si-dominant fly ash particles may originate from the plant industry located in west Chingqing, north of Guizhou province, central of Hunan province, Zhejiang province, Jiangxi province and the west of Guangdong province, while the activities of foundry and iron or steel plants in the west of Chongqing, the north of Guizhou province and the central of Hunan province may be the main sources of Fe-dominant fly ash particles in our samples. PMID

  1. More Practice, Less Preach? The role of supervision processes and therapist characteristics in EBP implementation

    PubMed Central

    Bearman, Sarah Kate; Weisz, John R.; Chorpita, Bruce F.; Hoagwood, Kimberly; Ward, Alyssa; Ugueto, Ana M.; Bernstein, Adam

    2014-01-01

    Identifying predictors of evidence-based practice (EBP) use, such as supervision processes and therapist characteristics, may support dissemination. Therapists (N = 57) received training and supervision in EBPs to treat community-based youth (N = 136). Supervision involving modeling and role-play predicted higher overall practice use than supervision involving discussion, and modeling predicted practice use in the next therapy session. No therapist characteristics predicted practice use, but therapist sex and age moderated the supervision and practice use relation. Supervision involving discussion predicted practice use for male therapists only, and modeling and role-play in supervision predicted practice use for older, not younger, therapists. PMID:23525895

  2. Seawater ultrafiltration: role of particles on organic rejections and permeate fluxes.

    PubMed

    Massé, Anthony; Thi, Hanh Nguyen; Roelens, Guillaume; Legentilhomme, Patrick; Jaouen, Pascal

    2013-01-01

    The role of natural compounds of seawater and added particles on mechanisms of membrane fouling and organic matter rejection has been investigated. Ultrafiltration (100 kDa) has been conducted in both dead-end (out/in) and tangential (in/out) modes on polysulfone hollow fibre membranes. The permeate fluxes are approximately three times higher for tangential ultrafiltration than for dead-end ultrafiltration without differences between settled and non-settled seawaters (NS-SWs) (51-55 L h(-1) m(-2) for tangential and 17-22 L h(-1) m(-2) for dead-end ultrafiltration). Adding bentonite or kieselguhr from 0.13 to 1.13 g L(-1) of suspended solids to NS-SW does not act significantly on permeate fluxes of dead-end contrary to tangential ultrafiltration. For the latter, an addition of particles induces a slight drop of permeate fluxes. Original particles of reconstituted seawater could increase the cake porosity, whereas bentonite and kieselguhr, compounds smaller than original particles, could participate in the formation of a compact cake. The total organic carbon removal was equal to approximately 80% whatever the mode of ultrafiltration may be and the suspended solid concentration ranged from 0.13 to 1.13 g L(-1). Dissolved organic carbon (DOC) and colloidal organic carbon rejection rates were greater for tangential ultrafiltration (37-49%) compared with dead-end ultrafiltration (30-44%) at different concentrations of added particles. Bentonite or kieselguhr addition induced a slight decrease of DOC removal. In the case of particles addition, the worst DOC rejection is found for bentonite. PMID:24527616

  3. Particle Motion Analysis Reveals Nanoscale Bond Characteristics and Enhances Dynamic Range for Biosensing.

    PubMed

    Visser, Emiel W A; van IJzendoorn, Leo J; Prins, Menno W J

    2016-03-22

    Biofunctionalized colloidal particles are widely used as labels in bioanalytical assays, lab-on-chip devices, biophysical research, and in studies on live biological systems. With detection resolution going down to the level of single particles and single molecules, understanding the nature of the interaction of the particles with surfaces and substrates becomes of paramount importance. Here, we present a comprehensive study of motion patterns of colloidal particles maintained in close proximity to a substrate by short molecular tethers (40 nm). The motion of the particles (500-1000 nm) was optically tracked with a very high localization accuracy (below 3 nm). A surprisingly large variation in motion patterns was observed, which can be attributed to properties of the particle-molecule-substrate system, namely the bond number, the nature of the bond, particle protrusions, and substrate nonuniformities. Experimentally observed motion patterns were compared to numerical Monte Carlo simulations, revealing a close correspondence between the observed motion patterns and properties of the molecular system. Particles bound via single tethers show distinct disc-, ring-, and bell-shaped motion patterns, where the ring- and bell-shaped patterns are caused by protrusions on the particle in the direct vicinity of the molecular attachment point. Double and triple tethered particles exhibit stripe-shaped and triangular-shaped motion patterns, respectively. The developed motion pattern analysis allows for discrimination between particles bound by different bond types, which opens the possibility to improve the limit of detection and the dynamic range of bioanalytical assays, with a projected increase of dynamic range by nearly 2 orders of magnitude. PMID:26913834

  4. Evidence for the role of organics in aerosol particle formation under atmospheric conditions

    NASA Astrophysics Data System (ADS)

    Baltensperger, Urs

    2010-05-01

    New particle formation in the atmosphere is an important parameter in governing the radiative forcing of atmospheric aerosols. However, detailed nucleation mechanisms remain still ambiguous, as laboratory data have so far not been successful in explaining atmospheric nucleation. We investigated the formation of new particles in a smog chamber simulating the photochemical formation of H2SO4 and organic condensable species. Nucleation occurs at H2SO4 concentrations similar to the ones found in the ambient atmosphere during nucleation events. The measured particle formation rates are proportional to the product of the concentrations of H2SO4 and an organic molecule. This suggests that only one H2SO4 molecule and one organic molecule are involved in the rate limiting step of the observed nucleation process. Parameterizing this process in a global aerosol model results in substantially better agreement with ambient observations compared to control runs. Reference: Axel Metzger, Bart Verheggen, Josef Dommen, Jonathan Duplissy, Andre S. H. Prevot, Ernest Weingartner, Ilona Riipinen, Markku Kulmala, Dominick V. Spracklen, Kenneth S. Carslaw, and Urs Baltensperger, Evidence for the role of organics in aerosol particle formation under atmospheric conditions, Proc. Natl. Acad. Sci. USA, 107 (2010), www.pnas.org/cgi/doi/10.1073/pnas.0911330107.

  5. Characteristics of movement of solid particle in snow-water mixtures

    NASA Astrophysics Data System (ADS)

    Sasaki, Mikio

    2009-02-01

    In the present study, experimental observations for the movement of solid particles in the solid-water mixture flow were carried out in the horizontal pipe with a high-speed camera. When flow is slow, the picture was taken at 1000 scenes per second, and when flow is fast, the flow observation catches the solid particle very clearly at 4000 scenes per second. From the flow observation of the solid-water multi-phase flow that the solid specific gravity is near that of the transportation fluid, the change of the solid particle position and the speed change of the solid particle were shown in the present study. Within the scope of the present study, the following conclusions were derived. The solid particle flows with moving up and down. The change of the speed is large. The speeds in the lower layer and upper layer are both great fluctuations because the change of the speed near the wall is large. On the other hand, the vicinity of the solid particle in the middle layer of the pipe fluctuates a little and a steady speed continues. The solid particle near the wall rotates greatly, however, the solid particle in the middle layer of the pipe shows a small rotation. The rotation means that the flow of the mixtures is not Bingham flow.

  6. Biopolymer nanoparticles from heat-treated electrostatic protein-polysaccharide complexes: factors affecting particle characteristics.

    PubMed

    Jones, Owen Griffith; McClements, David Julian

    2010-03-01

    Biopolymer nanoparticles can be formed by heating globular protein-ionic polysaccharide electrostatic complexes above the thermal denaturation temperature of the protein. This study examined how the size and concentration of biopolymer particles formed by heating beta-lactoglobulin-pectin complexes could be manipulated by controlling preparation conditions: pH, ionic strength, protein concentration, holding time, and holding temperature. Biopolymer particle size and concentration increased with increasing holding time (0 to 30 min), decreasing holding temperature (90 to 70 degrees C), increasing protein concentration (0 to 2 wt/wt%), increasing pH (4.5 to 5), and increasing salt concentration (0 to 50 mol/kg). The influence of these factors on biopolymer particle size was attributed to their impact on protein-polysaccharide interactions, and on the kinetics of nucleation and particle growth. The knowledge gained from this study will facilitate the rational design of biopolymer particles with specific physicochemical and functional attributes. PMID:20492252

  7. Characteristics of fine particle carbonaceous aerosol at two remote sites in Central Asia

    NASA Astrophysics Data System (ADS)

    Miller-Schulze, Justin P.; Shafer, Martin M.; Schauer, James J.; Solomon, Paul A.; Lantz, Jeffrey; Artamonova, Maria; Chen, Boris; Imashev, Sanjar; Sverdlik, Leonid; Carmichael, Greg R.; Deminter, Jeff T.

    2011-12-01

    Central Asia is a relatively understudied region of the world in terms of characterizing ambient particulate matter (PM) and quantifying source impacts of PM at receptor locations, although it is speculated to have an important role as a source region for long-range transport of PM to Eastern Asia, the Pacific Ocean, and the Western United States. PM is of significant interest not only because of its adverse effect on public health but also due to its more recently realized role in climate change. To investigate the sources and characteristics of PM in the region, a series of PM 2.5 and PM 10 samples were collected on an every-other-day basis at two sites (termed "Bishkek" and "Teploklyuchenka") in the Central Asian nation of the Kyrgyz Republic (also known as Kyrgyzstan) for a full year from July 2008 to July 2009. These samples were analyzed using standard methods for mass, organic carbon (OC), elemental carbon (EC), water-soluble organic carbon (WSOC), water-insoluble organic carbon by difference (OC minus WSOC) and a variety of molecular marker chemical species to be used in a chemical mass balance (CMB) model to apportion the sources of OC. These analyses indicate that approximately 19 ± 6.4% of the PM 2.5 mass at both sites throughout the year consists of OC. The carbonaceous component of PM 2.5 is dominated by OC, with OC/Total Carbon (TC) ratios being around 0.8 in the winter to almost 0.95 in the summer months. The CMB analysis indicated that mobile sources, i.e., gasoline and diesel engine exhaust, biomass combustion, and biogenic secondary organic aerosol (SOA) formation from isoprene and α-pinene precursors in the summer months were the dominant sources of OC. A strong positive correlation was observed between non-biomass burning WSOC and the un-apportioned OC from the CMB analysis, indicating that some of this un-apportioned OC is WSOC and likely the result of SOA-forming atmospheric processes that were not estimated by the CMB analysis performed. In

  8. Chemo-Mechanical Characteristics of Mud Formed from Environmental Dust Particles in Humid Ambient Air

    PubMed Central

    Hassan, Ghassan; Yilbas, B. S.; Said, Syed A. M.; Al-Aqeeli, N.; Matin, Asif

    2016-01-01

    Mud formed from environmental dust particles in humid ambient air significantly influences the performance of solar harvesting devices. This study examines the characterization of environmental dust particles and the chemo-mechanics of dry mud formed from dust particles. Analytical tools, including scanning electron microscopy, atomic force microscopy, energy dispersive spectroscopy, particle sizing, and X-ray diffraction, are used to characterize dry mud and dust particles. A micro/nano tribometer is used to measure the tangential force and friction coefficient while tensile tests are carried out to assess the binding forces of dry mud pellets. After dry mud is removed, mud residuals on the glass surface are examined and the optical transmittance of the glass is measured. Dust particles include alkaline compounds, which dissolve in water condensate and form a mud solution with high pH (pH = 7.5). The mud solution forms a thin liquid film at the interface of dust particles and surface. Crystals form as the mud solution dries, thus, increasing the adhesion work required to remove dry mud from the surface. Optical transmittance of the glass is reduced after dry mud is removed due to the dry mud residue on the surface. PMID:27445272

  9. Effect of Substrate and Its Shape on in-Flight Particle Characteristics in Suspension Plasma Spraying

    NASA Astrophysics Data System (ADS)

    Pourang, K.; Moreau, C.; Dolatabadi, A.

    2016-01-01

    Obtaining a uniform coating on curved mechanical parts such as gas turbine blades is one of the industrial challenges in suspension plasma spraying. Through a three dimensional numerical analysis, this study is aimed at providing a better understanding of the effect of substrate curvature on in-flight particle temperature, velocity, and trajectory. The high temperature and high velocity plasma flow is simulated inside the plasma torch using a uniform volumetric heat source in the energy equation. The suspension of yttria-stabilized zirconia particles is molded as a multicomponent droplet while catastrophic breakup regime is considered for simulating the secondary break up when the suspension interacts with the plasma flow. A two-way coupled Eulerian-Lagrangian approach along with a stochastic discrete model was used to track the particle trajectory. Particle size distribution in the vicinity of the substrate at different stand-off distances has been investigated. The results show that sub-micron particles obtain higher velocity and temperature compared to the larger particles. However, due to the small Stokes number associated with sub-micron particles, they are more sensitive to the change of the gas flow streamlines in the vicinity of a curved substrate.

  10. Chemo-Mechanical Characteristics of Mud Formed from Environmental Dust Particles in Humid Ambient Air

    NASA Astrophysics Data System (ADS)

    Hassan, Ghassan; Yilbas, B. S.; Said, Syed A. M.; Al-Aqeeli, N.; Matin, Asif

    2016-07-01

    Mud formed from environmental dust particles in humid ambient air significantly influences the performance of solar harvesting devices. This study examines the characterization of environmental dust particles and the chemo-mechanics of dry mud formed from dust particles. Analytical tools, including scanning electron microscopy, atomic force microscopy, energy dispersive spectroscopy, particle sizing, and X-ray diffraction, are used to characterize dry mud and dust particles. A micro/nano tribometer is used to measure the tangential force and friction coefficient while tensile tests are carried out to assess the binding forces of dry mud pellets. After dry mud is removed, mud residuals on the glass surface are examined and the optical transmittance of the glass is measured. Dust particles include alkaline compounds, which dissolve in water condensate and form a mud solution with high pH (pH = 7.5). The mud solution forms a thin liquid film at the interface of dust particles and surface. Crystals form as the mud solution dries, thus, increasing the adhesion work required to remove dry mud from the surface. Optical transmittance of the glass is reduced after dry mud is removed due to the dry mud residue on the surface.

  11. Chemo-Mechanical Characteristics of Mud Formed from Environmental Dust Particles in Humid Ambient Air.

    PubMed

    Hassan, Ghassan; Yilbas, B S; Said, Syed A M; Al-Aqeeli, N; Matin, Asif

    2016-01-01

    Mud formed from environmental dust particles in humid ambient air significantly influences the performance of solar harvesting devices. This study examines the characterization of environmental dust particles and the chemo-mechanics of dry mud formed from dust particles. Analytical tools, including scanning electron microscopy, atomic force microscopy, energy dispersive spectroscopy, particle sizing, and X-ray diffraction, are used to characterize dry mud and dust particles. A micro/nano tribometer is used to measure the tangential force and friction coefficient while tensile tests are carried out to assess the binding forces of dry mud pellets. After dry mud is removed, mud residuals on the glass surface are examined and the optical transmittance of the glass is measured. Dust particles include alkaline compounds, which dissolve in water condensate and form a mud solution with high pH (pH = 7.5). The mud solution forms a thin liquid film at the interface of dust particles and surface. Crystals form as the mud solution dries, thus, increasing the adhesion work required to remove dry mud from the surface. Optical transmittance of the glass is reduced after dry mud is removed due to the dry mud residue on the surface. PMID:27445272

  12. Participant roles of bullying in adolescence: Status characteristics, social behavior, and assignment criteria.

    PubMed

    Pouwels, J Loes; Lansu, Tessa A M; Cillessen, Antonius H N

    2016-05-01

    This study had three goals. First, we examined the prevalence of the participant roles of bullying in middle adolescence and possible gender differences therein. Second, we examined the behavioral and status characteristics associated with the participant roles in middle adolescence. Third, we compared two sets of criteria for assigning students to the participant roles of bullying. Participants were 1,638 adolescents (50.9% boys, Mage  = 16.38 years, SD =.80) who completed the shortened participant role questionnaire and peer nominations for peer status and behavioral characteristics. Adolescents were assigned to the participant roles according to the relative criteria of Salmivalli, Lagerspetz, Björkqvist, Österman, and Kaukiainen (1996). Next, the students in each role were divided in two subgroups based on an additional absolute criterion: the Relative Only Criterion subgroup (nominated by less than 10% of their classmates) and the Absolute & Relative Criterion subgroup (nominated by at least 10% of their classmates). Adolescents who bullied or reinforced or assisted bullies were highly popular and disliked and scored high on peer-valued characteristics. Adolescents who were victimized held the weakest social position in the peer group. Adolescents who defended victims were liked and prosocial, but average in popularity and peer-valued characteristics. Outsiders held a socially weak position in the peer group, but were less disliked, less aggressive, and more prosocial than victims. The behavior and status profiles of adolescents in the participant roles were more extreme for the Absolute & Relative Criterion subgroup than for the Relative Only Criterion subgroup. Aggr. Behav. 42:239-253, 2016. © 2015 Wiley Periodicals, Inc. PMID:26350031

  13. Characteristics and role of dynamic membrane layer in anaerobic membrane bioreactors.

    PubMed

    Ersahin, Mustafa Evren; Tao, Yu; Ozgun, Hale; Spanjers, Henri; van Lier, Jules B

    2016-04-01

    A submerged anaerobic dynamic membrane bioreactor (AnDMBR) was operated for treatment of concentrated wastewater. The dynamic membrane (DM) or cake layer was characterized on its physicochemical and biological composition and the role of the DM layer in treatment and filtration performances was assessed. The results showed that the DM layer had an important role in organic matter removal. Both organic and inorganic materials, such as sludge particles, soluble microbial products (SMP), extracellular polymeric substances (EPS), and Ca, N, P, Mg precipitations contributed to the DM layer formation. Thus, effective retention of very small particles by the DM layer was achieved. The DM layer had higher microbial diversity and different microbial population composition in comparison to the bulk sludge. Overall, this study provided a better understanding about the DM layer structure in AnDMBRs, which might lead to increased applicability of this promising technology for the treatment of concentrated wastewaters. PMID:26418620

  14. Broverman's methodology reversed: assessing university students' perceptions of the gender-role characteristics of counselors.

    PubMed

    Adams, Eve M; McNeil, Keith; Dubsick, Nicole

    2004-02-01

    This study examined university students' perceptions of which gender-role characteristics described helpful counselors for 137 nonmajors from an introduction to counseling class. Using a modification of the Broverman, et al. method (1970) and a modified version of their Stereotype Questionnaire, participants were randomly assigned to one of three conditions. Participants indicated the characteristics of a helpful counselor, a helpful female counselor, or a helpful male counselor using 20 bipolar items of gender-role characteristics. t tests were applied to whether agreement of the pole considered most frequently was greater than chance (50%). Analysis indicated agreement on characteristics were most helpful in a counselor, and the direction of this agreement did not differ across the three conditions or as a function of participants' sex. Agreement was high for the individual gender-role characteristic items across conditions as two of 20 items showed significant differences. There was significantly more agreement that male counselors should not have their feelings easily hurt than female counselors and significantly less agreement that male counselors should be able to express tender feelings easily relative to a counselor of unspecified sex. PMID:15077779

  15. The Role of Biographical Characteristics in Preservice Classroom Teachers' School Physical Activity Promotion Attitudes

    ERIC Educational Resources Information Center

    Webster, Collin A.; Monsma, Eva; Erwin, Heather E.

    2010-01-01

    Recommendations for increasing children's daily physical activity (PA) call on classroom teachers to assume an activist role at school. This study examined relationships among preservice classroom teachers' (PCT; n = 247) biographical characteristics, perceptions and attitudes regarding school PA promotion (SPAP). Results indicated participants…

  16. A Research Brief: A Novel Characteristic of Role Model Choice by Black Male College Students

    ERIC Educational Resources Information Center

    Bennett, B. J.; Davis, R.; Harris, A.; Brown, K.; Wood, P.; Jones, D. R.; Spencer, S.; Nelson, L.; Brown, J.; Waddell, T.; Jones, C. B.

    2004-01-01

    The purpose of the present research brief is to report a novel characteristic of role model choice that may be unreported in the literature for black males and to assess this finding in relation to perceived attractiveness of self and a member of the opposite sex. The study found that the proportion of males choosing themselves as their own role…

  17. Foster Parents Speak: Preferred Characteristics of Foster Children and Experiences in the Role of Foster Parent

    ERIC Educational Resources Information Center

    Rosenwald, Mitchell; Bronstein, Laura

    2008-01-01

    Foster parents play a pivotal role in the child welfare system. A study that employed focus groups with foster parents was conducted at a private foster care agency with the initial purpose of understanding the characteristics of foster children that foster parents both preferred and not preferred. In the qualitative research tradition, their…

  18. The Impact of Working Conditions, Social Roles, and Personal Characteristics on Gender Differences in Distress.

    ERIC Educational Resources Information Center

    Lowe, Graham S.; Northcott, Herbert C.

    1988-01-01

    Responses to a survey of 992 unionized postal workers in Canada revealed the effects of working conditions, nonwork roles, and personal characteristics on self-reports of depression, irritability, and psychophysiological symptoms. Males and females respond similarly to stressful jobs, although they report slightly higher levels of distress.…

  19. The Role of Reader Characteristics in Processing and Learning from Informational Text

    ERIC Educational Resources Information Center

    Fox, Emily

    2009-01-01

    This article considers the role of reader characteristics in processing and learning from informational text, as revealed in think-aloud research. A theoretical framework for relevant aspects of readers' processing and products was developed. These relevant aspects included three attentional foci for processing (comprehension, monitoring, and…

  20. The Role of Student Characteristics in Studying Micro Teaching-Learning Environments

    ERIC Educational Resources Information Center

    Seidel, Tina

    2006-01-01

    This study explored the role of student characteristics in studying micro teaching-learning environments. The overarching hypothesis is that teachers teach differently to micro environments in their classrooms. This study is the first of a series exploring the following four questions: (1) What student profiles are identified at the beginning of a…

  1. Comment on 'Mapping the dayside ionosphere to the magnetosphere according to particle precipitation characteristics' by Newell and Meng

    NASA Technical Reports Server (NTRS)

    Lockwood, M.; Smith, M. F.

    1993-01-01

    Newell and Meng (1992) present maps of the occurrence probability of various classifications of particle precipitation as seen in the dayside topside ionosphere. It is argued that these are maps of the magnetospheric regions, a contention with which their critics disagree. The latter conclude that, because of convection, any one population of particles seen at low altitudes will have originated from a wide variety of locations, and particle characteristics cannot be mapped back to those in the magnetosphere without detailed knowledge of both the convection and magnetic field. Steplike boundaries between the regions will arise from nonsteady-state conditions and cannot be envisaged as steady-state magnetospheric boundaries between two plasma populations. In their reply Newell and Meng contend that convection does not move plasma from the LLBL into the cusp. Most of the LLBL plasma comes from the magnetosheath, so the direction of plasma transfer is in the other direction.

  2. Probing surface characteristics of diffusion-limited-aggregation clusters with particles of variable size

    NASA Astrophysics Data System (ADS)

    Menshutin, A. Yu.; Shchur, L. N.; Vinokur, V. M.

    2007-01-01

    We develop a technique for probing the harmonic measure of a diffusion-limited-aggregation (DLA) cluster surface with variable-size particles and generate 1000 clusters with 50×106 particles using an original off-lattice killing-free algorithm. Taking, in sequence, the limit of the vanishing size of the probing particles and then sending the growing cluster size to infinity, we achieve unprecedented accuracy in determining the fractal dimension D=1.7100(2) crucial to the characterization of the geometric properties of DLA clusters.

  3. Measured and Modeled Humidification Factors of Fresh Smoke Particles From Biomass Burning: Role of Inorganic Constituents

    SciTech Connect

    Hand, Jenny L.; Day, Derek E.; McMeeking, Gavin M.; Levin, Ezra; Carrico, Christian M.; Kreidenweis, Sonia M.; Malm, William C.; Laskin, Alexander; Desyaterik, Yury

    2010-07-09

    During the 2006 FLAME study (Fire Laboratory at Missoula Experiment), laboratory burns of biomass fuels were performed to investigate the physico-chemical, optical, and hygroscopic properties of fresh biomass smoke. As part of the experiment, two nephelometers simultaneously measured dry and humidified light scattering coefficients (bsp(dry) and bsp(RH), respectively) in order to explore the role of relative humidity (RH) on the optical properties of biomass smoke aerosols. Results from burns of several biomass fuels showed large variability in the humidification factor (f(RH) = bsp(RH)/bsp(dry)). Values of f(RH) at RH=85-90% ranged from 1.02 to 2.15 depending on fuel type. We incorporated measured chemical composition and size distribution data to model the smoke hygroscopic growth to investigate the role of inorganic and organic compounds on water uptake for these aerosols. By assuming only inorganic constituents were hygroscopic, we were able to model the water uptake within experimental uncertainty, suggesting that inorganic species were responsible for most of the hygroscopic growth. In addition, humidification factors at 85-90% RH increased for smoke with increasing inorganic salt to carbon ratios. Particle morphology as observed from scanning electron microscopy revealed that samples of hygroscopic particles contained soot chains either internally or externally mixed with inorganic potassium salts, while samples of weak to non-hygroscopic particles were dominated by soot and organic constituents. This study provides further understanding of the compounds responsible for water uptake by young biomass smoke, and is important for accurately assessing the role of smoke in climate change studies and visibility regulatory efforts.

  4. Surface characteristics and photoactivity of silver-modified palygorskite clays coated with nanosized titanium dioxide particles

    SciTech Connect

    Zhao Difang . E-mail: zdf6910@163.com; Zhou Jie; Liu Ning

    2007-03-15

    This paper presents the results of a study in which nanosized titanium dioxide (TiO{sub 2}) crystal particles were coated onto the surface of palygorskite fibrous clay which had been modified by silver ions using titanium tetrachloride as a precursor. Coated TiO{sub 2} particles with the anatase structure were formed after calcining at 400 deg. C for 2 h in air. Various analytical techniques were used to characterize the surface properties of titanium dioxide particles on the palygorskite. Transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses showed that TiO{sub 2} particles were supported on the surface of the palygorskite clays and their size was in the range of 3-6 nm. The titanium oxide coatings were found to be very active for the photocatalytic decomposition of methylene blue.

  5. Heat-transfer characteristics of flowing and stationary particle-bed-type fusion-reactor blankets

    SciTech Connect

    Nietert, R.E.

    1983-02-01

    The following five appendices are included: (1) physical properties of materials, (2) thermal entrance length Nusselt number variations, (3) stationary particle bed temperature variations, (4) falling bed experimental data and calculations, and (5) stationary bed experimental data and calculations. (MOW)

  6. Suspended load and bed-load transport of particle-laden gravity currents: the role of particle-bed interaction

    NASA Astrophysics Data System (ADS)

    Dufek, J.; Bergantz, G. W.

    2007-03-01

    The development of particle-enriched regions (bed-load) at the base of particle-laden gravity currents has been widely observed, yet the controls and relative partitioning of material into the bed-load is poorly understood. We examine particle-laden gravity currents whose initial mixture (particle and fluid) density is greater than the ambient fluid, but whose interstitial fluid density is less than the ambient fluid (such as occurs in pyroclastic flows produced during volcanic eruptions or when sediment-enriched river discharge enters the ocean, generating hyperpycnal turbidity currents). A multifluid numerical approach is employed to assess suspended load and bed-load transport in particle-laden gravity currents under varying boundary conditions. Particle-laden flows that traverse denser fluid (such as pyroclastic flows crossing water) have leaky boundaries that provide the conceptual framework to study suspended load in isolation from bed-load transport. We develop leaky and saltation boundary conditions to study the influence of flow substrate on the development of bed-load. Flows with saltating boundaries develop particle-enriched basal layers (bed-load) where momentum transfer is primarily a result of particle-particle collisions. The grain size distribution is more homogeneous in the bed-load and the saltation boundaries increase the run-out distance and residence time of particles in the flow by as much as 25% over leaky boundary conditions. Transport over a leaky substrate removes particles that reach the bottom boundary and only the suspended load remains. Particle transport to the boundary is proportional to the settling velocity of particles, and flow dilution results in shear and buoyancy instabilities at the upper interface of these flows. These instabilities entrain ambient fluid, and the continued dilution ultimately results in these currents becoming less dense than the ambient fluid. A unifying concept is energy dissipation due to particle

  7. Morphological and chemical composition characteristics of summertime atmospheric particles collected at Tokchok Island, Korea

    NASA Astrophysics Data System (ADS)

    Geng, Hong; Jung, Hae-Jin; Park, YooMyung; Hwang, HeeJin; Kim, HyeKyeong; Kim, Yoo Jung; Sunwoo, Young; Ro, Chul-Un

    Determination of the chemical compositions of atmospheric single particles in the Yellow Sea region is critical for evaluating the environmental impact caused by air pollutants emitted from mainland China and the Korean peninsula. After ambient aerosol particles were collected by the Dekati PM10 cascade impactor on July 17-23, 2007 at Tokchok Island (approximately 50 km west of the Korean coast nearby Seoul), Korea, overall 2000 particles (on stage 2 and 3 with cut-off diameters of 2.5-10 μm and 1.0-2.5 μm, respectively) in 10 samples were determined by using low- Z particle electron probe X-ray microanalysis. X-ray spectral and secondary electron image (SEI) data showed that soil-derived and sea-salt particles which had reacted or were mixed with SO 2 and NO x (or their acidic products) outnumbered the primary and "genuine" ones (59.2% vs. 19.2% in the stage 2 fraction and 41.3% vs. 9.9% in the stage 3 fraction). Moreover, particles containing nitrate in the secondary soil-derived species greatly outnumbered those containing sulfate. Organic particles, mainly consisting of marine biogenic species, were more abundant in the stage 2 fraction than in the stage 3 fraction (11.6% vs. 5.1%). Their relative abundance was greater than the sum of carbon-rich, K-containing, Fe-containing, and fly ash particles, which exhibited low frequencies in all the samples. In addition, many droplets rich in C, N, O, and S were observed. They tended to be small, exhibiting a dark round shape on SEI, and generally included 8-20 at.% C, 0-12 at.% N, 60-80 at.% O, and 4-10 at.% S (sometimes with <3 at.% Mg and Na). They were attributed to be a mixture of carbonaceous matter, H 2SO 4, and NH 4HSO 4/(NH 4) 2SO 4, mostly from the reaction of atmospheric SO 2 with NH 3 under high relative humidity. The analysis of the relationship between the aerosol particle compositions and 72-h backward air-mass trajectories suggests that ambient aerosols at Tokchok Island are strongly affected not only

  8. First identification in energetic particles of characteristic plasma boundaries at Mars and an account of various energetic particle populations close to the planet

    NASA Astrophysics Data System (ADS)

    McKenna-Lawlor, S. M. P.; Afonin, V.; Yeroshenko, Ye.; Keppler, E.; Kirsch, E.; Schwingenschuh, K.

    1993-05-01

    Signatures of characteristic boundaries, interpreted to be the bow shock and magnetopause with, between them, the magnetosheath, were recorded for the first time in energetic particles (between 30 keV and 3.2 MeV) in the downstream nightside Martian environment by the SLED instrument aboard Phobos 2. Also, energetic particles, interpreted to be oxygen ions, were recorded by SLED at four distinct locations close to Mars. These include (a) anisotropic fluxes at the terminator shocks with energies of up to at least 72 keV; (b) anisotropic fluxes with energies of up to at least 225 keV inside the magnetopause, at a height above the planet of approximately 900 km in the subsolar part of the magnetosphere; (c) fluxes with energies of up to at least 3.2 MeV in the flanks of the magnetosheath displaying quasi-periodic variations (period approximately 45 min) which are synchronous across the recorded energy spectrum and correlated in time with changes in the local magnetic field; and (d) beams of oxygen ions with energies of up to at least 55 keV traveling out along open field lines in the magnetotail with, in some cases, a suggestion of confinement close to the neutral sheet. A preliminary discussion is provided concerning the energization of the various populations of particles identified.

  9. Characteristics of tyre dust in polluted air: Studies by single particle mass spectrometry (ATOFMS)

    NASA Astrophysics Data System (ADS)

    Dall'Osto, Manuel; Beddows, David C. S.; Gietl, Johanna K.; Olatunbosun, Oluremi A.; Yang, Xiaoguang; Harrison, Roy M.

    2014-09-01

    There is a paucity of quantitative knowledge on the contributions of non-exhaust (abrasion and re-suspension) sources to traffic emissions. Abrasive emissions can be broadly categorised as tyre wear, brake wear and road dust/road surface wear. Current research often considers road dust and tyre dust as externally mixed particles, the former mainly composed of mineral matter and the latter solely composed of mainly organic matter and some trace elements. The aim of this work was to characterise tyre wear from both laboratory and field studies by using Aerosol Time-Of-Flight Mass Spectrometry (ATOFMS). Real-time single particle chemical composition was obtained from a set of rubber tyres rotating on a metal surface. Bimodal particle number size distributions peaking at 35 nm and 85 nm were obtained from SMPS/APS measurements over the range 6-20,000 nm. ATOFMS mass spectra of tyre wear in the particle size range 200-3000 nm diameter show peaks due to exo-sulphur compounds, nitrate, Zn and ions of high molecular weight (m/z > 100) attributed to organic polymers. Two large ATOFMS datasets collected from a number of outdoor studies were examined. The former was constituted of 48 road dust samples collected on the roads of London. The latter consisted of ATOFMS ambient air field studies from Europe, overall composed of more than 2,000,000 single particle mass spectra. The majority (95%) of tyre wear particles present in the road dust samples and atmospheric samples are internally mixed with metals (Li, Na, Ca, Fe, Ti), as well as phosphate. It is concluded that the interaction of tyres with the road surface creates particles internally mixed from two sources: tyre rubber and road surface materials. Measurements of the tyre rubber component alone may underestimate the contribution of tyre wear to concentrations of airborne particulate matter. The results presented are especially relevant for urban aerosol source apportionment and PM2.5 exposure assessment.

  10. The Roles of Transport and Wave-Particle Interactions on Radiation Belt Dynamics

    NASA Technical Reports Server (NTRS)

    Fok, Mei-Ching; Glocer, Alex; Zheng, Qiuhua

    2011-01-01

    Particle fluxes in the radiation belts can vary dramatically during geomagnetic active periods. Transport and wave-particle interactions are believed to be the two main types of mechanisms that control the radiation belt dynamics. Major transport processes include substorm dipolarization and injection, radial diffusion, convection, adiabatic acceleration and deceleration, and magnetopause shadowing. Energetic electrons and ions are also subjected to pitch-angle and energy diffusion when interact with plasma waves in the radiation belts. Important wave modes include whistler mode chorus waves, plasmaspheric hiss, electromagnetic ion cyclotron waves, and magnetosonic waves. We investigate the relative roles of transport and wave associated processes in radiation belt variations. Energetic electron fluxes during several storms are simulated using our Radiation Belt Environment (RBE) model. The model includes important transport and wave processes such as substorm dipolarization in global MHD fields, chorus waves, and plasmaspheric hiss. We discuss the effects of these competing processes at different phases of the storms and validate the results by comparison with satellite and ground-based observations. Keywords: Radiation Belts, Space Weather, Wave-Particle Interaction, Storm and Substorm

  11. Characteristics of new particle formation events in Nanjing, China: Effect of water-soluble ions

    NASA Astrophysics Data System (ADS)

    An, Junlin; Wang, Honglei; Shen, Lijuan; Zhu, Bin; Zou, Jianan; Gao, Jinhui; Kang, Hanqing

    2015-05-01

    New particle formation (NPF) events and water-soluble ions were studied at the meteorological building on the campus of the Nanjing University of Information Science and Technology (NUIST), which is located in the western part of the Yangtze River Delta (YRD). A wide-range particle spectrometer (WPS) provided particle number size distributions between 10 nm and 10 μm, whereas water-soluble ions for particles with diameters between 10 nm and 18 μm were measured using a 13-stage Nano-MOUDI aerosol sampler and 850 professional Ion Chromatography (IC). Additionally, meteorological data, trace gas concentrations and mass concentration were recorded. Ten NPF days were captured during the measurement period from 08 July to 02 August 2012. The mean aerosol number concentration, which was primarily composed of Aitken-mode particles, i.e., with diameters of 20-100 nm, was 13,664 cm-3, which was 1.9 times larger than that on non-NPF days. The results suggest that the NPF events were only slightly affected by O3, SO2, and NO2; the primary factors affecting NPF events were meteorological factors and air mass directions. NPF events were found to be favorable during the summer in the presence of high temperatures, strong radiation, low humidity, strong winds and clean air masses originating from the southeastern coast. The mean growth rate (GR), formation rate (J10), condensational sink (CS), condensing vapor rate (Q), and condensation vapor (C) were determined to be 7.6 nm h-1, 3.7 cm-3 s-1, 2.8 × 10-2 s-1, 2.9 × 106 cm-3 s-1, and 10.5 × 107 cm-3, respectively, on NPF days. The largest effects of the studied NPF events were on the mass and water-soluble ion concentrations of Aitken-mode particles, followed by nuclei-mode particles; few contributions to accumulation- and coarse-mode particles were observed. Different water-soluble ions were observed to have distinct interactions with the NPF events. The proportions of NH4+, SO42-, NO3-, K+ and Mg2+ in nuclei- and Aitken

  12. Role of engine age and lubricant chemistry on the characteristics of EGR soot

    NASA Astrophysics Data System (ADS)

    Adeniran, Olusanmi Adeniji

    Exhaust products of Diesel Engines serves as an environmental hazard, and to curtail this problem a Tier 3 emission standard was introduced which involves change in engine designs and introduction of EGR systems in Diesel engines. EGR systems, however has the challenge of generating soot which are abrasive and are major causes of wear in Diesel engines. This work has studied the characteristics of EGR soot formed in different range of engine age and in different lubricant chemistries of Mineral and Synthetic based diesel Oils. It is found that lubricant degradation is encouraged by less efficient combustion as engine age increases, and these are precursors to formation of crystalline and amorphous particles that are causes of wear in Diesel Engines. It is found that soot from new engine is dominated by calcium based crystals which are from calcium sulfonate detergent, which reduces formation of second phase particles that can be abrasive. Diversity and peak intensity is seen to increase in soot samples as engine age increases. This understanding of second phase particles formed in engines across age ranges can help in the durability development of engine, improvement of Oil formulation for EGR engines, and in development of chemistries for after-treatment Oil solutions that can combat formation of abrasive particles in Oils.

  13. Atmospheric new particle formation and the potential role of organic peroxides

    NASA Astrophysics Data System (ADS)

    Trawny, Katrin; Bonn, Boris; Jacobi, Stefan

    2010-05-01

    latter observation indicates a potential role of biogenic volatile organic compounds (VOCs) as their emission is strongly coupled to temperature. Because of our observations in the laboratory and beacuse of observed nighttime events, we approximated the concentration of different radicals, e.g. OH, HO2 and RO2. The values of RO2 and especially the ones of biogenic (e.g. terpene) origin showed a good correlation with new particle formation occurrence and seemed to be one essential point of several to allow new particle formation to occur. This might be an indication of the important role of the biosphere and its stress effects for the particle formation process. The seasonality observed for the time period since February 2008 displayed two maxima in May and August, September with a minimum in June, when the weather conditions were more humid and is in line with the observations made above. July and August displayed the higest HO2 concentrations, which will act as a sink for the organic peroxy radicals. In connection to the supressive effect of water vapour on terpene induced nucleating molecules (secondary ozonides) this might serve as an explanation for the commonly observed summer minimum in nucleation events.

  14. Exponential-characteristic spatial quadrature for discrete-ordinates neutral-particle transport in slab geometry. Master's thesis

    SciTech Connect

    Sjoden, G.E.

    1992-03-01

    A new discrete ordinates spatial quadrature scheme is presented for solving neutral particle transport problems. This new scheme, called the exponential characteristic method, is developed here in slab geometry with isotropic scattering. This method uses a characteristic integration of the Boltzmann transport equation with an exponential function as the assumed from of the source distribution, continuous across each spatial cell. The exponential source function is constructed to globally conserve zeroth and first spatial source moments and is non-negative. Characteristic integration ensures non-negative fluxes and flux moments. Numerical testing indicates that convergence of the exponential characteristic scheme is fourth order in the limit of vanishingly thin cells. Highly accurate solutions to optically thick problems can result using this scheme with very coarse meshes. Comparing accuracy and computational cost with existing spatial quadrature schemes (diamond difference, linear discontinuous, linear characteristic, linear adaptive, etc.), the exponential characteristic scheme typically performed best. This scheme is expected to be expandable to two dimensions in a straight forward manner. Due to the high accuracies achievable using coarse meshes, this scheme may allow researchers to obtain solutions to transport problems once thought too large or too difficult to be adequately solved conventional computer systems.

  15. The Role of Nuclear Fragmentation in Particle Therapy and Space Radiation Protection.

    PubMed

    Zeitlin, Cary; La Tessa, Chiara

    2016-01-01

    The transport of the so-called HZE particles (those having high charge, Z, and energy, E) through matter is crucially important both in space radiation protection and in the clinical setting where heavy ions are used for cancer treatment. HZE particles are usually considered those having Z > 1, though sometimes Z > 2 is meant. Transport physics is governed by two types of interactions, electromagnetic (ionization energy loss) and nuclear. Models of transport, such as those used in treatment planning and space mission planning must account for both effects in detail. The theory of electromagnetic interactions is well developed, but nucleus-nucleus collisions are so complex that no fundamental physical theory currently describes them. Instead, interaction models are generally anchored to experimental data, which in some areas are far from complete. The lack of fundamental physics knowledge introduces uncertainties in the calculations of exposures and their associated risks. These uncertainties are greatly compounded by the much larger uncertainties in biological response to HZE particles. In this article, we discuss the role of nucleus-nucleus interactions in heavy charged particle therapy and in deep space, where astronauts will receive a chronic low dose from galactic cosmic rays (GCRs) and potentially higher short-term doses from sporadic, unpredictable solar energetic particles (SEPs). GCRs include HZE particles; SEPs typically do not and we, therefore, exclude them from consideration in this article. Nucleus-nucleus collisions can result in the breakup of heavy ions into lighter ions. In space, this is generally beneficial because dose and dose equivalent are, on the whole, reduced in the process. The GCRs can be considered a radiation field with a significant high-LET component; when they pass through matter, the high-LET component is attenuated, at the cost of a slight increase in the low-LET component. Not only are the standard measures of risk

  16. The Role of Nuclear Fragmentation in Particle Therapy and Space Radiation Protection

    PubMed Central

    Zeitlin, Cary; La Tessa, Chiara

    2016-01-01

    The transport of the so-called HZE particles (those having high charge, Z, and energy, E) through matter is crucially important both in space radiation protection and in the clinical setting where heavy ions are used for cancer treatment. HZE particles are usually considered those having Z > 1, though sometimes Z > 2 is meant. Transport physics is governed by two types of interactions, electromagnetic (ionization energy loss) and nuclear. Models of transport, such as those used in treatment planning and space mission planning must account for both effects in detail. The theory of electromagnetic interactions is well developed, but nucleus–nucleus collisions are so complex that no fundamental physical theory currently describes them. Instead, interaction models are generally anchored to experimental data, which in some areas are far from complete. The lack of fundamental physics knowledge introduces uncertainties in the calculations of exposures and their associated risks. These uncertainties are greatly compounded by the much larger uncertainties in biological response to HZE particles. In this article, we discuss the role of nucleus–nucleus interactions in heavy charged particle therapy and in deep space, where astronauts will receive a chronic low dose from galactic cosmic rays (GCRs) and potentially higher short-term doses from sporadic, unpredictable solar energetic particles (SEPs). GCRs include HZE particles; SEPs typically do not and we, therefore, exclude them from consideration in this article. Nucleus–nucleus collisions can result in the breakup of heavy ions into lighter ions. In space, this is generally beneficial because dose and dose equivalent are, on the whole, reduced in the process. The GCRs can be considered a radiation field with a significant high-LET component; when they pass through matter, the high-LET component is attenuated, at the cost of a slight increase in the low-LET component. Not only are the standard measures of risk

  17. The Role of Cohesive Particle Interactions on Solids Uniformity and Mobilization During Jet Mixing: Testing Recommendations

    SciTech Connect

    Gauglitz, Phillip A.; Wells, Beric E.; Bamberger, Judith A.; Fort, James A.; Chun, Jaehun; Jenks, Jeromy WJ

    2010-04-01

    Radioactive waste that is currently stored in large underground tanks at the Hanford Site will be staged in selected double-shell tanks (DSTs) and then transferred to the Waste Treatment and Immobilization Plant (WTP). Before being transferred, the waste will be mixed, sampled, and characterized to determine if the waste composition and meets the waste feed specifications. Washington River Protection Solutions is conducting a Tank Mixing and Sampling Demonstration Program to determine the mixing effectiveness of the current baseline mixing system that uses two jet mixer pumps and the adequacy of the planned sampling method. The overall purpose of the demonstration program is to mitigate the technical risk associated with the mixing and sampling systems meeting the feed certification requirements for transferring waste to the WTP.The purpose of this report is to analyze existing data and evaluate whether scaled mixing tests with cohesive simulants are needed to meet the overall objectives of the small-scale mixing demonstration program. This evaluation will focus on estimating the role of cohesive particle interactions on various physical phenomena that occur in parts of the mixing process. A specific focus of the evaluation will be on the uniformity of suspended solids in the mixed region. Based on the evaluation presented in this report and the absence of definitive studies, the recommendation is to conduct scaled mixing tests with cohesive particles and augment the initial testing with non-cohesive particles. In addition, planning for the quantitative tests would benefit from having test results from some scoping experiments that would provide results on the general behavior when cohesive inter-particle forces are important.

  18. Ultrafine particles cause cytoskeletal dysfunctions in macrophages: role of intracellular calcium

    PubMed Central

    Möller, Winfried; Brown, David M; Kreyling, Wolfgang G; Stone, Vicki

    2005-01-01

    Background Particulate air pollution is reported to cause adverse health effects in susceptible individuals. Since most of these particles are derived form combustion processes, the primary composition product is carbon with a very small diameter (ultrafine, less than 100 nm in diameter). Besides the induction of reactive oxygen species and inflammation, ultrafine particles (UFP) can cause intracellular calcium transients and suppression of defense mechanisms of alveolar macrophages, such as impaired migration or phagocytosis. Methods In this study the role of intracellular calcium transients caused by UFP was studied on cytoskeleton related functions in J774A.1 macrophages. Different types of fine and ultrafine carbon black particles (CB and ufCB, respectively), such as elemental carbon (EC90), commercial carbon (Printex 90), diesel particulate matter (DEP) and urban dust (UD), were investigated. Phagosome transport mechanisms and mechanical cytoskeletal integrity were studied by cytomagnetometry and cell viability was studied by fluorescence microscopy. Macrophages were exposed in vitro with 100 and 320 μg UFP/ml/million cells for 4 hours in serum free medium. Calcium antagonists Verapamil, BAPTA-AM and W-7 were used to block calcium channels in the membrane, to chelate intracellular calcium or to inhibit the calmodulin signaling pathways, respectively. Results Impaired phagosome transport and increased cytoskeletal stiffness occurred at EC90 and P90 concentrations of 100 μg/ml/million cells and above, but not with DEP or UD. Verapamil and W-7, but not BAPTA-AM inhibited the cytoskeletal dysfunctions caused by EC90 or P90. Additionally the presence of 5% serum or 1% bovine serum albumin (BSA) suppressed the cytoskeletal dysfunctions. Cell viability showed similar results, where co-culture of ufCB together with Verapamil, W-7, FCS or BSA produced less cell dead compared to the particles only. PMID:16202162

  19. Heating Characteristics of Transformer Oil-Based Magnetic Fluids of Different Magnetic Particle Concentrations

    NASA Astrophysics Data System (ADS)

    Skumiel, A.; Hornowski, T.; Józefczak, A.

    2011-04-01

    The heating ability of mineral oil-based magnetic fluids with different magnetic particle concentrations is studied. The calorimetric measurements were carried out in an alternating magnetic field of 500 A · m-1 to 2500 A · m-1 amplitude and of 1500 kHz frequency. The revealed H n law-type dependence of the temperature increase rate, (d T/d t) t=0, on the amplitude of the magnetic field indicates the presence of superparamagnetic and partially ferromagnetic particles in the tested samples since n > 2. The specific absorption rate (SAR) defined as the rate of energy absorption per unit mass increases with a decrease of the volume fraction of the dispersed phase. This can be explained by the formation of aggregates in the samples with a higher concentration of magnetic particles.

  20. Cloud condensation nuclei characteristics of Asian dust particles over the western and central North Pacific

    NASA Astrophysics Data System (ADS)

    Uematsu, M.; Furutani, H.; Kawata, R.; Nakayama, H.

    2015-12-01

    Marine aerosols, such as sea salt particles, and sulfate and organic particles originated from marine biotas, exist in the marine atmosphere. Additionally, continental aerosols, such as dust and anthropogenic substances are transported over the open oceans. Variation of number concentration of cloud condensation nuclei (CCN) depends on the number-size distribution and chemical compositions of aerosols, and affects the lifetime and the reflectivity of clouds over the open oceans. During the R/V Hakuho Maru KH-12-1 cruise from Callao to Tokyo via Honolulu in the Pacific Ocean (23 January - 7 March 2012), aerosol number-size distribution and CCN number concentration were continuously measured, and the marine aerosols for chemical analysis were collected on shipboard. In the marine atmosphere over the Pacific, averaged aerosol total number concentration (TN) was 280 cm-3. Bimodal number-size distributions were observed frequently with peaks at 40-60 nm (Aitken mode) and 160-230 nm (accumulation mode). CCN concentrations were categorized by assuming three types of particles by chemical compositions (i.e., NaCl; a major component of sea salt particles, (NH4)2SO4; a sulfur oxide originated from the marine biotas, and Oxalic acid; a major component among organic carbon (OC) originated from the marine biotas). Activation Rate (AR), which is defined as the ratio of the number concentrations of CCN against TN, varied mainly because of the number-size distribution. Chemical composition was the factor that determined AR values. However, the AR variations caused by changes of the chemical composition were much smaller than those caused changes of the particle size distribution even when Asian dust were observed over the region on 27-29 February. During the long range transport, rapid coagulation among mineral dust, organics and sea salt particles may accelerate the gravitational setting of marine aerosols and supplies the terrestrial substances to the ocean environment.

  1. Characteristics of ultrafine particle sources and deposition rates in primary school classrooms

    NASA Astrophysics Data System (ADS)

    Laiman, Rusdin; He, Congrong; Mazaheri, Mandana; Clifford, Samuel; Salimi, Farhad; Crilley, Leigh R.; Megat Mokhtar, Megat Azman; Morawska, Lidia

    2014-09-01

    The aim of this work was to investigate changes in particle number concentration (PNC) within naturally ventilated primary school classrooms arising from local sources either within or adjacent to the classrooms. We quantify the rate at which ultrafine particles were emitted either from printing, grilling, heating or cleaning activities and the rate at which the particles were removed by both deposition and air exchange processes. At each of 25 schools in Brisbane, Australia, two weeks of measurements of PNC and CO2 were taken both outdoors and in the two classrooms. Bayesian regression modelling was employed in order to estimate the relevant rates and analyse the relationship between air exchange rate (AER), particle infiltration and the deposition rates of particle generated from indoor activities in the classrooms. During schooling hours, grilling events at the school tuckshop as well as heating and printing in the classrooms led to indoor PNCs being elevated by a factor of more than four, with emission rates of (2.51 ± 0.25) × 1011 p min-1, (8.99 ± 6.70) × 1011 p min-1 and (5.17 ± 2.00) × 1011 p min-1, respectively. During non-school hours, cleaning events elevated indoor PNC by a factor of above five, with an average emission rate of (2.09 ± 6.30) × 1011 p min-1. Particles were removed by both air exchange and deposition; chiefly by ventilation when AER > 0.7 h-1 and by deposition when AER < 0.7 h-1.

  2. Characteristics and settling behaviour of particles from blast furnace flue gas washing.

    PubMed

    Kiventerä, Jenni; Leiviskä, Tiina; Keski-Ruismäki, Kirsi; Tanskanen, Juha

    2016-05-01

    A lot of particles from iron-making are removed with blast furnace off-gas and routed to the gas cleaning system. As water is used for cleaning the gas, the produced wash water contains a large amount of particles such as valuable Fe and C. However, the presence of zinc prevents recycling. In addition, the high amount of calcium results in uncontrolled scaling. Therefore, the properties of the wash water from scrubber and sludge, from the Finnish metal industry (SSAB Raahe), were evaluated in this study. Size fractionation of wash water revealed that Fe, Zn, Al, Mn, V, Cr and Cd appeared mainly in the larger fractions (>1.2 μm) and Na, Mg, Si, Ni, K, Cu and As appeared mainly in the smaller fractions (<1.2 μm) or in dissolved form. Calcium was found both in the larger fractions and dissolved (∼60 mg/L). Most of the particles in wash water were included in the 1.2-10 μm particle size and were settled effectively. However, a clear benefit was observed when using a chemical to enhance particle settling. In comparison to 2.5 h of settling without chemical, the turbidity was further decreased by about 94%, iron 85% and zinc 50%. Coagulation-flocculation experiments indicated that both low and high molecular weight cationic polymers could provide excellent purification results in terms of turbidity. Calcium should be removed by other methods. The particles in sludge were mostly in the 2-4 μm or 10-20 μm fractions. Further sludge settling resulted in high solids removal. PMID:26945188

  3. Industry growth, work role characteristics, and job satisfaction: a cross-level mediation model.

    PubMed

    Ford, Michael T; Wooldridge, Jessica D

    2012-10-01

    The associations between industry revenue growth, individual work role characteristics, and job satisfaction were examined in this cross-level mediation analysis. Work roles were expected to be more autonomous, involve greater skill variety, and offer more opportunities for growth and development for workers in growing industries than for workers in declining industries. Supervisor support was also hypothesized to be stronger for workers in high-growth industries. Results from a nationally representative (U.S.) sample of service industry workers, using multilevel modeling, supported these propositions and suggest that job enrichment mediates relations between industry growth and job satisfaction. Associations between industry growth and autonomy were also stronger among workers in occupations that are less normatively autonomous, suggesting that industry growth fosters a weakening, and industry decline a strengthening, of traditional differences in autonomy across work roles. These results contribute to a multilevel perspective on organizational environments, individual work roles, and worker attitudes and well-being. PMID:22888860

  4. Evaluation of the role of a cationic surfactant on the flow characteristics of fly ash slurry.

    PubMed

    Naik, H K; Mishra, M K; Rao Karanam, U M; Deb, D

    2009-09-30

    Transportation of fly ash is a major problem in its efficient disposal. The main problem associated with fly ash transportation is that the particles settle down sooner than desired. The primary objective of this research is that not only the fly ash particles should remain floated till it reaches the end but also settle down after that. In this investigation the role of a drag-reducing cationic surfactant and a counter-ion has been evaluated to achieve the objectives. The experimental results show encouraging trends of surfactant helping fly ash particles to remain water-borne. The material exhibited Newtonian behavior. This paper describes these in term of shear rates, shear stress, temperature, concentration and viscosity. Rheological tests were conducted using Advanced Computerized Rheometer. Zeta potential was measured to test the stability of the colloidal fly ash particles using Malvern Zeta Sizer instrument. Surface tension was also measured to know the drag reduction behavior of the fly ash slurry by using Surface Tensiometer. The test results and flow diagrams were generated using Rheoplus software and are presented in this paper. Surfactant concentration of 0%, 0.1%, 0.2%, 0.3%, 0.4% and 0.5% by weight was mixed with equal amount of counter-ion and the slurry was prepared by adding fly ash with ordinary tap water to achieve the desired solid concentration of 20% (by weight). PMID:19345482

  5. The spatio-temporal characteristics of ULF waves driven by substorm injected particles

    NASA Astrophysics Data System (ADS)

    James, M. K.; Yeoman, T. K.; Mager, P. N.; Klimushkin, D. Yu.

    2013-04-01

    A previous case study observed a ULF wave with an eastward and equatorward phase propagation (an azimuthal wave number m, of ˜13) generated during the expansion phase of a substorm. The eastward phase propagation of the wave suggested that eastward drifting energetic electrons injected during the substorm were responsible for driving that particular wave. In this study, a population of 83 similar ULF wave events also associated with substorm-injected particles have been identified using multiple Super Dual Auroral Radar Network radars in Europe and North America between June 2000 and September 2005. The wave events identified in this study exhibit azimuthal wave numbers ranging in magnitude from 2 to 92, where the direction of propagation depends on the relative positions of the substorm onsets and the wave observations. We suggest that azimuthally drifting energetic particles associated with the substorms are responsible for driving the waves. Both westward drifting ions and eastward drifting electrons are implicated with energies ranging from ˜1 to 70 keV. A clear dependence of the particle energy on the azimuthal separation of the wave observations and the substorm onset is seen, with higher energy particles (leading to lower m-number waves) being involved at smaller azimuthal separations.

  6. The Spatio-temporal Characteristics of ULF Waves Driven by Substorm Injected Particles

    NASA Astrophysics Data System (ADS)

    James, M. K.; Yeoman, T. K.; Klimushkin, D. Y.; Mager, P. N.

    2012-12-01

    A previous case study [Yeoman et al.,2010] observed a ULF wave with an eastward and equatorward phase propagation (an azimuthal wave number m, of ~13) generated during the expansion phase of a substorm. The eastward phase propagation of the wave suggested that eastward drifting energetic electrons injected during the substorm were responsible for driving that particular wave. In this study a population of 84 similar ULF wave events also associated with substorm-injected particles have been identified using multiple SuperDARN radars in Europe and North America between June 2000 and September 2005. The wave events identified in this study exhibit azimuthal wave numbers ranging in magnitude from 2 to 92, where the direction of propagation depends on the relative positions of the substorm onsets and the wave observations. We suggest that azimuthally drifting energetic particles associated with the substorms are responsible for driving the waves, as suggested in Yeoman et al. [2010]. Both westward drifting ions and eastward drifting electrons are implicated with energies ranging from ~1 to 70 keV. A clear dependence of the particle energy on the azimuthal separation of the wave observations and the substorm onset is seen, with higher energy particles (leading to lower m-number waves) being involved at smaller azimuthal separations.

  7. [Light scattering extinction properties of atmospheric particle and pollution characteristics in hazy weather in Hangzhou].

    PubMed

    Xu, Chang; Ye, Hui; Shen, Jian-Dong; Sun, Hong-Liang; Hong, Sheng-Mao; Jiao, Li; Huang, Kan

    2014-12-01

    In order to evaluate the influence of particle scattering on visibility, light scattering coefficient, particle concentrations and meteorological factor were simultaneously monitored from July 2011 to June 2012 in Hangzhou. Daily scattering coefficients ranged from 108.4 to 1 098.1 Mm(-1), with an annual average concentration of 428.6 Mm(-1) ± 200.2 Mm(-1). Seasonal variation of scattering coefficients was significant, with the highest concentrations observed in autumn and winter and the lowest in summer. It was found there were two peaks for the average diurnal variations of the scattering coefficient, which could be observed at 08:00 and 21:00. The scattering efficiencies of PM2.5 and PM10 were 7.6 m2 x g(-1) and 4.4 m2 x g(-1), respectively. The particle scattering was about 90.2 percent of the total light extinction. The scattering coefficients were 684.4 Mm(-1) ± 218.1 Mm(-1) and 1 095.4 Mm(-1) ± 397.7 Mm(-1) in hazy and heavy hazy days, respectively, which were 2.6 and 4.2 times as high as in non-hazy weather, indicating that particle scattering is the main factor for visibility degradation and the occurrence of hazy weather in Hangzhou. PMID:25826909

  8. Mote cyclone robber system particulate emission factors for cotton gins: Particle size distribution characteristics

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This report is part of a project to characterize cotton gin emissions from the standpoint of total particulate stack sampling and particle size analyses. In 2013, the U.S. Environmental Protection Agency (EPA) published a more stringent standard for particulate matter with nominal diameter less than...

  9. Mote cleaner system particulate emission factors for cotton gins: Particle size distribution characteristics

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This report is part of a project to characterize cotton gin emissions from the standpoint of total particulate stack sampling and particle size analyses. In 2013, U.S. Environmental Protection Agency (EPA) published a more stringent standard for particulate matter with nominal diameter less than or ...

  10. EFFECTS OF SAMPLING NOZZLES ON THE PARTICLE COLLECTION CHARACTERISTICS OF INERTIAL SIZING DEVICES

    EPA Science Inventory

    In several particle-sizing samplers, the sample extraction nozzle is necessarily closely coupled to the first inertial sizing stage. Devices of this type include small sampling cyclones, right angle impactor precollectors for in-stack impactors, and the first impaction stage of s...

  11. Characteristics of nano-/ultrafine particle-bound PAHs in ambient air at an international airport.

    PubMed

    Lai, Chia-Hsiang; Chuang, Kuen-Yuan; Chang, Jin-Wei

    2013-03-01

    Concentrations of 22 polycyclic aromatic hydrocarbons (PAHs) were estimated for individual particle-size distributions at the airport apron of the Taipei International Airport, Taiwan, on 48 days in July, September, October, and December of 2011. In total, 672 integrated air samples were collected using a micro-orifice uniform deposition impactor (MOUDI) and a nano-MOUDI. Particle-bound PAHs (P-PAHs) were analyzed by gas chromatography with mass selective detector (GC/MSD). The five most abundant species of P-PAHs on all sampling days were naphthalene (NaP), phenanthrene (PA), fluoranthene (FL), acenaphthene (AcP), and pyrene (Pyr). Total P-PAHs concentrations were 152.21, 184.83, and 188.94 ng/m(3) in summer, autumn, and winter, respectively. On average, the most abundant fractions of benzo[a]pyrene equivalent concentration (BaPeq) in different molecular weights were high-weight PAHs (79.29 %), followed by medium-weight PAHs (11.57 %) and low-weight PAHs (9.14 %). The mean BaPeq concentrations were 1.25 and 0.94 (ng/m(3)) in ultrafine particles (<0.1 μm) and nano-particles (<0.032 μm), respectively. The percentages of total BaPeq in nano- and ultrafine particulate size ranges were 52.4 % and 70.15 %, respectively. PMID:22821344

  12. First stage lint cleaning system particulate emission factors for cotton gins: Particle size distribution characteristics

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This report is part of a project to characterize cotton gin emissions from the standpoint of total particulate stack sampling and particle size analyses. In 2006, Environmental Protection Agency (EPA) published a more stringent standard for particulate matter with nominal diameter less than or equal...

  13. Particle size distribution characteristics of cotton gin first stage mote system total particulate emissions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This report is part of a project to characterize cotton gin emissions from the standpoint of total particulate stack sampling and particle size analyses. In 2013, EPA published a more stringent standard for particulate matter with nominal diameter less than or equal to 2.5 µm (PM2.5). This created a...

  14. Mote trash system particulate emission factors for cotton gins: Particle size distribution characteristics

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This report is part of a project to characterize cotton gin emissions from the standpoint of total particulate stack sampling and particle size analyses. In 2013, the U.S. Environmental Protection Agency (EPA) published a more stringent standard for particulate matter with nominal diameter less than...

  15. Combined mote system particulate emission factors for cotton gins: Particle size distribution characteristics

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This report is part of a project to characterize cotton gin emissions from the standpoint of total particulate stack sampling and particle size analyses. In 2013, the Environmental Protection Agency (EPA) published a more stringent standard for particulate matter with nominal diameter less than or e...

  16. Overflow system particulate emission factors for cotton gins: Particle size distribution characteristics

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This report is part of a project to characterize cotton gin emissions from the standpoint of total particulate stack sampling and particle size analyses. In 2013, the U.S. Environmental Protection Agency (EPA) published a more stringent standard for particulate matter with nominal diameter less than...

  17. Combined lint cleaning system particulate emission factors for cotton gins: Particle size distribution characteristics

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This report is part of a project to characterize cotton gin emissions from the standpoint of total particulate stack sampling and particle size analyses. In 2013, the Environmental Protection Agency (EPA) published a more stringent standard for particulate matter with nominal diameter less than or e...

  18. Master trash system particulate emission factors for cotton gins: Particle size distribution characteristics

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This report is part of a project to characterize cotton gin emissions from the standpoint of total particulate stack sampling and particle size analyses. In 2013, U.S. Environmental Protection Agency (EPA) published a more stringent standard for particulate matter with nominal diameter less than or ...

  19. Chemical characteristics of Northeast Asian fly ash particles: Implications for their long-range transportation

    NASA Astrophysics Data System (ADS)

    Inoue, Jun; Momose, Azusa; Okudaira, Takamoto; Murakami-Kitase, Akiko; Yamazaki, Hideo; Yoshikawa, Shusaku

    2014-10-01

    The chemical compositions of fly ash particles emitted in Northeast Asia were studied to better understand the long-range transportation of atmospheric pollutants. We examined the compositions of spheroidal carbonaceous particles (SCPs), a type of fly ash from several to ˜20 μm in diameter found in surface sediments in or near the main industrial cities of Japan, China, South Korea, and Taiwan. SCPs from different countries were found to vary; SCPs from Japan and South Korea were characterized by low Ti/Si and high S/Si ratios, whereas SCPs in China exhibited high Ti/Si and low S/Si ratios and particles from Taiwan showed high Ti/Si and S/Si ratios. We also examined the SCPs found in remote islands in the Sea of Japan, at least 100 km from any industrial city. On the basis of their chemical compositions, these SCPs were classified as Japan and Korea, China, and Taiwan types using discriminant analysis. The results indicated that 30-50% of the particles found in these islands were assigned to the China type, suggesting that most of these SCPs were probably transported from Chinese industrial regions to these islands. It implies that even large particulate pollutants of ˜10 μm, such as SCPs, could be transported long distances of ˜1000 km.

  20. Battery condenser system particulate emission factors for cotton gins: Particle size distribution characteristics

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This report is part of a project to characterize cotton gin emissions from the standpoint of total particulate stack sampling and particle size analyses. In 2013, the Environmental Protection Agency (EPA) published a more stringent standard for particulate matter with nominal diameter less than or e...

  1. Particle size distribution characteristics of cotton gin battery condenser system total particulate emissions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This report is part of a project to characterize cotton gin emissions from the standpoint of total particulate stack sampling and particle size analyses. In 2013, EPA published a more stringent standard for particulate matter with nominal diameter less than or equal to 2.5 µm (PM2.5). This created a...

  2. CHARACTERISTICS OF INDIVIDUAL PARTICLES AT A RURAL SITE IN THE EASTERN UNITED STATES

    EPA Science Inventory

    To determine the nature of aerosol particles in a rural area of the eastern United States, aerosol samples were collected at Deep Creek Lake, Maryland, on various substrates and analyzed by a scanning electron microscope (SEM) and a transmission electron microscope (TEM). SEM ana...

  3. Particle size distribution characteristics of cotton gin unloading system total particulate emissions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This report is part of a project to characterize cotton gin emissions from the standpoint of total particulate stack sampling and particle size analyses. In 2013, EPA published a more stringent standard for particulate matter with nominal diameter less than or equal to 2.5 µm (PM2.5). This created a...

  4. Particle size distribution characteristics of cotton gin combined mote system total particulate emissions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This report is part of a project to characterize cotton gin emissions from the standpoint of total particulate stack sampling and particle size analyses. In 2013, EPA published a more stringent standard for particulate matter with nominal diameter less than or equal to 2.5 µm (PM2.5). This created a...

  5. Particle size distribution characteristics of cotton gin cyclone robber system total particulate emissions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This report is part of a project to characterize cotton gin emissions from the standpoint of total particulate stack sampling and particle size analyses. In 2013, EPA published a more stringent standard for particulate matter with nominal diameter less than or equal to 2.5 µm (PM2.5). This created a...

  6. Particle size distribution characteristics of cotton gin overflow system total particulate emissions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This report is part of a project to characterize cotton gin emissions from the standpoint of total particulate stack sampling and particle size analyses. In 2013, EPA published a more stringent standard for particulate matter with nominal diameter less than or equal to 2.5 µm (PM2.5). This created a...

  7. Particle size distribution characteristics of cotton gin second stage lint cleaning system total particulate emissions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This report is part of a project to characterize cotton gin emissions from the standpoint of total particulate stack sampling and particle size analyses. In 2013, EPA published a more stringent standard for particulate matter with nominal diameter less than or equal to 2.5 µm (PM2.5). This created a...

  8. Particle size distribution characteristics of cotton gin mote cyclone robber system total particulate emissions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This report is part of a project to characterize cotton gin emissions from the standpoint of total particulate stack sampling and particle size analyses. In 2013, EPA published a more stringent standard for particulate matter with nominal diameter less than or equal to 2.5 µm (PM2.5). This created a...

  9. Particle size distribution characteristics of cotton gin master trash system total particulate emissions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This report is part of a project to characterize cotton gin emissions from the standpoint of total particulate stack sampling and particle size analyses. In 2013, EPA published a more stringent standard for particulate matter with nominal diameter less than or equal to 2.5 µm (PM2.5). This created a...

  10. Particle size distribution characteristics of cotton gin second stage mote system total particulate emissions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This report is part of a project to characterize cotton gin emissions from the standpoint of total particulate stack sampling and particle size analyses. In 2013, EPA published a more stringent standard for particulate matter with nominal diameter less than or equal to 2.5 µm (PM2.5). This created a...

  11. Particle size distribution characteristics of cotton gin mote trash system total particulate emissions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This report is part of a project to characterize cotton gin emissions from the standpoint of total particulate stack sampling and particle size analyses. In 2013, EPA published a more stringent standard for particulate matter with nominal diameter less than or equal to 2.5 µm (PM2.5). This created a...

  12. Particle size distribution characteristics of cotton gin mote cleaner system total particulate emissions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This report is part of a project to characterize cotton gin emissions from the standpoint of total particulate stack sampling and particle size analyses. In 2013, EPA published a more stringent standard for particulate matter with nominal diameter less than or equal to 2.5 µm (PM2.5). This created a...

  13. Particle size distribution characteristics of cotton gin combined lint cleaning system total particulate emissions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This report is part of a project to characterize cotton gin emissions from the standpoint of total particulate stack sampling and particle size analyses. In 2013, EPA published a more stringent standard for particulate matter with nominal diameter less than or equal to 2.5 µm (PM2.5). This created a...

  14. Performance of Combination Drug and Hygroscopic Excipient Submicrometer Particles from a Softmist Inhaler in a Characteristic Model of the Airways

    PubMed Central

    Longest, P. Worth; Tian, Geng; Li, Xiang; Son, Yoen-Ju; Hindle, Michael

    2012-01-01

    Excipient enhanced growth (EEG) of inhaled submicrometer pharmaceutical aerosols is a recently proposed method intended to significantly reduce extrathoracic deposition and improve lung delivery. The objective of this study was to evaluate the size increase of combination drug and hygroscopic excipient particles in a characteristic model of the airways during inhalation using both in vitro experiments and CFD simulations. The airway model included a characteristic mouth-throat (MT) and upper tracheobronchial (TB) region through the third bifurcation (B3) and was enclosed in a chamber geometry used to simulate the thermodynamic conditions of the lungs. Both in vitro results and CFD simulations were in close agreement and indicated that EEG delivery of combination submicrometer particles could nearly eliminate MT deposition for inhaled pharmaceutical aerosols. Compared with current inhalers, the proposed delivery approach represents a 1–2 order of magnitude reduction in MT deposition. Transient inhalation was found to influence the final size of the aerosol based on changes in residence times and relative humidity values. Aerosol sizes following EEG when exiting the chamber (2.75–4.61 μm) for all cases of initial submicrometer combination particles were equivalent to or larger than many conventional pharmaceutical aerosols that frequently have MMADs in the range of 2–3 μm. PMID:22820981

  15. Single particle tracking in systems showing anomalous diffusion: the role of weak ergodicity breaking.

    PubMed

    Burov, Stas; Jeon, Jae-Hyung; Metzler, Ralf; Barkai, Eli

    2011-02-01

    Anomalous diffusion has been widely observed by single particle tracking microscopy in complex systems such as biological cells. The resulting time series are usually evaluated in terms of time averages. Often anomalous diffusion is connected with non-ergodic behaviour. In such cases the time averages remain random variables and hence irreproducible. Here we present a detailed analysis of the time averaged mean squared displacement for systems governed by anomalous diffusion, considering both unconfined and restricted (corralled) motion. We discuss the behaviour of the time averaged mean squared displacement for two prominent stochastic processes, namely, continuous time random walks and fractional Brownian motion. We also study the distribution of the time averaged mean squared displacement around its ensemble mean, and show that this distribution preserves typical process characteristics even for short time series. Recently, velocity correlation functions were suggested to distinguish between these processes. We here present analytical expressions for the velocity correlation functions. The knowledge of the results presented here is expected to be relevant for the correct interpretation of single particle trajectory data in complex systems. PMID:21203639

  16. Investigations on particle surface characteristics vs. dispersion behaviour of L-leucine coated carrier-free inhalable powders.

    PubMed

    Raula, Janne; Thielmann, Frank; Naderi, Majid; Lehto, Vesa-Pekka; Kauppinen, Esko I

    2010-01-29

    Aerosol microparticles of salbutamol sulphate are gas-phase coated with an amino acid L-leucine. Depending of the saturated state of L-leucine, the coating is formed by the surface diffusion of L-leucine molecules within a droplet or by the physical vapour deposition (PVD) of L-leucine or by the combination thereof. The PVD coated particles showed excellent aerosolization characteristics in a carrier-free powder delivery from an inhaler. The aerosolization of the fine powders is compared with surface energy parameters analysed by inverse gas chromatography (IGC). The dispersion testing is conducted by a Inhalation Simulator using a fast inhalation profile with inhalation flow rate of 67 l min(-1). It is found that the powder emission is affected by the morphology, surface roughness (asperity size and density) of the particles and acidity of particle surface. The latter affects the dispersion and dose repeatability of fine powder in a case if L-leucine content is high enough. However, there is no direct correlation between dispersive surface energies and aerosolization performances of the powders. Crucial factors for the improved aerosolization rely weakly on surface acid-base properties but strongly on particle morphology and fine-scale surface roughness. PMID:19879344

  17. Role of nuclear deformations and proximity interactions in heavy particle radioactivity

    NASA Astrophysics Data System (ADS)

    Sawhney, Gudveen; Sandhu, Kirandeep; Sharma, Manoj K.; Gupta, Raj K.

    2014-11-01

    Based on the preformed cluster model (PCM), we have extended our earlier study on cluster decays of heavy parent nuclei to analyze the effects of different nuclear proximity potentials in the ground-state clusterization of superheavy nuclei with Z = 113, 115 and 117. In order to look for the possible role of deformations, calculations are performed for spherical as well as β 2-deformed choices of fragmentation. The relevance of "hot compact" over "cold elongated" configurations due to orientations is also explored, in addition to the role of Q value and angular momentum ℓ effects. As the PCM is based on collective clusterization picture, the preformation and penetration probabilities get modified considerably, and hence do so the decay constants and half-lives of the clusters, with the use of different nuclear proximity potentials. The comparative importance of nuclear proximity potentials Prox-1977 and Prox-2000 is analyzed and the calculated decay half-lives in the framework of PCM are compared with the recent predictions of the analytical super-asymmetric fission model (ASAFM). The possible role of shell corrections is also investigated for understanding the dynamics of heavy particle radioactivity. Finally, the potential energy surfaces are compared for different proton and neutron magic numbers in superheavy mass region.

  18. On the role of local CIR-associated particle acceleration in formation of time-intensity profiles of suprathermal particle fluxes

    NASA Astrophysics Data System (ADS)

    Khabarova, Olga; Malandraki, Olga E.

    2015-04-01

    A possibility of local acceleration of particles up to several MeV at the edge of corotating interaction regions (CIRs) in the solar wind is discussed. Recently, evidence for significant local particle energization due to magnetic reconnection that occurs at the heliospheric current sheet (HCS) and followed by consequent trapping and re-acceleration of suprathermal particles in magnetic islands surrounding the rippled HCS was provided (Khabarova et al. 2014). We investigate this phenomenon in application to particle energization at current sheets of various scales (from the HCS to local small-scale current sheets), including current sheets frequently observed at the edge of CIRs, and explore the role of magnetic islands in the picture of suprathermal particle flux enhancements associated with CIRs. It is commonly believed that CIRs serve as one of the sources of suprathermal particles at the Earth's orbit in addition to flares and pre-CME shocks because of particle acceleration by reverse shocks formed beyond 2-3AU. However, this paradigm demands a free way of particles back from the shocks to 1 AU, which produces specific timing and ion/electron flux features that are not observed every time. We suggest that local particle acceleration may take place directly at the CIR edge in the case of the HCS-CIR interaction, as well as be determined by the occurrence of electric field in merging/contracting magnetic islands and local reconnecting current sheets (Zank et al. 2014) in the turbulent plasma of CIRs. Multi-spacecraft data analysis (STEREO, Wind, ACE and Ulysses) is performed. Khabarova O., Zank G.P., Li G., le Roux J.A., Webb G.M., Dosch A., Zharkova V.V. and Malandraki O.E., Small-scale magnetic islands in the solar wind and their role in particle acceleration. Part 1: Dynamics of magnetic islands near the heliospheric current sheet. Submitted to ApJ, 2014 Zank G.P., le Roux J.A., Webb G.M., Dosch A., and O. Khabarova. Particle acceleration via reconnection

  19. Estimating Bacteria Emissions from Inversion of Atmospheric Transport: Sensitivity to Modelled Particle Characteristics

    SciTech Connect

    Burrows, Susannah M.; Rayner, Perter; Butler, T.; Lawrence, M.

    2013-06-04

    Model-simulated transport of atmospheric trace components can be combined with observed concentrations to obtain estimates of ground-based sources using various inversion techniques. These approaches have been applied in the past primarily to obtain source estimates for long-lived trace gases such as CO2. We consider the application of similar techniques to source estimation for atmospheric aerosols, by using as a case study the estimation of bacteria emissions from different ecosystem regions in the global atmospheric chemistry and climate model ECHAM5/MESSy-Atmospheric Chemistry (EMAC). Simulated particle concentrations in the tropopause region and at high latitudes, as well as transport of particles to tundra and land ice regions are shown to be highly sensitive to scavenging in mixed-phase clouds, which is poorly characterized in most global climate models. This may be a critical uncertainty in correctly simulating the transport of aerosol particles to the Arctic. Source estimation via Monte Carlo Markov Chain is applied to a suite of sensitivity simulations and the global mean emissions are estimated. We present an analysis of the partitioning of uncertainties in the global mean emissions that are attributable to particle size, CCN activity, the ice nucleation scavenging ratios for mixed-phase and cold clouds, and measurement error. Uncertainty due to CCN activity or to a 1 um error in particle size is typically between 10% and 40% of the uncertainty due to data uncertainty, as measured by the 5%-ile to 95%-ile range of the Monte Carlo ensemble. Uncertainty attributable to the ice nucleation scavenging ratio in mized-phase clouds is as high as 10% to 20% of the data uncertainty. Taken together, the four model 20 parameters examined contribute about half as much to the uncertainty in the estimated emissions as do the measurements. This was a surprisingly large contribution from model uncertainty in light of the substantial data uncertainty, which ranges from 81

  20. Exponential characteristic spatial quadrature for discrete ordinates neutral particle transport in two-dimensional cartesian coordinates. Doctoral thesis

    SciTech Connect

    Minor, B.M.

    1993-09-01

    The exponential characteristic spatial quadrature for discrete ordinates neutral particle transport with rectangular cells is developed. Numerical problems arising in the derivation required the development of exponential moment functions. These functions are used to remove indeterminant forms which can cause catastrophic cancellations. The EC method is positive and nonlinear. It conserves particles and satisfies first moment balance. Comparisons of the EC method's performance to other methods in optically thin and thick spatial cells were performed. For optically thin cells, the EC method was shown to converge to the correct answer, with third order truncation error in the thin cell limit. In deep penetration problems, the EC method attained its highest computational efficiencies compared to the other methods. For all the deep penetration problems examined, the number of spatial cells required by the EC method to attain a desired accuracy was less than the other methods.... Mathematics functions, Nuclear radiation, Nuclear engineering, Radiation attenuation, Radiation shielding, Transport theory, Radiation transport.

  1. Quality Characteristics and Ginsenosides Composition of Ginseng-Yakju According to the Particle Size of Ginseng Powder

    PubMed Central

    Lee, Je-Hyuk; Choi, Kang Hyun; Sohn, Eun-Hwa; Jang, Ki-Hyo

    2013-01-01

    The aim of this study was to develop rice wine (Yakju) containing various amounts and particle sizes of ginseng powder and to analyze the physicochemical characteristics and content of ginsenosides in ginseng-Yakju. Soluble solid content, pH, ethanol concentration, acidity, amino acid content, and evaluation of preference showed no difference between four kinds of Yakju groups, regardless of ginseng supplementation and particle size of the ginseng powder. During fermentation of Yakju containing ginseng, the contents of ginsenosides Rb1, Rb2, Rb3, and Rc were decreased. Otherwise, the content of ginsenoside Rh1 was increased highly by brewing microorganisms in Yakju. Recovery ratios of ginsenosides in ginseng-Yakju were approximately 25.4% (coarse ginseng power) and 23.8% (fine ginseng powder), which were superior to the recovery ratio of ginsenosides in Yakju containing ginseng slices (5%). PMID:24551824

  2. Structural, electrical and magnetic characteristics of nickel substituted cobalt ferrite nano particles, synthesized by self combustion method

    NASA Astrophysics Data System (ADS)

    Sontu, Uday Bhasker; Yelasani, Vijayakumar; Musugu, Venkata Ramana Reddy

    2015-01-01

    Nickel-substituted cobalt ferrite nano-particles are synthesized using a self-combustion method. Aqueous metal nitrates and citric acid form the precursors. No external oxidizing agents are used to change the pH of the precursors; this resulted in a more environment friendly synthesis. Structural, magnetic and electrical characteristics of the nano ferrites are verified using X-ray diffractometer (XRD), VSM and impedance analyzer respectively. Phase formation, particle size, lattice parameter, X-ray density, saturation magnetization, coercivity, dielectric constant and electrical activation energy as function of nickel substitution in cobalt ferrite are studied. It is shown here that the magnetic and electrical properties can be tuned by varying the nickel concentration.

  3. Point particle binary system with components of different masses in the linear regime of the characteristic formulation of general relativity

    NASA Astrophysics Data System (ADS)

    Cedeño M, C. E.; de Araujo, J. C. N.

    2016-05-01

    A study of binary systems composed of two point particles with different masses in the linear regime of the characteristic formulation of general relativity with a Minkowski background is provided. The present paper generalizes a previous study by Bishop et al. The boundary conditions at the world tubes generated by the particles's orbits are explored, where the metric variables are decomposed in spin-weighted spherical harmonics. The power lost by the emission of gravitational waves is computed using the Bondi News function. The power found is the well-known result obtained by Peters and Mathews using a different approach. This agreement validates the approach considered here. Several multipole term contributions to the gravitational radiation field are also shown.

  4. Computational methods for analyzing the transmission characteristics of a beta particle magnetic analysis system

    NASA Technical Reports Server (NTRS)

    Singh, J. J.

    1979-01-01

    Computational methods were developed to study the trajectories of beta particles (positrons) through a magnetic analysis system as a function of the spatial distribution of the radionuclides in the beta source, size and shape of the source collimator, and the strength of the analyzer magnetic field. On the basis of these methods, the particle flux, their energy spectrum, and source-to-target transit times have been calculated for Na-22 positrons as a function of the analyzer magnetic field and the size and location of the target. These data are in studies requiring parallel beams of positrons of uniform energy such as measurement of the moisture distribution in composite materials. Computer programs for obtaining various trajectories are included.

  5. Mechanical characteristics of SiC coating layer in TRISO fuel particles

    SciTech Connect

    Hosemann, Peter; Martos, J. N.; Frazer, D.; Vasudevamurthy, Gokul; Byun, Thak Sang; Hunn, John D; Jolly, Brian C; Terrani, Kurt A; Okuniewski, Maria A.

    2013-01-01

    Tristructural isotropic (TRISO) particles are considered as advanced fuel forms for a variety of fission platforms. While these fuel structures have been tested and deployed in reactors, the mechanical properties of these structures as a function of production parameters need to be investigated in order to ensure their reliability during service. Nanoindentation techniques, indentation crack testing, and half sphere crush testing were utilized in order to evaluate the integrity of the SiC coating layer that is meant to prevent fission product release in the coated particle fuel form. The results are complimented by scanning electron microscopy (SEM) of the grain structure that is subject to change as a function of processing parameters and can alter the mechanical properties such as hardness, elastic modulus, fracture toughness and fracture strength. Through utilization of these advanced techniques, subtle differences in mechanical properties that can be important for in-pile fuel performance can be distinguished and optimized in iteration with processing science of coated fuel particle production.

  6. Rheological and flow characteristics of nanofluids: Influence of electroviscous effects and particle agglomeration

    NASA Astrophysics Data System (ADS)

    Anoop, K. B.; Kabelac, S.; Sundararajan, T.; Das, Sarit K.

    2009-08-01

    Nanofluids have shown remarkable attraction in heat transfer community due to its reported enhanced thermal properties. One factor which can restrict nanofluids in heat transfer application is the increased viscosity value (compared to classical predictions). Particle aggregation occurring was the major reason for this observation. Even though majority of the aqueous nanofluids prepared in literature were stabilized electrostatically by adjusting the pH, studies on the effect of the electrical double layer thus created and its influence on viscosity increase has not been investigated for these nanofluids so far. Thus, in the present paper, rheological properties of alumina-water nanofluids, which are electrostatically stabilized, are measured and the increase in suspension viscosity due to presence of this electrical double layer causing additional electroviscous effects is brought out. Based on dynamic light scattering studies, particle agglomeration and its subsequent effect in increasing the viscosity of alumina-ethylene glycol nanofluid, where electroviscous effects are absent, are also considered. It is noted that the understanding of electroviscous effect is equally important as understanding the particle agglomeration effect and understanding both the effects is central to revealing the physics of nanofluid rheology. Further, hydrodynamic experiments are made, which show that nanofluids behaves almost like a homogeneous fluids under flow conditions, and by knowing their properties, such as viscosity and density, pressure drop can be predicted.

  7. Mechanical Characteristics of SiC Coating Layer in TRISO Fuel Particles

    SciTech Connect

    P. Hosemann; J. N. Martos; D. Frazer; G. Vasudevamurthy; T. S. Byun; J. D. Hunn; B. C. Jolly; K. Terrani; M. Okuniewski

    2013-11-01

    Tristructural isotropic (TRISO) particles are considered as advanced fuel forms for a variety of fission platforms. While these fuel structures have been tested and deployed in reactors, the mechanical properties of these structures as a function of production parameters need to be investigated in order to ensure their reliability during service. Nanoindentation techniques, indentation crack testing, and half sphere crush testing were utilized in order to evaluate the integrity of the SiC coating layer that is meant to prevent fission product release in the coated particle fuel form. The results are complimented by scanning electron microscopy (SEM) of the grain structure that is subject to change as a function of processing parameters and can alter the mechanical properties such as hardness, elastic modulus, fracture toughness and fracture strength. Through utilization of these advanced techniques, subtle differences in mechanical properties that can be important for in-pile fuel performance can be distinguished and optimized in iteration with processing science of coated fuel particle production.

  8. Fluid-particle characteristics in fully-developed cluster-induced turbulence

    NASA Astrophysics Data System (ADS)

    Capecelatro, Jesse; Desjardins, Olivier; Fox, Rodney

    2014-11-01

    In this study, we present a theoretical framework for collisional fluid-particle turbulence. To identify the key mechanisms responsible for energy exchange between the two phases, an Eulerian-Lagrangian strategy is used to simulate fully-developed cluster-inudced turbulence (CIT) under a range of Reynolds numbers, where fluctuations in particle concentration generate and sustain the carrier-phase turbulence. Using a novel filtering approach, a length-scale separation between the correlated particle velocity and uncorrelated granular temperature (GT) is achieved. This separation allows us to extract the instantaneous Eulerian volume fraction, velocity and GT fields from the Lagrangian data. Direct comparisons can thus be made with the relevant terms that appear in the multiphase turbulence model. It is shown that the granular pressure is highly anisotropic, and thus additional transport equations (as opposed to a single equation for GT) are necessary in formulating a predictive multiphase turbulence model. In addition to reporting the relevant contributions to the Reynolds stresses of each phase, two-point statistics, integral length/timescales, averages conditioned on the local volume fraction, and PDFs of the key multiphase statistics are presented and discussed. The research reported in this paper is partially supported by the HPC equipment purchased through U.S. National Science Foundation MRI Grant Number CNS 1229081 and CRI Grant Number 1205413.

  9. Cytokine expression in mice exposed to diesel exhaust particles by inhalation. Role of tumor necrosis factor

    PubMed Central

    Saber, Anne T; Jacobsen, Nicklas R; Bornholdt, Jette; Kjær, Sanna L; Dybdahl, Marianne; Risom, Lotte; Loft, Steffen; Vogel, Ulla; Wallin, Håkan

    2006-01-01

    Background Particulate air pollution has been associated with lung and cardiovascular disease, for which lung inflammation may be a driving mechanism. The pro-inflammatory cytokine, tumor necrosis factor (TNF) has been suggested to have a key-role in particle-induced inflammation. We studied the time course of gene expression of inflammatory markers in the lungs of wild type mice and Tnf-/- mice after exposure to diesel exhaust particles (DEPs). Mice were exposed to either a single or multiple doses of DEP by inhalation. We measured the mRNA level of the cytokines Tnf and interleukin-6 (Il-6) and the chemokines, monocyte chemoattractant protein (Mcp-1), macrophage inflammatory protein-2 (Mip-2) and keratinocyte derived chemokine (Kc) in the lung tissue at different time points after exposure. Results Tnf mRNA expression levels increased late after DEP-inhalation, whereas the expression levels of Il-6, Mcp-1 and Kc increased early. The expression of Mip-2 was independent of TNF if the dose was above a certain level. The expression levels of the cytokines Kc, Mcp-1 and Il-6, were increased in the absence of TNF. Conclusion Our data demonstrate that Tnf is not important in early DEP induced inflammation and rather exerts negative influence on Mcp-1 and Kc mRNA levels. This suggests that other signalling pathways are important, a candidate being one involving Mcp-1. PMID:16504008

  10. Growth of new particle in less and highly polluted atmosphere: Implication for an important role of NH4NO3 in growing new particles to CCN size

    NASA Astrophysics Data System (ADS)

    Zhu, Y.; Gao, H.; Duan, Z. Q.; Evans, G. J.; Yao, X.

    2013-12-01

    When new particles formed in the atmosphere grow over 50-80 nm, they will activate as cloud condensation nuclei (CCN) and lead to an increase of cloud albedo. Knowledge gaps still existed, e.g., 1) new particles under which conditions can grow to CCN size? 2) which chemicals determine the growth of new particles to CCN size? In this study, new particle formation (NPF) events were investigated at two urban sites, in Qingdao during 23 April and 31 May, 2010, and in Toronto during 1 May and 31 May, 2009, using two identical Fast Mobility Particle Sizer (FMPS). Based on the satellite column densities of air pollutants and the particulate chemical concentration in PM2.5, the site in Qingdao suffered severe air pollution while the site in Toronto is less polluted. NPF events were observed in 16 days out of 39 sampling days in Qingdao and 13 days out of 31 sampling days in Toronto. The occurrence frequency of NPF events between Qingdao (41%) and Toronto (42%) was comparable to each other. In Qingdao, the geometric mean diameter of grown nucleated particles (Dpg,i) in 15 days grew to larger than 40 nm except in one day when the growth of new particles terminated at ~20 nm. In addition, the Dpg,i in 8 days out of the 15 days grew over 50 nm and it reached ~100 nm in two days. Two-phase growth of new particles was generally observed in these NPF events of Qingdao. The first-phase growth occurred in daytime and the CMAQ modeling results showed that formation of secondary organics was likely an important cause for the growth. The second-phase growth was observed at night and was associated with the increased concentrations of NH4+ and NO3-, implying that NH4NO3 condensation played an important role in the growth. In Toronto, NPF events in 4 days followed with the growth of new particles <~20 nm while new particles grew up to ~40 nm in the remaining NPF events. A slight growth of new particles at night was observed only in 3-day NPF events when the increased concentrations of

  11. Role of the substrate in the electrical transport characteristics of focused ion beam fabricated nanogap electrode

    NASA Astrophysics Data System (ADS)

    Rajput, Nitul S.; Singh, Abhishek K.; Verma, H. C.

    2012-07-01

    Precise metallic nanogap structure is fabricated on a glass substrate by using a 30 keV focused Ga ion beam. While investigating the I-V behavior of the nanogap structure, tunneling through the substrate has been found to play a vital role in the electrical transportation process. Substrate breakdown occurs at a certain applied voltage and a metal vapor state is initiated through intense heat generation at the nanogap region. The experimental observation confirms the role of the substrate in the explosion process. Metallic spherical particles are formed during cooling/condensation of the metal vapors or splashing of the liquid droplets showing a wide distribution of size from few tens of nanometers to few microns.

  12. Characteristics of water-soluble ions and carbon in fine and coarse particles collected near an open burning site

    NASA Astrophysics Data System (ADS)

    Lin, Chih-Chung; Huang, Kuo-Lin; Tsai, Jen-Hsiung; Lee, Wen-Jhy; Chen, Shui-Jen; Lin, Shao-Kai

    2012-05-01

    This study investigates the chemical characteristics of particles that were collected from the open burning of wax apple agricultural waste, and evaluates the impact of such burning on regional air quality. The water-soluble ions, elemental carbon (EC), and organic carbon (OC) in fine (Dp ≤ 2.5 μm) and coarse (2.5 < Dp ≤ 10 μm) particles were collected using a micro-orifice uniform deposition impactor (MOUDI) and two Dichot samplers. The average PM2.5/PM10 ratio during open burning (0.90) was higher than those both before and after burning (0.57 and 0.55, respectively). The particle distributions before and during burning were bi-modal and uni-modal, respectively. During the open burning, the OC or K+ content markedly increased; however, that of secondary aerosol (NH4+, NO3- and SO42-) decreased. The Na+/Cl- molar ratios of fine particles before, after, and during the open burning 0.40, 0.18, and 0.24, respectively; however, the corresponding (Na+ + K+)/Cl- molar ratios were 0.74, 0.99, and 0.39, respectively. OC, K+ and Cl- were quite abundant in the open burning of agricultural waste (wax apple), and the OC/Na+, K+/Na+, and Cl-/Na+ (mass) ratios in fine particles (318, 10.2, and 10.5, respectively) may be used as reference indexes associated with the open burning of wax apple waste.

  13. Small-scale Magnetic Islands in the Solar Wind and Their Role in Particle Acceleration. II. Particle Energization inside Magnetically Confined Cavities

    NASA Astrophysics Data System (ADS)

    Khabarova, Olga V.; Zank, Gary P.; Li, Gang; Malandraki, Olga E.; le Roux, Jakobus A.; Webb, Gary M.

    2016-08-01

    We explore the role of heliospheric magnetic field configurations and conditions that favor the generation and confinement of small-scale magnetic islands associated with atypical energetic particle events (AEPEs) in the solar wind. Some AEPEs do not align with standard particle acceleration mechanisms, such as flare-related or simple diffusive shock acceleration processes related to interplanetary coronal mass ejections (ICMEs) and corotating interaction regions (CIRs). As we have shown recently, energetic particle flux enhancements may well originate locally and can be explained by particle acceleration in regions filled with small-scale magnetic islands with a typical width of ∼0.01 au or less, which is often observed near the heliospheric current sheet (HCS). The particle energization is a consequence of magnetic reconnection-related processes in islands experiencing either merging or contraction, observed, for example, in HCS ripples. Here we provide more observations that support the idea and the theory of particle energization produced by small-scale-flux-rope dynamics (Zank et al. and Le Roux et al.). If the particles are pre-accelerated to keV energies via classical mechanisms, they may be additionally accelerated up to 1–1.5 MeV inside magnetically confined cavities of various origins. The magnetic cavities, formed by current sheets, may occur at the interface of different streams such as CIRs and ICMEs or ICMEs and coronal hole flows. They may also form during the HCS interaction with interplanetary shocks (ISs) or CIRs/ICMEs. Particle acceleration inside magnetic cavities may explain puzzling AEPEs occurring far beyond ISs, within ICMEs, before approaching CIRs as well as between CIRs.

  14. Small-scale Magnetic Islands in the Solar Wind and Their Role in Particle Acceleration. II. Particle Energization inside Magnetically Confined Cavities

    NASA Astrophysics Data System (ADS)

    Khabarova, Olga V.; Zank, Gary P.; Li, Gang; Malandraki, Olga E.; le Roux, Jakobus A.; Webb, Gary M.

    2016-08-01

    We explore the role of heliospheric magnetic field configurations and conditions that favor the generation and confinement of small-scale magnetic islands associated with atypical energetic particle events (AEPEs) in the solar wind. Some AEPEs do not align with standard particle acceleration mechanisms, such as flare-related or simple diffusive shock acceleration processes related to interplanetary coronal mass ejections (ICMEs) and corotating interaction regions (CIRs). As we have shown recently, energetic particle flux enhancements may well originate locally and can be explained by particle acceleration in regions filled with small-scale magnetic islands with a typical width of ˜0.01 au or less, which is often observed near the heliospheric current sheet (HCS). The particle energization is a consequence of magnetic reconnection-related processes in islands experiencing either merging or contraction, observed, for example, in HCS ripples. Here we provide more observations that support the idea and the theory of particle energization produced by small-scale-flux-rope dynamics (Zank et al. and Le Roux et al.). If the particles are pre-accelerated to keV energies via classical mechanisms, they may be additionally accelerated up to 1–1.5 MeV inside magnetically confined cavities of various origins. The magnetic cavities, formed by current sheets, may occur at the interface of different streams such as CIRs and ICMEs or ICMEs and coronal hole flows. They may also form during the HCS interaction with interplanetary shocks (ISs) or CIRs/ICMEs. Particle acceleration inside magnetic cavities may explain puzzling AEPEs occurring far beyond ISs, within ICMEs, before approaching CIRs as well as between CIRs.

  15. VINE-A NUMERICAL CODE FOR SIMULATING ASTROPHYSICAL SYSTEMS USING PARTICLES. II. IMPLEMENTATION AND PERFORMANCE CHARACTERISTICS

    SciTech Connect

    Nelson, Andrew F.; Wetzstein, M.; Naab, T.

    2009-10-01

    We continue our presentation of VINE. In this paper, we begin with a description of relevant architectural properties of the serial and shared memory parallel computers on which VINE is intended to run, and describe their influences on the design of the code itself. We continue with a detailed description of a number of optimizations made to the layout of the particle data in memory and to our implementation of a binary tree used to access that data for use in gravitational force calculations and searches for smoothed particle hydrodynamics (SPH) neighbor particles. We describe the modifications to the code necessary to obtain forces efficiently from special purpose 'GRAPE' hardware, the interfaces required to allow transparent substitution of those forces in the code instead of those obtained from the tree, and the modifications necessary to use both tree and GRAPE together as a fused GRAPE/tree combination. We conclude with an extensive series of performance tests, which demonstrate that the code can be run efficiently and without modification in serial on small workstations or in parallel using the OpenMP compiler directives on large-scale, shared memory parallel machines. We analyze the effects of the code optimizations and estimate that they improve its overall performance by more than an order of magnitude over that obtained by many other tree codes. Scaled parallel performance of the gravity and SPH calculations, together the most costly components of most simulations, is nearly linear up to at least 120 processors on moderate sized test problems using the Origin 3000 architecture, and to the maximum machine sizes available to us on several other architectures. At similar accuracy, performance of VINE, used in GRAPE-tree mode, is approximately a factor 2 slower than that of VINE, used in host-only mode. Further optimizations of the GRAPE/host communications could improve the speed by as much as a factor of 3, but have not yet been implemented in VINE

  16. Densification characteristics of chromia/alumina castables by particle size distribution

    PubMed Central

    2012-01-01

    The quality of the refractories applied on integrated gasification combined cycle should be a key factor that affects both the reliability and the economics of gasifier operation. To enhance the workability of chromia/alumina castables, three types of ultrafine alumina powder were added to improve the workability. Densification behavior of such castables in the presence of ultrafine alumina was assessed through the measurement of parameters like flow value, viscosity, bulk density, apparent porosity, and microstructure evaluation by an SEM study. It's proved that the specific surface area and particle size distribution of ultrafine powders in matrix parts greatly influence the densification behavior of these castables. PMID:22221548

  17. Numerical study on the deposition rate of hematite particle on polypropylene walls: role of surface roughness.

    PubMed

    Henry, Christophe; Minier, Jean-Pierre; Lefèvre, Grégory; Hurisse, Olivier

    2011-04-19

    In this paper, we investigate the deposition of nanosized and microsized particles on rough surfaces under electrostatic repulsive conditions in an aqueous suspension. This issue arises in the general context of modeling particle deposition which, in the present work, is addressed as a two-step process: first particles are transported by the motions of the flow toward surfaces and, second, in the immediate vicinity of the walls, the forces between the incoming particles and the walls are determined using the classical DLVO theory. The interest of this approach is to take into account both hydrodynamical and physicochemical effects within a single model. Satisfactory results have been obtained in attractive conditions but some discrepancies have been revealed in the case of repulsive conditions, in line with other studies which have noted differences between predictions based on the DLVO theory and experimental measurements for similar repulsive conditions. Consequently, the aim of the present work is to focus on this particular range and, more specifically, to assess the influence of surface roughness on the DLVO potential energy. For this purpose, we introduce a new simplified model of surface roughness where spherical protruding asperities are placed randomly on a smooth plate. On the basis of this geometrical description, approximate DLVO expressions are used and numerical calculations are performed. We first highlight the existence of a critical asperity size which brings about the highest reduction of the DLVO interaction energy. Then, the influence of the surface covered by the asperities is investigated as well as retardation effects which can play a role in the reduction of the interaction energy. Finally, by considering the random distribution of the energy barrier of the DLVO potential due to the random geometrical configurations, the overall effect of surface roughness is demonstrated with one application of the complete deposition model in an industrial

  18. Smoothed Particle Hydrodynamics Simulation of Wave Overtopping Characteristics for Different Coastal Structures

    PubMed Central

    Pu, Jaan Hui; Shao, Songdong

    2012-01-01

    This research paper presents an incompressible smoothed particle hydrodynamics (ISPH) technique to investigate a regular wave overtopping on the coastal structure of different types. The SPH method is a mesh-free particle modeling approach that can efficiently treat the large deformation of free surface. The incompressible SPH approach employs a true hydrodynamic formulation to solve the fluid pressure that has less pressure fluctuations. The generation of flow turbulence during the wave breaking and overtopping is modeled by a subparticle scale (SPS) turbulence model. Here the ISPH model is used to investigate the wave overtopping over a coastal structure with and without the porous material. The computations disclosed the features of flow velocity, turbulence, and pressure distributions for different structure types and indicated that the existence of a layer of porous material can effectively reduce the wave impact pressure and overtopping rate. The proposed numerical model is expected to provide a promising practical tool to investigate the complicated wave-structure interactions. PMID:22919291

  19. Charged particle radiotherapy at the Hyogo Ion Beam Medical Center: Characteristics, technology and clinical results

    PubMed Central

    Abe, Mitsuyuki

    2007-01-01

    The Hyogo Ion Beam Medical Center was constructed in 2001 as the world’s first charged particle radiotherapy center where both proton and carbon-ion radiotherapy can be performed. From April 2001 to February 2007, more than 1,400 patients with a variety of cancers were treated. Most of the tumors except for prostate cancer were considered hard to cure with standard treatments such as surgery or conventional x-ray radiotherapy. The clinical results obtained so far are very encouraging, mainly due to the excellent dose localization to the tumor and strong cell killing effects of protons and carbon-ions. The good indications are localized tumors including skull base tumors, head and neck tumors, cancers of the lung, the liver, and the prostate, and bone and soft tissue sarcomas. Charged particle radiotherapy will significantly improve the quality of life of cancer patients and promote their speedy return to normal lives or work if it is used for early stage cancer. PMID:24367141

  20. Numerical investigation of the influence of crystallization of ultrafine particles of aluminum oxide on energy characteristics of solid-propellant rocket engine

    NASA Astrophysics Data System (ADS)

    Dyachenko, N. N.; Dyachenko, L. I.

    2014-08-01

    The results of numerical investigation of a multiphase flow considering coagulation, crushing and crystallization of the particles of polydispersed condensate in the nozzles of solid-propellant rocket engine are presented. The influence of particles crystallization on the energy characteristics of the engine is shown.

  1. Effects of plasmochemical treatments and cerium additions on the structural characteristics and activity of copper catalyst particles in isopropanol dehydrogenation

    NASA Astrophysics Data System (ADS)

    Platonov, E. A.; Lobanov, N. N.; Galimova, N. A.; Protasova, I. A.; Yagodovskii, V. D.

    2012-08-01

    The effect of the treatment of the 5 wt % Cu/SiO2 (I) and (5 wt % Cu + 0.5 wt % Ce)/SiO2 (II) catalysts with glow discharge plasma in O2, H2, and Ar on their structural characteristics was studied by X-ray phase analysis; the influence of cerium additions and plasmochemical treatments on the catalyst activity in isopropanol dehydrogenation was also investigated. Under the plasmochemical treatment, the diameters of Cu particles in catalyst I nearly doubled and microstresses in the metal particles also changed. Catalyst II was X-ray amorphous both before and after plasmochemical treatments. The activity of I after plasmochemical treatment increased because of the increase in the number of centers and changes in their composition. Growth of the activity of I compared with the activity of II was explained by the formation of new catalytic centers due to positive charging of the Ce+α adatom on the surface of the copper particle.

  2. BIOLOGICAL RESPONSE TO NANO-SCALE TIO2: ROLE OF PARTICLE DOSE, SHAPE AND RETENTION

    PubMed Central

    Silva, Rona M.; TeeSy, Christel; Franzi, Lisa; Weir, Alex; Westerhoff, Paul; Evans, James E.; Pinkerton, Kent E.

    2015-01-01

    TiO2 is one of the most widely used nanomaterials, valued for its highly refractive, photocatalytic and pigmenting properties. TiO2 is also classified by the International Agency for Research on Cancer (IARC) as a possible human carcinogen. The objectives of this study were to establish a lowest observed effect level (LOEL) for nano-scale TiO2, determine TiO2 uptake in the lungs, and estimate toxicity based on physico-chemical properties and retention in the lungs. In vivo lung toxicity of nano-scale TiO2 using varying forms of well-characterized, highly-dispersed TiO2 was assessed. Anatase/rutile P25 spheres (TiO2-P25), pure anatase spheres (TiO2-A), and anatase nanobelts (TiO2-NB) were tested. To determine the effects of dose and particle characteristics, male Sprague-Dawley rats were given TiO2 (0, 20, 70, or 200 µg) via intratracheal instillation. Broncho-alveolar lavage fluid (BALF) and lung tissue were obtained for analysis 1 and 7 days post exposure. Despite abundant TiO2 inclusions in all exposed animals, only TiO2-NB elicited any significant degree of inflammation seen in BALF at the 1-day time-point. This inflammation resolved by 7 days; although, TiO2 particles had not cleared from alveolar macrophages recovered from the lung. Histological examination showed TiO2-NB caused cellular changes at day 1 which were still evident at day 7. We conclude TiO2-NB is the most inflammatory with a lowest observable effect level of 200 µg at 1 day post instillation. PMID:24156719

  3. Pyrolysis characteristics of integrated circuit boards at various particle sizes and temperatures.

    PubMed

    Chiang, Hung-Lung; Lin, Kuo-Hsiung; Lai, Mei-Hsiu; Chen, Ting-Chien; Ma, Sen-Yi

    2007-10-01

    A pyrolysis method was employed to recycle the metals and brominated compounds blended into printed circuit boards. This research investigated the effect of particle size and process temperature on the element composition of IC boards and pyrolytic residues, liquid products, and water-soluble ionic species in the exhaust, with the overall goal being to identify the pyrolysis conditions that will have the least impact on the environment. Integrated circuit (IC) boards were crushed into 5-40 mesh (0.71-4.4mm), and the crushed particles were pyrolyzed at temperatures ranging from 200 to 500 degrees C. The thermal decomposition kinetics were measured by a thermogravimetric (TG) analyzer. The composition of pyrolytic residues was analyzed by Energy Dispersive X-ray Spectrometer (EDS), Inductively Coupled Plasma Atomic Emission Spectrometer (ICP-AES) and Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). In addition, the element compositions of liquid products were analyzed by ICP-AES and ICP-MS. Pyrolytic exhaust was collected by a water-absorption system in an ice-bath cooler, and IC analysis showed that the absorbed solution comprised 11 ionic species. Based on the pyrolytic kinetic parameters of TG analysis and pyrolytic residues at various temperatures for 30 min, the effect of particle size was insignificant in this study, and temperature was the key factor for the IC board pyrolysis. Two stages of decomposition were found for IC board pyrolysis under nitrogen atmosphere. The activation energy was 38-47 kcal/mol for the first-stage reaction and 5.2-9.4 kcal/mol for the second-stage reaction. Metal content was low in the liquid by-product of the IC board pyrolysis process, which is an advantage in that the liquid product could be used as a fuel. Brominate and ammonium were the main water-soluble ionic species of the pyrolytic exhaust. A plan for their safe and effective disposal must be developed if the pyrolytic recycling process is to be applied to IC boards

  4. Characteristics of the water-soluble components of aerosol particles in Hefei, China.

    PubMed

    Deng, Xue-liang; Shi, Chun-e; Wu, Bi-wen; Yang, Yuan-jian; Jin, Qi; Wang, Hong-lei; Zhu, Song; Yu, Caixia

    2016-04-01

    Size-classified daily aerosol mass concentrations and concentrations of water-soluble inorganic ions were measured in Hefei, China, in four representative months between September 2012 and August 2013. An annual average mass concentration of 169.09 μg/m(3) for total suspended particulate (TSP) was measured using an Andersen Mark-II cascade impactor. The seasonal average mass concentration was highest in winter (234.73 μg/m(3)) and lowest in summer (91.71 μg/m(3)). Water-soluble ions accounted for 59.49%, 32.90%, 48.62% and 37.08% of the aerosol mass concentration in winter, spring, summer, and fall, respectively, which indicated that ionic species were the primary constituents of the atmospheric aerosols. The four most abundant ions were NO3(-), SO4(2-), Ca(2+) and NH4(+). With the exception of Ca(2+), the mass concentrations of water-soluble ions were in an intermediate range compared with the levels for other Chinese cities. Sulfate, nitrate, and ammonium were the dominant fine-particle species, which were bimodally distributed in spring, summer and fall; however, the size distribution became unimodal in winter, with a peak at 1.1-2.1 μm. The Ca(2+) peak occurred at approximately 4.7-5.8 μm in all seasons. The cation to anion ratio was close to 1.4, which suggested that the aerosol particles were alkalescent in Hefei. The average NO3(-)/SO4(2-) mass ratio was 1.10 in Hefei, which indicated that mobile source emissions were predominant. Significant positive correlation coefficients between the concentrations of NH4(+) and SO4(2-), NH4(+) and NO3(-), SO4(2-) and NO3(-), and Mg(2+) and Ca(2+) were also indicated, suggesting that aerosol particles may be present as (NH4)2SO4, NH4HSO4, and NH4NO3. PMID:27090692

  5. Particle bed reactor propulsion vehicle performance and characteristics as an orbital transfer rocket

    SciTech Connect

    Horn, F.L.; Powell, J.R.; Lazareth, O.W.

    1986-01-01

    The particle bed reactor designed for 100 to 300 MW power output using hydrogen as a coolant is capable of specific impulses up to 1000 seconds as a nuclear rocket. A single space shuttle compatible vehicle can perform extensive missions from LEO to 3 times GEO and return with multi-ton payloads. The use of hydrogen to directly cool particulate reactor fuel results in a compact, lightweight rocket vehicle, whose duration of usefulness is dependent only upon hydrogen resupply availability. The LEO to GEO mission had a payload capability of 15.4 metric tons with 3.4 meters of shuttle bay. To increase the volume limitation of the shuttle bay, the use of ammonia in the initial boost phase from LEO is used to give greater payload volume with a small decrease in payload mass, 8.7 meters and 12.7 m-tons. 5 refs., 15 figs.

  6. Characteristics of ionic polymer-metal composite with chemically doped TiO2 particles

    NASA Astrophysics Data System (ADS)

    Jung, Youngsoo; Kim, Seong Jun; Kim, Kwang J.; Lee, Deuk Yong

    2011-12-01

    Many studies have investigated techniques to improve the bending performance of ionic polymer-metal composite (IPMC) actuators, including 'doping' of metal particles in the polymer membrane usually by means of physical processes. This study is mainly focused on the characterization of the physical, electrochemical and electromechanical properties of TiO2-doped ionic polymer membranes and IPMCs prepared by the sol-gel method, which results in a uniform distribution of the particles inside the polymer membrane. X-ray and UV-visible spectra indicate the presence of anatase-TiO2 in the modified membranes. TiO2-doped membranes (0.16 wt%) exhibit the highest level of water uptake. The glass transition temperature of these membranes, measured using differential scanning calorimetry (DSC), increases with the increase of the amount of TiO2 in the membrane. Dynamic mechanical analysis (DMA) demonstrated that the storage modulus of dried TiO2-doped ionic polymer membranes increases as the amount of TiO2 in the membrane increases, whereas the storage modulus of hydrated samples is closely related to the level of water uptake. Electrochemical impedance spectroscopy (EIS) shows that the conductivity of TiO2-doped membranes decreases with increasing TiO2 content in spite of an internal resistance drop in the samples. Above all, bending deflection of TiO2-doped IPMC decreased with higher TiO2 content in the membrane while the blocking force of each sample increased with the higher TiO2 content. Additionally, it was determined that the lifetime of IPMC is strongly dependent on the level of water uptake.

  7. Distribution characteristics of transparent exopolymer particles in the Pearl River estuary, China

    NASA Astrophysics Data System (ADS)

    Sun, Cui-Ci; Wang, You-Shao; Li, Qian P.; Yue, Wei-Zhong; Wang, Yu-Tu; Sun, Fu-Lin; Peng, Ya-Lan

    2012-12-01

    Distribution of Transparent Exopolymer Particles (TEP) in the Pearl River estuary, China, was investigated during two cruises in August 2009 and January 2010. TEPcolor concentrations were 521.5-1727.4 μg Xeq.L-1 (μg Gum Xanthan equivalent liter-1) in August 2009 and 88.7-1586.9 μg Xeq.L-1 in January 2010, respectively. The size of TEP generally increased in the seaward along the longitudinal section with the dominant size of 2-40 μm during the cruises. Experimental work suggested that both concentration and size of TEP increased with Ca2+ concentration (from 0.8 mmol L-1 to 10 mmol L-1). In the field study, Ca2+ concentration had a positive correlation with TEPcolor concentration in the surface layer with salinity <16. Decrease of TEP concentration seaward from intermediary salinity was partly due to dilution of seawater as well as enhanced aggregation and sedimentation of TEP via increasing divalent cation concentration. TEP concentration and turbidity maximum coexisted at the tip of salt wedge in the bottom layer during the wet season, and positive correlation between TEP and turbidity was observed in the winter. Relationships between TEP and turbidity suggested the important contribution of TEP aggregation to flocculation and sedimentation of particles in estuaries. Different pattern of TEP during two cruises can be attributed to physical process (i.e., mixing type) in estuaries. These findings indicated that formation and distribution of TEP were largely influenced by interaction between physical and biogeochemical processes in the Pearl River estuary. A conceptual model for TEP formation and distribution in the Pearl River estuary was developed.

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    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.

  9. Role of particle shape anisotropy on crack formation in drying of colloidal suspension

    PubMed Central

    Dugyala, Venkateshwar Rao; Lama, Hisay; Satapathy, Dillip K.; Basavaraj, Madivala G.

    2016-01-01

    Cracks in a colloidal film formed by evaporation induced drying can be controlled by changing drying conditions. We show, for the first time that the crack morphologies in colloidal films are dependent on shape of constituting particles apart from the microstructure and particle assembly. In order to investigate the particle shape effect on crack patterns, monodispered spherical and ellipsoidal particles are used in sessile drop experiments. On observing the dried sessile drop we found cracks along the radial direction for spherical particle dispersions and circular crack patterns for ellipsoidal particle dispersions. The change in crack pattern is a result of self assembly of shape anisotropic particles and their ordering. The ordering of particles dictate the crack direction and the cracks follow the path of least resistance to release the excess stress stored in the particle film. Ellipsoids having different aspect ratio (~3 to 7) are used and circular crack patterns are repeatedly observed in all experiments. PMID:27477261

  10. Role of particle shape anisotropy on crack formation in drying of colloidal suspension

    NASA Astrophysics Data System (ADS)

    Dugyala, Venkateshwar Rao; Lama, Hisay; Satapathy, Dillip K.; Basavaraj, Madivala G.

    2016-08-01

    Cracks in a colloidal film formed by evaporation induced drying can be controlled by changing drying conditions. We show, for the first time that the crack morphologies in colloidal films are dependent on shape of constituting particles apart from the microstructure and particle assembly. In order to investigate the particle shape effect on crack patterns, monodispered spherical and ellipsoidal particles are used in sessile drop experiments. On observing the dried sessile drop we found cracks along the radial direction for spherical particle dispersions and circular crack patterns for ellipsoidal particle dispersions. The change in crack pattern is a result of self assembly of shape anisotropic particles and their ordering. The ordering of particles dictate the crack direction and the cracks follow the path of least resistance to release the excess stress stored in the particle film. Ellipsoids having different aspect ratio (~3 to 7) are used and circular crack patterns are repeatedly observed in all experiments.

  11. Role of particle shape anisotropy on crack formation in drying of colloidal suspension.

    PubMed

    Dugyala, Venkateshwar Rao; Lama, Hisay; Satapathy, Dillip K; Basavaraj, Madivala G

    2016-01-01

    Cracks in a colloidal film formed by evaporation induced drying can be controlled by changing drying conditions. We show, for the first time that the crack morphologies in colloidal films are dependent on shape of constituting particles apart from the microstructure and particle assembly. In order to investigate the particle shape effect on crack patterns, monodispered spherical and ellipsoidal particles are used in sessile drop experiments. On observing the dried sessile drop we found cracks along the radial direction for spherical particle dispersions and circular crack patterns for ellipsoidal particle dispersions. The change in crack pattern is a result of self assembly of shape anisotropic particles and their ordering. The ordering of particles dictate the crack direction and the cracks follow the path of least resistance to release the excess stress stored in the particle film. Ellipsoids having different aspect ratio (~3 to 7) are used and circular crack patterns are repeatedly observed in all experiments. PMID:27477261

  12. Particle size distribution and characteristics of heavy metals in road-deposited sediments from Beijing Olympic Park.

    PubMed

    Li, Haiyan; Shi, Anbang; Zhang, Xiaoran

    2015-06-01

    Due to rapid urbanization and industrialization, heavy metals in road-deposited sediments (RDSs) of parks are emitted into the terrestrial, atmospheric, and water environment, and have a severe impact on residents' and tourists' health. To identify the distribution and characteristic of heavy metals in RDS and to assess the road environmental quality in Chinese parks, samples were collected from Beijing Olympic Park in the present study. The results indicated that particles with small grain size (<150 μm) were the dominant fraction. The length of dry period was one of the main factors affecting the particle size distribution, as indicated by the variation of size fraction with the increase of dry days. The amount of heavy metal (i.e., Cu, Zn, Pb and Cd) content was the largest in particles with small size (<150 μm) among all samples. Specifically, the percentage of Cu, Zn, Pb and Cd in these particles was 74.7%, 55.5%, 56.6% and 71.3%, respectively. Heavy metals adsorbed in sediments may mainly be contributed by road traffic emissions. The contamination levels of Pb and Cd were higher than Cu and Zn on the basis of the mean heavy metal contents. Specifically, the geoaccumulation index (Igeo) decreased in the order: Cd>Pb>Cu>Zn. This study analyzed the mobility of heavy metals in sediments using partial sequential extraction with the Tessier procedure. The results revealed that the apparent mobility and potential metal bioavailability of heavy metals in the sediments, based on the exchangeable and carbonate fractions, decreased in the order: Cd>Zn≈Pb>Cu. PMID:26040749

  13. Physicochemical characteristics of aerosol particles generated during the milling of beryllium silicate ores: implications for risk assessment.

    PubMed

    Stefaniak, Aleksandr B; Chipera, Steve J; Day, Gregory A; Sabey, Phil; Dickerson, Robert M; Sbarra, Deborah C; Duling, Mathew G; Lawrence, Robert B; Stanton, Marcia L; Scripsick, Ronald C

    2008-01-01

    Inhalation of beryllium dusts generated during milling of ores and cutting of beryl-containing gemstones is associated with development of beryllium sensitization and low prevalence of chronic beryllium disease (CBD). Inhalation of beryllium aerosols generated during primary beryllium production and machining of the metal, alloys, and ceramics are associated with sensitization and high rates of CBD, despite similar airborne beryllium mass concentrations among these industries. Understanding the physicochemical properties of exposure aerosols may help to understand the differential immunopathologic mechanisms of sensitization and CBD and lead to more biologically relevant exposure standards. Properties of aerosols generated during the industrial milling of bertrandite and beryl ores were evaluated. Airborne beryllium mass concentrations among work areas ranged from 0.001 microg/m(3) (beryl ore grinding) to 2.1 microg/m(3) (beryl ore crushing). Respirable mass fractions of airborne beryllium-containing particles were < 20% in low-energy input operation areas (ore crushing, hydroxide product drumming) and > 80% in high-energy input areas (beryl melting, beryl grinding). Particle specific surface area decreased with processing from feedstock ores to drumming final product beryllium hydroxide. Among work areas, beryllium was identified in three crystalline forms: beryl, poorly crystalline beryllium oxide, and beryllium hydroxide. In comparison to aerosols generated by high-CBD risk primary production processes, aerosol particles encountered during milling had similar mass concentrations, generally lower number concentrations and surface area, and contained no identifiable highly crystalline beryllium oxide. One possible explanation for the apparent low prevalence of CBD among workers exposed to beryllium mineral dusts may be that characteristics of the exposure material do not contribute to the development of lung burdens sufficient for progression from sensitization to

  14. Characteristics of aerosol particles and trace gases in ship exhaust plumes

    NASA Astrophysics Data System (ADS)

    Drewnick, F.; Diesch, J.; Borrmann, S.

    2011-12-01

    Gaseous and particulate matter from marine vessels gain increasing attention due to their significant contribution to the anthropogenic burden of the atmosphere, implying the change of the atmospheric composition and the impact on local and regional air quality and climate (Eyring et al., 2010). As ship emissions significantly affect air quality of onshore regions, this study deals with various aspects of gas and particulate plumes from marine traffic measured near the Elbe river mouth in northern Germany. In addition to a detailed investigation of the chemical and physical particle properties from different types of commercial marine vessels, we will focus on the chemistry of ship plumes and their changes while undergoing atmospheric processing. Measurements of the ambient aerosol, various trace gases and meteorological parameters using a mobile laboratory (MoLa) were performed on the banks of the Lower Elbe which is passed on average, daily by 30 ocean-going vessels reaching the port of Hamburg, the second largest freight port of Europe. During 5 days of sampling from April 25-30, 2011 170 commercial marine vessels were probed at a distance of about 1.5-2 km with high temporal resolution. Mass concentrations in PM1, PM2.5 and PM10 and number as well as PAH and black carbon (BC) concentrations in PM1 were measured; size distribution instruments covered the size range from 6 nm up to 32 μm. The chemical composition of the non-refractory aerosol in the submicron range was measured by means of an Aerosol Mass Spectrometer (Aerodyne HR-ToF-AMS). Gas phase species analyzers monitored various trace gas concentrations in the air and a weather station provided meteorological parameters. Additionally, a wide spectrum of ship information for each vessel including speed, size, vessel type, fuel type, gross tonnage and engine power was recorded via Automatic Identification System (AIS) broadcasts. Although commercial marine vessels powered by diesel engines consume high

  15. Ultrafine particle emission from incinerators: the role of the fabric filter.

    PubMed

    Buonanno, G; Scungio, M; Stabile, L; Tirler, W

    2012-01-01

    Incinerators are claimed to be responsible of particle and gaseous emissions: to this purpose Best Available Techniques (BAT) are used in the flue-gas treatment sections leading to pollutant emission lower than established threshold limit values. As regard particle emission, only a mass-based threshold limit is required by the regulatory authorities. However; in the last years the attention of medical experts moved from coarse and fine particles towards ultrafine particles (UFPs; diameter less than 0.1 microm), mainly emitted by combustion processes. According to toxicological and epidemiological studies, ultrafine particles could represent a risk for health and environment. Therefore, it is necessary to quantify particle emissions from incinerators also to perform an exposure assessment for the human populations living in their surrounding areas. A further topic to be stressed in the UFP emission from incinerators is the particle filtration efficiency as function of different flue-gas treatment sections. In fact, it could be somehow important to know which particle filtration method is able to assure high abatement efficiency also in terms of UFPs. To this purpose, in the present work experimental results in terms of ultrafine particle emissions from several incineration plants are reported. Experimental campaigns were carried out in the period 2007-2010 by measuring UFP number distributions and total concentrations at the stack of five plants through condensation particle counters and mobility particle sizer spectrometers. Average total particle number concentrations ranging from 0.4 x 10(3) to 6.0 x 10(3) particles cm(-3) were measured at the stack of the analyzed plants. Further experimental campaigns were performed to characterize particle levels before the fabric filters in two of the analyzed plants in order to deepen their particle reduction effect; particle concentrations higher than 1 x 10(7) particles cm(-3) were measured, leading to filtration

  16. [Synthesis and characteristic of cobalt bearing ferrite particles at room temperature].

    PubMed

    Wang, Jing; Deng, Tong; Feng, Ya-ping; Dai, Yu-jie

    2005-08-01

    Cobalt bearing magnetite particles were synthesized by aerial oxidation of ferrous and cobalt ions at alkaline condition and room temperature. The samples obtained at different time intervals during reaction were subjected to XRD and IR, and it was indicated that the cobalt-bearing ferrites were produced through green-rust intermediate phase. Different compounds were synthesized using 1/20, 1/15, 1/10, 1/7, 1/5 and 1/3 Co2+/Fe2+ starting ratios, and Co-ferrites with Co/Fe of 0.05, 0.06, 0.08, 0.12, 0.17, 0.18 were obtained. The chemical composition, microstructure and micrograph of those precipitates were characterized by chemical analysis, IR, XRD and SEM. The results revealed that Co2+ replaced Fe3+ at octahedral position in spinel structure, and the increase of Co in initial solution showed deleterious effect on the crystallinity of the precipitates. PMID:16329524

  17. Polycyclic aromatic hydrocarbons in urban atmosphere of Guangzhou, China: Size distribution characteristics and size-resolved gas-particle partitioning

    NASA Astrophysics Data System (ADS)

    Yu, Huan; Yu, Jian Zhen

    2012-07-01

    Size distributions of thirteen polycyclic aromatic hydrocarbons (PAHs), elemental carbon (EC), and organic carbon (OC) in the range of 0.01-18 μm 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 μm), three accumulation modes AMI, AMII, AMIII (MMAD: 0.13-0.17 μm, 0.4-0.45 μm, and 0.9-1.2 μm, respectively), and coarse mode (MMAD: 4-6 μm). 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.

  18. Instability of characteristics of SiC detectors subjected to extreme fluence of nuclear particles

    SciTech Connect

    Ivanov, A. M. Strokan, N. B.; Bogdanova, E. V.; Lebedev, A. A.

    2007-01-15

    The operation of detectors irradiated with 8-MeV protons at a fluence of 3 x 10{sup 14} cm{sup -2} has been studied. The detectors were based on modern CVD-grown n-4H-SiC films with a concentration of uncompensated donors equal to {approx}2 x 10{sup 14} cm{sup -3} and a thickness of 55 {mu}m. The high concentration of primary radiation defects ({approx}2 x 10{sup 17} cm{sup -3}) determined the deep compensation of the films. The basic characteristics of the detectors-pulse amplitude and resolution-exhibited temporal instability. This effect is due to prolonged capture of nonequilibrium carriers by radiation centers and the resulting appearance of a polarization voltage in the bulk of the detector. The kinetics of attainment of steady values by the quantities specified above was analyzed.

  19. Explaining the relationship between insecure attachment and partner abuse: the role of personality characteristics.

    PubMed

    Buck, Nicole M L; Leenaars, Ellie P E M; Emmelkamp, Paul M G; van Marle, Hjalmar J C

    2012-11-01

    Studies have found that male batterers are more often insecurely attached as compared with nonbatterers. However, it is still not clear how insecure attachment is related to domestic violence. Many studies compared batterers and nonbatterers regarding pathological personality characteristics that are related to attachment (e.g., dependency, jealousy) and generally found that batterers report more personality characteristics. However, these studies did not investigate which role these characteristics played in the relationship between insecure attachment and battering. The first aim of this study is to test which personality characteristics are good candidates to explain the relationship between insecure attachment and domestic violence. The second aim is to test whether personality characteristics are predictive of battering over and above attachment. Seventy-two mainly court-mandated family-only males who were in group treatment for battering are allocated to a securely and an insecurely attached group and compared with 62 nonbatterers. Using questionnaires, self-esteem, dependency, general distrust, distrust in partner, jealousy, lack of empathy, separation anxiety, desire for control, and impulsivity were assessed. This was the first study that examined distrust, separation anxiety, and desire for control in relation to battering. The results show that the relationship between insecure attachment and domestic violence can be explained by separation anxiety and partner distrust. Moreover, only partner distrust increased the risk for battering over and above insecure attachment. The findings suggest the presence of two subtypes among batterers based on attachment style, which has similarities to the family-only and dysphoric-borderline subtypes suggested by Holtzworth-Munroe and Stuart. Implications of the present findings for therapy are discussed. PMID:22550146

  20. The role of ions in the self-healing behavior of soft particle suspensions

    NASA Astrophysics Data System (ADS)

    Scotti, Andrea; Gasser, Urs; Herman, Emily S.; Pelaez-Fernandez, Miguel; Han, Jun; Menzel, Andreas; Lyon, L. Andrew; Fernández-Nieves, Alberto

    2016-05-01

    Impurities in crystals generally cause point defects and can even suppress crystallization. This general rule, however, does not apply to colloidal crystals formed by soft microgel particles [Iyer ASJ, Lyon LA (2009) Angew Chem Int Ed 48:4562–4566], as, in this case, the larger particles are able to shrink and join the crystal formed by a majority of smaller particles. Using small-angle X-ray scattering, we find the limit in large-particle concentration for this spontaneous deswelling to persist. We rationalize our data in the context of those counterions that are bound to the microgel particles as a result of the electrostatic attraction exerted by the fixed charges residing on the particle periphery. These bound counterions do not contribute to the suspension osmotic pressure in dilute conditions, as they can be seen as internal degrees of freedom associated with each microgel particle. In contrast, at sufficiently high particle concentrations, the counterion cloud of each particle overlaps with that of its neighbors, allowing these ions to freely explore the space outside the particles. We confirm this scenario by directly measuring the osmotic pressure of the suspension. Because these counterions are then no longer bound, they create an osmotic pressure difference between the inside and outside of the microgels, which, if larger than the microgel bulk modulus, can cause deswelling, explaining why large, soft microgel particles feel the squeeze when suspended with a majority of smaller particles. We perform small-angle neutron scattering measurements to further confirm this remarkable behavior.

  1. Role of fluid density in shaping eruption currents driven by frontal particle blow-out

    NASA Astrophysics Data System (ADS)

    Carroll, C. S.; Turnbull, B.; Louge, M. Y.

    2012-06-01

    We study the role of suspension density in eruption currents, a regime of gravity-driven flow that is sustained by massive, localized blow-out of particles acting as a steady source of heavier fluid injected into a uniform flow at high Reynolds number. Inspired by the potential flow solution of Saffman and Yuen ["Finite-amplitude interfacial waves in the presence of a current," J. Fluid Mech. 123, 459-476 (1982), 10.1017/S0022112082003152], we show that the relative density difference between the two fluids swells the size of the current's head without changing its shape, while inducing a velocity jump at the interface. We test this inviscid theory against inviscid and large-eddy-simulations. We also conduct experiments in a water flume, where a line source of fluorescent brines of various densities is injected in a cross-stream and visualized with a narrow sheet of light. Simulations and experiments reveal that, with isotropic velocity distribution on a finite source, eruption currents expand further and develop interface oscillations, but the inviscid theory still captures relative swelling induced by density. We compare predictions to the static pressure data of McElwaine and Turnbull ["Air pressure data from the Vallee de la Sionne avalanches of 2004," J. Geophys. Res. 110, F03010, doi:, 10.1029/2004JF000237 (2005)] in powder snow avalanches.

  2. (The role of colloidal particles on the subsurface transport of contaminants)

    SciTech Connect

    McCarthy, J.F.

    1990-02-22

    The primary purpose of this foreign travel was to attend the 10th meeting of the European Community's CoCo (colloids and complexation) Club to learn about research on groundwater colloids in Europe and inform the CoCo participants about the colloid subprogram of the US Department of Energy (DOE) Subsurface Science Program. The goal of CoCo Club research, and of the umbrella MIRAGE (MIgration of RAdionuclides in the GEosphere) Project, is to develop data and understanding necessary to complete safety assessments for licensing nuclear repositories in Europe. The emphasis of CoCo Club research is sorption of radionuclides to organic and inorganic colloidal particles. The traveler also visited the British Geological Survey (BGS) headquarters and a BGS field site. Discussions focused on development of innovative drilling equipment for minimizing aquifer disturbance, development and application of computerized resistivity tomography for aquifer characterization, and laboratory research on the role of organic matter on metal transport. The trip was successful in that the traveler obtained a comprehensive overview of European research on groundwater colloids which will help improve and focus DOE's colloid subprogram, and the traveler learned about advances in specific areas that will contribute to his own DOE-funded project.

  3. The role of DNA repair on cell killing by charged particles

    NASA Astrophysics Data System (ADS)

    Eguchi-Kasai, K.; Murakami, M.; Itsukaichi, H.; Fukutsu, K.; Kanai, T.; Furusawa, Y.; Sato, K.; Ohara, H.; Yatagai, F.

    It can be noted that it is not simple double strand breaks (dsb) but the non-reparable breaks that are associated with high biological effectiveness in the cell killing effect for high LET radiation. Here, we have examined the effectiveness of fast neutrons and low (initial energy = 12 MeV/u) or high (135 MeV/u) energy charged particles on cell death in 19 mammalian cell lines including radiosensitive mutants. Some of the radiosensitive lines were deficient in DNA dsb repair such as LX830, M10, V3, and L5178Y-S cells and showed lower values of relative biological effectiveness (RBE) for fast neutrons if compared with their parent cell lines. The other lines of human ataxia-telangiectasia fibroblasts, irs 1, irs 2, irs 3 and irs1SF cells, which were also radiosensitive but known as proficient in dsb repair, showed moderate RBEs. Dsb repair deficient mutants showed low RBE values for heavy ions. These experimental findings suggest that the DNA repair system does not play a major role against the attack of high linear energy transfer (LET) radiations. Therefore, we hypothesize that a main cause of cell death induced by high LET radiations is due to non-reparable dsb, which are produced at a higher rate compared to low LET radiations.

  4. The role of colloid particles in the albumin-lanthanides interaction: The study of aggregation mechanisms.

    PubMed

    Tikhonova, Tatiana N; Shirshin, Evgeny A; Romanchuk, Anna Yu; Fadeev, Victor V

    2016-10-01

    We studied the interaction between bovine serum albumin (BSA) and lanthanide ions in aqueous solution in the 4.0÷9.5pH range. A strong increase of the solution turbidity was observed at pH values exceeding 6, which corresponds to the formation of Ln(OH)3 nanoparticles, while no changes were observed near the isoelectric point of BSA (pH 4.7). The results of the dynamic light scattering and protein adsorption measurements clearly demonstrated that the observed turbidity enhancement was caused by albumin sorption on the surface of Ln(OH)3 and colloid particles bridging via adsorbed protein molecules. Upon pH increase from 4.5 to 6.5, albumin adsorption on lanthanide colloids was observed, while the following increase of pH from 6.5 to 9.5 led to protein desorption. The predominant role of the electrostatic interactions in the adsorption and desorption processes were revealed in the zeta-potential measurements. No reversibility was observed upon decreasing pH from 9.5 to 4.5 that was suggested to be due to the other interaction mechanisms present in the system. It was shown that while for all lanthanide ions the interaction mechanism with BSA was similar, its manifestation in the optical properties of the system was significantly different. This was interpreted as a consequence of the differences in lanthanides hydrolysis constants. PMID:27419645

  5. A massively parallel method of characteristic neutral particle transport code for GPUs

    SciTech Connect

    Boyd, W. R.; Smith, K.; Forget, B.

    2013-07-01

    Over the past 20 years, parallel computing has enabled computers to grow ever larger and more powerful while scientific applications have advanced in sophistication and resolution. This trend is being challenged, however, as the power consumption for conventional parallel computing architectures has risen to unsustainable levels and memory limitations have come to dominate compute performance. Heterogeneous computing platforms, such as Graphics Processing Units (GPUs), are an increasingly popular paradigm for solving these issues. This paper explores the applicability of GPUs for deterministic neutron transport. A 2D method of characteristics (MOC) code - OpenMOC - has been developed with solvers for both shared memory multi-core platforms as well as GPUs. The multi-threading and memory locality methodologies for the GPU solver are presented. Performance results for the 2D C5G7 benchmark demonstrate 25-35 x speedup for MOC on the GPU. The lessons learned from this case study will provide the basis for further exploration of MOC on GPUs as well as design decisions for hardware vendors exploring technologies for the next generation of machines for scientific computing. (authors)

  6. Microstructure and Texture Through Thixomolding and Thermomechanical Processing and the Role of Mg17Al12 Particles

    NASA Astrophysics Data System (ADS)

    Berman, Tracy D.; Pollock, Tresa M.; Jones, J. Wayne

    2016-06-01

    Thixomolding and thermomechanical processing (TTMP) is a pathway through which it is possible to produce Mg alloy sheet with both a fine grain size and a weak basal texture. Following static recrystallization, the texture of TTMP AZ61 is comparable to that of rare-earth Mg alloy sheets. The β-Mg17Al12 particles in the alloy serve several important roles. Pinning during rolling retards dynamic recrystallization, thereby preventing the development of the typical Mg sheet deformation texture. Recrystallized grains form near clusters of β-particles and in the grain mantle regions. Larger β-particles pin boundaries during subsolvus thermal exposures and therefore provide grain size stability during annealing. The size and spatial arrangement of the β-particles are relatively stable during processing, so modifications to optimize the texture reduction or grain size stability would require changes in composition or modifications in the Thixomolding parameters.

  7. Role of Pre-Course Student Characteristics on Student Learning in Interactive Teaching Environments

    NASA Astrophysics Data System (ADS)

    Miller, Kelly Anne

    The goal of this dissertation is to broaden our understanding of interactive teaching strategies, in the context of the introductory physics classroom at the undergraduate level. The dissertation is divided into four main projects, each of which investigates a specific aspect of teaching physics interactively. All four projects look towards improving the effectiveness of interactive teaching by understanding how pre-course student characteristics affect the way students learn interactively. We first discuss lecture demonstrations in the context of an interactive classroom using Peer Instruction. We study the role of predictions in conceptual learning. We examine how students' predictions affect what they report having seen during a demonstration. We also examine how student predictions affect what they recall as the outcome of the demonstration at the end of the semester. We then analyze student response patterns to conceptual questions posed during Peer Instruction. We look at the relationship between a student's tendency to switch their answer and pre-course student characteristics like science self-efficacy. Next we elucidate response timing to conceptual questions posed over the course of the semester, in two introductory physics classes taught using Peer Instruction. We look at the relationship between student response times and student characteristics like pre-course physics knowledge, science self-efficacy and gender. We study response times as a way of gaining insight into students thinking in Peer Instruction environments as well as to improve the implementation of Peer Instruction. Finally, we present work on the role of NB, an online collaborative textbook annotation tool, in a flipped, project based, physics class. We analyze the relationship between students' level of online engagement and traditional learning metrics to understand the effectiveness of NB in the context of flipped classrooms. We also report the results of experiments conducted to

  8. The Role of Criegee Intermediates in Particle Formation and Growth during the Ozonolysis of Small Alkenes

    NASA Astrophysics Data System (ADS)

    Zhao, Y.; Wingen, L. M.; Perraud, V. M.; Finlayson-Pitts, B. J.

    2014-12-01

    Ozonolysis of alkenes is an important source of particulate matter (e.g., secondary organic aerosol) in the atmosphere. However, the mechanisms by which Criegee intermediates (CI) react to form the particles, particularly the oligomeric components, are currently not well understood. In this study, ozonolysis of trans-3-hexene was investigated with a focus on the formation mechanism of oligomers involving CI, as well as their contributions to particle formation and growth. Ozonolysis experiments were performed both in a static chamber and in a flow reactor in the absence and presence of an OH or stabilized CI (SCI) scavenger. The oligomeric and elemental composition of the total and size-selected particles was measured with different mass spectrometries, and the effects of adding OH and SCI scavengers were investigated. Size-selected measurements show that the relative abundance of higher ordered oligomers in the particles decreases with increasing particle size, indicating the preference of larger oligomers in the growth of smaller particles. Consistent with oligomeric composition, the O/C ratio of the particles decreases with particle size, suggesting more oxygenated organic material (e.g., primarily oligomeric peroxides) in smaller particles. The mechanism for particle formation suggested by these data is the initial reaction of RO2 radicals to the CI, followed by sequential addition of CI, in agreement with the earlier work of Sadezky et al. (2008). The relationship to the mechanism of particle formation from larger alkenes such as terpenes and the atmospheric implications will be explored.

  9. Role of particle size and composition in metal adsorption by solids deposited on urban road surfaces.

    PubMed

    Gunawardana, Chandima; Egodawatta, Prasanna; Goonetilleke, Ashantha

    2014-01-01

    Despite common knowledge that the metal content adsorbed by fine particles is relatively higher compared to coarser particles, the reasons for this phenomenon have gained little research attention. The research study discussed in the paper investigated the variations in metal content for different particle sizes of solids associated with pollutant build-up on urban road surfaces. Data analysis confirmed that parameters favourable for metal adsorption to solids such as specific surface area, organic carbon content, effective cation exchange capacity and clay forming minerals content decrease with the increase in particle size. Furthermore, the mineralogical composition of solids was found to be the governing factor influencing the specific surface area and effective cation exchange capacity. There is high quartz content in particles >150 μm compared to particles <150 μm. As particle size reduces below 150 μm, the clay forming minerals content increases, providing favourable physical and chemical properties that influence adsorption. PMID:24021928

  10. Investigation of Propagation Characteristics of Twisted Hollow Waveguides for Particle Accelerator Applications

    SciTech Connect

    Wilson, Joshua Lee

    2008-09-01

    A new class of accelerating structures employing a uniformly twisted waveguide is investigated. Twisted waveguides of various cross-sectional geometries are considered and analyzed. It is shown that such a twisted waveguide can support waves that travel at a speed slower than the speed of light c. The slow-wave properties of twisted structures are of interest because these slow-wave electromagnetic fields can be used in applications such as electron traveling wave tubes and linear particle accelerators. Since there is no exact closed form solution for the electromagnetic fields within a twisted waveguide or cavity, several previously proposed approximate methods are examined, and more effcient approaches are developed. It is found that the existing perturbation theory methods yield adequate results for slowly twisted structures; however, our efforts here are geared toward analyzing rapidly twisted structures using modifed finite difference methods specially suited for twisted structures. Although the method can handle general twisted structures, three particular cross sections are selected as representative cases for careful analysis. First, a slowly twisted rectangular cavity is analyzed as a reference case. This is because its shape is simple and perturbation theory already gives a good approximate solution for such slow twists rates. Secondly, a symmetrically notched circular cross section is investigated, since its longitudinal cross section is comparable to the well known disk-loaded cavity (used in many practical accelerator designs, including SLAC). Finally, a "dumbbell" shaped cross section is analyzed because of its similarity to the well-known TESLA-type accelerating cavity, which is of great importance because of its wide acceptance as a superconducting cavity. To validate the results of the developed theory and our extensive simulations, the newly developed numerical models are compared to commercial codes. Also, several prototypes are developed

  11. Correlation Analyses Between the Characteristic Times of Gradual Solar Energetic Particle Events and the Properties of Associated Coronal Mass Ejections

    NASA Astrophysics Data System (ADS)

    Pan, Z. H.; Wang, C. B.; Wang, Yuming; Xue, X. H.

    2011-06-01

    It is generally believed that gradual solar energetic particles (SEPs) are accelerated by shocks associated with coronal mass ejections (CMEs). Using an ice-cream cone model, the radial speed and angular width of 95 CMEs associated with SEP events during 1998 - 2002 are calculated from SOHO/LASCO observations. Then, we investigate the relationships between the kinematic properties of these CMEs and the characteristic times of the intensity-time profile of their accompanied SEP events observed at 1 AU. These characteristic times of SEP are i) the onset time from the accompanying CME eruption at the Sun to the SEP arrival at 1 AU, ii) the rise time from the SEP onset to the time when the SEP intensity is one-half of peak intensity, and iii) the duration over which the SEP intensity is within a factor of two of the peak intensity. It is found that the onset time has neither significant correlation with the radial speed nor with the angular width of the accompanying CME. For events that are poorly connected to the Earth, the SEP rise time and duration have no significant correlation with the radial speed and angular width of the associated CMEs. However, for events that are magnetically well connected to the Earth, the SEP rise time and duration have significantly positive correlations with the radial speed and angular width of the associated CMEs. This indicates that a CME event with wider angular width and higher speed may more easily drive a strong and wide shock near to the Earth-connected interplanetary magnetic field lines, may trap and accelerate particles for a longer time, and may lead to longer rise time and duration of the ensuing SEP event.

  12. [Particle Size Distribution, Seasonal Variation Characteristics and Human Exposure Assessment of Heavy Metals in Typical Settled Dust from Beijing].

    PubMed

    Cao, Zhi-guo; Yu, Gang; Lü, Xiang-ying; Wang, Meng-lei; Li, Qi-lu; Feng, Jing-lan; Yan, Guang-xuan; Yu, Hao; Sun, Jian-hui

    2016-04-15

    Four types of dust from dormitories, offices, hotels and roads in Beijing were collected and fractionated into 9 fractions, respectively. Totally 36 samples were obtained and analyzed for heavy metals including Cu, Zn, Cr, Pb, Cd and Ni. Particle size distributions of those heavy metals in these four types of dust were investigated and the influencing mechanisms were discussed. Distribution patterns of the same heavy metal in different types of dust showed various characteristics. Also different metals in the same type of dust represented different distribution patterns. Heavy metals in road dust tended to concentrate in finer particles. Two offices from the same building, located in Beijing, China, were selected to study the seasonality of heavy metals in dust. Dust sampling from Office A was conducted at weekly intervals between March 2012 and August 2012, while dust from Office B was sampled fortnightly from March 2012 to December 2012. Generally, levels of all heavy metals remained stable among different seasons, however, Cr and Pb represented more significant fluctuations than other four heavy metals. Based on the geo-accumulation index method, the pollution of Zn, Cu and Pb was more serious in the investigated samples, and dust from offices and hotels were moderately polluted by Zn. According to the risk assessment results, the carcinogenic health risks of the six heavy metals in the four types of dust were negligible. PMID:27548946

  13. Insomnia, Nightmare Frequency, and Nightmare Distress in Victims of Sexual Abuse: The Role of Perceived Social Support and Abuse Characteristics

    ERIC Educational Resources Information Center

    Steine, Iris M.; Krystal, John H.; Nordhus, Inger H.; Bjorvatn, Bjorn; Harvey, Allison G.; Eid, Jarle; Gronli, Janne; Milde, Anne M.; Pallesen, Stale

    2012-01-01

    In this study of victims of sexual abuse, the aim was to investigate the role of perceived social support and abuse characteristics in self-reported insomnia, nightmare frequency, and nightmare distress. Four hundred sixty Norwegian victims of sexual abuse completed a questionnaire assessing perceived social support, abuse characteristics,…

  14. Downward particle flux and carbon export in the Beaufort Sea, Arctic Ocean; the role of zooplankton

    NASA Astrophysics Data System (ADS)

    Miquel, J.-C.; Gasser, B.; Martín, J.; Marec, C.; Babin, M.; Fortier, L.; Forest, A.

    2015-08-01

    As part of the international, multidisciplinary project Malina, downward particle fluxes were investigated by means of a drifting multi-sediment trap mooring deployed at three sites in the Canadian Beaufort Sea in late summer 2009. Mooring deployments lasted between 28 and 50 h and targeted the shelf-break and the slope along the Beaufort-Mackenzie continental margin, as well as the edge between the Mackenzie Shelf and the Amundsen Gulf. Besides analyses of C and N, the collected material was investigated for pigments, phyto- and microzooplankton, faecal pellets and swimmers. The measured fluxes were relatively low, in the range of 11-54 mg m-2 d-1 for the total mass, 1-15 mg C m-2 d-1 for organic carbon and 0.2-2.5 mg N m-2 d-1 for nitrogen. Comparison with a long-term trap data set from the same sampling area showed that the short-term measurements were at the lower end of the high variability characterizing a rather high flux regime during the study period. The sinking material consisted of aggregates and particles that were characterized by the presence of hetero- and autotrophic microzooplankters and diatoms and by the corresponding pigment signatures. Faecal pellets contribution to sinking carbon flux was important, especially at depths below 100 m, where they represented up to 25 % of the total carbon flux. The vertical distribution of different morphotypes of pellets showed a marked pattern with cylindrical faeces (produced by calanoid copepods) present mainly within the euphotic zone, whereas elliptical pellets (produced mainly by smaller copepods) were more abundant at mesopelagic depths. These features, together with the density of matter within the pellets, highlighted the role of the zooplankton community in the transformation of carbon issued from the primary production and the transition of that carbon from the productive surface zone to the Arctic Ocean's interior. Our data indicate that sinking carbon flux in this late summer period is primarily

  15. The Role of Friction in the Segregation of Particles in a Chute Flow

    NASA Astrophysics Data System (ADS)

    Hernandez-Sanchez, Federico; Zenit, Roberto

    2009-11-01

    When a granular media, compound of particles with different properties, flows de-mixing of the constituent components may occur. This phenomenon, known as segregation, has been observed in particles with different sizes (the Brazil nut effect). In spite of being a well studied process, there is not a general understanding of the mechanisms that dominate this process. It is our interest to study the conditions that determine particle segregation in avalanches. Using a two-dimensional, discrete-element simulation, we study a bidisperse flow of particles over an inclined plane with periodic boundaries. We vary the roughness of the wall by attaching fixed particles on it. A wide range of parameters were varied (slope, number of particles, size ratio, density ratio). Both ordinary and reverse segregation patterns were observed. In this talk some preliminary results and their interpretation will be presented.

  16. Critical roles of cationic surfactants in the preparation of colloidal mesostructured silica nanoparticles: control of mesostructure, particle size, and dispersion.

    PubMed

    Yamada, Hironori; Urata, Chihiro; Higashitamori, Sayuri; Aoyama, Yuko; Yamauchi, Yusuke; Kuroda, Kazuyuki

    2014-03-12

    Mesoporous silica nanoparticles are promising materials for various applications, such as drug delivery and catalysis, but the functional roles of surfactants in the formation and preparation of mesostructured silica nanoparticles (MSN-as) remain to be seen. It was confirmed that the molar ratio of cationic surfactants to Si of alkoxysilanes (Surf/Si) can affect the degree of mesostructure formation (i.e., whether the mesochannels formed inside the nanoparticles actually pass through the outer surface of the particles), the particle diameter, and the dispersibility of MSN-as. Wormhole-like mesostructures formed with low Surf/Si ratios; however, the mesopores did not pass through the outer surface of the particles completely. At high Surf/Si ratios, the mesostructures extended. The particle diameter was 100 nm or larger at low Surf/Si ratios, and the primary particle diameter decreased as the Surf/Si ratio increased. This was because the surfactants enhanced the dispersity of the alkoxysilanes in water and the hydrolysis rate of the alkoxysilanes became faster, leading to an increased nucleation as compared to the particle growth. Moreover, primary particles aggregated at low Surf/Si ratios because of the hydrophobic interactions among the surfactants that were not involved in the mesostructure formation but were adsorbed onto the nanoparticles. At high Surf/Si ratios, the surfactant micelles were adsorbed on the surface of primary particles (admicelles), resulting in the dispersion of the particles due to electrostatic repulsion. In particular, molar ratios of 0.13 or higher were quite effective for the preparation of highly dispersed MSN-as. Surfactants played important roles in the mesostructure formation, decreasing the particle diameters, and the dispersibility of the particles. All of these factors were considerably affected by the Surf/Si ratio. The results suggested novel opportunities to control various colloidal mesostructured nanoparticles from the

  17. The role of ions in the self-healing behavior of soft particle suspensions.

    PubMed

    Scotti, Andrea; Gasser, Urs; Herman, Emily S; Pelaez-Fernandez, Miguel; Han, Jun; Menzel, Andreas; Lyon, L Andrew; Fernández-Nieves, Alberto

    2016-05-17

    Impurities in crystals generally cause point defects and can even suppress crystallization. This general rule, however, does not apply to colloidal crystals formed by soft microgel particles [Iyer ASJ, Lyon LA (2009) Angew Chem Int Ed 48:4562-4566], as, in this case, the larger particles are able to shrink and join the crystal formed by a majority of smaller particles. Using small-angle X-ray scattering, we find the limit in large-particle concentration for this spontaneous deswelling to persist. We rationalize our data in the context of those counterions that are bound to the microgel particles as a result of the electrostatic attraction exerted by the fixed charges residing on the particle periphery. These bound counterions do not contribute to the suspension osmotic pressure in dilute conditions, as they can be seen as internal degrees of freedom associated with each microgel particle. In contrast, at sufficiently high particle concentrations, the counterion cloud of each particle overlaps with that of its neighbors, allowing these ions to freely explore the space outside the particles. We confirm this scenario by directly measuring the osmotic pressure of the suspension. Because these counterions are then no longer bound, they create an osmotic pressure difference between the inside and outside of the microgels, which, if larger than the microgel bulk modulus, can cause deswelling, explaining why large, soft microgel particles feel the squeeze when suspended with a majority of smaller particles. We perform small-angle neutron scattering measurements to further confirm this remarkable behavior. PMID:27125854

  18. Hygroscopicity of mineral dust particles: Roles of chemical mixing state and hygroscopic conversion timescale

    NASA Astrophysics Data System (ADS)

    Sullivan, R. C.; Moore, M. J.; Petters, M. D.; Laskin, A.; Roberts, G. C.; Kreidenweis, S. M.; Prather, K. A.

    2009-05-01

    Our laboratory investigations of mineral dust particle hygroscopicity are motivated by field observations of the atmospheric processing of dust. During ACE-Asia we observed sulphate and nitrate to be strongly segregated from each other in individual aged Asian dust particles. CCN activation curves of pure calcium minerals as proxies for fresh (calcium carbonate) and aged (calcium sulphate, nitrate, chloride) dust indicate that this mixing state would cause a large fraction of aged dust particles to remain poor warm cloud nucleation potential, contrary to previous assumptions. The enrichment of oxalic acid in calcium-rich dust particles could have similar effects due to the formation of insoluble calcium oxalate. Soluble calcium nitrate and chloride reaction products are hygroscopic and will transform mineral dust into excellent CCN. Generating insoluble mineral particles wet by atomization produced particles with much higher hygroscopicity then when resuspended dry. The atomized particles are likely composed of dissolved residuals and do not properly reflect the chemistry of dry mineral powders. Aerosol flow tube experiments were employed to study the conversion of calcium carbonate into calcium nitrate via heterogeneous reaction with nitric acid, with simultaneous measurements of the reacted particles' chemistry and hygroscopicity. The timescale for this hygroscopic conversion was found to occur on the order of a few hours under tropospheric conditions. This implies that the conversion of non-hygroscopic calcite- containing dust into hygroscopic particles will be controlled by the availability of nitric acid, and not by the atmospheric residence time. Results from recent investigations of the effect of secondary coatings on the ice nucleation properties of dust particles will also be presented. The cloud formation potential of aged dust particles depends on both the quantity and form of the secondary species that have reacted or mixed with the dust. These results

  19. Eyewitness Testimony for a Simulated Juvenile Crime by Male and Female Criminals with Consistent or Inconsistent Gender-Role Characteristics

    ERIC Educational Resources Information Center

    Shapiro, Lauren R.

    2009-01-01

    Eyewitness recall by 60 adolescents and 60 young adults in Experiment 1 and by 64 children and 63 preadolescents in Experiment 2 for a simulated theft in which gender-role characteristics and sex of criminal were manipulated (i.e., masculine male, feminine male, feminine female, masculine female) was investigated. Gender-role flexibility impacted…

  20. Role of impactor properties on the computational simulation of particle impact damage in transparent ceramic windows

    NASA Astrophysics Data System (ADS)

    Schultz, Robert; Guven, Ibrahim; Zelinski, Brian J.

    2014-05-01

    The ability to deploy advanced sensor and seeker systems in harsh environments is often restricted by the mechanical durability of the external electromagnetic window or dome. Mission environments may range from long flights at high speeds through rain, ice, or sand to exposure at slower speeds to debris on runways or from helicopter downwash. While significant progress has been made to characterize, understand, and model rain damage, less is known about modeling damage in windows and domes caused by impacts from solid particles such as stones, pebbles, and sand. This paper highlights recent progress made to simulate particle impact damage in zinc sulfide (ZnS) using peridynamics (PD). Early versions of the PD model of sand impact damage simulated the sand particle as a rigid disk. Results from these early models indicated that the extent of damage in relation to the size of the impacting particle was significantly larger than the actual damage observed by experimentation. In order to identify possible explanations for this discrepancy, the shape, impact orientation and mechanical properties of the impacting particle were modified to more closely resemble actual sand particle impacts, that is, the particle was made friable (deformable and breakable). The impacting geometries considered include sphere, flat face of a cylinder, cube-face, cube-edge, and cube-corner. Results confirm that modification of the impacting particle's mechanical properties, shape and impact orientation lead to better agreement between experimental observations and simulation results.

  1. I V characteristic of electronic transport through a quantum dot chain: The role of antiresonance

    NASA Astrophysics Data System (ADS)

    Liu, Yu; Zheng, Yisong; Gong, Weijiang; Lü, Tianquan

    2006-12-01

    The I V spectrum of electronic transport through a quantum dot chain is calculated by means of the nonequilibrium Green function technique. In such a system, two arbitrary quantum dots are connected with two electron reservoirs through leads. When the dot-lead coupling is very weak, a series of discrete resonant peaks in electron transmission function cause staircase-like I V characteristic. On the contrary, in the relatively strong dot-lead coupling regime, stairs in the I V spectrum due to resonance vanish. However, when there are some dangling quantum dots in the chain outside two leads, the antiresonance which corresponds to the zero points of electron transmission function brings about novel staircase characteristic in the I V spectrum. Moreover, two features in the I V spectrum arising from the antiresonance are pointed out, which are significant for possible device applications. One is the multiple negative differential conductance regions, and another is regarding to create a highly spin-polarized current through the quantum dot chain by the interplay of the resonance and antiresonance. Finally, we focus on the role that the many-body effect plays on the antiresonance. Our result is that the antiresonance remains when the electron interaction is considered to the second order approximation.

  2. Investigating the role of parent and child characteristics in healthy eating intervention outcomes.

    PubMed

    Holley, Clare E; Farrow, Claire; Haycraft, Emma

    2016-10-01

    While numerous studies have investigated the efficacy of interventions at increasing children's vegetable consumption, little research has examined the effect of individual characteristics on intervention outcomes. In previous research, interventions consisting of modelling and rewards have been shown to increase children's vegetable intake, but differences were identified in terms of how much children respond to such interventions. With this in mind, the current study investigated the role of parental feeding practices, child temperament, and child eating behaviours as predictors of intervention success. Parents (N = 90) of children aged 2-4 years were recruited from toddler groups across Leicestershire, UK. Parents completed measures of feeding practices, child eating behaviours and child temperament, before participating in one of four conditions of a home-based, parent led 14 day intervention aimed at increasing their child's consumption of a disliked vegetable. Correlations and logistic regressions were performed to investigate the role of these factors in predicting intervention success. Parental feeding practices were not significantly associated with intervention success. However, child sociability and food fussiness significantly predicted intervention success, producing a regression model which could predict intervention success in 61% of cases. These findings suggest that future interventions could benefit from being tailored according to child temperament. Furthermore, interventions for children high in food fussiness may be better targeted at reducing fussiness in addition to increasing vegetable consumption. PMID:27263070

  3. Characteristics of hypervelocity impact craters on LDEF experiment S1003 and implications of small particle impacts on reflective surfaces

    NASA Technical Reports Server (NTRS)

    Mirtich, Michael J.; Rutledge, Sharon K.; Banks, Bruce A.; Devries, Christopher; Merrow, James E.

    1993-01-01

    The Ion Beam textured and coated surfaces EXperiment (IBEX), designated S1003, was flown on LDEF at a location 98 deg in a north facing direction relative to the ram direction. Thirty-six diverse materials were exposed to the micrometeoroid (and some debris) environment for 5.8 years. Optical property measurements indicated no changes for almost all of the materials except S-13G, Kapton, and Kapton-coated surfaces, and these changes can be explained by other environmental effects. From the predicted micrometeoroid flux of NASA SP-8013, no significant changes in optical properties of the surfaces due to micrometeoroids were expected. There were hypervelocity impacts on the various diverse materials flown on IBEX, and the characteristics of these craters were documented using scanning electron microscopy (SEM). The S1003 alumigold-coated aluminum cover tray was sectioned into 2 cm x 2 cm pieces for crater documentation. The flux curve generated from this crater data fits well between the 1969 micrometeoroid model and the Kessler debris model for particles less than 10(exp -9) gm which were corrected for the S1003 positions (98 deg to ram). As the particle mass increases, the S1003 impact data is greater than that predicted by even the debris model. This, however, is consistent with data taken on intercostal F07 by the Micrometeoroid/Debris Special Investigating Group (M/D SIG). The mirrored surface micrometeoroid detector flown on IBEX showed no change in solar reflectance and corroborated the S1003 flux curve, as well as results of this surface flown on SERT 2 and OSO 3 for as long as 21 years.

  4. Characteristics of hypervelocity impact craters on LDEF experiment S1003 and implications of small particle impacts on reflective surfaces

    NASA Astrophysics Data System (ADS)

    Mirtich, Michael J.; Rutledge, Sharon K.; Banks, Bruce A.; Devries, Christopher; Merrow, James E.

    1993-04-01

    The Ion Beam textured and coated surfaces EXperiment (IBEX), designated S1003, was flown on LDEF at a location 98 deg in a north facing direction relative to the ram direction. Thirty-six diverse materials were exposed to the micrometeoroid (and some debris) environment for 5.8 years. Optical property measurements indicated no changes for almost all of the materials except S-13G, Kapton, and Kapton-coated surfaces, and these changes can be explained by other environmental effects. From the predicted micrometeoroid flux of NASA SP-8013, no significant changes in optical properties of the surfaces due to micrometeoroids were expected. There were hypervelocity impacts on the various diverse materials flown on IBEX, and the characteristics of these craters were documented using scanning electron microscopy (SEM). The S1003 alumigold-coated aluminum cover tray was sectioned into 2 cm x 2 cm pieces for crater documentation. The flux curve generated from this crater data fits well between the 1969 micrometeoroid model and the Kessler debris model for particles less than 10(exp -9) gm which were corrected for the S1003 positions (98 deg to ram). As the particle mass increases, the S1003 impact data is greater than that predicted by even the debris model. This, however, is consistent with data taken on intercostal F07 by the Micrometeoroid/Debris Special Investigating Group (M/D SIG). The mirrored surface micrometeoroid detector flown on IBEX showed no change in solar reflectance and corroborated the S1003 flux curve, as well as results of this surface flown on SERT 2 and OSO 3 for as long as 21 years.

  5. The role of equiaxed particles on the yield stress of composites

    NASA Technical Reports Server (NTRS)

    Aikin, R. M., Jr.; Christodoulou, L.

    1991-01-01

    Possible explanations are investigated for the yield strength enhancement of discontinuously reinforced Al alloy matrix MMCs, for the case of low temperature yield behavior where deformation occurs by dislocation slide. The Al alloys contain 0.1-10 micron diameter equiaxed particle discontinuous reinforcements of TiB2, Al2O3, and TiC. Attention is given to a single dislocation-particle interaction model, and both dislocation pile-up and forest-hardening multiple-dislocation particle interaction models.

  6. The role of interplanetary shocks in the longitude distribution of solar energetic particles

    NASA Technical Reports Server (NTRS)

    Cane, H. V.; Reames, D. V.; Von Rosenvinge, T. T.

    1988-01-01

    Data from the Goddard particle experiments on IMPs 4, 5, 7, and 8, and ISEE 3 are used to model particle intensity profiles including prompt solar particles and the effects of shocks. It is shown that the intensity profiles of solar protons depend on the heliolongitude, and it is suggested that the major controlling agent is the existence of an interplanetary (IP) shock. Shocks are strongest when observed along the radial from the source region, with the highest shock-associated intensities generally observed from central meridian flares. Using a recently derived model for the large-scale structure of IP shocks, the change in shape as a function of heliolongitude is explained.

  7. Observed impact of energetic particles on the stratosphere and mesosphere and its role in global change

    NASA Astrophysics Data System (ADS)

    Jackman, C. H.

    2011-12-01

    Energetic precipitating particles (EPPs) can cause significant constituent changes in the polar stratosphere and mesosphere (middle atmosphere) during certain periods. Both protons and electrons can influence the polar middle atmosphere through ionization and dissociation processes. EPPs can enhance HOx (H, OH, HO2) through the formation of positive ions followed by complex ion chemistry and NOx (N, NO, NO2) through the dissociation of molecular nitrogen. The HOx increases can lead to ozone destruction in the mesosphere and upper stratosphere via several catalytic loss cycles. Such middle atmospheric HOx-caused ozone loss is rather short-lived due to the relatively short lifetime (hours) of the HOx constituents. HOx enhancements due to SPEs were confirmed by observations in the past solar cycle and HOx-caused ozone depletion has been observed during several solar proton events in the past 50 years. The NOx family has a longer lifetime than the HOx family and can also lead to catalytic ozone destruction. EPP-caused enhancements of the NOx family can affect ozone promptly, if produced in the stratosphere, or subsequently, if produced in the lower thermosphere or mesosphere and transported to the stratosphere. NOx enhancements due to auroral electrons, medium and high energy electrons, relativistic electron precipitation events, and solar proton events have been measured and/or modeled for decades. Model predictions and measurements show that certain years have significant winter-time meteorological events, which result in the transport of EPP-caused NOx enhancements in the upper mesosphere and lower thermosphere to lower altitudes. A recent study has shown statistically significant changes in polar surface air temperatures correlated with electron precipitation, although the authors suggest that the Northern Annular Mode introduces significant uncertainty into the results (Seppälä et al., J. Geophys. Res., 114, A10312, doi:10.1029/2008JA014029, 2009). Several solar

  8. On the role of the Sivers effect in A{sub N} for inclusive particle production in pp collisions

    SciTech Connect

    Anselmino, Mauro; Boglione, Mariaelena; D'Alesio, Umberto; Melis, Stefano; Murgia, Francesco; Prokudin, Alexei

    2014-01-01

    Single spin asymmetries, A{sub N} , for inclusive particle production in pp collisions are considered within a generalized parton model with inclusion of spin and tranverse momentum effects. We consider the potential role of the Sivers effect in A{sub N} , as extracted from a careful analysis of azimuthal asymmetries in SIDIS, and discuss its phenomenological consequences in connection with a recently updated study of the Collins effect.

  9. The Peptidoglycan Hydrolase of Staphylococcus aureus Bacteriophage ϕ11 Plays a Structural Role in the Viral Particle

    PubMed Central

    Rodríguez-Rubio, Lorena; Quiles-Puchalt, Nuria; Martínez, Beatriz; Rodríguez, Ana; Penadés, José R.

    2013-01-01

    The role of virion-associated peptidoglycan hydrolases (VAPGHs) in the phage infection cycle is not clear. gp49, the VAPGH from Staphylococcus aureus phage ϕ11, is not essential for phage growth but stabilizes the viral particles. ϕ11Δ49 phages showed a reduced burst size and delayed host lysis. Complementation of gp49 with HydH5 from bacteriophage vB_SauS-phiIPLA88 restored the wild-type phenotype. PMID:23892745

  10. Role of Polymer Segment-Particle Surface Interactions in Controlling Nanoparticle Dispersions in Concentrated Polymer Solutions

    SciTech Connect

    Kim, So Youn; Zukoski, Charles F.

    2014-09-24

    The microstructure of particles suspended in concentrated polymer solutions is examined with small-angle X-ray scattering and small-angle neutron scattering. Of interest are changes to long wavelength particle density fluctuations in ternary mixtures of silica nanoparticles suspended in concentrated solutions of poly(ethylene glycol). The results are understood in terms of application of the pseudo-two-component polymer reference interaction site model (PRISM) theory modified to account for solvent addition via effective contact strength of interfacial attraction, εpc, in an implicit manner. The combined experimental-theoretical study emphasizes the complex interactions between solvent, polymer, and particle surface that control particle miscibility but also demonstrate that these factors can all be understood in terms of variations of εpc.

  11. Role of surface gauging in extended particle interactions: The case for spin

    NASA Astrophysics Data System (ADS)

    Mazilu, Nicolae; Ghizdovat, Vlad; Agop, Maricel

    2016-05-01

    The matter, being extended in space, should be first characterized by a surface of separation from the empty space. This surface cannot be neatly, i.e. purely geometrically, defined. When it comes to extended particles, which thereby are to be considered the fundamental structural units of the matter, the physical evidence points out that they are not even stable: they are in a continuous transformation; and so is their limit of separation from space. The present work describes a concept of extended particle with special emphasis on this limit of separation. It turns out that the properties of inertia, as classically understood, are intrinsically related to the spin properties of quantum origin. Thus, an extended particle model cannot be but "holographic" when it comes to imbedding it in a physical structure. The spin properties turn out to be essential, inasmuch as they decide the forces of interaction issuing from particles.

  12. Particle nonuniformity effects on particle cloud flames in low gravity

    NASA Technical Reports Server (NTRS)

    Berlad, A. L.; Tangirala, V.; Seshadri, K.; Facca, L. T.; Ogrin, J.; Ross, H.

    1991-01-01

    Experimental and analytical studies of particle cloud combustion at reduced gravity reveal the substantial roles that particle cloud nonuniformities may play in particle cloud combustion. Macroscopically uniform, quiescent particle cloud systems (at very low gravitational levels and above) sustain processes which can render them nonuniform on both macroscopic and microscopic scales. It is found that a given macroscopically uniform, quiescent particle cloud flame system can display a range of microscopically nonuniform features which lead to a range of combustion features. Microscopically nonuniform particle cloud distributions are difficult experimentally to detect and characterize. A uniformly distributed lycopodium cloud of particle-enriched microscopic nonuniformities in reduced gravity displays a range of burning velocities for any given overall stoichiometry. The range of observed and calculated burning velocities corresponds to the range of particle enriched concentrations within a characteristic microscopic nonuniformity. Sedimentation effects (even in reduced gravity) are also examined.

  13. The role of adsorbed water on the friction of a layer of submicron particles

    USGS Publications Warehouse

    Sammis, Charles G.; Lockner, David A.; Reches, Ze’ev

    2011-01-01

    Anomalously low values of friction observed in layers of submicron particles deformed in simple shear at high slip velocities are explained as the consequence of a one nanometer thick layer of water adsorbed on the particles. The observed transition from normal friction with an apparent coefficient near μ = 0.6 at low slip speeds to a coefficient near μ = 0.3 at higher slip speeds is attributed to competition between the time required to extrude the water layer from between neighboring particles in a force chain and the average lifetime of the chain. At low slip speeds the time required for extrusion is less than the average lifetime of a chain so the particles make contact and lock. As slip speed increases, the average lifetime of a chain decreases until it is less than the extrusion time and the particles in a force chain never come into direct contact. If the adsorbed water layer enables the otherwise rough particles to rotate, the coefficient of friction will drop to μ = 0.3, appropriate for rotating spheres. At the highest slip speeds particle temperatures rise above 100°C, the water layer vaporizes, the particles contact and lock, and the coefficient of friction rises to μ = 0.6. The observed onset of weakening at slip speeds near 0.001 m/s is consistent with the measured viscosity of a 1 nm thick layer of adsorbed water, with a minimum particle radius of approximately 20 nm, and with reasonable assumptions about the distribution of force chains guided by experimental observation. The reduction of friction and the range of velocities over which it occurs decrease with increasing normal stress, as predicted by the model. Moreover, the analysis predicts that this high-speed weakening mechanism should operate only for particles with radii smaller than approximately 1 μm. For larger particles the slip speed required for weakening is so large that frictional heating will evaporate the adsorbed water and weakening will not occur.

  14. Molecular simulation study of role of polymer–particle interactions in the strain-dependent viscoelasticity of elastomers (Payne effect)

    SciTech Connect

    Chen, Yulong; Li, Ziwei; Wen, Shipeng; Zhang, Liqun; Yang, Qingyuan E-mail: LiuL@mail.buct.edu.cn; Zhong, Chongli; Liu, Li E-mail: LiuL@mail.buct.edu.cn

    2014-09-14

    The strain-amplitude dependence of viscoelastic behavior of model crosslinked elastomers containing various concentrations of spherical nanoparticles (NPs) was studied by non-equilibrium molecular dynamics simulation. All the filler NPs were in monodispersed state and the interactions between these particles were purely repulsive. The polymer–particle interactions were attractive and their interaction energies were tuned in a broad range. Through the computational study, many important features of the behavior of particle-reinforced elastomers observed in experiments, including the Payne effect, were successfully reproduced. It was shown that the magnitude of the Payne effect was found to depend on the polymer–particle interaction and the filler loading. By examining the microstructures of the simulation systems and their evolution during oscillatory shear, four different mechanisms for the role of the polymer–particle interactions in the Payne effect were revealed that consist of the debonding of polymer chains from NP surfaces, the breakage of polymer-shell-bridged NP network, the rearrangement of the NPs in the network into different layers and the shear-induced yielding of the rigid polymer shell in-between neighboring NPs.

  15. Jetting mechanisms of particles under shock wave acceleration: the role of force chains

    NASA Astrophysics Data System (ADS)

    Xue, Kun

    The particle jetting phenomenon is widely observed in many problems associated with blast/shock dispersal of granular materials, although its origin is still unidentified. We carried out discrete element simulations of the shock dispersal of two-dimensional particle rings in order to extract the particle-scale evolution of the shocked rings in terms of the velocity profile and the force-chain networks. Initially the force chains distribute uniformly along the circumference, but after several dozens of microseconds, they disseminate into a handful of blobs which mainly consist of long linear or branched chains align with the radial direction. These blobs are separated by zones featuring relatively sparse force chains which take forms of short chains or small compact polygons. The radial-like force chains in blobs serves as the channels transferring the momentum from the inner layers to outer layers, resulting in fast moving blocks without appreciable velocity differences. By contrast, the shock energy in the zones with short force chains is largely dissipated among the particle collision. Thus particles in these zones lag behind those bound by strong force chains. The resultant heterogeneous velocity profile acts as the precursor of the ensuing particle jetting.

  16. Fractal Characteristics of Soil Retention Curve and Particle Size Distribution with Different Vegetation Types in Mountain Areas of Northern China.

    PubMed

    Niu, Xiang; Gao, Peng; Wang, Bing; Liu, Yu

    2015-12-01

    Based on fractal theory, the fractal characteristics of soil particle size distribution (PSD) and soil water retention curve (WRC) under the five vegetation types were studied in the mountainous land of Northern China. Results showed that: (1) the fractal parameters of soil PSD and soil WRC varied greatly under each different vegetation type, with Quercus acutissima Carr. and Robina pseudoacacia Linn. mixed plantation (QRM) > Pinus thunbergii Parl. and Pistacia chinensis Bunge mixed plantation (PPM) > Pinus thunbergii Parl. (PTP) > Juglans rigia Linn. (JRL) > abandoned grassland (ABG); (2) the soil fractal dimensions of woodlands (QRM, PPM, PTP and JRL) were significantly higher than that in ABG, and mixed forests (QRM and PPM) were higher than that in pure forests (PTP and JRL); (3) the fractal dimension of soil was positively correlated with the silt and clay content but negatively correlated with the sand content; and (4) the fractal dimension of soil PSD was positively correlated with the soil WRC. These indicated that the fractal parameters of soil PSD and soil WRC could act as quantitative indices to reflect the physical properties of the soil, and could be used to describe the influences of the Return Farmland to Forests Projects on soil structure. PMID:26633458

  17. Fractal Characteristics of Soil Retention Curve and Particle Size Distribution with Different Vegetation Types in Mountain Areas of Northern China

    PubMed Central

    Niu, Xiang; Gao, Peng; Wang, Bing; Liu, Yu

    2015-01-01

    Based on fractal theory, the fractal characteristics of soil particle size distribution (PSD) and soil water retention curve (WRC) under the five vegetation types were studied in the mountainous land of Northern China. Results showed that: (1) the fractal parameters of soil PSD and soil WRC varied greatly under each different vegetation type, with Quercus acutissima Carr. and Robina pseudoacacia Linn. mixed plantation (QRM) > Pinus thunbergii Parl. and Pistacia chinensis Bunge mixed plantation (PPM) > Pinus thunbergii Parl. (PTP) > Juglans rigia Linn. (JRL) > abandoned grassland (ABG); (2) the soil fractal dimensions of woodlands (QRM, PPM, PTP and JRL) were significantly higher than that in ABG, and mixed forests (QRM and PPM) were higher than that in pure forests (PTP and JRL); (3) the fractal dimension of soil was positively correlated with the silt and clay content but negatively correlated with the sand content; and (4) the fractal dimension of soil PSD was positively correlated with the soil WRC. These indicated that the fractal parameters of soil PSD and soil WRC could act as quantitative indices to reflect the physical properties of the soil, and could be used to describe the influences of the Return Farmland to Forests Projects on soil structure. PMID:26633458

  18. Correlation between particle size and magnetic characteristics of Mn-substituted ZnFe2O4 ferrites

    NASA Astrophysics Data System (ADS)

    Zawar, Sidra; Atiq, Shahid; Riaz, Saira; Naseem, Shahzad

    2016-05-01

    We report synthesis of Zn1-xMnxFe2O4 (x = 0.0, 0.1, 0.3, 0.4 & 0.5) ferrites using sol-gel auto-combustion route while citric acid is used as a fuel. The study is aimed to explore the influence of Mn contents on structural parameters, morphological characteristics and magnetic properties of ZnFe2O4 ferrite samples while the impact of average grain dimensions on magnetic properties inferred from multi domain and single domain particle's effect is also analyzed. X-ray diffraction confirmed the configuration of single phase pure crystalline structure with low concentration of Mn while some impurity peaks were found for higher Mn contents. Lattice parameter was found to increase with increasing Mn contents while crystallite size was decreased. Average grain size was decreased from 240 to 150 nm with increasing Mn concentration which directly affected the magnetic properties. A decrease in saturation magnetization (from 52.35 to 45.80 emu/g) and an increase in coercivity (from 44 to 262 Oe) was observed with increasing Mn contents. A decrease in initial permeability and increase in hysteresis loss with increasing Mn contents was also evident. Coercive field and hysteresis losses were increased with decreasing average grain size while initial permeability was found to decrease with decrease in average grain size.

  19. Characteristic Times of Gradual Solar Energetic Particle Events and Their Dependence on Associated Coronal Mass Ejection Properties

    NASA Astrophysics Data System (ADS)

    Kahler, S. W.

    2005-08-01

    We use 20 MeV proton intensities from the EPACT instrument on Wind and coronal mass ejections (CMEs) from the LASCO coronagraph on SOHO observed during 1998-2002 to statistically determine three characteristic times of gradual solar energetic particle (SEP) events as functions of solar source longitude: (1) TO, the time from associated CME launch to SEP onset at 1 AU, (2) TR, the rise time from SEP onset to the time when the SEP intensity is a factor of 2 below peak intensity, and (3) TD, the duration over which the SEP intensity is within a factor of 2 of the peak intensity. Those SEP event times are compared with associated CME speeds, accelerations, and widths to determine whether and how the SEP event times may depend on the formation and dynamics of coronal/interplanetary shocks driven by the CMEs. Solar source longitudinal variations are clearly present in the SEP times, but TR and TD are significantly correlated with CME speeds only for SEP events in the best-connected longitude range. No significant correlations between the SEP times and CME accelerations are found except for TD in one longitude range, but there is a weak correlation of TR and TD with CME widths. We also find no correlation of any SEP times with the solar wind O+7/O+6 values, suggesting no dependence on solar wind stream type. The SEP times of the small subset of events occurring in interplanetary CMEs may be slightly shorter than those of all events.

  20. Role of the reaction of stabilized Criegee intermediates with peroxy radicals in particle formation and growth in air.

    PubMed

    Zhao, Yue; Wingen, Lisa M; Perraud, Véronique; Greaves, John; Finlayson-Pitts, Barbara J

    2015-05-21

    Ozonolysis of alkenes is an important source of secondary organic aerosol (SOA) in the atmosphere. However, the mechanisms by which stabilized Criegee intermediates (SCI) react to form and grow the particles, and in particular the contributions from oligomers, are not well understood. In this study, ozonolysis of trans-3-hexene (C6H12), as a proxy for small alkenes, was investigated with an emphasis on the mechanisms of particle formation and growth. Ozonolysis experiments were carried out both in static Teflon chambers (18-20 min reaction times) and in a glass flow reactor (24 s reaction time) in the absence and presence of OH or SCI scavengers, and under different relative humidity (RH) conditions. The chemical composition of polydisperse and size-selected SOA particles was probed using different mass spectrometric techniques and infrared spectroscopy. Oligomers having SCI as the chain unit are found to be the dominant components of such SOA particles. The formation mechanism for these oligomers suggested by our results follows the sequential addition of SCI to organic peroxy (RO2) radicals, in agreement with previous studies by Moortgat and coworkers. Smaller particles are shown to have a relatively greater contribution from longer oligomers. Higher O/C ratios are observed in smaller particles and are similar to those of oligomers resulting from RO2 + nSCI, supporting a significant role for longer oligomers in particle nucleation and early growth. Under atmospherically relevant RH of 30-80%, water vapor suppresses oligomer formation through scavenging SCI, but also enhances particle nucleation. Under humid conditions, or in the presence of formic or hydrochloric acid as SCI scavengers, peroxyhemiacetals are formed by the acid-catalyzed particle phase reaction between oligomers from RO2 + nSCI and a trans-3-hexene derived carbonyl product. In contrast to the ozonolysis of trans-3-hexene, oligomerization involving RO2 + nSCI does not appear to be prevalent in the

  1. Sociodemographic Characteristics and Waking Activities and their Role in the Timing and Duration of Sleep

    PubMed Central

    Basner, Mathias; Spaeth, Andrea M.; Dinges, David F.

    2014-01-01

    will need to be offset. Raising awareness of the importance of sufficient sleep for health and safety may be necessary to positively influence discretionary behaviors that reduce sleep time, including television viewing and morning grooming. Citation: Basner M, Spaeth AM, Dinges DF. Sociodemographic characteristics and waking activities and their role in the timing and duration of sleep. SLEEP 2014;37(12):1889-1906. PMID:25325472

  2. Role of particle masses in the magnetic field generation driven by the parity violating interaction

    NASA Astrophysics Data System (ADS)

    Dvornikov, Maxim

    2016-09-01

    Recently the new model for the generation of strong large scale magnetic fields in neutron stars, driven by the parity violating interaction, was proposed. In this model, the magnetic field instability results from the modification of the chiral magnetic effect in presence of the electroweak interaction between ultrarelativistic electrons and nucleons. In the present work we study how a nonzero mass of charged particles, which are degenerate relativistic electrons and nonrelativistic protons, influences the generation of the magnetic field in frames of this approach. For this purpose we calculate the induced electric current of these charged particles, electroweakly interacting with background neutrons and an external magnetic field, exactly accounting for the particle mass. This current is calculated by two methods: using the exact solution of the Dirac equation for a charged particle in external fields and computing the polarization operator of a photon in matter composed of background neutrons. We show that the induced current is vanishing in both approaches leading to the zero contribution of massive particles to the generated magnetic field. We discuss the implication of our results for the problem of the magnetic field generation in compact stars.

  3. The role of interparticle interaction and environmental coupling in a two-particle open quantum system.

    PubMed

    Laguna, Humberto G; Sagar, Robin P; Tempel, David G; Aspuru-Guzik, Alán

    2016-01-01

    The effects of bath coupling on an interacting two-particle quantum system are studied using tools from information theory. Shannon entropies of the one (reduced) and two-particle distribution functions in position, momentum and separable phase-space are examined. Results show that the presence of the bath leads to a delocalization of the distribution functions in position space, and a localization in momentum space. This can be interpreted as a loss of information in position space and a gain of information in momentum space. The entropy sum of the system, in the presence of a bath, is shown to be dependent on the strength of the interparticle potential and also on the strength of the coupling to the bath. The statistical correlation between the particles, and its dependence on the bath and interparticle potential, is examined using mutual information. A stronger repulsive potential between particles, in the presence of the bath, yields a smaller correlation between the particles positions, and a larger one between their momenta. PMID:26616490

  4. PROPAGATION OF SOLAR ENERGETIC PARTICLES IN THREE-DIMENSIONAL INTERPLANETARY MAGNETIC FIELDS: IN VIEW OF CHARACTERISTICS OF SOURCES

    SciTech Connect

    He, H.-Q.; Qin, G.; Zhang, M. E-mail: gqin@spaceweather.ac.cn

    2011-06-20

    In this paper, a model of solar energetic particle (SEP) propagation in the three-dimensional Parker interplanetary magnetic field is calculated numerically. We study the effects of the different aspects of particle sources on the solar surface, which include the source location, coverage of latitude and longitude, and spatial distribution of source particle intensity, on propagation of SEPs with both parallel and perpendicular diffusion. We compute the particle flux and anisotropy profiles at different observation locations in the heliosphere. From our calculations, we find that the observation location relative to the latitudinal and longitudinal coverage of particle source has the strongest effects on particle flux and anisotropy profiles observed by a spacecraft. When a spacecraft is directly connected to the solar sources by the interplanetary magnetic field lines, the observed particle fluxes are larger than when the spacecraft is not directly connected. This paper focuses on the situations when a spacecraft is not connected to the particle sources on the solar surface. We find that when the magnetic footpoint of the spacecraft is farther away from the source, the observed particle flux is smaller and its onset and maximum intensity occur later. When the particle source covers a larger range of latitude and longitude, the observed particle flux is larger and appears earlier. There is east-west azimuthal asymmetry in SEP profiles even when the source distribution is east-west symmetric. However, the detail of particle spatial distribution inside the source does not affect the profile of the SEP flux very much. When the magnetic footpoint of the spacecraft is significantly far away from the particle source, the anisotropy of particles in the early stage of an SEP event points toward the Sun, which indicates that the first arriving particles come from outside of the observer through perpendicular diffusion at large radial distances.

  5. Distribution characteristics of phenanthrene in the water, suspended particles and sediments from Yangtze River under hydrodynamic conditions.

    PubMed

    Wang, Lili; Shen, Zhenyao; Wang, Hongyuan; Niu, Junfeng; Lian, Guoxi; Yang, Zhifeng

    2009-06-15

    The effects of aquatic sediment concentrations, grain size distribution and hydrodynamic conditions on sorption behavior of phenanthrene (PHE) on sediments collected from Yangtze River (Wuhan catchment) were investigated. The results showed that the sorption behavior of PHE was mainly affected by the organic carbon in different phases, i.e. organic carbon contents (f(oc)) (w/w, organic carbon/dry weight sediment) in the sediments and dissolved organic carbon (DOC) in liquid phase. In this study, sediments were subjected to artificial resuspension under turbulent diffusion coefficients being 24.6, 29.5 and 46.2 cm(2)s(-1) corresponded to 0.4, 0.3 and 0.2 s cycle(-1) of the perforated grids, respectively, which were driven by variable speed motor with 150, 180 and 280 rotation per minute (rpm). The suspended particle concentration increased from 1.01 to 6.70 g L(-1) as the hydrodynamic strength increased from 150 to 280 rpm, whereas PHE concentration in liquid phase decreased from 0.56 to 0.34 microg mL(-1). The amount of DOC was supposed to play an important role in the partition of PHE under hydrodynamic conditions. Moreover, a sorption dynamic model was developed based on the linear isotherm expression and law of conservation of mass. The model was validated by PHE sorption behavior acquired with three different hydrodynamic conditions and the predicted values displayed satisfying accordance with experimental data. PMID:19022579

  6. Child sexual abuse, attachment style, and depression: the role of the characteristics of abuse.

    PubMed

    Cantón-Cortés, David; Cortés, María Rosario; Cantón, José

    2015-02-01

    The aim of the current study was to examine the effects of secure, avoidant, and anxious attachment styles on depressive symptomatology in child sexual abuse (CSA) among young female adult victims. The role of attachment style was studied by considering possible interactive effects with the type of abuse, the relationship with the perpetrator, and the continuity of abuse. Participants were 168 female victims of CSA. Information about the abuse was obtained from a self-reported questionnaire. Attachment style was assessed with the Attachment Style Measure (ASM), and the Beck Depression Inventory (BDI) was used to assess depressive symptomatology. Secure and anxious attachment styles were correlated with low and high depression scores respectively. The effects of attachment style were stronger in cases where the abuse consisted of oral sex/penetration, a non-family member as perpetrator, and in isolated, compared with continued, abuse. These results confirm that characteristics of CSA (type of abuse, relationship with the perpetrator, and continuity of abuse) can affect the impact of attachment style on depressive symptomatology. PMID:24958133

  7. Pay or conditions? The role of workplace characteristics in nurses' labor supply.

    PubMed

    Eberth, Barbara; Elliott, Robert F; Skåtun, Diane

    2016-07-01

    Empirically rigorous studies of nursing labor supply have to date relied on extant secondary data and focused almost exclusively on the role of pay. Yet the conditions under which nurses work and the timing and convenience of the hours they work are also important determinants of labor supply. Where there are national pay structures and pay structures are relatively inflexible, as in nursing in European countries, these factors become more important. One of the principal ways in which employers can improve the relative attractiveness of nursing jobs is by changing these other conditions of employment. This study uses new primary data to estimate an extended model of nursing labor supply. It is the first to explore whether and how measures of non-pecuniary workplace characteristics and observed individual (worker) heterogeneity over non-pecuniary job aspects impact estimates of the elasticity of hours with respect to wages. Our results have implications for the future sustainability of an adequately sized nurse workforce and patient care especially at a time when European healthcare systems are confronted with severe financial pressures that have resulted in squeezes in levels of healthcare funding. PMID:26453574

  8. [Oxalobacter formigenes--characteristics and role in development of calcium oxalate urolithiasis].

    PubMed

    Torzewska, Agnieszka

    2013-01-01

    Microorganisms are one of the important factors for urinary calculi formation. While urease-positive bacteria and nanobacteria contribute to stone formation, Oxalobacter formigenes rods play a protective role against the development of urolithiasis. Proteus mirabilis alkaline environment of the urinary tract and cause crystallization mainly of struvite (magnesium ammonium phosphate). However, nanobacteria, due to the possibility of apatite deposition on the surface of their cells, have long been considered as an etiological factor of urinary calculi consisting of calcium phosphates. O. formigenes is an anaerobe using oxalate as the main source of carbon and energy and occurs as natural gastrointestinal microflora of humans and animals. These bacteria control the amount of oxalate excretion degrading oxalates and regulating their transport by intestinal epithelium. Lower colonization of the human colon by O. formigenes can cause increased oxalate excretion and lead to the development of oxalate urolithiasis. Due to the positive influence of O. formigenes, there is ongoing research into the use of this microorganism as a probiotic in the prophylaxis or treatment of hyperoxaluria, both secondary and primary. The results of these studies are very promising, but they still require continuation. Future studies focus on the exact characteristics of O. formigenes including their metabolism and the development of methods for applying as a therapeutic agent the bacteria or their enzymes degrading the oxalate. PMID:24379255

  9. Quasi-particle spectrum in trilayer graphene: Role of onsite coulomb interaction and interlayer coupling

    NASA Astrophysics Data System (ADS)

    Kumar, Sanjay; Ajay

    2015-01-01

    Stacking dependent quasi-particle spectrum and density of states (DOS) in trilayer (ABC-, ABA- and AAA-stacked) graphene are analyzed using mean-field Green's function equations of motion method. Interlayer coupling (t1) is found to be responsible for the splitting of quasi-particle peaks in each stacking order. Coulomb interaction suppresses the trilayer splitting and generates a finite gap at Fermi level in ABC- while a tiny gap in ABA-stacked trilayer graphene. Influence of t⊥ is prominent for AAA-stacking as compared to ABC- and ABA-stacking orders. The theoretically obtained quasi-particle energies and DOS has been viewed in terms of recent angle resolved photoemission spectroscopic (ARPES) and scanning tunneling microscopic (STM) data available on these systems.

  10. Molecular dynamics simulation for the cluster formation process of Lennard-Jones particles: Magic numbers and characteristic features

    NASA Astrophysics Data System (ADS)

    Ikeshoji, Tamio; Hafskjold, Bjørn; Hashi, Yuichi; Kawazoe, Yoshiyuki

    1996-09-01

    Cluster formation of Lennard-Jones particles (65 536 atoms in a unit cell with an overall number density equal to 0.0149) was simulated by molecular dynamics. The temperature was set to decrease linearly with time by various thermostats, starting from a gas state temperature and ending at zero temperature. With the Nosé-Hoover thermostat, it was found that the translational temperature of the clusters suddenly decreased almost to zero when the cluster formation drastically increased around a reduced temperature (T*) of 0.5, while the internal temperature decreased linearly. Using the Andersen thermostat, which could simulate the aggregation of particles in an inert gas, both the internal and translational temperatures decreased almost linearly with time. When these thermostats were used, cluster-cluster and cluster-atom collisions did not give any magic number peaks in the size distribution up to 250 atoms/cluster at any temperature. Careful tracing of the cluster growth of 13-atom clusters showed no difference in reactivity between icosahedral and nonicosahedral clusters. To simulate cooling in a supersonic jet, a thermostat which controlled only the translational temperature was introduced. After the clusters were formed by cooling the system with this thermostat, their internal temperature stayed at T*≊0.5, while the translational temperature decreased linearly to zero with time as it was controlled. A long-time evaporation from these high-temperature clusters gave peaks at 13 and 19 (and less significantly at 23 and 26) which are magic number sizes corresponding to single, double, triple, and quadruple icosahedra, respectively. The internal temperatures of 13- and 19-atom clusters were higher than those of other size clusters. Higher evaporation energy was observed for the clusters of 13, 19, 23, and 26 atoms than for other size clusters after the long-time evaporation, but only the 13-atom clusters had the higher evaporation energy after cooling by the

  11. Platelet-adenovirus vs. inert particles interaction: effect on aggregation and the role of platelet membrane receptors.

    PubMed

    Gupalo, Elena; Kuk, Cynthia; Qadura, Mohammad; Buriachkovskaia, Liudmila; Othman, Maha

    2013-01-01

    Platelets are involved in host defense via clearance of bacteria from the circulation, interaction with virus particles, and uptake of various size particulates. There is a growing interest in micro- and nanoparticles for drug delivery and there is evidence that the properties of these particles critically influence their interaction and uptake by various tissues and cells including platelets. Virus mediated gene therapy applications are still challenged by the resultant thrombocytopenia and the mechanism(s) of platelet-foreign particles interaction remains unclear. We studied the specifics of platelet interaction with an active biological agent (adenovirus) and inert latex microspheres (MS) and investigated the role of platelet proteins in this interaction. We show that activated and not resting platelets internalize MS, without influencing platelet aggregation. In contrast, adenovirus induces and potentiates ADP-induced platelet aggregation and results in rapid expression of P-selectin. Platelets then internalize adenovirus and viral particles appear inside the open canalicular system. Inhibition of platelet αIIbβ3, GPIbα, and P-selectin decreases both platelet aggregation and internalization of MS. Inhibition of αIIbβ3 and αVβ3 does not abolish adenovirus platelet internalization and adenovirus-induced platelet activation is maintained. Our study demonstrates that platelets react differentially with foreign particles and that αIIbβ3 is a key player in platelet engulfing of foreign particles but not in mediating adenovirus internalization. Other platelet candidate molecules remain to be investigated as potential targets for management of adenovirus-induced thrombocytopenia. PMID:22812520

  12. Physical and Optical/Radiative Characteristics of Aerosol and Cloud Particles in Tropical Cirrus: Importance in Radiation Balance

    NASA Technical Reports Server (NTRS)

    Pueschel, R. F.; Howard, S. D.; Foster, T. C.; Hallett, J.; Arnott, W. P.; Condon, Estelle P. (Technical Monitor)

    1996-01-01

    Whether cirrus clouds heat or cool the Earth-atmosphere system depends on the relative importance of the cloud shortwave albedo effect and the cloud thermal greenhouse effect. Both are determined by the distribution of ice condensate with cloud particle size. The microphysics instrument package flown aboard the NASA DC-8 in TOGA/COARE included an ice crystal replicator, a 2D Greyscale Cloud Particle Probe and a Forward Scattering Spectrometer Aerosol Probe. In combination, the electro-optical instruments permitted particle size measurements between 0.5 micrometer and 2.6 millimeter diameter. Ice crystal replicas were used to validate signals from the electrooptical instruments. Both optical and scanning electron microscopy were utilized to analyze aerosol and ice particle replicas between 0.1 micrometer and several 100 micrometer diameter. In first approximation, the combined aerosol-cloud particle spectrum in several clouds followed a power law N alpha D(sup -2.5). Thus, large cloud particles carried most of the condensate mass, while small cloud and aerosol particles determined the surface area. The mechanism of formation of small particles is growth of (hygroscopic, possibly ocean-derived) aerosol particles along the Kohler curves. The concentration of small particles is higher and less variable in space and time, and their tropospheric residence time is longer, than those of large cloud particles because of lower sedimentation velocities. Small particles shift effective cloud particle radii to sizes much smaller than the mean diameter of the cloud particles. This causes an increase in shortwave reflectivity and IR emissivity, and a decrease in transmissivity. Occasionally, the cloud reflectivity increased with altitude (decreasing temperature) stronger than did cloud emissivity, yielding enhanced radiative cooling at higher altitudes. Thus, cirrus produced by deep convection in the tropics may be critical in controlling processes whereby energy from warm

  13. Physical properties and structure of fine core-shell particles used as packing materials for chromatography relationships between particle characteristics and column performance

    SciTech Connect

    Gritti, Fabrice; Guiochon, Georges A

    2010-01-01

    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 physical properties that set them apart from conventional porous particles. The kinetic performance of 4.6 mm I.D. columns packed with these two new materials is analyzed based on the results of a series of nine independent and complementary experiments: low-temperature nitrogen adsorption (LTNA), scanning electron microscopy (SEM), inverse size-exclusion chromatography (ISEC), Coulter counter particle size distributions, pycnometry, height equivalent to a theoretical plate (HETP), peak parking method (PP), total pore blocking method (TPB), and local electrochemical detection across the column exit section (LED). The results of this work establish links between the physical properties of these superficially porous particles and the excellent kinetic performance of columns packed with them. It clarifies the fundamental origin of the difference in the chromatographic performances of the Halo and the Kinetex columns.

  14. Climate change and agricultural risk management: the role of the family-farm characteristics

    NASA Astrophysics Data System (ADS)

    Quaranta, G.; Salvia, R.

    2009-04-01

    incidence and distribution of natural events, constitutes the theoretical background of the emphasis posed on social agents. Innovative interpretative frameworks, derived from this paradigm, are necessary in order to reshape both management approaches and policy elaboration. Local authorities and local actors should increase awareness and have suitable and new tools to improve the management and to mitigate the risks impacts on agro-natural resources where the role of the social agents is explicitly acknowledged. Mitigation and adaptation strategies should be shaped mainly taking in account the end-users characteristics. The framework presented and discussed in this paper internalizes the social agents perspective recognizing that perception of the risks in the agricultural sector may affect the farmers compliance decision and the level of management practices undertaken. Therefore the intensity of management practices both structural and non-structural has captured in two participatory stages: a model of perception in the first stage and a model of adoption (compliance) and the level of adoption of management practices. In the first stage the factors that condition the farmer perception of the risk linked to water availability are examined. The factors considered are household-specific elements that influence diffusion of information, social capital, farm assets, labour force characteristics. The second stage is finalized to examine the factors that determine the rate of adoption. The methodology has been used in a pilot area of Southern Italy and it has demonstrated to be very effective in depicting farm behaviours definitely showing a great attitude to be utilized for policies ex-ante evaluation and rural policies formulation.

  15. Airborne Particles: What We Have Learned About Their Role in Climate from Remote Sensing, and Prospects for Future Advances

    NASA Technical Reports Server (NTRS)

    Kahn, Ralph A.

    2013-01-01

    Desert dust, wildfire smoke, volcanic ash, biogenic and urban pollution particles, all affect the regional-scale climate of Earth in places and at times; some have global-scale impacts on the column radiation balance, cloud properties, atmospheric stability structure, and circulation patterns. Remote sensing has played a central role in identifying the sources and transports of airborne particles, mapping their three-dimensional distribution and variability, quantifying their amount, and constraining aerosol air mass type. The measurements obtained from remote sensing have strengths and limitations, and their value for characterizing Earths environment is enhanced immensely when they are combined with direct, in situ observations, and used to constrain aerosol transport and climate models. A similar approach has been taken to study the role particles play in determining the climate of Mars, though based on far fewer observations. This presentation will focus what we have learned from remote sensing about the impacts aerosol have on Earths climate; a few points about how aerosols affect the climate of Mars will also be introduced, in the context of how we might assess aerosol-climate impacts more generally on other worlds.

  16. Role of polyethylene particles in peri-prosthetic osteolysis: A review

    PubMed Central

    Atkins, Gerald J; Haynes, David R; Howie, Donald W; Findlay, David M

    2011-01-01

    There is convincing evidence that particles produced by the wear of joint prostheses are causal in the peri-prosthetic loss of bone, or osteolysis, which, if it progresses, leads to the phenomenon of aseptic loosening. It is important to fully understand the biology of this bone loss because it threatens prosthesis survival, and loosened implants can result in peri-prosthetic fracture, which is disastrous for the patient and presents a difficult surgical scenario. The focus of this review is the bioactivity of polyethylene (PE) particles, since there is evidence that these are major players in the development and progression of osteolysis around prostheses which use PE as the bearing surface. The review describes the biological consequences of interaction of PE particles with macrophages, osteoclasts and cells of the osteoblast lineage, including osteocytes. It explores the possible cellular mechanisms of action of PE and seeks to use the findings to date to propose potential non-surgical treatments for osteolysis. In particular, a non-surgical approach is likely to be applicable to implants containing newer, highly cross-linked PEs (HXLPEs), for which osteolysis seems to occur with much reduced PE wear compared with conventional PEs. The caveat here is that we know little as yet about the bioactivity of HXLPE particles and addressing this constitutes our next challenge. PMID:22474627

  17. The Role of Pressure Anisotropy on Particle Acceleration during Magnetic Reconnection

    NASA Astrophysics Data System (ADS)

    Schoeffler, K. M.; Drake, J. F.; Swisdak, M.; Knizhnik, K.

    2013-02-01

    Voyager spacecraft observations have revealed that contrary to expectations, the source of anomalous cosmic rays (ACRs) is not at the local termination shock. A possible mechanism of ACR acceleration is magnetic reconnection in the heliosheath. Using a particle-in-cell code, we investigate the effects of β on reconnection-driven particle acceleration by studying island growth in multiple interacting Harris current sheets. Many islands are generated, and particles are dominantly heated through Fermi reflection in contracting islands during island growth and merging. There is a striking difference between the heating of electrons versus the heating of ions. There is a strong dependence of β on electron heating, while the ion heating is insensitive to β. Anisotropies develop with T ∥ ≠ T for both electrons and ions. The electron anisotropies support the development of a Weibel instability that suppresses the Fermi acceleration of the electrons. Since the Weibel instability develops at a larger T ∥/T in lower β systems, electrons are able to accelerate more efficiently by the Fermi mechanism at low β. The variance in anisotropy implies less electron acceleration in higher β systems, and thus less heating. This study sheds light on particle acceleration mechanisms within the sectored magnetic field regions of the heliosheath and the dissipation of turbulence such as that produced by the magnetorotational instability in accreting systems.

  18. BACTERIOPLANKTON DYNAMICS IN NORTHERN SAN FRANCISCO BAY: ROLE OF PARTICLE ASSOCIATION AND SEASONAL FRESHWATER FLOW

    EPA Science Inventory

    Bacterioplankton abundance and metabolic characteristics were observed in northern San Francisco Bay, California, during spring and summer 1996 at three sites: Central Bay, Suisun Bay, and the Sacramento River. These sites spanned a salinity gradient from marine to freshwater, an...

  19. On the road to self-sputtering in high power impulse magnetron sputtering: particle balance and discharge characteristics

    NASA Astrophysics Data System (ADS)

    Huo, Chunqing; Lundin, Daniel; Raadu, Michael A.; Anders, André; Tomas Gudmundsson, Jon; Brenning, Nils

    2014-04-01

    The onset and development of self-sputtering (SS) in a high power impulse magnetron sputtering (HiPIMS) discharge have been studied using a plasma chemical model and a set of experimental data, taken with an aluminum target and argon gas. The model is tailored to duplicate the discharge in which the data are taken. The pulses are long enough to include both an initial transient and a following steady state. The model is used to unravel how the internal discharge physics evolves with pulse power and time, and how it is related to features in the discharge current-voltage-time characteristics such as current densities, maxima, kinks and slopes. The connection between the self-sputter process and the discharge characteristics is quantified and discussed in terms of three parameters: a critical target current density Jcrit based on the maximum refill rate of process (argon) gas above the target, an SS recycling factor ΠSS-recycle, and an approximation \\tilde{\\alpha} of the probabilities of ionization of species that come from the target (both sputtered metal and embedded argon atoms). For low power pulses, discharge voltages UD ⩽ 380 V with peak current densities below ≈ 0.2 A cm-2, the discharge is found to be dominated by process gas sputtering. In these pulses there is an initial current peak in time, associated with partial gas rarefaction, which is followed by a steady-state-like plateau in all parameters similar to direct current magnetron sputtering. In contrast, high power pulses, with UD ⩾ 500 V and peak current densities above JD ≈ 1.6 A cm-2, make a transition to a discharge mode where SS dominates. The transition is found not to be driven by process gas rarefaction which is only about 10% at this time. Maximum gas rarefaction is found later in time and always after the initial peak in the discharge current. With increasing voltage, and pulse power, the discharge can be described as following a route where the role of SS increases in four steps

  20. Sub-micron particle number size distributions characteristics at an urban location, Kanpur, in the Indo-Gangetic Plain

    NASA Astrophysics Data System (ADS)

    Kanawade, V. P.; Tripathi, S. N.; Bhattu, Deepika; Shamjad, P. M.

    2014-10-01

    We present long-term measurements of sub-micron particle number size distributions (PNSDs) conducted at an urban location, Kanpur, in India, from September 2007 to July 2011. The mean Aitken mode (NAIT), accumulation mode (NACCU), the total particle (NTOT), and black carbon (BC) mass concentrations were 12.4 × 103 cm- 3, 18.9 × 103 cm- 3, 31.9 × 103 cm- 3, and 7.96 μg m- 3, respectively, within the observed range at other urban locations worldwide, but much higher than those reported at urban sites in the developed nations. The total particle volume concentration appears to be dominated mainly by the accumulation mode particles, except during the monsoon months, perhaps due to efficient wet deposition of accumulation mode particles by precipitation. At Kanpur, the diurnal variation of particle number concentrations was very distinct, with highest during morning and late evening hours, and lowest during the afternoon hours. This behavior could be attributed to the large primary emissions of aerosol particles and temporal evolution of the planetary boundary layer. A distinct seasonal variation in the total particle number and BC mass concentrations was observed, with the maximum in winter and minimum during the rainy season, however, the Aitken mode particles did not show a clear seasonal fluctuation. The ratio of Aitken to accumulation mode particles, NAIT/NACCU, was varied from 0.1 to 14.2, with maximum during April to September months, probably suggesting the importance of new particle formation processes and subsequent particle growth. This finding suggests that dedicated long-term measurements of PNSDs (from a few nanometer to one micron) are required to systematically characterize new particle formation over the Indian subcontinent that has been largely unstudied so far. Contrarily, the low NAIT/NACCU during post-monsoon and winter indicated the dominance of biomass/biofuel burning aerosol emissions at this site.

  1. Children exposure assessment to ultrafine particles and black carbon: The role of transport and cooking activities

    NASA Astrophysics Data System (ADS)

    Buonanno, G.; Stabile, L.; Morawska, L.; Russi, A.

    2013-11-01

    An accurate evaluation of the airborne particle dose-response relationship requires detailed measurements of the actual particle concentration levels that people are exposed to, in every microenvironment in which they reside. The aim of this work was to perform an exposure assessment of children in relation to two different aerosol species: ultrafine particles (UFPs) and black carbon (BC). To this purpose, personal exposure measurements, in terms of UFP and BC concentrations, were performed on 103 children aged 8-11 years (10.1 ± 1.1 years) using hand-held particle counters and aethalometers. Simultaneously, a time-activity diary and a portable GPS were used to determine the children's daily time-activity pattern and estimate their inhaled dose of UFPs and BC. The median concentration to which the study population was exposed was found to be comparable to the high levels typically detected in urban traffic microenvironments, in terms of both particle number (2.2 × 104 part. cm-3) and BC (3.8 μg m-3) concentrations. Daily inhaled doses were also found to be relatively high and were equal to 3.35 × 1011 part. day-1 and 3.92 × 101 μg day-1 for UFPs and BC, respectively. Cooking and using transportation were recognized as the main activities contributing to overall daily exposure, when normalized according to their corresponding time contribution for UFPs and BC, respectively. Therefore, UFPs and BC could represent tracers of children exposure to particulate pollution from indoor cooking activities and transportation microenvironments, respectively.

  2. Role of sediment characteristics on natural radiation level of the Vaigai river sediment, Tamilnadu, India.

    PubMed

    Ramasamy, V; Paramasivam, K; Suresh, G; Jose, M T

    2014-01-01

    The sediment characteristics such as granulometric contents (sand, silt and clay), organic matter, magnetic susceptibility (low and high frequency) and weight percentage of magnetic minerals and the natural radionuclide ((238)U, (232)Th and (40)K) contents have been analyzed for the sediment samples of Vaigai river with an aim of evaluating the radiation hazard nature and assessing characterization of sediment. Granulometric analysis confirmed that the sand is major content. The organic matter content is ranged from 0.30 to 8.62% and comparison shows that the present river has high organic content. The magnetic measurement results indicated that the sites S16, S18 and S25 may be affected anthropogenically. Frequency dependence magnetic susceptibility is calculated to know the contribution of grains to magnetic susceptibility. Average of activity concentrations (except (40)K) and all calculated radiological parameters are within the recommended level. Multivariate statistical analyses (Pearson correlation, cluster and factor analysis) dictated that the role of sediment characteristics on the level of radioactivity in the river sediments. The content of organic matter and clay, and magnetic parameters are positively correlated with important radioactive variables. The measurement of organic matter and magnetic susceptibility in various granulometric contents show some higher values in silt and clay fractions. Radioactivity level was also measured for the samples (after removing silt and clay fractions from bulk samples) and the results show decrease in radioactive variables. The present study stated that the lower grain sized fractions have the ability to absorb the contents such as organic content and magnetic minerals as cations on their surface and raise the level of radioactivity. Percentage of decrease in the natural radionuclides of (238)U, (232)Th, (40)K and absorbed dose rate of the samples (after removing the silt and clay fractions from bulk samples) to the

  3. U{sup BF}(5) to SU{sup BF}(3) shape phase transition in odd nuclei for j=1/2, 3/2, and 5/2 orbits: The role of the odd particle at the critical point

    SciTech Connect

    Alonso, C. E.; Arias, J. M.; Fortunato, L.; Vitturi, A.

    2009-01-15

    We investigate the phase transition in odd nuclei within the Interacting Boson Fermion Model in correspondence with the transition from spherical to stable axially deformed shape. The odd particle is assumed to be moving in the single-particle orbitals with angular momenta j=1/2,3/2,5/2 with a boson-fermion Hamiltonian that leads to the occurrence of the SU{sup BF}(3) boson-fermion symmetry when the boson part approaches the SU(3) condition. Both energy spectra and electromagnetic transitions show characteristic patterns similar to those displayed by the even nuclei at the corresponding critical point. The role of the additional particle in characterizing the properties of the critical points in finite quantal systems is investigated by resorting to the formalism based on the intrinsic frame.

  4. Symptoms of Depression and Anxiety in Adolescents with Sickle Cell Disease: The Role of Intrapersonal Characteristics and Stress Processing Variables

    ERIC Educational Resources Information Center

    Simon, Katherine; Barakat, Lamia P.; Patterson, Chavis A.; Dampier, Carlton

    2009-01-01

    Sickle cell disease (SCD) complications place patients at risk for poor psychosocial adaptation, including depression and anxiety symptoms. This study aimed to test a mediator model based on the Risk and Resistance model to explore the role of intrapersonal characteristics and stress processing variables in psychosocial functioning. Participants…

  5. The role of acid-base effects on particle charging in apolar media.

    PubMed

    Gacek, Matthew Michael; Berg, John C

    2015-06-01

    The creation and stabilization of electric charge in apolar environments (dielectric constant≈2) have been an area of interest dating back to when an explanation was sought for the occurrence of what are now known as electrokinetic explosions during the pumping of fuels. More recently attention has focused on the charging of suspended particles in such media, underlying such applications as electrophoretic displays (e.g., the Amazon Kindle® reader) and new printing devices (e.g., the HP Indigo® Digital Press). The endeavor has been challenging owing to the complexity of the systems involved and the large number of factors that appear to be important. A number of different, and sometimes conflicting, theories for particle surface charging have been advanced, but most observations obtained in the authors' laboratory, as well as others, appear to be explainable in terms of an acid-base mechanism. Adducts formed between chemical functional groups on the particle surface and monomers of reverse micelle-forming surfactants dissociate, leaving charged groups on the surface, while the counter-charges formed are sequestered in the reverse micelles. For a series of mineral oxides in a given medium with a given surfactant, surface charging (as quantified by the maximum electrophoretic mobility or zeta potential obtained as surfactant concentration is varied) was found to scale linearly with the aqueous PZC (or IEP) values of the oxides. Different surfactants, with the same oxide series, yielded similar behavior, but with different PZC crossover points between negative and positive particle charging, and different slopes of charge vs. PZC. Thus the oxide series could be used as a yardstick to characterize the acid-base properties of the surfactants. This has led directly to the study of other materials, including surface-modified oxides, carbon blacks, pigments (charge transfer complexes), and polymer latices. This review focuses on the acid-base mechanism of particle

  6. Temporal Evolution of Spectral and Angular Characteristics of SEP Particles during Several GLEs of Solar Cycle 23 Derived from NM Data

    NASA Astrophysics Data System (ADS)

    Mishev, Alexander; Usoskin, Ilya; Kocharov, Leon

    High-energy charged particles of solar origin could represent a severe radiation risk for astronauts and air crew. In addition, they could disrupt technological systems. When a ground-based neutron monitor register abrupt increases in solar energetic particles (SEPs), we observe a special case of solar energetic particle event, a ground-level enhancement (GLE). In order to derive the spectral and angular characteristics of GLE particles a precise computation of solar energetic particle propagation in the Earth's magnetosphere and atmosphere is necessary. It consists of detailed computation of assymptotic cones for neutron monitors (NMs) and application of inverse method using the newly computed neutron monitor yield function. Assymptotic directions are computed using the Planetocosmics code and realistic magnetospheric models, namely IGRF as the internal model and Tsyganenko 89 with the corresponding Kp index as the external one. The inverse problem solution is performed on the basis of non-linear least squares method, namely Levenberg-Marqurdt. In the study presented here, we analyse several major GLEs of the solar cycle 23 as well as the first GLE event of the solar cycle 24, namely GLE69, GLE70 and GLE 71. The SEP spectra and pitch angle distribution are obtained at different momenta since the event's onset. The obtained characteristics are compared with previously reported results. The obtained results are briefly discussed.

  7. Roles of Clinician, Patient, and Community Characteristics in the Management of Pediatric Upper Respiratory Tract Infections

    PubMed Central

    Yaeger, Jeffrey P.; Temte, Jonathan L.; Hanrahan, Lawrence P.; Martinez-Donate, P.

    2015-01-01

    PURPOSE Prior studies have evaluated factors predictive of inappropriate antibiotic prescription for upper respiratory tract infections (URIs). Community factors, however, have not been examined. The aim of this study was to evaluate the roles of patient, clinician, and community factors in predicting appropriate management of URIs in children. METHODS We used a novel database exchange, linking electronic health record data with community statistics, to identify all patients aged 3 months to 18 years in whom URI was diagnosed in the period from 2007 to 2012. We followed the Healthcare Effectiveness Data and Information Set (HEDIS) quality measurement titled “Appropriate treatment for children with upper respiratory infection” to determine the rate of appropriate management of URIs. We then stratified data across individual and community characteristics and used multiple logistic regression modeling to identify variables that independently predicted antibiotic prescription. RESULTS Of 20,581 patients, the overall rate for appropriate management for URI was 93.5%. Family medicine clinicians (AOR = 1.5; 95% CI 1.31, 1.71; reference = pediatric clinicians), urgent care clinicians (AOR = 2.23; 95% CI 1.93, 2.57; reference = pediatric clinicians), patients aged 12 to 18 years (AOR = 1.44; 95% CI 1.25, 1.67; reference = age 3 months to 4 years), and patients of white race/ ethnicity (AOR = 1.83; 95% CI 1.41, 2.37; reference = black non-Hispanic) were independently predictive of antibiotic prescription. No community factors were independently predictive of antibiotic prescription. CONCLUSIONS Results correlate with prior studies in which non-pediatric clinicians and white race/ethnicity were predictive of antibiotic prescription, while association with older patient age has not been previously reported. Findings illustrate the promise of linking electronic health records with community data to evaluate health care disparities. PMID:26553892

  8. The role of HZE particles in space flight: results from spaceflight and ground-based experiments.

    PubMed

    Bucker, H; Facius, R

    1981-01-01

    Selected results from experiments investigating the potentially specific radiobiological importance of the cosmic HZE (= high Z, energetic) particles are discussed. Results from the Biostack space flight experiments, which were designed to meet the experimental requirements imposed by the microdosimetric nature of this radiation field, clearly indicate the existence of radiation mechanisms which become effective only at higher values of LET (linear energy transfer). Accelerator irradiation studies are reviewed which conform with this conjecture. The recently discovered production of "micro-lesions" in mammalian tissues by single HZE particles is possibly the most direct evidence. Open questions concerning the establishment of radiation standards for manned spaceflight, such as late effects, interaction with flight dynamic parameters, and weightlessness, are indicated. PMID:11543100

  9. Fracto-emission - The role of charge separation. [in particle emission during fracture

    NASA Technical Reports Server (NTRS)

    Dickinson, J. T.; Jensen, L. C.; Jahan-Latibari, A.

    1984-01-01

    Fracto-emission is the emission of particles (e.g., electrons, ions, ground state and excited neutrals, and photons) during and following fracture. It is found that during fracture in vacuum of adhesive bonds and crystalline materials involving large amounts of charge separation on the surface the emission of charged particles, excited neutrals, light, and radio waves occurs with unique and revealing time dependencies. Simultaneous fracto-emission measurements on several systems are reported. The results are interpreted in terms of a conceptual model involving the following steps: (1) charge separation due to fracture, (2) desorption of gases from the material into the crack tip, (3) a gas discharge in the crack, (4) energetic bombardment of the freshly created crack walls, and (5) thermally stimulated electron emission, accompanied by electron stimulated desorption of ions and excited neutrals. In addition to evidence from fracture experiments, results from studies of electron bombardment of a polymer surface are presented.

  10. Nature of composite fermions and the role of particle-hole symmetry: A microscopic account

    NASA Astrophysics Data System (ADS)

    Balram, Ajit C.; Jain, J. K.

    2016-06-01

    Motivated by the issue of particle-hole symmetry for the composite fermion Fermi sea at the half-filled Landau level, Son has made an intriguing proposal [Phys. Rev. X 5, 031027 (2015), 10.1103/PhysRevX.5.031027] that composite fermions are Dirac particles. We ask what features of the Dirac-composite fermion theory and its various consequences may be reconciled with the well-established microscopic theory of the fractional quantum Hall effect and the 1/2 state, which is based on nonrelativistic composite fermions. Starting from the microscopic theory, we derive the assertion of Son that the particle-hole transformation of electrons at filling factor ν =1/2 corresponds to an effective time-reversal transformation (i.e., {kj} →{-kj} ) for composite fermions, and discuss how this connects to the absence of 2 kF backscattering in the presence of a particle-hole symmetric disorder. By considering bare holes in various composite-fermion Λ levels (analogs of electronic Landau levels), we determine the Λ level spacing and find it to be very nearly independent of the Λ level index, consistent with a parabolic dispersion for the underlying composite fermions. Finally, we address the compatibility of the Chern-Simons theory with the lowest Landau level constraint, and find that the wave functions of the mean-field Chern-Simons theory, as well as a class of topologically similar wave functions, are surprisingly accurate when projected into the lowest Landau level. These considerations lead us to introduce a "normal form" for the unprojected wave functions of the n /(2 p n -1 ) states that correctly capture the topological properties even without lowest Landau level projection.

  11. Ice nucleating particles from biomass combustion: emission rates and the role of refractory black carbon

    NASA Astrophysics Data System (ADS)

    Levin, E. J.; McMeeking, G. R.; McCluskey, C. S.; Carrico, C. M.; Nakao, S.; Stockwell, C.; Yokelson, R. J.; Sullivan, R. C.; DeMott, P. J.; Kreidenweis, S. M.

    2015-12-01

    Ice nucleating particles (INPs) allow initial ice crystal formation in clouds at temperatures warmer than about -36 °C and are thus important for cloud and precipitation development. One potential source of INPs to the atmosphere is biomass combustion, such as wildfires, prescribed burning and agricultural burning, which emits large quantities of particulate matter into the atmosphere and is a major source of black carbon (BC) aerosol. To better understand and constrain INP emissions from biomass combustion, globally relevant fuels were used in a series of burns during a study called FLAME 4 at the USFS Fire Sciences Laboratory in Missoula, MT. Concentrations of immersion mode INPs were measured using a Colorado State University Continuous Flow Diffusion Chamber (CFDC). During the first part of the study, emissions were measured in real time as fires progressed from ignition to flaming and smoldering phases. INP emissions were observed predominately during periods of intensely flaming combustion. Roughly 75% of measured burns produced detectable INP concentrations and these had, on average, higher combustion efficiencies and higher BC emissions. During the second half of FLAME 4, we directly measured the contribution of refractory black carbon (rBC) to INP concentrations by selectively removing these particles via laser-induced incandescence (LII) using a Single Particle Soot Photometer (SP2; Droplet Measurement Technologies). The SP2 uses a 1064 nm Na:YAG laser to heat rBC aerosol to their vaporization temperatures, thus removing them from the sampled aerosol. By passing combustion aerosol through the SP2 with the laser on and off while measuring the remaining aerosol with the CFDC, we were able to determine the contribution of rBC to the INP population. Reductions in INPs of 0 - 70% were observed when removing rBC from the combustion aerosol, indicating the importance of rBC particles to INP concentrations for some burn scenarios.

  12. Role of food and clay particles in toxicity of copper and diazinon using Daphnia magna.

    PubMed

    Jeon, Junho; Sung Ra, Jin; Lee, Sun Hong; Lee, Myun J; Yu, Seung H; Kim, Sang Don

    2010-03-01

    Toxicity changes in copper and diazinon were investigated in the presence of food, clay, and their mixture by using Daphnia magna. In sorption equilibrium experiments, copper was significantly attracted (>34% sorbed) to food, clay, and food-clay mixture due to their negative zeta potential, while diazinon was less sorbed (<11%). In the exposure test with food and clay particles, it was revealed that copper was remarkably reduced in the presence of clay particles indicating the change in bioavailability of copper by sorption to clay. This was considered as the primary mechanism for toxicity reduction whereas diazinon toxicity was food dependent in the analysis of toxicity using toxicity change index (TCI). It was also shown that certain foods could not only act as a sorbent to copper and diazinon, but also as a material of energy source to alleviate the toxic damage. Meanwhile, clay can be considered as a prominent sorbent to copper but not to diazinon and can inhibit the sorption interaction between foodstuffs and toxicants through the aggregation and sedimentation processes. Furthermore, clay particles, as shown in TCI analysis, may be a potentially risky material as a physiological stressor or a toxicant carrier in contaminated environments. PMID:19942290

  13. Role of slip between a probe particle and a gel in microrheology

    NASA Astrophysics Data System (ADS)

    Fu, Henry; Shenoy, Vivek; Powers, Thomas

    2008-11-01

    In the technique of microrheology, rheological information is deduced from the behavior of microscopic probe particles under thermal or active forcing. Microrheology requires knowledge of the force felt by a probe particle in response to displacements, which we investigate for a spherical particle using the two-fluid model. The gel is represented by a polymer network coupled to a surrounding solvent via a drag force. We obtain an analytic solution for the response function in the limit of small volume fraction of the polymer network, and neglecting inertial effects. We use no-slip boundary conditions for the solvent at the surface of the sphere. The boundary condition for the network at the surface of the sphere is a kinetic friction law specifying the tangential stress. We show that the far field motion and the force on the sphere are controlled by the solvent boundary conditions at high frequency and by the network boundary conditions at low frequency. At low frequencies compression of the network can also affect the force on the sphere. We find the crossover frequencies at which the effects of sliding of the sphere past the polymer network and compression of the gel become important.

  14. PARTICLE ACCELERATION AT NEAR-PERPENDICULAR SHOCKS: THE ROLE OF FIELD-LINE TOPOLOGY

    SciTech Connect

    Kota, Jozsef

    2010-11-01

    Particle acceleration at two-dimensional (2D) shocks can significantly differ from our expectations based on one-dimensional shocks. We discuss several features of 2D shocks. First, we present a simple example of diffusive acceleration to demonstrate that (1) 'hot spots' and cold regions can be expected along the shock face, as the field-line configuration changes along the shock face, (2) the flux of accelerated particles (even the average flux) can be expected to increase beyond the shock, and (3) 2D structures may lead to a softening of the spectrum. We also address quasi-perpendicular shocks and discuss what happens when a field line is hit by a curved shock or is detaching from a shock. This mechanism is of interest on both large and small scales. We consider pure field-aligned transport and address both the diffusive (large scale) and scatter-free (small scale) cases, looking from the perspective of one field line. We find that quasi-trapping of particles in front of the shock can lead to rapid and effective acceleration via multiple mirroring on the ever faster moving shock. This mechanism may be of importance at various astrophysical, heliospheric, and coronal mass ejection driven shocks.

  15. Laboratory Studies of the Role of Amines in Particle Formation, Growth and Climate

    SciTech Connect

    Finlayson-Pitts, Barbara J.

    2015-02-07

    Organosulfur compounds have a variety of sources, particularly biological processes in the oceans. Their oxidation in air forms sulfur dioxide, which is further oxidized to sulfuric acid, as well as methanesulfonic acid (MSA). While sulfuric acid is a well known precursor to particles in air, MSA had not been regarded as a source of new particle formation. Laboratory studies were carried out under this project that showed MSA forms new particles quite efficiently in the presence of amines and water vapor. The data could be reproduced with a relatively simple kinetics model representing cluster formation and growth, which is promising for representing this chemistry in global climate models. The initial steps in the kinetics scheme are based on quantum chemical calculations of likely clusters. The organosulfur chemistry was introduced into an atmospheric model for southern California and used to predict the impact of going to a fossil-fuel free world in which anthropogenic emissions of SO2 are removed, but the natural processes remain.

  16. Asymmetric lipid-polymer particles (LIPOMER) by modified nanoprecipitation: role of non-solvent composition.

    PubMed

    Jindal, Anil B; Devarajan, Padma V

    2015-07-15

    Asymmetric lipid polymer nanostructures (LIPOMER) comprising glyceryl monostearate (GMS) as lipid and Gantrez AN 119 (Gantrez) as polymer, revealed enhanced splenic accumulation. In the present paper, we attempt to explain the formation of asymmetric GMS LIPOMER using real time imaging. Particles were prepared by precipitation under static conditions using different non-solvent phase compositions. The process was video recorded and the videos converted to time elapsed images using the FFmpeg 0.10.2 software at 25 frames/sec. Non-solvent compositions comprising >30% of IPA/Acetone revealed significant stranding of the solvent phase and slower onset of precipitation(2-6s). At lower concentrations of IPA and acetone, and in non-solvent compositions comprising ethanol/water the stranding phenomenon was not evident. Further, rapid precipitation(<1 s) was evident. Nanoprecipitation based on the Marangoni effect is a result of diffusion stranding, interfacial turbulence, and mass transfer of solvent and non-solvent resulting in solute precipitation. Enhanced diffusion stranding favored by high interaction of GMS and Gantrez(low ΔPol), and the low solubility parameter(Δδtotal) and high mixing enthalpy(ΔHM) of GMS in IPA resulted in droplets with random shapes analogous to an amoeba with pseudopodia, which on precipitation formed asymmetric particles. Asymmetric particles could be readily designed through appropriate selection of solutes and non-solvent phase by modified nanoprecipitation. PMID:25934429

  17. Heterogeneous reaction of gaseous hydrogen peroxide and its role in the oxidation of organic compounds on mineral dust particles

    NASA Astrophysics Data System (ADS)

    Zhao, Y.; Chen, Z.; Huang, D.

    2012-12-01

    As a significant atmospheric oxidant, hydrogen peroxide (H2O2) plays an important role in the formation of secondary sulfate, HOx radical chemistry, as well as the formation of secondary organic aerosol. Recent field and model combined studies have revealed that heterogeneous reaction on mineral dust seems to be an important sink for gaseous H2O2. However, available kinetic data concerning this reaction are quite scarce and is mainly limited to the reaction on mineral oxide surfaces. In addition, H2O2 may act as a source of surface reactive species (e.g., OH and HO2 radicals) on mineral dust particles, and thus may favor the oxidation of surface co-adsorbed organics. However, little is known about this potential role that H2O2 may play. In this study, we have investigated heterogeneous reactions of gaseous H2O2 with two different authentic mineral dusts, Asian dust storm particles and Tengger Desert sand, using a filter-based flow tube reactor. The BET uptake coefficients of H2O2 were measured to be on the order of 10^-4 for both dust samples. Additionally, the potential role of H2O2 in the oxidation of organic compounds on mineral dust particles were studied by investigating the reactions of methacrolein (MAC) and methyl vinyl ketone (MVK) with alumina oxide, a major reactive components of mineral dust, in the absence and presence of H2O2. We found that in the presence of H2O2, the yield of organic acid products exhibits a marked enhancement relative to that in the absence of H2O2, that is, a factor of 2 for acetic acid and a factor of 3 for formic acid in MAC reaction system, and up to a factor of 10 for acetic acid in MVK reaction system. These data indicate a significant role of H2O2 in oxidation of MAC and MVK, probably related to formation of surface OH and HO2 radicals from H2O2 decomposition on the particles. Our results suggest that uptake by mineral dust can be an important removal process of gaseous H2O2, comparable to the loss due to the photolysis or

  18. Particle size and interfacial effects on heat transfer characteristics of water and {alpha}-SiC nanofluids.

    SciTech Connect

    Timofeeva, E.; Smith, D. S.; Yu, W.; France, D. M.; Singh, D.; Routbort, J. L.

    2010-01-01

    The effect of average particle sizes on basic macroscopic properties and heat transfer performance of {alpha}-SiC/water nanofluids was investigated. The average particle sizes, calculated from the specific surface area of nanoparticles, were varied from 16 to 90 nm. Nanofluids with larger particles of the same material and volume concentration provide higher thermal conductivity and lower viscosity increases than those with smaller particles because of the smaller solid/liquid interfacial area of larger particles. It was also demonstrated that the viscosity of water-based nanofluids can be significantly decreased by pH of the suspension independently from the thermal conductivity. Heat transfer coefficients were measured and compared to the performance of base fluids as well as to nanofluids reported in the literature. Criteria for evaluation of the heat transfer performance of nanofluids are discussed and optimum directions in nanofluid development are suggested.

  19. Voidage and pressure profile characteristics of sand-iron ore-coal-FCC single-particle systems in the riser of a pilot plant circulating fluidized bed

    SciTech Connect

    Das, M.; Meikap, B.C.; Saha, R.K.

    2008-06-15

    Hydrodynamic behaviors of single system of particles were investigated in a circulating fluidized bed (CFB) unit. Particles belonging to Geldart groups A and B like sand of various sizes (90, 300, 417, 522, 599, and 622 mu m), FCC catalyst (120 mu m), iron ore (166 and 140 {mu} m), and coal (335 and 168 {mu} m) were used to study the hydrodynamic characteristics. Superficial air velocity used in the present study ranged between 2.01 and 4.681 m/s and corresponding mass fluxes were 12.5-50 kg/(m{sup 2} s). A CFB needs the creation of some special hydrodynamic conditions, namely a certain combination of superficial gas velocity, solids circulation rate, particle diameter, density of particle, etc. which can give rise to a state wherein the solid particles are subjected to an upward velocity greater than the terminal or free fall velocity of the majority of the individual particles. The hydrodynamics of the bed was investigated in depth and theoretical analysis is presented to support the findings. Based on gas-solid momentum balance in the riser, a distinction between apparent and real voidage has been made. The effects of acceleration and friction on the real voidage have been estimated. Results indicated a 0.995 voidage for higher superficial gas velocity of 4.681. m/s.

  20. Gyrokinetic study of the role of β on electron particle transport in tokamaks

    NASA Astrophysics Data System (ADS)

    Hein, T.; Angioni, C.; Fable, E.; Candy, J.

    2010-10-01

    Electromagnetic effects on the radial transport of electrons in the core of tokamak plasmas are studied by means of linear and nonlinear gyrokinetic simulations with the code GYRO [J. Candy and R. E. Waltz, J. Comput. Phys. 186, 545 (2003)] and by an analytical derivation. The impact of a finite β, that is, a finite ratio of the plasma pressure to the magnetic pressure, is considered on the fluctuations of the magnetic field through Ampére's law, as well as on the geometrical modification of the vertical drift produced by the Shafranov shift in the magnetic equilibrium, which, for realistic descriptions, has to be included in both electrostatic and electromagnetic modeling. The condition of turbulent particle flux at the null, which allows the determination of stationary logarithmic density gradients when neoclassical transport and particle sources are negligible, is investigated for increasing values of β, in regimes of ion temperature gradient and trapped electron mode turbulence. The loss of adiabaticity of passing electrons produced by fluctuations in the magnetic vector potential produces an outward convection. When the magnetic equilibrium geometry is kept fixed, this induces a strong reduction of the stationary logarithmic density gradient with increasing β. This effect is partly compensated by the geometrical effect on the vertical drift. This compensation effect, however, is significantly weaker in nonlinear simulations as compared to quasilinear calculations. A detailed comparison between quasilinear and nonlinear results reveals that the predicted value of the logarithmic density gradient is highly sensitive on the assumptions on the wave number spectrum applied in the quasilinear model. The qualitative consistency of the theoretical predictions with the experimental results obtained so far on the dependence of density peaking on β is discussed by considering the additional impact, with increasing β, of a particle source delivered by neutral beam

  1. Gyrokinetic study of the role of {beta} on electron particle transport in tokamaks

    SciTech Connect

    Hein, T.; Angioni, C.; Fable, E.; Candy, J.

    2010-10-15

    Electromagnetic effects on the radial transport of electrons in the core of tokamak plasmas are studied by means of linear and nonlinear gyrokinetic simulations with the code GYRO[J. Candy and R. E. Waltz, J. Comput. Phys. 186, 545 (2003)] and by an analytical derivation. The impact of a finite {beta}, that is, a finite ratio of the plasma pressure to the magnetic pressure, is considered on the fluctuations of the magnetic field through Ampere's law, as well as on the geometrical modification of the vertical drift produced by the Shafranov shift in the magnetic equilibrium, which, for realistic descriptions, has to be included in both electrostatic and electromagnetic modeling. The condition of turbulent particle flux at the null, which allows the determination of stationary logarithmic density gradients when neoclassical transport and particle sources are negligible, is investigated for increasing values of {beta}, in regimes of ion temperature gradient and trapped electron mode turbulence. The loss of adiabaticity of passing electrons produced by fluctuations in the magnetic vector potential produces an outward convection. When the magnetic equilibrium geometry is kept fixed, this induces a strong reduction of the stationary logarithmic density gradient with increasing {beta}. This effect is partly compensated by the geometrical effect on the vertical drift. This compensation effect, however, is significantly weaker in nonlinear simulations as compared to quasilinear calculations. A detailed comparison between quasilinear and nonlinear results reveals that the predicted value of the logarithmic density gradient is highly sensitive on the assumptions on the wave number spectrum applied in the quasilinear model. The qualitative consistency of the theoretical predictions with the experimental results obtained so far on the dependence of density peaking on {beta} is discussed by considering the additional impact, with increasing {beta}, of a particle source delivered

  2. Do interacting coronal mass ejections play a role in solar energetic particle events?

    SciTech Connect

    Kahler, S. W.; Vourlidas, A.

    2014-03-20

    Gradual solar energetic (E > 10 MeV) particle (SEP) events are produced in shocks driven by fast and wide coronal mass ejections (CMEs). With a set of western hemisphere 20 MeV SEP events, we test the possibility that SEP peak intensities, Ip, are enhanced by interactions of their associated CMEs with preceding CMEs (preCMEs) launched during the previous 12 hr. Among SEP events with no, 1, or 2 or more (2+) preCMEs, we find enhanced Ip for the groups with preCMEs, but no differences in TO+TR, the time from CME launch to SEP onset and the time from onset to SEP half-peak Ip. Neither the timings of the preCMEs relative to their associated CMEs nor the preCME widths W {sub pre}, speeds V {sub pre}, or numbers correlate with the SEP Ip values. The 20 MeV Ip of all the preCME groups correlate with the 2 MeV proton background intensities, consistent with a general correlation with possible seed particle populations. Furthermore, the fraction of CMEs with preCMEs also increases with the 2 MeV proton background intensities. This implies that the higher SEP Ip values with preCMEs may not be due primarily to CME interactions, such as the 'twin-CME' scenario, but are explained by a general increase of both background seed particles and more frequent CMEs during times of higher solar activity. This explanation is not supported by our analysis of 2 MeV proton backgrounds in two earlier preCME studies of SEP events, so the relevance of CME interactions for larger SEP event intensities remains unclear.

  3. Crucial Role for Outdoor Chemistry in Ultrafine Particle Formation in Modern Office Buildings.

    PubMed

    Carslaw, Nicola; Ashmore, Mike; Terry, Andrew C; Carslaw, David C

    2015-09-15

    In the developed world, we spend most of our time indoors, where we receive the majority of our exposure to air pollution. This paper reports model simulations of PM2.5 and ozone concentrations in identical landscape offices in three European cities: Athens, Helsinki, and Milan. We compare concentrations during an intense heatwave in August 2003 with a meteorologically more typical August in 2009. During the heatwave, average indoor ozone concentrations during office hours were 44, 19, and 41 ppb in Athens, Helsinki, and Milan respectively, enhanced by 7, 4, and 17 ppb respectively relative to 2009. Total predicted PM2.5 concentrations were 13.5, 3.6, and 17.2 μg m(-3) in Athens, Helsinki, and Milan respectively, enhanced by 0.5, 0.4, and 6.7 μg m(-3) respectively relative to 2009: the three cities were affected to differing extents by the heatwave. A significant portion of the indoor PM2.5 derived from gas-phase chemistry outdoors, producing 2.5, 0.8, and 4.8 μg m(-3) of the total concentrations in Athens, Helsinki, and Milan, respectively. Despite filtering office inlet supplies to remove outdoor particles, gas-phase precursors for particles can still enter offices, where conditions are ripe for new particles to form, particularly where biogenic emissions are important outdoors. This result has important implications for indoor air quality, particularly given the current trend for green walls on buildings, which will provide a potential source of biogenic emissions near to air inlet systems. PMID:26301707

  4. The role of biogenic, biomass burning and urban pollution aerosol particles in controlling key atmospheric processes in Amazonia

    NASA Astrophysics Data System (ADS)

    Artaxo, P.; Ferreira De Brito, J.; Barbosa, H. M.; Rizzo, L. V.; Sena, E. T.; Cirino, G.; Arana, A.; Yanez-Serrano, A. M.

    2013-05-01

    As part of the LBA (The Large Scale Biosphere Atmosphere Experiment in Amazonia) experiment, a research program run in the last 10 years had help to understand critical atmospheric processes in Amazonia. The vegetation in Amazonia is a direct source of aerosol particles to the atmosphere as well as a source of biogenic trace gases that generates particles trough gas-to-particle conversion. Biomass burning is also a large source of particles and trace gases to the atmosphere. Over the last 10 years, the LBA experiment has unveiled several key processes that control Amazonian composition and influence regional climate. A significant fraction (60-80%) of airborne particles can act as Cloud Condensation Nuclei (CCN), influencing cloud formation and development. The radiation balance is strongly influenced by biomass burning particles, and surface radiative forcing up to -250 w/m2 is measured. A network of 8 sites with AERONET sunphotometers measures aerosol optical depth (AOD) and derive aerosol size distribution and optical properties. Aerosols are composed of more than 70% of organic material, with significant absorption characteristics. The aerosol radiative forcing during the biomass burning season can reach very high values, and the increase in diffuse radiation increases the carbon uptake by the forest for AOD values smaller than 1.2 at 500nm. For large AOD, the solar flux is strongly reduced making the carbon uptake approach zero for AOD larger than 3.0. The composition of aerosols is mostly organic, with contribution of K, Ca, Si, and other trace elements. The aerosol has high capability to serve as Cloud Condensation Nuclei (CCN), contributing with high water vapor amounts to the significant cloud cover over the region. In the last 20 years, an urbanization process took over for most of the Amazonian region, increasing urban pollution that interacts with forest emissions to produce a quite unique pattern of aerosols and pollutants around large urban areas such

  5. The Role of Teacher Characteristics and Personality in Student Learning in Individualized Science Programs.

    ERIC Educational Resources Information Center

    Horton, Phillip B.

    Seventeen selected research studies relating student learning with teacher characteristics and personality in grades 7-12 science classrooms are reviewed. Methodology, objectives, and major findings of the 1960 "Teacher Characteristics Study" and short summaries of nine additional studies are considered in the first section dealing with general…

  6. Reading and Spelling Skills in German Third Graders: Examining the Role of Student and Context Characteristics

    ERIC Educational Resources Information Center

    Suchodoletz, Antje; Larsen, Ross A. A.; Gunzenhauser, Catherine; Fäsche, Anika

    2015-01-01

    Background: Educational processes and outcomes are influenced by a multitude of factors, including individual and contextual characteristics. Recently, studies have demonstrated that student and context characteristics may produce unique and cumulative effects on educational outcomes. Aims: The study aimed to investigate (1) the relative…

  7. Role of Teacher Characteristics and School Resources in Early Mathematics Learning

    ERIC Educational Resources Information Center

    Jung, Eunjoo; Brown, Elizabeth T.; Karp, Karen S.

    2014-01-01

    The authors investigated the degree to which school-level teacher characteristics and resources are related to the mathematics learning of kindergarten children using a sample drawn from a large US database. Kindergarten-level teacher characteristics were operationalised as collective teacher efficacy, teacher experience and teacher preparation;…

  8. Decomposing Inequalities in Performance Scores: The Role of Student Background, Peer Effects and School Characteristics

    ERIC Educational Resources Information Center

    Mostafa, Tarek

    2010-01-01

    This paper analyses the mechanisms of stratification and inequalities in educational achievements. The main objective is to determine how stratification leads to unequal educational outcomes and how inequalities are channelled through student characteristics, school characteristics and peer effects. This analysis is undertaken in five countries…

  9. The Relationship between Neighborhood Characteristics and Effective Parenting Behaviors: The Role of Social Support

    ERIC Educational Resources Information Center

    Byrnes, Hilary F.; Miller, Brenda A.

    2012-01-01

    Neighborhood characteristics have been linked to healthy behavior, including effective parenting behaviors. This may be partially explained through the neighborhood's relation to parents' access to social support from friends and family. The current study examined associations of neighborhood characteristics with parenting behaviors indirectly…

  10. Surface reaction characteristics at low temperature synthesis BaTiO 3 particles by barium hydroxide aqueous solution and titanium tetraisopropoxide

    NASA Astrophysics Data System (ADS)

    Zeng, Min

    2011-05-01

    Well-crystallized cubic phase BaTiO 3 particles were prepared by heating the mixture of barium hydroxide aqueous solution and titania derived from the hydrolysis of titanium isopropoxide (TTIP) at 328 K, 348 K or 368 K for 24 h. The morphology and size of obtained particles depended on the reaction temperature and the Ba(OH) 2/TTIP molar ratio. By the direct hydrolytic reaction of titanium tetraisopropoxide, the high surface area titania (TiO 2) was obtained. The surface adsorption characteristics of the titania particles had been studied with different electric charges OH - ions or H + ions. The formation mechanism and kinetics of BaTiO 3 were examined by measuring the concentration of [Ba 2+] ions in the solution during the heating process. The experimental results showed that the heterogeneous nucleation of BaTiO 3 occurred on the titania surface, according to the Avrami's equation.

  11. Two metallothionein genes in Oxya chinensis: molecular characteristics, expression patterns and roles in heavy metal stress.

    PubMed

    Liu, Yaoming; Wu, Haihua; Kou, Lihua; Liu, Xiaojian; Zhang, Jianzhen; Guo, Yaping; Ma, Enbo

    2014-01-01

    Metallothioneins (MTs) are small, cysteine-rich, heavy metal-binding proteins involved in metal homeostasis and detoxification in living organisms. In the present study, we cloned two MT genes (OcMT1 and OcMT2) from Oxya chinensis, analyzed the expression patterns of the OcMT transcripts in different tissues and at varying developmental stages using real-time quantitative PCR (RT-qPCR), evaluated the functions of these two MTs using RNAi and recombinant proteins in an E. coli expression system. The full-length cDNAs of OcMT1 and OcMT2 encoded 40 and 64 amino acid residues, respectively. We found Cys-Cys, Cys-X-Cys and Cys-X-Y-Z-Cys motifs in OcMT1 and OcMT2. These motifs might serve as primary chelating sites, as in other organisms. These characteristics suggest that OcMT1 and OcMT2 may be involved in heavy metal detoxification by capturing the metals. Two OcMT were expressed at all developmental stages, and the highest levels were found in the eggs. Both transcripts were expressed in all eleven tissues examined, with the highest levels observed in the brain and optic lobes, followed by the fat body. The expression of OcMT2 was also relatively high in the ovaries. The functions of OcMT1 and OcMT2 were explored using RNA interference (RNAi) and different concentrations and treatment times for the three heavy metals. Our results indicated that mortality increased significantly from 8.5% to 16.7%, and this increase was both time- and dose-dependent. To evaluate the abilities of these two MT proteins to confer heavy metal tolerance to E. coli, the bacterial cells were transformed with pET-28a plasmids containing the OcMT genes. The optical densities of both the MT-expressing and control cells decreased with increasing concentrations of CdCl2. Nevertheless, the survival rates of the MT-overexpressing cells were higher than those of the controls. Our results suggest that these two genes play important roles in heavy metal detoxification in O. chinensis. PMID:25391131

  12. Two Metallothionein Genes in Oxya chinensis: Molecular Characteristics, Expression Patterns and Roles in Heavy Metal Stress

    PubMed Central

    Liu, Yaoming; Wu, Haihua; Kou, Lihua; Liu, Xiaojian; Zhang, Jianzhen; Guo, Yaping; Ma, Enbo

    2014-01-01

    Metallothioneins (MTs) are small, cysteine-rich, heavy metal-binding proteins involved in metal homeostasis and detoxification in living organisms. In the present study, we cloned two MT genes (OcMT1 and OcMT2) from Oxya chinensis, analyzed the expression patterns of the OcMT transcripts in different tissues and at varying developmental stages using real-time quantitative PCR (RT-qPCR), evaluated the functions of these two MTs using RNAi and recombinant proteins in an E. coli expression system. The full-length cDNAs of OcMT1 and OcMT2 encoded 40 and 64 amino acid residues, respectively. We found Cys-Cys, Cys-X-Cys and Cys-X-Y-Z-Cys motifs in OcMT1 and OcMT2. These motifs might serve as primary chelating sites, as in other organisms. These characteristics suggest that OcMT1 and OcMT2 may be involved in heavy metal detoxification by capturing the metals. Two OcMT were expressed at all developmental stages, and the highest levels were found in the eggs. Both transcripts were expressed in all eleven tissues examined, with the highest levels observed in the brain and optic lobes, followed by the fat body. The expression of OcMT2 was also relatively high in the ovaries. The functions of OcMT1 and OcMT2 were explored using RNA interference (RNAi) and different concentrations and treatment times for the three heavy metals. Our results indicated that mortality increased significantly from 8.5% to 16.7%, and this increase was both time- and dose-dependent. To evaluate the abilities of these two MT proteins to confer heavy metal tolerance to E. coli, the bacterial cells were transformed with pET-28a plasmids containing the OcMT genes. The optical densities of both the MT-expressing and control cells decreased with increasing concentrations of CdCl2. Nevertheless, the survival rates of the MT-overexpressing cells were higher than those of the controls. Our results suggest that these two genes play important roles in heavy metal detoxification in O. chinensis. PMID:25391131

  13. Characteristics of regional new particle formation in urban and regional background environments in the North China Plain

    NASA Astrophysics Data System (ADS)

    Wang, Z. B.; Hu, M.; Sun, J. Y.; Wu, Z. J.; Yue, D. L.; Shen, X. J.; Zhang, Y. M.; Pei, X. Y.; Wiedensohler, A.

    2013-08-01

    Long-term measurements of particle number size distributions were carried out in the North China Plain both at an urban background site (Peking University, PKU) and a regional Global Atmospheric Watch station (Shangdianzi, SDZ) from March to November in 2008. In total, 52 new particle formation events were observed simultaneously at both sites, indicating that this is a regional phenomenon in the North China Plain. On average, the mean condensation sink value before the nucleation event start was 0.025 s-1 in the urban environment, which was 1.6 times higher than that at regional site. However, higher particle formation and growth rates were observed at PKU (10.8 cm-3 s-1 an 5.2 nm h-1) compared with those at SDZ (4.9 cm-3 s-1 and 4.0 nm h-1). These results implied that more precursors are needed to participate in the nucleation process to observe the occurrence of new particle formation event in a more polluted urban environment. Different from the observations in clean environments, the background condition of the observed nucleation events in the North China Plain could be characterized as the co-existing of the higher source and sink. The condensational growth of newly formed particles results in an increase in the particle mass concentration, particle light scattering coefficient, and CCN number concentration, with consequences on climate effects and air quality. In 34 investigated new particle formation cases at both sites, a significant particle nucleation and subsequent growth over a sufficient long time period were observed and investigated in terms of the particle light scattering and the number concentration of "potential" CCN. The results revealed that the new particle formation increases the particle light scattering coefficient and CCN number concentration in the North China Plain by factors in the range of 6.3-7.6 and 5.6-8.7, respectively. Moreover, the potential contribution of anthropogenic emissions to the CCN number concentration is more than 50

  14. Socio-economic gradients in psychological distress: a focus on women, social roles and work-home characteristics.

    PubMed

    Matthews, Sharon; Power, Chris

    2002-03-01

    A focus in the literature on determinants of women's health is the cost and benefit of occupying multiple roles as employee, spouse, and mother, yet little attention has been given to the work and home characteristics of different roles for women in paid and unpaid work. The impact of work-home factors on socio-economic gradients in health has also tended to be overlooked. This paper assesses the contribution of work-home factors on socio-economic differences in psychological distress among women, using data from the 1958 British birth cohort. Outcome measures include psychological distress and social class at age 33. Work-home measures include: (1) roles--employment, marital status, domestic responsibility and parental status (2) work characteristics--psychosocial job strain, insecurity, unsocial working hours, and (3) home characteristics youngest child's age, total number of children, childcare responsibilities and having an older adult in the household (over 70 years). A social gradient in psychological distress exists: the odds ratio (OR) for classes IV and V versus. I and II was 3.02, adjusting for prior psychological distress reduces this to 2.36. Whilst, work and home factors were associated separately with distress and social class, the combined effect of work and home factors did not account for the class gradient in distress. This surprising result therefore implicates factors beyond adult social roles examined here in the development of socio-economic gradients. PMID:11999494

  15. Investigating the role of vibrational excitation in simulating charged-particle tracks in liquid pyrimidine

    NASA Astrophysics Data System (ADS)

    Brunger, Michael J.; Ratnavelu, Kuru; Buckman, Stephen J.; Jones, Darryl B.; Muñoz, Antonio; Blanco, Francisco; García, Gustavo

    2016-03-01

    We report on our results of a study into the sensitivity of charged-particle (electron) track simulations in liquid pyrimidine, to the vibrational cross sections and vibrational energy loss distribution function employed in those simulations. We achieve this by repeating the earlier investigation of Fuss et al. [J. Appl. Phys. 117, 214701 (2015)], but now incorporating more accurate data for the vibrational integral cross sections and the energy loss distribution function that have recently become available. We find that while changes in absorbed dose or particle range are quite minor, due to the energy transferred via vibrational excitations being low in comparison to that for other processes such as ionisation, at the very end of the tracks, where non-ionizing interactions dominate, the significantly large numbers of vibrational excitation processes increases the electrons' ability to induce other effects (e.g. sample heating, bond breaking and radical formation) that might cause damage. Contribution to the Topical Issue "Advances in Positron and Electron Scattering", edited by Paulo Limao-Vieira, Gustavo Garcia, E. Krishnakumar, James Sullivan, Hajime Tanuma and Zoran Petrovic.

  16. Understanding the Role of Water in Modifying Particle Mixing States for CCN Activity

    NASA Astrophysics Data System (ADS)

    Vu, D. N.; Gao, S.; Pierce, J. R.; Asa-Awuku, A. A.

    2014-12-01

    CCN data sets from ambient and chamber studies, which consist of complex heterogeneous mixtures of organic and inorganic aerosol mixtures, may not show a single activation curve but instead can exhibit multiple activations not associated with doubly charged particles. It has been suggested that these activation curves may be representative of multiple externally mixed compounds, whereas single activation curves are representative of single component or multicomponent internally mixed aerosols. To characterize and modify mixing states, a new laminar flow tube apparatus was developed to control the extent of mixing of organic and inorganic fractions under different environmental conditions such as relative humidity. Data sets yielding multiple activation curves have been recreated by mixing multiple inorganic and organic compounds. Preliminary results suggest that aerosol water is a significant factor; under dry conditions, the aerosols remained externally mixed while humid conditions facilitated internal mixing. For example, ammonium sulfate (inorganic) and succinic acid (organic) when dry, maintained an external mixture and multiple activation curves were observed to be constant. Under humid conditions, external mixing was initially observed; however, the aerosol water promoted internal mixing and the activation curves were observed to converge into a single curve. The data agrees well with Köhler Theory and single parameter (kappa) theory thermodynamic predictions of droplet activation. Data sets are also compared with a diffusion based coagulation particle model to predict mixing behavior. The method of analysis and the effect of mixing states of multiple components on the supersaturated hygroscopic properties of aerosols are presented.

  17. The role of particle-to-cell interactions in dictating nanoparticle aided magnetophoretic separation of microalgal cells.

    PubMed

    Toh, Pey Yi; Ng, Bee Wah; Ahmad, Abdul Latif; Chieh, Derek Chan Juinn; Lim, JitKang

    2014-11-01

    Successful application of a magnetophoretic separation technique for harvesting biological cells often relies on the need to tag the cells with magnetic nanoparticles. This study investigates the underlying principle behind the attachment of iron oxide nanoparticles (IONPs) onto microalgal cells, Chlorella sp. and Nannochloropsis sp., in both freshwater and seawater, by taking into account the contributions of various colloidal forces involved. The complex interplay between van der Waals (vdW), electrostatic (ES) and Lewis acid-base interactions (AB) in dictating IONP attachment was studied under the framework of extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) analysis. Our results showed that ES interaction plays an important role in determining the net interaction between the Chlorella sp. cells and IONPs in freshwater, while the AB and vdW interactions play a more dominant role in dictating the net particle-to-cell interaction in high ionic strength media (≥100 mM NaCl), such as seawater. XDLVO predicted effective attachment between cells and surface functionalized IONPs (SF-IONPs) with an estimated secondary minimum of -3.12 kT in freshwater. This prediction is in accordance with the experimental observation in which 98.89% of cells can be magnetophoretically separated from freshwater with SF-IONPs. We have observed successful magnetophoretic separation of microalgal cells from freshwater and/or seawater for all the cases as long as XDLVO analysis predicts particle attachment. For both the conditions, no pH adjustment is required for particle-to-cell attachment. PMID:25227473

  18. The role of porous nanostructure in controlling lipase-mediated digestion of lipid loaded into silica particles.

    PubMed

    Joyce, Paul; Tan, Angel; Whitby, Catherine P; Prestidge, Clive A

    2014-03-18

    The rate and extent of lipolysis, the breakdown of fat into molecules that can be absorbed into the bloodstream, depend on the interfacial composition and structure of lipid (fat) particles. A novel method for controlling the interfacial properties is to load the lipid into porous colloidal particles. We report on the role of pore nanostructure and surface coverage in controlling the digestion kinetics of medium-chain and long-chain triglycerides loaded into porous silica powders of different particle size, porosity, and hydrophobicity/hydrophilicity. An in vitro lipolysis model was used to measure digestion kinetics of lipid by pancreatic lipase, a digestive enzyme. The rate and extent of lipid digestion were significantly enhanced when a partial monolayer of lipid was loaded in porous hydrophilic silica particles compared to a submicrometer lipid-in-water emulsion or a coarse emulsion. The inhibitory effect of digestion products was clearly evident for digestion from a submicrometer emulsion and coarse emulsion. This effect was minimal, however, in the two silica-lipid systems. Lipase action was inhibited for lipid loaded in the hydrophobic silica and considered due to the orientation of lipase adsorption on the methylated silica surface. Thus, hydrophilic silica promotes enhanced digestion kinetics, whereas hydrophobic silica exerts an inhibitory effect on hydrolysis. Evaluation of digestion kinetics enabled the mechanism for enhanced rate of lipolysis in silica-lipid systems to be derived and detailed. These investigations provide valuable insights for the optimization of smart food microparticles and lipid-based drug delivery systems based on lipid excipients and porous nanoparticles. PMID:24552363

  19. The role of particle size of particulate nano-zinc oxide wood preservatives on termite mortality and leach resistance

    PubMed Central

    2011-01-01

    Historically most residential wood preservatives were aqueous soluble metal formulations, but recently metals ground to submicron size and dispersed in water to give particulate formulations have gained importance. In this study, the specific role nano-zinc oxide (ZnO) particle size and leach resistance plays in termite mortality resulting from exposure to particulate ZnO-treated wood was investigated. Southern yellow pine (SYP) sapwood impregnated with three concentrations of two particle sizes (30 and 70 nm) of ZnO were compared to wood treated with soluble zinc sulphate (ZnSO4) preservative for leach resistance and termite resistance. Less than four percent leached from the particulate nano-ZnO-treated specimens, while 13 to 25% of the zinc sulphate leached from the soluble treated wood. Nano-ZnO was essentially non-leachable from wood treated with 5% formulation for the 30-nm particle size. In a no-choice laboratory test, eastern subterranean termites (Reticulitermes flavipes) consumed less than 10% of the leached nano-ZnO-treated wood with 93 to 100% mortality in all treatment concentrations. In contrast, termites consumed 10 to 12% of the leached ZnSO4-treated wood, but with lower mortality: 29% in the 1% treatment group and less than 10% (5 and 8%, respectively) in the group of wood blocks treated with 2.5 and 5.0% ZnSO4. We conclude that termites were repelled from consuming wood treated with nano-ZnO, but when consumed it was more toxic to eastern subterranean termites than wood treated with the soluble metal oxide formulation. There were no differences in leaching or termite mortality between the two particle sizes of nano-ZnO. PMID:21711491

  20. The role of particle size of particulate nano-zinc oxide wood preservatives on termite mortality and leach resistance.

    PubMed

    Clausen, Carol A; Kartal, S Nami; Arango, Rachel A; Green, Frederick

    2011-01-01

    Historically most residential wood preservatives were aqueous soluble metal formulations, but recently metals ground to submicron size and dispersed in water to give particulate formulations have gained importance. In this study, the specific role nano-zinc oxide (ZnO) particle size and leach resistance plays in termite mortality resulting from exposure to particulate ZnO-treated wood was investigated. Southern yellow pine (SYP) sapwood impregnated with three concentrations of two particle sizes (30 and 70 nm) of ZnO were compared to wood treated with soluble zinc sulphate (ZnSO4) preservative for leach resistance and termite resistance. Less than four percent leached from the particulate nano-ZnO-treated specimens, while 13 to 25% of the zinc sulphate leached from the soluble treated wood. Nano-ZnO was essentially non-leachable from wood treated with 5% formulation for the 30-nm particle size. In a no-choice laboratory test, eastern subterranean termites (Reticulitermes flavipes) consumed less than 10% of the leached nano-ZnO-treated wood with 93 to 100% mortality in all treatment concentrations. In contrast, termites consumed 10 to 12% of the leached ZnSO4-treated wood, but with lower mortality: 29% in the 1% treatment group and less than 10% (5 and 8%, respectively) in the group of wood blocks treated with 2.5 and 5.0% ZnSO4. We conclude that termites were repelled from consuming wood treated with nano-ZnO, but when consumed it was more toxic to eastern subterranean termites than wood treated with the soluble metal oxide formulation. There were no differences in leaching or termite mortality between the two particle sizes of nano-ZnO. PMID:21711491

  1. The role of particle size of particulate nano-zinc oxide wood preservatives on termite mortality and leach resistance

    NASA Astrophysics Data System (ADS)

    Clausen, Carol A.; Kartal, S. Nami; Arango, Rachel A.; Green, Frederick

    2011-06-01

    Historically most residential wood preservatives were aqueous soluble metal formulations, but recently metals ground to submicron size and dispersed in water to give particulate formulations have gained importance. In this study, the specific role nano-zinc oxide (ZnO) particle size and leach resistance plays in termite mortality resulting from exposure to particulate ZnO-treated wood was investigated. Southern yellow pine (SYP) sapwood impregnated with three concentrations of two particle sizes (30 and 70 nm) of ZnO were compared to wood treated with soluble zinc sulphate (ZnSO4) preservative for leach resistance and termite resistance. Less than four percent leached from the particulate nano-ZnO-treated specimens, while 13 to 25% of the zinc sulphate leached from the soluble treated wood. Nano-ZnO was essentially non-leachable from wood treated with 5% formulation for the 30-nm particle size. In a no-choice laboratory test, eastern subterranean termites ( Reticulitermes flavipes) consumed less than 10% of the leached nano-ZnO-treated wood with 93 to 100% mortality in all treatment concentrations. In contrast, termites consumed 10 to 12% of the leached ZnSO4-treated wood, but with lower mortality: 29% in the 1% treatment group and less than 10% (5 and 8%, respectively) in the group of wood blocks treated with 2.5 and 5.0% ZnSO4. We conclude that termites were repelled from consuming wood treated with nano-ZnO, but when consumed it was more toxic to eastern subterranean termites than wood treated with the soluble metal oxide formulation. There were no differences in leaching or termite mortality between the two particle sizes of nano-ZnO.

  2. Role of slip between a probe particle and a gel in microrheology

    NASA Astrophysics Data System (ADS)

    Fu, Henry C.; Shenoy, Vivek B.; Powers, Thomas R.

    2008-12-01

    In the technique of microrheology, macroscopic rheological parameters as well as information about local structure are deduced from the behavior of microscopic probe particles under thermal or active forcing. Microrheology requires knowledge of the relation between macroscopic parameters and the force felt by a particle in response to displacements. We investigate this response function for a spherical particle using the two-fluid model, in which the gel is represented by a polymer network coupled to a surrounding solvent via a drag force. We obtain an analytic solution for the response function in the limit of small volume fraction of the polymer network, and neglecting inertial effects. We use no-slip boundary conditions for the solvent at the surface of the sphere. The boundary condition for the network at the surface of the sphere is a kinetic friction law, for which the tangential stress of the network is proportional to relative velocity of the network and the sphere. This boundary condition encompasses both no-slip and frictionless boundary conditions as limits. Far from the sphere there is no relative motion between the solvent and network due to the coupling between them. However, the different boundary conditions on the solvent and network tend to produce different far-field motions. We show that the far-field motion and the force on the sphere are controlled by the solvent boundary conditions at high frequency and by the network boundary conditions at low frequency. At low frequencies compression of the network can also affect the force on the sphere. We find the crossover frequencies at which the effects of sliding of the sphere past the polymer network and compression of the gel become important. The effects of sliding alone can lead to an underestimation of moduli by up to 33%, while the effects of compression alone can lead to an underestimation of moduli by up to 20%, and the effects of sliding and compression combined can lead to an underestimation

  3. Experimental studies on particle emissions from cruising ship, their characteristic properties, transformation and atmospheric lifetime in the marine boundary layer

    NASA Astrophysics Data System (ADS)

    Petzold, A.; Hasselbach, J.; Lauer, P.; Baumann, R.; Franke, K.; Gurk, C.; Schlager, H.; Weingartner, E.

    2007-10-01

    Particle emissions from ship engines and their atmospheric transformation in the marine boundary layer (MBL) were investigated in engine test bed studies and in airborne measurements of expanding ship plumes. During the test rig studies, detailed aerosol microphysical and chemical properties were measured in the exhaust gas of a serial MAN B&W seven-cylinder four-stroke marine diesel engine under various load conditions. The emission studies were complemented by airborne aerosol transformation studies in the plume of a large container ship in the English Channel using the DLR aircraft Falcon 20 E-5. Observations from emission studies and plume studies combined with a Gaussian plume dispersion model yield a consistent picture of particle transformation processes from emission to atmospheric processing during plume expansion. Particulate matter emission indices obtained from plume measurements are 8.8±1.0×1015(kg fuel)-1 by number for non-volatile particles and 174±43 mg (kg fuel)-1 by mass for Black Carbon (BC). Values determined for test rig conditions between 85 and 110% engine load are of similar magnitude. For the total particle number including volatile compounds no emission index can be derived since the volatile aerosol fraction is subject to rapid transformation processes in the plume. Ship exhaust particles occur in the size range Dp<0.3 μm, showing a bi-modal structure. The combustion particle mode is centred at modal diameters of 0.05 μm for raw emissions to 0.10 μm at a plume age of 1 h. The smaller-sized volatile particle mode is centred at Dp≤0.02 μm. From the decay of ship exhaust particle number concentrations in an expanding plume, a maximum plume life time of approx. 24 h is estimated for a well-mixed marine boundary layer.

  4. Experimental studies on particle emissions from cruising ship, their characteristic properties, transformation and atmospheric lifetime in the marine boundary layer

    NASA Astrophysics Data System (ADS)

    Petzold, A.; Hasselbach, J.; Lauer, P.; Baumann, R.; Franke, K.; Gurk, C.; Schlager, H.; Weingartner, E.

    2008-05-01

    Particle emissions from ship engines and their atmospheric transformation in the marine boundary layer (MBL) were investigated in engine test bed studies and in airborne measurements of expanding ship plumes. During the test rig studies, detailed aerosol microphysical and chemical properties were measured in the exhaust gas of a serial MAN B&W seven-cylinder four-stroke marine diesel engine under various load conditions. The emission studies were complemented by airborne aerosol transformation studies in the plume of a large container ship in the English Channel using the DLR aircraft Falcon 20 E-5. Observations from emission studies and plume studies combined with a Gaussian plume dispersion model yield a consistent picture of particle transformation processes from emission to atmospheric processing during plume expansion. Particulate matter emission indices obtained from plume measurements are 8.8±1.0×1015(kg fuel)-1 by number for non-volatile particles and 174±43 mg (kg fuel)-1 by mass for Black Carbon (BC). Values determined for test rig conditions between 85 and 110% engine load are of similar magnitude. For the total particle number including volatile compounds no emission index can be derived since the volatile aerosol fraction is subject to rapid transformation processes in the plume. Ship exhaust particles occur in the size range Dp<0.3 μm, showing a bi-modal structure. The combustion particle mode is centred at modal diameters of 0.05 μm for raw emissions to 0.10 μm at a plume age of 1 h. The smaller-sized volatile particle mode is centred at Dp≤0.02 μm. From the decay of ship exhaust particle number concentrations in an expanding plume, a maximum plume life time of approx. 24 h is estimated for a well-mixed marine boundary layer.

  5. The mediating role of job involvement in the relationship between job characteristics and organizational citizenship behavior.

    PubMed

    Chen, Chien-Cheng; Chiu, Su-Fen

    2009-08-01

    Past researchers have found that motivating job characteristics can increase employee display of organizational citizenship behavior (OCB). In this study, the authors extended previous research by investigating the mediating process of job involvement in the relationship between job characteristics and OCB. The authors collected data from 323 employees and their supervisors from 7 companies in Taiwan. Results show that, through the mediating process of job involvement, the 3 job characteristics (i.e., task identity, task significance, and autonomy) positively influenced the display of an employee's OCB, whereas skill variety had a negative effect on OCB. The authors discuss implications of their findings, contributions, limitations, and future research directions. PMID:19702106

  6. Direct and indirect effects of sea spray geoengineering and the role of injected particle size

    NASA Astrophysics Data System (ADS)

    Partanen, Antti-Ilari; Kokkola, Harri; Romakkaniemi, Sami; Kerminen, Veli-Matti; Lehtinen, Kari E. J.; Bergman, Tommi; Arola, Antti; Korhonen, Hannele

    2012-01-01

    Climate-aerosol model ECHAM5.5-HAM2 was used to investigate how geoengineering with artificial sea salt emissions would affect marine clouds and the Earth's radiative balance. Prognostic cloud droplet number concentration and interaction of aerosol particles with clouds and radiation were calculated explicitly, thus making this the first time that aerosol direct effects of sea spray geoengineering are considered. When a wind speed dependent baseline geoengineering flux was applied over all oceans (total annual emissions 443.9 Tg), we predicted a radiative flux perturbation (RFP) of -5.1 W m-2, which is enough to counteract warming from doubled CO2 concentration. When the baseline flux was limited to three persistent stratocumulus regions (3.3% of Earth's surface, total annual emissions 20.6 Tg), the RFP was -0.8 Wm-2 resulting mainly from a 74-80% increase in cloud droplet number concentration and a 2.5-4.4 percentage point increase in cloud cover. Multiplying the baseline mass flux by 5 or reducing the injected particle size from 250 to 100 nm had comparable effects on the geoengineering efficiency with RFPs -2.2 and -2.1 Wm-2, respectively. Within regions characterized with persistent stratocumulus decks, practically all of the radiative effect originated from aerosol indirect effects. However, when all oceanic regions were seeded, the direct effect with the baseline flux was globally about 29% of the total radiative effect. Together with previous studies, our results indicate that there are still large uncertainties associated with the sea spray geoengineering efficiency due to variations in e.g., background aerosol concentration, updraft velocity, cloud altitude and onset of precipitation.

  7. Possible role for secondary particles in proton-induced single event upsets of modern devices

    SciTech Connect

    Savage, M.W.; McNulty, P.J.; Roth, D.R.; Foster, C.C.

    1998-12-01

    Increases in the SEU sensitivity of some modern COTS devices suggest that other reactions besides the direct spallation reaction may begin to play a role in proton SEU events, but only in devices with upset thresholds significantly lower than devices currently flown in space or sold commercially for terrestrial applications. Triple coincidence tagged proton exposures and neutron exposures are combined to demonstrate these reactions in the same device.

  8. Study of particle rebound characteristics and material erosion at high temperature: Final technical report for period April 1984 to December 1986

    SciTech Connect

    Tabakoff, W.; Hamed, A.; Eroglu, H.

    1987-01-01

    The Laser Doppler Velocimeter (LDV) system was used to measure the rebounding characteristics of 15 micron mean diameter fly ash particles impacting several target materials. The rebounding velocities and angles were determined for 410 stainless steel, 2024 aluminum, 6A1-4V titanium, INCO 718, RENE 41, AM355, L605 cobalt, and alumina (Al/sub 2/O/sub 3/) target materials at different impact angles. In addition, AM355 steel alloys were tested at five different impact velocities of 75, 150, 320, 450 and 650 ft/sec. Rebounding measurements were also taken for 2024 aluminum alloy, using 200 microns mean diameter sand particles. A comparison was made between the rebounding results using sand and ash particles. Tests were also conducted with two different L605 cobalt sample material thicknesses. An erosion study was conducted to measure the erosion rate for the 2024 aluminum, 6A1-4V titanium, 304 stainless steel, RENE 41, A286, AM355 and L605 cobalt target materials impacted by fly ash particles. The effect of the following parameters on erosion was investigated: particle sizes, composition, velocity, impingement angle and temperature. 14 refs., 122 figs., 16 tabs.

  9. Growth mechanism, distribution characteristics and reinforcing behavior of (Ti, Nb)C particle in laser cladded Fe-based composite coating

    NASA Astrophysics Data System (ADS)

    Li, Qingtang; Lei, Yongping; Fu, Hanguang

    2014-10-01

    Over the past decade, researchers have demonstrated much interest in laser cladded metal matrix composite coatings for its good wear resistance, corrosion resistance, and high temperature properties. In this paper, in-situ (Ti, Nb)C particle reinforced Fe-based composite coatings were produced by laser cladding. The effects of Ti/Nb(atomic ratio) in the cladding powder on the formation mechanism and distribution characteristics of multiple particle were investigated. The results showed that when Ti/Nb > 1, Ti had a stronger ability to bond with C compared with Nb. (Ti, Nb)C multiple particles with TiC core formed in the molten pool. With the decrease of Ti/Nb, core-shell structure disappeared, the structure of particle got close to that of NbC gradually. It is found that the amount, area ratio and distribution of the reinforced particle in the coating containing Ti and Nb elements were improved, compared with these in the coating containing equal Nb element. When Ti/Nb = 1, the effects above-mentioned is most prominent, and the wear resistance of the coating is promoted obviously.

  10. Psychometric Characteristics of Role-Play Assessments of Social Skill in Schizophrenia

    ERIC Educational Resources Information Center

    Bellack, Alan S.; Brown, Clayton H.; Thomas-Lohrman, Shannon

    2006-01-01

    There is an extensive literature documenting that people with schizophrenia have marked impairments in social role functioning and social skill. One of the most widely employed strategies for assessing social skill has been role-play tests: simulated social interactions that are videotaped for subsequent behavioral coding. There has been…

  11. Detailed diesel exhaust characteristics including particle surface area and lung deposited dose for better understanding of health effects in human chamber exposure studies

    NASA Astrophysics Data System (ADS)

    Wierzbicka, Aneta; Nilsson, Patrik T.; Rissler, Jenny; Sallsten, Gerd; Xu, Yiyi; Pagels, Joakim H.; Albin, Maria; Österberg, Kai; Strandberg, Bo; Eriksson, Axel; Bohgard, Mats; Bergemalm-Rynell, Kerstin; Gudmundsson, Anders

    2014-04-01

    Several diesel exhaust (DE) characteristics, comprising both particle and gas phase, recognized as important when linking with health effects, are not reported in human chamber exposure studies. In order to understand effects of DE on humans there is a need for better characterization of DE when performing exposure studies. The aim of this study was to determine and quantify detailed DE characteristics during human chamber exposure. Additionally to compare to reported DE properties in conducted human exposures. A wide battery of particle and gas phase measurement techniques have been used to provide detailed DE characteristics including the DE particles (DEP) surface area, fraction and dose deposited in the lungs, chemical composition of both particle and gas phase such as NO, NO2, CO, CO2, volatile organic compounds (including aldehydes, benzene, toluene) and polycyclic aromatic hydrocarbons (PAHs). Eyes, nose and throat irritation effects were determined. Exposure conditions with PM1 (<1 μm) mass concentration 280 μg m-3, number concentration 4 × 105 cm-3 and elemental to total carbon fraction of 82% were generated from a diesel vehicle at idling. When estimating the lung deposited dose it was found that using the size dependent effective density (in contrast to assuming unity density) reduced the estimated respiratory dose by 132% by mass. Accounting for agglomerated structure of DEP prevented underestimation of lung deposited dose by surface area by 37% in comparison to assuming spherical particles. Comparison of DE characteristics reported in conducted chamber exposures showed that DE properties vary to a great extent under the same DEP mass concentration and engine load. This highlights the need for detailed and standardized approach for measuring and reporting of DE properties. Eyes irritation effects, most probably caused by aldehydes in the gas phase, as well as nose irritation were observed at exposure levels below current occupational exposure limit

  12. Effect of particle size and particle size distribution on physical characteristics, morphology and crystal structure of explosively compacted high-T(sub c) superconductors

    NASA Technical Reports Server (NTRS)

    Kotsis, I.; Enisz, M.; Oravetz, D.; Szalay, A.

    1995-01-01

    A superconductor, of composition Y(Ba,K,Na)2Cu3O(x)/F(y) and a composite of composition Y(Ba,K,Na)2Cu3O(x)/F(y) + Ag, with changing K, Na and F content but a constant silver content (Ag = 10 mass%) was prepared using a single heat treatment. the resulting material was ground in a corundum lined mill, separated to particle size fractions of 0-40 micron, 0-63 micron and 63-900 micron and explosively compacted, using an explosive pressure of 10(exp 4) MPa and a subsequent heat treatment. Best results were obtained with the 63-900 micron fraction of composition Y(Ba(1.95) K(0.01)Cu3O(x)F(0),(05)/Ag: porosity less than 0.01 cu cm/g and current density 2800 A/sq cm at 77K.

  13. Characteristics of regional new particle formation in urban and regional background environments in the North China Plain

    NASA Astrophysics Data System (ADS)

    Wang, Z. B.; Hu, M.; Sun, J. Y.; Wu, Z. J.; Yue, D. L.; Shen, X. J.; Zhang, Y. M.; Pei, X. Y.; Cheng, Y. F.; Wiedensohler, A.

    2013-12-01

    Long-term measurements of particle number size distributions were carried out both at an urban background site (Peking University, PKU) and a regional Global Atmospheric Watch station (Shangdianzi, SDZ) from March to November in 2008. In total, 52 new particle formation (NPF) events were observed simultaneously at both sites, indicating that this is a regional phenomenon in the North China Plain. On average, the mean condensation sink value before the nucleation events started was 0.025 s-1 in the urban environment, which was 1.6 times higher than that at regional site. However, higher particle formation and growth rates were observed at PKU (10.8 cm-3 s-1 and 5.2 nm h-1) compared with those at SDZ (4.9 cm-3 s-1 and 4.0 nm h-1). These results implied that precursors were much more abundant in the polluted urban environment. Different from the observations in cleaner environments, the background conditions of the observed particle homogeneous nucleation events in the North China Plain could be characterized as the co-existing of a stronger source of precursor gases and a higher condensational sink of pre-existing aerosol particles. Secondary aerosol formation following nucleation events results in an increase of particle mass concentration, particle light scattering coefficient, and cloud condensation nuclei (CCN) number concentration, with consequences on visibility, radiative effects, and air quality. Typical regional NPF events with significant particle nucleation rates and subsequent particle growth over a sufficiently long time period at both sites were chosen to investigate the influence of NPF on the number concentration of "potential" CCN. As a result, the NPF and the subsequent condensable growth increased the CCN number concentration in the North China Plain by factors in the range from 5.6 to 8.7. Moreover, the potential contribution of anthropogenic emissions to the CCN number concentration was more than 50%, to which more attention should be drawn in

  14. Brownian motion of a nano-colloidal particle: the role of the solvent.

    PubMed

    Torres-Carbajal, Alexis; Herrera-Velarde, Salvador; Castañeda-Priego, Ramón

    2015-07-15

    Brownian motion is a feature of colloidal particles immersed in a liquid-like environment. Usually, it can be described by means of the generalised Langevin equation (GLE) within the framework of the Mori theory. In principle, all quantities that appear in the GLE can be calculated from the molecular information of the whole system, i.e., colloids and solvent molecules. In this work, by means of extensive Molecular Dynamics simulations, we study the effects of the microscopic details and the thermodynamic state of the solvent on the movement of a single nano-colloid. In particular, we consider a two-dimensional model system in which the mass and size of the colloid are two and one orders of magnitude, respectively, larger than the ones associated with the solvent molecules. The latter ones interact via a Lennard-Jones-type potential to tune the nature of the solvent, i.e., it can be either repulsive or attractive. We choose the linear momentum of the Brownian particle as the observable of interest in order to fully describe the Brownian motion within the Mori framework. We particularly focus on the colloid diffusion at different solvent densities and two temperature regimes: high and low (near the critical point) temperatures. To reach our goal, we have rewritten the GLE as a second kind Volterra integral in order to compute the memory kernel in real space. With this kernel, we evaluate the momentum-fluctuating force correlation function, which is of particular relevance since it allows us to establish when the stationarity condition has been reached. Our findings show that even at high temperatures, the details of the attractive interaction potential among solvent molecules induce important changes in the colloid dynamics. Additionally, near the critical point, the dynamical scenario becomes more complex; all the correlation functions decay slowly in an extended time window, however, the memory kernel seems to be only a function of the solvent density. Thus, the

  15. [Characteristics and Formation Mechanism of a Multi-Day Haze in the Winter of Shijiazhuang Using a Single Particle Aerosol Mass Spectrometer (SPAMS)].

    PubMed

    Zhou, Jing-bo; Ren, Yi-bin; Hong, Gang; Lu, Na; Li, Zhi-guo; Li, Lei; Li, Hui-lai; Jin, Wei

    2015-11-01

    A multi-day haze episode occurred in Shijiazhuang during November 18-26, 2014. The characteristics were studied based on the data collected by the single particle aerosol mass spectrometer (SPAMS) located in the automatic monitoring station (20 meters) of Shijiazhuang. In accordance with the source spectral library of atmospheric pollutant emissions in Shijiazhuang, the main sources were distinguished and analyzed. The mass concentration of particulate matters and meteorological conditions being taken in account, the causes of haze in winter were also studied. It turned out that fine particulate matters in the Shijiazhuang air were mainly from 7 different sources: the tracer ion of coal source was Al; the tracer ions of industry sources were OC, Fe, and Pb; the tracer ion of motor vehicle tail gas source was EC; the tracer ions of dust source were Al, Ca and Si; the tracer ions of biomass burning source were K and levoglucosan; the tracer ions of pure secondary inorganic source were SO4-, NO2-, and NO3-, and the tracer ion of dining source was HOC. Of the above mentioned, OC, HOC, EC, HEC, ECOC, rich potassium particles minerals and heavy metals were 8 dominant polluting groups in hazy days. OC and ECOC particles were the majority, which accounted for more than 50% and 20% of the overall measured particles. OC particles were mainly discharged from coal combustion and industrial processes, and ECOC particles were mainly from coal combustion and vehicle exhaust emissions. When haze occurred in Shijiazhuang the proportion of pollutant particles of NH4+, SO4- , NO2- and NO3- increased, of which NH4+ was the most sharply increased. The mixed degree between EC, OC and NH4+, So4-, NO3- in the haze was higher than usual, of which NH4+ was the most sharply increased. In the static and stable weather gaseous (SO2, NO(x), NH3, VOCs) pollutants and particles were difficult to spread and accumulated rapidly, which were discharged from coal combustion, the process of the medical

  16. Particle Engineering of Excipients for Direct Compression: Understanding the Role of Material Properties.

    PubMed

    Mangal, Sharad; Meiser, Felix; Morton, David; Larson, Ian

    2015-01-01

    Tablets represent the preferred and most commonly dispensed pharmaceutical dosage form for administering active pharmaceutical ingredients (APIs). Minimizing the cost of goods and improving manufacturing output efficiency has motivated companies to use direct compression as a preferred method of tablet manufacturing. Excipients dictate the success of direct compression, notably by optimizing powder formulation compactability and flow, thus there has been a surge in creating excipients specifically designed to meet these needs for direct compression. Greater scientific understanding of tablet manufacturing coupled with effective application of the principles of material science and particle engineering has resulted in a number of improved direct compression excipients. Despite this, significant practical disadvantages of direct compression remain relative to granulation, and this is partly due to the limitations of direct compression excipients. For instance, in formulating high-dose APIs, a much higher level of excipient is required relative to wet or dry granulation and so tablets are much bigger. Creating excipients to enable direct compression of high-dose APIs requires the knowledge of the relationship between fundamental material properties and excipient functionalities. In this paper, we review the current understanding of the relationship between fundamental material properties and excipient functionality for direct compression. PMID:26446468

  17. Structured illumination with particle averaging reveals novel roles for yeast centrosome components during duplication.

    PubMed

    Burns, Shannon; Avena, Jennifer S; Unruh, Jay R; Yu, Zulin; Smith, Sarah E; Slaughter, Brian D; Winey, Mark; Jaspersen, Sue L

    2015-01-01

    Duplication of the yeast centrosome (called the spindle pole body, SPB) is thought to occur through a series of discrete steps that culminate in insertion of the new SPB into the nuclear envelope (NE). To better understand this process, we developed a novel two-color structured illumination microscopy with single-particle averaging (SPA-SIM) approach to study the localization of all 18 SPB components during duplication using endogenously expressed fluorescent protein derivatives. The increased resolution and quantitative intensity information obtained using this method allowed us to demonstrate that SPB duplication begins by formation of an asymmetric Sfi1 filament at mitotic exit followed by Mps1-dependent assembly of a Spc29- and Spc42-dependent complex at its tip. Our observation that proteins involved in membrane insertion, such as Mps2, Bbp1, and Ndc1, also accumulate at the new SPB early in duplication suggests that SPB assembly and NE insertion are coupled events during SPB formation in wild-type cells. PMID:26371506

  18. Structured illumination with particle averaging reveals novel roles for yeast centrosome components during duplication

    PubMed Central

    Burns, Shannon; Avena, Jennifer S; Unruh, Jay R; Yu, Zulin; Smith, Sarah E; Slaughter, Brian D; Winey, Mark; Jaspersen, Sue L

    2015-01-01

    Duplication of the yeast centrosome (called the spindle pole body, SPB) is thought to occur through a series of discrete steps that culminate in insertion of the new SPB into the nuclear envelope (NE). To better understand this process, we developed a novel two-color structured illumination microscopy with single-particle averaging (SPA-SIM) approach to study the localization of all 18 SPB components during duplication using endogenously expressed fluorescent protein derivatives. The increased resolution and quantitative intensity information obtained using this method allowed us to demonstrate that SPB duplication begins by formation of an asymmetric Sfi1 filament at mitotic exit followed by Mps1-dependent assembly of a Spc29- and Spc42-dependent complex at its tip. Our observation that proteins involved in membrane insertion, such as Mps2, Bbp1, and Ndc1, also accumulate at the new SPB early in duplication suggests that SPB assembly and NE insertion are coupled events during SPB formation in wild-type cells. DOI: http://dx.doi.org/10.7554/eLife.08586.001 PMID:26371506

  19. The possible role of anisotropy in kinetic electronic excitation of solids by particle bombardment

    NASA Astrophysics Data System (ADS)

    Heuser, C.; Marpe, M.; Diesing, D.; Wucher, A.

    2011-06-01

    The kinetic excitation of a solid surface by impact of energetic particles is investigated by means of internal electron emission across a buried metal-insulator-metal (MIM) tunnel junction. By bombarding the top metal surface of such a device with keV noble gas ions, internal emission yields were determined as a function of projectile impact energy and angle of incidence with respect to the surface normal. In order to understand the observed impact angle dependence, we apply a modified formalism originally published to describe external electron emission. As a result, we find that the measured data can be explained by assuming the spatial distribution of excited electrons propagating towards the buried oxide interface to be strongly influenced by the projectile impact angle. A simple ballistic model assuming excited electrons generated by direct collisions with the projectile to preferably propagate along the direction of the original projectile motion, while electrons excited by scattering from moving recoils propagate isotropically, appears to describe the observed experimental data quite well.

  20. Particle Detectors

    NASA Astrophysics Data System (ADS)

    Grupen, Claus; Shwartz, Boris

    2011-09-01

    Preface to the first edition; Preface to the second edition; Introduction; 1. Interactions of particles and radiation with matter; 2. Characteristic properties of detectors; 3. Units of radiation measurements and radiation sources; 4. Accelerators; 5. Main physical phenomena used for particle detection and basic counter types; 6. Historical track detectors; 7. Track detectors; 8. Calorimetry; 9. Particle identification; 10. Neutrino detectors; 11. Momentum measurement and muon detection; 12. Ageing and radiation effects; 13. Example of a general-purpose detector: Belle; 14. Electronics; 15. Data analysis; 16. Applications of particle detectors outside particle physics; 17. Glossary; 18. Solutions; 19. Resumé; Appendixes; Index.

  1. Effect of the flame temperature on the characteristics of zirconium oxide fine particle synthesized by flame assisted spray pyrolysis

    NASA Astrophysics Data System (ADS)

    Widiyastuti, W.; Machmudah, Siti; Nurtono, Tantular; Winardi, Sugeng

    2013-09-01

    Zirconium oxide fine particles were synthesized by flame assisted spray pyrolysis using zirconium chloride solution as precursor. Propane gas and air were used as a fuel and an oxidizer, respectively. The ratio of flow rate of oxidizer and fuel was maintained constant at 10:1 to ensure a complete combustion. Increasing fuel flow rate led to the increase of temperature distribution in the flame reactor. The intensity of XRD patterns increased with temperature and precursor concentration. Phase composition of zirconium oxide produced by this process consisted of monoclinic and tetragonal phases. The volume fraction of monoclinic phase of zirconium oxide increased with temperature and precursor concentration. The morphology particles observed by SEM resulted in spherical particles with size in the submicron range depending on the precursor concentration.

  2. Charged Particle Characteristics of the ^124Xe+^112,124Sn reactions at 50A MeV

    NASA Astrophysics Data System (ADS)

    McIntosh, A. B.; Hudan, S.; Gosser, Z.; Metelko, C. J.; Rudolph, M.; Yanez, R.; de Souza, R. T.; Chbihi, A.; Famiano, M.; Frégeau, M. O.; Gauthier, J.; Moisan, J.; Roy, R.; Schwarz, C.; Bianchin, S.; Trautmann, W.

    2009-05-01

    To investigate the density dependence of the symmetry energy in the nuclear equation of state, neutrons and charged particles produced in the reactions ^124Xe+^112,124Sn at E/A=50MeV were measured. Charged particles emitted in the angular range 2.8-14.5 were detected with the Indiana array FIRST with good energy and angular resolution. Charged products at larger angles (30-45 ) were detected in the Si strip array LASSA. The DEMON array was used to identify neutrons and measure their kinetic energies using pulse-shape discrimination and TOF. Isotopic resolution was obtained in all charged particle detectors. Energy distributions, angular distributions, and the Z distributions of charged products will be presented. Yields of isotopically resolved fragments will be compared; the effect of the target N/Z on the production of these fragments will be examined.

  3. Role of grain size and particle velocity distribution in secondary electron emission in space plasmas

    NASA Technical Reports Server (NTRS)

    Chow, V. W.; Mendis, D. A.; Rosenberg, M.

    1993-01-01

    By virtue of being generally immersed in a plasma environment, cosmic dust is necessarily electrically charged. The fact that secondary emission plays an important role in determining the equilibrium grain potential has long been recognized, but the fact that the grain size plays a crucial role in this equilibrium potential, when secondary emission is important, has not been widely appreciated. Using both conducting and insulating spherical grains of various sizes and also both Maxwellian and generalized Lorentzian plasmas (which are believed to represent certain space plasmas), we have made a detailed study of this problem. In general, we find that the secondary emission yield delta increases with decreasing size and becomes very large for grains whose dimensions are comparable to the primary electron penetration depth, such as in the case of the very small grains observed at comet Halley and inferred in the interstellar medium. Moreover, we observed that delta is larger for insulators and equilibrium potentials are generally more positive when the plasma has a broad non-Maxwellian tail. Interestingly, we find that for thermal energies that are expected in several cosmic regions, grains of different sizes can have opposite charge, the smaller ones being positive while the larger ones are negative. This may have important consequences for grain accretion in polydisperse dusty space plasmas.

  4. Over time and space changing characteristics of estuarine suspended particles in the German Weser and Elbe estuaries

    NASA Astrophysics Data System (ADS)

    Papenmeier, Svenja; Schrottke, Kerstin; Bartholomä, Alexander

    2014-01-01

    Fine cohesive, suspended sediments appear in all estuarine environments in a predominately flocculated state. The transport and deposition of these flocs is influenced by their in-situ and primary particle size distribution. Especially the size of the inorganic particles influences the density and hence the settling velocity of the flocculated material. To describe both the changes in primary particle size of suspended particulate matter as well as the variability of floc sizes over time and space, the data of In-Situ Particle-Size Distributions (ISPSDs), Primary Particle Size Distributions (PPSDs) and Suspended Sediment Concentrations (SSCs) were collected. For this, Laser In-Situ Scattering and Transmissiometry (LISST) measurements as well as the water samples were collected in the German Elbe and Weser estuaries, covering seasonal variability of the SSC. The data of the ISPSDs show that the inorganic and organic Suspended Particulate Matter (SPM), as found in the Elbe and Weser estuaries, mostly appears in a flocculated state. The substrate for organic matter is mainly imported from the seaside and transported into the estuaries as indicated by an upstream decrease of the amount of fine particles. In winter, when the freshwater discharge is high, different PPSDs are found in the case of the Elbe estuary in the Turbidity Maximum Zone (TMZ) as well as in the landward and in the seaward sections close to the TMZ. In summer, the distance between the seaward and the landward section is too low to obtain an individual PPSD within the Elbe TMZ. A missing correlation between the PPSD and ISPSD shows that the inorganic constituents do not have an influence on the in-situ floc size. Although flocs aggregate and disaggregate over a tidal cycle and with changing SSC, they do not change their PPSD. The microflocs are therefore strong enough to withstand further breakage into their inorganic constituents.

  5. Job characteristics and burnout: The moderating roles of emotional intelligence, motivation and pay among bank employees.

    PubMed

    Salami, Samuel O; Ajitoni, Sunday O

    2016-10-01

    This study investigated the prediction of burnout from job characteristics, emotional intelligence, motivation and pay among bank employees. It also examined the interactions of emotional intelligence, motivation, pay and job characteristics in the prediction of burnout. Data obtained from 230 (Males = 127, Females = 103) bank employees were analysed using Pearson's Product Moment Correlation and multiple regression analysis. Results showed that theses variables jointly and separately negatively predicted burnout components. The results further indicated that emotional intelligence, motivation and pay separately interacted with some job characteristic components to negatively predict some burnout components. The findings imply that emotional intelligence, motivation and pay could be considered by counsellors when designing interventions to reduce burnout among bank employees. PMID:26118824

  6. Effect of particle size and particle size distribution on physical characteristics, morphology and crystal strucutre of explosively compacted high-Tc superconductors

    SciTech Connect

    Kotsis, I.; Enisz, M.; Oravetz, D.

    1994-12-31

    A superconductor, of composition Y(Ba,K,Na){sub 2}Cu{sub 3}O{sub x}/F{sub y} and a composite, of composition Y(Ba,K,Na){sub 2}Cu{sub 3}O{sub x}/F{sub y}+Ag, with changing K, Na and F content, but a constant silver content (Ag=10 mass per cent) was prepared using a single heat treatment. The resulting material was ground in a corundum lined mill, separated to particle size fractions of 0-40 {mu}m, 0-63 {mu}m and 63-900 {mu}m and explosively compacted, using an explosive pressure of 10{sup 4} MPa and a subsequent heat treatment. Best results were obtained with the 63-900 {mu}m fraction of composition Y(Ba{sub 1,95}K{sub 0,01})Cu{sub 3}O{sub x}F{sub 0,05}/Ag: porosity <0.01 cm{sup 3}/g and current density 2800 A/cm{sup 2} at 77 K.

  7. Aquaporin in Chondrosia reniformis Nardo, 1847 and Its Possible Role in the Interaction Between Cells and Engulfed Siliceous Particles.

    PubMed

    Pozzolini, Marina; Ferrando, Sara; Gallus, Lorenzo; Gambardella, Chiara; Ghignone, Stefano; Giovine, Marco

    2016-06-01

    The sponge Chondrosia reniformis selectively engulfs siliceous particles that, when in crystalline form, become quickly dissolved in its ectosome. The molecular mechanism, identity, and physiological significance of the cells involved in this process are not completely understood. In the present study, we applied light and electronic microscopic techniques to show how the quartz particles in C. reniformis are enveloped through collagen fibers and host cells near the surface of these organisms. As various aquaporins from bacteria, animals, and plants bidirectionally conduct metalloids-including silicon ions--through the cell membrane, the presence and potential involvement of aquaporins in quartz dissolution in C. reniformis have been investigated. An aquaporin-like transcript (CrAQP) was isolated according to the transcriptome sequencing results in C. reniformis The full-length CrAQP cDNA is 907 nucleotides long, with a 795-base pair (bp), open reading frame encoding a protein of 265 amino acids, a 29-bp, 5'-non-coding region, and a 83-bp, 3'-untranslated region. The Bayesian phylogenetic inference suggests that CrAqp is closely related to the Aqp8L grade, which is also implicated in H2O2 transport. Quantification of CrAQP mRNA through qPCR indicated that the transcript level was higher in the ectosome than in the choanosome. Immunofluorescence of a mammalian AQP8 in C. reniformis showed positivity in some cells near the quartz particles, a finding that may support the initial hypothesis of the potential involvement of CrAQP in quartz erosion. However, the features of the primary structure of this protein offer a new viewpoint about the functional role of these molecules in this process: that CrAQP may be involved in the permeation of H2O2 released during silica erosion. PMID:27365417

  8. Modelling the role of marine particle on large scale 231Pa, 230Th, Iron and Aluminium distributions

    NASA Astrophysics Data System (ADS)

    Dutay, J.-C.; Tagliabue, A.; Kriest, I.; van Hulten, M. M. P.

    2015-04-01

    The distribution of trace elements in the ocean is governed by the combined effects of various processes, and by exchanges with external sources. Modelling these represents an opportunity to better understand and quantify the mechanisms that regulate the oceanic tracer cycles. Observations collected during the GEOTRACES program provide an opportunity to improve our knowledge regarding processes that should be considered in biogeochemical models to adequately represent the distributions of trace elements in the ocean. Here we present a synthesis about the state of the art for simulating selected trace elements in biogeochemical models: Protactinium, Thorium, Iron and Aluminium. In this contribution we pay particular attention on the role of particles in the cycling of these tracers and how they may provide additional constraints on the transfer of matter in the ocean.

  9. Effects of nano-SiO{sub 2} particles on surface tracking characteristics of silicone rubber composites

    SciTech Connect

    Liu, Yong Li, Zhonglei; Du, Boxue

    2014-09-08

    Compared with neat silicone rubber composites (SiRCs), SiRCs filled with nano-sized SiO{sub 2} particles at weight ratios from 0.1 to 1.0 wt. % exhibit a higher surface flashover voltage and a greater resistance to surface tracking. Scanning electron microscopy images of tracking morphologies indicate that the SiO{sub 2} particles are situated in close proximity to the polymeric chains and act as bridges to stabilize the chains and maintain the structure of the composite. Higher concentrations of nano-sized SiO{sub 2} particles, however, (above 0.3 wt. %) produce defects in the molecular network which lead to reductions in both the surface flashover voltage and the resistance to surface tracking, although these reduced values are still superior to those of neat SiRCs. Therefore, SiRCs filled with nano-sized SiO{sub 2} particles, especially at an optimal weight ratio (0.1 to 0.3 wt. %), may have significant potential applications as outdoor insulators for power systems.

  10. Characteristics of atmospheric ice nucleating particles associated with biomass burning in the US: Prescribed burns and wildfires

    NASA Astrophysics Data System (ADS)

    McCluskey, Christina S.; DeMott, Paul J.; Prenni, Anthony J.; Levin, Ezra J. T.; McMeeking, Gavin R.; Sullivan, Amy P.; Hill, Thomas C. J.; Nakao, Shunsuke; Carrico, Christian M.; Kreidenweis, Sonia M.

    2014-09-01

    An improved understanding of atmospheric ice nucleating particles (INP), including sources and atmospheric abundance, is needed to advance our understanding of aerosol-cloud-climate interactions. This study examines diverse biomass burning events to better constrain our understanding of how fires impact populations of INP. Sampling of prescribed burns and wildfires in Colorado and Georgia, U.S.A., revealed that biomass burning leads to the release of particles that are active as condensation/immersion freezing INP at temperatures from -32 to -12°C. During prescribed burning of wiregrass, up to 64% of INP collected during smoke-impacted periods were identified as soot particles via electron microscopy analyses. Other carbonaceous types and mineral-like particles dominated INP collected during wildfires of ponderosa pine forest in Colorado. Total measured nINP and the excess nINP associated with smoke-impacted periods were higher during two wildfires compared to the prescribed burns. Interferences from non-smoke sources of INP, including long-range transported mineral dust and local contributions of soils and plant materials lofted from the wildfires themselves, presented challenges in using the observations to develop a smoke-specific nINP parameterization. Nevertheless, these field observations suggest that biomass burning may serve as an important source of INP on a regional scale, particularly during time periods that lack other robust sources of INP such as long-range transported mineral dust.

  11. Particle size distribution characteristics of cotton gin first stage seed-cotton cleaning system total particulate emissions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This report is part of a project to characterize cotton gin emissions from the standpoint of total particulate stack sampling and particle size analyses. In 2013, EPA published a more stringent standard for particulate matter with nominal diameter less than or equal to 2.5 µm (PM2.5). This created a...

  12. Particle size distribution characteristics of cotton gin third stage seed-cotton cleaning system total particulate emissions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This report is part of a project to characterize cotton gin emissions from the standpoint of total particulate stack sampling and particle size analyses. In 2013, EPA published a more stringent standard for particulate matter with nominal diameter less than or equal to 2.5 µm (PM2.5). This created a...

  13. Particle size distribution characteristics of cotton gin second stage seed-cotton cleaning system total particulate emissions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This report is part of a project to characterize cotton gin emissions from the standpoint of total particulate stack sampling and particle size analyses. In 2013, EPA published a more stringent standard for particulate matter with nominal diameter less than or equal to 2.5 µm (PM2.5). This created a...

  14. Spanish Maintenance among English-Speaking Latino Youth: The Role of Individual and Social Characteristics

    ERIC Educational Resources Information Center

    Lutz, Amy

    2006-01-01

    This paper investigates the effects of individual, family, social and demographic characteristics on the maintenance of Spanish among English-speaking Latino youth. This research finds effects of generation, gender, race, parent's English proficiency, single-parent status, parental income, and neighborhood concentration of co-ethnics as well as…

  15. The Role of Task and Listener Characteristics in Second Language Listening

    ERIC Educational Resources Information Center

    Brunfaut, Tineke; Révész, Andrea

    2015-01-01

    This study investigated the relationship between second language (L2) listening and a range of task and listener characteristics. More specifically, for a group of 93 nonnative English speakers, the researchers examined the extent to which linguistic complexity of the listening task input and response, and speed and explicitness of the input, were…

  16. Correlates of Depressed Mothers' Sensitivity toward Their Infants: The Role of Maternal, Child, and Contextual Characteristics

    ERIC Educational Resources Information Center

    van Doesum, Karin T. M.; Hosman, Clemens M. H.; Riksen-Walraven, J. Marianne; Hoefnagels, Cees

    2007-01-01

    Objective: To examine various maternal, child, and contextual characteristics, as well as the number of risk factors present, to distinguish which factors explain variance in the sensitivity of depressed mothers toward their infants. Method: Participants were depressed mothers (n = 84) with their infants ages 1 month up to 1 year. Mothers were…

  17. Work Characteristics and Parent-Child Relationship Quality: The Mediating Role of Temporal Involvement

    ERIC Educational Resources Information Center

    Roeters, Anne; Van Der Lippe, Tanja; Kluwer, Esther S.

    2010-01-01

    This study investigated whether the amount and nature of parent-child time mediated the association between parental work characteristics and parent-child relationship quality. We based hypotheses on the conflict and enrichment approaches, and we tested a path model using self-collected data on 1,008 Dutch fathers and 929 Dutch mothers with…

  18. Characteristics of the International Educator and the Strategic Role of Critical Incidents

    ERIC Educational Resources Information Center

    Savva, Maria

    2015-01-01

    This study explored the characteristics of the international educator through a qualitative analysis of initial decisions to teach abroad. Using interview data from 30 Anglophone educators based across three international schools in China and the Netherlands, the investigation looked beyond surface motives to explore the deeper values which…

  19. Gender Differences in Intrahousehold Schooling Outcomes: The Role of Sibling Characteristics and Birth-Order Effects

    ERIC Educational Resources Information Center

    Rammohan, Anu; Dancer, Diane

    2008-01-01

    In this paper we examine the influence of gender, sibling characteristics and birth order on the schooling attainment of school-age Egyptian children. We use multivariate analysis to simultaneously examine three different schooling outcomes of a child having "no schooling", "less than the desired level of schooling", and an "age-appropriate level…

  20. Escaping Poverty for Low-Wage Workers: The Role of Employer Characteristics and Changes.

    ERIC Educational Resources Information Center

    Holzer, Harry J.; Lane, Julia I.; Vilhuber, Lars

    A study analyzed the extent to which escape from or entry into low-wage status among adult workers is associated with changes in employers and their characteristics. The research used a database that consisted of quarterly establishment records of the employment earnings of almost all individuals (11,207,031) who worked in Illinois from the first…

  1. The Pathway to Excellence: The Role of Psychological Characteristics in Negotiating the Challenges of Musical Development

    ERIC Educational Resources Information Center

    MacNamara, Áine; Holmes, Patricia; Collins, Dave

    2006-01-01

    The pathway to excellence is turbulent and aspiring musicians must cope with the "ebb and flow" of development if they are to realise their potential. With this in mind, internationally renowned musicians were interviewed in order to identify the challenges of each stage of musical development and the psychological characteristics that…

  2. Improving Service Delivery: Investigating the Role of Information Sharing, Job Characteristics, and Employee Satisfaction

    ERIC Educational Resources Information Center

    Bontis, Nick; Richards, David; Serenko, Alexander

    2011-01-01

    Purpose: The purpose of this study is to propose and test a model designed to investigate the impact of job characteristics, employee satisfaction, and information sharing on two key indicators of quality service delivery, such as worker perceptions of their efficiency and customer focus. Design/methodology/approach: During the project, 9,060…

  3. Promoting Ethnic Tolerance and Patriotism: The Role of Education System Characteristics

    ERIC Educational Resources Information Center

    Janmaat, Jan Germen; Mons, Nathalie

    2011-01-01

    The literature on political socialization has overlooked the influence of system characteristics of schooling on civic values and youth political identities. This article addresses that gap by investigating the degree to which system differentiation relates to the values of ethnic tolerance and patriotism. We distinguish between pedagogical…

  4. Explaining the Relationship between Insecure Attachment and Partner Abuse: The Role of Personality Characteristics

    ERIC Educational Resources Information Center

    Buck, Nicole M. L.; Leenaars, Ellie P. E. M.; Emmelkamp, Paul M. G.; van Marle, Hjalmar J. C.

    2012-01-01

    Studies have found that male batterers are more often insecurely attached as compared with nonbatterers. However, it is still not clear how insecure attachment is related to domestic violence. Many studies compared batterers and nonbatterers regarding pathological personality characteristics that are related to attachment (e.g., dependency,…

  5. The Role of Psychosocial Characteristics in Criminal Convictions among Cocaine and Gambling Clients in Treatment

    ERIC Educational Resources Information Center

    Martin, Gina; Macdonald, Scott; Ishiguro, Sonya

    2013-01-01

    This study assessed the relative importance of problem gambling, cocaine use and selected psychosocial characteristics in predicting criminal convictions. A self-administered questionnaire was completed by clients when admitted to a treatment program for a primary problem with cocaine (n = 300), gambling (n = 199), or tobacco (n = 249). The…

  6. Characteristics of slag, fly ash and deposited particles during melting of dewatered sewage sludge in a pilot plant.

    PubMed

    Kanchanapiya, Premrudee; Sakano, Takeo; Kanaoka, Chikao; Mikuni, Tokuyoshi; Ninomiya, Yoshihiko; Zhang, Lian; Masui, Megumi; Masami, Furuuchi

    2006-04-01

    This study examines slag, fly ash, and deposited particles during melting of dewatered sewage sludge in a pilot plant. In addition, the chemical composition of particles in flue gas was simulated using a thermodynamics program, namely FACTSage 5.2. The results showed that the main components of slag were Al, Fe, Ca, P and Si; the minor components were Na, K, Mg, Cu, and Zn. The main chemical compound of slag was Ca4(Mg,Fe)5(PO4)6. For fly ash particles, heavy metals with the highest concentrations were in the order of Zn and As, Pb, Cu, and Cd, respectively. For non-heavy metals, Al, Fe and P were also found in significant amounts. The majority of deposited particles were composed of elements of Zn, P, S, Na, Fe, Al, Si, and Ca and such chemical compounds as Zn3(PO4)2, AlPO4, FePO4 and Fe(OH)3 while the minority consisted of elements of As, Cu, and Pb. Moreover, the compositions of deposited particles in each chamber differed due to different flue gas temperatures inside. In the secondary chamber at 760 degrees C, the amounts of Fe and Al were higher than Zn, whereas, in the other chambers (600-400 degrees C), the amount of Zn was higher. In other words, at the lower temperature the deposition of Zn was higher than the deposition of Fe and Al. In the water cooling section, volatile elements (i.e. Zn, As, Cu, Pb) were found in the highest concentrations due to a big difference in temperature between the wall surface and flue gas. From the simulation results, most of the elements in the gas phase were found to be chloride compounds, whereas those in the solid phase were in the form of oxide, sulfate, and phosphate compounds. PMID:16198048

  7. The Characteristics of the Chicago Lake Breeze and Its Effects on Trace Particle Transport: Results from an Episodic Event Simulation.

    NASA Astrophysics Data System (ADS)

    Harris, Lucas; Rao Kotamarthi, V.

    2005-11-01

    The lake-breeze circulation that forms over Lake Michigan during the summer influences the Chicago, Illinois, metropolitan area’s weather in several ways. Of particular significance is the circulation’s effect on the dispersion of pollutants such as ozone and aerosols produced in and around the city. To investigate these effects, the fifth-generation Pennsylvania State University National Center for Atmospheric Research Mesoscale Model (MM5) was used to perform numerical simulations for two lake-breeze events—one in July 1999 and another in July 2002. The model runs were verified with data from several locations around the Chicago area. The simulated breeze circulation decreased the rate of increase in air temperature while penetrating roughly 12 km inland and lasting about 8 h, in reasonable agreement with observations. Furthermore, the inland penetration distance was related to the strength of the maximum vertical velocity within the front. Calculations of trajectories and transport of particles showed that the breeze tended to transport particles trapped within it to the north when release occurred before the circulation came ashore, whereas particles released at the time of the breeze’s landfall or afterward moved more northeasterly, in the direction of the prevailing wind. Thirty-four percent of all released particles were trapped by the circulation and raised to a height of at least 300 m, and 20% of the particles remained in the lowest 100 m above the surface. In addition, sensitivity tests showed little change in the modeled breeze when measured surface temperatures for Lake Michigan were used as initial conditions and boundary conditions in the place of surface skin temperature (as derived by the National Centers for Environmental Prediction). Raising the lake temperatures significantly in the simulation yielded a more elongated vertical circulation and a briefer lake-breeze event that did not reach as far inland.

  8. Activation of endothelial cells after exposure to ambient ultrafine particles: The role of NADPH oxidase

    SciTech Connect

    Mo Yiqun; Wan Rong; Chien Sufan; Tollerud, David J.; Zhang Qunwei

    2009-04-15

    Several studies have shown that ultrafine particles (UFPs) may pass from the lungs to the circulation because of their very small diameter, and induce lung oxidative stress with a resultant increase in lung epithelial permeability. The direct effects of UFPs on vascular endothelium remain unknown. We hypothesized that exposure to UFPs leads to endothelial cell O{sub 2}{sup {center_dot}}{sup -} generation via NADPH oxidase and results in activation of endothelial cells. Our results showed that UFPs, at a non-toxic dose, induced reactive oxygen species (ROS) generation in mouse pulmonary microvascular endothelial cells (MPMVEC) that was inhibited by pre-treatment with the ROS scavengers or inhibitors, but not with the mitochondrial inhibitor, rotenone. UFP-induced ROS generation in MPMVEC was abolished by p67{sup phox} siRNA transfection and UFPs did not cause ROS generation in MPMVEC isolated from gp91{sup phox} knock-out mice. UFP-induced ROS generation in endothelial cells was also determined in vivo by using a perfused lung model with imaging. Moreover, Western blot and immunofluorescence staining results showed that MPMVEC treated with UFPs resulted in the translocation of cytosolic proteins of NADPH oxidase, p47{sup phox}, p67{sup phox} and rac 1, to the plasma membrane. These results demonstrate that NADPH oxidase in the pulmonary endothelium is involved in ROS generation following exposure to UFPs. To investigate the activation of endothelial cells by UFP-induced oxidative stress, we determined the activation of the mitogen-activated protein kinases (MAPKs) in MPMVEC. Our results showed that exposure of MPMVEC to UFPs caused increased phosphorylation of p38 and ERK1/2 MAPKs that was blocked by pre-treatment with DPI or p67{sup phox} siRNA. Exposure of MPMVEC obtained from gp91{sup phox} knock-out mice to UFPs did not cause increased phosphorylation of p38 and ERK1/2 MAPKs. These findings confirm that UFPs can cause endothelial cells to generate ROS directly

  9. The role of angiogenesis in implant dentistry part I: Review of titanium alloys, surface characteristics and treatments

    PubMed Central

    Asatourian, Armen; Garcia-Godoy, Franklin; Sheibani, Nader

    2016-01-01

    Background Angiogenesis plays an important role in osseointegration process by contributing to inflammatory and regenerative phases of surrounding alveolar bone. The present review evaluated the effect of titanium alloys and their surface characteristics including: surface topography (macro, micro, and nano), surface wettability/energy, surface hydrophilicity or hydrophobicity, surface charge, and surface treatments of dental implants on angiogenesis events, which occur during osseointegration period. Material and Methods An electronic search was performed in PubMed, MEDLINE, and EMBASE databases via OVID using the keywords mentioned in the PubMed and MeSH headings regarding the role of angiogenesis in implant dentistry from January 2000-April 2014. Results Of the 2,691 articles identified in our initial search results, only 30 met the inclusion criteria set for this review. The hydrophilicity and topography of dental implants are the most important and effective surface characteristics in angiogenesis and osteogenesis processes. The surface treatments or modifications of dental implants are mainly directed through the enhancement of biological activity and functionalization in order to promote osteogenesis and angiogenesis, and accelerate the osseointegration procedure. Conclusions Angiogenesis is of great importance in implant dentistry in a manner that most of the surface characteristics and treatments of dental implants are directed toward creating a more pro-angiogenic surface on dental implants. A number of studies discussed the effect of titanium alloys, dental implant surface characteristic and treatments on agiogenesis process. However, clinical trials and in-vivo studies delineating the mechanisms of dental implants, and their surface characteristics or treatments, action in angiogenesis processes are lagging. Key words:Angiogenesis, dental implant, osseointergration. PMID:27031073

  10. [Characteristics of particle size structure of plankton community in turbidity zone of near-shore waters, Liaoning Province of Northeast China].

    PubMed

    Song, Lun; Wang, Nian-bin; Song, Yong-Gang; Li, Nan

    2013-04-01

    Estuary and nearshore waters have complicated environment, where plankton community has a frequent feedback regulation and a very unstable particle size structure. In this paper, an investigation was made on the particle size structure of plankton in the turbidity zone of nearshore and port area waters in Liaoning Province of Northeast China. In the waters with high concentration inorganic nitrogen, phytoplankton biomass was mainly of small particle sizes, with the equivalent sphere diameter (ESD) being primarily 20-100 micro m, while in low nutrient waters, the phytoplankton biomass was mainly of larger size particles, with the ESD>100 micro m, indicating that the phytoplankton feedback regulation caused the phytoplankton community to be comprised of small sized organisms as part of the biological responses to high concentration suspended solids, which reduced the individual number of larger organisms such as Coscinodiscus. sp. and other species, and in turn, directly affected the fisheries resources, including a variety of fish and shrimp larvae fed on phytoplankton. A normalized biomass size spectrum with the characteristics of nearshore shallow aquatic oceanic ecosystems exhibiting eutrophication was constructed. The spectrum slope indicated that the plankton community biomass would gradually increase in size. The feasibility of using dinoflagellates and cladocerans as the bio-indicators for eutrophication was discussed. PMID:23898643

  11. The role of particle-to-cell interactions in dictating nanoparticle aided magnetophoretic separation of microalgal cells

    NASA Astrophysics Data System (ADS)

    Toh, Pey Yi; Ng, Bee Wah; Ahmad, Abdul Latif; Chieh, Derek Chan Juinn; Lim, Jitkang

    2014-10-01

    Successful application of a magnetophoretic separation technique for harvesting biological cells often relies on the need to tag the cells with magnetic nanoparticles. This study investigates the underlying principle behind the attachment of iron oxide nanoparticles (IONPs) onto microalgal cells, Chlorella sp. and Nannochloropsis sp., in both freshwater and seawater, by taking into account the contributions of various colloidal forces involved. The complex interplay between van der Waals (vdW), electrostatic (ES) and Lewis acid-base interactions (AB) in dictating IONP attachment was studied under the framework of extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) analysis. Our results showed that ES interaction plays an important role in determining the net interaction between the Chlorella sp. cells and IONPs in freshwater, while the AB and vdW interactions play a more dominant role in dictating the net particle-to-cell interaction in high ionic strength media (>=100 mM NaCl), such as seawater. XDLVO predicted effective attachment between cells and surface functionalized IONPs (SF-IONPs) with an estimated secondary minimum of -3.12 kT in freshwater. This prediction is in accordance with the experimental observation in which 98.89% of cells can be magnetophoretically separated from freshwater with SF-IONPs. We have observed successful magnetophoretic separation of microalgal cells from freshwater and/or seawater for all the cases as long as XDLVO analysis predicts particle attachment. For both the conditions, no pH adjustment is required for particle-to-cell attachment.Successful application of a magnetophoretic separation technique for harvesting biological cells often relies on the need to tag the cells with magnetic nanoparticles. This study investigates the underlying principle behind the attachment of iron oxide nanoparticles (IONPs) onto microalgal cells, Chlorella sp. and Nannochloropsis sp., in both freshwater and seawater, by taking into account the

  12. Capillary electrophoresis study on segment/segment system for segments based on phase of mixed micelles and its role in transport of particles between the two segments.

    PubMed

    Oszwałdowski, Sławomir; Kubáň, Pavel

    2015-09-18

    Capillary electrophoresis coupled with contactless conductivity detector was applied to characterize BGE/segment/segment/BGE and BGE/segment/electrolyte/segment/BGE systems, where segment is the phase of mixed micelles migrating surrounded by BGE and composition of the first segment≠second segment. It was established that both systems are subject of evolution during electrophoretic run induced by different electrophoretic mobilities of segments and the phenomenon that generates the evolution is exchange of micelles between the two segments. This leads to segments re-equilibration during a run, which generates sub-zones from the two segments in the form of a cumulative zone or two isolated zones, depending on the injection scheme applied. Further analysis based on the system BGE/segment/electrolyte/segment/BGE shows that electrolyte solution between segments can act as a spacer to isolate the two micellar segments, and thereby to control the exchange of micelles between the two segments. Established features for both systems were further implemented towards characterization of the transport of nanocrystals (NCs) between two segments using CE/UV-vis technique and two examples were discussed: (i) on-line coating of NCs with surfactants and (ii) distribution of NCs between segments. The former aspect was found to be useful to discuss the state of particle in micellar media, whereas the latter shows system ability for the transport of NCs from the first segment or BGE based sample to the second segment, controlled by the electrolyte characteristics. It was concluded that transport of micelles and NCs is the subject of the same phenomena since basic electrolyte characteristics, i.e. length and concentration, act in the same way. This means that NCs in these systems can play the role of pseudomicelles, which mimic behaviour of micelles. Definitely, the tools established in the present work can be used to examine dynamic phenomena for pseudophase during electrophoresis

  13. HIV testing among MSM in Bogotá, Colombia: The role of structural and individual characteristics

    PubMed Central

    Reisen, Carol A.; Zea, Maria Cecilia; Bianchi, Fernanda T.; Poppen, Paul J.; del Río González, Ana Maria; Romero, Rodrigo A. Aguayo; Pérez, Carolin

    2014-01-01

    This study used mixed methods to examine characteristics related to HIV testing among men who have sex with men (MSM) in Bogotá, Colombia. A sample of 890 MSM responded to a computerized quantitative survey. Follow-up qualitative data included 20 in-depth interviews with MSM and 12 key informant interviews. Hierarchical logistic set regression indicated that sequential sets of variables reflecting demographic characteristics, insurance coverage, risk appraisal, and social context each added to the explanation of HIV testing. Follow-up logistic regression showed that individuals who were older, had higher income, paid for their own insurance, had had a sexually transmitted infection, knew more people living with HIV, and had greater social support were more likely to have been tested for HIV at least once. Qualitative findings provided details of personal and structural barriers to testing, as well as interrelationships among these factors. Recommendations to increase HIV testing among Colombian MSM are offered. PMID:25068180

  14. The role of manipulator characteristics in selecting the ideal effective vehicle

    NASA Technical Reports Server (NTRS)

    Hess, R. A.

    1981-01-01

    A structural model of the human pilot is introduced and discussed. The model is used to provide a rationale for certain nonlinear pilot control behavior such as stick pulsing and serves as a framework for studying aspects of motor skill development. In light of the theoretical background provided by the model, some past empirical pilot response phenomena are analyzed and shown to be attributable to manipulator or control stick characteristics. In particular, some recent problems associated with pilot/vehicle performance in glideslope tracking in short takeoff and landing (STOL) aircraft are analyzed. The apparent contribution of the cockpit manipulator (throttle) characteristics to these problems are outlined and a solution proposed and evaluated in both simulation and flight test.

  15. Phenotypic and Genotypic Characteristics of Small Colony Variants and Their Role in Chronic Infection

    PubMed Central

    Johns, Benjamin E.; Purdy, Kevin J.; Tucker, Nicholas P.; Maddocks, Sarah E.

    2015-01-01

    Small colony variant (SCV) bacteria arise spontaneously within apparently homogeneous microbial populations, largely in response to environmental stresses, such as antimicrobial treatment. They display unique phenotypic characteristics conferred in part by heritable genetic changes. Characteristically slow growing, SCVs comprise a minor proportion of the population from which they arise but persist by virtue of their inherent resilience and host adaptability. Consequently, SCVs are problematic in chronic infection, where antimicrobial treatment is administered during the acute phase of infection but fails to eradicate SCVs, which remain within the host causing recurrent or chronic infection. This review discusses some of the phenotypic and genotypic changes that enable SCVs to successfully proliferate within the host environment as potential pathogens and strategies that could ameliorate the resolution of infection where SCVs are present. PMID:26448688

  16. The Relationship between Neighborhood Characteristics and Effective Parenting Behaviors: The Role of Social Support

    PubMed Central

    Byrnes, Hilary F.; Miller, Brenda A.

    2011-01-01

    Neighborhood characteristics have been linked to healthy behavior, including effective parenting behaviors. This may be partially explained through the neighborhood’s relation to parents’ access to social support from friends and family. The current study examined associations of neighborhood characteristics with parenting behaviors indirectly through social support. The sample included 614 mothers of 11–12 year old youths enrolled in a health care system in the San Francisco area. Structural equations modeling shows that neighborhood perceptions were related to parenting behaviors, indirectly through social support, while archival census neighborhood indicators were unrelated to social support and parenting. Perceived neighborhood social cohesion and control were related to greater social support, which was related to more effective parenting style, parent-child communication, and monitoring. Perceived neighborhood disorganization was unrelated to social support. Prevention strategies should focus on helping parents build a social support network that can act as a resource in times of need. PMID:23794774

  17. Thermolysis characteristics of salts of o-phthalic acid with the formation of Fe, Co, Ni, Cu metal particles

    NASA Astrophysics Data System (ADS)

    Yudanova, L. I.; Logvinenko, V. A.; Yudanov, N. F.; Rudina, N. A.; Ishchenko, A. V.; Korol'kov, I. V.; Semyannikov, P. P.; Sheludyakova, L. A.; Alferova, N. I.

    2016-06-01

    Studies of the thermolysis of ortho-[Ni(H2O)2(C8H4O4)](H2O)2, [Cu(H2O)(C8H4O4)], and acid [M(H2O)6](C8H5O4)2 (M(II) = Fe(II), Co(II), and Ni(II)), [Cu(H2O)2(C8H5O4)2] phthalates reveal that the solid products of their decomposition are composites with nanoparticles embedded in carbon-polymer matrices. Metallic nanoparticles with oxide nanoparticle impurities are detected in iron/cobalt polymer composites, while nickel/copper composites are composed of only metallic particles. It is found that nickel nanoparticles with the diameters of 6-8 nm are covered with disordered graphene layers, while the copperbased composite matrix contains spherical conglomerates (50-200 nm) with numerous spherical Cu particles (5-10 nm).

  18. Workplace Learning within Teacher Education: The Role of Job Characteristics and Goal Orientation

    ERIC Educational Resources Information Center

    Kyndt, Eva; Donche, Vincent; Gijbels, David; Van Petegem, Peter

    2014-01-01

    Within teacher education, it is widely recognised that internships play a major role in preparing prospective teachers. The current research examines if the learning activities students' undertake in the workplace can be explained by students' goal orientation and their perceptions of the workplace. In addition, it will be investigated…

  19. Negotiating Transitions in Musical Development: The Role of Psychological Characteristics of Developing Excellence

    ERIC Educational Resources Information Center

    MacNamara, Aine; Holmes, Patricia; Collins, Dave

    2008-01-01

    The challenges of developing potential to achieve high-level performance in music are considerable. Furthermore, research is increasingly emphasizing the multidimensional and dynamic construction of talent, along with an awareness of the central role of psycho-behavioural factors in the realization of potential. Moreover, in order to achieve…

  20. Why Are Socially Anxious Adolescents Rejected by Peers? The Role of Subject-Group Similarity Characteristics

    ERIC Educational Resources Information Center

    Blote, Anke W.; Bokhorst, Caroline L.; Miers, Anne C.; Westenberg, P. Michiel

    2012-01-01

    This study addressed the role of actual and perceived similarity in peer rejection of socially anxious adolescents. Videotapes of 20 high and 20 low socially anxious adolescents (13-17 years old) giving a speech were rated by groups of unfamiliar peers with regard to perceived similarity and desire for future interaction (lower scores indicating…

  1. The Role of Goal Orientations and Goal Structures in Explaining Classroom Social and Affective Characteristics

    ERIC Educational Resources Information Center

    Polychroni, Fotini; Hatzichristou, Chryse; Sideridis, Georgios

    2012-01-01

    Examining motivational variables may prove to be particularly fruitful towards our understanding of classroom processes, student behaviors and school outcomes. The present study examined the role of personal and contextual goals (goals and goal structures) towards explaining social relationships (peer, teacher-student and home-school). 1493 fifth…

  2. Role Models and the Psychological Characteristics That Buffer Low-Socioeconomic-Status Youth from Cardiovascular Risk

    ERIC Educational Resources Information Center

    Chen, Edith; Lee, William K.; Cavey, Lisa; Ho, Amanda

    2013-01-01

    Little is understood about why some youth from low-socioeconomic-status (SES) environments exhibit good health despite adversity. This study tested whether role models and "shift-and-persist" approaches (reframing stressors more benignly while persisting with future optimism) protect low-SES youth from cardiovascular risk. A total of 163…

  3. VOCALS/Southeast Pacific Science: Role of drizzle and mesoscale organization in determining cloud characteristics

    NASA Astrophysics Data System (ADS)

    Stemmler, J.; Leon, D.; Snider, J.; Sever, G.

    2011-12-01

    The VOCALS-REx campaign took place during October and November of 2008 in the South-Eastern Pacific (SEP) off the Chilean coast. The SEP region is home to a large, semi-permanent area of stratocumulus over the ocean. Within the Sc deck there are clear signatures of embedded mesoscale organization which become more pronounced in the (typically) deeper boundary-layer further to the West. We examine data collected onboard the NSF/NCAR C130 along 20° S. Flight legs were conducted above cloud, in cloud, and below cloud (at ~150m) . The Wyoming Cloud Radar (WCR) and Wyoming Cloud Lidar (WCL) onboard the C130 are used to separate drizzling from non-drizzling segments. In-situ thermodynamic properties are then computed for each regime and examined. We look at variability in structure and mesoscale organization within each leg to determine characteristic properties of both drizzling and non-drizzling regimes. These characteristic properties are used to examine differences in boundary layer decoupling between the two regimes. Finally, legs are broken into individual mesoscale features ('drizzle-cells') identified visually in the WCR and WCL data series. The visual determination of the drizzle-cells is used to assess their characteristic features and to investigate how these structures modulate the properties of the cloud field.

  4. Are middle schools harmful? The role of transition timing, classroom quality and school characteristics.

    PubMed

    Holas, Igor; Huston, Aletha C

    2012-03-01

    Are middle schools ill-suited for early adolescents, or can school characteristics account for any differences in student functioning? Achievement, school engagement, and perceived competence of children starting middle schools in 5th and 6th grades were compared to those of their same-grade peers in elementary schools in a national, longitudinal sample (NICHD Study of Early Child Care and Youth Development, n = 855; 52% Female, 82% White). Classroom quality (observed and teacher-reported) and school characteristics (composition and size) were considered as explanations for any relationships between school-level and student functioning. Fifth grade middle school students did not differ from those in elementary school, but students entering middle school in 6th grade, compared to those in elementary school, experienced lower classroom quality, which in turn predicted slightly lower achievement. They also had lower school engagement, explained by larger school size. Classroom quality and school characteristics predicted youth functioning regardless of school type. We suggest reshaping the research and policy debate with renewed focus on classroom quality and school size instead of grade organization. PMID:22143392

  5. The orbital characteristics of debris particle rings as derived from IDE observations of multiple orbit intersections with LDEF

    NASA Technical Reports Server (NTRS)

    Cooke, William J.; Oliver, John P.; Simon, Charles G.

    1995-01-01

    During the first 346 days of the LDEF's almost 6 year stay in space, the metal oxide silicon detectors of the Interplanetary Dust Experiment (IDE) recorded over 15,000 impacts, most of which were separated in time by integer multiples of the LDEF orbital period (called multiple orbit event sequences, or MOES). Simple celestial mechanics provides ample reason to expect that a good deal of information about the orbits of the impacting debris particles can be extracted from these MOES, and so a procedure, based on the work of Greenberg, has been developed and applied to one of these events, the so-called 'May swarm'. This technique, the 'Method of Differential Precession,' allows for the determination of the geometrical elements of a particle orbit from the change in the position of the impact point with time. The application of this approach to the May swarm gave the following orbital elements for the orbit of the particles striking LDEF during this MOES: a = 6746.5 km; 0.0165 less than e less than 0.025; i = 66.55 deg; Omega(sub 0) = 179.0 deg plus or minus 0.2 deg; omega = 178.1 deg plus or minus 0.2 deg.

  6. The orbital characteristics of debris particle rings as derived from IDE observations of multiple orbit intersections with LDEF

    SciTech Connect

    Cooke, W.J.; Oliver, J.P.; Simon, C.G.

    1995-02-01

    During the first 346 days of the LDEF`s almost 6 year stay in space, the metal oxide silicon detectors of the Interplanetary Dust Experiment (IDE) recorded over 15,000 impacts, most of which were separated in time by integer multiples of the LDEF orbital period (called multiple orbit event sequences, or MOES). Simple celestial mechanics provides ample reason to expect that a good deal of information about the orbits of the impacting debris particles can be extracted from these MOES, and so a procedure, based on the work of Greenberg, has been developed and applied to one of these events, the so-called `May swarm`. This technique, the `Method of Differential Precession,` allows for the determination of the geometrical elements of a particle orbit from the change in the position of the impact point with time. The application of this approach to the May swarm gave the following orbital elements for the orbit of the particles striking LDEF during this MOES: a = 6746.5 km; 0.0165 less than e less than 0.025; i = 66.55 deg; Omega(sub 0) = 179.0 deg plus or minus 0.2 deg; omega = 178.1 deg plus or minus 0.2 deg.

  7. Dynamic and chemical controls on new particle formation occurrence and characteristics from in situ and satellite-based measurements

    NASA Astrophysics Data System (ADS)

    Sullivan, R. C.; Pryor, S. C.

    2016-02-01

    We analyze the association between satellite-based measurements of chemical conditions (sulfur dioxide (SO2), nitrogen dioxide (NO2), and formaldehyde (HCHO) concentrations), insolation (UV), and aerosol particle properties (aerosol optical depth (AOD) and Ångström exponent (AE)); and the occurrence of new particle formation (NPF), formation rates (J6), growth rates (GR), and survival probabilities (SP) using particle size distribution measurements taken during two extended field campaigns at a forested location in southern Indiana. When conditionally sampled by event occurrence and non-occurrence the satellite-derived parameters exhibit significant differences and also show some degree of skill in predicting NPF though logistic regression analysis. During leaf-on measurement periods, NPF occurrence exhibits strong seasonality (NPF is more frequent in spring vs. summer) and is associated with a low condensational sink, while leaf-off NPF occurrence is associated with high near-surface UV receipt. Multiple linear regression equations of J6, GR, and SP using the chemical conditions as predictors exhibit some significant r2 values (p < 0.1), but are relatively unstable and many of the regression coefficients do not differ significantly from zero.

  8. Effect of antiscalants on precipitation of an RO concentrate: metals precipitated and particle characteristics for several water compositions.

    PubMed

    Greenlee, Lauren F; Testa, Fabrice; Lawler, Desmond F; Freeman, Benny D; Moulin, Philippe

    2010-04-01

    Inland brackish water reverse osmosis (RO) is economically and technically limited by the large volume of salty waste (concentrate) produced. The use of a controlled precipitation step, followed by solid/liquid separation (filtration), has emerged as a promising side-stream treatment process to treat reverse osmosis concentrate and increase overall system recovery. The addition of antiscalants to the RO feed prevents precipitation within the membrane system but might have a deleterious effect on a concentrate treatment process that uses precipitation to remove problematic precipitates. The effects of antiscalant type and concentration on salt precipitation and precipitate particle morphology were evaluated for several water compositions. The primary precipitate for the synthetic brackish waters tested was calcium carbonate; the presence of magnesium, sulfate, minor ions, and antiscalant compounds affected the amount of calcium precipitated, as well as the phases of calcium carbonate formed during precipitation. Addition of antiscalant decreased calcium precipitation but increased incorporation of magnesium and sulfate into precipitating calcium carbonate. Antiscalants prevented the growth of nucleated precipitates, resulting in the formation of small (100-200 nm diameter) particles, as well as larger (6-10 microm) particles. Elemental analysis revealed changes in composition and calcium carbonate polymorph with antiscalant addition and antiscalant type. Results indicate that the presence of antiscalants does reduce the extent of calcium precipitation and can worsen subsequent filtration performance. PMID:20172582

  9. Individual Characteristics Influencing Physicians' Perceptions of Job Demands and Control: The Role of Affectivity, Work Engagement and Workaholism.

    PubMed

    Mazzetti, Greta; Biolcati, Roberta; Guglielmi, Dina; Vallesi, Caryn; Schaufeli, Wilmar B

    2016-01-01

    The first purpose of the present study was to investigate the role of individual characteristics, i.e., positive and negative affectivity, in explaining the different perception of job control and job demands in a particularly demanding environment such as the healthcare setting. In addition, we aimed to explore the mediational role of work engagement and workaholism using the Job Demands-Resources Model as a theoretical framework. Data were collected using a sample of 269 Italian head physicians working in nine general hospitals. To test our hypotheses, the collected data were analyzed with structural equation modeling. Moreover, Sobel Test and bootstrapping were employed to assess the mediating hypotheses. Our results indicated that positive affectivity is related to work engagement, which, in its turn, showed a positive association with job control. In addition, workaholism mediated the relationship between negative affectivity and job demands. All in all, this study represents a first attempt to explore the role of trait affectivity as a dispositional characteristic able to foster the level of work engagement and workaholism exhibited by employees and, in turn, to increase the perceived levels of job control and job demands. PMID:27275828

  10. Individual Characteristics Influencing Physicians’ Perceptions of Job Demands and Control: The Role of Affectivity, Work Engagement and Workaholism

    PubMed Central

    Mazzetti, Greta; Biolcati, Roberta; Guglielmi, Dina; Vallesi, Caryn; Schaufeli, Wilmar B.

    2016-01-01

    The first purpose of the present study was to investigate the role of individual characteristics, i.e., positive and negative affectivity, in explaining the different perception of job control and job demands in a particularly demanding environment such as the healthcare setting. In addition, we aimed to explore the mediational role of work engagement and workaholism using the Job Demands-Resources Model as a theoretical framework. Data were collected using a sample of 269 Italian head physicians working in nine general hospitals. To test our hypotheses, the collected data were analyzed with structural equation modeling. Moreover, Sobel Test and bootstrapping were employed to assess the mediating hypotheses. Our results indicated that positive affectivity is related to work engagement, which, in its turn, showed a positive association with job control. In addition, workaholism mediated the relationship between negative affectivity and job demands. All in all, this study represents a first attempt to explore the role of trait affectivity as a dispositional characteristic able to foster the level of work engagement and workaholism exhibited by employees and, in turn, to increase the perceived levels of job control and job demands. PMID:27275828

  11. Effect of Spray Particle Velocity on Cavitation Erosion Resistance Characteristics of HVOF and HVAF Processed 86WC-10Co4Cr Hydro Turbine Coatings

    NASA Astrophysics Data System (ADS)

    Kumar, R. K.; Kamaraj, M.; Seetharamu, S.; Pramod, T.; Sampathkumaran, P.

    2016-06-01

    The hydro plants utilizing silt-laden water for power generation suffer from severe metal wastage due to particle-induced erosion and cavitation. High-velocity oxy-fuel process (HVOF)-based coatings is widely applied to improve the erosion life. The process parameters such as particle velocity, size, powder feed rate, temperature, affect their mechanical properties. The high-velocity air fuel (HVAF) technology, with higher particle velocities and lower spray temperatures, gives dense and substantially nonoxidized coating. In the present study, the cavitation resistance of 86WC-10Co4Cr-type HVOF coating processed at 680 m/s spray particle velocity was compared with HVAF coatings made at 895, 960, and 1010 m/s. The properties such as porosity, hardness, indentation toughness, and cavitation resistance were investigated. The surface damage morphology has been analyzed in SEM. The cohesion between different layers has been examined qualitatively through scratch depth measurements across the cross section. The HVAF coatings have shown a lower porosity, higher hardness, and superior cavitation resistance. Delamination, extensive cracking of the matrix interface, and detachment of the WC grains were observed in HVOF coating. The rate of metal loss is low in HVAF coatings implying that process parameters play a vital role in achieving improved cavitation resistance.

  12. Effect of Spray Particle Velocity on Cavitation Erosion Resistance Characteristics of HVOF and HVAF Processed 86WC-10Co4Cr Hydro Turbine Coatings

    NASA Astrophysics Data System (ADS)

    Kumar, R. K.; Kamaraj, M.; Seetharamu, S.; Pramod, T.; Sampathkumaran, P.

    2016-08-01

    The hydro plants utilizing silt-laden water for power generation suffer from severe metal wastage due to particle-induced erosion and cavitation. High-velocity oxy-fuel process (HVOF)-based coatings is widely applied to improve the erosion life. The process parameters such as particle velocity, size, powder feed rate, temperature, affect their mechanical properties. The high-velocity air fuel (HVAF) technology, with higher particle velocities and lower spray temperatures, gives dense and substantially nonoxidized coating. In the present study, the cavitation resistance of 86WC-10Co4Cr-type HVOF coating processed at 680 m/s spray particle velocity was compared with HVAF coatings made at 895, 960, and 1010 m/s. The properties such as porosity, hardness, indentation toughness, and cavitation resistance were investigated. The surface damage morphology has been analyzed in SEM. The cohesion between different layers has been examined qualitatively through scratch depth measurements across the cross section. The HVAF coatings have shown a lower porosity, higher hardness, and superior cavitation resistance. Delamination, extensive cracking of the matrix interface, and detachment of the WC grains were observed in HVOF coating. The rate of metal loss is low in HVAF coatings implying that process parameters play a vital role in achieving improved cavitation resistance.

  13. Biological response to nano-scale titanium dioxide (TiO2): role of particle dose, shape, and retention.

    PubMed

    Silva, Rona M; Teesy, Christel; Franzi, Lisa; Weir, Alex; Westerhoff, Paul; Evans, James E; Pinkerton, Kent E

    2013-01-01

    Titanium dioxide (TiO2) is one of the most widely used nanomaterials, valued for its highly refractive, photocatalytic, and pigmenting properties. TiO2 is also classified by the International Agency for Research on Cancer (IARC) as a possible human carcinogen. The objectives of this study were to (1) establish a lowest-observed-effect level (LOEL) for nano-scale TiO2, (2) determine TiO2 uptake in the lungs, and (3) estimate toxicity based on physicochemical properties and retention in the lungs. In vivo lung toxicity of nano-scale TiO2 using varying forms of well-characterized, highly dispersed TiO2 was assessed. Anatase/rutile P25 spheres (TiO2-P25), pure anatase spheres (TiO2-A), and anatase nanobelts (TiO2-NB) were tested. To determine the effects of dose and particle characteristics, male Sprague-Dawley rats were administered TiO2 (0, 20, 70, or 200 μg) via intratracheal instillation. Bronchoalveolar lavage fluid (BALF) and lung tissue were obtained for analysis 1 and 7 d post exposure. Despite abundant TiO2 inclusions in all exposed animals, only TiO2-NB displayed any significant degree of inflammation seen in BALF at the 1-d time point. This inflammation resolved by 7 d, although TiO2 particles had not cleared from alveolar macrophages recovered from the lung. Histological examination showed TiO2-NB produced cellular changes at d 1 that were still evident at d 7. Data indicate TiO2-NB is the most inflammatory with a LOEL of 200 μg at 1 d post instillation. PMID:24156719

  14. The role of cognitive styles and sociodemographic characteristics in consumer perceptions and attitudes toward nonhuman animal welfare.

    PubMed

    Musto, Mauro; Faraone, Daniela; Cellini, Francesco

    2014-01-01

    Given the increasing importance of exploring consumers' concerns about the welfare of farmed animals, a survey questionnaire was designed to investigate the role of cognitive styles along with sociodemographic characteristics in consumers' perceptions about nonhuman animal welfare (AW) and their willingness to pay for animal-friendly products. The results revealed that the survey respondents were concerned about AW and had negative perceptions of the way animals were treated. They showed positive attitudes toward some actions to be taken for improving AW and strongly agreed to pay more for animal-friendly products. Consistent with previous studies, results revealed significant associations between sociodemographics and concern toward AW. However, some observed differences were highlighted by cognitive styles rather than by sociodemographic characteristics. These results indicate a significant link between cognitive styles and perceptions and attitudes toward AW, which may outweigh previously found sociodemographic differences and fuel the contemporary debate on AW. PMID:24749930

  15. A study on the combustion characteristics of PVC, poly(styrene), poly(ethylene), and poly(propylene) particles under high heating rates

    SciTech Connect

    Panagiotou, T.; Levendis, Y. . Dept. of Mechanical Engineering)

    1994-10-01

    The combustion characteristics of four commonly encountered plastics: poly(styrene), PVC, poly(ethylene) and poly(propylene) were studied under conditions pertinent to incinerators, that is, high heating rates (in the order of 10,000 K/s) and elevated gas temperatures (1,200--1,500 K). Batches of spherical and monodisperse particles of these plastics were generated in the size range of 53--300 [mu]m. Combustion of single particles, of known size and mass, was conducted in a laminar-flow drop-tube furnace, at controlled atmospheres. The radiation emitted from burning particles was monitored, along their flight path, by simultaneous three-color optical pyrometry and high-speed cinematography. Results indicate that polymer particles (plastics) burned expediently with burntimes similar to those of light oil drops such as kerosene, hexadecane, etc. Both PVC and poly(styrene) burned with very luminous yellow flames, which were attributed to high soot loadings. The flame combustion of PVC was the brightest and fastest with steadily decreasing temperature and flame diameter, while that of poly(styrene) occurred mostly at constant flame diameter and mildly decreasing temperature. Combustion of both poly(ethylene) and poly(propylene) was dimmer and somewhat lengthier. Furthermore, in this temperature region, it is argued herein that the combustion of poly(styrene), poly(ethylene), and poly(propylene) occurred concurrently with, and was partially controlled by, pyrolysis reactions. PVC seemed to undergo significant pyrolysis prior to ignition; thereafter, combustion occurred in a premixed-like flame mode and, finally, dimly glowing combustion of the remaining char was observed. PVC exhibited the highest soot volume fraction in its flame, followed by poly(styrene); poly(propylene), and poly(ethylene). Moreover, it was observed that the rate of burning was the highest for PVC particles and the lowest for poly(ethylene).

  16. Modelling large solar proton events with the shock-and-particle model. Extraction of the characteristics of the MHD shock front at the cobpoint

    NASA Astrophysics Data System (ADS)

    Pomoell, Jens; Aran, Angels; Jacobs, Carla; Rodríguez-Gasén, Rosa; Poedts, Stefaan; Sanahuja, Blai

    2015-06-01

    We have developed a new version of a model that combines a two-dimensional Sun-to-Earth magnetohydrodynamic (MHD) simulation of the propagation of a CME-driven shock and a simulation of the transport of particles along the interplanetary magnetic field (IMF) line connecting the shock front and the observer. We assume that the shock-accelerated particles are injected at the point along the shock front that intersects this IMF line, i.e. at the cobpoint. Novel features of the model are an improved solar wind model and an enhanced fully automated algorithm to extract the necessary plasma characteristics from the shock simulation. In this work, the new algorithms have been employed to simulate the 2000 April 4 and the 2006 December 13 SEP events. In addition to quantifying the performance of the new model with respect to results obtained using previous versions of the shock-and-particle model, we investigate the semi-empirical relation between the injection rate of shock-accelerated particles, Q, and the jump in speed across the shock, VR, known as the Q(VR) relation. Our results show that while the magnetic field and density compression at the shock front is markedly different than in our previous modeling, the evolution of VR remains largely similar. As a result, we confirm that a simple relation can still be established between Q and VR, which enables the computation of synthetic intensity-time profiles at any location in interplanetary space. Furthermore, the new shock extraction tool is found to yield improved results being in general more robust. These results are important not only with regard to efforts to develop coupled magnetohydrodynamic and particle simulation models, but also to improve space weather related software tools that aim to predict the peak intensities, fluences and proton intensity-time profiles of SEP events (such as the SOLPENCO tool).

  17. Quantifying the role of climate and landscape characteristics on hydrologic partitioning and vegetation response

    NASA Astrophysics Data System (ADS)

    Voepel, Hal; Ruddell, Benjamin; Schumer, Rina; Troch, Peter A.; Brooks, Paul D.; Neal, Andrew; Durcik, Matej; Sivapalan, Murugesu

    2011-10-01

    There is no consensus on how changes in both temperature and precipitation will affect regional vegetation. We investigated controls on hydrologic partitioning at the catchment scale across many different ecoregions, and compared the resulting estimates of catchment wetting and vaporization (evapotranspiration) to remotely sensed indices of vegetation greenness. The fraction of catchment wetting vaporized by plants, known as the Horton index, is strongly related to the ratio of available energy to available water at the Earth's surface, the aridity index. Here we show that the Horton index is also a function of catchment mean slope and elevation, and is thus related to landscape characteristics that control how much and how long water is retained in a catchment. We compared the power of the components of the water and energy balance, as well as landscape characteristics, to predict Normalized Difference Vegetation Index (NDVI), a surrogate for vegetation productivity, at 312 Model Parameter Estimation Experiment (MOPEX) catchments across the United States. Statistical analysis revealed that the Horton index provides more precision in predicting maximum annual NDVI for all catchments than mean annual precipitation, potential evapotranspiration, or their ratio, the aridity index. Models of vegetation productivity should emphasize plant-available water, rather than just precipitation, by incorporating the interaction of climate and landscape. Major findings related to the Horton index are: (1) it is a catchment signature that is relatively constant from year-to-year; (2) it is related to specific landscape characteristics; (3) it can be used to create catchment typologies; and (4) it is related to overall catchment greenness.

  18. Cancer-Associated Fibroblasts: Their Characteristics and Their Roles in Tumor Growth

    PubMed Central

    Shiga, Kazuyoshi; Hara, Masayasu; Nagasaki, Takaya; Sato, Takafumi; Takahashi, Hiroki; Takeyama, Hiromitsu

    2015-01-01

    Cancer tissues are composed of cancer cells and the surrounding stromal cells (e.g., fibroblasts, vascular endothelial cells, and immune cells), in addition to the extracellular matrix. Most studies investigating carcinogenesis and the progression, invasion, metastasis, and angiogenesis of cancer have focused on alterations in cancer cells, including genetic and epigenetic changes. Recently, interactions between cancer cells and the stroma have attracted considerable attention, and increasing evidence has accumulated on this. Several researchers have gradually clarified the origins, features, and roles of cancer-associated fibroblasts (CAFs), a major component of the cancer stroma. CAFs function in a similar manner to myofibroblasts during wound healing. We previously reported the relationship between CAFs and angiogenesis. Interleukin-6 (IL-6), a multifunctional cytokine, plays a central role in regulating inflammatory and immune responses, and important roles in the progression, including proliferation, migration, and angiogenesis, of several cancers. We showed that CAFs are an important IL-6 source and that anti-IL-6 receptor antibody suppressed angiogenesis and inhibited tumor-stroma interactions. Furthermore, CAFs contribute to drug-resistance acquisition in cancer cells. The interaction between cancer cells and the stroma could be a potential target for anti-cancer therapy. PMID:26690480

  19. Characteristic of copper matrix simultaneously reinforced with nano- and micro-sized Al{sub 2}O{sub 3} particles

    SciTech Connect

    Rajkovic, Viseslava Bozic, Dusan; Devecerski, Aleksandar; Jovanovic, Milan T.

    2012-05-15

    The effect of the simultaneous presence of nano- and micro-sized Al{sub 2}O{sub 3} particles on the microstructure and properties of copper matrix was the object of this study. The mixture of inert gas-atomized prealloyed copper powder (with 1 wt.% Al) and 0.6 wt.% commercial Al{sub 2}O{sub 3} powder (serving as micro-sized particles) was used as the starting materials. Strengthening of the copper matrix was performed by treating the powders in the air for up to 20 h in the planetary ball mill. During milling of the prealloyed powder, finely dispersed nano-sized Al{sub 2}O{sub 3} particles were formed in situ by internal oxidation. The approximate size of these particles was between 30 and 60 nm. The highest values of microhardness were reached in compacts processed from 10 h-milled powders. The microhardness of compact obtained from 10 h-milled powder was 3 times higher than the microhardness of compact processed from as-received and non-milled prealloyed powder. At the maximum microhardness the grain size reaches the smallest value as a result of the synergetic effect of nano- and micro-sized Al{sub 2}O{sub 3} particles. Recrystallization, which occurred during prolonged milling, was the main factor influencing the decrease in microhardness. The increase in electrical conductivity of compacts after 15 h of milling is the result of the decrease in microhardness and activated recrystallization processes. Highlights: Black-Right-Pointing-Pointer Copper matrix was reinforced with nano- and micro-sized Al{sub 2}O{sub 3} particles. Black-Right-Pointing-Pointer The twofold role of coarse Al{sub 2}O{sub 3} particles in matrix strengthening exists. Black-Right-Pointing-Pointer During shorter milling time these particles contribute to increase of microhardness. Black-Right-Pointing-Pointer At longer milling time decrease in microhardness is related to recrystallization.

  20. Manager Characteristics and Employee Job Insecurity around a Merger Announcement: The Role of Status and Crossover

    PubMed Central

    Lam, Jack; Fox, Kimberly; Fan, Wen; Moen, Phyllis; Kelly, Erin; Hammer, Leslie; Kossek, Ellen

    2014-01-01

    Most existing research theorizes individual factors as predictors of perceived job insecurity. Incorporating contextual and organizational factors at an information technology organization where a merger was announced during data collection, we draw on status expectations and crossover theories to investigate whether managers’ characteristics and insecurity shape their employees’ job insecurity. We find having an Asian as opposed to a White manager is associated with lower job insecurity, while managers’ own insecurity positively predicts employees’ insecurity. Also contingent on the organizational climate, managers’ own tenure buffers, and managers’ perceived job insecurity magnifies insecurity of employees interviewed after a merger announcement, further specifying status expectations theory by considering context. PMID:26190868

  1. Facebook addiction among Turkish college students: the role of psychological health, demographic, and usage characteristics.

    PubMed

    Koc, Mustafa; Gulyagci, Seval

    2013-04-01

    This study explored Facebook addiction among Turkish college students and its behavioral, demographic, and psychological health predictors. The Facebook Addiction Scale (FAS) was developed and its construct validity was assessed through factor analyses. A total of 447 students reported their personal information and Facebook usage and completed the FAS and General Health Questionnaire (GHQ-28). The results revealed that weekly time commitment, social motives, severe depression, and anxiety and insomnia positively predicted Facebook addiction. Neither demographic variables nor the interactions of gender by usage characteristics were found to be significant predictors. PMID:23286695

  2. Hygroscopicity and CCN activity of atmospheric aerosol particles and their relation to organics: Characteristics of urban aerosols in Nagoya, Japan

    NASA Astrophysics Data System (ADS)

    Kawana, Kaori; Nakayama, Tomoki; Mochida, Michihiro

    2016-04-01

    The size-resolved distributions of hygroscopic growth factor g and the ratios of cloud condensation nuclei (CCN) to condensation nuclei of atmospheric aerosols were investigated in Nagoya, Japan. The average of the distributions of g at 85% relative humidity was bimodal. The size-resolved mean κ derived from g showed an increasing trend with diameter: 0.17-0.33 at 24-359 nm. The κ values calculated from CCN activation curves were 37% higher than those derived from g. Only 9% of the 37% difference is explained by the difference in the κ of inorganics under subsaturated and supersaturated conditions, suggesting a contribution of organics to the remaining 28% difference. The size-averaged κ of organics (κorg) was calculated as 0.14 and 0.19 by two different methods. The number fractions of CCN predicted from the hygroscopicity data over the range of 24-359 nm are loosely consistent with those observed if the size- and time-averaged g is applied to all particles (differences: -30% to +10%). This consistency improves if size- and time-resolved g and g distribution are used (differences: -19% to -3%). Whereas the number fractions of CCN predicted from the composition data are greatly underestimated if organics are assumed to be insoluble (differences: -64% to -45%), they are more consistent if κorg of 0.14 or 0.19 is applied (differences: -10% to +14%). The results demonstrate the importance of the dependence of the g of particles on time and particle size and the hygroscopicity of organics for CCN number concentrations in the urban atmosphere.

  3. Relations between morning sector Pi 1 pulsation activity and particle and field characteristics observed by the DE 2 satellite

    NASA Technical Reports Server (NTRS)

    Engebretson, M. J.; Cahill, L. J., Jr.; Winningham, J. D.; Rosenberg, T. J.; Arnoldy, R. L.; Maynard, N. C.; Sugiura, M.

    1986-01-01

    Ground-based magnetometer, photometer, and riometer data are combined with low-altitude particle and electric and magnetic field data from the DE-2 spacecraft to provide a more complete characterization of the magnetospheric and tropospheric environment in which morning sector asymmetric Pi 1 pulsations are observed. The results of the study are in agreement with recent conclusions that morning sector asymmetric Pi 1 pulsations are physically related to pulsating aurorae. Precipitation of energetic electrons (E greater than 35 keV) coincides in every instance with the occurrence of these pulsations.

  4. [Pollution characteristics and source of the atmospheric fine particles and secondary inorganic compounds at Mount Dinghu in autumn season].

    PubMed

    Liu, Zi-Rui; Wang, Yue-Si; Liu, Quan; Liu, Lu-Ning; Zhang, De-Qiang

    2011-11-01

    Real-time measurements of PM2.5, secondary inorganic compounds in PM2.5 (SO4(2-), NH4(+), and NO3(-)) and related gaseous pollutants were conducted at Mount Dinghu, a regional background station of the Pearl River Delta (PRD), in October and November 2008 by using a conventional R&P TEOM and a system of rapid collection of fine particles and ion chromatography (RCFP-IC). Sources and transportation of atmospheric particles during the experiment were discussed with principal component analysis and backward trajectories calculated using HYSPLIT model. The average daily mass concentrations of PM2.5 were 76.9 microg x m(-3) during sampling period, and average daily mass concentrations of SO4(2-), NH4(+), and NO3(-) were 20.0 microg x m(-3), 6.8 microg x m(-3) and 2.6 microg x m(-3), respectively. The sum of these three secondary inorganic compounds accounted for more than one third of the PM2.5 mass concentration, which had become the major source of atmospheric fine particles at Mount Dinghu. The diurnal variation of PM2.5, SO4(2-), and NH4(+) all showed a "bimodal" distribution with two peaks appeared at 10:00 am and at 16:00 pm, respectively, whereas NO3(-s) howed "single peak" distribution peaked at 10:00 am. The mass concentrations of SO4(2-) in PM2.5 had the similar diurnal variation with that of SO2, SO4(2-) in PM2.5 was mainly transformed from SO2, whereas NO3(-) showed difference diurnal variation with that of NO2, and the second conversion rate of NO2 was far lower than that of SO2. NH4(+) in PM2.5 existed mainly in the form of sulfate, nitrate and chloride. Both of principal component analysis and back trajectory analysis showed that the variations of PM2.5 and secondary inorganic compounds at Mount Dinghu were mainly affected by the long-range transport air mass passed over Guangzhou, Huizhou and other highly industrialized areas which carried air pollutants to the observation site, at the same time local sulfate originated from secondary formation also

  5. Childhood maltreatment and illicit drug use in middle adulthood: the role of neighborhood characteristics.

    PubMed

    Chauhan, Preeti; Widom, Cathy Spatz

    2012-08-01

    This paper examined whether childhood maltreatment increases the risk of living in neighborhoods with less desirable characteristics (i.e., more disorder and disadvantage, less social cohesion, social control and advantage, and fewer resources) in middle adulthood and whether these neighborhood characteristics influence subsequent illicit drug use. Using a prospective cohort design study, court documented cases of childhood abuse and neglect and matched controls (n = 833) were first interviewed as young adults (mean age = 29 years) from 1989 to 1995 and again in middle adulthood from 2000 to 2002 (mean age = 40 years) and 2003 to 2005 (mean age = 41 years). In middle adulthood, individuals with histories of childhood abuse and neglect were more likely to live in neighborhoods with more disorder and disadvantage and less social cohesion and advantage compared to controls and to engage in illicit drug use during the past year. Path analyses showed an indirect effect on illicit drug use via neighborhood disorder among maltreated children, even after accounting for drug abuse symptoms in young adulthood, although this was sex specific and race specific, affecting women and Whites. Overall, child abuse and neglect places children on a negative trajectory that dynamically influences negative outcomes at multiple levels into middle adulthood. PMID:22781851

  6. HOW JOB CHARACTERISTICS AFFECT INTERNATIONAL MIGRATION: THE ROLE OF INFORMALITY IN MEXICO

    PubMed Central

    Blanchard, Sarah

    2016-01-01

    Despite the importance given to employment opportunities as a primary motive for migration, previous studies have paid insufficient attention to the kinds of jobs that are more likely to retain workers in their countries of origin. We use information from a panel survey of Mexican adults to examine how job characteristics affect the risk of international migration. The sampling strategy and overall size of the survey allow us to analyze the effect of employment characteristics on migration from urban areas, which have much greater labor market diversity, and to separate our analysis by gender. We also distinguish migrants according to whether they migrate for work or for other reasons. We find informality to be a significant predictor of international migration. Even after controlling for individual factors including workers’ wages, as well as various household- and community-level predictors, we find that workers employed in the informal sector have significantly higher odds of migrating than their counterparts in the formal sector. The pervasive nature of informality in many developing countries from which a high proportion of international migrants originate may therefore create a constant supply of workers who are predisposed to migrate. Our findings thus have important implications for a proper understanding of the effects of economic development on migration. PMID:23073750

  7. How job characteristics affect international migration: the role of informality in Mexico.

    PubMed

    Villarreal, Andrés; Blanchard, Sarah

    2013-04-01

    Despite the importance given to employment opportunities as a primary motive for migration, previous studies have paid insufficient attention to the kinds of jobs that are more likely to retain workers in their countries of origin. We use information from a panel survey of Mexican adults to examine how job characteristics affect the risk of international migration. The sampling strategy and overall size of the survey allow us to analyze the effect of employment characteristics on migration from urban areas, which have much greater labor market diversity, and to separate our analysis by gender. We also distinguish migrants according to whether they migrate for work or for other reasons. We find informality to be a significant predictor of international migration. Even a