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Sample records for aerodynamic particle size

  1. Intercomparison of 15 aerodynamic particle size spectrometers (APS 3321): uncertainties in particle sizing and number size distribution

    NASA Astrophysics Data System (ADS)

    Pfeifer, S.; Müller, T.; Weinhold, K.; Zikova, N.; Santos, S.; Marinoni, A.; Bischof, O. F.; Kykal, C.; Ries, L.; Meinhardt, F.; Aalto, P.; Mihalopoulos, N.; Wiedensohler, A.

    2015-11-01

    Aerodynamic particle size spectrometers are a well-established method to measure number size distributions of coarse mode particles in the atmosphere. Quality assurance is essential for atmospheric observational aerosol networks to obtain comparable results with known uncertainties. In a laboratory study within the framework of ACTRIS (Aerosols, Clouds, and Trace gases Research Infrastructure Network), 15 aerodynamic particle size spectrometers (APS model 3321, TSI Inc., St. Paul, MN, USA) were compared with a focus on flow rates accuracy, particle sizing, and unit-to-unit variability of the particle number size distribution. Flow rate deviations were relatively small (within a few percent), while the sizing accuracy was found to be within 10 % compared to polystyrene latex (PSL) reference particles. The unit-to-unit variability in terms of the particle number size distribution during this study was within 10-20 % for particles in the range of 0.9 up to 3 μm, which is acceptable for atmospheric measurements. For particles smaller than that, the variability increased up to 60 %, probably caused by differences in the counting efficiencies of individual units. Number size distribution data for particles smaller than 0.9 μm in aerodynamic diameter should be only used with caution. For particles larger than 3 μm, the unit-to-unit variability increased as well. A possible reason is an insufficient sizing accuracy in combination with a steeply sloping particle number size distribution and the increasing uncertainty due to decreasing counting. This uncertainty of the particle number size distribution has especially to be considered if higher moments of the size distribution such as the particle volume or mass are calculated, which require the conversion of the aerodynamic diameter measured to a volume equivalent diameter. In order to perform a quantitative quality assurance, a traceable reference method for the particle number concentration in the size range 0.5-3

  2. Intercomparison of 15 aerodynamic particle size spectrometers (APS 3321): uncertainties in particle sizing and number size distribution

    NASA Astrophysics Data System (ADS)

    Pfeifer, Sascha; Müller, Thomas; Weinhold, Kay; Zikova, Nadezda; Martins dos Santos, Sebastiao; Marinoni, Angela; Bischof, Oliver F.; Kykal, Carsten; Ries, Ludwig; Meinhardt, Frank; Aalto, Pasi; Mihalopoulos, Nikolaos; Wiedensohler, Alfred

    2016-04-01

    Aerodynamic particle size spectrometers are a well-established method to measure number size distributions of coarse mode particles in the atmosphere. Quality assurance is essential for atmospheric observational aerosol networks to obtain comparable results with known uncertainties. In a laboratory study within the framework of ACTRIS (Aerosols, Clouds, and Trace gases Research Infrastructure Network), 15 aerodynamic particle size spectrometers (APS model 3321, TSI Inc., St. Paul, MN, USA) were compared with a focus on flow rates, particle sizing, and the unit-to-unit variability of the particle number size distribution. Flow rate deviations were relatively small (within a few percent), while the sizing accuracy was found to be within 10 % compared to polystyrene latex (PSL) reference particles. The unit-to-unit variability in terms of the particle number size distribution during this study was within 10 % to 20 % for particles in the range of 0.9 up to 3 µm, which is acceptable for atmospheric measurements. For particles smaller than that, the variability increased up to 60 %, probably caused by differences in the counting efficiencies of individual units. Number size distribution data for particles smaller than 0.9 µm in aerodynamic diameter should only be used with caution. For particles larger than 3 µm, the unit-to-unit variability increased as well. A possible reason is an insufficient sizing accuracy in combination with a steeply sloping particle number size distribution and the increasing uncertainty due to decreasing counting. Particularly this uncertainty of the particle number size distribution must be considered if higher moments of the size distribution such as the particle volume or mass are calculated, which require the conversion of the aerodynamic diameter measured to a volume equivalent diameter. In order to perform a quantitative quality assurance, a traceable reference method for the particle number concentration in the size range 0.5-3 µm

  3. A system for aerodynamically sizing ultrafine environmental radioactive particles

    SciTech Connect

    Olawoyin, L.

    1995-09-01

    The unattached environmental radioactive particles/clusters, produced mainly by {sup 222}Rn in indoor air, are usually few nanometers in size. The inhalation of these radioactive clusters can lead to deposition of radioactivity on the mucosal surface of the tracheobronchial tree. The ultimate size of the cluster together with the flow characteristics will determine the depositional site in the human lung and thus, the extent of damage that can be caused. Thus, there exists the need for the determination of the size of the radioactive clusters. However, the existing particle measuring device have low resolution in the sub-nanometer range. In this research, a system for the alternative detection and measurement of the size of particles/cluster in the less than 2 nm range have been developed. The system is a one stage impactor which has a solid state spectrometer as its impaction plate. It`s major feature is the nozzle-to-plate separation, L. The particle size collected changes with L and thus, particle size spectroscopy is achieved by varying L. The number of collected particles is determined by alpha spectroscopy. The size-discriminating ability of the system was tested with laboratory generated radon particles and it was subsequently used to characterize the physical (size) changes associated with the interaction of radon progeny with water vapor and short chain alcohols in various support gases. The theory of both traditional and high velocity jet impactors together with the design and evaluation of the system developed in this study are discussed in various chapters of this dissertation. The major results obtained in the course of the study are also presented.

  4. Investigate the relationship between multiwavelength lidar ratios and aerosol size distributions using aerodynamic particle sizer spectrometer

    NASA Astrophysics Data System (ADS)

    Zhao, Hu; Hua, Dengxin; Mao, Jiandong; Zhou, Chunyan

    2017-02-01

    The real aerosol size distributions were obtained by aerodynamic particle sizer spectrometer (APS) in China YinChuan. The lidar ratios at wavelengths of 355 nm, 532 nm and 1064 nm were calculated using Mie theory. The effective radius of aerosol particles reff and volume C/F ratio (coarse/fine) Vc/f were retrieved from the real aerosol size distributions. The relationship between multiwavelength lidar ratios and particle reff and Vc/f were investigated. The results indicate that the lidar ratio is positive correlated to the particle reff and Vc/f. The lidar ratio is more sensitive to the coarse particles. The short wavelength lidar ratio is more sensitive to the particle Vc/f and the long wavelength lidar ratio is more sensitive to the particle reff. The wavelength dependency indicated that the lidar ratios decrease with increasing the wavelength. The lidar ratios are almost irrelevant to the shape and total particles of aerosol size distributions.

  5. The generation of diesel exhaust particle aerosols from a bulk source in an aerodynamic size range similar to atmospheric particles

    PubMed Central

    Cooney, Daniel J; Hickey, Anthony J

    2008-01-01

    The influence of diesel exhaust particles (DEP) on the lungs and heart is currently a topic of great interest in inhalation toxicology. Epidemiological data and animal studies have implicated airborne particulate matter and DEP in increased morbidity and mortality due to a number of cardiopulmonary diseases including asthma, chronic obstructive pulmonary disorder, and lung cancer. The pathogeneses of these diseases are being studied using animal models and cell culture techniques. Real-time exposures to freshly combusted diesel fuel are complex and require significant infrastructure including engine operations, dilution air, and monitoring and control of gases. A method of generating DEP aerosols from a bulk source in an aerodynamic size range similar to atmospheric DEP would be a desirable and useful alternative. Metered dose inhaler technology was adopted to generate aerosols from suspensions of DEP in the propellant hydrofluoroalkane 134a. Inertial impaction data indicated that the particle size distributions of the generated aerosols were trimodal, with count median aerodynamic diameters less than 100 nm. Scanning electron microscopy of deposited particles showed tightly aggregated particles, as would be expected from an evaporative process. Chemical analysis indicated that there were no major changes in the mass proportion of 2 specific aromatic hydrocarbons (benzo[a]pyrene and benzo[k]fluoranthene) in the particles resulting from the aerosolization process. PMID:19337412

  6. Developing Supersonic Impactor and Aerodynamic Lens for Separation and Handling of Nano-Sized Particles

    SciTech Connect

    Goodarz Ahmadi

    2008-06-30

    A computational model for supersonic flows of compressible gases in an aerodynamic lens with several lenses and in a supersonic/hypersonic impactor was developed. Airflow conditions in the aerodynamic lens were analyzed and contour plots for variation of Mach number, velocity magnitude and pressure field in the lens were evaluated. The nano and micro-particle trajectories in the lens and their focusing and transmission efficiencies were evaluated. The computational model was then applied to design of a aerodynamic lens that could generate focus particle beams while operating under atmospheric conditions. The computational model was also applied to airflow condition in the supersonic/hypersonic impactor. Variations of airflow condition and particle trajectories in the impactor were evaluated. The simulation results could provide understanding of the performance of the supersonic and hypersonic impactors that would be helpful for the design of such systems.

  7. Fluorescent Biological Aerosol Particle Concentrations and Size Distributions Measured with an Ultraviolet Aerodynamic Particle Sizer (UV-APS) in Central Europe

    NASA Astrophysics Data System (ADS)

    Huffman, J. A.; Treutlein, B.; Pöschl, U.

    2009-12-01

    Primary biological aerosol particles (PBAPs), including bacteria, spores and pollen, are essential for the spread of organisms and disease in the biosphere, and numerous studies have suggested that they may be important for atmospheric processes, including the formation of clouds and precipitation. The atmospheric abundance and size distribution of PBAPs, however, are largely unknown. At a semi-urban site in Mainz, Germany, we used an ultraviolet aerodynamic particle sizer (UV-APS) to measure fluorescent biological aerosol particles (FBAPs), which can be regarded as viable bioaerosol particles representing a lower limit for the actual abundance of PBAPs. Fluorescence of non-biological aerosol components are likely to influence the measurement results obtained for fine particles (< 1 µm), but not for coarse particles (1 - 20 µm). Averaged over the four-month measurement period (August - December 2006), the mean number concentration of coarse FBAPs was ~3x10-2 cm-3, corresponding to ~4% of total coarse particle number [1]. The mean mass concentration of FBAPs was ~1 µg m-3, corresponding to ~20% of total coarse particle mass. The FBAP number size distributions exhibited alternating patterns with peaks at various diameters. A pronounced peak at ~3 µm was essentially always observed and can be described by the following campaign-average lognormal fit parameters: geometric mean diameter 3.2 µm, geometric standard deviation 1.3, number concentration 1.6 x 10-2 cm-3. This peak is likely due to fungal spores or agglomerated bacteria, and it exhibited a pronounced diel cycle with maximum intensity during early/mid-morning. FBAP peaks around ~1.5 µm, ~5 µm, and ~13 µm were also observed, but less pronounced and less frequent. These may be explained by single bacterial cells, larger fungal spores, and pollen grains, respectively. The observed number concentrations and characteristic sizes of FBAPs are consistent with microscopic, biological and chemical analyses of

  8. Fluorescent biological aerosol particle concentrations and size distributions measured with an ultraviolet aerodynamic particle sizer (UV-APS) in Central Europe

    NASA Astrophysics Data System (ADS)

    Huffman, J. A.; Treutlein, B.; Pöschl, U.

    2009-08-01

    Primary biological aerosol particles (PBAPs), including bacteria, spores and pollen, are essential for the spread of organisms and disease in the biosphere, and numerous studies have suggested that they may be important for atmospheric processes, including the formation of clouds and precipitation. The atmospheric abundance and size distribution of PBAPs, however, are largely unknown. At a semi-urban site in Mainz, Germany, we used an ultraviolet aerodynamic particle sizer (UV-APS) to measure fluorescent biological aerosol particles (FBAPs), which can be regarded as viable bioaerosol particles representing a lower limit for the actual abundance of PBAPs. Fluorescence of non-biological aerosol components are likely to influence the measurement results obtained for fine particles (<1 μm), but not for coarse particles (1-20 μm). Averaged over the four-month measurement period (August-December 2006), the mean number concentration of coarse FBAPs was ~3×10-2 cm-3, corresponding to ~4% of total coarse particle number. The mean mass concentration of FBAPs was ~1 μg m-3, corresponding to ~20% of total coarse particle mass. The FBAP number size distributions exhibited alternating patterns with peaks at various diameters. A pronounced peak at ~3 μm was essentially always observed and can be described by the following campaign-average lognormal fit parameters: geometric mean diameter 3.2 μm, geometric standard deviation 1.3, number concentration 1.6×10-2 cm-3. This peak is likely due to fungal spores or agglomerated bacteria, and it exhibited a pronounced diel cycle with maximum intensity during early/mid-morning. FBAP peaks around ~1.5 μm, ~5 μm, and ~13 μm were also observed, but less pronounced and less frequent. These may be explained by single bacterial cells, larger fungal spores, and pollen grains, respectively. The observed number concentrations and characteristic sizes of FBAPs are consistent with microscopic, biological and chemical analyses of PBAPs in

  9. Fluorescent biological aerosol particle concentrations and size distributions measured with an Ultraviolet Aerodynamic Particle Sizer (UV-APS) in Central Europe

    NASA Astrophysics Data System (ADS)

    Huffman, J. A.; Treutlein, B.; Pöschl, U.

    2010-04-01

    Primary Biological Aerosol Particles (PBAPs), including bacteria, spores and pollen, are essential for the spread of organisms and disease in the biosphere, and numerous studies have suggested that they may be important for atmospheric processes, including the formation of clouds and precipitation. The atmospheric abundance and size distribution of PBAPs, however, are largely unknown. At a semi-urban site in Mainz, Germany we used an Ultraviolet Aerodynamic Particle Sizer (UV-APS) to measure Fluorescent Biological Aerosol Particles (FBAPs), which provide an estimate of viable bioaerosol particles and can be regarded as an approximate lower limit for the actual abundance of PBAPs. Fluorescence of non-biological aerosol components are likely to influence the measurement results obtained for fine particles (<1 μm), but not for coarse particles (1-20 μm). Averaged over the four-month measurement period (August-December 2006), the mean number concentration of coarse FBAPs was ~3×10-2 cm-3, corresponding to ~4% of total coarse particle number. The mean mass concentration of FBAPs was ~1μg m-3, corresponding to ~20% of total coarse particle mass. The FBAP number size distributions exhibited alternating patterns with peaks at various diameters. A pronounced peak at ~3 μm was essentially always observed and can be described by the following campaign-average lognormal fit parameters: geometric mean diameter 3.2 μm, geometric standard deviation 1.3, number concentration 1.6×10-2 cm-3. This peak is likely due to fungal spores or agglomerated bacteria, and it exhibited a pronounced diel cycle (24-h) with maximum intensity during early/mid-morning. FBAP peaks around ~1.5 μm, ~5 μm, and ~13 μm were also observed, but less pronounced and less frequent. These may be single bacterial cells, larger fungal spores, and pollen grains, respectively. The observed number concentrations and characteristic sizes of FBAPs are consistent with microscopic, biological and chemical

  10. A hybrid chip based on aerodynamics and electrostatics for the size-dependent classification of ultrafine and nano particles.

    PubMed

    Kim, Yong-Ho; Park, Dongho; Hwang, Jungho; Kim, Yong-Jun

    2009-09-21

    Conventional virtual impactors experience a large pressure drop when they classify particles according to size, in particular ultrafine particles smaller than 100 nm in diameter. Therefore, most virtual impactors have been used to classify particles larger than 100 nm. Their cut-off diameters are also fixed by the geometry of their flow channels. In the proposed virtual impactor, particles smaller than 100 nm are accelerated by applying DC potentials to an integrated electrode pair. By the electrical acceleration, the large pressure drop could be significantly decreased and new cut-off diameters smaller than 100 nm could be successfully added. The geometric cut-off diameter (GCD) of the proposed virtual impactor was designed to be 1.0 microm. Performances including the GCD and wall loss were examined by classifying dioctyl sebacate of 100 to 600 nm in size and carbon particles of 0.6 to 10 microm in size. The GCD was measured to be 0.95 microm, and the wall loss was highest at 1.1 microm. To add new cut-off diameters, monodisperse NaCl particles ranging from 15 to 70 nm were classified using the proposed virtual impactor with applying a DC potential of 0.25 to 3.0 kV. In this range of the potential, the new cut-off diameters ranging from 15 to 35 nm was added.

  11. (Aerodynamic focusing of particles and heavy molecules)

    SciTech Connect

    de la Mora, J.F.

    1990-01-08

    By accelerating a gas containing suspended particles or large molecules through a converging nozzle, the suspended species may be focused and therefore used to write fine lines on a surface. Our objective was to study the limits on how narrow this focal region could be as a function of particle size. We find that, for monodisperse particles with masses m{sub p} some 3.6 {times} 10{sup 5} times larger than the molecular mass m of the carrier gas (diameters above some 100{angstrom}), there is no fundamental obstacle to directly write submicron features. However, this conclusion has been verified experimentally only with particles larger than 0.1 {mu}m. Experimental, theoretical and numerical studies on the defocusing role of Brownian motion for very small particles or heavy molecules have shown that high resolution (purely aerodynamic) focusing is impossible with volatile molecules whose masses are typically smaller than 1000 Dalton. For these, the minimal focal diameter after optimization appears to be 5{radical}(m/m{sub p}) times the nozzle diameter d{sub n}. But combinations of focused lasers and aerodynamic focusing appear as promising for direct writing with molecular precursors. Theoretical and numerical schemes capable of predicting the evolution of the focusing beam, including Brownian motion effects, have been developed, although further numerical work would be desirable. 11 refs.

  12. Multivariate data analysis as a semi-quantitative tool for interpretive evaluation of comparability or equivalence of aerodynamic particle size distribution profiles.

    PubMed

    Shi, Shuai; Hickey, Anthony J

    2009-01-01

    The purpose of this article is to investigate the performance of multivariate data analysis, especially orthogonal partial least square (OPLS) analysis, as a semi-quantitative tool to evaluate the comparability or equivalence of aerodynamic particle size distribution (APSD) profiles of orally inhaled and nasal drug products (OINDP). Monte Carlo simulation was employed to reconstitute APSD profiles based on 55 realistic scenarios proposed by the Product Quality Research Institute (PQRI) working group. OPLS analyses with different data pretreatment methods were performed on each of the reconstituted profiles. Compared to unit-variance scaling, equivalence determined based on OPLS analysis with Pareto scaling was shown to be more consistent with the working group assessment. Chi-square statistics was employed to compare the performance of OPLS analysis (Pareto scaling) with that of the combination test (i.e., chi-square ratio statistics and population bioequivalence test for impactor-sized mass) in terms of achieving greater consistency with the working group evaluation. A p value of 0.036 suggested that OPLS analysis with Pareto scaling may be more predictive than the combination test with respect to consistency. Furthermore, OPLS analysis may also be employed to analyze part of the APSD profiles that contribute to the calculation of the mass median aerodynamic diameter. Our results show that OPLS analysis performed on partial deposition sites do not interfere with the performance on all deposition sites.

  13. Aerodynamic Size Classification of Glass Fibers.

    NASA Astrophysics Data System (ADS)

    Laosmaa, Pekka J. J.

    The objective of this research was to examine a technique by which fibers may be aerodynamically classified by diameter and/or length. In this study a system for fiber preparation and generation as well as an in situ fiber classifier were constructed and evaluated. A recently developed technique, the size classification of particles by opposing jets, was modified. The research set-up consisted of (1) a vibrating bed fiber generator, which also functioned as a preselector, (2) an opposing-jet classifier equipped with electrodes and high voltage power supplies to create fiber-aligning electric fields inside the classifier and (3) an optoelectric fiber sensor to measure the concentration and length of fibers. The classified fibers were also collected on filters for the counting and dimensional analysis of the fibers. Some flow instability problems were found during the initial tests of the classifier. They were attributed to random flow fluctuations in the nozzles caused by very small perturbations upstream of the nozzles. Within a critical range of flow Reynolds numbers the flow becomes "intermittent", i.e. it alternates in time between being laminar and turbulent in a random sequence. Small disturbances upstream of the point of consideration can "trigger" the changes from laminar to turbulent flow and the initial disturbance may be "amplified", sending a turbulent flash through the flow system. The classifier performed well with test aerosols after the nozzle flowrate had been decreased to correspond to a lower and less critical Reynolds number and after some modifications had been made to smooth the flow inside the classifier inlet chambers. The cut-off of test aerosols was sharp, but the loss of particles greater than 2.5 (mu)m in aerodynamic diameter was unsatisfactorily high. The classifier was able to classify fibers by aerodynamic diameter, but not as predicted through calculations. The results were difficult to interpret because of the high loss of fibers

  14. Relative precision of inhaler aerodynamic particle size distribution (APSD) metrics by full resolution and abbreviated andersen cascade impactors (ACIs): part 1.

    PubMed

    Mitchell, Jolyon P; Nagel, Mark W; Doyle, Cathy C; Ali, Rubina S; Avvakoumova, Valentina I; Christopher, J David; Quiroz, Jorge; Strickland, Helen; Tougas, Terrence; Lyapustina, Svetlana

    2010-06-01

    The purpose of this study was to compare relative precision of two different abbreviated impactor measurement (AIM) systems and a traditional multi-stage cascade impactor (CI). The experimental design was chosen to provide separate estimates of variability for each impactor type. Full-resolution CIs are useful for characterizing the aerosol aerodynamic particle size distribution of orally inhaled products during development but are too cumbersome, time-consuming, and resource-intensive for other applications, such as routine quality control (QC). This article presents a proof-of-concept experiment, where two AIM systems configured to provide metrics pertinent to QC (QC-system) and human respiratory tract (HRT-system) were evaluated using a hydrofluoroalkane-albuterol pressurized metered dose inhaler. The Andersen eight-stage CI (ACI) served as the benchmark apparatus. The statistical design allowed estimation of precision with each CI configuration. Apart from one source of systematic error affecting extra-fine particle fraction from the HRT-system, no other bias was detected with either abbreviated system. The observed bias was shown to be caused by particle bounce following the displacement of surfactant by the shear force of the airflow diverging above the collection plate of the second impaction stage. A procedure was subsequently developed that eliminated this source of error, as described in the second article of this series (submitted to AAPS PharmSciTech). Measurements obtained with both abbreviated impactors were very similar in precision to the ACI for all measures of in vitro performance evaluated. Such abbreviated impactors can therefore be substituted for the ACI in certain situations, such as inhaler QC or add-on device testing.

  15. Aerodynamic beam generator for large particles

    DOEpatents

    Brockmann, John E.; Torczynski, John R.; Dykhuizen, Ronald C.; Neiser, Richard A.; Smith, Mark F.

    2002-01-01

    A new type of aerodynamic particle beam generator is disclosed. This generator produces a tightly focused beam of large material particles at velocities ranging from a few feet per second to supersonic speeds, depending on the exact configuration and operating conditions. Such generators are of particular interest for use in additive fabrication techniques.

  16. Performance of an aerodynamic particle separator

    SciTech Connect

    Ragland, K.; Han, J.; Aerts, D.

    1996-12-31

    This compact, high-flow device aerodynamically separates small particles from a gas stream by a series of annular truncated airfoils. The operating concept, design and performance of this novel particle separator are described. Tests results using corn starch and post-cyclone coal fly ash are presented. Particle collection efficiencies of 90% for corn starch and 70% for coal fly ash were measured at inlet velocities of 80 ft s{sup {minus}1} (2,700 cfm) and (6 inches) water pressure drop with particle loading up to 4 gr ft{sup {minus}3} in air at standard conditions. Results from computer modeling using FLUENT are presented and compared to the tests. The aerodynamic particle separator is an attractive alternative to a cyclone collector.

  17. USE OF THE AERODYNAMIC PARTICLE SIZER TO MEASURE PM-COARSE

    EPA Science Inventory

    The aerodynamic particle sizer (APS 3321, TSI, Inc.) measures particle size distributions from 0.5 µm to 20 µm by determining the time-of-flight of individual particles in an accelerating flow field. A complete particle size distribution may be determined in a matter of s...

  18. USE OF THE AERODYNAMIC PARTICLE SIZER TO MEASURE PM-COARSE

    EPA Science Inventory

    The aerodynamic particle sizer (APS 3321, TSI, Inc.) measures particle size distributions from 0.5 µm to 20 µm by determining the time-of-flight of individual particles in an accelerating flow field. A complete particle size distribution may be determined in a matter of ...

  19. An approach to evaluating and correcting aerodynamic particle sizer measurements for phantom particle count creation.

    PubMed

    Heitbrink, W A; Baron, P A

    1992-07-01

    An aerodynamic particle sizer (APS) can be used to make real-time measurements of the aerodynamic particle size distribution over the range of 0.5 to 32 microns. This instrument is very useful in conducting health-related aerosol measurements involving aerosol generation, respirator efficiency, and particulate sampling efficiency. One of the two signal processors within the APS can create spurious or phantom particle counts that can significantly affect relative measurements and calculated mass distributions. In the APS, particle size measurement is based upon a particle's transit time between two laser beams that are perpendicular to an accelerating airflow. The signal processors measure each particle's transit from the time between the two pulses of scattered light that are generated as the particle passes through the two laser beams. When only a single pulse from a particle is detected, another pulse can cause the recording of a randomly sized phantom particle. The small particle processor (SPP), which measures particle transit from the times in digital increments of 4 nanoseconds, can create phantom particles; the large particle processor (LPP), which measures particle transit times in digital increments of 66.67 nanoseconds, is designed to prevent the creation of phantom particles. These two processors overlap in the range of 5.2 to 15.4 microns.(ABSTRACT TRUNCATED AT 250 WORDS)

  20. Tandem Differential Mobility Analyzer/Aerodynamic Particle Sizer (APS) Handbook

    SciTech Connect

    Collins, D

    2010-06-18

    The tandem differential mobility analyzer (TDMA) is a single instrument that cycles through a series of complementary measurements of the physical properties of size-resolved submicron particles. In 2008, the TDMA was augmented through the addition of an aerodynamic particle sizer (APS), which extends the upper limit of the measured size distribution into the supermicron range. These two instruments are operated in parallel, but because they are controlled by a common computer and because the size distributions measured by the two are integrated in the produced datastreams, they are described together here. Throughout the day, the TDMA sequentially measures submicron aerosol size distributions and size-resolved hygroscopic growth distributions. More specifically, the instrument is operated as a scanning DMA to measure size distributions and as a TDMA to measure size-resolved hygroscopicity. A typical measurement sequence requires roughly 45 minutes. Each morning additional measurements are made of the relative humidity (RH) dependent hygroscopicity and temperature-dependent volatility of size-resolved particles. When the outside temperature and RH are within acceptable ranges, the hydration state of size-resolved particles is also characterized. The measured aerosol distributions complement the array of aerosol instruments in the Aerosol Observing System (AOS) and provide additional details of the light-scattering and cloud-nucleating characteristics of the aerosol.

  1. Particle Size Analysis.

    ERIC Educational Resources Information Center

    Barth, Howard G.; Sun, Shao-Tang

    1989-01-01

    Presents a review of research focusing on scattering, elution techniques, electrozone sensing, filtration, centrifugation, comparison of techniques, data analysis, and particle size standards. The review covers the period 1986-1988. (MVL)

  2. Particle-Size Analysis

    SciTech Connect

    Gee, Glendon W. ); Or, Dani; J.H. Dane and G.C. Topp

    2002-11-01

    Book Chapter describing methods of particle-size analysis for soils. Includes a variety of classification schemes. Standard methods for size distributions using pipet and hydrometer techniques are described. New laser-light scattering and related techniques are discussed. Complete with updated references.

  3. WOOD STOVE EMISSIONS: PARTICLE SIZE AND CHEMICAL COMPOSITION

    EPA Science Inventory

    The report summarizes wood stove particle size and chemical composition data gathered to date. [NOTE: In 1995, EPA estimated that residential wood combustion (RWC), including fireplaces, accounted for a significant fraction of national particulate matter with aerodynamic diameter...

  4. Sampling efficiency of the TSI aerodynamic particle sizer

    SciTech Connect

    Chen, Y.; Barber, E.M.; Zhang, Y.

    1998-09-01

    The Aerodynamic Particle Sizer (APS) has been tested and used in a variety of laboratory and field situations for indoor air quality research of both industrial and livestock buildings. The APS is capable of providing rapid, real-time measurement of particle size distribution. However, no literature was found in which the sampling efficiency of the APS was addressed. This paper presents a method to evaluate the sampling efficiency of the APS, considering both the aspiration efficiency and the penetration efficiency. Six tests were conducted and measurements were taken by a cascade impact sampler and the APS simultaneously. The results obtained by the APS were compared with the results of the cascade impact sampler.

  5. Resuspension of Particles by Aerodynamic Deagglomeration

    NASA Technical Reports Server (NTRS)

    Fonda, Mark; Petach, Mike; Rogers, C. Fred; Huntington, Judith; Stratton, David; Nishioka, Kenji; Tipo, Mark

    1998-01-01

    A deagglomerator system was developed, characterized by laboratory tests and flown under low gravity (low-g) microgravity conditions. Requirements for a dry powder deagglomeration system were generated by university and National Aeronautics and Space Administration (NASA) scientists from diverse fields of interest including exobiology, planetary sciences, and atmospheric sciences. Existing deagglomeration methods and devices are reviewed. An aerosol generation method suitable for dry powders over a large range of particles sizes and types at high concentrations with consistent deagglomeration efficiency was evaluated. Development of a pulsed-flow laboratory device and experimental approaches to meet the requirements without being g- dependent are described. Results of laboratory one-g quantitative characterization on one type of dry powder particle generator is discussed. Data from NASA low-g tests are summarized.

  6. Aerodynamic levitator for large-sized glassy material production.

    PubMed

    Yoda, Shinichi; Cho, Won-Seung; Imai, Ryoji

    2015-09-01

    Containerless aerodynamic levitation processing is a unique technology for the fabrication of bulk non-crystalline materials. Using conventional aerodynamic levitation, a high reflective index (RI) material (BaTi2O5 and LaO3/2-TiO2-ZrO2 system) was developed with a RI greater than approximately 2.2, which is similar to that of diamond. However, the glass size was small, approximately 3 mm in diameter. Therefore, it is essential to produce large sized materials for future optical materials applications, such as camera lenses. In this study, a new aerodynamic levitator was designed to produce non-crystalline materials with diameters larger than 6 mm. The concept of this new levitator was to set up a reduced pressure at the top of the molten samples without generating turbulent flow. A numerical simulation was also performed to verify the concept.

  7. Effect of sampling volume on dry powder inhaler (DPI)-emitted aerosol aerodynamic particle size distributions (APSDs) measured by the Next-Generation Pharmaceutical Impactor (NGI) and the Andersen eight-stage cascade impactor (ACI).

    PubMed

    Mohammed, Hlack; Roberts, Daryl L; Copley, Mark; Hammond, Mark; Nichols, Steven C; Mitchell, Jolyon P

    2012-09-01

    Current pharmacopeial methods for testing dry powder inhalers (DPIs) require that 4.0 L be drawn through the inhaler to quantify aerodynamic particle size distribution of "inhaled" particles. This volume comfortably exceeds the internal dead volume of the Andersen eight-stage cascade impactor (ACI) and Next Generation pharmaceutical Impactor (NGI) as designated multistage cascade impactors. Two DPIs, the second (DPI-B) having similar resistance than the first (DPI-A) were used to evaluate ACI and NGI performance at 60 L/min following the methodology described in the European and United States Pharmacopeias. At sampling times ≥2 s (equivalent to volumes ≥2.0 L), both impactors provided consistent measures of therapeutically important fine particle mass (FPM) from both DPIs, independent of sample duration. At shorter sample times, FPM decreased substantially with the NGI, indicative of incomplete aerosol bolus transfer through the system whose dead space was 2.025 L. However, the ACI provided consistent measures of both variables across the range of sampled volumes evaluated, even when this volume was less than 50% of its internal dead space of 1.155 L. Such behavior may be indicative of maldistribution of the flow profile from the relatively narrow exit of the induction port to the uppermost stage of the impactor at start-up. An explanation of the ACI anomalous behavior from first principles requires resolution of the rapidly changing unsteady flow and pressure conditions at start up, and is the subject of ongoing research by the European Pharmaceutical Aerosol Group. Meanwhile, these experimental findings are provided to advocate a prudent approach by retaining the current pharmacopeial methodology.

  8. Investigation of dry powder inhaler (DPI) resistance and aerosol dispersion timing on emitted aerosol aerodynamic particle sizing by multistage cascade impactor when sampled volume is reduced from compendial value of 4 L.

    PubMed

    Mohammed, Hlack; Arp, Jan; Chambers, Frank; Copley, Mark; Glaab, Volker; Hammond, Mark; Solomon, Derek; Bradford, Kerry; Russell, Theresa; Sizer, Yvonne; Nichols, Steven C; Roberts, Daryl L; Shelton, Christopher; Greguletz, Roland; Mitchell, Jolyon P

    2014-10-01

    Compendial methods determining dry powder inhaler (DPI)-emitted aerosol aerodynamic particle size distribution (APSD) collect a 4-L air sample containing the aerosol bolus, where the flow, which propagates through the cascade impactor (CI) measurement system from the vacuum source, is used to actuate the inhaler. A previous article described outcomes with two CIs (Andersen eight-stage cascade impactor (ACI) and Next-Generation Pharmaceutical Impactor (NGI)) when the air sample volume was ≤4 L with moderate-resistance DPIs. This article extends that work, examining the hypothesis that DPI flow resistance may be a factor in determining outcomes. APSD measurements were made using the same CI systems with inhalers representing low and high flow resistance extremes (Cyclohaler® and HandiHaler® DPIs, respectively). The ratio of sample volume to internal dead space (normalized volume (V*)) was varied from 0.25 to 1.98 (NGI) and from 0.43 to 3.46 (ACI). Inhaler resistance was a contributing factor to the rate of bolus transfer; the higher resistance DPI completing bolus relocation to the NGI pre-separator via the inlet when V* was as small as 0.25, whereas only ca. 50% of the bolus mass was collected at this condition with the Cyclohaler® DPI. Size fractionation of the bolus from either DPI was completed within the ACI at smaller values of V* than within the NGI. Bolus transfer from the Cyclohaler® capsule and from the HandiHaler® to the ACI system were unaffected by the different flow rise time observed in the two different flow controller systems, and the effects the ACI-based on APSD measurements were marginal.

  9. Evaporation of Water from Particles in the Aerodynamic Lens Inlet: An Experimental Study

    SciTech Connect

    Zelenyuk, Alla; Imre, Dan G.; Cuadra-Rodriguez, Luis A.

    2006-10-01

    The extremely high particle transmission efficiency of aerodynamic lens inlets resulted in their wide use in aerosol mass spectrometers. One of the consequences of a transport of particles from high ambient pressure into the vacuum is that it is accompanied by a rapid drop in relative humidity (RH). Since many atmospheric particles exist in the form of hygroscopic water droplets, a drop in RH may result in a significant loss of water and even a change in phase. To predict how much water will be evaporated is not feasible. Because water loss can effect in addition to particle size, its transmission efficiency, ionization probability and mass spectrum it is imperative to provide definitive experimental data that can serve to guide the field to a reasonable and uniform sampling approach. In this study we present the results of a number of carefully conducted measurements that provide the first experimentally determined benchmark of water evaporation from a range of particles, during their transport through an aerodynamic lens inlet. We conclude that the only sure way to avoid ambiguities during measurements of aerodynamic diameter in instruments that utilize low pressure aerodynamic lens inlets is to dry the particles prior to sampling.

  10. Mass spectrometric analysis and aerodynamic properties of various types of combustion-related aerosol particles

    NASA Astrophysics Data System (ADS)

    Schneider, J.; Weimer, S.; Drewnick, F.; Borrmann, S.; Helas, G.; Gwaze, P.; Schmid, O.; Andreae, M. O.; Kirchner, U.

    2006-12-01

    Various types of combustion-related particles in the size range between 100 and 850 nm were analyzed with an aerosol mass spectrometer and a differential mobility analyzer. The measurements were performed with particles originating from biomass burning, diesel engine exhaust, laboratory combustion of diesel fuel and gasoline, as well as from spark soot generation. Physical and morphological parameters like fractal dimension, effective density, bulk density and dynamic shape factor were derived or at least approximated from the measurements of electrical mobility diameter and vacuum aerodynamic diameter. The relative intensities of the mass peaks in the mass spectra obtained from particles generated by a commercial diesel passenger car, by diesel combustion in a laboratory burner, and by evaporating and re-condensing lubrication oil were found to be very similar. The mass spectra from biomass burning particles show signatures identified as organic compounds like levoglucosan but also others which are yet unidentified. The aerodynamic behavior yielded a fractal dimension (Df) of 2.09 +/- 0.06 for biomass burning particles from the combustion of dry beech sticks, but showed values around three, and hence more compact particle morphologies, for particles from combustion of more natural oak. Scanning electron microscope images confirmed the finding that the beech combustion particles were fractal-like aggregates, while the oak combustion particles displayed a much more compact shape. For particles from laboratory combusted diesel fuel, a Df value of 2.35 was found, for spark soot particles, Df [approximate] 2.10. The aerodynamic properties of fractal-like particles from dry beech wood combustion indicate an aerodynamic shape factor [chi] that increases with electrical mobility diameter, and a bulk density of 1.92 g cm-3. An upper limit of [chi] [approximate] 1.2 was inferred for the shape factor of the more compact particles from oak combustion.

  11. Size effects on insect hovering aerodynamics: an integrated computational study.

    PubMed

    Liu, H; Aono, H

    2009-03-01

    Hovering is a miracle of insects that is observed for all sizes of flying insects. Sizing effect in insect hovering on flapping-wing aerodynamics is of interest to both the micro-air-vehicle (MAV) community and also of importance to comparative morphologists. In this study, we present an integrated computational study of such size effects on insect hovering aerodynamics, which is performed using a biology-inspired dynamic flight simulator that integrates the modelling of realistic wing-body morphology, the modelling of flapping-wing and body kinematics and an in-house Navier-Stokes solver. Results of four typical insect hovering flights including a hawkmoth, a honeybee, a fruit fly and a thrips, over a wide range of Reynolds numbers from O(10(4)) to O(10(1)) are presented, which demonstrate the feasibility of the present integrated computational methods in quantitatively modelling and evaluating the unsteady aerodynamics in insect flapping flight. Our results based on realistically modelling of insect hovering therefore offer an integrated understanding of the near-field vortex dynamics, the far-field wake and downwash structures, and their correlation with the force production in terms of sizing and Reynolds number as well as wing kinematics. Our results not only give an integrated interpretation on the similarity and discrepancy of the near- and far-field vortex structures in insect hovering but also demonstrate that our methods can be an effective tool in the MAVs design.

  12. Comparison of the Grimm 1.108 and 1.109 portable aerosol spectrometer to the TSI 3321 aerodynamic particle sizer for dry particles.

    PubMed

    Peters, Thomas M; Ott, Darrin; O'Shaughnessy, Patrick T

    2006-11-01

    This study compared the response of two optical particle counters with that of an aerodynamic particle sizer. The optical particle counters rely on the amount of incident light scattered at 90 degrees by a particle to measure particle number concentration by optical particle size. Two models of optical particle counters from Grimm Technologies were used: the portable aerosol spectrometer (PAS) 1.108 (0.3-20 microm in 15 channels); and the PAS 1.109 (0.2-20 microm in 30 size channels). With a substantially different operating principle from that employed by the optical particle counters, the aerodynamic particle sizer (APS) model 3321 (TSI, Inc., St Paul, MN, USA) sizes particles according to their behavior in an accelerating flow to provide particle number concentration by aerodynamic size over a slightly narrower size range (0.5-20 microm) in 52 channels. The responses of these instruments were compared for three sizes of monodisperse solid aerosols composed of polystyrene latex spheres and a polydisperse aerosol composed of Arizona test dust. The PASs provided similar results to those from the APS. However, there were systematic differences among instruments in number and mass concentration measurement that depended upon particle size.

  13. Measurements of Primary Biogenic Aerosol Particles with an Ultraviolet Aerodynamic Particle Sizer (UVAPS) During AMAZE-08

    NASA Astrophysics Data System (ADS)

    Wollny, A. G.; Garland, R.; Pöschl, U.

    2008-12-01

    Biogenic aerosols are ubiquitous in the Earth's atmosphere and they influence atmospheric chemistry and physics, the biosphere, climate, and public health. They play an important role in the spread of biological organisms and reproductive materials, and they can cause or enhance human, animal, and plant diseases. Moreover, they influence the Earth's energy budget by scattering and absorbing radiation, and they can initiate the formation of clouds and precipitation as cloud condensation and ice nuclei. The composition, abundance, and origin of biogenic aerosol particles and components are, however, still not well understood and poorly quantified. Prominent examples of primary biogenic aerosol particles, which are directly emitted from the biosphere to the atmosphere, are pollen, bacteria, fungal spores, viruses, and fragments of animals and plants. During the AMazonian Aerosol CharacteriZation Experiment (AMAZE-08) a large number of aerosol and gas-phase measurements were taken on a remote site close to Manaus, Brazil, during a period of five weeks in February and March 2008. The presented study is focused on data from an ultraviolet aerodynamic particle sizer (UVAPS, TSI inc.) that has been deployed for the first time in Amazonia. In this instrument, particle counting and aerodynamic sizing over the range of 0.5-20 μm are complemented by the measurement of UV fluorescence at 355 nm (excitation) and 420-575 nm (emission), respectively. Fluorescence at these wavelengths is characteristic for reduced pyridine nucleotides (e.g., NAD(P)H) and for riboflavin, which are specific for living cells. Thus particles exhibiting fluorescence signals can be regarded as 'viable aerosols' or 'fluorescent bioparticles' (FBAP), and their concentration can be considered as lower limit for the actual abundance of primary biogenic aerosol particles. First data analyses show a pronounced peak of FBAP at diameters around 2-3 μm. In this size range the biogenic particle fraction was

  14. Particle Size Distribution in Aluminum Manufacturing Facilities

    PubMed Central

    Liu, Sa; Noth, Elizabeth M.; Dixon-Ernst, Christine; Eisen, Ellen A.; Cullen, Mark R.; Hammond, S. Katharine

    2015-01-01

    As part of exposure assessment for an ongoing epidemiologic study of heart disease and fine particle exposures in aluminum industry, area particle samples were collected in production facilities to assess instrument reliability and particle size distribution at different process areas. Personal modular impactors (PMI) and Minimicro-orifice uniform deposition impactors (MiniMOUDI) were used. The coefficient of variation (CV) of co-located samples was used to evaluate the reproducibility of the samplers. PM2.5 measured by PMI was compared to PM2.5 calculated from MiniMOUDI data. Mass median aerodynamic diameter (MMAD) and concentrations of sub-micrometer (PM1.0) and quasi-ultrafine (PM0.56) particles were evaluated to characterize particle size distribution. Most of CVs were less than 30%. The slope of the linear regression of PMI_PM2.5 versus MiniMOUDI_PM2.5 was 1.03 mg/m3 per mg/m3 (± 0.05), with correlation coefficient of 0.97 (± 0.01). Particle size distribution varied substantively in smelters, whereas it was less variable in fabrication units with significantly smaller MMADs (arithmetic mean of MMADs: 2.59 μm in smelters vs. 1.31 μm in fabrication units, p = 0.001). Although the total particle concentration was more than two times higher in the smelters than in the fabrication units, the fraction of PM10 which was PM1.0 or PM0.56 was significantly lower in the smelters than in the fabrication units (p < 0.001). Consequently, the concentrations of sub-micrometer and quasi-ultrafine particles were similar in these two types of facilities. It would appear, studies evaluating ultrafine particle exposure in aluminum industry should focus on not only the smelters, but also the fabrication facilities. PMID:26478760

  15. BRL Particle Sizing Interferometer

    DTIC Science & Technology

    1982-07-01

    possible operational conditions. The parameters associated with a fuel spray which may be expected to have a significant impact on PSI performance are...could be obtained for two possible viewing geometries. As Appendix II points out, A can be increased by using slit apertures to reduce Ax. In...particle number density and aerosol mass concentration using the model described in Appendix II. Inputs required are relative slit width Kappa, and

  16. Aerodynamic Ground Effect in Fruitfly Sized Insect Takeoff

    PubMed Central

    Kolomenskiy, Dmitry; Maeda, Masateru; Engels, Thomas; Liu, Hao; Schneider, Kai; Nave, Jean-Christophe

    2016-01-01

    Aerodynamic ground effect in flapping-wing insect flight is of importance to comparative morphologies and of interest to the micro-air-vehicle (MAV) community. Recent studies, however, show apparently contradictory results of either some significant extra lift or power savings, or zero ground effect. Here we present a numerical study of fruitfly sized insect takeoff with a specific focus on the significance of leg thrust and wing kinematics. Flapping-wing takeoff is studied using numerical modelling and high performance computing. The aerodynamic forces are calculated using a three-dimensional Navier–Stokes solver based on a pseudo-spectral method with volume penalization. It is coupled with a flight dynamics solver that accounts for the body weight, inertia and the leg thrust, while only having two degrees of freedom: the vertical and the longitudinal horizontal displacement. The natural voluntary takeoff of a fruitfly is considered as reference. The parameters of the model are then varied to explore possible effects of interaction between the flapping-wing model and the ground plane. These modified takeoffs include cases with decreased leg thrust parameter, and/or with periodic wing kinematics, constant body pitch angle. The results show that the ground effect during natural voluntary takeoff is negligible. In the modified takeoffs, when the rate of climb is slow, the difference in the aerodynamic forces due to the interaction with the ground is up to 6%. Surprisingly, depending on the kinematics, the difference is either positive or negative, in contrast to the intuition based on the helicopter theory, which suggests positive excess lift. This effect is attributed to unsteady wing-wake interactions. A similar effect is found during hovering. PMID:27019208

  17. Resuspension of allergen-containing particles under mechanical and aerodynamic disturbances from human walking

    NASA Astrophysics Data System (ADS)

    Gomes, C.; Freihaut, J.; Bahnfleth, W.

    This study presents and develops a controlled and characterized method to explore the influence of specific occupant activity on the aerosolization of allergen-containing particles. Indoor allergen-related diseases are primarily inhalation sensitized and developed, suggesting an aerobiological pathway of allergen-containing carrier particles from dust reservoir to occupant respiration. But the pathways are not well understood or quantified. The influence of occupant walking on particle aerosolization is simulated by a system in which complex floor disturbances are deconvoluted into aerodynamic and mechanical components. Time resolved particle size distributions are measured for particles resuspended from representative samples of flooring materials and different types of floor disturbances in an environmentally controlled experimental chamber. Results indicate aerodynamic disturbances, relative to mechanical, dominate the particle resuspension behavior. Dust type, dust load and floor type showed marginal influences on a normalized surface loading basis. Humidity effects were not clear since during experiments the floor samples may not have reached moisture partitioning equilibrium with the controlled air humidity. Average resuspension rates ranged from 10 -7 to 10 -3 min -1, having phenomenological consistency with previous, large room or chamber investigations, suggesting the method can be utilized to develop a database for particle resuspension rates.

  18. Characterization of aerodynamic drag force on single particles: Final report

    SciTech Connect

    Kale, S.R.

    1987-10-01

    An electrodynamic balance was used to measure the drag coefficient and also to record the size and shape of spheres, and coal and oil shale particles (100 ..mu..m to 200 ..mu..m in size). The electrodynamic balance consisted of a central, and two end electrodes. The resulting electric field stably suspended a charged particle. A suspended particle, back illuminated by a light emitting diode, was viewed by a video camera. The image was analyzed for particle position control and was calibrated to give the diameter of spheres, or the area equivalent diameter of nonspherical particles. The drag coefficient was calculated from the air velocity and the dc voltage required to keep the particle at the balance center. The particle Reynolds number varied from 0.2 to 13. Three particles each of coal and oil shale were captured and photographed by a scanning electron microscope and the motion of all the particles was recorded on video tape. Drag coefficient vs Reynolds number data for spheres agreed well with correlations. Data for thirteen particles each of coal and oil shale indicated a power law relationship between drag coefficient and Reynolds number. All these particles exhibited higher drag than spheres and were also observed to rotate. The rotation, however, did not affect the drag coefficient. The choice of characteristic dimension affects the drag characteristics of oil shale more strongly than for coal, owing to the flake-like shape of oil shale. 38 figs., 5 tabs.

  19. Comparison of optical particle sizing and cascade impaction for measuring the particle size of a suspension metered dose inhaler.

    PubMed

    Pu, Yu; Kline, Lukeysha C; Khawaja, Nazia; Van Liew, Melissa; Berry, Julianne

    2015-05-01

    Optical techniques for the particle size characterization of metered dose inhaler (MDI) suspensions have been developed as an alternative to the labor-intensive and time-consuming impaction method. In this study, a laser diffraction (LD) apparatus with a liquid cell ("wet cell" method) and a "time-of-flight" apparatus named aerodynamic particle sizer (APS) were utilized to assess MDI suspensions with varied formulation compositions and storage conditions. The results were compared with the conventional Anderson cascade impaction (ACI) data. The two optical methods were able to detect the changes in particle size distributions between formulations, yet to a lesser extent than those observed using the cascade impaction methodology. The median aerodynamic particle size measured by the APS method and the median geometric particle size obtained from the LD method were linearly correlated with the corresponding ACI results in the range of 2-5 µm. It was also found that the APS measurement was biased towards the finer particle size region and resulted in overestimated fine particle fraction (FPF) values which were 2-3 times folds of the ACI results. In conclusion, the optical particle sizing techniques may, under some circumstances, be viable techniques for the rapid assessment of MDI suspensions. The "wet cell" LD method, in particular, is found to be a valuable means of detecting active pharmaceutical ingredient (API) particle size changes in an MDI suspension. Using both the LD and the APS methods in early formulation screening followed by a final assessment with cascade impaction analysis can improve the efficiency of MDI formulation development.

  20. Small-particle-size cement

    SciTech Connect

    Ewert, D.P.; Almond, S.W.; Blerhaus, W.M. II )

    1991-05-01

    Successful remedial cementing has historically been difficult in wells with large-interval, multizone, gravel-packed completions. The reason is the inability of conventional oilfield cements to penetrate gravel packs adequately. Small-particle-size cement (SPSC) was developed to penetrate gravel packs and to provide the zonal isolation required. This paper details the laboratory work, job design, and field implementation of this new cement.

  1. Global Evolution of Solid Matter in Turbulent Protoplanetry Disks. Part 1; Aerodynamics of Solid Particles

    NASA Technical Reports Server (NTRS)

    Stepinski, T. F.; Valageas, P.

    1996-01-01

    The problem of planetary system formation and its subsequent character can only be addressed by studying the global evolution of solid material entrained in gaseous protoplanetary disks. We start to investigate this problem by considering the space-time development of aerodynamic forces that cause solid particles to decouple from the gas. The aim of this work is to demonstrate that only the smallest particles are attached to the gas, or that the radial distribution of the solid matter has no momentary relation to the radial distribution of the gas. We present the illustrative example wherein a gaseous disk of 0.245 solar mass and angular momentum of 5.6 x 10(exp 52) g/sq cm/s is allowed to evolve due to turbulent viscosity characterized by either alpha = 10(exp -2) or alpha = 10(exp -3). The motion of solid particles suspended in a viscously evolving gaseous disk is calculated numerically for particles of different sizes. In addition we calculate the global evolution of single-sized, noncoagulating particles. We find that particles smaller than 0.1 cm move with the gas; larger particles have significant radial velocities relative to the gas. Particles larger than 0.1 cm but smaller than 10(exp 3) cm have inward radial velocities much larger than the gas, whereas particles larger than 10(exp 4) cm have inward velocities much smaller than the gas. A significant difference in the form of the radial distribution of solids and the gas develops with time. It is the radial distribution of solids, rather than the gas, that determines the character of an emerging planetary system.

  2. Aerodynamic Limits on Large Civil Tiltrotor Sizing and Efficiency

    NASA Technical Reports Server (NTRS)

    Acree, C W., Jr.

    2014-01-01

    The NASA Large Civil Tiltrotor (2nd generation, or LCTR2) has been the reference design for avariety of NASA studies of design optimization, engine and gearbox technology, handling qualities, andother areas, with contributions from NASA Ames, Glenn and Langley Centers, plus academic and industrystudies. Ongoing work includes airfoil design, 3D blade optimization, engine technology studies, andwingrotor aerodynamic interference. The proposed paper will bring the design up to date with the latestresults of such studies, then explore the limits of what aerodynamic improvements might hope toaccomplish. The purpose is two-fold: 1) determine where future technology studies might have the greatestpayoff, and 2) establish a stronger basis of comparison for studies of other vehicle configurations andmissions.

  3. Aerodynamic Limits on Large Civil Tiltrotor Sizing and Efficiency

    NASA Technical Reports Server (NTRS)

    Acree, C W.

    2014-01-01

    The NASA Large Civil Tiltrotor (2nd generation, or LCTR2) is a useful reference design for technology impact studies. The present paper takes a broad view of technology assessment by examining the extremes of what aerodynamic improvements might hope to accomplish. Performance was analyzed with aerodynamically idealized rotor, wing, and airframe, representing the physical limits of a large tiltrotor. The analysis was repeated with more realistic assumptions, which revealed that increased maximum rotor lift capability is potentially more effective in improving overall vehicle efficiency than higher rotor or wing efficiency. To balance these purely theoretical studies, some practical limitations on airframe layout are also discussed, along with their implications for wing design. Performance of a less efficient but more practical aircraft with non-tilting nacelles is presented.

  4. Recent trends in particle size analysis techniques

    NASA Technical Reports Server (NTRS)

    Kang, S. H.

    1984-01-01

    Recent advances and developments in the particle-sizing technologies are briefly reviewed in accordance with three operating principles including particle size and shape descriptions. Significant trends of the particle size analysing equipment recently developed show that compact electronic circuitry and rapid data processing systems were mainly adopted in the instrument design. Some newly developed techniques characterizing the particulate system were also introduced.

  5. Chromate content versus particle size for aircraft paints.

    PubMed

    LaPuma, Peter T; Rhodes, Brian S

    2002-12-01

    Many industries rely on the corrosion inhibiting properties of chromate-containing primer paints to protect metal from oxidation. However, chromate contains hexavalent chromium (Cr(6+)), a known human carcinogen. The concentration of Cr(6+) as a function of paint particle size has important implications to worker health and environmental release from paint facilities. This research examines Cr(6+) content as a function of particle size for three types of aircraft primer paints: solvent-based epoxy-polyamide, water-based epoxy-polyamide, and solvent-based polyurethane. Cascade impactors were used to collect and separate paint particles based on their aerodynamic diameter, from 0.7 to 34.1 microm. The mass of the dry paint collected at each stage was determined and an atomic absorption spectrometer was used to analyze for Cr(6+) content. For all three paints, particles less than 7.0 microm contained disproportionately less Cr(6+) per mass of dry paint than larger particles, and the Cr(6+)concentration decreased substantially as particle size decreased. The smallest particles, 0.7 to 1.0 microm, contained approximately 10% of the Cr(6+) content, per mass of dry paint, compared to particles larger than 7.0 microm. The paint gun settings of air to paint ratio was found to have no influence on the Cr(6+) bias.

  6. A relationship between maximum packing of particles and particle size

    NASA Technical Reports Server (NTRS)

    Fedors, R. F.

    1979-01-01

    Experimental data indicate that the volume fraction of particles in a packed bed (i.e. maximum packing) depends on particle size. One explanation for this is based on the idea that particle adhesion is the primary factor. In this paper, however, it is shown that entrainment and immobilization of liquid by the particles can also account for the facts.

  7. Micromechanical Origin of Particle Size Segregation

    NASA Astrophysics Data System (ADS)

    Jing, L.; Kwok, C. Y.; Leung, Y. F.

    2017-03-01

    We computationally study the micromechanics of shear-induced size segregation and propose distinct migration mechanisms for individual large and small particles. While small particles percolate through voids without enduring contacts, large particles climb under shear through their crowded neighborhoods with anisotropic contact network. Particle rotation associated with shear is necessary for the upward migration of large particles. Segregation of large particles can be suppressed with inadequate friction, or with no rotation; increasing interparticle friction promotes the migration of large particles, but has little effect on the percolation of small particles.

  8. Cumulative frequency fit for particle size distribution.

    PubMed

    Xu, Zhuyun; Gautam, Mridul; Mehta, Sandeep

    2002-08-01

    A cumulative frequency distribution fit method is presented for analyzing particle size distributions by minimizing the summation of the square of cumulative frequency errors. Compared to the frequency fit method, the cumulative frequency fit method yields a more accurate solution. Based upon this, a spreadsheet was developed for analyzing multi-modal particle size distribution. The motivation for the work presented in this article was the current interest in ultra-fine and nano-sized particle exhaust emissions from heavy-duty diesel engines. The new spreadsheet provides a quick and convenient way to conduct particle size distribution analysis.

  9. Method for producing size selected particles

    SciTech Connect

    Krumdick, Gregory K.; Shin, Young Ho; Takeya, Kaname

    2016-09-20

    The invention provides a system for preparing specific sized particles, the system comprising a continuous stir tank reactor adapted to receive reactants; a centrifugal dispenser positioned downstream from the reactor and in fluid communication with the reactor; a particle separator positioned downstream of the dispenser; and a solution stream return conduit positioned between the separator and the reactor. Also provided is a method for preparing specific sized particles, the method comprising introducing reagent into a continuous stir reaction tank and allowing the reagents to react to produce product liquor containing particles; contacting the liquor particles with a centrifugal force for a time sufficient to generate particles of a predetermined size and morphology; and returning unused reagents and particles of a non-predetermined size to the tank.

  10. Comparison of the Aerodynamic Characteristics of Similar Models in Two Size Wind Tunnels at Transonic Speeds

    NASA Technical Reports Server (NTRS)

    Springer, Anthony M.

    1998-01-01

    The aerodynamic characteristics of two similar models of a lifting body configuration were run in two transonic wind tunnels, one a 16 foot the other a 14-inch and are compared. The 16 foot test used a 2% model while the 14-inch test used a 0.7% scale model. The wind tunnel model configurations varied only in vertical tail size and an aft sting shroud. The results from these two tests compare the effect of tunnel size, Reynolds number, dynamic pressure and blockage on the longitudinal aerodynamic characteristics of the vehicle. The data accuracy and uncertainty are also presented. It was concluded from these tests that the data resultant from a small wind tunnel compares very well to that of a much larger wind tunnel in relation to total vehicle aerodynamic characteristics.

  11. Measurement of Size-dependent Dynamic Shape Factors of Quartz Particles in Two Flow Regimes

    SciTech Connect

    Alexander, Jennifer M.; Bell, David M.; Imre, D.; Kleiber, Paul; Grassian, Vicki H.; Zelenyuk, Alla

    2016-08-02

    Understanding and modeling the behavior of quartz dust particles, commonly found in the atmosphere, requires knowledge of many relevant particles properties, including particle shape. This study uses a single particle mass spectrometer, a differential mobility analyzer, and an aerosol particle mass analyzer to measure quartz aerosol particles mobility, aerodynamic, and volume equivalent diameters, mass, composition, effective density, and dynamic shape factor as a function of particle size, in both the free molecular and transition flow regimes. The results clearly demonstrate that dynamic shape factors can vary significantly as a function of particle size. For the quartz samples studied here, the dynamic shape factors increase with size, indicating that larger particles are significantly more aspherical than smaller particles. In addition, dynamic shape factors measured in the free-molecular (χv) and transition (χt) flow regimes can be significantly different, and these differences vary with the size of the quartz particles. For quartz, χv of small (d < 200 nm) particles is 1.25, while χv of larger particles (d ~ 440 nm) is 1.6, with a continuously increasing trend with particle size. In contrast χt, of small particles starts at 1.1 increasing slowly to 1.34 for 550 nm diameter particles. The multidimensional particle characterization approach used here goes beyond determination of average properties for each size, to provide additional information about how the particle dynamic shape factor may vary even for particles with the same mass and volume equivalent diameter.

  12. Industrial Particle Size Measurement Using Light Scattering

    NASA Astrophysics Data System (ADS)

    Muly, E. C.; Frock, H. N.

    1980-12-01

    The precise knowledge of particle size and particle size distribution is fundamental to the control of a wide variety of industrial processes. Processing steps as diverse as crystallization, grinding, emulsification, and atomization, produce particles in the size range .1 to 1000 micrometers in diameter. While the object of some processes may be the production of particles of specified sizes, e.g., abrasives and glass beads, other processes may require particle size control for process efficiency, e.g., crystallization, and still others for control of final product quality, e.g., minerals, cement, and ceramics. In many processes more than one of these reasons may be important. A line of instruments has been developed using light scattering to measure various parameters of particulate distributions. These instruments employ laser illumination of a flowing stream of particles, producing Fraunhofer diffraction patterns which are processed both optically and electronically with unique, proprietary techniques. Various parameters of the particle size distribution are measured. The measurement is both rapid and precise. This paper will cover the importance of particle size measurements in various processes, different types of measurement methods, and the application of light scattering technology to size determinations in wet slurries and dry powders. A number of specific applications will be discussed encompassing minerals grinding, Portland cement, and rolling mill emulsions. Some references will be made to energy savings through automation.

  13. Proposed international conventions for particle size-selective sampling.

    PubMed

    Soderholm, S C

    1989-01-01

    Definitions are proposed for the inspirable (also called inhalable), thoracic and respirable fractions of airborne particles. Each definition is expressed as a sampling efficiency (S) which is a function of particle aerodynamic diameter (d) and specifies the fraction of the ambient concentration of airborne particles collected by an ideal sampler. For the inspirable fraction. SI(d) = 0.5 (1 + e-0.06d). For the thoracic fraction, ST(d) = SI(d)[1 - F(x)], where (formula; see text) F(x) is the cumulative probability function of a standardized normal random variable. For the respirable fraction, SR(d) = SI(d)[1 - F(x)], where gamma = 4.25 microns, sigma = 1.5. International harmonization will require resolution of the differences between the firmly established BMRC [Orenstein, A. J. (1960) Proceedings of the Pneumoconiosis Conference, Johannesburg, 1959, pp. 610-621. A.J. Churchill Ltd, London] and ACGIH [(1985) Particle size-selective sampling in the workplace. Report of the ACGIH Technical Committee on Air Sampling Procedures] definitions of the respirable fraction. The proposed definition differs approximately equally from the BMRC and ACGIH definitions and is at least as defensible when compared to available human data. Several standard-setting organizations are in the process of adopting particle size-selective sampling conventions. Much confusion will be avoided if all adopt the same specifications of the collection efficiencies of ideal samplers, such as those proposed here.

  14. Constant size, variable density aerosol particles by ultrasonic spray freeze drying.

    PubMed

    D'Addio, Suzanne M; Chan, John Gar Yan; Kwok, Philip Chi Lip; Prud'homme, Robert K; Chan, Hak-Kim

    2012-05-10

    This work provides a new understanding of critical process parameters involved in the production of inhalation aerosol particles by ultrasonic spray freeze drying to enable precise control over particle size and aerodynamic properties. A series of highly porous mannitol, lysozyme, and bovine serum albumin (BSA) particles were produced, varying only the solute concentration in the liquid feed, c(s), from 1 to 5 wt%. The particle sizes of mannitol, BSA, and lysozyme powders were independent of solute concentration, and depend only on the drop size produced by atomization. Both mannitol and lysozyme formulations showed a linear relationship between the computed Fine Particle Fraction (FPF) and the square root of c(s), which is proportional to the particle density, ρ, given a constant particle size d(g). The FPF decreased with increasing c(s) from 57.0% to 16.6% for mannitol and 44.5% to 17.2% for lysozyme. Due to cohesion, the BSA powder FPF measured by cascade impaction was less than 10% and independent of c(s). Ultrasonic spray freeze drying enables separate control over particle size, d(g), and aerodynamic size, d(a) which has allowed us to make the first experimental demonstration of the widely accepted rule d(a)=d(g)(ρ/ρ(o))(1/2) with particles of constant d(g), but variable density, ρ (ρ(o) is unit density).

  15. APSAS; an Automated Particle Size Analysis System

    USGS Publications Warehouse

    Poppe, Lawrence J.; Eliason, A.H.; Fredericks, J.J.

    1985-01-01

    The Automated Particle Size Analysis System integrates a settling tube and an electroresistance multichannel particle-size analyzer (Coulter Counter) with a Pro-Comp/gg microcomputer and a Hewlett Packard 2100 MX(HP 2100 MX) minicomputer. This system and its associated software digitize the raw sediment grain-size data, combine the coarse- and fine-fraction data into complete grain-size distributions, perform method of moments and inclusive graphics statistics, verbally classify the sediment, generate histogram and cumulative frequency plots, and transfer the results into a data-retrieval system. This system saves time and labor and affords greater reliability, resolution, and reproducibility than conventional methods do.

  16. DESIGN AND EVALUATION OF AN INLET CONDITIONER TO DRY PARTICLES FOR AN AERODYNAMIC PARTICLE SIZER

    EPA Science Inventory

    Atmospheric particulate matter is one of six pollutants for which the Environmental Protection Agency (EPA) has set National Ambient Air Quality Standards. Particulate matter standards are specified by particle size as PM 2.5 defined as the mass concentration of ′fine...

  17. Size distributions of solar energetic particle events

    NASA Technical Reports Server (NTRS)

    Cliver, E.; Reames, D.; Kahler, S.; Cane, H.

    1991-01-01

    NASA particle detectors on the IMP-8 are employed to determine the size distributions of the peak fluxes of events related to solar-energetic particles including protons and electrons. The energetic proton events show a flatter size distribution which suggests that not all flares are proton flares. Both the electron and proton events are classified as either 'impulsive' or 'gradual', and the impulsive events tend to have a steeper power-law distribution.

  18. The complex aerodynamic footprint of desert locusts revealed by large-volume tomographic particle image velocimetry.

    PubMed

    Henningsson, Per; Michaelis, Dirk; Nakata, Toshiyuki; Schanz, Daniel; Geisler, Reinhard; Schröder, Andreas; Bomphrey, Richard J

    2015-07-06

    Particle image velocimetry has been the preferred experimental technique with which to study the aerodynamics of animal flight for over a decade. In that time, hardware has become more accessible and the software has progressed from the acquisition of planes through the flow field to the reconstruction of small volumetric measurements. Until now, it has not been possible to capture large volumes that incorporate the full wavelength of the aerodynamic track left behind during a complete wingbeat cycle. Here, we use a unique apparatus to acquire the first instantaneous wake volume of a flying animal's entire wingbeat. We confirm the presence of wake deformation behind desert locusts and quantify the effect of that deformation on estimates of aerodynamic force and the efficiency of lift generation. We present previously undescribed vortex wake phenomena, including entrainment around the wing-tip vortices of a set of secondary vortices borne of Kelvin-Helmholtz instability in the shear layer behind the flapping wings.

  19. The complex aerodynamic footprint of desert locusts revealed by large-volume tomographic particle image velocimetry

    PubMed Central

    Henningsson, Per; Michaelis, Dirk; Nakata, Toshiyuki; Schanz, Daniel; Geisler, Reinhard; Schröder, Andreas; Bomphrey, Richard J.

    2015-01-01

    Particle image velocimetry has been the preferred experimental technique with which to study the aerodynamics of animal flight for over a decade. In that time, hardware has become more accessible and the software has progressed from the acquisition of planes through the flow field to the reconstruction of small volumetric measurements. Until now, it has not been possible to capture large volumes that incorporate the full wavelength of the aerodynamic track left behind during a complete wingbeat cycle. Here, we use a unique apparatus to acquire the first instantaneous wake volume of a flying animal's entire wingbeat. We confirm the presence of wake deformation behind desert locusts and quantify the effect of that deformation on estimates of aerodynamic force and the efficiency of lift generation. We present previously undescribed vortex wake phenomena, including entrainment around the wing-tip vortices of a set of secondary vortices borne of Kelvin–Helmholtz instability in the shear layer behind the flapping wings. PMID:26040598

  20. Particle size-dependent radical generation from wildland fire smoke.

    PubMed

    Leonard, Stephen S; Castranova, Vince; Chen, Bean T; Schwegler-Berry, Diane; Hoover, Mark; Piacitelli, Chris; Gaughan, Denise M

    2007-07-01

    Firefighting, along with construction, mining and agriculture, ranks among the most dangerous occupations. In addition, the work environment of firefighters is unlike that of any other occupation, not only because of the obvious physical hazards but also due to the respiratory and systemic health hazards of smoke inhalation resulting from combustion. A significant amount of research has been devoted to studying municipal firefighters; however, these studies may not be useful in wildland firefighter exposures, because the two work environments are so different. Not only are wildland firefighters exposed to different combustion products, but their exposure profiles are different. The combustion products wildland firefighters are exposed to can vary greatly in characteristics due to the type and amount of material being burned, soil conditions, temperature and exposure time. Smoke inhalation is one of the greatest concerns for firefighter health and it has been shown that the smoke consists of a large number of particles. These smoke particles contain intermediates of hydrogen, carbon and oxygen free radicals, which may pose a potential health risk. Our investigation looked into the involvement of free radicals in smoke toxicity and the relationship between particle size and radical generation. Samples were collected in discrete aerodynamic particle sizes from a wildfire in Alaska, preserved and then shipped to our laboratory for analysis. Electron spin resonance was used to measure carbon-centered as well as hydroxyl radicals produced by a Fenton-like reaction with wildfire smoke. Further study of reactive oxygen species was conducted using analysis of cellular H(2)O(2) generation, lipid peroxidation of cellular membranes and DNA damage. Results demonstrate that coarse size-range particles contained more carbon radicals per unit mass than the ultrafine particles; however, the ultrafine particles generated more *OH radicals in the acellular Fenton-like reaction. The

  1. Hazards of explosives dusts: Particle size effects

    SciTech Connect

    Cashdollar, K L; Hertzberg, M; Green, G M

    1992-02-01

    At the request of the Department of Energy, the Bureau of Mines has investigated the hazards of military explosives dispersed as dust clouds in a 20-L test chamber. In this report, the effect of particle size for HMX, HNS, RDX, TATB, and TNT explosives dusts is studied in detail. The explosibility data for these dusts are also compared to those for pure fuel dusts. The data show that all of the sizes of the explosives dusts that were studied were capable of sustaining explosions as dust clouds dispersed in air. The finest sizes (<10 [mu]m) of explosives dusts were less reactive than the intermediate sizes (20 to 60 [mu]m); this is opposite to the particle size effect observed previously for the pure fuel dusts. At the largest sizes studied, the explosives dusts become somewhat less reactive as dispersed dust clouds. The six sizes of the HMX dust were also studied as dust clouds dispersed in nitrogen.

  2. Investigation of plasma particle interactions with variable particle sizes

    NASA Astrophysics Data System (ADS)

    Dropmann, Michael; Laufer, Rene; Herdrich, Georg; Matthews, Lorin; Hyde, Truell

    2015-11-01

    In dusty plasmas, the dust particles are subjected to many forces of different origins. Both the gas and plasma directly affect the dust particles through electric fields, neutral drag, ion drag and thermophoretic forces, while the particles themselves interact with one another through a screened coulomb potential, which can be influenced by flowing ions. Recently, micron sized particles have been used as probes to analyze the electric fields in the plasma directly. A proper analysis of the resulting data requires a full understanding of the manner in which these forces couple to the dust particles. In most cases each of the forces exhibit unique characteristics, many of which are partially dependent on the particle size. In this study, five different particle sizes are used to investigate the forces resident in the sheath above the lower electrode of a GEC RF reference cell. The particles are tracked using a high-speed camera, yielding two-dimensional force maps allowing the force on the particles to be described as a polynomial series. It will be shown that the data collected can be analyzed to reveal information about the origins of the various forces. Support from the NSF and the DOE (award numbers PHY-1262031 and PHY-1414523) is gratefully acknowledged.

  3. Sheathless Size-Based Acoustic Particle Separation

    PubMed Central

    Guldiken, Rasim; Jo, Myeong Chan; Gallant, Nathan D.; Demirci, Utkan; Zhe, Jiang

    2012-01-01

    Particle separation is of great interest in many biological and biomedical applications. Flow-based methods have been used to sort particles and cells. However, the main challenge with flow based particle separation systems is the need for a sheath flow for successful operation. Existence of the sheath liquid dilutes the analyte, necessitates precise flow control between sample and sheath flow, requires a complicated design to create sheath flow and separation efficiency depends on the sheath liquid composition. In this paper, we present a microfluidic platform for sheathless particle separation using standing surface acoustic waves. In this platform, particles are first lined up at the center of the channel without introducing any external sheath flow. The particles are then entered into the second stage where particles are driven towards the off-center pressure nodes for size based separation. The larger particles are exposed to more lateral displacement in the channel due to the acoustic force differences. Consequently, different-size particles are separated into multiple collection outlets. The prominent feature of the present microfluidic platform is that the device does not require the use of the sheath flow for positioning and aligning of particles. Instead, the sheathless flow focusing and separation are integrated within a single microfluidic device and accomplished simultaneously. In this paper, we demonstrated two different particle size-resolution separations; (1) 3 μm and 10 μm and (2) 3 μm and 5 μm. Also, the effects of the input power, the flow rate, and particle concentration on the separation efficiency were investigated. These technologies have potential to impact broadly various areas including the essential microfluidic components for lab-on-a-chip system and integrated biological and biomedical applications. PMID:22368502

  4. The techniques of holographic particle sizing

    NASA Technical Reports Server (NTRS)

    Kurtz, R. L.

    1973-01-01

    Depending on the mechanism of particle production, the resultant particle size and velocity distribution may range over several orders of magnitude. In general, if particle size information is desired from a given type generator, one must resort to some form of experimental determination of the distribution. If the source of particle production is a dynamic one involving a reasonable volume, holography provides a tailor-made particle size and velocity distribution detector. This is evidenced by the fact that holography allows the entire volume to be recorded on one exposure without any interference with the volume of interest. Herein lies a very important characteristic of the holographic particle detection technique: It provides a holographic nondestructive testing technique in the fullest sense of the definition of nondestructive testing. This report provides a description of three different systems useful in this technique and includes the experimental results from one of the holographic systems which was used to detect particle size and velocity distribution from the Skylab waste tank.

  5. Particle size distribution and particle size-related crystalline silica content in granite quarry dust.

    PubMed

    Sirianni, Greg; Hosgood, Howard Dean; Slade, Martin D; Borak, Jonathan

    2008-05-01

    Previous studies indicate that the relationship between empirically derived particle counts, particle mass determinations, and particle size-related silica content are not constant within mines or across mine work tasks. To better understand the variability of particle size distributions and variations in silica content by particle size in a granite quarry, exposure surveys were conducted with side-by-side arrays of four closed face cassettes, four cyclones, four personal environmental monitors, and a real-time particle counter. In general, the proportion of silica increased as collected particulate size increased, but samples varied in an inconstant way. Significant differences in particle size distributions were seen depending on the extent of ventilation and the nature and activity of work performed. Such variability raises concerns about the adequacy of silica exposure assessments based on only limited numbers of samples or short-term samples.

  6. Particle size distribution of indoor aerosol sources

    SciTech Connect

    Shah, K.B.

    1990-10-24

    As concern about Indoor Air Quality (IAQ) has grown in recent years, it has become necessary to determine the nature of particles produced by different indoor aerosol sources and the typical concentration that these sources tend to produce. These data are important in predicting the dose of particles to people exposed to these sources and it will also enable us to take effective mitigation procedures. Further, it will also help in designing appropriate air cleaners. A new state of the art technique, DMPS (Differential Mobility Particle Sizer) System is used to determine the particle size distributions of a number of sources. This system employs the electrical mobility characteristics of these particles and is very effective in the 0.01--1.0 {mu}m size range. A modified system that can measure particle sizes in the lower size range down to 3 nm was also used. Experimental results for various aerosol sources is presented in the ensuing chapters. 37 refs., 20 figs., 2 tabs.

  7. Measurement of nonvolatile particle number size distribution

    NASA Astrophysics Data System (ADS)

    Gkatzelis, G. I.; Papanastasiou, D. K.; Florou, K.; Kaltsonoudis, C.; Louvaris, E.; Pandis, S. N.

    2016-01-01

    An experimental methodology was developed to measure the nonvolatile particle number concentration using a thermodenuder (TD). The TD was coupled with a high-resolution time-of-flight aerosol mass spectrometer, measuring the chemical composition and mass size distribution of the submicrometer aerosol and a scanning mobility particle sizer (SMPS) that provided the number size distribution of the aerosol in the range from 10 to 500 nm. The method was evaluated with a set of smog chamber experiments and achieved almost complete evaporation (> 98 %) of secondary organic as well as freshly nucleated particles, using a TD temperature of 400 °C and a centerline residence time of 15 s. This experimental approach was applied in a winter field campaign in Athens and provided a direct measurement of number concentration and size distribution for particles emitted from major pollution sources. During periods in which the contribution of biomass burning sources was dominant, more than 80 % of particle number concentration remained after passing through the thermodenuder, suggesting that nearly all biomass burning particles had a nonvolatile core. These remaining particles consisted mostly of black carbon (60 % mass contribution) and organic aerosol (OA; 40 %). Organics that had not evaporated through the TD were mostly biomass burning OA (BBOA) and oxygenated OA (OOA) as determined from AMS source apportionment analysis. For periods during which traffic contribution was dominant 50-60 % of the particles had a nonvolatile core while the rest evaporated at 400 °C. The remaining particle mass consisted mostly of black carbon with an 80 % contribution, while OA was responsible for another 15-20 %. Organics were mostly hydrocarbon-like OA (HOA) and OOA. These results suggest that even at 400 °C some fraction of the OA does not evaporate from particles emitted from common combustion processes, such as biomass burning and car engines, indicating that a fraction of this type of OA

  8. Calibration of optical particle-size analyzer

    DOEpatents

    Pechin, William H.; Thacker, Louis H.; Turner, Lloyd J.

    1979-01-01

    This invention relates to a system for the calibration of an optical particle-size analyzer of the light-intercepting type for spherical particles, wherein a rotary wheel or disc is provided with radially-extending wires of differing diameters, each wire corresponding to a particular equivalent spherical particle diameter. These wires are passed at an appropriate frequency between the light source and the light detector of the analyzer. The reduction of light as received at the detector is a measure of the size of the wire, and the electronic signal may then be adjusted to provide the desired signal for corresponding spherical particles. This calibrator may be operated at any time without interrupting other processing.

  9. Particle Size Distributions in Atmospheric Clouds

    NASA Technical Reports Server (NTRS)

    Paoli, Roberto; Shariff, Karim

    2003-01-01

    In this note, we derive a transport equation for a spatially integrated distribution function of particles size that is suitable for sparse particle systems, such as in atmospheric clouds. This is done by integrating a Boltzmann equation for a (local) distribution function over an arbitrary but finite volume. A methodology for evolving the moments of the integrated distribution is presented. These moments can be either tracked for a finite number of discrete populations ('clusters') or treated as continuum variables.

  10. Electronic cigarette aerosol particle size distribution measurements.

    PubMed

    Ingebrethsen, Bradley J; Cole, Stephen K; Alderman, Steven L

    2012-12-01

    The particle size distribution of aerosols produced by electronic cigarettes was measured in an undiluted state by a spectral transmission procedure and after high dilution with an electrical mobility analyzer. The undiluted e-cigarette aerosols were found to have particle diameters of average mass in the 250-450 nm range and particle number concentrations in the 10(9) particles/cm(3) range. These measurements are comparable to those observed for tobacco burning cigarette smoke in prior studies and also measured in the current study with the spectral transmission method and with the electrical mobility procedure. Total particulate mass for the e-cigarettes calculated from the size distribution parameters measured by spectral transmission were in good agreement with replicate determinations of total particulate mass by gravimetric filter collection. In contrast, average particle diameters determined for e-cigarettes by the electrical mobility method are in the 50 nm range and total particulate masses calculated based on the suggested diameters are orders of magnitude smaller than those determined gravimetrically. This latter discrepancy, and the very small particle diameters observed, are believed to result from almost complete e-cigarette aerosol particle evaporation at the dilution levels and conditions of the electrical mobility analysis. A much smaller degree, ~20% by mass, of apparent particle evaporation was observed for tobacco burning cigarette smoke. The spectral transmission method is validated in the current study against measurements on tobacco burning cigarette smoke, which has been well characterized in prior studies, and is supported as yielding an accurate characterization of the e-cigarette aerosol particle size distribution.

  11. Cataclasis and processes of particle size reduction

    NASA Astrophysics Data System (ADS)

    Blenkinsop, Tom G.

    1991-05-01

    The particle size distribution (P.S.D.) of fragmented geological materials is affected by the fragmentation process, initial size distribution, number of fracturing events, energy input, strain, and confining pressure. A summary of literature shows that the fractal dimension ( D) of the P.S.D. is increased by the number of fracturing events, energy input, strain, and confining pressure. Cenozoic cataclasis of granite, granodiorites, gneisses and arkose seen in cores from the Cajon Pass drillhole, southern California, produced P.S.D.s with values of D that varied from 1.88 to 3.08. Each rock type has a characteristic and more limited range of D. Areas of dilatant texture and mode I fracture-fillings have low average values (2.32 and 2.37) compared to an average value of 2.67 in shear fracture-fillings D has a good inverse correlation with average particle size. Data from fault rocks in the San Gabriel fault zone, southern California ( Anderson et al., 1983) have been reanalyzed to show that values of D are higher (2.10 5.52) and average particle size is lower than the Cajon Pass samples, but the ranges of values overlap, and the inverse correlation between D and average particle size is extended. Microstructural observations combined with these results suggest that three processes contributed to particle size reduction during cataclasis. The first process of feldspar alteration, which leads to low values of D, has not been previously recognized. The second process is probably constrained comminution ( Sammis et al., 1987), since the average D in shear fracture-fillings is close to the value of 2.58 predicted by this theory. A further stage of particle size reduction is demonstrated by an increase of D with cataclasis. This third process is selective fracture of larger particles, which may also operate during localization and the cataclastic flow-to-faulting transition as observed in experiments. A transition from constrained comminution to selective fracture of

  12. Underlying Asymmetry with Particle-Size Segregation

    NASA Astrophysics Data System (ADS)

    Gajjar, Parmesh; van der Vaart, Kasper; Epely-Chauvin, Gael; Andreini, Nicolas; Gray, Nico; Ancey, Christophe

    2015-11-01

    Granular media have a natural tendency to self-organise when sheared, with different sized constituents counter-intuitively separating from each other. Not only does the segregation produce a rich diversity of beautiful patterns, but it can also have serious implications in both industrial and geophysical environments. Despite the universal importance, the individual particle dynamics during segregation are still poorly understand, with such an analysis proving to be difficult with conventional techniques such as binning and sidewall observation. This talk will present results of recent experiments that studied particle scale segregation dynamics during oscillatory shear. Refractive index matched scanning allowed examination of the interior of the flow, where it was observed that large and small particles have an underlying asymmetry that is dependant on the local particle concentration. Small particles were seen to segregate faster through regions of many large particles, whilst large particles rise slower through regions of many small particles. The asymmetry is quantified on both bulk and particle length scales, and is shown to have good agreement with a continuum model that uses a cubic segregation flux.

  13. Rock sampling. [apparatus for controlling particle size

    NASA Technical Reports Server (NTRS)

    Blum, P. (Inventor)

    1971-01-01

    An apparatus for sampling rock and other brittle materials and for controlling resultant particle sizes is described. The device includes grinding means for cutting grooves in the rock surface and to provide a grouping of thin, shallow, parallel ridges and cutter means to reduce these ridges to a powder specimen. Collection means is provided for the powder. The invention relates to rock grinding and particularly to the sampling of rock specimens with good size control.

  14. PARTICLE SIZE DISTRIBUTIONS FOR AN OFFICE AEROSOL

    EPA Science Inventory

    The article discusses an evaluation of the effect of percent outdoor air supplied and occupation level on the particle size distributions and mass concentrations for a typical office building. (NOTE: As attention has become focused on indoor air pollution control, it has become i...

  15. Analysis and evaluation of diesel particle size

    SciTech Connect

    Franke, H.U.; Klingenberg, H.

    1995-12-31

    The results of the investigations were presented at the 4th International Aerosol Conference in September 1994. These investigations are currently being carried out further. At this conference, it was reported that the particle size and its distribution increases while traveling through the exhaust system. Particularly, a larger increase was observed for particles passing through the catalytic converter. The goals of the continued work are: (1) to investigate the cause for the increase of the particle size in the catalytic converter and the influence of sulfur compounds, (2) to develop a method to determine the three - dimensional shape of the particles quantitatively, and (3) to look for methods to increase the particle diameter above the 10 {mu}m limit where they are not breathed into the lungs For these investigations a fourth sampling position behind the exhaust system was defined. Measurement was carried out by again using impactors a new computer controlled transmission electron microscope, and a new REM and a TM x 2000. A determination of the definite x, y, z values for the particles by a photogrametric evaluation of the electron microscope pictures taken from different angles. This allows the construction of the three - dimensional shapes. All the results will be reported.

  16. Remote Laser Diffraction Particle Size Distribution Analyzer

    SciTech Connect

    Batcheller, Thomas Aquinas; Huestis, Gary Michael; Bolton, Steven Michael

    2001-03-01

    In support of a radioactive slurry sampling and physical characterization task, an “off-the-shelf” laser diffraction (classical light scattering) particle size analyzer was utilized for remote particle size distribution (PSD) analysis. Spent nuclear fuel was previously reprocessed at the Idaho Nuclear Technology and Engineering Center (INTEC—formerly recognized as the Idaho Chemical Processing Plant) which is on DOE’s INEEL site. The acidic, radioactive aqueous raffinate streams from these processes were transferred to 300,000 gallon stainless steel storage vessels located in the INTEC Tank Farm area. Due to the transfer piping configuration in these vessels, complete removal of the liquid can not be achieved. Consequently, a “heel” slurry remains at the bottom of an “emptied” vessel. Particle size distribution characterization of the settled solids in this remaining heel slurry, as well as suspended solids in the tank liquid, is the goal of this remote PSD analyzer task. A Horiba Instruments Inc. Model LA-300 PSD analyzer, which has a 0.1 to 600 micron measurement range, was modified for remote application in a “hot cell” (gamma radiation) environment. This technology provides rapid and simple PSD analysis, especially down in the fine and microscopic particle size regime. Particle size analysis of these radioactive slurries down in this smaller range was not previously achievable—making this technology far superior than the traditional methods used. Successful acquisition of this data, in conjunction with other characterization analyses, provides important information that can be used in the myriad of potential radioactive waste management alternatives.

  17. Determining particle size distributions in the inhalable size range for wood dust collected by air samplers.

    PubMed

    Harper, Martin; Muller, Brian S; Bartolucci, Al

    2002-10-01

    In the absence of methods for determining particle size distributions in the inhalable size range with good discrimination, the samples collected by personal air sampling devices can only be characterized by their total mass. This parameter gives no information regarding the size distribution of the aerosol or the size-selection characteristics of different samplers in field use conditions. A method is described where the particles collected by a sampler are removed, suspended, and re-deposited on a mixed cellulose-ester filter, and examined by optical microscopy to determine particle aerodynamic diameters. This method is particularly appropriate to wood dust particles which are generally large and close to rectangular prisms in shape. Over 200 wood dust samples have been collected in three different wood-products industries, using the traditional closed-face polystyrene/acrylonitrile cassette, the Institute of Occupational Medicine inhalable sampler, and the Button sampler developed by the University of Cincinnati. A portion of these samples has been analyzed to determine the limitations of this method. Extensive quality control measures are being developed to improve the robustness of the procedure, and preliminary results suggest the method has an accuracy similar to that required of National Institute for Occupational Safety and Health (NIOSH) methods. The results should provide valuable insights into the collection characteristics of the samplers and the impact of these characteristics on comparison of sampler results to present and potential future limit values. The NIOSH Deep South Education and Research Center has a focus on research into hazards of the forestry and associated wood-products industry, and it is hoped to expand this activity in the future.

  18. Physicochemical characterization of Capstone depleted uranium aerosols II: particle size distributions as a function of time.

    PubMed

    Cheng, Yung Sung; Kenoyer, Judson L; Guilmette, Raymond A; Parkhurst, Mary Ann

    2009-03-01

    The Capstone Depleted Uranium (DU) Aerosol Study, which generated and characterized aerosols containing DU from perforation of armored vehicles with large-caliber DU penetrators, incorporated a sampling protocol to evaluate particle size distributions. Aerosol particle size distribution is an important parameter that influences aerosol transport and deposition processes as well as the dosimetry of the inhaled particles. These aerosols were collected on cascade impactor substrates using a pre-established time sequence following the firing event to analyze the uranium concentration and particle size of the aerosols as a function of time. The impactor substrates were analyzed using proportional counting, and the derived uranium content of each served as input to the evaluation of particle size distributions. Activity median aerodynamic diameters (AMADs) of the particle size distributions were evaluated using unimodal and bimodal models. The particle size data from the impactor measurements were quite variable. Most size distributions measured in the test based on activity had bimodal size distributions with a small particle size mode in the range of between 0.2 and 1.2 microm and a large size mode between 2 and 15 microm. In general, the evolution of particle size over time showed an overall decrease of average particle size from AMADs of 5 to 10 microm shortly after perforation to around 1 microm at the end of the 2-h sampling period. The AMADs generally decreased over time because of settling. Additionally, the median diameter of the larger size mode decreased with time. These results were used to estimate the dosimetry of inhaled DU particles.

  19. Physicochemical Characterization of Capstone Depleted Uranium Aerosols II: Particle Size Distributions as a Function of Time

    SciTech Connect

    Cheng, Yung-Sung; Kenoyer, Judson L.; Guilmette, Raymond A.; Parkhurst, MaryAnn

    2009-03-01

    The Capstone Depleted Uranium (DU) Aerosol Study, which generated and characterized aerosols containing depleted uranium from perforation of armored vehicles with large-caliber DU penetrators, incorporated a sampling protocol to evaluated particle size distributions. Aerosol particle size distribution is an important parameter that influences aerosol transport and deposition processes as well as the dosimetry of the inhaled particles. These aerosols were collected on cascade impactor substrates using a pre-established time sequence following the firing event to analyze the uranium concentration and particle size of the aerosols as a function of time. The impactor substrates were analyzed using beta spectrometry, and the derived uranium content of each served as input to the evaluation of particle size distributions. Activity median aerodynamic diameters (AMADs) of the particle size distributions were evaluated using unimodal and bimodal models. The particle size data from the impactor measurements was quite variable. Most size distributions measured in the test based on activity had bimodal size distributions with a small particle size mode in the range of between 0.2 and 1.2 um and a large size mode between 2 and 15 um. In general, the evolution of particle size over time showed an overall decrease of average particle size from AMADs of 5 to 10 um shortly after perforation to around 1 um at the end of the 2-hr sampling period. The AMADs generally decreased over time because of settling. Additionally, the median diameter of the larger size mode decreased with time. These results were used to estimate the dosimetry of inhaled DU particles.

  20. Photographic techniques for characterizing streambed particle sizes

    USGS Publications Warehouse

    Whitman, M.S.; Moran, E.H.; Ourso, R.T.

    2003-01-01

    We developed photographic techniques to characterize coarse (>2-mm) and fine (???2-mm) streambed particle sizes in 12 streams in Anchorage, Alaska. Results were compared with current sampling techniques to assess which provided greater sampling efficiency and accuracy. The streams sampled were wade-able and contained gravel - cobble streambeds. Gradients ranged from about 5% at the upstream sites to about 0.25% at the downstream sites. Mean particle sizes and size-frequency distributions resulting from digitized photographs differed significantly from those resulting from Wolman pebble counts for five sites in the analysis. Wolman counts were biased toward selecting larger particles. Photographic analysis also yielded a greater number of measured particles (mean = 989) than did the Wolman counts (mean = 328). Stream embeddedness ratings assigned from field and photographic observations were significantly different at 5 of the 12 sites, although both types of ratings showed a positive relationship with digitized surface fines. Visual estimates of embeddedness and digitized surface fines may both be useful indicators of benthic conditions, but digitizing surface fines produces quantitative rather than qualitative data. Benefits of the photographic techniques include reduced field time, minimal streambed disturbance, convenience of postfield processing, easy sample archiving, and improved accuracy and replication potential.

  1. The Effect of Aerodynamic Heating on Air Penetration by Shaped Charge Jets and Their Particles

    NASA Astrophysics Data System (ADS)

    Backofen, Joseph

    2009-06-01

    The goal of this paper is to present recent work modeling thermal coupling between shaped charge jets and their particles with air while it is being penetrated to form a crater that subsequently collapses back onto the jet. This work complements research published at International Symposia on Ballistics: 1) 1987 - Shaped Charge Jet Aerodynamics, Particulation and Blast Field Modeling; and 2) 2007 - Air Cratering by Eroding Shaped Charge Jets. The current work shows how and when a shaped charge jet's tip and jet particles are softened enough that they can erode in a hydrodynamic manner as modeled in these papers. This paper and its presentation includes models for heat transfer from shocked air as a function of jet velocity as well as heat flow within the jet or particle. The work is supported by an extensive bibliographic search including publications on meteors and ballistic missile re-entry vehicles. The modeling shows that a jet loses its strength to the depth required to justify hydrodynamic erosion when its velocity is above a specific velocity related to the shock properties of air and the jet material's properties. As a result, the portion of a jet's kinetic energy converted at the aerodynamic shock into heating transferred back onto the jet affects the energy deposited into the air through drag and ablation which in turn affect air crater expansion and subsequent collapse back onto the jet and its particles as shown in high-speed photography.

  2. Particle size and shape of calcium hydroxide

    PubMed Central

    Komabayashi, Takashi; D’souza, Rena N; Dechow, Paul C; Safavi, Kamran E.; Spångberg, Larz S.W.

    2009-01-01

    The aim of this study was to examine the particle length, width, perimeter, and aspect ratio of calcium hydroxide powder using a flow particle image analyzer (FPIA). Five sample groups each with 10mg calcium hydroxide were mixed with 15mL of alcohol and sonicated. Digital images of the particle samples were taken using the FPIA and analyzed with a one-way ANOVA. The overall averages±S.D. among the five groups for particle length (μm), width (μm), perimeter (μm), and aspect ratio were 2.255±1.994, 1.620±1.464, 6.699±5.598, and 0.737±0.149, respectively. No statistical significance was observed among the groups for all parameters. When the total of 46,818 particles from all five groups were classified into the five length categories of 0.5μm increments, there were significant differences in width, perimeter, and aspect ratio (all p-values<0.0001). In conclusion, calcium hydroxide particles have a size and shape that may allow direct penetration into open dentin tubules. PMID:19166791

  3. Particle size statistics in dynamic fragmentation

    SciTech Connect

    Grady, D.E. )

    1990-12-15

    Condensed matter, when subjected to intense disrupting forces through impact or radiation deposition, will break up into a randomly distributed array of fragments. An earlier analysis of random fragmentation is extended to account for fragmentation in bodies which are finite in extent and for bodies within which the minimum fragment size is bounded. The statistical fragment size relations are compared with molecular dynamic simulations of dynamic fragmentation, with fragmentation caused by the high-energy collision of nuclear particles, and with the distribution of galaxies in the universe which are assumed to be fragment debris from the primordial Big Bang.

  4. Colloid particle size-dependent dispersivity

    NASA Astrophysics Data System (ADS)

    Chrysikopoulos, C. V.; Katzourakis, V. E.

    2014-12-01

    Laboratory and field studies have demonstrated that dispersion coefficients evaluated by fitting advection-dispersion transport models to nonreactive tracer breakthrough curves do not adequately describe colloid transport under the same flow field conditions. Here an extensive laboratory study was undertaken to assess whether the dispersivity, which traditionally has been considered to be a property of the porous medium, is dependent on colloid particle size and interstitial velocity. A total of 49 colloid transport experiments were performed in columns packed with glass beads under chemically unfavorable colloid attachment conditions. Nine different colloid diameters, and various flow velocities were examined. The breakthrough curves were successfully simulated with a mathematical model describing colloid transport in homogeneous, water saturated porous media. The results demonstrated that the dispersivity is positively correlated with colloid particle size, and increases with increasing velocity.

  5. Method of producing non-agglomerating submicron size particles

    DOEpatents

    Bourne, Roy S.; Eichman, Clarence C.; Welbon, William W.

    1989-01-01

    Submicron size particles are produced by using a sputtering process to deposit particles into a liquid. The liquid is processed to recover the particles therefrom, and the particles have sizes in the range of twenty to two hundred Angstroms. Either metallic or non-metallic particles can be produced, and the metallic particles can be used in "metallic inks".

  6. Method of producing submicron size particles and product produced thereby

    DOEpatents

    Bourne, R.S.; Eichman, C.C.; Welbon, W.W.

    1988-05-11

    Submicron size particles are produced by using a sputtering process to deposit particles into a liquid. The liquid is processed to recover the particles therefrom, and the particles have sizes in the range of twenty to two hundred Angstroms. Either metallic or non-metallic particles can be produced, and the metallic particles can be used in ''metallic inks.'' 4 figs.

  7. Synthesis and magnetorheology of suspensions of submicron-sized cobalt particles with tunable particle size

    NASA Astrophysics Data System (ADS)

    López-López, M. T.; Kuzhir, P.; Meunier, A.; Bossis, G.

    2010-08-01

    Different samples of cobalt powder were synthesized. Particle size and shape were characterized using electron microscopy and light scattering. These measurements showed that the synthesized powders consisted of monodisperse spheres with average diameters ranging between 63 and 760 nm. These powders were used for the preparation of magnetorheological (MR) fluids by dispersing them in silicone oil. The MR properties of these MR fluids were investigated. It was found that particle size did not have much influence on the MR response of MR fluids, for average particle diameters larger than 100 nm. On the other hand, the MR response decreased appreciably when the average particle diameter was diminished below 100 nm a theory based on the change of the shape of the aggregates with the size of the particles could explain these observations.

  8. Particle Size Distributions in Atmospheric Clouds

    DTIC Science & Technology

    2003-12-01

    UNCLASSIFIED Center for Turbulence Research 39 Annual Research Briefs 2003 Particle size distributions in atmospheric clouds By Roberto Paoli & Karim...atmospheric turbulence is an important, though complex, problem in cloud physics ( Shaw 2003). From a computational point of view, two major factors...contribute to this complexity. First is the very high turbulence Reynolds number and the large range of spatial scales (Vaillancourt & Yau 2000; Shaw 2003

  9. Modelling complete particle-size distributions from operator estimates of particle-size

    NASA Astrophysics Data System (ADS)

    Roberson, Sam; Weltje, Gert Jan

    2014-05-01

    Estimates of particle-size made by operators in the field and laboratory represent a vast and relatively untapped data archive. The wide spatial distribution of particle-size estimates makes them ideal for constructing geological models and soil maps. This study uses a large data set from the Netherlands (n = 4837) containing both operator estimates of particle size and complete particle-size distributions measured by laser granulometry. This study introduces a logit-based constrained-cubic-spline (CCS) algorithm to interpolate complete particle-size distributions from operator estimates. The CCS model is compared to four other models: (i) a linear interpolation; (ii) a log-hyperbolic interpolation; (iii) an empirical logistic function; and (iv) an empirical arctan function. Operator estimates were found to be both inaccurate and imprecise; only 14% of samples were successfully classified using the Dutch classification scheme for fine sediment. Operator estimates of sediment particle-size encompass the same range of values as particle-size distributions measured by laser analysis. However, the distributions measured by laser analysis show that most of the sand percentage values lie between zero and one, so the majority of the variability in the data is lost because operator estimates are made to the nearest 1% at best, and more frequently to the nearest 5%. A method for constructing complete particle-size distributions from operator estimates of sediment texture using a logit constrained cubit spline (CCS) interpolation algorithm is presented. This model and four other previously published methods are compared to establish the best approach to modelling particle-size distributions. The logit-CCS model is the most accurate method, although both logit-linear and log-linear interpolation models provide reasonable alternatives. Models based on empirical distribution functions are less accurate than interpolation algorithms for modelling particle-size distributions in

  10. Method for determining aerosol particle size, device for determining aerosol particle size

    SciTech Connect

    Novick, Vincent J.

    1997-12-01

    A method for determining the mass median diameter D of particles contained in a fluid is provided wherein the data of the mass of a pre-exposed and then a post-exposed filter is mathematically combined with data concerning the pressure differential across the same filter before and then after exposure to a particle-laden stream. A device for measuring particle size is also provided wherein the device utilizes the above-method for mathematically combining the easily quantifiable data.

  11. Chaotic mixing of finite-sized particles

    NASA Astrophysics Data System (ADS)

    Omurtag, Ahmet Can

    1997-10-01

    Dynamical systems concepts have been used to analyze the behavior of rigid spherical finite-sized particles in chaotic flows in the eccentric annular system. If the particles are sufficiently small they follow the fluid streamlines. Then the dynamical system is Hamiltonian as a result of the presence of a streamfunction for the two- dimensional incompressible flow. The Stokes number characterizes the significance of particle inertia. It is shown that the bifurcations of the dynamical system can be harnessed for separating particles with different physical properties. These results are numerically obtained for finite-sized particles in Stokes flows. Departure from Stokes flow toward higher Reynolds numbers results in longer transients in the fluid velocity field. It also changes the steady state pattern of the streamlines. Mixing under chaotic stirring procedures with up to Re=100 indicates a general tendency toward poorer mixing per cycle. Results obtained by the numerically generated fluid velocity field demonstrated good agreement with experimental results. The extent and shape of the chaotic regions are not, in general, radically modified as the Reynolds number increases. It was shown that the unstable manifolds of the underlying mapping based on Stokes flow provides a template for deformations in the flow even beyond the Stokes regime as well as with particle inertia and q/not=1. It was also shown that the stable and unstable manifolds can be located by calculating the finite-time Lyapunov exponents of a very large number of trajectories in the domain. Mixing in the eccentric annulus is applied to the problem of collecting fetal cells from maternal circulation of blood. Fetal cells were modeled as small spherical particles suspended in a Newtonian fluid filling the gap in a small eccentric annular mixing device. Two separate model collecting devices are used. The first model utilizes vertically placed and antibody coated fibers that adhere to fetal cells on

  12. Initial size distributions and hygroscopicity of indoor combustion aerosol particles

    SciTech Connect

    Li, W.; Hopke, P.K.

    1993-10-01

    Cigarette smoke, incense smoke, natural gas flames, propane fuel flames, and candle flames are contributors of indoor aerosol particles. To provide a quantitative basis for the modeling of inhaled aerosol deposition pattern, the hygroscopic growth of particles from these five sources as well as the source size distributions were measured. Because the experiments were performed on the bases of particles of single size, it provided not only the averaged particle`s hygroscopic growth of each source, but also the detailed size change for particles of different sizes within the whole size spectrum. The source particle size distribution measurements found that cigarette smoke and incense smoke contained particles in the size range of 100-700 nm, while the natural gas, propane, and candle flames generated particles between 10 and 100 nm. The hygroscopic growth experiments showed that these combustion aerosol particles could grow 10% to 120%, depending on the particle sizes and origins. 18 refs., 15 figs., 3 tabs.

  13. Particle-size analysis of pharmaceutical powders.

    PubMed

    Beaubien, L J; Vanderwielen, A J

    1980-06-01

    An automated electrolytic sensing zone (electrozone) method was developed to determine the particle-size distribution of milled and micronized pharmaceutical powders. The powdered drugs obeyed log-normal statistics, and the distributions were well defined by thier geometric volume mean diameter and the geometric standard deviation. The results show that accurate data can be obtained between 2 and 80 micron with a precision of approximately 0.5 micron. Pulse-width analyses were performed to determine the feasibility of using a pulse-width discrimination program. However, in this case, the program discriminates against real particles and, therefore, its usefulness is limited. Milled and micronized materials are described adequately by a spherical diameter, and the automated electrozone system described is an excellent method for quality control purposes.

  14. Spatial Variability of CCN Sized Aerosol Particles

    NASA Astrophysics Data System (ADS)

    Asmi, A.; Väänänen, R.

    2014-12-01

    The computational limitations restrict the grid size used in GCM models, and for many cloud types they are too large when compared to the scale of the cloud formation processes. Several parameterizations for e.g. convective cloud formation exist, but information on spatial subgrid variation of the cloud condensation nuclei (CCNs) sized aerosol concentration is not known. We quantify this variation as a function of the spatial scale by using datasets from airborne aerosol measurement campaigns around the world including EUCAARI LONGREX, ATAR, INCA, INDOEX, CLAIRE, PEGASOS and several regional airborne campaigns in Finland. The typical shapes of the distributions are analyzed. When possible, we use information obtained by CCN counters. In some other cases, we use particle size distribution measured by for example SMPS to get approximated CCN concentration. Other instruments used include optical particle counters or condensational particle counters. When using the GCM models, the CCN concentration used for each the grid-box is often considered to be either flat, or as an arithmetic mean of the concentration inside the grid-box. However, the aircraft data shows that the concentration values are often lognormal distributed. This, combined with the subgrid variations in the land use and atmospheric properties, might cause that the aerosol-cloud interactions calculated by using mean values to vary significantly from the true effects both temporary and spatially. This, in turn, can cause non-linear bias into the GCMs. We calculate the CCN aerosol concentration distribution as a function of different spatial scales. The measurements allow us to study the variation of these distributions within from hundreds of meters up to hundreds of kilometers. This is used to quantify the potential error when mean values are used in GCMs.

  15. Aerodynamic sizing of metered dose inhalers: an evaluation of the Andersen and Next Generation pharmaceutical impactors and their USP methods.

    PubMed

    Kamiya, Akihiko; Sakagami, Masahiro; Hindle, Michael; Byron, Peter R

    2004-07-01

    The particle sizing performance of a Next Generation Pharmaceutical Impactor (NGI) was compared to that of an Andersen cascade impactor (ACI). A single lot of Vanceril MDIs containing beclomethasone dipropionate (BDP) was used throughout. MDIs were sampled into NGI and ACI in accordance with USP recommendations, at 30.0 and 28.3 L/min, respectively, following 1, 2, 6, and 30 actuations with or without a silicone cup or stage coating, to determine the apparent particle size distributions (PSD) of BDP. The mass balance and the statistical comparability of drug deposits were assured on a "per actuation basis" across all experiments, demonstrating "good cascade impactor practices." Interstage deposition or "wall losses" in NGI were found to be lower than those in ACI, although their determination was laborious in NGI. The PSD profiles for Vanceril from a single actuation were distinguishable between NGI and ACI, when uncoated collection surfaces were used, most specifically for drug mass <4-microm aerodynamic diameter (p < 0.05). Silicone coating of collection surfaces and an increased number of actuations were shown to result in PSD profile shifts for both NGI and ACI. Such effects were most pronounced for NGI, although coating the collection surfaces and/or increasing the number of actuations improved drug retention significantly on the upper stages of NGI, and thereby, minimized the effects of particle bounce of BDP from Vanceril MDIs. PSD profiles from a single actuation could be determined reliably in either of these impactors, provided that coated collection surfaces were employed; also, cumulative % mass undersize profiles were similar between instruments. However, small differences in PSD profiles still existed to support NGI's design claims for reduced "overlap" in its stage collection efficiency curves.

  16. Comparative measurements using different particle size instruments

    NASA Technical Reports Server (NTRS)

    Chigier, N.

    1984-01-01

    This paper discusses the measurement and comparison of particle size and velocity measurements in sprays. The general nature of sprays and the development of standard, consistent research sprays are described. The instruments considered in this paper are: pulsed laser photography, holography, television, and cinematography; laser anemometry and interferometry using visibility, peak amplitude, and intensity ratioing; and laser diffraction. Calibration is by graticule, reticle, powders with known size distributions in liquid cells, monosize sprays, and, eventually, standard sprays. Statistical analyses including spatial and temporal long-time averaging as well as high-frequency response time histories with conditional sampling are examined. Previous attempts at comparing instruments, the making of simultaneous or consecutive measurements with similar types and different types of imaging, interferometric, and diffraction instruments are reviewed. A program of calibration and experiments for comparing and assessing different instruments is presented.

  17. Adhesion as an interplay between particle size and surface roughness.

    PubMed

    Katainen, J; Paajanen, M; Ahtola, E; Pore, V; Lahtinen, J

    2006-12-15

    Surface roughness plays an important role in the adhesion of small particles. In this paper we have investigated adhesion as a geometrical effect taking into account both the particle size and the size of the surface features. Adhesion is studied using blunt model particles on surfaces up to 10 nm root-mean-square (RMS) roughness. Measurements with particles both smaller and larger than surface features are presented. Results indicate different behavior in these areas. Adhesion of particles smaller than or similar in size to the asperities depend mainly on the size and shape of the asperities and only weakly on the size of the particle. For large particles also the particle size has a significant effect on the adhesion. A new model, which takes the relative size of particles and asperities into account, is also derived and compared to the experimental data. The proposed model predicts adhesion well over a wide range of particle/asperity length scales.

  18. Weak size dependence of resuspended radiocesium adsorbed on soil particles collected after the Fukushima nuclear accident.

    PubMed

    Kaneyasu, Naoki; Ohashi, Hideo; Suzuki, Fumie; Okuda, Tomoaki; Ikemori, Fumikazu; Akata, Naofumi; Kogure, Toshihiro

    2017-03-24

    Most studies of the properties of airborne radionuclides emitted from the Fukushima Daiichi Nuclear Power Plant have focused on the relatively early stages of the accident, and little is known about the characteristics of radiocesium in the long-term. In this study, we analyzed activity size distributions of airborne radiocesium collected over 5 months in Tsukuba, Japan. Radiocesium in the accumulation mode size range (0.1-2 μm in aerodynamic diameter) was overwhelming in the early aerosol samples and decreased with time, while that associated with coarse aerosols remained airborne. We examined the radiocesium adsorbed onto airborne soil particles, and found that the size dependence of (137)Cs surface density adsorbed on soil particles was weak. That is, radiocesium was distributed homogeneously throughout the aerodynamic diameter range of 2.1-11 μm. This characteristic may be related to the reported structure of radiocesium-bearing soil particles collected from the ground, which consisted of an aggregate of specific clay minerals and other non-cesium adsorbing particles. The resuspension factors for the first two aerosol samples collected during late April and May 2011 were close to those in European cities in the months following the Chernobyl accident, despite different soil and weather conditions.

  19. Source apportionment of ambient fine particle size distribution using positive matrix factorization in Erfurt, Germany

    PubMed Central

    Yue, Wei; Stölzel, Matthias; Cyrys, Josef; Pitz, Mike; Heinrich, Joachim; Kreyling, Wolfgang G.; Wichmann, H.-Erich; Peters, Annette; Wang, Sheng; Hopke, Philip K.

    2008-01-01

    Particle size distribution data collected between September 1997 and August 2001 in Erfurt, Germany were used to investigate the sources of ambient particulate matter by positive matrix factorization (PMF). A total of 29,313 hourly averaged particle size distribution measurements covering the size range of 0.01 to 3.0 μm were included in the analysis. The particle number concentrations (cm−3) for the 9 channels in the ultrafine range, and mass concentrations (ng m−3) for the 41 size bins in the accumulation mode and particle up to 3 μm in aerodynamic diameter were used in the PMF. The analysis was performed separately for each season. Additional analyses were performed including calculations of the correlations of factor contributions with gaseous pollutants (O3, NO, NO2, CO and SO2) and particle composition data (sulfate, organic carbon and elemental carbon), estimating the contributions of each factor to the total number and mass concentration, identifying the directional locations of the sources using the conditional probability function, and examining the diurnal patterns of factor scores. These results were used to assist in the interpretation of the factors. Five factors representing particles from airborne soil, ultrafine particles from local traffic, secondary aerosols from local fuel combustion, particles from remote traffic sources, and secondary aerosols from multiple sources were identified in all seasons. PMID:18433834

  20. Size-resolved source apportionment of airborne particle mass in a roadside environment.

    PubMed

    Riddle, Sarah G; Robert, Michael A; Jakober, Chris A; Hannigan, Michael P; Kleeman, Michael J

    2008-09-01

    Airborne particulate hopanes, steranes, and polycyclic aromatic hydrocarbons (PAHs) were measured in six size fractions < 1.8 microm particle diameter at one site upwind and two sites downwind of the Interstate 5 freeway in San Diego, CA. The smallest size fraction collected was exclusively in the ultrafine size range (D(p) < 0.1 microm; PM0.1). Size distributions of hopanes, steranes, and PAHs peaked between 0.10-0.18 microm particle aerodynamic diameter with a tail extending into the PM0.1 size range. This pattern is similar to previous dynamometer studies of hopane, sterane, and PAH size distributions emitted from gasoline- and diesel-powered vehicles. Size-resolved source profiles were combined to form an "on-road" profile for motor oil, diesel, and gasoline contributions to EC and OC. The resulting equations were used to predict source contributions to the size distributions of EC and OC in the roadside environment. The method successfully accounted for the majority of the carbonaceous material in particles with diameter < 0.18 microm, with significant residual material in larger size fractions. The peak in both the measured and predicted EC size distribution occurred between 0.1-0.18 microm particle aerodynamic diameter. The predicted OC size distribution peaked between 0.1-0.18 microm particle diameter, butthe measured OC size distribution peaked between 0.56-1.0 microm particle diameter, possibly because of secondary organic aerosol formation. Predicted OC concentrations in particles with diameter < 0.18 microm were greater than measured values 18 m downwind of the roadway but showed good agreement 37 m downwind. The largest source contributions to the PM0.1 and PM0.18 size fractions were different. PM0.18 was dominated by diesel fuel and motor oil combustion products while PM0.1 was dominated by diesel fuel and gasoline fuel combustion products. Total source contributions to ultrafine (PM0.1) EC concentrations 37 m downwind of the roadway were 44 +/- 6

  1. Characterizing Particle Size Distributions of Crystalline Silica in Gold Mine Dust

    PubMed Central

    Chubb, Lauren G.; Cauda, Emanuele G.

    2017-01-01

    Dust containing crystalline silica is common in mining environments in the U.S. and around the world. The exposure to respirable crystalline silica remains an important occupational issue and it can lead to the development of silicosis and other respiratory diseases. Little has been done with regard to the characterization of the crystalline silica content of specific particle sizes of mine-generated dust. Such characterization could improve monitoring techniques and control technologies for crystalline silica, decreasing worker exposure to silica and preventing future incidence of silicosis. Three gold mine dust samples were aerosolized in a laboratory chamber. Particle size-specific samples were collected for gravimetric analysis and for quantification of silica using the Microorifice Uniform Deposit Impactor (MOUDI). Dust size distributions were characterized via aerodynamic and scanning mobility particle sizers (APS, SMPS) and gravimetrically via the MOUDI. Silica size distributions were constructed using gravimetric data from the MOUDI and proportional silica content corresponding to each size range of particles collected by the MOUDI, as determined via X-ray diffraction and infrared spectroscopic quantification of silica. Results indicate that silica does not comprise a uniform proportion of total dust across all particle sizes and that the size distributions of a given dust and its silica component are similar but not equivalent. Additional research characterizing the silica content of dusts from a variety of mine types and other occupational environments is necessary in order to ascertain trends that could be beneficial in developing better monitoring and control strategies. PMID:28217139

  2. The determination and optimization of (rutile) pigment particle size distributions

    NASA Technical Reports Server (NTRS)

    Richards, L. W.

    1972-01-01

    A light scattering particle size test which can be used with materials having a broad particle size distribution is described. This test is useful for pigments. The relation between the particle size distribution of a rutile pigment and its optical performance in a gray tint test at low pigment concentration is calculated and compared with experimental data.

  3. Monodisperse Block Copolymer Particles with Controllable Size, Shape, and Nanostructure

    NASA Astrophysics Data System (ADS)

    Shin, Jae Man; Kim, Yongjoo; Kim, Bumjoon; PNEL Team

    Shape-anisotropic particles are important class of novel colloidal building block for their functionality is more strongly governed by their shape, size and nanostructure compared to conventional spherical particles. Recently, facile strategy for producing non-spherical polymeric particles by interfacial engineering received significant attention. However, achieving uniform size distribution of particles together with controlled shape and nanostructure has not been achieved. Here, we introduce versatile system for producing monodisperse BCP particles with controlled size, shape and morphology. Polystyrene-b-polybutadiene (PS-b-PB) self-assembled to either onion-like or striped ellipsoid particle, where final structure is governed by amount of adsorbed sodium dodecyl sulfate (SDS) surfactant at the particle/surrounding interface. Further control of molecular weight and particle size enabled fine-tuning of aspect ratio of ellipsoid particle. Underlying physics of free energy for morphology formation and entropic penalty associated with bending BCP chains strongly affects particle structure and specification.

  4. The particle size magnifier closing the gap between measurement of molecules, molecular clusters and aerosol particles

    NASA Astrophysics Data System (ADS)

    Mikkilä, Jyri; Lehtipalo, Katrianne; Kangasluoma, Juha; Franchin, Alessandro; Sipilä, Mikko; Jokinen, Tuija; Sarnela, Nina; Schobesberger, Siegfried; Junninen, Heikki; Kulmala, Markku; Worsnop, Douglas; Petäjä, Tuukka

    2013-05-01

    The Particle Size Magnifier lowers the cut-off size of a Condensation Particle Counter even down to about 1 nm in mobility diameter. By scanning the supersaturation also size information of the particles can be gained. We demonstrated that the PSM can detect particles starting from molecular sizes. By combining the data with newly developed mass spectrometric methods particle formation and growth can be followed molecule by molecule.

  5. Permeability of packed coal beds: The effect of particle size distribution, particle size and coal type

    SciTech Connect

    Greeff, S.C.; Slaghuis, J.H.; Walt, T.J. van der

    1998-12-31

    Sasol operates 97 Lurgi type gasifiers for the production of syngas using lump coal obtained from 7 captive coal mines. Permeability of packed coal beds of the coal has been identified as one of the major variables affecting stable operation which in turn affects maximum coal throughput and gas production. A tenth scale instrumented cold perspex model simulating a gasifier was constructed in which the pressure drop per unit bed length for a given gas flow could be measured. The effect of particle size distribution, particle size and coal type on the pressure drop (and hence permeability) was measured. The results were augmented by measuring void fractions as well as shape factors for the different coal types. The effect of size segregation during filling of the scale model was also investigated. Results have shown that bed permeability is strongly affected by the 3 variables investigated. The change in void fraction was found to be very small and could not be linked to the change in permeability. Size segregation resulted in a difference in gas flow rate between the center of the coal bed and against the wall of the model. The significance of the observations are discussed in terms of gasifier stability, optimum pressure drop and the effect of thermal size stability of coal upon entering the gasifier.

  6. Knife mill operating factors effect on switchgrass particle size distributions

    SciTech Connect

    Bitra, V.S.P.; Womac, A.R.; Yang, Y.T.; Igathinathane, C.; Miu, P.I; Chevanan, Nehru; Sokhansanj, Shahabaddine

    2009-06-01

    Biomass particle size impacts handling, storage, conversion, and dust control systems. Switchgrass (Panicum virgatum L.) particle size distributions created by a knife mill were determined for integral classifying screen sizes from 12.7 to 50.8 mm, operating speeds from 250 to 500 rpm, and mass input rates from 2 to 11 kg/min. Particle distributions were classified with standardized sieves for forage analysis that included horizontal sieving motion with machined-aluminum sieves of thickness proportional to sieve opening dimensions. Then, a wide range of analytical descriptors were examined to mathematically represent the range of particle sizes in the distributions. Correlation coefficient of geometric mean length with knife mill screen size, feed rate, and speed were 0.872, 0.349, and 0.037, respectively. Hence, knife mill screen size largely determined particle size of switchgrass chop. Feed rate had an unexpected influence on particle size, though to a lesser degree than screen size. The Rosin Rammler function fit the chopped switchgrass size distribution data with an R2 > 0.982. Mass relative span was greater than 1, which indicated a wide distribution of particle sizes. Uniformity coefficient was more than 4.0, which indicated a large assortment of particles and also represented a well-graded particle size distribution. Knife mill chopping of switchgrass produced strongly fine skewed mesokurtic particles with 12.7 25.4 mm screens and fine skewed mesokurtic particles with 50.8 mm screen. Results of this extensive analysis of particle sizes can be applied to selection of knife mill operating parameters to produce a particular size of switchgrass chop, and will serve as a guide for relations among the various analytic descriptors of biomass particle distributions.

  7. Knife mill operating factors effect on switchgrass particle size distributions.

    PubMed

    Bitra, Venkata S P; Womac, Alvin R; Yang, Yuechuan T; Igathinathane, C; Miu, Petre I; Chevanan, Nehru; Sokhansanj, Shahab

    2009-11-01

    Biomass particle size impacts handling, storage, conversion, and dust control systems. Switchgrass (Panicum virgatum L.) particle size distributions created by a knife mill were determined for integral classifying screen sizes from 12.7 to 50.8 mm, operating speeds from 250 to 500 rpm, and mass input rates from 2 to 11 kg/min. Particle distributions were classified with standardized sieves for forage analysis that included horizontal sieving motion with machined-aluminum sieves of thickness proportional to sieve opening dimensions. Then, a wide range of analytical descriptors were examined to mathematically represent the range of particle sizes in the distributions. Correlation coefficient of geometric mean length with knife mill screen size, feed rate, and speed were 0.872, 0.349, and 0.037, respectively. Hence, knife mill screen size largely determined particle size of switchgrass chop. Feed rate had an unexpected influence on particle size, though to a lesser degree than screen size. The Rosin-Rammler function fit the chopped switchgrass size distribution data with an R(2)>0.982. Mass relative span was greater than 1, which indicated a wide distribution of particle sizes. Uniformity coefficient was more than 4.0, which indicated a large assortment of particles and also represented a well-graded particle size distribution. Knife mill chopping of switchgrass produced 'strongly fine skewed mesokurtic' particles with 12.7-25.4 mm screens and 'fine skewed mesokurtic' particles with 50.8 mm screen. Results of this extensive analysis of particle sizes can be applied to selection of knife mill operating parameters to produce a particular size of switchgrass chop, and will serve as a guide for relations among the various analytic descriptors of biomass particle distributions.

  8. Monitoring the particle size in CFB using fuzzy neural network

    SciTech Connect

    Ma, L.; Chen, H.; Tian, Z.; He, W.

    1999-07-01

    The particle size and particle size distributions (PSDs) affect the performance of a circulating fluidized (CFB) boiler. For improving the efficiency of analysis of particle size to monitor the particle size and particle size distribution, a fuzzy neural network (FNN) model is presented. Because the pressure fluctuant frequency and particle size have some non-linear relationship, the FNN models the relationship between the pressure fluctuant frequencies along CFB boiler height and particle size sampled from CFB boiler by neural network training. A hybrid fuzzy neural network parameter training method is presented to identify the model parameters, which combine the gradient back propagation (BP) algorithm and least square estimation (LSE) algorithm to estimate unknown non-linear parameter and linear parameter respectively. When the FNN training procedure converges, the parameters, which reflect the non-linear relationship between frequency and particle, are determined for a given operational condition of CFB boiler. In operating CFB boilers, the coal particle size at high temperature changes with combustion and its values are unknown, however, pressure fluctuation frequency can be obtained easily. In this case, FNN can predict the particle size and PSDs along the CFB boiler height according to the pressure fluctuation frequency. To validate the FNN model effect of analyzing the particle size, data from experiment are used with fluidized gas velocity equal to 41.82 cm/s. The predictive error of FNN model is 3.839%. It is proved that the model not only identifies the non-linear relationship between particle size and pressure fluctuation frequency with high precision but also can adaptively learn the data information without expert knowledge by adjusting its own parameters. It operates quickly and can satisfy the real-time request of monitoring the particle size and its distribution in CFB boilers.

  9. Process for preparation of large-particle-size monodisperse latexes

    NASA Technical Reports Server (NTRS)

    Vanderhoff, J. W.; Micale, F. J.; El-Aasser, M. S.; Kornfeld, D. M. (Inventor)

    1981-01-01

    Monodisperse latexes having a particle size in the range of 2 to 40 microns are prepared by seeded emulsion polymerization in microgravity. A reaction mixture containing smaller monodisperse latex seed particles, predetermined amounts of monomer, emulsifier, initiator, inhibitor and water is placed in a microgravity environment, and polymerization is initiated by heating. The reaction is allowed to continue until the seed particles grow to a predetermined size, and the resulting enlarged particles are then recovered. A plurality of particle-growing steps can be used to reach larger sizes within the stated range, with enlarge particles from the previous steps being used as seed particles for the succeeding steps. Microgravity enables preparation of particles in the stated size range by avoiding gravity related problems of creaming and settling, and flocculation induced by mechanical shear that have precluded their preparation in a normal gravity environment.

  10. Evaluation of process for sludge particle size reduction

    SciTech Connect

    Precechtel, D.R.; Packer, M.J., Fluor Daniel Hanford

    1997-03-18

    This document evaluates the available technology for K Basin sludge particle size. The results can be used to demonstrate the sensitivity or lack thereof, of K Basin sludge to available reduction processes and TWRS proposed particle acceptance criteria.

  11. Brazil-nut effect: Size separation of granular particles

    NASA Astrophysics Data System (ADS)

    Möbius, Matthias E.; Lauderdale, Benjamin E.; Nagel, Sidney R.; Jaeger, Heinrich M.

    2001-11-01

    Granular media differ from other materials in their response to stirring or jostling - unlike two-fluid systems, bi-disperse granular mixtures will separate according to particle size when shaken, with large particles rising, a phenomenon termed the 'Brazil-nut effect'. Mounting evidence indicates that differences in particle density affect size separation in mixtures of granular particles. We show here that this density dependence does not follow a steady trend but is non-monotonic and sensitive to background air pressure. Our results indicate that particle density and interstitial air must both be considered in size segregation.

  12. Dependence of strength on particle size in graphite

    SciTech Connect

    Kennedy, E.P.; Kennedy, C.R.

    1980-06-08

    The strength to particle size relationship for specially fabricated graphites has been demonstrated and rationalized using fracture mechanics. In the past, similar studies have yielded empirical data using only commercially available material. Thus, experimental verification of these relationships has been difficult. However, the graphites of this study were fabricated by controlling the particle size ranges for a series of isotropic graphites. All graphites that were evaluated had a constant 1.85 g/cm/sup 3/ density. Thus, particle size was the only variable. This study also considered the particle size effect on other physical properties; coefficient of thermal expansion (CTE), electrical resistivity, fracture strain, and Young's modulus.

  13. The biological response to nanometre-sized polymer particles

    PubMed Central

    Liu, Aiqin; Richards, Laura; Bladen, Catherine L.; Ingham, Eileen; Fisher, John; Tipper, Joanne L.

    2015-01-01

    Recently, nanometre-sized UHMWPE particles generated from hip and knee replacements have been identified in vitro and in vivo. UHMWPE particles in the 0.1–1.0 μm size range have been shown to be more biologically active than larger particles, provoking an inflammatory response implicated in late aseptic loosening of total joint replacements. The biological activity of nanometre-sized particles has not previously been studied. The biological response to clinically-relevant UHMWPE wear particles including nanometre-sized and micrometre-sized, along with polystyrene particles (FluoSpheres 20 nm, 60 nm, 200 nm and 1.0 μm), and nanometre-sized model polyethylene particles (Ceridust 3615®), was determined in terms of osteolytic cytokine release from primary human peripheral blood mononuclear cells (PBMNCs). Nanometre-sized UHMWPE wear particles, nanometre-sized Ceridust 3615® and 20 nm FluoSpheres had no significant effect on TNF-α, IL-1β, IL-6 and IL-8 release from PBMNCs at a concentration of 100 μm3 particles per cell after 12 and 24 h. The micrometre-size UHMWPE wear particles (0.1–1.0 μm) and 60 nm, 200 nm and 1.0 μm FluoSpheres caused significantly elevated osteolytic cytokine release from PBMNCs. These results indicated that particles below circa 50 nm fail to activate PBMNCs and that particle size, composition and morphology played a crucial role in cytokine release by particle stimulated macrophages. PMID:26004221

  14. Particle size dependent chemistry from laser ablation of brass.

    PubMed

    Liu, Chunyi; Mao, Xianglei; Mao, Sam S; Greif, Ralph; Russo, Richard E

    2005-10-15

    The proportion of zinc and copper in particles formed by laser ablation of brass was found to vary with the particle diameter. Energy-dispersive X-ray analysis showed that smaller particles were zinc enhanced while larger particles were composed mostly of copper. A model based on condensation of vapor onto large droplets ejected from a melted liquid layer is proposed to describe the change in particle composition versus size.

  15. Seed particle response and size characterization in high speed flows

    NASA Technical Reports Server (NTRS)

    Rudoff, Roger C.; Bachalo, William D.

    1991-01-01

    The response of seed particles ranging between 0.7 and 8.7 micron is determined using a phase Doppler particle analyzer which simultaneously measures particle size and velocity. The stagnant seed particles are entrained into a high speed free jet at velocities ranging from 40 to 300 m/s. The size-mean axial velocity correlation and size-rms velocity correlations are used to determine the particle response to the sudden acceleration. It was determined that at the lower speeds, seed particles up to approximately 5 microns are adequate, but as velocities approach 300 m/s only particles on the order of one micron are suitable. The ability to determine size and velocity simultaneously is essential if seeding with polydispersions is used since it allows the rejection of data which will not accurately represent the flow field.

  16. Selective follicular targeting by modification of the particle sizes.

    PubMed

    Patzelt, Alexa; Richter, Heike; Knorr, Fanny; Schäfer, Ulrich; Lehr, Claus-Michael; Dähne, Lars; Sterry, Wolfram; Lademann, Juergen

    2011-02-28

    Hair follicles represent interesting target sites for topically applied substances such as topical vaccinations or agents used in the field of regenerative medicine. In recent years, it could be shown that particles penetrate very effectively into the hair follicles. In the present study, the influence of particle size on the follicular penetration depths was examined. The penetration depths of two different types of particles sized 122 to 1000 nm were determined in vitro on porcine skin. The results revealed that the particles of medium size (643 and 646 nm, respectively) penetrated deeper into the porcine hair follicles than smaller or larger particles. It was concluded that by varying the particle size, different sites within the porcine hair follicle can be targeted selectively. For the human terminal hair follicle, the situation can be expected to be similar due to a similar size ratio of the hair follicles.

  17. Direct Characterization of Airborne Particles Associated with Arsenic-rich Mine Tailings: Particle Size Mineralogy and Texture

    SciTech Connect

    M Corriveau; H Jamieson; M Parsons; J Campbell; A Lanzirotti

    2011-12-31

    Windblown and vehicle-raised dust from unvegetated mine tailings can be a human health risk. Airborne particles from As-rich abandoned Au mine tailings from Nova Scotia, Canada have been characterized in terms of particle size, As concentration, As oxidation state, mineral species and texture. Samples were collected in seven aerodynamically fractionated size ranges (0.5-16 {micro}m) using a cascade impactor deployed at three tailings fields. All three sites are used for recreational activities and off-road vehicles were racing on the tailings at two mines during sample collection. Total concentrations of As in the <8 {micro}m fraction varied from 65 to 1040 ng/m{sup 3} of air as measured by proton-induced X-ray emission (PIXE) analysis. The same samples were analysed by synchrotron-based microfocused X-ray absorption near-edge spectroscopy ({micro}XANES) and X-ray diffraction ({micro}XRD) and found to contain multiple As-bearing mineral species, including Fe-As weathering products. The As species present in the dust were similar to those observed in the near-surface tailings. The action of vehicles on the tailings surface may disaggregate material cemented with Fe arsenate and contribute additional fine-grained As-rich particles to airborne dust. Results from this study can be used to help assess the potential human health risks associated with exposure to airborne particles from mine tailings.

  18. Three-dimensional combined pyrometric sizing and velocimetry of combusting coal particles. II: Pyrometry.

    PubMed

    Toth, Pal; Draper, Teri; Palotas, Arpad B; Ring, Terry A; Eddings, Eric G

    2015-05-20

    Knowledge of the in situ temperature, size, velocity, and number density of a population of burning coal particles yields insight into the chemical and aerodynamic behavior of a pulverized coal flame (e.g., through means of combustion model validation). Sophisticated and reasonably accurate methods are available for the simultaneous measurement of particle velocity and temperature; however, these methods typically produce single particle measurements in small analyzed volumes and require extensive instrumentation. We present a simple, inexpensive method for the simultaneous, in situ, three-dimensional (3D) measurement of particle velocity, number density, size, and temperature. The proposed method uses a combination of stereo imaging, 3D reconstruction, multicolor pyrometry, and digital image processing techniques. The details of theoretical and algorithmic backgrounds are presented, along with examples and validation experiments. Rigorous uncertainty quantification was performed using numerical simulations to estimate the accuracy of the method and explore how different parameters affect measurement uncertainty. This paper, Part II of two parts that discuss this method [Appl. Opt.54, 4049 (2015)], describes particle temperature and size measurement in overexposed emission images.

  19. Optical properties of size-resolved particles at a Hong Kong urban site during winter

    NASA Astrophysics Data System (ADS)

    Gao, Yuan; Lai, Senchao; Lee, Shun-Cheng; Yau, Pui Shan; Huang, Yu; Cheng, Yan; Wang, Tao; Xu, Zheng; Yuan, Chao; Zhang, Yingyi

    2015-03-01

    Visibility degradation in Hong Kong is related to the city's serious air pollution problems. To investigate the aerosols' optical properties and their relationship with the chemical composition and size distribution of the particles, a monitoring campaign was conducted at an urban site in the early winter period (from October to December, 2010). The particle light scattering coefficient (Bsp) and absorption coefficient (Bap) were measured. Two collocated Micro-Orifice Uniform Deposit Impactor samplers (MOUDI110, MSP, USA) with nominal 50% cut-off aerodynamic diameters of 18, 10, 5.6, 3.2, 1.8, 1, 0.56, 0.32, 0.18, 0.1, and 0.056 μm were used to collect size-resolved particle samples. The average Bsp and Bap were 201.96 ± 105.82 Mm- 1 and 39.91 ± 19.16 Mm- 1, with an average single scattering albedo (ωo) of 0.82 ± 0.07. The theoretical method of light extinction calculation was used to determine the extinction of the size-resolved particulate matters (PM). The reconstructed light scattering coefficient correlated well with the measured scattering value in the Hong Kong urban area. Droplet mode (0.56-1.8 μm) particles contributed most to the particle light extinction (~ 69%). Organic matter, ammonium sulphate and elemental carbon were the key components causing visibility degradation in the droplet (0.56-1.8 μm) and condensation (0.1-0.56 μm) size ranges. Five sources contributing to particle light extinction have been identified using positive matrix factorisation (PMF). Traffic/engine exhausts and secondary aerosols accounted for ~ 36% and ~ 32% of particle light extinction, respectively, followed by sea salt (15%). The remaining sources, soil/fugitive dust and tire dust, contributed by ~ 10% and 7%, respectively, to particle light extinction.

  20. On the impact of size and position of semi-trailer on the aerodynamic drag of an articulated vehicle

    NASA Astrophysics Data System (ADS)

    Maciejewski, M.

    2016-09-01

    The paper relates to the numerical aerodynamic simulation of an articulated vehicle. All simulations were comparative, where variables were only three geometric parameters: the height and length of the semi-trailer, and the gap between the tractor and semi-trailer. Simulation results have been investigated and compared in terms of observed values of aerodynamic drag coefficients. These coefficients have been presented in time (for example only), but above all, as constant, averaged magnitudes which are more suitable for comparisons. Total number of simulations and thereby geometrical configurations was 125, i.e. for 5 sizes of the height and length of trailer, and 5 clearance gaps between the tractor and trailer. Results have been presented graphically and discussed.

  1. Effect of particle size on enzymatic hydrolysis of pretreated Miscanthus

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Particle size reduction is a crucial factor in transportation logistics as well as cellulosic conversion. The effect of particle size on enzymatic hydrolysis of pretreated Miscanthus x giganteus was determined. Miscanthus was ground using a hammer mill equipped with screens having 0.08, 2.0 or 6.0...

  2. Indoor/outdoor radon decay products associated aerosol particle-size distributions and their relation to total number concentrations.

    PubMed

    Moriizumi, Jun; Yamada, Shinya; Xu, Yang; Matsuki, Satoru; Hirao, Shigekazu; Yamazawa, Hiromi

    2014-07-01

    The activity size distributions of indoor and outdoor radioactive aerosol associated with short-lived radon decay products were observed at Nagoya, Japan, for some periods from 2010 to 2012, following the indoor observation by Mostafa et al. [Mostafa, A. M. A., Tamaki, K., Moriizumi, J., Yamazawa, H. and Iida, T. The weather dependence of particle size distribution of indoor radioactive aerosol associated with radon decay products. Radiat. Prot. Dosim. 146: (1-3), 19-22 (2011)]. The tendency of smaller indoor activity median aerodynamic diameter (AMAD) after rainfalls showed in the previous study was not consistently obtained, while the consistent tendency of less indoor radioactive particles with diameters in the accumulation mode was observed again after rainfalls. The indoor aerosols showed activity size distributions similar to the outdoor ones. Non-radioactive aerosol particle concentrations measured with a laser particle counter suggested a somewhat liner relationship with AMAD.

  3. Hydrodynamic model for particle size segregation in granular media

    NASA Astrophysics Data System (ADS)

    Trujillo, Leonardo; Herrmann, Hans J.

    2003-12-01

    We present a hydrodynamic theoretical model for “Brazil nut” size segregation in granular materials. We give analytical solutions for the rise velocity of a large intruder particle immersed in a medium of monodisperse fluidized small particles. We propose a new mechanism for this particle size-segregation due to buoyant forces caused by density variations which come from differences in the local “granular temperature”. The mobility of the particles is modified by the energy dissipation due to inelastic collisions and this leads to a different behavior from what one would expect for an elastic system. Using our model we can explain the size ratio dependence of the upward velocity.

  4. Particle Size Influences Fibronectin Internalization and Degradation by Fibroblasts

    NASA Astrophysics Data System (ADS)

    Bozavikov, Peter

    Particle size is a crucial factor that influences the fate and biological impact of particles and their surface proteins upon internalization. Here, using fibronectin-coated polystyrene nanoparticles and microparticles we examined the effect of particle size on degradation of fibronectin. Microparticle uptake depended primarily on beta1 integrins and actin filaments, while nanoparticle uptake relied mainly on lipid rafts and specifically on clathrin-mediated endocytosis. Further, biotinylated fibronectin when coated on microparticles underwent more intracellular processing than fibronectin coated on to nanoparticles. Thus, particle size affects actin and clathrin- dependent internalization, which in turn regulates intracellular fibronectin degradation.

  5. Planar particle/droplet size measurement technique using digital particle image velocimetry image data

    NASA Technical Reports Server (NTRS)

    Wernet, Mark P. (Inventor); Mielke, Amy F. (Inventor); Kadambi, Jaikrishnan R. (Inventor)

    2005-01-01

    A method for determining a mass flux of an entrained phase in a planar two-phase flow records images of particles in the two-phase flow. Respective sizes of the particles (the entrained phase) are determined as a function of a separation between spots identified on the particle images. Respective velocities of the particles are determined. The mass flux of the entrained phase is determined as a function of the size and velocity of the particles.

  6. A hybrid mathematical model for controlling particle size, particle size distribution, and color properties of toner particles

    NASA Astrophysics Data System (ADS)

    Ataeefard, Maryam; Shadman, Alireza; Saeb, Mohammad Reza; Mohammadi, Yousef

    2016-08-01

    A mathematical modeling approach was proposed combining the capabilities of response surface methodology (RSM) and desirability function (DF) and implemented successfully in production of printing toner particles. Toner powders were systematically synthesized through suspension copolymerization process. Applying RSM, a series of experiments were designed and toner particles were prepared and the effects of monomer ratio, colorant and surfactant content on the particle size (PS), particle size distribution (PSD), thermal and colorimetric properties (∆ E) of the resulting toner were monitored and discussed. The second-order models corresponding to each target characteristic, i.e., PS, PSD, and ∆ E of different types of toner powders, were obtained by individual optimization to express variation of each property in terms of polymerization parameters. Applying statistical calculations, the best reduced models were identified to be fed in the second step of optimization. Since toners with appropriate PS, PSD, and CP were needed, we applied multi-objective optimization based on DF approach. The results show that exact tuning of toner properties is closely possible with the aid of hybrid mathematical model developed in this work. Noticeably, desirabilities are very close to 100 %.

  7. Stability and size of particle pairs in complex plasmas

    SciTech Connect

    Nosenko, V.; Ivlev, A. V.; Kompaneets, R.; Morfill, G.

    2014-11-15

    Particle pairing in a complex plasma was experimentally studied with the emphasis on pair spatial extent and stability. Micron-size particles were suspended in the (pre)sheath area above the lower electrode in a capacitively coupled radio-frequency discharge in argon. They formed vertical pairs due to the ion wakes created by the flow of ions past particles. We discuss the confinement mechanism for the lower particle, resulting from a combination of the wake field and the field of non-uniform sheath. A model of particle pairs is proposed, which provides good description for the dependence of pair size and stability on experimental parameters.

  8. Noninvasive particle sizing using camera-based diffuse reflectance spectroscopy.

    PubMed

    Abildgaard, Otto Højager Attermann; Frisvad, Jeppe Revall; Falster, Viggo; Parker, Alan; Christensen, Niels Jørgen; Dahl, Anders Bjorholm; Larsen, Rasmus

    2016-05-10

    Diffuse reflectance measurements are useful for noninvasive inspection of optical properties such as reduced scattering and absorption coefficients. Spectroscopic analysis of these optical properties can be used for particle sizing. Systems based on optical fiber probes are commonly employed, but their low spatial resolution limits their validity ranges for the coefficients. To cover a wider range of coefficients, we use camera-based spectroscopic oblique incidence reflectometry. We develop a noninvasive technique for acquisition of apparent particle size distributions based on this approach. Our technique is validated using stable oil-in-water emulsions with a wide range of known particle size distributions. We also measure the apparent particle size distributions of complex dairy products. These results show that our tool, in contrast to those based on fiber probes, can deal with a range of optical properties wide enough to track apparent particle size distributions in a typical industrial process.

  9. Laser Doppler spectrometer method of particle sizing. [for air pollution

    NASA Technical Reports Server (NTRS)

    Weber, F. N.

    1976-01-01

    A spectrometer for the detection of airborne particulate pollution in the submicron size range is described. In this device, airborne particles are accelerated through a supersonic nozzle, with different sizes achieving different velocities in the gas flow. Information about the velocities of the accelerated particles is obtained with a laser-heterodyne optical system through the Doppler shift of light scattered from the particles. Detection is accomplished by means of a photomultiplier. Nozzle design and signal processing techniques are also discussed.

  10. Particle Sizing in Solid Rocket Motors

    DTIC Science & Technology

    1989-03-01

    reduced. A reduction in agglomeration can be expected due to the geometry of the closely packed AP particles. Tighter AP intersticial spacing reduces... intersticial "pockets" which enhanced agglomeration more than did the 4.69% aluminum content propellant matrix. * There was a large increase in quantities of

  11. The Size of Gelatin Sponge Particles: Differences with Preparation Method

    SciTech Connect

    Katsumori, Tetsuya Kasahara, Toshiyuki

    2006-12-15

    Purpose. To assess whether the size distribution of gelatin sponge particles differed according to the method used to make them and the type of original sheet. Methods. Gelatin sponge particles of approximately 1-1.5 x 1-1.5 x 2 mm were made from either Spongel or Gelfoam sheets by cutting with a scalpel and scissors. Particles were also made of either Spongel or Gelfoam sheets by pumping with two syringes and a three-way stopcock. The size distribution of the particles in saline was compared among the groups. Results. (1) Cutting versus pumping: When Spongel was used, cutting produced lower rates of smaller particles {<=}500 {mu}m and larger particles >2000 {mu}m compared with pumping back and forth 30 times (1.1% vs 37.6%, p < 0.0001; 2.2% vs 14.4%, p = 0.008). When Gelfoam was used, cutting produced lower rates of smaller and larger particles compared with pumping (8.5% vs 20.4%, p = 0.1809; 0% vs 48.1%, p < 0.0001). (2) Spongel versus Gelfoam: There was no significant difference in the size distribution of the particles between Spongel and Gelfoam (p = 0.2002) when cutting was used. Conclusion. The size distribution of gelatin sponge particles differed according to the method used to make them. More uniform particle sizes can be achieved by cutting than by pumping.

  12. Particle size distributions of particulate emissions from the ferroalloy industry evaluated by electrical low pressure impactor (ELPI).

    PubMed

    Kero, Ida; Naess, Mari K; Tranell, Gabriella

    2015-01-01

    The present article presents a comprehensive evaluation of the potential use of an Electrical Low Pressure Impactor (ELPI) in the ferroalloy industry with respect to indoor air quality and fugitive emission control. The ELPI was used to assess particulate emission properties, particularly of the fine particles (Dp ≤ 1 μm), which in turn may enable more satisfactory risk assessments for the indoor working conditions in the ferroalloy industry. An ELPI has been applied to characterize the fume in two different ferroalloy plants, one producing silicomanganese (SiMn) alloys and one producing ferrosilicon (FeSi) alloys. The impactor classifies the particles according to their aerodynamic diameter and gives real-time particle size distributions (PSD). The PSD based on both number and mass concentrations are shown and compared. Collected particles have also been analyzed by transmission and scanning electron microscopy with energy dispersive spectroscopy. From the ELPI classification, particle size distributions in the range 7 nm - 10 μm have been established for industrial SiMn and FeSi fumes. Due to the extremely low masses of the ultrafine particles, the number and mass concentration PSD are significantly different. The average aerodynamic diameters for the FeSi and the SiMn fume particles were 0.17 and 0.10 μm, respectively. Based on this work, the ELPI is identified as a valuable tool for the evaluation of airborne particulate matter in the indoor air of metallurgical production sites. The method is well suited for real-time assessment of morphology (particle shape), particle size, and particle size distribution of aerosols.

  13. Particle Size Distributions of Particulate Emissions from the Ferroalloy Industry Evaluated by Electrical Low Pressure Impactor (ELPI)

    PubMed Central

    Kero, Ida; Naess, Mari K.; Tranell, Gabriella

    2015-01-01

    The present article presents a comprehensive evaluation of the potential use of an Electrical Low Pressure Impactor (ELPI) in the ferroalloy industry with respect to indoor air quality and fugitive emission control. The ELPI was used to assess particulate emission properties, particularly of the fine particles (Dp ≤ 1 μm), which in turn may enable more satisfactory risk assessments for the indoor working conditions in the ferroalloy industry. An ELPI has been applied to characterize the fume in two different ferroalloy plants, one producing silicomanganese (SiMn) alloys and one producing ferrosilicon (FeSi) alloys. The impactor classifies the particles according to their aerodynamic diameter and gives real-time particle size distributions (PSD). The PSD based on both number and mass concentrations are shown and compared. Collected particles have also been analyzed by transmission and scanning electron microscopy with energy dispersive spectroscopy. From the ELPI classification, particle size distributions in the range 7 nm – 10 μm have been established for industrial SiMn and FeSi fumes. Due to the extremely low masses of the ultrafine particles, the number and mass concentration PSD are significantly different. The average aerodynamic diameters for the FeSi and the SiMn fume particles were 0.17 and 0.10 μm, respectively. Based on this work, the ELPI is identified as a valuable tool for the evaluation of airborne particulate matter in the indoor air of metallurgical production sites. The method is well suited for real-time assessment of morphology (particle shape), particle size, and particle size distribution of aerosols. PMID:25380385

  14. Particle size and particle-particle interactions on tensile properties and reinforcement of corn flour particles in natural rubber

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Renewable corn flour has a significant reinforcement effect in natural rubber. The corn flour was hydrolyzed and microfluidized to reduce its particle size. Greater than 90% of the hydrolyzed corn flour had an average size of ~300 nm, a reduction of 33 times compared to unhydrolyzed corn flour. Comp...

  15. Effects of particle size distribution in thick film conductors

    NASA Technical Reports Server (NTRS)

    Vest, R. W.

    1983-01-01

    Studies of particle size distribution in thick film conductors are discussed. The distribution of particle sizes does have an effect on fired film density but the effect is not always positive. A proper distribution of sizes is necessary, and while the theoretical models can serve as guides to selecting this proper distribution, improved densities can be achieved by empirical variations from the predictions of the models.

  16. Size limit for particle-stabilized emulsion droplets under gravity.

    PubMed

    Tavacoli, J W; Katgert, G; Kim, E G; Cates, M E; Clegg, P S

    2012-06-29

    We demonstrate that emulsion droplets stabilized by interfacial particles become unstable beyond a size threshold set by gravity. This holds not only for colloids but also for supracolloidal glass beads, using which we directly observe the ejection of particles near the droplet base. The number of particles acting together in these ejection events decreases with time until a stable acornlike configuration is reached. Stability occurs when the weight of all remaining particles is less than the interfacial binding force of one particle. We also show the importance of the curvature of the droplet surface in promoting particle ejection.

  17. In vitro toxicology of ambient particulate matter: correlation of cellular effects with particle size and components.

    PubMed

    Kroll, Alexandra; Gietl, Johanna K; Wiesmüller, Gerhard A; Günsel, Andreas; Wohlleben, Wendel; Schnekenburger, Jürgen; Klemm, Otto

    2013-02-01

    High concentrations of airborne particulate matter (PM) have been associated with increased rates of morbidity and mortality among exposed populations. Although certain components of PM were suggested to influence these effects, no clear-cut correlation was determined thus far. One of the possible modes of action is the induction of oxidative stress by inhaled PM triggering inflammatory responses. Therefore, the in vitro formation of reactive oxygen species (ROS) in three cell lines in the presence of five subfractions of PM(10), collected in Münster, Germany was investigated. The PM components chloride, nitrate, ammonium, sulfate, 68 chemical elements, and endotoxin were quantified. The highest concentration of endotoxin was found in particles of 0.42-1.2 μm aerodynamic diameters, and therefore probably subject to long-range transport. Intracellular ROS formation in three well established mammalian cell lines (CaCo2, human; MDCK, canine; RAW264.7, mouse) only correlated positively with particle size. The two smallest PM size fractions provoked the highest rise in ROS. However, the latter did not correlate with the concentration of any PM components investigated. The smallest PM size fractions significantly dominated the number of particles. Therefore, the particle number may be most effective in inducing oxidative stress in vitro.

  18. ON TRIMODAL PARTICLE SIZE DISTRIBUTIONS IN FLY ASH FROM PULVERIZED COAL COMBUSTION

    EPA Science Inventory

    Combustion generated fine particles, defined as those with aerodynamic diameters less than 2.5 micrometers, have come under increased regulatory scrutiny because of suspected links to adverse human health effects. Whereas classical theories regarding coal combustion suggest that ...

  19. Alpha spectrometric characterization of process-related particle size distributions from active particle sampling at the Los Alamos National Laboratory uranium foundry

    SciTech Connect

    Plionis, Alexander A; Peterson, Dominic S; Tandon, Lav; Lamont, Stephen P

    2009-01-01

    Uranium particles within the respirable size range pose a significant hazard to the health and safety of workers. Significant differences in the deposition and incorporation patterns of aerosols within the respirable range can be identified and integrated into sophisticated health physics models. Data characterizing the uranium particle size distribution resulting from specific foundry-related processes are needed. Using personal air sampling cascade impactors, particles collected from several foundry processes were sorted by activity median aerodynamic diameter onto various Marple substrates. After an initial gravimetric assessment of each impactor stage, the substrates were analyzed by alpha spectrometry to determine the uranium content of each stage. Alpha spectrometry provides rapid nondestructive isotopic data that can distinguish process uranium from natural sources and the degree of uranium contribution to the total accumulated particle load. In addition, the particle size bins utilized by the impactors provide adequate resolution to determine if a process particle size distribution is: lognormal, bimodal, or trimodal. Data on process uranium particle size values and distributions facilitate the development of more sophisticated and accurate models for internal dosimetry, resulting in an improved understanding of foundry worker health and safety.

  20. Particle size- and concentration-dependent separation of magnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Witte, Kerstin; Müller, Knut; Grüttner, Cordula; Westphal, Fritz; Johansson, Christer

    2017-04-01

    Small magnetic nanoparticles with a narrow size distribution are of great interest for several biomedical applications. When the size of the particles decreases, the magnetic moment of the particles decreases. This leads to a significant increase in the separation time by several orders of magnitude. Therefore, in the present study the separation processes of bionized nanoferrites (BNF) with different sizes and concentrations were investigated with the commercial Sepmag Q system. It was found that an increasing initial particle concentration leads to a reduction of the separation time for large nanoparticles due to the higher probability of building chains. Small nanoparticles showed exactly the opposite behavior with rising particle concentration up to 0.1 mg(Fe)/ml. For higher iron concentrations the separation time remains constant and the measured Z-average decreases in the supernatant at same time intervals. At half separation time a high yield with decreasing hydrodynamic diameter of particles can be obtained using higher initial particle concentrations.

  1. Packing fraction of particles with lognormal size distribution

    NASA Astrophysics Data System (ADS)

    Brouwers, H. J. H.

    2014-05-01

    This paper addresses the packing and void fraction of polydisperse particles with a lognormal size distribution. It is demonstrated that a binomial particle size distribution can be transformed into a continuous particle-size distribution of the lognormal type. Furthermore, an original and exact expression is derived that predicts the packing fraction of mixtures of particles with a lognormal distribution, which is governed by the standard deviation, mode of packing, and particle shape only. For a number of particle shapes and their packing modes (close, loose) the applicable values are given. This closed-form analytical expression governing the packing fraction is thoroughly compared with empirical and computational data reported in the literature, and good agreement is found.

  2. Sonochemical synthesis of silica particles and their size control

    NASA Astrophysics Data System (ADS)

    Kim, Hwa-Min; Lee, Chang-Hyun; Kim, Bonghwan

    2016-09-01

    Using an ultrasound-assisted sol-gel method, we successfully synthesized very uniformly shaped, monodisperse, and size-controlled spherical silica particles from a mixture of ethanol, water, and tetraethyl orthosilicate in the presence of ammonia as catalyst, at room temperature. The diameters of the silica particles were distributed in the range from 40 to 400 nm; their morphology was well characterized by scanning electron microscopy. The silica particle size could be adjusted by choosing suitable concentrations of ammonium hydroxide and water, which in turn determined the nucleation and growth rates of the particles during the reaction. This sonochemical-based silica synthesis offers an alternative way to produce spherical silica particles in a relatively short reaction time. Thus, we suggest that this simple, low-cost, and efficient method of preparing uniform silica particles of various sizes will have practical and wide-ranging industrial applicability.

  3. Particle size and shape distributions of hammer milled pine

    SciTech Connect

    Westover, Tyler Lott; Matthews, Austin Colter; Williams, Christopher Luke; Ryan, John Chadron Benjamin

    2015-04-01

    Particle size and shape distributions impact particle heating rates and diffusion of volatized gases out of particles during fast pyrolysis conversion, and consequently must be modeled accurately in order for computational pyrolysis models to produce reliable results for bulk solid materials. For this milestone, lodge pole pine chips were ground using a Thomas-Wiley #4 mill using two screen sizes in order to produce two representative materials that are suitable for fast pyrolysis. For the first material, a 6 mm screen was employed in the mill and for the second material, a 3 mm screen was employed in the mill. Both materials were subjected to RoTap sieve analysis, and the distributions of the particle sizes and shapes were determined using digital image analysis. The results of the physical analysis will be fed into computational pyrolysis simulations to create models of materials with realistic particle size and shape distributions. This milestone was met on schedule.

  4. Particle size characterization by quadruple-detector hydrodynamic chromatography.

    PubMed

    Brewer, Amandaa K; Striegel, André M

    2009-01-01

    Particle size and shape and their distribution directly influence a variety of end-use material properties related to packing, mixing, and transport of powders, solutions, and suspensions. Many of the techniques currently employed for particle size characterization have found limited applicability for broadly polydisperse and/or nonspherical particles. Here, we introduce a quadruple-detector hydrodynamic chromatography (HDC) method utilizing static multiangle light scattering (MALS), quasi-elastic light scattering (QELS), differential viscometry (VISC), and differential refractometry (DRI), and apply the technique to characterizing a series of solid and hollow polystyrene latexes with diameters in the approximate range of 40-400 nm. Using HDC/MALS/QELS/VISC/DRI, we were able to determine a multiplicity of size parameters and their polydispersity and to monitor the size of the particles across the elution profile of each sample. Using self-similarity scaling relationships between the molar mass and the various particle radii, we were also able to ascertain the shape of the latexes and the shape constancy as a function of particle size. The particle shape for each latex was confirmed by the dimensionless ratio rho identical with R (G,z )/R (H,z ) which, in addition, provided information on the structure (compactness) of the latexes as a function of particle size. Solid and hollow polystyrene latex samples were also differentiable using these methods. Extension of this method to nonspherical, fractal objects should be possible.

  5. Particle size distributions of several commonly used seeding aerosols

    NASA Technical Reports Server (NTRS)

    Crosswy, F. L.

    1985-01-01

    During the course of experimentation, no solid particle powder could be found which produced an aerosol with a narrow particle size distribution when fluidization was the only flow process used in producing the aerosol. The complication of adding particle size fractionation processes to the aerosol generation effort appears to be avoidable. In this regard, a simple sonic orifice is found to be effective in reducing the percentage of agglomerates in the several metal oxide powders tested. Marginally beneficial results are obtained for a 0.5/99.5 percent by weight mixture of the flow agent and metal oxide powder. However, agglomeration is observed to be enhanced when the flow agent percentage is increased to 5 percent. Liquid atomization using the Collison nebulizer as well as a version of the Laskin nozzle resulted in polydispersed aerosols with particle size distributions heavily weighted by the small particle end of the size spectrum. The aerosol particle size distributions produced by the vaporization/condensation seeder are closer to the ideal monodispersed aerosol than any of the other aerosols tested. In addition, this seeding approach affords a measure of control over particle size and particle production rate.

  6. Backscattering measurements of micron-sized spherical particles.

    PubMed

    Heffernan, Brendan M; Heinson, Yuli W; Maughan, Justin B; Chakrabarti, Amitabha; Sorensen, Christopher M

    2016-04-20

    An apparatus was designed and assembled to measure scattered light in the range of 180°±6° where enhanced backscattering, the cause of a glory, occurs. The apparatus was calibrated and tested using Fraunhofer circular aperture diffraction, angle of incidence correction, and a diffuse reflector. Theory indicates that backscattering is strongly dependent on particle size, refractive index, and shape. Experimental measurements from polystyrene latex spheres of two sizes and water droplets showed good agreement with Mie theory, but also indicated the extreme sensitivity of the backscattering to particle parameters. The results presented should have use in the fields of particle scattering, particle metrology, and LIDAR.

  7. Real-time characterization of the size and chemical composition of individual particles in ambient aerosol systems in Riverside, California

    SciTech Connect

    Noble, C.A.; Prather, K.A.

    1995-12-31

    Atmospheric aerosols, although ubiquitous, are highly diverse and continually fluctuating systems. A typical aerosol system may consist of particles with diameters between {approximately}0.002 {mu}m and {approximately}200 {mu}m. Even in rural or pristine areas, atmospheric particle concentration is significant, with concentrations up to 10{sup 8} particles/cm{sup 3} not being uncommon. Chemical composition of atmospheric particles vary from simple water droplets or acidic ices to soot particles and cigarette smoke. Due to changes in atmospheric conditions, processes such as nucleation, coagulation or heterogeneous chemistry may effect both physical and chemical properties of individual particles over relatively short time intervals. Recently, aerosol measurement techniques are focusing on determining the size and/or chemical composition of individual aerosol particles. This research group has recently developed aerosol time-of-flight mass spectrometry (ATOFMS), a technique which allows for real-time determination of the size and chemical composition of individual aerosol particles. Single particle measurements are performed in one instrument using dual laser aerodynamic particle sizing and time-of-flight mass spectrometry. Aerosol-time-of-flight mass spectrometry is briefly described in several other abstracts in this publication.

  8. Evaluation of the Malvern optical particle monitor. [Volumetric size distribution

    SciTech Connect

    Anderson, R. J.; Johnson, E.

    1983-07-01

    The Malvern 2200/3300 Particle Sizer is a laser-based optical particle sizing device which utilizes the principle of Fraunhofer Diffraction as the means of particle size measurement. The instrument is designed to analyze particle sizes in the range of 1 to 1800 microns diameter through a selection of lenses for the receiving optics. It is not a single-particle counter but rather an ensemble averager over the distribution of particles present in the measuring volume. Through appropriate measurement techniques, the instrument can measure the volumetric size distribution of: solids in gas or liquid suspension; liquid droplets in gas or other immiscible liquids; and, gas bubbles in liquid. (Malvern Handbook, Version 1.5). This report details a limited laboratory evaluation of the Malvern system to determine its operational characteristics, limitations, and accuracy. This investigation focused on relatively small particles in the range of 5 to 150 microns. Primarily, well characterized particles of coal in a coal and water mixture were utilized, but a selection of naturally occurring, industrially generated, and standard samples (i.e., glass beads) wer also tested. The characteristic size parameter from the Malvern system for each of these samples was compared with the results of a Coulter particle counter (Model TA II) analysis to determine the size measurement accuracy. Most of the particulate samples were suspended in a liquid media (water or isoton, plus a dispersant) for the size characterization. Specifically, the investigations contained in this report fall into four categories: (a) Sample-to-lense distance and sample concentration studies, (b) studies testing the applicability to aerosols, (c) tests of the manufacturer supplied software, and (d) size measurement comparisons with the results of Coulter analysis. 5 references, 15 figures, 2 tables.

  9. [The fractal characteristics of particle size distribution and conservation relationship].

    PubMed

    Jin, Peng-kang; Wang, Xiao-chang

    2004-01-01

    Using a microscopic technique, the characteristics of particle size distribution of Al-humic flocs were studied. The results showed that Al-humic floc size followed a lognormal distribution. By introducing the lognormal distribution and fractal dimension into the fundamental kinetic equation of flocculation, a conservation relationship was obtained between the total number of particles, average floc volume and standard deviation of floc size distribution. Significance of the relation can greatly simplify the complicated procedure of kinetic analysis and enable a more accurate evaluation of floc size distribution.

  10. Effect of tail size reductions on longitudinal aerodynamic characteristics of a three surface F-15 model with nonaxisymmetric nozzles

    NASA Technical Reports Server (NTRS)

    Frassinelli, Mark C.; Carson, George T., Jr.

    1990-01-01

    An investigation was conducted in the Langley 16-Foot Transonic Tunnel to determine the effects of horizontal and vertical tail size reductions on the longitudinal aerodynamic characteristics of a modified F-15 model with canards and 2-D convergent-divergent nozzles. Quantifying the drag decrease at low angles of attack produced by tail size reductions was the primary focus. The model was tested at Mach numbers of 0.40, 0.90, and 1.20 over an angle of attack of -2 degree to 10 degree. The nozzle exhaust flow was simulated using high pressure air at nozzle pressure ratios varying from 1.0 (jet off) to 7.5. Data were obtained on the baseline configuration with and without tails as well as with reduced horizontal and/or vertical tail sizes that were 75, 50, and 25 percent of the baseline tail areas.

  11. Effect of Cobalt Particle Size on Acetone Steam Reforming

    SciTech Connect

    Sun, Junming; Zhang, He; Yu, Ning; Davidson, Stephen; Wang, Yong

    2015-06-11

    Carbon-supported cobalt nanoparticles with different particle sizes were synthesized and characterized by complementary characterization techniques such as X-ray diffraction, N-2 sorption, acetone temperature-programmed desorption, transmission electron microscopy, and CO chemisorption. Using acetone steam reforming reaction as a probe reaction, we revealed a volcano-shape curve of the intrinsic activity (turnover frequency of acetone) and the CO2 selectivity as a function of the cobalt particle size with the highest activity and selectivity observed at a particle size of approximately 12.8nm. Our results indicate that the overall performance of acetone steam reforming is related to a combination of particle-size-dependent acetone decomposition, water dissociation, and the oxidation state of the cobalt nanoparticles.

  12. Appendix B: Summary of TEM Particle Size Distribution Datasets

    EPA Pesticide Factsheets

    As discussed in the main text (see Section 5.3.2), calculation of the concentration of asbestos fibers in each of the bins of potential interest requires particle size distribution data derived using transmission electron microscopy (TEM).

  13. Atmospheric particles acting as Ice Forming Nuclei in different size ranges

    NASA Astrophysics Data System (ADS)

    Santachiara, G.; Di Matteo, L.; Prodi, F.; Belosi, F.

    2010-05-01

    The work presents the results of an experimental campaign performed at a rural site (S. Pietro Capofiume, near Bologna July 2007) concerning measurements of ice nuclei in different size classes of aerosol: PM1, PM2.5, PM10 and total suspended particles (TSP). Simultaneous measurements of particle number concentrations were also performed. Aerosol in the PM1 fraction contributes about 50% of the measured ice nuclei number concentration, and in the PM10 fraction contributes about 70-90%. Consequently, the dominant fraction of aerosol that can be activated as ice nuclei involves particles with aerodynamic diameter less than 10 μm. A positive correlation is observed between higher supersaturation with respect to ice and water ( Sice and Sw, respectively) values, and ice nuclei number concentration. The variations of Sw from 2 to 10% and Sice from 20 to 32% ( Tair = - 15 °C) determine an approximately threefold increase (from 110 to 337 m - 3 ) in the ice nuclei average number concentration. There is no correlation between ice nuclei measured in the different size ranges, either with the particle number concentration measured with the counter spectrometer ( d > 0.3 μm) or with the condensation nuclei counter.

  14. Laser velocimeter seed particle sizing by the whisker particle collector and laser aerosol spectrometer methods

    NASA Astrophysics Data System (ADS)

    Crosswy, F. L.; Kingery, M. K.; Schaefer, H. J.; Pfeifer, H. J.

    1989-07-01

    Two different aerosol particle sizing systems, the Whisker Particle Collector (WPC) and the Laser Aerosol Spectrometer (LAS), were evaluated for sizing aerosol particles in the size range of 0.1 to 3.0 micrometers. The evaluation tests were conducted using an aerosol of alumina (Al2O3) particles, an aerosol commonly used to provide light scattering particles for laser velocimeter measurements in high temperature flows. The LAS and WPC measurements were then compared for samples taken from the alumina particle aerosols. Some difficulty was encountered in directly comparing these measurements. Other operational aspects of the two systems were also compared including on-line/off-line data presentation capabilities, field portability and measurement limitations at the small particle end of the size range of interest.

  15. Effect of particle size on the alcohol yield from corn

    SciTech Connect

    Gantt, R.E.; Hegg, R.O.

    1981-01-01

    A laboratory study was conducted to determine the effect of particle size on the conversion of corn to ethanol. Standard analytical procedures were used to measure carbohydrates, sugar, and alcohol. The highest yield obtained was 2.4 gal/bu with the average being 1.8 gal/bu. The results showed that particle size has little effect on alcohol yield. 7 refs.

  16. Medical Modeling of Particle Size Effects for CB Inhalation Hazards

    DTIC Science & Technology

    2015-09-01

    typical city. As has been described , many of the parameters in the model are hard-coded due to limitations in data transfer with SCIPUFF. When fully... describes the resulting medical impact. Many current models assume that only the 1 to 5 micron “respirable” particles capable of reaching the pulmonary...well. Inhalation mechanics , FXCODA, DARRT, bioagent, aerosol, particle size, particle deposition, biological agents, ricin, tularemia Unclassified

  17. Soil signature simulation of complex mixtures and particle size distributions

    NASA Astrophysics Data System (ADS)

    Carson, Tyler; Bachmann, Charles M.; Salvaggio, Carl

    2015-09-01

    Soil reflectance signatures were modeled using the digital imaging and remote sensing image generation model and Blender three-dimensional (3-D) graphic design software. Using these tools, the geometry, radiometry, and chemistry of quartz and magnetite were exploited to model the presence of particle size and porosity effects in the visible and the shortwave infrared spectrum. Using the physics engines within the Blender 3-D graphic design software, physical representations of granular soil scenes were created. Each scene characterized a specific particle distribution and density. Chemical and optical properties of pure quartz and magnetite were assigned to particles in the scene based on particle size. This work presents a model to describe an observed phase-angle dependence of beach sand density. Bidirectional reflectance signatures were simulated for targets of varying size distribution and density. This model provides validation for a phenomenological trade space between density and particle size distribution in complex, heterogeneous soil mixtures. It also confirms the suggestion that directional reflectance signatures can be defined by intimate mixtures that depend on pore spacing. The study demonstrated that by combining realistic target geometry and spectral measurements of pure quartz and magnetite, effects of soil particle size and density could be modeled without functional data fitting or rigorous analysis of material dynamics. This research does not use traditional function-based models for simulation. The combination of realistic geometry, physically viable particle structure, and first-principles ray-tracing enables the ability to represent signature changes that have been observed in experimental observations.

  18. Effect of sonication on the particle size of montmorillonite clays.

    PubMed

    Poli, Alessandra L; Batista, Tatiana; Schmitt, Carla C; Gessner, Fergus; Neumann, Miguel G

    2008-09-15

    This paper reports on the effect of sonication on SAz-1 and SWy-1 montmorillonite suspensions. Changes in the size of the particles of these materials and modifications of their properties have been investigated. The variation of the particle size has been analyzed by DLS (dynamic light scattering). In all cases the clay particles show a bimodal distribution. Sonication resulted in a decrease of the larger modal diameter, as well as a reduction of its volume percentage. Simultaneously, the proportion of the smallest particles increases. After 60 min of sonication, SAz-1 presented a very broad particle size distribution with a modal diameter of 283 nm. On the other hand, the SWy-1 sonicated for 60 min presents a bimodal distribution of particles at 140 and 454 nm. Changes in the properties of the clay suspensions due to sonication were evaluated spectroscopically from dye-clay interactions, using Methylene Blue. The acidic sites present in the interlamellar region, which are responsible for dye protonation, disappeared after sonication of the clay. The changes in the size of the scattering particles and the lack of acidic sites after sonication suggest that sonication induces delamination of the clay particles.

  19. Particle size effects in particle-particle triboelectric charging studied with an integrated fluidized bed and electrostatic separator system

    NASA Astrophysics Data System (ADS)

    Bilici, Mihai A.; Toth, Joseph R.; Sankaran, R. Mohan; Lacks, Daniel J.

    2014-10-01

    Fundamental studies of triboelectric charging of granular materials via particle-particle contact are challenging to control and interpret because of foreign material surfaces that are difficult to avoid during contacting and measurement. The measurement of particle charge itself can also induce charging, altering results. Here, we introduce a completely integrated fluidized bed and electrostatic separator system that charges particles solely by interparticle interactions and characterizes their charge on line. Particles are contacted in a free-surface fluidized bed (no reactor walls) with a well-controlled fountain-like flow to regulate particle-particle contact. The charged particles in the fountain are transferred by a pulsed jet of air to the top of a vertically-oriented electrostatic separator consisting of two electrodes at oppositely biased high voltage. The free-falling particles migrate towards the electrodes of opposite charge and are collected by an array of cups where their charge and size can be determined. We carried out experiments on a bidisperse size mixture of soda lime glass particles with systematically varying ratios of concentration. Results show that larger particles fall close to the negative electrode and smaller particles fall close to the positive electrode, consistent with theory and prior experiments that larger particles charge positively and smaller particles charge negatively. The segregation of particles by charge for one of the size components is strongest when its collisions are mostly with particles of the other size component; thus, small particles segregate most strongly to the negative sample when their concentration in the mixture is small (and analogous results occur for the large particles). Furthermore, we find additional size segregation due to granular flow, whereby the fountain becomes enriched in larger particles as the smaller particles are preferentially expelled from the fountain.

  20. Particle size effects in particle-particle triboelectric charging studied with an integrated fluidized bed and electrostatic separator system

    SciTech Connect

    Bilici, Mihai A.; Toth, Joseph R.; Sankaran, R. Mohan; Lacks, Daniel J.

    2014-10-15

    Fundamental studies of triboelectric charging of granular materials via particle-particle contact are challenging to control and interpret because of foreign material surfaces that are difficult to avoid during contacting and measurement. The measurement of particle charge itself can also induce charging, altering results. Here, we introduce a completely integrated fluidized bed and electrostatic separator system that charges particles solely by interparticle interactions and characterizes their charge on line. Particles are contacted in a free-surface fluidized bed (no reactor walls) with a well-controlled fountain-like flow to regulate particle-particle contact. The charged particles in the fountain are transferred by a pulsed jet of air to the top of a vertically-oriented electrostatic separator consisting of two electrodes at oppositely biased high voltage. The free-falling particles migrate towards the electrodes of opposite charge and are collected by an array of cups where their charge and size can be determined. We carried out experiments on a bidisperse size mixture of soda lime glass particles with systematically varying ratios of concentration. Results show that larger particles fall close to the negative electrode and smaller particles fall close to the positive electrode, consistent with theory and prior experiments that larger particles charge positively and smaller particles charge negatively. The segregation of particles by charge for one of the size components is strongest when its collisions are mostly with particles of the other size component; thus, small particles segregate most strongly to the negative sample when their concentration in the mixture is small (and analogous results occur for the large particles). Furthermore, we find additional size segregation due to granular flow, whereby the fountain becomes enriched in larger particles as the smaller particles are preferentially expelled from the fountain.

  1. A comparative study of submicron particle sizing platforms: accuracy, precision and resolution analysis of polydisperse particle size distributions.

    PubMed

    Anderson, Will; Kozak, Darby; Coleman, Victoria A; Jämting, Åsa K; Trau, Matt

    2013-09-01

    The particle size distribution (PSD) of a polydisperse or multimodal system can often be difficult to obtain due to the inherent limitations in established measurement techniques. For this reason, the resolution, accuracy and precision of three new and one established, commercially available and fundamentally different particle size analysis platforms were compared by measuring both individual and a mixed sample of monodisperse, sub-micron (220, 330, and 410 nm - nominal modal size) polystyrene particles. The platforms compared were the qNano Tunable Resistive Pulse Sensor, Nanosight LM10 Particle Tracking Analysis System, the CPS Instruments's UHR24000 Disc Centrifuge, and the routinely used Malvern Zetasizer Nano ZS Dynamic Light Scattering system. All measurements were subjected to a peak detection algorithm so that the detected particle populations could be compared to 'reference' Transmission Electron Microscope measurements of the individual particle samples. Only the Tunable Resistive Pulse Sensor and Disc Centrifuge platforms provided the resolution required to resolve all three particle populations present in the mixed 'multimodal' particle sample. In contrast, the light scattering based Particle Tracking Analysis and Dynamic Light Scattering platforms were only able to detect a single population of particles corresponding to either the largest (410 nm) or smallest (220 nm) particles in the multimodal sample, respectively. When the particle sets were measured separately (monomodal) each platform was able to resolve and accurately obtain a mean particle size within 10% of the Transmission Electron Microscope reference values. However, the broadness of the PSD measured in the monomodal samples deviated greatly, with coefficients of variation being ~2-6-fold larger than the TEM measurements across all four platforms. The large variation in the PSDs obtained from these four, fundamentally different platforms, indicates that great care must still be taken in

  2. Particle size determination of a three-component suspension using a laser-scattering particle size distribution analyzer.

    PubMed

    Toongsuwan, S; Chang, H C; Li, L C; Stephens, D; Plichta-Mahmoud, H

    2000-08-01

    In this study, a rapid and accurate particle size determination method using a light-scattering particle size analyzer was developed to measure the particle size and size distribution of a suspension containing three solid components: clotrimazole, triamcinolone, and sarafloxacin, which have different refractive indices. To ensure that data represent the size distribution of the primary particles of the suspension, the optimal sonication prior to and during measurement was determined. It was found that the results obtained using the average relative refractive index (RRI) of the three components agreed with the results obtained using three individual RRIs. In addition, the results from two analysts demonstrated good reproducibility of this method. The size distribution data of the suspension were also compared to those of the bulk drugs. The results showed that the median particle size of this three-component suspension is relatively close to that of clotrimazole, which accounts for 80% of solid particles in the suspension. Furthermore, the results obtained using the light-scattering technique were comparable to those obtained using a polarized light microscope equipped with an image analyzer, indicating acceptable accuracy of this technique.

  3. Saturn's Rings II. Particle Sizes Inferred from Stellar Occultation Data

    NASA Astrophysics Data System (ADS)

    French, Richard G.; Nicholson, Philip D.

    2000-06-01

    We derive power-law particle size distributions for each of Saturn's main ring regions, using observations of the 3 July 1989 stellar occultation of 28 Sgr from Palomar, McDonald, and Lick observatories. We use the Voyager PPS δ Sco optical depth profile to estimate and then remove the directly transmitted signal from the 28 Sgr observations, leaving high SNR scattered light profiles at wavelengths of 3.9, 2.1, and 0.9 μm. The angular distribution of this diffracted signal depends on the ring particle size distribution: the sharpness of the forward lobe is set by the largest particles, while the overall breadth and amplitude of the scattered signal reflect the abundance of smaller, cm-sized particles. From a simple one-dimensional scattering model, we estimate characteristic particle sizes in the A, B, and C rings, and obtain a good match to the detailed structure of the observed scattered light profiles. To accommodate more realistic particle size distributions and to take proper account of the geometry of the occultation, we then develop a two-dimensional forward-scattering model. We assume for simplicity a single power law particle size distribution for each major ring region, and we determine the index q and lower and upper size cutoffs amin and amax that provide the best match to all three data sets in each region. Our results in the A and C rings are fairly consistent with values of q and amax derived from Voyager radio occultation (RSS) measurements (Zebker et al. 1985). We extend their results by determining lower limits to the particle size distributions and by probing the B Ring. We find a rather flat ( q=2.75) and narrow size distribution for both the inner A Ring and the B Ring, with a surprisingly large amin=30 cm. From the detailed shape of the scattered signal in the A and B rings, we find amax=20 m, a factor of two larger than the RSS result. The fraction of cm-sized particles increases between the inner and outer A Ring and is greatest in the C

  4. Size distributions of manure particles released under simulated rainfall.

    PubMed

    Pachepsky, Yakov A; Guber, Andrey K; Shelton, Daniel R; McCarty, Gregory W

    2009-03-01

    Manure and animal waste deposited on cropland and grazing lands serve as a source of microorganisms, some of which may be pathogenic. These microorganisms are released along with particles of dissolved manure during rainfall events. Relatively little if anything is known about the amounts and sizes of manure particles released during rainfall, that subsequently may serve as carriers, abode, and nutritional source for microorganisms. The objective of this work was to obtain and present the first experimental data on sizes of bovine manure particles released to runoff during simulated rainfall and leached through soil during subsequent infiltration. Experiments were conducted using 200 cm long boxes containing turfgrass soil sod; the boxes were designed so that rates of manure dissolution and subsequent infiltration and runoff could be monitored independently. Dairy manure was applied on the upper portion of boxes. Simulated rainfall (ca. 32.4 mm h(-1)) was applied for 90 min on boxes with stands of either live or dead grass. Electrical conductivity, turbidity, and particle size distributions obtained from laser diffractometry were determined in manure runoff and soil leachate samples. Turbidity of leachates and manure runoff samples decreased exponentially. Turbidity of manure runoff samples was on average 20% less than turbidity of soil leachate samples. Turbidity of leachate samples from boxes with dead grass was on average 30% less than from boxes with live grass. Particle size distributions in manure runoff and leachate suspensions remained remarkably stable after 15 min of runoff initiation, although the turbidity continued to decrease. Particles had the median diameter of 3.8 microm, and 90% of particles were between 0.6 and 17.8 microm. The particle size distributions were not affected by the grass status. Because manure particles are known to affect transport and retention of microbial pathogens in soil, more information needs to be collected about the

  5. Number size distribution of ambient particles in a typical urban site: the first Polish assessment based on long-term (9 months) measurements.

    PubMed

    Klejnowski, Krzysztof; Krasa, Andrzej; Rogula-Kozłowska, Wioletta; Błaszczak, Barbara

    2013-01-01

    This work presents results from the long-term measurements of particle number carried out at an urban background station in Zabrze, Poland. Ambient particles with aerodynamic diameters of between 28 nm and 10 μ m were investigated by means of a DEKATI thirteen-stage electrical low pressure impactor (ELPI). The particle number-size distribution was bimodal, whilst its density function had the local maxima in the aerodynamic diameter intervals 0.056-0.095 μ m and 0.157-0.263 μ m. The average particle number in winter was nearly twice as high as in summer. The greatest number concentrations in winter were those of the particles with diameters of between 0.617 and 2.41 μ m, that is, the anthropogenic particles from fossil fuel combustion. Approximately 99% of the particles observed in Zabrze had aerodynamic diameters ≤ 1 μ m-they may have originated from the combustion of biomass, liquid, and gaseous fuels in domestic stoves or in car engines. The daily variation of particle number was similar for both seasons-the highest values were observed in the morning (traffic rush hour) and in the afternoon/late evening (traffic and house heating emissions). An additional maximum (0.028-0.056 μ m) observed in the early afternoon in summer was due to the intensive formation of new PM particles from gas precursors.

  6. Modeling photoacoustic spectral features of micron-sized particles.

    PubMed

    Strohm, Eric M; Gorelikov, Ivan; Matsuura, Naomi; Kolios, Michael C

    2014-10-07

    The photoacoustic signal generated from particles when irradiated by light is determined by attributes of the particle such as the size, speed of sound, morphology and the optical absorption coefficient. Unique features such as periodically varying minima and maxima are observed throughout the photoacoustic signal power spectrum, where the periodicity depends on these physical attributes. The frequency content of the photoacoustic signals can be used to obtain the physical attributes of unknown particles by comparison to analytical solutions of homogeneous symmetric geometric structures, such as spheres. However, analytical solutions do not exist for irregularly shaped particles, inhomogeneous particles or particles near structures. A finite element model (FEM) was used to simulate photoacoustic wave propagation from four different particle configurations: a homogeneous particle suspended in water, a homogeneous particle on a reflecting boundary, an inhomogeneous particle with an absorbing shell and non-absorbing core, and an irregularly shaped particle such as a red blood cell. Biocompatible perfluorocarbon droplets, 3-5 μm in diameter containing optically absorbing nanoparticles were used as the representative ideal particles, as they are spherical, homogeneous, optically translucent, and have known physical properties. The photoacoustic spectrum of micron-sized single droplets in suspension and on a reflecting boundary were measured over the frequency range of 100-500 MHz and compared directly to analytical models and the FEM. Good agreement between the analytical model, FEM and measured values were observed for a droplet in suspension, where the spectral minima agreed to within a 3.3 MHz standard deviation. For a droplet on a reflecting boundary, spectral features were correctly reproduced using the FEM but not the analytical model. The photoacoustic spectra from other common particle configurations such as particle with an absorbing shell and a

  7. Modeling photoacoustic spectral features of micron-sized particles

    NASA Astrophysics Data System (ADS)

    Strohm, Eric M.; Gorelikov, Ivan; Matsuura, Naomi; Kolios, Michael C.

    2014-10-01

    The photoacoustic signal generated from particles when irradiated by light is determined by attributes of the particle such as the size, speed of sound, morphology and the optical absorption coefficient. Unique features such as periodically varying minima and maxima are observed throughout the photoacoustic signal power spectrum, where the periodicity depends on these physical attributes. The frequency content of the photoacoustic signals can be used to obtain the physical attributes of unknown particles by comparison to analytical solutions of homogeneous symmetric geometric structures, such as spheres. However, analytical solutions do not exist for irregularly shaped particles, inhomogeneous particles or particles near structures. A finite element model (FEM) was used to simulate photoacoustic wave propagation from four different particle configurations: a homogeneous particle suspended in water, a homogeneous particle on a reflecting boundary, an inhomogeneous particle with an absorbing shell and non-absorbing core, and an irregularly shaped particle such as a red blood cell. Biocompatible perfluorocarbon droplets, 3-5 μm in diameter containing optically absorbing nanoparticles were used as the representative ideal particles, as they are spherical, homogeneous, optically translucent, and have known physical properties. The photoacoustic spectrum of micron-sized single droplets in suspension and on a reflecting boundary were measured over the frequency range of 100-500 MHz and compared directly to analytical models and the FEM. Good agreement between the analytical model, FEM and measured values were observed for a droplet in suspension, where the spectral minima agreed to within a 3.3 MHz standard deviation. For a droplet on a reflecting boundary, spectral features were correctly reproduced using the FEM but not the analytical model. The photoacoustic spectra from other common particle configurations such as particle with an absorbing shell and a

  8. The Effect of Particle Size on the Biodistribution of Low-modulus Hydrogel PRINT Particles

    PubMed Central

    Merkel, Timothy J.; Chen, Kai; Jones, Stephen W.; Pandya, Ashish A.; Tian, Shaomin; Napier, Mary E.; Zamboni, William E.; DeSimone, Joseph M.

    2012-01-01

    There is a growing recognition that the deformability of particles used for drug delivery plays a significant role on their biodistribution and circulation profile. Understanding these effects would provide a crucial tool for the rational design of drug delivery systems. While particles resembling red blood cells (RBCs) in size, shape and deformability have extended circulation times and altered biodistribution profiles compared to rigid, but otherwise similar particles, the in vivo behavior of such highly deformable particles of varied size has not been explored. We report the fabrication of a series of discoid, monodisperse, low-modulus hydrogel particles with diameters ranging from 0.8 to 8.9 μm, spanning sizes smaller than and larger than RBCs. We injected these particles into healthy mice, and tracked their concentration in the blood and their distribution into major organs. These deformable particles all demonstrated some hold up in filtration tissues like the lungs and spleen, followed by release back into the circulation, characterized by decreases in particles in these tissues with concomitant increases in particle concentration in blood. Particles similar to red blood cells in size demonstrated longer circulation times, suggesting that this size and shape of deformable particle is uniquely suited to avoid clearance. PMID:22705460

  9. Novel magnetic Fe onion-like fullerene micrometer-sized particles of narrow size distribution

    NASA Astrophysics Data System (ADS)

    Snovski, Ron; Grinblat, Judith; Margel, Shlomo

    2012-01-01

    Magnetic polydivinylbenzene (PDVB)/magnetite micrometer-sized particles of narrow size distribution were prepared by entrapping Fe(CO)5 within the pores of uniform porous PDVB particles, followed by the thermal decomposition of the encapsulated Fe(CO)5 at 300 °C in a sealed cell under inert atmosphere. Magnetic Fe onion-like fullerene micrometer-sized particles of narrow size distribution have been prepared by the thermal decomposition of the PDVB/magnetite magnetic microspheres at 1100 °C under inert atmosphere. The graphitic coating protects the elemental iron particles from oxidation and thereby preserves their very high magnetic moment for at least a year. Characterization of these unique magnetic carbon graphitic particles was also performed.

  10. Aerodynamic performance and particle image velocimetery of piezo actuated biomimetic manduca sexta engineered wings towards the design and application of a flapping wing flight vehicle

    NASA Astrophysics Data System (ADS)

    DeLuca, Anthony M.

    Considerable research and investigation has been conducted on the aerodynamic performance, and the predominate flow physics of the Manduca Sexta size of biomimetically designed and fabricated wings as part of the AFIT FWMAV design project. Despite a burgeoning interest and research into the diverse field of flapping wing flight and biomimicry, the aerodynamics of flapping wing flight remains a nebulous field of science with considerable variance into the theoretical abstractions surrounding aerodynamic mechanisms responsible for aerial performance. Traditional FWMAV flight models assume a form of a quasi-steady approximation of wing aerodynamics based on an infinite wing blade element model (BEM). An accurate estimation of the lift, drag, and side force coefficients is a critical component of autonomous stability and control models. This research focused on two separate experimental avenues into the aerodynamics of AFIT's engineered hawkmoth wings|forces and flow visualization. 1. Six degree of freedom force balance testing, and high speed video analysis was conducted on 30°, 45°, and 60° angle stop wings. A novel, non-intrusive optical tracking algorithm was developed utilizing a combination of a Gaussian Mixture Model (GMM) and ComputerVision (OpenCV) tools to track the wing in motion from multiple cameras. A complete mapping of the wing's kinematic angles as a function of driving amplitude was performed. The stroke angle, elevation angle, and angle of attack were tabulated for all three wings at driving amplitudes ranging from A=0.3 to A=0.6. The wing kinematics together with the force balance data was used to develop several aerodynamic force coefficient models. A combined translational and rotational aerodynamic model predicted lift forces within 10%, and vertical forces within 6%. The total power consumption was calculated for each of the three wings, and a Figure of Merit was calculated for each wing as a general expression of the overall efficiency of

  11. Recovering 3D particle size distributions from 2D sections

    NASA Astrophysics Data System (ADS)

    Cuzzi, Jeffrey N.; Olson, Daniel M.

    2017-03-01

    We discuss different ways to convert observed, apparent particle size distributions from 2D sections (thin sections, SEM maps on planar surfaces, etc.) into true 3D particle size distributions. We give a simple, flexible, and practical method to do this; show which of these techniques gives the most faithful conversions; and provide (online) short computer codes to calculate both 2D-3D recoveries and simulations of 2D observations by random sectioning. The most important systematic bias of 2D sectioning, from the standpoint of most chondrite studies, is an overestimate of the abundance of the larger particles. We show that fairly good recoveries can be achieved from observed size distributions containing 100-300 individual measurements of apparent particle diameter.

  12. Domain and droplet sizes in emulsions stabilized by colloidal particles

    NASA Astrophysics Data System (ADS)

    Frijters, Stefan; Günther, Florian; Harting, Jens

    2014-10-01

    Particle-stabilized emulsions are commonly used in various industrial applications. These emulsions can present in different forms, such as Pickering emulsions or bijels, which can be distinguished by their different topologies and rheology. We numerically investigate the effect of the volume fraction and the uniform wettability of the stabilizing spherical particles in mixtures of two fluids. For this, we use the well-established three-dimensional lattice Boltzmann method, extended to allow for the added colloidal particles with non-neutral wetting properties. We obtain data on the domain sizes in the emulsions by using both structure functions and the Hoshen-Kopelman (HK) algorithm, and we demonstrate that both methods have their own (dis)advantages. We confirm an inverse dependence between the concentration of particles and the average radius of the stabilized droplets. Furthermore, we demonstrate the effect of particles detaching from interfaces on the emulsion properties and domain-size measurements.

  13. Small-size dust particles near Halley's Comet

    NASA Astrophysics Data System (ADS)

    Sagdeev, R. Z.; Evlanov, E. N.; Fomenkova, M. N.; Prilutskii, O. F.; Zubkov, B. V.

    Dust-impact PUMA mass-analyzers aboard the spacecrafts VEGA-1 and VEGA-2 allow to conduct the first direct measurements of mass-spectra of comet Halley's dust envelope particles with masses higher than 10 to the -17th g. The analysis of spectra measured by the PUMA instruments showed that unindentified peaks in this spectra could be associated with very small particles. Detection of small-size particles in the dust envelope of comet Halley agrees with the idea that the comet's nucleus is an interstellar dust aggregate which contains very small particles.

  14. Application of bag sampling technique for particle size distribution measurements.

    PubMed

    Mazaheri, M; Johnson, G R; Morawska, L

    2009-11-01

    Bag sampling techniques can be used to temporarily store the aerosol and therefore provide sufficient time to utilize sensitive but slow instrumental techniques for recording detailed particle size distributions. Laboratory based assessment of the method was conducted to examine size dependant deposition loss coefficients for aerosols held in Velostat bags conforming to a horizontal cylindrical geometry. Deposition losses of NaCl particles in the range of 10 nm to 160 nm were analysed in relation to the bag size, storage time, and sampling flow rate. Results of this study suggest that the bag sampling method is most useful for moderately short sampling periods of about 5 minutes.

  15. Size Dependent Elemental Composition of Road-Associated Particles

    PubMed Central

    McKenzie, Erica R.; Wong, Carol M.; Green, Peter G.; Kayhanian, Masoud; Young, Thomas M.

    2009-01-01

    Stormwater particles often provide transport for metals and other contaminants, however only larger particles are effectively removed by typical best management practices. Fine particles and their associated constituents are more likely to reach receiving waters; this merits further investigation regarding the metal contribution of fine (dp<10 μm) and very fine (dp <1.5 μm) particles. Road associated particles were collected by vacuuming a road surface and by collecting highway stormwater runoff. A cell sorter was employed to sort road associated particles into four size ranges: 0.1–0.3, 0.3–0.5, 0.5–1.0, and 1.0–1.5 μm. These very fine particles, along with six particle size ranges (total range <2–63 μm) separated using a settling column, were analyzed for Al, Mn, Fe, Cr, Ni, Cu, Zn, and Pb using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Enrichment factors (EFs), calculated using Al as a basis to represent crustal contributions, were similar for the vacuumed road dust and the stormwater runoff. Fe and Mn were minimally depleted (0.1x) or near unity for all size ranges (Fe EF range 0.01–3.7; Mn EF range 0.02–10.6). Cr, Ni, Cu, Zn, and Pb were moderately (10x) to considerably (>100x) enriched for most size ranges; these metals were most enriched in the very fine fractions (max EF~4900 in Zn, 0.1–0.3 μm). Based on this preliminary study, a cell sorter is an acceptable means of fractionating aqueous particles of diameter 0.1–1.5 μm. In spite of their minimal relative mass contribution, the very fine particles are environmentally relevant due to their mobility and enrichment in potentially toxic metals.. PMID:18433840

  16. Airborne Particle Size Distribution Measurements at USDOE Fernald

    SciTech Connect

    Harley, N.H.; Chittaporn, P.; Heikkinen, M.; Medora, R.; Merrill, R.

    2003-03-27

    There are no long term measurements of the particle size distribution and concentration of airborne radionuclides at any USDOE facility except Fernald. Yet the determinant of lung dose is the particle size, determining the airway and lower lung deposition. Beginning in 2000, continuous (6 to 8 weeks) measurements of the aerosol particle size distribution have been made with a miniature sampler developed under EMSP. Radon gas decays to a chain of four short lived solid radionuclides that attach immediately to the resident atmospheric aerosol. These in turn decay to long lived polonium 210. Alpha emitting polonium is a tracer for any atmospheric aerosol. Six samplers at Fernald and four at QC sites in New Jersey show a difference in both polonium concentration and size distribution with the winter measurements being higher/larger than summer by almost a factor of two at all locations. EMSP USDOE Contract DE FG07 97ER62522.

  17. Laser anemometer signals: visibility characteristics and application to particle sizing.

    PubMed

    Adrian, R J; Orloff, K L

    1977-03-01

    The signal visibility characteristics of a dual beam laser anemometer operated in a backscatter mode have been investigated both experimentally and analytically. The analysis is based on Mie's electromagnetic scattering theory for spherical particles and is exact within the limitations of the scattering theory. It is shown that the signal visibility is a function of the ratio of the particle diameter to the fringe spacing in a certain, restricted case; but more generally it also depends on the Mie scattering size parameter, refractive index, the illuminating beam polarization, and the size, shape, and location of the light collecting aperture. The character of backscatter signal visibility differs significantly from the forward scatter case, and it is concluded that backscatter measurements of particle diameters using the visibility sizing technique may not always be possible. Restrictions on the forward scatter application of the visibility sizing method are also discussed.

  18. Size segregated ring pattern formation in particle impactors

    NASA Astrophysics Data System (ADS)

    Saylor, J. R.; Fredericks, S. A.

    2016-11-01

    Typical particle impactors consist of a nozzle that directs a particle laden flow onto a plate, and is designed to capture particles greater than a cutoff diameter. Connected in series as a cascade, with each impactor designed to have a progressively smaller cutoff diameter, the particle size distribution can be measured. Typical impactors utilize a nozzle-to-plate distance S that is on the order of one nozzle diameter W, S / W 1 , and give a nominally Gaussian particle deposition pattern on the plate. We explored conditions where S / W < < 1 and observed deposition patterns consisting of very fine rings. Moreover, we found that the ring diameter increased with decreasing particle diameter and the ring thickness increased with particle diameter. These results suggest a potential method for sizing particles by using the mature technology of impactors in a different way. Potential mechanisms for how these ring patterns are formed will be discussed. We note that prior studies have observed conditions where particle deposition patterns exhibited "halos". These halos appear less distinct than the rings we have observed, and it is unclear whether they are related.

  19. Saharan Dust Particle Size And Concentration Distribution In Central Ghana

    NASA Astrophysics Data System (ADS)

    Sunnu, A. K.

    2010-12-01

    A.K. Sunnu*, G. M. Afeti* and F. Resch+ *Department of Mechanical Engineering, Kwame Nkrumah University of Science and Technology (KNUST) Kumasi, Ghana. E-mail: albertsunnu@yahoo.com +Laboratoire Lepi, ISITV-Université du Sud Toulon-Var, 83162 La Valette cedex, France E-mail: resch@univ-tln.fr Keywords: Atmospheric aerosol; Saharan dust; Particle size distributions; Particle concentrations. Abstract The Saharan dust that is transported and deposited over many countries in the West African atmospheric environment (5°N), every year, during the months of November to March, known locally as the Harmattan season, have been studied over a 13-year period, between 1996 and 2009, using a location at Kumasi in central Ghana (6° 40'N, 1° 34'W) as the reference geographical point. The suspended Saharan dust particles were sampled by an optical particle counter, and the particle size distributions and concentrations were analysed. The counter gives the total dust loads as number of particles per unit volume of air. The optical particle counter used did not discriminate the smoke fractions (due to spontaneous bush fires during the dry season) from the Saharan dust. Within the particle size range measured (0.5 μm-25 μm.), the average inter-annual mean particle diameter, number and mass concentrations during the northern winter months of January and February were determined. The average daily number concentrations ranged from 15 particles/cm3 to 63 particles/cm3 with an average of 31 particles/cm3. The average daily mass concentrations ranged from 122 μg/m3 to 1344 μg/m3 with an average of 532 μg/m3. The measured particle concentrations outside the winter period were consistently less than 10 cm-3. The overall dust mean particle diameter, analyzed from the peak representative Harmattan periods over the 13-year period, ranged from 0.89 μm to 2.43 μm with an average of 1.5 μm ± 0.5. The particle size distributions exhibited the typical distribution pattern for

  20. Diffusion of micrometer-sized soft particles in confinement

    NASA Astrophysics Data System (ADS)

    Jordan, Benjamin; Aptowicz, Kevin

    We investigate the diffusion of micrometer sized poly(N-isopropylacrylamide) (PNIPAM) gel particles in confinement. The influence of confinement on the transport of small particles is becoming increasingly important for microfluidics and bio-fluidics. Analytical solutions to this problem are limited to very unique geometries or gross approximations. Computational methods have provided more insight into the problem as well as experimental investigations. However, most research has focused on the hard-sphere problem. In this work, we will explore the diffusion of soft particles in confinement. The dynamics of the particles confined between two parallel walls is captured with video-microscopy. In addition, we use a recently developed technique to measurement confinement of particles in-situ with a precision of 1%. This poster will present some preliminary results of how confinement affects the diffusion of these soft particles. We acknowledge support from Grant DMR-1206231.

  1. Rheology of PVC Plastisol: Particle Size Distribution and Viscoelastic Properties.

    PubMed

    Nakajima, N.; Harrell, E. R.

    2001-06-01

    Plastisols of poly(vinyl chloride), PVC, are suspensions of fine particles in plasticizer with about 50% resin volume fraction. Typically, the gross particle size ranges from 15 to 0.2 &mgr;m and smaller, where the common practice of spray-drying these resins and subsequent grinding of larger particles dictate the size ranges including agglomerates as well as the primary particles. The plastisol is a pastelike liquid, which may be spread to coat substrates. The coated substrates are heated in an oven to gel and fuse the material for producing uniform, rubbery products. Because the first step of processing is spreading the plastisol on a substrate, rheology at room temperature is obviously important. The material is thixotropic under very low stress. The flow behavior is pseudoplastic and exhibits dilatancy and fracture at high shear rate. This work is concerned with the pseudoplastic behavior but the dynamic mechanical measurements are employed instead of the usual steady-state shear flow measurements. This is because the steady shear may break up agglomerates. The dynamic measurements with small strain-amplitude avoid the break-up of the agglomerates. This is important, because this work is concerned with the effects of the particle size distribution on the material behavior. The frequency dependence of both viscous and elastic behavior is recorded and presented with samples varying in particle size distribution. Copyright 2001 Academic Press.

  2. A simple way to measure particle size in fluegases

    SciTech Connect

    Gomes, J.F.P.

    1998-03-01

    The size range of particles found in fluegases from stationary emission sources, such as combustion stacks, is an important process parameter. Particle-size range not only affects plume opacity and dispersion modeling, but it is a key factor in the selection and design of air-pollution-control equipment, such as cyclones, bag filters and electrostatic precipitators. The particle-size distribution of a fluegas stream is also a useful parameter for analyzing the performance efficiency of combustion equipment and particulate-removal systems. While several laboratories use costly, laser-beam techniques to carry out this task, no standard method to date has been developed to determine the size range of particles in stationary sources. This article discusses a method (described in US EPA Method 5) in which particles in gases circulating in a stack are collected isokinetically in a filter. Once collected, the particles are measured using an optical microscope. Despite some limitations, this relatively inexpensive method gives reproducible results in many applications. Several are described.

  3. Turbulent Concentration of mm-Size Particles in the Protoplanetary Nebula: Scale-Dependent Cascades

    NASA Technical Reports Server (NTRS)

    Cuzzi, J. N.; Hartlep, T.

    2015-01-01

    The initial accretion of primitive bodies (here, asteroids in particular) from freely-floating nebula particles remains problematic. Traditional growth-by-sticking models encounter a formidable "meter-size barrier" (or even a mm-to-cm-size barrier) in turbulent nebulae, making the preconditions for so-called "streaming instabilities" difficult to achieve even for so-called "lucky" particles. Even if growth by sticking could somehow breach the meter size barrier, turbulent nebulae present further obstacles through the 1-10km size range. On the other hand, nonturbulent nebulae form large asteroids too quickly to explain long spreads in formation times, or the dearth of melted asteroids. Theoretical understanding of nebula turbulence is itself in flux; recent models of MRI (magnetically-driven) turbulence favor low-or- no-turbulence environments, but purely hydrodynamic turbulence is making a comeback, with two recently discovered mechanisms generating robust turbulence which do not rely on magnetic fields at all. An important clue regarding planetesimal formation is an apparent 100km diameter peak in the pre-depletion, pre-erosion mass distribution of asteroids; scenarios leading directly from independent nebula particulates to large objects of this size, which avoid the problematic m-km size range, could be called "leapfrog" scenarios. The leapfrog scenario we have studied in detail involves formation of dense clumps of aerodynamically selected, typically mm-size particles in turbulence, which can under certain conditions shrink inexorably on 100-1000 orbit timescales and form 10-100km diameter sandpile planetesimals. There is evidence that at least the ordinary chondrite parent bodies were initially composed entirely of a homogeneous mix of such particles. Thus, while they are arcane, turbulent concentration models acting directly on chondrule size particles are worthy of deeper study. The typical sizes of planetesimals and the rate of their formation can be

  4. [Theory and practice of electrospray crystallization in particle size reduction].

    PubMed

    Szunyogh, Tímea; Ambrus, Rita; Szabóné Révész, Piroska

    2015-01-01

    Nowdays, one of the most challenges for the researchers is the formulation of poorly water soluble drugs. Reduction of particle size of active agents to submicron range could result in a faster dissolution rate and higher bioavailability. Integration as crystallization process is an often used particle size decreasing technique. The aim of this study was to show the theoretical background and practical application of the electros pray crystallization as an innovative particle size decreasing technique. Our model drug was the niflumic acid (NIF), which belongs to the BCS Class II. After the optimization of the process parameters, the physico-chemical properties of the samples were characterized. Particle size and shape were visualized by scanning electron microscopy (SEM). Crystalline state of NIF and the samples were investigated using differential scanning calorimetry (DSC) and X-ray powder diffraction. Physico-chemical properties were determined using dissolution test from simulated media. The electrospray crytallization resulted in particle size reduction but the aggregation of nanonized NIF crystals (NIF-nano) could not avoid without excipient. Aggregates with poor secondary forces are suitable for production of the interactive physical mixture. It was found that NIF-nano could be well distributed on the surface of the mannitol as carrier and the Poloxamer R protected the NIF-nano crystals (320 nm)from aggregation. Consequently, the physical mixture resulted in product with higher polarity, better wettability and faster dissolution rate of NIF as raw NIF or NIF-nano.

  5. Particle-Size-Distribution of Nevada Test Site Soils

    SciTech Connect

    Spriggs, G; Ray-Maitra, A

    2007-09-17

    The amount of each size particle in a given soil is called the particle-size distribution (PSD), and the way it feels to the touch is called the soil texture. Sand, silt, and clay are the three particle sizes of mineral material found in soils. Sand is the largest sized particle and it feels gritty; silt is medium sized and it feels floury; and clay is the smallest and if feels sticky. Knowing the particle-size distribution of a soil sample helps to understand many soil properties such as how much water, heat, and nutrients the soil will hold, how fast water and heat will move through the soil, and what kind of structure, bulk density and consistence the soil will have. Furthermore, the native particle-size distribution of the soil in the vicinity of ground zero of a nuclear detonation plays a major role in nuclear fallout. For soils that have a high-sand content, the near-range fallout will be relatively high and the far-range fallout will be relatively light. Whereas, for soils that have a high-silt and high-clay content, the near-range fallout will be significantly lower and the far-range fallout will be significantly higher. As part of a program funded by the Defense Threat Reduction Agency (DTRA), the Lawrence Livermore National Laboratory (LLNL) has recently measured the PSDs from the various major areas at the Nevada Test Site where atmospheric detonations and/or nuclear weapon safety tests were performed back in the 50s and 60s. The purpose of this report is to document those results.

  6. Measurement of non-volatile particle number size distribution

    NASA Astrophysics Data System (ADS)

    Gkatzelis, G. I.; Papanastasiou, D. K.; Florou, K.; Kaltsonoudis, C.; Louvaris, E.; Pandis, S. N.

    2015-06-01

    An experimental methodology was developed to measure the non-volatile particle number concentration using a thermodenuder (TD). The TD was coupled with a high-resolution time-of-flight aerosol mass spectrometer, measuring the chemical composition and mass size distribution of the submicrometer aerosol and a scanning mobility particle sizer (SMPS) that provided the number size distribution of the aerosol in the range from 10 to 500 nm. The method was evaluated with a set of smog chamber experiments and achieved almost complete evaporation (> 98 %) of secondary organic as well as freshly nucleated particles, using a TD temperature of 400 °C and a centerline residence time of 15 s. This experimental approach was applied in a winter field campaign in Athens and provided a direct measurement of number concentration and size distribution for particles emitted from major pollution sources. During periods in which the contribution of biomass burning sources was dominant, more than 80 % of particle number concentration remained after passing through the thermodenuder, suggesting that nearly all biomass burning particles had a non-volatile core. These remaining particles consisted mostly of black carbon (60 % mass contribution) and organic aerosol, OA (40 %). Organics that had not evaporated through the TD were mostly biomass burning OA (BBOA) and oxygenated OA (OOA) as determined from AMS source apportionment analysis. For periods during which traffic contribution was dominant 50-60 % of the particles had a non-volatile core while the rest evaporated at 400 °C. The remaining particle mass consisted mostly of black carbon (BC) with an 80 % contribution, while OA was responsible for another 15-20 %. Organics were mostly hydrocarbon-like OA (HOA) and OOA. These results suggest that even at 400 °C some fraction of the OA does not evaporate from particles emitted from common combustion processes, such as biomass burning and car engines, indicating that a fraction of this type

  7. HDL particle number and size as predictors of cardiovascular disease.

    PubMed

    Kontush, Anatol

    2015-01-01

    Previous studies indicate that reduced concentrations of circulating high-density lipoprotein (HDL) particles can be superior to HDL-cholesterol (HDL-C) levels as a predictor of cardiovascular disease. Measurements of HDL particle numbers, therefore, bear a potential for the improved assessment of cardiovascular risk. Furthermore, such measurement can be relevant for the evaluation of novel therapeutic approaches targeting HDL. Modern in-depth analyses of HDL particle profile may further improve evaluation of cardiovascular risk. Although clinical relevance of circulating concentrations of HDL subpopulations to cardiovascular disease remains controversial, the negative relationship between the number of large HDL particles and cardiovascular disease suggests that assessment of HDL particle profile can be clinically useful. Reduced mean HDL size is equally associated with cardiovascular disease in large-scale clinical studies. Since HDL-C is primarily carried in the circulation by large, lipid-rich HDL particles, the inverse relationship between HDL size and cardiovascular risk can be secondary to those established for plasma levels of HDL particles, HDL-C, and large HDL. The epidemiological data thereby suggest that HDL particle number may represent a more relevant therapeutic target as compared to HDL-C.

  8. From Agglomerates of Spheres to Irregularly Shaped Particles: Determination of Dynamic Shape Factors from Measurements of Mobility and Vacuum Aerodynamic Diameters

    SciTech Connect

    Zelenyuk, Alla; Cai, Yong; Imre, Dan G.

    2006-03-01

    With the advert of aerosol instrumentation it has become possible to simultaneously measure individual particle mobility and vacuum aerodynamic diameters. For spherical particles these two diameters yield individual particle density. In contrast, assigning a physical meaning to the mobility or aerodynamic diameter of aspherical particles is not straightforward. This paper presents an experimental exploration of the effect of particle shape on the relationship between mobility and vacuum aerodynamic diameters. We make measurements on systems of three types: 1) Agglomerates of spheres, for which the density and the volume are known; 2) Ammonium sulfate, sodium chloride, succinic acid and lauric acid irregularly shaped particles of known density; and 3) Internally mixed particles, containing organics and ammonium sulfate, of unknown density and shape. For agglomerates of spheres we observed alignment effects in the DMA and report the first measurements of the dynamic shape factors (DSFs) in free molecular regime. We present here the first experimental determination of the DSF of ammonium sulfate particles. We find for ammonium sulfate particles a DSF that increases from 1.03 to 1.07 as particle mobility diameter increases from 160 nm to 500 nm. Three types of NaC1 particles were generated and characterized: nearly spherical particles with DSF of ~1.02; cubic with DSF that increases from 1.065 to 1.17 as particle mobility diameter increases from 200 nm to 900 nm; and compact agglomerates with DSF 1.3-1.4. Organic particles were found very nearly spherical. The data suggest that particles composed of binary mixtures of ammonium sulfate and succinic acid have lower dynamic shape factors than pure ammonium sulfate particles. However, for internally mixed ammonium sulfate and lauric acid particles we cannot distinguish between nearly spherical particles with low density and particles with DSF of 1.17.

  9. Transport of finite size particles in confined narrow channels: Diffusion, coherence, and particle separation

    NASA Astrophysics Data System (ADS)

    Ai, Bao-Quan; Wu, Jian-Chun

    2013-07-01

    Transport of the finite size spherical Brownian particles is investigated in confined narrow channels with varying cross-section width. Applying the Fick-Jacobs approximation, we obtain the expressions of the particle current, the effective diffusion coefficient, and the coherence level of Brownian transport (the Péclet number). For the case of the biased constant force, the dependencies of the nonlinear mobility, the effective diffusion coefficient, and the Péclet number on the particle size exhibit striking behaviors. The Péclet number decreases with increasing the radius of the particle which shows that the big sizes of the particles reduce the coherence level of Brownian transport. There exists an optimized value of the radius at which the effective diffusion coefficient is maximal. For the case of the asymmetric unbiased force, due to the competition between the spatial asymmetry and the temporal asymmetry, the transport directions of the particles depend very sensitively on the size of the particle. Particles larger than a given threshold radius move to the left, whereas particles smaller than that move to the right. Therefore, one can separate particles of different radii and make them move towards opposite directions.

  10. The Influence of Particle Size on Infrared Reflectance Spectra

    SciTech Connect

    Myers, Tanya L.; Brauer, Carolyn S.; Su, Yin-Fong; Blake, Thomas A.; Johnson, Timothy J.; Richardson, Robert L.

    2014-06-13

    Reflectance spectra of solids are influenced by the absorption coefficient as well as the particle size and morphology. In the infrared, spectral features may be observed as either maxima or minima: in general, the upward-going peaks in the reflectance spectrum result from surface scattering, which are rays that have reflected from the surface without penetration, whereas downward-going peaks result from either absorption or volume scattering, i.e. rays that have penetrated into the sample or refracted into the sample interior and are not reflected. The light signal reflected from solids usually encompasses all these effects which include dependencies on particle size, morphology and sample density. This paper measures the reflectance spectra in the 1.3 – 16 micron range for various bulk materials that have a combination of strong and weak absorption bands in order to understand the effects on the spectral features as a function of the mean grain size of the sample. The bulk materials were ground with a mortar and pestle and then sieved to separate the samples into various size fractions: 0-45, 45-90, 90-180, 180-250, 250-500, and >500 microns. The directional-hemispherical spectra were recorded using a Fourier transform infrared spectrometer equipped with an integrating sphere to measure the reflectance for all of the particle-size fractions. We have studied both organic and inorganic materials, but this paper focuses on inorganic salts, NaNO3 in particular. Our studies clearly show that particle size has an enormous influence on the measured reflectance spectra for bulk materials and that successful identification requires sufficient representative reflectance data so as to include the particle size(s) of interest. Origins of the effects are discussed.

  11. Determining Sizes of Particles in a Flow from DPIV Data

    NASA Technical Reports Server (NTRS)

    Wernet, M. P.; Mielke, A.; Cadambi, J. R.

    2004-01-01

    A proposed method of measuring the size of particles entrained in a flow of a liquid or gas would involve utilization of data from digital particle-image velocimetry (DPIV) of the flow. That is to say, with proper design and operation of a DPIV system, the DPIV data could be processed according to the proposed method to obtain particle sizes in addition to particle velocities. As an additional benefit, one could then compute the mass flux of the entrained particles from the particle sizes and velocities. As in DPIV as practiced heretofore, a pulsed laser beam would be formed into a thin sheet to illuminate a plane of interest in a flow field and the illuminated plane would be observed by means of a charge-coupled device (CCD) camera aimed along a line perpendicular to the illuminated plane. Unlike in DPIV as practiced heretofore, care would be taken to polarize the laser beam so that its electric field would lie in the illuminated plane, for the reason explained in the next paragraph. The proposed method applies, more specifically, to transparent or semitransparent spherical particles that have an index of refraction different from that of the fluid in which they are entrained. The method is based on the established Mie theory, which describes the scattering of light by diffraction, refraction, and specular reflection of light by such particles. In the case of a particle illuminated by polarized light and observed in the arrangement described in the preceding paragraph, the Mie theory shows that the image of the particle on the focal plane of the CCD camera includes two glare spots: one attributable to light reflected toward the camera and one attributable to light refracted toward the camera. The distance between the glare spots is a known function of the size of the particle, the indices of refraction of the particle material, and design parameters of the camera optics. Hence, the size of a particle can be determined from the distance between the glare spots. The

  12. STREAMBED PARTICLE SIZE FROM PEBBLE COUNTS USING VISUALLY ESTIMATED SIZE CLSASES: JUNK OR USEFUL DATA?

    EPA Science Inventory

    In large-scale studies, it is often neither feasible nor necessary to obtain the large samples of 400 particles advocated by many geomorphologists to adequately quantify streambed surface particle-size distributions. Synoptic surveys such as U.S. Environmental Protection Agency...

  13. Investigation of particles size effects in Dissipative Particle Dynamics (DPD) modelling of colloidal suspensions

    NASA Astrophysics Data System (ADS)

    Mai-Duy, N.; Phan-Thien, N.; Khoo, B. C.

    2015-04-01

    In the Dissipative Particle Dynamics (DPD) simulation of suspension, the fluid (solvent) and colloidal particles are replaced by a set of DPD particles and therefore their relative sizes (as measured by their exclusion zones) can affect the maximal packing fraction of the colloidal particles. In this study, we investigate roles of the conservative, dissipative and random forces in this relative size ratio (colloidal/solvent). We propose a mechanism of adjusting the DPD parameters to properly model the solvent phase (the solvent here is supposed to have the same isothermal compressibility to that of water).

  14. Influence of particle size and chemistry on the cloud nucleating properties of aerosols

    NASA Astrophysics Data System (ADS)

    Quinn, P. K.; Bates, T. S.; Coffman, D. J.; Covert, D. S.

    2008-02-01

    The ability of an aerosol particle to act as a cloud condensation nuclei (CCN) is a function of the size of the particle, its composition and mixing state, and the supersaturation of the cloud. In-situ data from field studies provide a means to assess the relative importance of these parameters. During the 2006 Texas Air Quality - Gulf of Mexico Atmospheric Composition and Climate Study (TexAQS-GoMACCS), the NOAA RV Ronald H. Brown encountered a wide variety of aerosol types ranging from marine near the Florida panhandle to urban and industrial in the Houston-Galveston area. These varied sources provided an opportunity to investigate the role of aerosol sources and chemistry in the potential activation of particles to form cloud droplets. Measurements were made of CCN concentrations, aerosol chemical composition in the size range relevant for particle activation in warm clouds, and aerosol size distributions. Variability in aerosol composition was parameterized by the mass fraction of Hydrocarbon-like Organic Aerosol (HOA) for particle diameters less than 200 nm (vacuum aerodynamic). The HOA mass fraction in this size range was lowest for marine aerosol and highest for aerosol sampled close to anthropogenic sources. Combining all data from the experiment reveals that composition (defined by HOA mass fraction) explains 40% of the variance in the critical diameter for particle activation at the instrumental supersaturation (S) of 0.44%. Correlations between HOA mass fraction and aerosol mean diameter show that these two parameters are essentially independent of one another for this data set. We conclude that, based on the variability of the HOA mass fraction observed during TexAQS-GoMACCS, variability in particle composition played a significant role in determining the fraction of particles that could activate to form cloud droplets. Using a simple model based on Köhler theory and the assumption that HOA is insoluble, we estimate the degree to which calculated CCN

  15. Size distribution of airborne particle-bound polybrominated diphenyl ethers and its implications for dry and wet deposition.

    PubMed

    Luo, Pei; Ni, Hong-Gang; Bao, Lian-Jun; Li, Shao-Meng; Zeng, Eddy Y

    2014-12-02

    Size distribution of particles in part dictates the environmental behavior of particle-bound organic pollutants in the atmosphere. The present study was conducted to examine the potential mechanisms responsible for the distribution of organic pollutants in size fractionated particles and their environmental implications, using an e-waste recycling zone in South China as a case study. Size-fractionated atmospheric particles were collected at the heights of 1.5, 5, and 20 m near two residential apartments and analyzed for polybrominated diphenyl ethers (PBDEs). The concentrations of particle-bound ΣPBDE (sum of 18 PBDE congeners) were significantly greater at 5 and 20 m than those at 1.5 m. The size-fractionated distributions of airborne ΣPBDE displayed trimodal peaks in 0.10–0.18, 1.8–3.2, and 10–18 μm at 1.5 m but only an unimodal peak in 1.0–1.8 μm at 20 m height. Emission sources, resuspension of dust and soil, and volatility of PBDEs were important factors influencing the size distribution of particle-bound PBDEs. The dry deposition fluxes of particle-bound PBDE estimated from the measured data in the present study were approximately twice the estimated wet deposition fluxes, with a total deposition flux of 3000 ng m(–2) d(–1). The relative contributions of particles to dry and wet deposition fluxes were also size-dependent, e.g., coarse (aerodynamic diameters (Dp) > 1.8 μm) and fine (Dp < 1.8 μm) particles dominated the dry and wet deposition fluxes of PBDEs, respectively.

  16. Particle sizing in rocket motor studies utilizing hologram image processing

    NASA Technical Reports Server (NTRS)

    Netzer, David; Powers, John

    1987-01-01

    A technique of obtaining particle size information from holograms of combustion products is described. The holograms are obtained with a pulsed ruby laser through windows in a combustion chamber. The reconstruction is done with a krypton laser with the real image being viewed through a microscope. The particle size information is measured with a Quantimet 720 image processing system which can discriminate various features and perform measurements of the portions of interest in the image. Various problems that arise in the technique are discussed, especially those that are a consequence of the speckle due to the diffuse illumination used in the recording process.

  17. Critical Bottleneck Size for Jamless Particle Flows in Two Dimensions

    NASA Astrophysics Data System (ADS)

    Masuda, Takumi; Nishinari, Katsuhiro; Schadschneider, Andreas

    2014-04-01

    We propose a simple microscopic model for arching phenomena at bottlenecks. The dynamics of particles in front of a bottleneck is described by a one-dimensional stochastic cellular automaton on a semicircular geometry. The model reproduces oscillation phenomena due to the formation and collapsing of arches. It predicts the existence of a critical bottleneck size for continuous particle flows. The dependence of the jamming probability on the system size is approximated by the Gompertz function. The analytical results are in good agreement with simulations.

  18. Rock sampling. [method for controlling particle size distribution

    NASA Technical Reports Server (NTRS)

    Blum, P. (Inventor)

    1971-01-01

    A method for sampling rock and other brittle materials and for controlling resultant particle sizes is described. The method involves cutting grooves in the rock surface to provide a grouping of parallel ridges and subsequently machining the ridges to provide a powder specimen. The machining step may comprise milling, drilling, lathe cutting or the like; but a planing step is advantageous. Control of the particle size distribution is effected primarily by changing the height and width of these ridges. This control exceeds that obtainable by conventional grinding.

  19. Turbulent Concentration of MM-Size Particles in the Protoplanetary Nebula: Scaled-Dependent Multiplier Functions

    NASA Technical Reports Server (NTRS)

    Cuzzi, Jeffrey N.; Hartlep, Thomas; Weston, B.; Estremera, Shariff Kareem

    2014-01-01

    The initial accretion of primitive bodies (asteroids and TNOs) from freely-floating nebula particles remains problematic. Here we focus on the asteroids where constituent particle (read "chondrule") sizes are observationally known; similar arguments will hold for TNOs, but the constituent particles in those regions will be smaller, or will be fluffy aggregates, and are unobserved. Traditional growth-bysticking models encounter a formidable "meter-size barrier" [1] (or even a mm-cm-size barrier [2]) in turbulent nebulae, while nonturbulent nebulae form large asteroids too quickly to explain long spreads in formation times, or the dearth of melted asteroids [3]. Even if growth by sticking could somehow breach the meter size barrier, other obstacles are encountered through the 1-10km size range [4]. Another clue regarding planetesimal formation is an apparent 100km diameter peak in the pre-depletion, pre-erosion mass distribution of asteroids [5]; scenarios leading directly from independent nebula particulates to this size, which avoid the problematic m-km size range, could be called "leapfrog" scenarios [6-8]. The leapfrog scenario we have studied in detail involves formation of dense clumps of aerodynamically selected, typically mm-size particles in turbulence, which can under certain conditions shrink inexorably on 100-1000 orbit timescales and form 10-100km diameter sandpile planetesimals. The typical sizes of planetesimals and the rate of their formation [7,8] are determined by a statistical model with properties inferred from large numerical simulations of turbulence [9]. Nebula turbulence can be described by its Reynolds number Re = L/eta sup(4/3), where L = ETA alpha sup (1/2) the largest eddy scale, H is the nebula gas vertical scale height, and a the nebula turbulent viscosity parameter, and ? is the Kolmogorov or smallest scale in turbulence (typically about 1km), with eddy turnover time t?. In the nebula, Re is far larger than any numerical simulation can

  20. Saharan Dust: Particle Size Distributions and Light Absorption From Measurements During PRIDE and AEROCE

    NASA Astrophysics Data System (ADS)

    Savoie, D. L.; Maring, H. B.

    2001-12-01

    During July 2000, the Office of Naval Reseach and NASA co-sponsored the Puerto Rican Dust Experiment (PRIDE) to assess the physical and optical properties of Saharan dust over the western Atlantic. Numerous aerosol characterization instruments were deployed on Isla Cabras (18.21 N, 65.60 W) in the Roosevelt Roads Naval Station at the eastern end of Puerto Rico. As part of AEROCE (Atmosphere/Ocean Chemistry Experiment), we had previously made similar measurements over the eastern Atlantic at Izana, Tenerife, Canary Islands (28.30 N, 16.48 W). Instrumentation included a TSI APS33 aerodynamic particle sizer, a Ruprecht and Patashnick Tapered Element Oscillating Microbalance (TEOM), and a Radiance Research particle soot absorption photometer (PSAP). At the same locations, daily, high-volume, bulk aerosol samples were collected and analyzed for mineral dust, sea-salt, nitrate, sulfate, and ammonium and for aerosol light absorption (every 10 nm from 300 to 1100 nm via total diffuse reflectance measurements). With the concurrent aerosol chemistry, variations in the in-situ aerosol physical and optical properties can be linked to variations in the concentrations of particles from specific sources. High concentrations of Saharan dust were present at Izana during the last half of July 1995. The APS data at Izana are almost exclusively from dust as there is no sea-salt at this free troposphere site. We used the measured particle size distributions for high dust periods from this campaign to establish an average dust size distribution. Because of the nearly zero correlation between sea-salt and dust, the APS size distributions during PRIDE could be reasonably well resolved between these two components. In contrast to the situation at Izana, there were virtually no particles larger than 10 um geometric diameter at Puerto Rico. Progressively lesser fractions of particles were lost between the eastern and western Atlantic as the particle size decreased. With the natural

  1. Particle Size Distribution in Saturn’s Ring C

    NASA Astrophysics Data System (ADS)

    Marouf, Essam A.; Wong, K.; French, R.; Rappaport, N.

    2012-10-01

    Information about particle sizes in Saturn’s rings is provided by two complementary types of Cassini radio occultation measurements. The first is differential extinction of three coherent sinusoidal signals transmitted by Cassini through the rings back to Earth (wavelength = 0.94, 3.6, and 13 cm, respectively). The differential measurements strongly constraint three parameters of an assumed power-law size distribution n(a) = n0 (a/a0)q, amin ≤ a ≤ amax: namely, the power law index q, the minimum radius amin, and reference abundance n0 at reference radius a0. The differential measurements are particularly sensitive to radii in the range 0.1 mm < a < 1 m. Complementing this capability, is a second type of measurements that is particularly sensitive to the larger radii 1 m < a < 20 m and their abundance. Signature of the collective near-forward scattering by these particles is captured in power spectrum measurements as broadened component of width, shape, and strength that depend on ring particle sizes, their spatial distribution, and observation geometry. Contributions of ring features of width as small several hundred kilometers can be identified and isolated in the measured spectra for a small subset of Cassini orbits of favorable geometry. We use three inverse scattering algorithms (Bayes, constrained linear inversion, generalized singular-value-decomposition) to recover the size distribution of particles of resolved ring features over the size range 1 m < a < 20 m without assuming an explicit size distribution model. We also investigate consistency of the results with a single power-law model extending over 0.1 mm < a < 20 m and implications to the spatial distribution of ring particles normal to the ring plane (vertical ring thickness). We present example results for selected features across Saturn’s Ring C where little evidence for gravitational wakes is present, hence the approaches above are applicable.

  2. Experimental effects on IR reflectance spectra: particle size and morphology

    NASA Astrophysics Data System (ADS)

    Beiswenger, Toya N.; Myers, Tanya L.; Brauer, Carolyn S.; Su, Yin-Fong; Blake, Thomas A.; Ertel, Alyssa B.; Tonkyn, Russell G.; Szecsody, James E.; Johnson, Timothy J.; Smith, Milton O.; Lanker, Cory L.

    2016-05-01

    For geologic and extraterrestrial samples it is known that both particle size and morphology can have strong effects on a species' infrared reflectance spectra. Due to such effects, the reflectance spectra cannot be predicted from the absorption coefficients alone. This is because reflectance is both a surface as well as a bulk phenomenon, incorporating both dispersion as well as absorption effects. The same spectral feature can even be observed as either a maximum or minimum. The complex effects depend on particle size and preparation, as well as the relative amplitudes of the optical constants n and k, i.e. the real and imaginary components of the complex refractive index. While somewhat oversimplified, upward-going amplitude in the reflectance spectrum usually results from surface scattering, i.e. rays that have been reflected from the surface without penetration, whereas downward-going peaks are due to either absorption or volume scattering, i.e. rays that have penetrated or refracted into the sample interior and are not reflected. While the effects are known, we report seminal measurements of reflectance along with quantified particle size of the samples, the sizing obtained from optical microscopy measurements. The size measurements are correlated with the reflectance spectra in the 1.3 - 16 micron range for various bulk materials that have a combination of strong and weak absorption bands in order to understand the effects on the spectral features as a function of the mean grain size. We report results for both anhydrous sodium sulfate Na2SO4 as well as ammonium sulfate (NH4)2SO4; the optical constants have been measured for (NH4)2SO4. To go a step further from the laboratory and into the field we explore our understanding of particle size effects on reflectance spectra using standoff detection at distances of up to 160 meters in a field experiment. The studies have shown that particle size has a strong influence on the measured reflectance spectra of such

  3. Experimental Effects on IR Reflectance Spectra: Particle Size and Morphology

    SciTech Connect

    Beiswenger, Toya N.; Myers, Tanya L.; Brauer, Carolyn S.; Su, Yin-Fong; Blake, Thomas A.; Ertel, Alyssa B.; Tonkyn, Russell G.; Szecsody, James E.; Johnson, Timothy J.; Smith, Milton; Lanker, Cory

    2016-05-23

    For geologic and extraterrestrial samples it is known that both particle size and morphology can have strong effects on the species’ infrared reflectance spectra. Due to such effects, the reflectance spectra cannot be predicted from the absorption coefficients alone. This is because reflectance is both a surface as well as a bulk phenomenon, incorporating both dispersion as well as absorption effects. The same spectral features can even be observed as either a maximum or minimum. The complex effects depend on particle size and preparation, as well as the relative amplitudes of the optical constants n and k, i.e. the real and imaginary components of the complex refractive index. While somewhat oversimplified, upward-going amplitude in the reflectance spectrum usually result from surface scattering, i.e. rays that have been reflected from the surface without penetration, whereas downward-going peaks are due to either absorption or volume scattering, i.e. rays that have penetrated or refracted into the sample interior and are not reflected. While the effects are well known, we report seminal measurements of reflectance along with quantified particle size of the samples, the sizing obtained from optical microscopy measurements. The size measurements are correlated with the reflectance spectra in the 1.3 – 16 micron range for various bulk materials that have a combination of strong and weak absorption bands in order to understand the effects on the spectral features as a function of the mean grain size of the sample. We report results for both sodium sulfate Na2SO4 as well as ammonium sulfate (NH4)2SO4; the optical constants have been measured for (NH4)2SO4. To go a step further from the field to the laboratory we explore our understanding of particle size effects on reflectance spectra in the field using standoff detection. This has helped identify weaknesses and strengths in detection using standoff distances of up 160 meters away from the Target. The studies have

  4. Effects of Size Polydispersity on Pharmaceutical Particle Packings

    NASA Astrophysics Data System (ADS)

    Dutt, Meenakshi; Hancock, Bruno; Bentham, Craig; Elliott, James

    2005-03-01

    Pharmaceutical powder blends are multicomponent mixtures of excipients and the drug powder particles which have irregular shapes with equivalent diameters typically ranging from 40 microns to 300 microns. We consider idealizations of such systems with emphasis on the size dispersity in a pure excipient powder comprised of spherical particles. We study the characteristics of the particle packings generated through gravitational compaction followed by uniaxial compaction via Discrete Element Method simulations (Dutt et al., 2004 to be published). We present results for two common excipients: microcrystalline cellulose (MCC) and sucrose. For each excipient, we vary the degree of dispersity in the diameters of the particles. For insight into the geometrical characteristics of the particle packings, we calculate the coordination number, packing fraction, radial distribution functions and contact angle distributions for the various mixtures. The evolution of the force and stress distributions along with the stress-strain relations are calculated for each system. We discuss comparisons of these quantities for systems with different size dispersity and material properties. For MCC and sucrose mixtures with narrow size distributions (195-225 microns, 170-260 microns), the average packing fraction and coordination number prior to and after uniaxial compaction decreases with interparticle friction, in agreement with results for monodisperse spheres (Silbert et al., Phys. Rev. E (2002)).

  5. Online submicron particle sizing by dynamic light scattering using autodilution

    NASA Technical Reports Server (NTRS)

    Nicoli, David F.; Elings, V. B.

    1989-01-01

    Efficient production of a wide range of commercial products based on submicron colloidal dispersions would benefit from instrumentation for online particle sizing, permitting real time monitoring and control of the particle size distribution. Recent advances in the technology of dynamic light scattering (DLS), especially improvements in algorithms for inversion of the intensity autocorrelation function, have made it ideally suited to the measurement of simple particle size distributions in the difficult submicron region. Crucial to the success of an online DSL based instrument is a simple mechanism for automatically sampling and diluting the starting concentrated sample suspension, yielding a final concentration which is optimal for the light scattering measurement. A proprietary method and apparatus was developed for performing this function, designed to be used with a DLS based particle sizing instrument. A PC/AT computer is used as a smart controller for the valves in the sampler diluter, as well as an input-output communicator, video display and data storage device. Quantitative results are presented for a latex suspension and an oil-in-water emulsion.

  6. Vacuum probe sampler removes micron-sized particles from surfaces

    NASA Technical Reports Server (NTRS)

    Whitfield, W. J.

    1968-01-01

    Vacuum probe sampler removes micron-sized particles from sensitive surfaces, without damage to the surface. The probe has a critical orifice to ensure an optimum airflow rate that disturbs the boundary layer of air and raises bacteria from the surface into the probe with the moving air stream.

  7. Effective particle sizes of cohesive sediment in north Mississippi streams

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Knowledge of the size of cohesive sediment particles transported in streams is important information for predicting how the sediment and contaminants the sediment may be carrying will be transported by the flow. Cohesive sediments (less than 0.062 mm in diameter) generally are not transported in th...

  8. AIRBORNE PARTICLE SIZES AND SOURCES FOUND IN INDOOR AIR

    EPA Science Inventory

    The paper summarizes results of a literature search into the sources, sizes, and concentrations of particles in indoor air, including the various types: plant, animal, mineral, combustion, home/personal care, and radioactive aerosols. This information, presented in a summary figu...

  9. Particle size related bacterial recovery in immunomagnetic separation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Magnetic nanoparticles (MNPs) have demonstrated superior capture efficiencies in small molecule targets during immunomagnetic separation (IMS), but the potentials of MNPs in bacterial isolation have not been verified. The objective of this study was to evaluate the effect of magnetic particle size o...

  10. Evolution of particle size in turbid discharge plumes

    DTIC Science & Technology

    2016-06-07

    Evolution of particle size in turbid discharge plumes Paul S. Hill Department of Oceanography Dalhousie University Halifax, Nova Scotia, CANADA B3H...ES) Dalhousie University,Department of Oceanography,Halifax, Nova Scotia B3H 4J1, Canada, 8. PERFORMING ORGANIZATION REPORT NUMBER 9. SPONSORING

  11. Particle size distributions in and exhausted from a poultry house

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Here we describe a study looking at the full particulate size range of particles in a poultry house. Agricultural particulates are typically thought of as coarse mode dust. But recent emphasis of PM2.5 regulations on pre-cursors such as ammonia and volatile organic compounds increasingly makes it ne...

  12. Ham particle size influences saltiness perception in flans.

    PubMed

    Emorine, M; Septier, C; Thomas-Danguin, T; Salles, C

    2014-04-01

    One major issue of the food industry is reducing sodium content while maintaining food acceptability and liking. Despite extensive research in this field, little has been published on real complex food products. The aim of this study was to investigate whether the size of particles, a parameter easily adjusted in food processing, could influence the salty taste of low-salt food product. We thus evaluated the effect of ham particle sizes (4 levels, including a zero level) on salt perception and the consumer liking of flans varying in their overall salt concentrations (low- and high-salt content). Two consumer panels, composed of 107 and 77 subjects, rated, respectively, the saltiness of and liking for the developed flans (8 samples). The outcomes of this study indicated first, that the addition of ham to flans increased the salty taste perception and second, that a decrease in ham particle size (ground ham) increased the perceived saltiness. Moreover, low- and high-salt flans were equally liked, demonstrating that food manufacturers could reduce the salt contents (here, by over 15%) while maintaining consumer acceptability through the manipulation of the size of the salt-providing particles.

  13. Tracing Particle Size Distribution Curves Using an Analogue Circuit.

    ERIC Educational Resources Information Center

    Bisschop, F. De; Segaert, O.

    1986-01-01

    Proposes an analog circuit for use in sedimentation analysis of finely divided solid materials. Discusses a method of particle size distribution analysis and provides schematics of the circuit with list of components as well as a discussion about the operation of the circuit. (JM)

  14. Comparison of ice particle size variations across Ganymede and Callisto

    NASA Astrophysics Data System (ADS)

    Stephan, Katrin; Hoffmann, Harald; Hibbitts, Karl; Wagner, Roland; Jaumann, Ralf

    2016-04-01

    Ratios of band depths of different H2O ice absorptions as measured by the Near Infrared Spectrometer NIMS onboard the Galileo spacecraft [1] have been found to be semi-quantitative indicator of changes in the particle size of ice across the surfaces of the Jovian satellite Ganymede [2]. This method is now applied to Ganymede's neighboring satellite Callisto. On Ganymede, sizes reach from 1 μm near the poles to 1 mm near the equator [2]. Smallest particles occur at latitudes higher than ±30° where the closed magnetic field lines of Ganymede's magnetic field change into open ones and Ganymede's polar caps become apparent. Thus, the formation of these polar caps has often been attributed to brightening effects due to plasma bombardment of the surface [3,4]. Callisto, which does not exhibit an intrinsic magnetic field, however, also shows the same trend as observed on Ganymede with slightly larger particle sizes on Callisto than on Ganymede at low and mid latitude but similar particle sizes in the polar regions. Similar trends in the particle size variations on Callisto and on Ganymede imply that these variations are caused by similar surface processes. Our measurements rather point to a continuous decreasing of ice particle sizes toward the poles on both satellites related to changes of the surface temperatures [5]. Maximum temperatures during the day reach 150 K and 165 K near the equator of Ganymede and Callisto [6, 7], respectively and sublimation of ice particles and crystal growth [8] is expected to be the dominant surface process in these regions. In contrast, polar temperatures do not exceed 80 ± 5 K [5]. Larger particles in the equatorial region of Callisto than on Ganymede could be explained due to the slight higher maximum temperature but also a longer Callistoan day (Callisto: ~ 17 Earth days; Ganymede: ~ 7 Earth days). References: [1] Carlson et al.. (1999) Science 274, 385-388, 1996; [2] Stephan et al., 2009, EPSC, Abstract #EPSC2009-633; [3] Johnson

  15. Entropic control of particle sizes during viral self-assembly

    NASA Astrophysics Data System (ADS)

    Castelnovo, M.; Muriaux, D.; Faivre-Moskalenko, C.

    2013-03-01

    Morphologic diversity is observed across all families of viruses. However, these supra-molecular assemblies are produced most of the time in a spontaneous way through complex molecular self-assembly scenarios. The modeling of these phenomena remains a challenging problem within the emerging field of physical virology. We present in this work a theoretical analysis aiming at highlighting the particular role of configuration entropy in the control of viral particle size distribution. Specializing this model to retroviruses such as HIV-1, we predict a new mechanism of entropic control of both RNA uptake into the viral particle and of the particle's size distribution. Evidence of this peculiar behavior has recently been reported experimentally.

  16. Evolution of Particle Size Distributions in Fragmentation Over Time

    NASA Astrophysics Data System (ADS)

    Charalambous, C. A.; Pike, W. T.

    2013-12-01

    We present a new model of fragmentation based on a probabilistic calculation of the repeated fracture of a particle population. The resulting continuous solution, which is in closed form, gives the evolution of fragmentation products from an initial block, through a scale-invariant power-law relationship to a final comminuted powder. Models for the fragmentation of particles have been developed separately in mainly two different disciplines: the continuous integro-differential equations of batch mineral grinding (Reid, 1965) and the fractal analysis of geophysics (Turcotte, 1986) based on a discrete model with a single probability of fracture. The first gives a time-dependent development of the particle-size distribution, but has resisted a closed-form solution, while the latter leads to the scale-invariant power laws, but with no time dependence. Bird (2009) recently introduced a bridge between these two approaches with a step-wise iterative calculation of the fragmentation products. The development of the particle-size distribution occurs with discrete steps: during each fragmentation event, the particles will repeatedly fracture probabilistically, cascading down the length scales to a final size distribution reached after all particles have failed to further fragment. We have identified this process as the equivalent to a sequence of trials for each particle with a fixed probability of fragmentation. Although the resulting distribution is discrete, it can be reformulated as a continuous distribution in maturity over time and particle size. In our model, Turcotte's power-law distribution emerges at a unique maturation index that defines a regime boundary. Up to this index, the fragmentation is in an erosional regime with the initial particle size setting the scaling. Fragmentation beyond this index is in a regime of comminution with rebreakage of the particles down to the size limit of fracture. The maturation index can increment continuously, for example under

  17. Pharmacokinetics of inhaled monodisperse beclomethasone as a function of particle size

    PubMed Central

    Esposito-Festen, J E; Zanen, P; Tiddens, H A W M; Lammers, J-W J

    2007-01-01

    What is already known about this subject For asthmatic adults, bronchodilators with a MMAD between 3 and 6 µm were shown to give the best improvement in lung function and the least systemic side-effects. It is not known, however, what is the most efficacious particle size for inhaled steroids in asthmatic adults. Clinical efficacy and systemic side-effects of inhaled steroids should be measured to define the optimal particle size. What this study adds Our study investigated the systemic absorption of inhaled steroids. We found that a particle size of 2.5 µm and 4.5 µm gave a higher pulmonary bioavailability compared with the 1.5 µm monodisperse aerosols in adults with mild asthma and therefore were more likely to elicit systemic adverse effects. Aims For optimal efficacy, antiasthma drugs should be delivered to the desired region in the airways. To date, the optimal particle size for steroids in adults is not known. The aim of the study was to evaluate the pulmonary bioavailability for inhaled beclomethasone dipropionate (BDP) aerosols of different particle sizes. Methods In a randomized single-blind crossover trial, 10 mild asthmatic patients inhaled monodisperse BDP aerosols with mass median aerodynamic diameters (MMADs) of 1.5, 2.5 and 4.5 µm. Gastrointestinal absorption was blocked by activated charcoal. Plasma concentrations of 17-beclomethasone monopropionate (17-BMP) were measured by liquid chromatography plus mass spectrometry. Results Aerosols with MMADs of 1.5 µm, 2.5 µm, and 4.5 µm gave mean maximum concentrations (Cmax) of 17-BMP of 475 pg ml−1, 1300 pg ml−1, and 1161 pg ml−1, respectively. The area under the curve (AUC) values of 17-BMP for MMADs of 1.5 µm, 2.5 µm, and 4.5 µm were 825 pg ml−1 h, 2629 pg ml−1 h, and 2276 pg ml−1 h, respectively. The mean terminal half-time of 17-BMP for all three aerosol sizes was around 1.5 h. Conclusions Monodisperse BDP aerosols with a MMAD of 1.5 µm gave two-three fold lower values for Cmax

  18. Ultrasonic cavitation for obtainment of nanometric sized particles

    NASA Astrophysics Data System (ADS)

    Santos, A.; Guzmán, R.; Espinosa, J.; Estrada, J.

    2016-02-01

    This project aims to determine the possibility of obtaining nanometric size particles of aluminium oxide (Al2O3) and titanium dioxide (TiO2) from commercial micron-sized powders, through the physical principle of ultrasonic cavitation, in order to be used as supply material in coatings made through a process of thermal spray by flame. The tests are performed on a Hielscher UIP 1000hd Ultrasonics equipment, in a 20 micron wave amplitude and in times of 6, 8, 12, 18 and 24 hours. The determination of the particle size is done through image processing using ImageJ software, obtained by the technique of scanning electron microscopy (SEM); while the elemental composition of the processed samples is analyzed through the technique of energy dispersing spectroscopy (EDS). The results show that Al2O3 and TiO2 have a reduction behaviour of the particles size after being subjected to ultrasonic cavitation, however is only reached the nanometric size in the TiO2 samples.

  19. Determination of particle size distributions from acoustic wave propagation measurements

    SciTech Connect

    Spelt, P.D.; Norato, M.A.; Sangani, A.S.; Tavlarides, L.L.

    1999-05-01

    The wave equations for the interior and exterior of the particles are ensemble averaged and combined with an analysis by Allegra and Hawley [J. Acoust. Soc. Am. {bold 51}, 1545 (1972)] for the interaction of a single particle with the incident wave to determine the phase speed and attenuation of sound waves propagating through dilute slurries. The theory is shown to compare very well with the measured attenuation. The inverse problem, i.e., the problem of determining the particle size distribution given the attenuation as a function of frequency, is examined using regularization techniques that have been successful for bubbly liquids. It is shown that, unlike the bubbly liquids, the success of solving the inverse problem is limited since it depends strongly on the nature of particles and the frequency range used in inverse calculations. {copyright} {ital 1999 American Institute of Physics.}

  20. Diffusion of finite-size particles in confined geometries.

    PubMed

    Bruna, Maria; Chapman, S Jonathan

    2014-04-01

    The diffusion of finite-size hard-core interacting particles in two- or three-dimensional confined domains is considered in the limit that the confinement dimensions become comparable to the particle's dimensions. The result is a nonlinear diffusion equation for the one-particle probability density function, with an overall collective diffusion that depends on both the excluded-volume and the narrow confinement. By including both these effects, the equation is able to interpolate between severe confinement (for example, single-file diffusion) and unconfined diffusion. Numerical solutions of both the effective nonlinear diffusion equation and the stochastic particle system are presented and compared. As an application, the case of diffusion under a ratchet potential is considered, and the change in transport properties due to excluded-volume and confinement effects is examined.

  1. A simultaneous charge and size measurement method for individual airborne particles using digital holographic particle imaging

    NASA Astrophysics Data System (ADS)

    Hammond, Adam; Dou, Zhongwang; Liang, Zach; Meng, Hui

    2016-11-01

    Recently, significant inquiry to understand the effects of particle charge on particle laden flow have been made, particularly in the study of Lagrangian particle-pair statistics. Quantification of individual particle charge allows relation of inter-particle electric forces and turbulence-induced forces. Here we offer a simultaneous, individual particle charge and size measurement technique utilizing in-line digital holographic Particle Tracking Velocimetry (hPTV). The method measures particle electric mobility through its velocity response within a uniform electric field using a sequence of holograms, next the particle diameter is measured with the same holograms using a matched-filter developed by Lu et al. (2012) as an input for calculation of charge. Consequently, a benefit of this method is that particle charge is calculated on the individual level, versus a mean charge calculated from a group of particles, offering improved estimations of charge distributions for studies of particle laden flow. This work was supported by NSF CBET-0967407 and CBET-0967349.

  2. Mixing state of regionally transported soot particles and the coating effect on their size and shape at a mountain site in Japan

    NASA Astrophysics Data System (ADS)

    Adachi, Kouji; Zaizen, Yuji; Kajino, Mizuo; Igarashi, Yasuhito

    2014-05-01

    Soot particles influence the global climate through interactions with sunlight. A coating on soot particles increases their light absorption by increasing their absorption cross section and cloud condensation nuclei activity when mixed with other hygroscopic aerosol components. Therefore, it is important to understand how soot internally mixes with other materials to accurately simulate its effects in climate models. In this study, we used a transmission electron microscope (TEM) with an auto particle analysis system, which enables more particles to be analyzed than a conventional TEM. Using the TEM, soot particle size and shape (shape factor) were determined with and without coating from samples collected at a remote mountain site in Japan. The results indicate that ~10% of aerosol particles between 60 and 350 nm in aerodynamic diameters contain or consist of soot particles and ~75% of soot particles were internally mixed with nonvolatile ammonium sulfate or other materials. In contrast to an assumption that coatings change soot shape, both internally and externally mixed soot particles had similar shape and size distributions. Larger aerosol particles had higher soot mixing ratios, i.e., more than 40% of aerosol particles with diameters >1 µm had soot inclusions, whereas <20% of aerosol particles with diameters <1 µm included soot. Our results suggest that climate models may use the same size distributions and shapes for both internally and externally mixed soot; however, changing the soot mixing ratios in the different aerosol size bins is necessary.

  3. Relationship between regolith particle size and porosity on small bodies

    NASA Astrophysics Data System (ADS)

    Kiuchi, M.; Nakamura, A.

    2014-07-01

    Small planetary bodies are covered by a particle layer called the regolith. The particle size and porosity of the regolith surface of the small bodies are important physical properties. The responses of the surface to solar irradiation depend on the particle size and porosity. The particle size and porosity have influences on the dynamic responses of the surface, such as cratering efficiency. In previous studies, these two quantities were measured or estimated by various methods. Here we propose a semi-empirical relationship between the particle size and porosity for small bodies' surfaces. An empirical relationship between the porosity of granular materials in loose packing state under 1G and the ratio of the magnitudes of the interparticle force and gravity which act on a particle was presented in a previous study [1]. In this study, we assume that the van der Waals force F_{V} is predominant in the interparticle forces and adopt a model formula [2] which is different from that adopted in the previous study [1]: F_{V} = {AS^{2}}/{48Ω ^{2}}r, where A is the Hamaker constant, r is the particle radius, Ω is the diameter of an O^{-2} ion, and S is the cleanliness ratio which shows the smallness of a number of the adsorbate molecules [2]. It was shown that the cleanliness ratio S is approximately 0.1 on the Earth, and is almost unity in the interplanetary space. In addition to the data of the several previous studies, our own measurement result for micron-sized fly-ash particles in atmospheric conditions is used in the present analysis. We calculate F_{V} using Eq. (1), and obtain a relationship between porosity and the ratio R_{F} = F_{V}/F_{g}, where F_{g} is gravity. An empirical formula used in the previous study [1], p = p_{0}+(1-p_{0})exp(-m{R_{F}}^{-n}), is applied to fit the data, where p is the porosity and p_{0}, m and n are constants. We assume that p_{0} is 0.36. By substituting Eq. (1) to Eq. 2, we obtain p = p_{0}+(1-p_{0})exp {-m({AS^{2}}/{64πΩ ^{2

  4. Particle size dependent rheological property in magnetic fluid

    NASA Astrophysics Data System (ADS)

    Wu, Jie; Pei, Lei; Xuan, Shouhu; Yan, Qifan; Gong, Xinglong

    2016-06-01

    The influence of the particle size on the rheological property of magnetic fluid was studied both by the experimental and computer simulation methods. Firstly, the magnetic fluids were prepared by dispersing Fe3O4 nanospheres with size varied from 40 nm to 100 nm and 200 nm in the solution. Then, the rheological properties were investigated and it was found that the relative magnetorheological effects increased with increasing the particle size. Finally, the molecular dynamic simulation was used to analyze the mechanical characteristics of the magnetic fluid and the chain-like model agreed well with the experimental result. The authentic chain-like structure observed by a microscope agreed with the simulation results. The three particles composed of the similar cluster nanostructure, thus they exhibited similar magnetic property. To this end, the unique assembling microstructures was the origination of the mechanical difference. And it was found that the higher MR (magnetorheological) effects of the large particle based magnetic fluid was originated from the stronger assembling microstructure under the applying magnetic field.

  5. Counting particles emitted by stratospheric aircraft and measuring size of particles emitted by stratospheric aircraft

    NASA Technical Reports Server (NTRS)

    Wilson, James Charles

    1994-01-01

    The ER-2 condensation nuclei counter (CNC) has been modified to reduce the diffusive losses of particles within the instrument. These changes have been successful in improving the counting efficiency of small particles at low pressures. Two techniques for measuring the size distributions of particles with diameters less than 0.17 micrometers have been evaluated. Both of these methods, the differential mobility analyzer (DMA) and the diffusion battery, have fundamental problems that limit their usefulness for stratospheric applications. We cannot recommend either for this application. Newly developed, alternative methods for measuring small particles include inertial separation with a low-loss critical orifice and thin-plate impactor device. This technique is now used to collect particles in the multisample aerosol collector housed in the ER-2 CNC-2, and shows some promise for particle size measurements when coupled with a CNC as a counting device. The modified focused-cavity aerosol spectrometer (FCAS) can determine the size distribution of particles with ambient diameters as small as about 0.07 micrometers. Data from this instrument indicates the presence of a nuclei mode when CNC-2 indicates high concentrations of particles, but cannot resolve important parameters of the distribution.

  6. Dependence of thermal stability of lithiated Si on particle size

    NASA Astrophysics Data System (ADS)

    Li, Chao; Shi, Tongfei; Li, Decheng; Yoshitake, Hideya; Wang, Hongyu

    2016-12-01

    Thermal properties of the component materials are key issues in lithium ion batteries (LIBs). Si-based anodes are one of the most promising materials, but its thermal evolution have received much less attention than its electrochemical performance. In this article, the thermal behavior of various of Si material has been studied by differential scanning calorimetry (DSC). Three kinds of Si-particles, ranging from nano-to micro-sizes was subject to thermal analysis. It has been found that the thermal stability increases with the rise in particle-size. For the nanoparticles of 20 nm, both characteristic peaks of A and B regions in the heating process are stronger than the large-diameter particles. For three kinds of Si particles, the starting temperature of thermal reaction demonstrates a similar trend, gradually becoming lower with the increasing of the lithiation extent. At last, the ex situ XPS has also been conducted to explore the causes of surface state after temperature elevation. In A region, the heating decomposition of SEI with electrolyte, mainly consisting of a variety of esterification compounds, produces high content of lithium carbonate below 180 °C. When lithium in the inner phase of Si particles loses the protection of SEI film, the severe exothermic reaction occurred between lithium and the solvent species.

  7. Surface Chemistry at Size-Selected Nano-Aerosol Particles

    NASA Astrophysics Data System (ADS)

    Roberts, Jeffrey

    2005-03-01

    A method has been developed to conduct surface chemistry and extract surface kinetic rates from size-selected aerosol nanoparticles. The measurements encompass broad ranges of particle size, phase, and composition. Results will be presented on the uptake of water by aerosolized soot nanoparticles of radius between 10 and 40 nm. Water uptake was monitored by tandem differential mobility analysis (T-DMA), which is capable of measuring changes in particle diameter as little as 0.2 nm. Soot particles were produced in an ethene diffusion flame and extracted into an atmospheric pressure aerosol flow tube reactor. The particles were subjected to various thermal and oxidative treatments, and the effects of these treatments on the ability of soot to adsorb monolayer quantities of water was determined. The results are important because soot nucleates atmospheric cloud particles. More generally, the results represent one of the first kinetic and mechanistic studies of gas-phase nanoparticle reactivity. Co-author: Henry Ajo, University of Minnesota

  8. Aspects of droplet and particle size control in miniemulsions

    NASA Astrophysics Data System (ADS)

    Saygi-Arslan, Oznur

    Miniemulsion polymerization has become increasingly popular among researchers since it can provide significant advantages over conventional emulsion polymerization in certain cases, such as production of high-solids, low-viscosity latexes with better stability and polymerization of highly water-insoluble monomers. Miniemulsions are relatively stable oil (e.g., monomer) droplets, which can range in size from 50 to 500 nm, and are normally dispersed in an aqueous phase with the aid of a surfactant and a costabilizer. These droplets are the primary locus of the initiation of the polymerization reaction. Since particle formation takes place in the monomer droplets, theoretically, in miniemulsion systems the final particle size can be controlled by the initial droplet size. The miniemulsion preparation process typically generates broad droplet size distributions and there is no complete treatment in the literature regarding the control of the mean droplet size or size distribution. This research aims to control the miniemulsion droplet size and its distribution. In situ emulsification, where the surfactant is synthesized spontaneously at the oil/water interface, has been put forth as a simpler method for the preparation of miniemulsions-like systems. Using the in situ method of preparation, emulsion stability and droplet and particle sizes were monitored and compared with conventional emulsions and miniemulsions. Styrene emulsions prepared by the in situ method do not demonstrate the stability of a comparable miniemulsion. Upon polymerization, the final particle size generated from the in situ emulsion did not differ significantly from the comparable conventional emulsion polymerization; the reaction mechanism for in situ emulsions is more like conventional emulsion polymerization rather than miniemulsion polymerization. Similar results were found when the in situ method was applied to controlled free radical polymerizations (CFRP), which have been advanced as a

  9. TNT particle size distributions from detonated 155-mm howitzer rounds.

    PubMed

    Taylor, Susan; Hewitt, Alan; Lever, James; Hayes, Charlotte; Perovich, Laura; Thorne, Phil; Daghlian, Chuck

    2004-04-01

    To achieve sustainable range management and avoid or minimize environmental contamination, the Army needs to know the amount of explosives deposited on ranges from different munitions and how these are degraded and transported under different geological and climatic conditions. The physical form of the deposited explosives has a bearing on this problem, yet the shapes and size distributions of the explosive particles remaining after detonations are not known. We collected residues from 8 high-order and 6 low-order non-tactical detonations of TNT-filled 155-mm rounds. We found significant variation in the amount of TNT scattered from the high-order detonations, ranging from 0.00001 to 2% of the TNT in the original shell. All low-order detonations scattered percent-level amounts of TNT. We imaged thousands of TNT particles and determined the size, mass and surface-area distributions of particles collected from one high-order and one low-order detonation. For the high-order detonation, particles smaller than 1 mm contribute most of the mass and surface area of the TNT scattered. For the low-order detonation, most of the scattered TNT mass was in the form of un-heated, centimeter-sized pieces whereas most of the surface area was again from particles smaller than 1 mm. We also observed that the large pieces of TNT disintegrate readily, giving rise to many smaller particles that can quickly dissolve. We suggest picking up the large pieces of TNT before they disintegrate to become point sources of contamination.

  10. THE STICKINESS OF MICROMETER-SIZED WATER-ICE PARTICLES

    SciTech Connect

    Gundlach, B.; Blum, J.

    2015-01-01

    Water ice is one of the most abundant materials in dense molecular clouds and in the outer reaches of protoplanetary disks. In contrast to other materials (e.g., silicates), water ice is assumed to be stickier due to its higher specific surface energy, leading to faster or more efficient growth in mutual collisions. However, experiments investigating the stickiness of water ice have been scarce, particularly in the astrophysically relevant micrometer-sized region and at low temperatures. In this work, we present an experimental setup to grow aggregates composed of μm-sized water-ice particles, which we used to measure the sticking and erosion thresholds of the ice particles at different temperatures between 114 K and 260 K. We show with our experiments that for low temperatures (below ∼210 K), μm-sized water-ice particles stick below a threshold velocity of 9.6 m s{sup –1}, which is approximately 10 times higher than the sticking threshold of μm-sized silica particles. Furthermore, erosion of the grown ice aggregates is observed for velocities above 15.3 m s{sup –1}. A comparison of the experimentally derived sticking threshold with model predictions is performed to determine important material properties of water ice, i.e., the specific surface energy and the viscous relaxation time. Our experimental results indicate that the presence of water ice in the outer reaches of protoplanetary disks can enhance the growth of planetesimals by direct sticking of particles.

  11. The small volume particle microsampler (SVPM): a new approach to particle size distribution and composition

    NASA Astrophysics Data System (ADS)

    Archambault, Marie-Claude; Grant, Jon; Hatcher, Annamarie

    2001-10-01

    The characterization of trophically and geochemically important suspended particulate matter (SPM) has traditionally relied on bottle sampling and subsequent analysis with Coulter Multisizers and other instruments, which are not sufficient in preserving the in situ size, shape and composition of aggregated particles. The small volume particle microsampler (SVPM) is a sampling device that captures individual particles on filters with minimal disturbance for microscope image analysis of size distribution and composition. Sand grains, microalga ( Dunaliella tertiolecta) and laboratory cultivated flocs were used to test the SVPM's ability to determine particle size. For statistical analysis of the SVPM's capabilities, sand grain and algal size distribution, calculated as equivalent spherical diameter (ESD), were compared to Multisizer data while video images provided a comparison for the flocs. Non-aggregated sand particles sampled by the SVPM showed a size distribution that was similar to that of the Multisizer. Aggregated D. tertiolecta flocs were broken up by the Multisizer, and SVPM data indicated a significantly greater mean ESD. The SVPM showed significantly smaller mean ESDs than the video images because of the higher resolution of the sampler for small particles. In terms of particle concentration, the microsampler measured values similar to those of the Multisizer and video camera. The most important feature of the SVPM is its ability to capture aggregates for the analysis of composition, by histological stains or other means. The SVPM is an alternative method of sampling that is more effective in preserving aggregates for laboratory analyses and is less complicated and expensive than in situ optical sampling techniques, especially in documenting the lower end of the particle size spectrum.

  12. The particle size effect on Gas Hydrate Formation in powdered silica particles

    NASA Astrophysics Data System (ADS)

    Kawasaki, T.; Lu, H.; Ripmeester, J. A.; Zeng, H.; Fujii, T.; Nakamizu, M.

    2007-12-01

    Based on the investigations in the past years, it has been recognized that methane hydrates in Nankai Trough primarily occur in turbidite sediments (Fujii et al. 2005; Uchida et al., 2005). Turbidite is composed of a set of sediments, generally becoming finer upward in particle size, from coarse sand to clay (Bouma, 1962). In natural environment the formation of methane hydrate will be inevitably subject to the influence of sediments, so the modes of gas hydrate formation and occurrence might be different in the sediments with various particle sizes and mineral compositions. The elucidation of this issue, how sediments affect methane hydrate formation and occurrence will help in efficient hydrate exploration, accurate estimation of hydrate reserve, and the design of hydrate production method. In this research, we especially studied the particle size effect on the water conversion degree to hydrate using a set of powdered silica particles with the size from medium silt (<20 μm) to medium sand (250 ~ 500 μm). The test specimens were saturated with 3.5% NaCl solution, simulating the interstitial water of marine sediments, and reacted with methane gas at the pressure of ~ 10 MPa and temperature of 3° C. The water conversion degree to hydrate in a test specimen was estimated with the amount of gas that was clathrated in hydrate. The obtained results indicate a clear relationship between water conversion degree to hydrate and particle size: only 3.2 % when particle size is <20 μm, increasing dramatically from 5.7% to 82.8 % when particle size changes from ~30 μm (coarse silt) to ~200 μm (fine sand), and almost stable at ~ 80% when particle size is > 250 μm (medium sand). Because the test materials are all silica, the difference in water conversion degree to hydrate should be resulted from physical properties of silica particle, specific surface area, and/or the property confined by silica particle, pore size. This study was carried out as a part of Research

  13. Integral inversion to Fraunhofer diffraction for particle sizing.

    PubMed

    Cao, Zhang; Xu, Lijun; Ding, Jie

    2009-09-01

    A new solution to the inversion of Fraunhofer diffraction for particle sizing was introduced. Compared with the well-known Chin-Shifrin inversion, it is an inversion of the form of integral transform and less sensitive to noise. Simulation results with noise-contaminated data were obtained and showed that the new inversion is better than the Chin-Shifrin inversion. Especially when the particle diameter was small, the new inversion still performed well, whereas the Chin-Shifrin inversion did not converge.

  14. Infrared reflectance spectra: Effects of particle size, provenance and preparation

    SciTech Connect

    Su, Yin-Fong; Myers, Tanya L.; Brauer, Carolyn S.; Blake, Thomas A.; Forland, Brenda M.; Szecsody, James E.; Johnson, Timothy J.

    2014-09-22

    We have recently developed methods for making more accurate infrared total and diffuse directional - hemispherical reflectance measurements using an integrating sphere. We have found that reflectance spectra of solids, especially powders, are influenced by a number of factors including the sample preparation method, the particle size and morphology, as well as the sample origin. On a quantitative basis we have investigated some of these parameters and the effects they have on reflectance spectra, particularly in the longwave infrared. In the IR the spectral features may be observed as either maxima or minima: In general, upward-going peaks in the reflectance spectrum result from strong surface scattering, i.e. rays that are reflected from the surface without bulk penetration, whereas downward-going peaks are due to either absorption or volume scattering, i.e. rays that have penetrated or refracted into the sample interior and are not reflected. The light signals reflected from solids usually encompass all such effects, but with strong dependencies on particle size and preparation. This paper measures the reflectance spectra in the 1.3 – 16 micron range for various bulk materials that have a combination of strong and weak absorption bands in order to observe the effects on the spectral features: Bulk materials were ground with a mortar and pestle and sieved to separate the samples into various size fractions between 5 and 500 microns. The median particle size is demonstrated to have large effects on the reflectance spectra. For certain minerals we also observe significant spectral change depending on the geologic origin of the sample. All three such effects (particle size, preparation and provenance) result in substantial change in the reflectance spectra for solid materials; successful identification algorithms will require sufficient flexibility to account for these parameters.

  15. Coupling particle simulation with aerodynamic measurement in hypersonic rarefied wind tunnel in JAXA

    NASA Astrophysics Data System (ADS)

    Suzuki, Toshiyuki; Ozawa, Takashi; Fujita, Kazuhisa

    2012-11-01

    Characteristics of test flow produced by the hypersonic rarefied wind tunnel in JAXA are investigated experimentally and numerically. To probe the test flow, a stainless sphere model with a diameter of 5mm is put into the test flow. Its displacement due to the aerodynamic force is measured under the several operating conditions of the wind tunnel. A spatial variation of total pressure of the test flow is also measured by using a pitot pressure tube. The flowfield in the test section of wind tunnel is also analyzed by using the direct simulation Monte Carlo technique. The flow properties are deduced from the comparison between the measurement and the calculation. It is found from the study that the freestream Mach number of 16 and Knudsen number of 0.2 are achieved for the mass flow rate of 0.08g/s and the total temperature of 750K. The core flow diameter is estimated to be approximately 30mm.

  16. Optically controlled grippers for manipulating micron-sized particles

    NASA Astrophysics Data System (ADS)

    Gibson, Graham; Barron, Louise; Beck, Fiona; Whyte, Graeme; Padgett, Miles

    2007-01-01

    We report the development of a joystick controlled gripper for the real-time manipulation of micron-sized objects, driven using holographic optical tweezers (HOTs). The gripper consists of an arrangement of four silica beads, located in optical traps, which can be positioned and scaled in order to trap an object indirectly. The joystick can be used to grasp, move (lateral or axial), and change the orientation of the target object. The ability to trap objects indirectly allows us to demonstrate the manipulation of a strongly scattering micron-sized metallic particle.

  17. Effect of particle size and dopant concentration on photophysical properties of Eu3+-doped rare earth oxysulphide phosphor coatings.

    PubMed

    Chakradhar, R P S; Basu, Bharathibai J; Lakshmi, R V

    2011-02-01

    Europium-doped rare-earth oxysulphides (red phosphors) are often used as reference luminophore in pyrene-based pressure sensor coatings for aerodynamic applications. Different red phosphor samples were characterized for their particle size, chemical composition, photoluminescent properties and temperature sensitivity. The red phosphor samples were characterized using energy-dispersive X-ray spectroscopy (EDX) for elemental analysis and scanning electron microscopy (SEM) for morphology and particle size measurement. The particle size was in the range of 1.5-5.7 μm with morphology of hexagonal or spherical shape. It was found that phosphor with higher europium content exhibited higher luminescent emission intensity. The phosphor coatings were prepared by spraying a dispersion of the material in silicone resin. Smooth coatings were obtained by using phosphor samples with smaller particle size. Upon 334 nm excitation, the coatings showed characteristic luminescence 5D0→7FJ (J=0, 1, 2, 3, 4) of the Eu3+ ions. The electronic transition located at 626 nm (5D0→7F2) of Eu3+ ions was stronger than the magnetic dipole transition located at 595 nm (5D0→7F1). Luminescence decay curves obeyed double exponential behaviour. The phosphor samples showed temperature sensitivity of -0.012 to -0.168%/°C in the temperature range of 25-50 °C.

  18. Inversion method based on stochastic optimization for particle sizing.

    PubMed

    Sánchez-Escobar, Juan Jaime; Barbosa-Santillán, Liliana Ibeth; Vargas-Ubera, Javier; Aguilar-Valdés, Félix

    2016-08-01

    A stochastic inverse method is presented based on a hybrid evolutionary optimization algorithm (HEOA) to retrieve a monomodal particle-size distribution (PSD) from the angular distribution of scattered light. By solving an optimization problem, the HEOA (with the Fraunhofer approximation) retrieves the PSD from an intensity pattern generated by Mie theory. The analyzed light-scattering pattern can be attributed to unimodal normal, gamma, or lognormal distribution of spherical particles covering the interval of modal size parameters 46≤α≤150. The HEOA ensures convergence to the near-optimal solution during the optimization of a real-valued objective function by combining the advantages of a multimember evolution strategy and locally weighted linear regression. The numerical results show that our HEOA can be satisfactorily applied to solve the inverse light-scattering problem.

  19. Particle size and pathogenicity in the respiratory tract

    PubMed Central

    Thomas, Richard James

    2013-01-01

    Particle size dictates where aerosolized pathogens deposit in the respiratory tract, thereafter the pathogens potential to cause disease is influenced by tissue tropism, clearance kinetics and the host immunological response. This interplay brings pathogens into contact with a range of tissues spanning the respiratory tract and associated anatomical structures. In animal models, differential deposition within the respiratory tract influences infection kinetics for numerous select agents. Greater numbers of pathogens are required to infect the upper (URT) compared with the lower respiratory tract (LRT), and in comparison the URT infections are protracted with reduced mortality. Pathogenesis in the URT is characterized by infection of the URT lymphoid tissues, cervical lymphadenopathy and septicemia, closely resembling reported human infections of the URT. The olfactory, gastrointestinal, and ophthalmic systems are also infected in a pathogen-dependent manner. The relevant literature is reviewed with respect to particle size and infection of the URT in animal models and humans. PMID:24225380

  20. Size distributions of fine and ultrafine particles in the city of Strasbourg: correlation between number of particles and concentrations of NO(x) and SO(2) gases and some soluble ions concentration determination.

    PubMed

    Roth, Estelle; Kehrli, Damaris; Bonnot, Karine; Trouvé, Gwénaëlle

    2008-01-01

    An Electrical Low Pressure Impactor (ELPI) was used during spring and autumn 2003 in the centre of Strasbourg for the measurement of atmospheric aerosols size distribution. The concentration of NO(x) and SO(2) in air was simultaneously measured with specific analysers. Samples were collected in the range 0.007-10 microm in equivalent aerodynamic diameter size. Number distributions are representative of a pollution originating from urban traffic with a particle size distribution exhibiting a nucleation mode below 29 nm and an accumulation mode around 80 nm in size. A mean particle density equal to 39000+/-35000 total particles per cm(3) with a size ranging from 7 to 10 microm was obtained after a sampling period of 2 weeks in spring. About 86.9% of the number of particles have an aerodynamic diameter below 0.1 microm and 13.1% between 0.1 and 1 microm. Correlation coefficients between the number of particles impacted on each ELPI plate and gas concentrations (SO(2) and NO(x)) showed that the numbers of particles with diameter between 0.10 and 0.62 microm are highly related to the NO(x) concentration. This result indicates that particles are traffic induced since NO(x) is mainly emitted by cars as shown by measurements on various sites. Particles are less clearly correlated to the SO(2) concentration. Particle analysis on different ELPI plates for a sampling period of 2 weeks in autumn showed high level of soluble NO(3)(-), SO(4)(2-) and NH(4)(+) ions. Indeed, up to 90% b.w. of these three species were found in the particle range 0.1-1 microm. The formation of particulate NH(4)NO(3) is favoured by high NO(x) concentration, which induces the formation of gaseous HNO(3).

  1. Multiple-Instrument Analyses of Single Micron-Size Particles

    NASA Astrophysics Data System (ADS)

    Admon, Uri; Donohue, David; Aigner, Helmut; Tamborini, Gabriele; Bildstein, Olivier; Betti, Maria

    2005-08-01

    Physical, chemical, and isotopic analyses of individual radioactive and other particles in the micron-size range, key tools in environmental research and in nuclear forensics, require the ability to precisely relocate particles of interest (POIs) in the secondary ion mass spectrometer (SIMS) or in another instrument, after having been located, identified, and characterized in the scanning electron microscope (SEM). This article describes the implementation, testing, and evaluation of the triangulation POIs re-location method, based on microscopic reference marks imprinted on or attached to the sample holder, serving as an inherent coordinate system. In SEM-to-SEM and SEM-to-SIMS experiments re-location precision better than 10 [mu]m and 20 [mu]m, respectively, is readily attainable for instruments using standard specimen stages. The method is fast, easy to apply, and facilitates repeated analyses of individual particles in different instruments and laboratories.

  2. Thermal levitation of 10 um size particles in low vacuum

    NASA Astrophysics Data System (ADS)

    Fung, Long Fung Frankie; Kowalski, Nicholas; Parker, Colin; Chin, Cheng

    2016-05-01

    We report on experimental methods for trapping 10 micron-sized ice, glass, ceramic and polyethylene particles with thermophoresis in medium vacuum, at pressures between 5 Torr and 25 Torr. Under appropriate conditions particles can launch and levitate robustly for up to an hour. We describe the experimental setup used to produce the temperature gradient necessary for the levitation, as well as our procedure for generating and introducing ice into the experimental setup. In addition to analyzing the conditions necessary for levitation, and the dependence of levitation on the experimental parameters, we report on the behavior of particles during levitation and ejection, including position and stability, under different pressures and temperatures. We also note a significant discrepancy between theory and data, suggesting the presence of other levitating forces.

  3. Laser diffraction particle sizing: Instrument probe volume relocation and elongation

    NASA Technical Reports Server (NTRS)

    Anderson, Robert C.; Buchele, Donald R.; Hovenac, Edward A.; Lock, James A.

    1990-01-01

    The effective probe volume of laser diffraction particle sizing instruments depends on many instrument parameters. In particular the probe volume axial boundaries and its location along laser beam are essentially defined by the onset of a vignetting effect where light scattered at large angles from small particles misses the transform lens. This vignetting effect results in a probe volume that must be inconveniently close to the lens in order to detect smaller diameter particles (less than 100 micrometers). With the addition of an appropriately designed Keplerian telescope, the probe volume may be relocated and elongated. The theory of operation of this supplemental optical system is described. Design considerations for these supplemental optical systems are described, including recommendations for lens specifications, assembly and use. An image transfer system is described which has been designed for use on a Malvern 2600HSD instrument. Experimental validation of this image transfer system is described.

  4. Determination of particle size using measurement of scatter

    NASA Technical Reports Server (NTRS)

    Scott, R. L., Jr.

    1978-01-01

    A literature search was conducted to determine the state of the art particle size measurement by the light scatter technique. This technique may involve diffraction pattern analysis, location of minima and maxima in angular dependence of scattered light, magnitude of intensity verses angle, forward lobe scattered intensity ratio using two small angles, forward scatter in a small cone, and total scatter. Some of the more modern recordings and detection systems are video, holographic, and systems using optical processing.

  5. Derivation and use of simple relationships between aerodynamic and optical particle measurements

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A simple relationship, referred to as a mass conversion factor (MCF), is presented to convert optically based particle measurements to mass concentration. It is calculated from filter-based samples and optical particle counter (OPC) data on a daily or sample period basis. The MCF allows for greater ...

  6. Particle impactor assembly for size selective high volume air sampler

    DOEpatents

    Langer, Gerhard

    1988-08-16

    Air containing entrained particulate matter is directed through a plurality of parallel, narrow, vertically oriented impactor slots of an inlet element toward an adjacently located, relatively large, dust impaction surface preferably covered with an adhesive material. The air flow turns over the impaction surface, leaving behind the relatively larger particles according to the human thoracic separation system and passes through two elongate exhaust apertures defining the outer bounds of the impaction collection surface to pass through divergent passages which slow down and distribute the air flow, with entrained smaller particles, over a fine filter element that separates the fine particles from the air. The elongate exhaust apertures defining the impaction collection surface are spaced apart by a distance greater than the lengths of elongate impactor slots in the inlet element and are oriented to be normal thereto. By appropriate selection of dimensions and the number of impactor slots air flow through the inlet element is provided a nonuniform velocity distribution with the lower velocities being obtained near the center of the impactor slots, in order to separate out particles larger than a certain predetermined size on the impaction collection surface. The impaction collection surface, even in a moderately sized apparatus, is thus relatively large and permits the prolonged sampling of air for periods extending to four weeks.

  7. Particle Size Control of Polyethylene Glycol Coated Fe Nanoparticles

    NASA Astrophysics Data System (ADS)

    Srinivasan, B.; Bonder, M. J.; Zhang, Y.; Gallo, D.; Hadjipanayis, G. C.

    2006-03-01

    Recent interest in Fe nanoparticles with high magnetization is driven by their potential use in biomedical applications such as targeted drug delivery, MRI contrast enhancement and hyperthermia treatment of cancer. This study looks at the use of a polyethylene glycol (PEG) solution to mediate the particle size and therefore control the coercivity of the resulting nanoparticles. Iron nanoparticles were synthesized using an aqueous sodium borohydride reduction of ferrous chloride by a simultaneous introduction of reagents in a Y- junction. The resulting product was collected in a vessel containing a 15 mg/ml carboxyl terminated polyethylene glycol (cPEG) in ethyl alcohol solution located under the Y junction. By varying the length of tubing below the Y junction, the particle size was varied from 5-25 nm. X-ray diffraction data indicates the presence of either amorphous Fe-B or crystalline alpha Fe, depending on the molar ratio of reagents. Magnetic measurements indicate the particles are ferromagnetic with values of coercivity ranging from 200-500 Oe and a saturation magnetization in range of 70-110 emu/g. The XRD shows that the particles are not affected by the polymer coating.

  8. Light scattering by lunar-like particle size distributions

    NASA Technical Reports Server (NTRS)

    Goguen, Jay D.

    1991-01-01

    A fundamental input to models of light scattering from planetary regoliths is the mean phase function of the regolith particles. Using the known size distribution for typical lunar soils, the mean phase function and mean linear polarization for a regolith volume element of spherical particles of any composition were calculated from Mie theory. The two contour plots given here summarize the changes in the mean phase function and linear polarization with changes in the real part of the complex index of refraction, n - ik, for k equals 0.01, the visible wavelength 0.55 micrometers, and the particle size distribution of the typical mature lunar soil 72141. A second figure is a similar index-phase surface, except with k equals 0.1. The index-phase surfaces from this survey are a first order description of scattering by lunar-like regoliths of spherical particles of arbitrary composition. They form the basis of functions that span a large range of parameter-space.

  9. Production of large-particle-size monodisperse latexes

    NASA Technical Reports Server (NTRS)

    Vanderhoff, J. W.; El-Aasser, M. L.; Micale, F. J.; Sudol, E. D.; Tseng, C. M.; Silwanowicz, A.

    1984-01-01

    The research program achieved two objectives: (1) it has refined and extended the experimental techniques for preparing monodisperse latexes in quantity on the ground up to a particle diameter of 10 microns; and (2) it has demonstrated that a microgravity environment can be used to grow monodisperse latexes to larger sizes, where the limitations in size have yet to be defined. The experimental development of the monodisperse latex reactor (MLR) and the seeded emulsion polymerizations carried out in the laboratory prototype of the flight hardware, as a function of the operational parameters is discussed. The emphasis is directed towards the measurement, interpretation, and modeling of the kinetics of seeded emulsion polymerization and successive seeded emulsion polymerization. The recipe development of seeded emulsion polymerization as a function of particle size is discussed. The equilibrium swelling of latex particles with monomers was investigated both theoretically and experimentally. Extensive studies are reported on both the type and concentration of initiators, surfactants, and inhibitors, which eventually led to the development of the flight recipes. The experimental results of the flight experiments are discussed, as well as the experimental development of inhibition of seeded emulsion polymerization in terms of time of inhibition and the effect of inhibitors on the kinetics of polymerization.

  10. Airborne birch pollen antigens in different particle sizes.

    PubMed

    Rantio-Lehtimäki, A; Viander, M; Koivikko, A

    1994-01-01

    Two particle samplers for ambient air, situated together: a static size-selective bio-aerosol sampler (SSBAS) and a Burkard pollen and spore trap were compared in sampling intact birch pollen grains through one flowering period of Betula (a total of 44 days). The SSBAS trapped pollen grains three times more efficiently than the Burkard trap, but the variations in pollen counts were significantly correlated. In contrast, birch pollen antigenic activity and the pollen count in the Burkard samples were not closely correlated. The antigenic concentration was occasionally high both before and after the pollination period. There was a high birch pollen antigenic activity in particle size classes where intact pollen grains were absent, even on days when the pollen count was very low. Correspondingly, on days with high birch pollen counts in the air, pollen antigenic activity was on several occasions low, indicating that pollen grains were empty of antigenic material. The small particle size classes are especially important to allergic patients because they are able to penetrate immediately into the alveoli and provoke asthmatic reactions. Therefore, aerobiological information systems based on pollen and spore counts should be supplemented with information concerning antigenic activities in the air.

  11. Capillary effect in salt-cemented media of particle sizes

    NASA Astrophysics Data System (ADS)

    Yoon, Hyung-Koo; Hung Truong, Q.; Byun, Yong-Hoon; Lee, Jong-Sub

    2015-01-01

    Natural cementation such as salt cementation may significantly affect the geotechnical properties of soils at low confining pressures. Capillary force plays a key role in the distribution patterns of salt cementation resulting from dehydration. The aim of this study is to investigate the effect of capillary force on salt cementation through cone penetration testing, electrical conductivity measurements, photographic imaging technique, and nondestructive elastic wave scanning. Granular media is modeled using glass beads which are saturated in salt water and cemented by oven drying. The cone tip resistance profiles, electrical conductivity profiles, and amplitudes of the scanned elastic waves are high at the top of the specimen with small-sized particles, in the middle of the specimen in medium-sized particles, and at the bottom of the specimen in the large-sized particles. Differences in the distribution of salt in the cemented specimens are confirmed from photographic images. The calculated capillary heights are associated with the areas of high salt concentration in the cemented specimens. The four investigation methods used in this study show that the behavior of salt-cemented granular media depends on capillary force in a shallow depth.

  12. Comprehensive understanding of nano-sized particle separation processes using nanoparticle tracking analysis.

    PubMed

    Lawler, Desmond F; Youn, Sungmin; Zhu, Tongren; Kim, Ijung; Lau, Boris L T

    2015-01-01

    The understanding of nano-sized particle separation processes has been limited by difficulties of nanoparticle characterization. In this study, nanoparticle tracking analysis (NTA) was deployed to evaluate the absolute particle size distributions in laboratory scale flocculation and filtration experiments with silver nanoparticles. The results from NTA were consistent with standard theories of particle destabilization and transport. Direct observations of changes in absolute particle size distributions from NTA enhance both qualitative and quantitative understanding of particle separation processes of nano-sized particles.

  13. FIELD COMPARISONS OF DUAL SMPS-APS SYSTEMS TO MEASURE INDOOR-OUTDOOR PARTICLE SIZE DISTRIBUTIONS

    EPA Science Inventory

    Simultaneous measurements of particle size distributions across multiple locations can provide critical information to accurately assess human exposure to particles. These data are very useful to describe indoor-outdoor particle relationships, outdoor particle penetration thro...

  14. Counting Particles Emitted by Stratospheric Aircraft and Measuring Size of Particles Emitted by Stratospheric Aircraft

    NASA Technical Reports Server (NTRS)

    Wilson, James Charles

    1994-01-01

    There were two principal objectives of the cooperative agreement between NASA and the University of Denver. The first goal was to modify the design of the ER-2 condensation nuclei counter (CNC) so that the effective lower detection limit would be improved at high altitudes. This improvement was sought because, in the instrument used prior to 1993, diffusion losses prevented the smallest detectable particles from reaching the detection volume of the instrument during operation at low pressure. Therefore, in spite of the sensor's ability to detect particles as small as 0.008 microns in diameter, many of these particles were lost in transport to the sensing region and were not counted. Most of the particles emitted by aircraft are smaller than 0.1 micron in diameter. At the start date of this work, May 1990, continuous sizing techniques available on the ER-2 were only capable of detecting particles larger than 0.17 micron. Thus, the second objective of this work was to evaluate candidate sizing techniques in an effort to gain additional information concerning the size of particles emitted by aircraft.

  15. Decrease of calorific value and particle size in coal stockpiles

    SciTech Connect

    Sensogut, C.; Ozdeniz, A.H.

    2008-07-01

    During storage of excess amount of coal, they lose both their economical value and cause environmental problems. In this work, two industrial-sized stockpiles were constituted at a coal stockyard of Western Lignite Corporation (WLC) in Tuncbilek, Turkey. The size of the stockpiles, formed as triangle prisms, was about 10 m x 5 m wide with a height of 3 m; each mass being approximately 120 tons of coal in total. Some of the parameters that were effective on the stockpiles were measured in a continuous manner during this experimental work. The calorific losses and the decreases that occurred in particle size due to atmospheric conditions were also examined and detailed as the result of this work.

  16. Two size-selective mechanisms specifically trap bacteria-sized food particles in Caenorhabditis elegans.

    PubMed

    Fang-Yen, Christopher; Avery, Leon; Samuel, Aravinthan D T

    2009-11-24

    Caenorhabditis elegans is a filter feeder: it draws bacteria suspended in liquid into its pharynx, traps the bacteria, and ejects the liquid. How pharyngeal pumping simultaneously transports and filters food particles has been poorly understood. Here, we use high-speed video microscopy to define the detailed workings of pharyngeal mechanics. The buccal cavity and metastomal flaps regulate the flow of dense bacterial suspensions and exclude excessively large particles from entering the pharynx. A complex sequence of contractions and relaxations transports food particles in two successive trap stages before passage into the terminal bulb and intestine. Filtering occurs at each trap as bacteria are concentrated in the central lumen while fluids are expelled radially through three apical channels. Experiments with microspheres show that the C. elegans pharynx, in combination with the buccal cavity, is tuned to specifically catch and transport particles of a size range corresponding to most soil bacteria.

  17. Geostatistical Interpolation of Particle-Size Curves in Heterogeneous Aquifers

    NASA Astrophysics Data System (ADS)

    Guadagnini, A.; Menafoglio, A.; Secchi, P.

    2013-12-01

    We address the problem of predicting the spatial field of particle-size curves (PSCs) from measurements associated with soil samples collected at a discrete set of locations within an aquifer system. Proper estimates of the full PSC are relevant to applications related to groundwater hydrology, soil science and geochemistry and aimed at modeling physical and chemical processes occurring in heterogeneous earth systems. Hence, we focus on providing kriging estimates of the entire PSC at unsampled locations. To this end, we treat particle-size curves as cumulative distribution functions, model their densities as functional compositional data and analyze them by embedding these into the Hilbert space of compositional functions endowed with the Aitchison geometry. On this basis, we develop a new geostatistical methodology for the analysis of spatially dependent functional compositional data. Our functional compositional kriging (FCK) approach allows providing predictions at unsampled location of the entire particle-size curve, together with a quantification of the associated uncertainty, by fully exploiting both the functional form of the data and their compositional nature. This is a key advantage of our approach with respect to traditional methodologies, which treat only a set of selected features (e.g., quantiles) of PSCs. Embedding the full PSC into a geostatistical analysis enables one to provide a complete characterization of the spatial distribution of lithotypes in a reservoir, eventually leading to improved predictions of soil hydraulic attributes through pedotransfer functions as well as of soil geochemical parameters which are relevant in sorption/desorption and cation exchange processes. We test our new method on PSCs sampled along a borehole located within an alluvial aquifer near the city of Tuebingen, Germany. The quality of FCK predictions is assessed through leave-one-out cross-validation. A comparison between hydraulic conductivity estimates obtained

  18. [Ultrafine particle number concentration and size distribution of vehicle exhaust ultrafine particles].

    PubMed

    Lu, Ye-qiang; Chen, Qiu-fang; Sun, Zai; Cai, Zhi-liang; Yang, Wen-jun

    2014-09-01

    Ultrafine particle (UFP) number concentrations obtained from three different vehicles were measured using fast mobility particle sizer (FMPS) and automobile exhaust gas analyzer. UFP number concentration and size distribution were studied at different idle driving speeds. The results showed that at a low idle speed of 800 rmin-1 , the emission particle number concentration was the lowest and showed a increasing trend with the increase of idle speed. The majority of exhaust particles were in Nuclear mode and Aitken mode. The peak sizes were dominated by 10 nm and 50 nm. Particle number concentration showed a significantly sharp increase during the vehicle acceleration process, and was then kept stable when the speed was stable. In the range of 0. 4 m axial distance from the end of the exhaust pipe, the particle number concentration decayed rapidly after dilution, but it was not obvious in the range of 0. 4-1 m. The number concentration was larger than the background concentration. Concentration of exhaust emissions such as CO, HC and NO showed a reducing trend with the increase of idle speed,which was in contrast to the emission trend of particle number concentration.

  19. Measurement of resuspended aerosol in the Chernobyl area. Part III. Size distribution and dry deposition velocity of radioactive particles during anthropogenic enhanced resuspension.

    PubMed

    Garger, E K; Paretzke, H G; Tschiersch, J

    1998-10-01

    During anthropogenic activities, such as agricultural soil management and traffic on unpaved roads, size distribution measurements were performed of atmospheric particulate radionuclides at a site in the Chernobyl 30-km exclusion zone. Analysis of cascade impactor measurements showed an increase of the total atmospheric radioactivity. In the cases of harrowing by a tractor and traffic on unpaved roads, a common shape of the size distribution was found with two maxima, the first in the 2-4 microm range, the second in the 12-20 microm range. The size distributions were compared to measurements during wind-driven resuspension. Particle number concentration measurements with an Aerodynamic Particle Sizer showed a dynamic dependence of the particle concentration in different size ranges on anthropogenic action. The increase of the mean concentration was for the large particles more than one order of magnitude higher than for fine particles during anthropogenic enhanced resuspension. From the measurement of the mass concentration, the radioactive loading could be estimated. An enrichment of radionuclides on resuspended particles (compared to soil particles) was found, with the highest enrichment for large particles. Micrometeorological considerations showed that large particles may frequently be subject to medium range transport. The dry deposition velocity was measured; the mean value of 0.026 m s(-1) +/- 0.016 m s(-1) is typical for 6-9 microm diameter particles.

  20. The influence of particle size on latex colloid deposition kinetics

    SciTech Connect

    Litton, G.M.; Olson, T.M.

    1995-12-01

    The influence of particle size on the deposition kinetics of latex colloids in packed-bed columns was investigated in the presence of sodium dodecyl sulfate. Deposition rates, expressed as attachment efficiencies, were determined with 245, 481, and 755 nm carboxyl and 248 and 753 nm sulfate latex microspheres in granular quartz beds as a function of ionic strength. Experiments were performed at pH 10 in the presence of 10{sup -3} M sodium dodecyl sulfate to mask possible hydrophobic regions on the interacting surfaces. The onset of unfavorable filtration conditions and the sensitivity of the experimental attachment efficiencies, {alpha}{sub exp}, to changes in the ionic strength were both particle size dependent. However, both effects were opposite to that predicted by DLVO theory based on the primary interaction energy barrier height. Correlations of {alpha}{sub exp} with the secondary minimum showed that as attachment efficiencies approached 1 the depth of the secondary well increased. These observations suggest that particles may be retained within the secondary minimum even when a primary energy barrier is sufficient to inhibit attachment.

  1. Chemically generated convective transport of micron sized particles

    NASA Astrophysics Data System (ADS)

    Shklyaev, Oleg; Das, Sambeeta; Altemose, Alicia; Shum, Henry; Balazs, Anna; Sen, Ayusman

    2015-11-01

    A variety of chemical and biological applications require manipulation of micron sized objects like cells, viruses, and large molecules. Increasing the size of particles up to a micron reduces performance of techniques based on diffusive transport. Directional transport of cargo toward detecting elements reduces the delivery time and improves performance of sensing devices. We demonstrate how chemical reactions can be used to organize fluid flows carrying particles toward the assigned destinations. Convection is driven by density variations caused by a chemical reaction occurring at a catalyst or enzyme-covered target site. If the reaction causes a reduction in fluid density, as in the case of catalytic decomposition of hydrogen peroxide, then fluid and suspended cargo is drawn toward the target along the bottom surface. The intensity of the fluid flow and the time of cargo delivery are controlled by the amount of reagent in the system. After the reagent has been consumed, the fluid pump stops and particles are found aggregated on and around the enzyme-coated patch. The pumps are reusable, being reactivated upon injection of additional reagent. The developed technique can be implemented in lab-on-a-chip devices for transportation of micro-scale object immersed in solution.

  2. Depositing nanometer-sized particles of metals onto carbon allotropes

    NASA Technical Reports Server (NTRS)

    Watson, Kent A. (Inventor); Fallbach, Michael J. (Inventor); Ghose, Sayata (Inventor); Smith, Joseph G. (Inventor); Delozier, Donavon M. (Inventor); Connell, John W. (Inventor)

    2010-01-01

    A process for depositing nanometer-sized metal particles onto a substrate in the absence of aqueous solvents, organic solvents, and reducing agents, and without any required pre-treatment of the substrate, includes preparing an admixture of a metal compound and a substrate by dry mixing a chosen amount of the metal compound with a chosen amount of the substrate; and supplying energy to the admixture in an amount sufficient to deposit zero valance metal particles onto the substrate. This process gives rise to a number of deposited metallic particle sizes which may be controlled. The compositions prepared by this process are used to produce polymer composites by combining them with readily available commodity and engineering plastics. The polymer composites are used as coatings, or they are used to fabricate articles, such as free-standing films, fibers, fabrics, foams, molded and laminated articles, tubes, adhesives, and fiber reinforced articles. These articles are well-suited for many applications requiring thermal conductivity, electrical conductivity, antibacterial activity, catalytic activity, and combinations thereof.

  3. Particle Size and Structural Arrangement of Suspended Cohesive Sediments

    NASA Astrophysics Data System (ADS)

    Tan, X.; Zhang, G.; Reed, A. H.; Furukawa, Y.

    2012-12-01

    Coastal environments are often characterized by high concentrations of cohesive sediments influenced by the loaded organic matter (particularly extracellular polymeric substances (EPS)), salt, and hydrodynamic disturbance. The size and structural variation of suspended cohesive sediments due to flocculation and/or disaggregation is of key importance for understanding a variety of sediment transport processes (e.g., settling, breakage, survivability) in littoral environments and the geotechnical/geophysical properties of the bottom bed. To obtain a comprehensive understanding of sediment floc behavior and correlate the clay-EPS-ion interaction mechanisms with their structures, a series of sediment samples were synthesized in laboratory using four pure clays (i.e., kaolinite, illite, Ca-montmorillonite, and Na-montmorillonite), three EPS (cationic, neutral, and anionic) at different concentrations, and saltwater of different salinity under different hydrodynamic conditions. Particle size analysis of the pure clays, clay-EPS, and clay-salt flocs under three hydrodynamic conditions demonstrated for the first time in the laboratory that pure clays and clay-EPS mixtures exhibit lognormal, multimodal (i.e., 2-4 levels consisting of primary particle, flocculi, microfloc, and macrofloc) particle size distributions (PSDs) within the size range of ~0.1 to ~500 μm. The presence of EPS causes the formation of macroflocs (>200 μm) and can significantly increase the mean particle size by several orders of magnitude through flocculation, assisted by electrostatic forces, ion-dipole, van der Waals forces, and other mechanisms. The change in size of the pure clay flocs in saltwater showed different trends: Due to the clays' different properties and interaction mechanisms with EPS, their PSDs and size changes are also different in different flow conditions: the hydrodynamic turbulence may promote the flocculation of Ca-montmorillonite, but break kaolinite and Na

  4. Effect of traffic restriction on atmospheric particle concentrations and their size distributions in urban Lanzhou, Northwestern China.

    PubMed

    Zhao, Suping; Yu, Ye; Liu, Na; He, Jianjun; Chen, Jinbei

    2014-02-01

    During the 2012 Lanzhou International Marathon, the local government made a significant effort to improve traffic conditions and air quality by implementing traffic restriction measures. To evaluate the direct effect of these measures on urban air quality, especially particle concentrations and their size distributions, atmospheric particle size distributions (0.5-20 microm) obtained using an aerodynamic particle sizer (model 3321, TSI, USA) in June 2012 were analyzed. It was found that the particle number, surface area and volume concentrations for size range 0.5-10 microm were (15.0 +/- 2.1) cm(-3), (11.8 +/- 2.6) microm2/cm3 and (1.9 +/- 0.6) microm2/cm3, respectively, on the traffic-restricted day (Sunday), which is 63.2%, 53.0% and 47.2% lower than those on a normal Sunday. For number and surface area concentrations, the most affected size range was 0.5-0.7 and 0.5-0.8 microm, respectively, while for volume concentration, the most affected size ranges were 0.5-0.8, 1.7-2.0 and 5.0-5.4 microm. Number and volume concentrations of particles in size range 0.5-1.0 microm correlated well with the number of non-CNG (Compressed Natural Gas) powered vehicles, while their correlation with the number of CNG-powered vehicles was very low, suggesting that reasonable urban traffic controls along with vehicle technology improvements could play an important role in improving urban air quality.

  5. Shape, size, and distribution of magnetic particles in Bjurbole chondrules

    NASA Technical Reports Server (NTRS)

    Nava, David F.

    1994-01-01

    Chondrules from the Bjurbole chondritic meteorite (L4) exhibit saturation remanence magnetization (SIRM) values which vary over three orders of magnitude. REM values (Natural Remanence Magnetization/SIRM) for Allende (C3V) and Chainpur (LL3) are less than 0.01 but in Bjurbole some chondrules were found to have REM values greater than 0.1 with several greater than 0.2. REM values greater than 0.1 are abnormal and cannot be acquired during weak field cooling. If exposure to a strong field (whatever the source) during the chondrules' history is responsible for the high REM values, was such history associated with a different processing which might have resulted in different shape, size, and distribution of metal particles compared to chondrules having REM values of less than 0.01? Furthermore, magnetic hysteresis results show a broad range of magnetic hardness and other intrinsic magnetic properties. These features must be related to (1) size and amount of metal; and (2) properties of, and amount of, tetrataenite in the chondrules (all chondrules thus far subjected to thermomagnetic analysis show the presence of tetrataenite). A scanning electron microscopy (SEM) study is underway to determine the relationship between the shape, size, and distribution of metal particles within individual chondrules and the magnetic properties of these chondrules. Results from the SEM study in conjunction with magnetic property data may also help to discern effects from possible lightning strikes in the nebula prior to incorporation of the chondrules into the parent body.

  6. Finite-size effects in dissipative particle dynamics simulations.

    PubMed

    Velázquez, María Eugenia; Gama-Goicochea, Armando; González-Melchor, Minerva; Neria, Maricela; Alejandre, José

    2006-02-28

    We have performed dissipative particle dynamics (DPD) simulations to evaluate the effect that finite size of transversal area has on stress anisotropy and interfacial tension. The simulations were carried out in one phase and two phases in parallelepiped cells. In one-phase simulations there is no finite-size effect on stress anisotropy when the simulation is performed using repulsive forces. However, an oscillatory function of stress anisotropy is found for attractive-repulsive interactions. In the case of liquid-liquid interfaces with repulsive interaction between molecules, there is only a small effect of surface area on interfacial tension when the simulations are performed using the Monte Carlo method at constant temperature and normal pressure. An important but artificial finite-size effect of interfacial area on surface tension is found in simulations in the canonical ensemble. Reliable results of interfacial tension from DPD simulations can be obtained using small systems, less than 2000 particles, when they interact exclusively with repulsive forces.

  7. An optical trapped nanohand for manipulating micron-sized particles

    NASA Astrophysics Data System (ADS)

    Gibson, Graham; Barron, Louise; Beck, Fiona; Whyte, Graeme; Padgett, Miles

    2006-08-01

    Optical tweezers use the electric-field gradient-force associated with tightly focused laser beams to trap micron-sized objects at the beam focus. Over the last few years optical tweezers have been revolutionized by the addition of spatial light modulators to split the laser beam into many traps that can be individually controlled; a technique called holographic optical tweezers. However, the reliance of optical tweezers on the gradient-force largely restricts their application to transparent objects that are not unduly sensitive to the effects of the laser light. Consequently, the manipulation of metallic particles or sensitive biomaterials can be problematic. In this work we use a holographic tweezers to position multiple silica beads acting as an optical gripper to lift, rotate and move micron-sized objects that otherwise do not lend themselves to tweezers control. We illustrate the use of the optical gripper under real-time joystick control to manipulate micron-sized metallic particles with nano-scale precision.

  8. Nano to micro particle size distribution measurement in the fluid by interactive force apparatus for fine particle processing.

    PubMed

    Fujita, Toyohisa; Dodbiba, Gjergj; Okaya, Katsunori; Matsuo, Seiji; Wang, Li Pang; Onda, Kana; Otsuki, Akira

    2013-12-01

    The direct measurement of fine particles size distribution of dispersions or coagulations in liquid is important for water purification, fine particles separation for recycling and mineral processing, as well as the new material production. The nano to micro particle size is usually measured by light scattering method; however, it is difficult to measure at high concentration of suspension. Here, a novel dynamical method by using the interactive force measurement between particles in liquid under electric field is used for measuring distribution of fine particle. Three types of nano to submicron particles, that is well-dispersed nano particles, coagulated nano particles and settled submicron particles, have been measured by interactive force measurement method. The particle size distributions are compered with the size distributions of dried particles measured by TEM or SEM. The well-dispersed nano particle size distribution by interactive force measurement is influenced by the nano size surfactant micelles. The size distribution of coagulated nano particles in water is larger than the result by TEM. On the other hand, the submicron nickel particle size distribution is similar with the one analyzed by SEM.

  9. Effects of particle size and velocity on burial depth of airborne particles in glass fiber filters

    SciTech Connect

    Higby, D.P.

    1984-11-01

    Air sampling for particulate radioactive material involves collecting airborne particles on a filter and then determining the amount of radioactivity collected per unit volume of air drawn through the filter. The amount of radioactivity collected is frequently determined by directly measuring the radiation emitted from the particles collected on the filter. Counting losses caused by the particle becoming buried in the filter matrix may cause concentrations of airborne particulate radioactive materials to be underestimated by as much as 50%. Furthermore, the dose calculation for inhaled radionuclides will also be affected. The present study was designed to evaluate the extent to which particle size and sampling velocity influence burial depth in glass-fiber filters. Aerosols of high-fired /sup 239/PuO/sub 2/ were collected at various sampling velocities on glass-fiber filters. The fraction of alpha counts lost due to burial was determined as the ratio of activity detected by direct alpha count to the quantity determined by photon spectrometry. The results show that burial of airborne particles collected on glass-fiber filters appears to be a weak function of sampling velocity and particle size. Counting losses ranged from 0 to 25%. A correction that assumes losses of 10 to 15% would ensure that the concentration of airborne alpha-emitting radionuclides would not be underestimated when glass-fiber filters are used. 32 references, 21 figures, 11 tables.

  10. Particle Size Distributions Obtained Through Unfolding 2D Sections: Towards Accurate Distributions of Nebular Solids in the Allende Meteorite

    NASA Technical Reports Server (NTRS)

    Christoffersen, P. A.; Simon, Justin I.; Ross, D. K.; Friedrich, J. M.; Cuzzi, J. N.

    2012-01-01

    Size distributions of nebular solids in chondrites suggest an efficient sorting of these early forming objects within the protoplanetary disk. The effect of this sorting has been documented by investigations of modal abundances of CAIs (e.g., [1-4]) and chondrules (e.g., [5-8]). Evidence for aerodynamic sorting in the disk is largely qualitative, and needs to be carefully assessed. It may be a way of concentrating these materials into planetesimal-mass clumps, perhaps 100 fs of ka after they formed. A key parameter is size/density distributions of particles (i.e., chondrules, CAIs, and metal grains), and in particular, whether the radius-density product (rxp) is a better metric for defining the distribution than r alone [9]. There is no consensus between r versus rxp based models. Here we report our initial tests and preliminary results, which when expanded will be used to test the accuracy of current dynamical disk models.

  11. Size-resolved measurements of ice-nucleating particles at six locations in North America and one in Europe

    NASA Astrophysics Data System (ADS)

    Mason, R. H.; Si, M.; Chou, C.; Irish, V. E.; Dickie, R.; Elizondo, P.; Wong, R.; Brintnell, M.; Elsasser, M.; Lassar, W. M.; Pierce, K. M.; Leaitch, W. R.; MacDonald, A. M.; Platt, A.; Toom-Sauntry, D.; Sarda-Estève, R.; Schiller, C. L.; Suski, K. J.; Hill, T. C. J.; Abbatt, J. P. D.; Huffman, J. A.; DeMott, P. J.; Bertram, A. K.

    2016-02-01

    Detailed information on the size of ice-nucleating particles (INPs) may be useful in source identification, modeling their transport in the atmosphere to improve climate predictions, and determining how effectively or ineffectively instrumentation used for quantifying INPs in the atmosphere captures the full INP population. In this study we report immersion-mode INP number concentrations as a function of size at six ground sites in North America and one in Europe using the micro-orifice uniform-deposit impactor droplet freezing technique (MOUDI-DFT), which combines particle size-segregation by inertial impaction and a microscope-based immersion freezing apparatus. The lowest INP number concentrations were observed at Arctic and alpine locations and the highest at suburban and agricultural locations, consistent with previous studies of INP concentrations in similar environments. We found that 91 ± 9, 79 ± 17, and 63 ± 21 % of INPs had an aerodynamic diameter > 1 µm at ice activation temperatures of -15, -20, and -25 °C, respectively, when averaging over all sampling locations. In addition, 62 ± 20, 55 ± 18, and 42 ± 17 % of INPs were in the coarse mode (> 2.5 µm) at ice activation temperatures of -15, -20, and -25 °C, respectively, when averaging over all sampling locations. These results are consistent with six out of the nine studies in the literature that have focused on the size distribution of INPs in the atmosphere. Taken together, these findings strongly suggest that supermicron and coarse-mode aerosol particles are a significant component of the INP population in many different ground-level environments. Further size-resolved studies of INPs as a function of altitude are required since the size distribution of INPs may be different at high altitudes due to size-dependent removal processes of atmospheric particles.

  12. Polymer-Particle Nanocomposites: Size and Dispersion Effects

    NASA Astrophysics Data System (ADS)

    Moll, Joseph

    Polymer-particle nanocomposites are used in industrial processes to enhance a broad range of material properties (e.g. mechanical, optical, electrical and gas permeability properties). This dissertation will focus on explanation and quantification of mechanical property improvements upon the addition of nanoparticles to polymeric materials. Nanoparticles, as enhancers of mechanical properties, are ubiquitous in synthetic and natural materials (e.g. automobile tires, packaging, bone), however, to date, there is no thorough understanding of the mechanism of their action. In this dissertation, silica (SiO2) nanoparticles, both bare and grafted with polystyrene (PS), are studied in polymeric matrices. Several variables of interest are considered, including particle dispersion state, particle size, length and density of grafted polymer chains, and volume fraction of SiO2. Polymer grafted nanoparticles behave akin to block copolymers, and this is critically leveraged to systematically vary nanoparticle dispersion and examine its role on the mechanical reinforcement in polymer based nanocomposites in the melt state. Rheology unequivocally shows that reinforcement is maximized by the formation of a transient, but long-lived, percolating polymer-particle network with the particles serving as the network junctions. The effects of dispersion and weight fraction of filler on nanocomposite mechanical properties are also studied in a bare particle system. Due to the interest in directional properties for many different materials, different means of inducing directional ordering of particle structures are also studied. Using a combination of electron microscopy and x-ray scattering, it is shown that shearing anisotropic NP assemblies (sheets or strings) causes them to orient, one in front of the other, into macroscopic two-dimensional structures along the flow direction. In contrast, no such flow-induced ordering occurs for well dispersed NPs or spherical NP aggregates! This work

  13. Particle Sizing in a Fuel-Rich Ramjet Combustor.

    DTIC Science & Technology

    1983-08-01

    COVERED Particle Sizing in a Fuel-Rich Ramjet Combustor Technical Memorandum 6 PERFORMING ORG. REPORT NUMBER 7. AIJTHORII CONTRACT OR GRANT NUMBER~s...R. Turner and R. A. Murphy N00024-83-C-S3Ol 9. PERFORMING ORGANIZATION NAME & ADDRESS 10. PROGRAM ELEMENT. PROJECT. TASK The Johns Hopkins University... Analyi , of t)op- pier Signal Characteristics for a Cross-tean I aser Doppler Ve- locimcier." 4ppI. Opt.. 14. 2177 (1975). In the present configuration

  14. Photonic nanojet effect in multilayer micrometre-sized spherical particles

    NASA Astrophysics Data System (ADS)

    Geints, Yu E.; Zemlyanov, A. A.; Panina, E. K.

    2011-06-01

    The spatial and amplitude characteristics of photonic nanojets from micrometre-sized composite particles consisting of a nucleus and several shells with different refractive indices were considered. We investigated the longitudinal and transverse dimensions of the photon jet as well as the dependence of its peak intensity on the optical contrast of the shells. It was shown that, by varying the refractive index of the neighbouring shells in composite spherical microparticles, it is possible to manipulate the photonic nanojet parameters, in particular, increase its length or raise the peak intensity of the photon flux.

  15. Photonic nanojet effect in multilayer micrometre-sized spherical particles

    SciTech Connect

    Geints, Yu E; Zemlyanov, A A; Panina, E K

    2011-06-30

    The spatial and amplitude characteristics of photonic nanojets from micrometre-sized composite particles consisting of a nucleus and several shells with different refractive indices were considered. We investigated the longitudinal and transverse dimensions of the photon jet as well as the dependence of its peak intensity on the optical contrast of the shells. It was shown that, by varying the refractive index of the neighbouring shells in composite spherical microparticles, it is possible to manipulate the photonic nanojet parameters, in particular, increase its length or raise the peak intensity of the photon flux. (interaction of laser radiation with matter. laser plasma)

  16. Characterization of particle number size distribution and new particle formation in Southern China.

    PubMed

    Huang, Xiaofeng; Wang, Chuan; Peng, Jianfei; He, Lingyan; Cao, Liming; Zhu, Qiao; Cui, Jie; Wu, Zhijun; Hu, Min

    2017-01-01

    Knowledge of particle number size distribution (PND) and new particle formation (NPF) events in Southern China is essential for mitigation strategies related to submicron particles and their effects on regional air quality, haze, and human health. In this study, seven field measurement campaigns were conducted from December 2013 to May 2015 using a scanning mobility particle sizer (SMPS) at four sites in Southern China, including three urban sites and one background site. Particles were measured in the size range of 15-615nm, and the median particle number concentrations (PNCs) were found to vary in the range of 0.3×10(4)-2.2×10(4)cm(-3) at the urban sites and were approximately 0.2×10(4)cm(-3) at the background site. The peak diameters at the different sites varied largely from 22 to 102nm. The PNCs in the Aitken mode (25-100nm) at the urban sites were up to 10 times higher than they were at the background site, indicating large primary emissions from traffic at the urban sites. The diurnal variations of PNCs were significantly influenced by both rush hour traffic at the urban sites and NPF events. The frequencies of NPF events at the different sites were 0%-30%, with the highest frequency occurring at an urban site during autumn. With higher SO2 concentrations and higher ambient temperatures being necessary, NPF at the urban site was found to be more influenced by atmospheric oxidizing capability, while NPF at the background site was limited by the condensation sink. This study provides a unique dataset of particle number and size information in various environments in Southern China, which can help understand the sources, formation, and the climate forcing of aerosols in this quickly developing region, as well as help constrain and validate NPF modeling.

  17. Experimental investigation of suspended particles transport through porous media: particle and grain size effect.

    PubMed

    Liu, Quansheng; Cui, Xianze; Zhang, Chengyuan; Huang, Shibing

    2016-01-01

    Particle and grain size may influence the transportation and deposition characteristics of particles within pollutant transport and within granular filters that are typically used in wastewater treatment. We conducted two-dimensional sandbox experiments using quartz powder as the particles and quartz sand as the porous medium to study the response of transportation and deposition formation to changes in particle diameter (ds, with median diameter 18, 41, and 82 μm) and grain diameter (dp, with median diameter 0.36, 1.25, and 2.82 mm) considering a wide range of diameter ratios (ds/dp) from 0.0064 to 0.228. Particles were suspended in deionized water, and quartz sand was used as the porous medium, which was meticulously cleaned to minimize any physicochemical and impurities effects that could result in indeterminate results. After the experiments, the particle concentration of the effluent and particle mass per gram of dry sands were measured to explore changes in transportation and deposition characteristics under different conditions. In addition, a micro-analysis was conducted to better analyse the results on a mesoscopic scale. The experimental observation analyses indicate that different diameter ratios (ds/dp) may lead to different deposit formations. As ds/dp increased, the deposit formation changed from 'Random Deposition Type' to 'Gradient Deposition Type', and eventually became 'Inlet Deposition Type'.

  18. A note on the stochastic nature of particle cohesive force and implications to threshold friction velocity for aerodynamic dust entrainment

    Technology Transfer Automated Retrieval System (TEKTRAN)

    There is considerable interest to determine the threshold for aeolian dust emission on Earth and Mars. Existing schemes for threshold friction velocity are all deterministic in nature, but observations show that in the dust particle size range the threshold friction velocity scatters strongly due t...

  19. Effect of Primary Particle Size on the Granule Properties

    NASA Astrophysics Data System (ADS)

    Rahmanian, Nejat; Ghadiri, Mojtaba; Ding, Yulong; Jia, Xiaodong

    2009-06-01

    Results of a study of the influence of primary particle size on the strength, density and internal structure of granules produced in a high shear mixer granulator, Cyclomix (manufactured by Hosokawa Micron B.V., The Netherlands) are reported. Different grades of calcium carbonate powder (available commercially as Durcal 15, 40 and 65) were granulated in a 50 L granulator. Durcal 15 is the finest powder, d50 = 23 μm, and Durcal 65 is the coarsest one, d50 = 60 μm. An aqueous solution of polyethylene glycol was used as the binder. Granules produced from the three powder grades were dried and tested to ascertain their internal structure using X-ray Micro Tomography (XMT). The granules were also individually subjected to quasi-static compression to characterise their crushing strength. The envelop density of granules for each powder grade was also measured. The results show that the envelope density increases with the mean size of primary particles. It is found that a more uniform strength and density distributions are obtained for the coarsest powder grade and the granulation operating conditions for the finest grade, Durcal 15, produced the weakest granules. This is attributed to the presence of large pores and cavities in their cores, as observed by XMT.

  20. Single particle size and fluorescence spectra from emissions of burning materials in a tube furnace to simulate burn pits

    NASA Astrophysics Data System (ADS)

    Pan, Yong-Le; Houck, Joshua D. T.; Clark, Pamela A.; Pinnick, Ronald G.

    2013-08-01

    A single-particle fluorescence spectrometer (SPFS) and an aerodynamic particle sizer were used to measure the fluorescence spectra and particle size distribution from the particulate emissions of 12 different burning materials in a tube furnace to simulate open-air burning of garbage. Although the particulate emissions are likely dominated by particles <1 μm diameter, only the spectra of supermicron particles were measured here. The overall fluorescence spectral profiles exhibit either one or two broad bands peaked around 300-450 nm within the 280-650 nm spectral range, when the particles are illuminated with a 263-nm laser. Different burning materials have different profiles, some of them (cigarette, hair, uniform, paper, and plastics) show small changes during the burning process, and while others (beef, bread, carrot, Styrofoam, and wood) show big variations, which initially exhibit a single UV peak (around 310-340 nm) and a long shoulder in visible, and then gradually evolve into a bimodal spectrum with another visible peak (around 430-450 nm) having increasing intensity during the burning process. These spectral profiles could mainly derive from polycyclic aromatic hydrocarbons with the combinations of tyrosine-like, tryptophan-like, and other humic-like substances. About 68 % of these single-particle fluorescence spectra can be grouped into 10 clustered spectral templates that are derived from the spectra of millions of atmospheric aerosol particles observed in three locations; while the others, particularly these bimodal spectra, do not fall into any of the 10 templates. Therefore, the spectra from particulate emissions of burning materials can be easily discriminated from that of common atmospheric aerosol particles. The SFFS technology could be a good tool for monitoring burning pit emissions and possibly for distinguishing them from atmospheric aerosol particles.

  1. Comparison of trace elements in size-fractionated particles in two communities with contrasting socioeconomic status in Houston, TX.

    PubMed

    Han, Inkyu; Guo, Yuncan; Afshar, Masoud; Stock, Thomas H; Symanski, Elaine

    2017-02-01

    Levels of ambient air pollutants, including particulate matter (PM), are often higher in low-socioeconomic status (SES) communities than in high-SES communities. Houston is the fourth largest city in the USA and is home to a large petrochemical industry, an active port, and congested roadways, which represent significant emission sources of air pollution in the region. To compare levels of air pollution between a low-SES and a high-SES community, we simultaneously collected a 7-day integrated size-fractionated PM between June 2013 and November 2013. We analyzed PM mass and elements for three particle size modes: quasi-ultrafine particles (quasi-UFP) (aerodynamic diameter <0.25 μm), accumulation mode particles (0.25-2.5 μm), and coarse mode particles (>2.5 μm). Concentrations of vanadium, nickel, manganese, and iron in the quasi-UFP mode were significantly higher in the low-SES community than in the high-SES community. In the accumulation and coarse modes, concentrations of crustal elements and barium were also significantly higher in the low-SES community compared to the high-SES community. These findings suggest that people living in the low-SES community may experience higher exposures to some toxic elements as compared to people in the high-SES community.

  2. Size Resolved High Temperature Oxidation Kinetics of Nano-Sized Titanium and Zirconium Particles.

    PubMed

    Zong, Yichen; Jacob, Rohit J; Li, Shuiqing; Zachariah, Michael R

    2015-06-18

    While ultrafine metal particles offer the possibility of very high energy density fuels, there is considerable uncertainty in the mechanism by which metal nanoparticles burn, and few studies that have examined the size dependence to their kinetics at the nanoscale. In this work we quantify the size dependence to the burning rate of titanium and zirconium nanoparticles. Nanoparticles in the range of 20-150 nm were produced via pulsed laser ablation, and then in-flight size-selected using differential electrical mobility. The size-selected oxide free metal particles were directly injected into the post flame region of a laminar flame to create a high temperature (1700-2500 K) oxidizing environment. The reaction was monitored using high-speed videography by tracking the emission from individual nanoparticles. We find that sintering occurs prior to significant reaction, and that once sintering is accounted for, the rate of combustion follows a near nearly (diameter)(1) power-law dependence. Additionally, Arrhenius parameters for the combustion of these nanoparticles were evaluated by measuring the burn times at different ambient temperatures. The optical emission from combustion was also used to model the oxidation process, which we find can be reasonably described with a kinetically controlled shrinking core model.

  3. Concentrations, size distributions and temporal variations of fluorescent biological aerosol particles in southern tropical India

    NASA Astrophysics Data System (ADS)

    Valsan, Aswathy; Krishna R, Ravi; CV, Biju; Huffman, Alex; Poschl, Ulrich; Gunthe, Sachin

    2015-04-01

    Biological aerosols constitute a wide range of dead and alive biological materials and structures that are suspended in the atmosphere. They play an important role in the atmospheric physical, chemical and biological processes and health of living being by spread of diseases among humans, plants, and, animals. The atmospheric abundance, sources, physical properties of PBAPs as compared to non-biological aerosols, however, is poorly characterized. The Indian tropical region, where large fraction of the world's total population is residing, experiences a distinctive meteorological phenomenon by means of Indian Summer Monsoon (IMS). Thus, the properties and characteristics of biological aerosols are also expected to be very diverse over the Indian subcontinent depending upon the seasons. Here we characterize the number concentration and size distribution of Fluorescent Biological Aerosol Particles (FBAP) at a high altitude continental site, Munnar (10.09 N, 77.06 E; 1605 m asl) in South India during the South-West monsoon, which constitute around 80 percent of the annual rainfall in Munnar. Continuous three months measurements (from 01 June 2014 to 21 Aug 2104) FBAPs were carried out at Munnar using Ultra Violet Aerodynamic Particle Sizer (UVAPS) during IMS. The mean number and mass concentration of coarse FBAP averaged over the entire campaign was 1.7 x 10-2 cm-3 and 0.24 µg m-3 respectively, which corresponds to 2 percent and 6 percent of total aerosol particle number and mass concentration. In agreement to other previous measurements the number size distribution of FBAP also peaks at 3.2 micron indicating the strong presence of fungal spores. This was also supported by the Scanning Electron Microscopic analysis of bioaerosols on filter paper. They also displayed a strong diurnal cycle with maximum concentration occurring at early morning hours. During periods of heavy and continuous rain where the wind is consistently blowing from South-West direction it was

  4. The effect of particle size, location and season on the toxicity of urban and rural particulate matter.

    PubMed

    Mirowsky, Jaime; Hickey, Christina; Horton, Lori; Blaustein, Martin; Galdanes, Karen; Peltier, Richard E; Chillrud, Steven; Chen, Lung Chi; Ross, James; Nadas, Arthur; Lippmann, Morton; Gordon, Terry

    2013-11-01

    Particulate matter (PM) varies in chemical composition and mass concentration based on a number of factors including location, season, source and particle size. The aim of this study was to evaluate the in vitro and in vivo toxicity of coarse and fine PM simultaneously collected at three rural and two urban sites within the metropolitan New York City (NYC) region during two seasons, and to assess how particle size and elemental composition affect toxicity. Human pulmonary microvascular endothelial (HPMEC-ST1.6R) and bronchial epithelial (BEAS-2B) cell lines were exposed to PM (50 μg/mL) and analyzed for reactive oxygen species (ROS). Mice (FVB/N) were exposed by oropharyngeal aspiration to 50 µg PM, and lavage fluid was analyzed for total protein and PMN influx. The ROS response was greater in the HPMEC-ST1.6R cell line compared to BEAS-2B cells, but the responses were significantly correlated (p < 0.01). The ROS response was affected by location, locale and the location:size interaction in both cell lines, and an additional association for size was observed from HPMEC-ST1.6R cells. Urban fine PM generated the highest ROS response. In the mouse model, inflammation was associated with particle size and by a season:size interaction, with coarse PM producing greater PMN inflammation. This study showed that the aerodynamic size, locale (i.e. urban versus rural), and site of PM samples affected the ROS response in pulmonary endothelial and epithelial cells and the inflammatory response in mice. Importantly, these responses were dependent upon the chemical composition of the PM samples.

  5. The effect of particle size, location and season on the toxicity of urban and rural particulate matter

    PubMed Central

    Mirowsky, Jaime; Hickey, Christina; Horton, Lori; Blaustein, Martin; Galdanes, Karen; Peltier, Richard E.; Chillrud, Steven; Chen, Lung Chi; Ross, James; Nadas, Arthur; Lippmann, Morton; Gordon, Terry

    2014-01-01

    Particulate matter (PM) varies in chemical composition and mass concentration based on a number of factors including location, season, source and particle size. The aim of this study was to evaluate the in vitro and in vivo toxicity of coarse and fine PM simultaneously collected at three rural and two urban sites within the metropolitan New York City (NYC) region during two seasons, and to assess how particle size and elemental composition affect toxicity. Human pulmonary microvascular endothelial (HPMEC-ST1.6R) and bronchial epithelial (BEAS-2B) cell lines were exposed to PM (50 μg/mL) and analyzed for reactive oxygen species (ROS). Mice (FVB/N) were exposed by oropharyngeal aspiration to 50 μg PM, and lavage fluid was analyzed for total protein and PMN influx. The ROS response was greater in the HPMEC-ST1.6R cell line compared to BEAS-2B cells, but the responses were significantly correlated (p<0.01). The ROS response was affected by location, locale and the location:size interaction in both cell lines, and an additional association for size was observed from HPMEC-ST1.6R cells. Urban fine PM generated the highest ROS response. In the mouse model, inflammation was associated with particle size and by a season:size interaction, with coarse PM producing greater PMN inflammation. This study showed that the aerodynamic size, locale (i.e. urban versus rural), and site of PM samples affected the ROS response in pulmonary endothelial and epithelial cells and the inflammatory response in mice. Importantly, these responses were dependent upon the chemical composition of the PM samples. PMID:24255952

  6. Aerodynamic size distribution of suspended particulate matter in the ambient air in the city of Cleveland, Ohio

    NASA Technical Reports Server (NTRS)

    Leibecki, H. F.; King, R. B.; Fordyce, J. S.

    1974-01-01

    The City of Cleveland Division of Air Pollution Control and NASA jointly investigated the chemical and physical characteristics of the suspended particulate matter in Cleveland, and as part of the program, measurements of the particle size distribution of ambient air samples at five urban locations during August and September 1972 were made using high-volume cascade impactions. The distributions were evaluated for lognormality, and the mass median diameters were compared between locations and as a function of resultant wind direction. Junge-type distributions were consistent with dirty continental aerosols. About two-thirds of the suspended particulate matter observed in Cleveland is less than 7 microns in diameter.

  7. Size-resolved measurements of ice nucleating particles at six locations in North America and one in Europe

    NASA Astrophysics Data System (ADS)

    Mason, R. H.; Si, M.; Chou, C.; Irish, V. E.; Dickie, R.; Elizondo, P.; Wong, R.; Brintnell, M.; Elsasser, M.; Lassar, W. M.; Pierce, K. M.; Leaitch, W. R.; MacDonald, A. M.; Platt, A.; Toom-Sauntry, D.; Sarda-Estève, R.; Schiller, C. L.; Suski, K. J.; Hill, T. C. J.; Abbatt, J. P. D.; Huffman, J. A.; DeMott, P. J.; Bertram, A. K.

    2015-07-01

    Detailed information on the size of ice nucleating particles (INPs) may be useful in source identification, modeling their transport in the atmosphere to improve climate predictions, and determining how effectively or ineffectively instrumentation used for quantifying INPs in the atmosphere captures the full INP population. In this study we report immersion-mode INP number concentrations as a function of size at six ground sites in North America and one in Europe. The lowest INP number concentrations were observed at Arctic and alpine locations and the highest at suburban and agricultural locations, consistent with previous studies of INP concentrations in similar environments. We found that 91, 79, and 63 % of INPs had an aerodynamic diameter > 1 μm at ice activation temperatures of -15, -20, and -25 °C, respectively, when averaging over all sampling locations. In addition, 62, 55, and 42 % of INPs were in the coarse mode (> 2.5 μm) at ice activation temperatures of -15, -20, and -25 °C, respectively, when averaging over all sampling locations. These results are consistent with six out of the seven studies in the literature that have focused on the size distribution of INPs in the atmosphere. Taken together, these findings strongly suggest that supermicron and coarse mode aerosol particles are a significant component of the ice nuclei population in many different ground-level environments. Further size-resolved studies of INPs as a function of altitude are required.

  8. HEC-cysteamine particles: influence of particle size, zeta potential, morphology and sulfhydryl groups on permeation enhancing properties.

    PubMed

    Rahmat, Deni; Müller, Christiane; Shahnaz, Gul; Leithner, Katharina; Laffleur, Flavia; Khan, Mohammad Imran; Martien, Ronny; Bernkop Schnürch, Andreas

    2013-09-01

    Within this study, the influence of particle size and zeta potential of hydroxyethyl cellulose-cysteamine particles on permeation enhancing properties was investigated. Particles were prepared by four different methods namely ionic gelation, spray drying, air jet milling and grinding. Particles prepared by grinding were additionally air jet milled. All particles were characterized in terms of particle size and zeta potential. The transport of fluorescein isothiocyanate-dextran 4 (FD4) across Caco-2 cell monolayers in the presence of these particles and the decrease in transepithelial electrical resistance (TEER) was evaluated. The cytotoxic effect of the particles was investigated using resazurin assay. Nanoparticles displaying a zeta potential of 3.3 ± 1.3 mV showed the highest enhancement of FD4 transport among all particles with a 5.83-fold improvement compared to buffer only. Due to the larger particle size, particles generated by grinding exhibited a lower capability in opening of tight junctions compared to smaller particles generated by air jet milling. In addition, the results of the transport studies were supported by the decrease in the TEER. All particle formulations tested were comparatively non-cytotoxic. Accordingly, the zeta potential and particle size showed a significant impact on the opening of tight junctions and hence could play an important role in the design of hydroxyethyl cellulose (HEC)-cysteamine-based nano- and micro-particles as drug delivery systems.

  9. Reinforced polypropylene composites: effects of chemical compositions and particle size.

    PubMed

    Ashori, Alireza; Nourbakhsh, Amir

    2010-04-01

    In this work, the effects of wood species, particle sizes and hot-water treatment on some physical and mechanical properties of wood-plastic composites were studied. Composites of thermoplastic reinforced with oak (Quercus castaneifolia) and pine (Pinus eldarica) wood were prepared. Polypropylene (PP) and maleic anhydride grafted polypropylene (MAPP) were used as the polymer matrix and coupling agent, respectively. The results showed that pine fiber had significant effect on the mechanical properties considered in this study. This effect is explained by the higher fiber length and aspect ratio of pine compared to the oak fiber. The hot-water treated (extractive-free) samples, in both wood species, improved the tensile, flexural and impact properties, but increased the water absorption for 24h. This work clearly showed that lignocellulosic materials in both forms of fiber and flour could be effectively used as reinforcing elements in PP matrix. Furthermore, extractives have marked effects on the mechanical and physical properties.

  10. Particle size distribution and metal content in street sediments

    SciTech Connect

    Viklander, M.

    1998-08-01

    Sediments that had accumulated during the winter season, and which were left at the surface when the snow had melted, were studied with regard to physical and chemical characteristics. The investigation was carried out in the city of Luleaa, which is located in northern Sweden. Sediment samples were collected in the city center and in a housing area at streets with different traffic loads. The results showed that the amount of the sediments at a street surface was evidently affected by the presence of a sidewalk. The street with a sidewalk accumulated much more sediment than the street without a sidewalk. Both of these streets had approximately the same traffic load. The sidewalk also affected the particle size distribution. The content of heavy metals in the sediments varied with the traffic load and the area type. The highest concentration of cadmium, lead, and zinc was found in the street with the highest traffic load.

  11. A global data set of soil particle size properties

    NASA Technical Reports Server (NTRS)

    Webb, Robert S.; Rosenzweig, Cynthia E.; Levine, Elissa R.

    1991-01-01

    A standardized global data set of soil horizon thicknesses and textures (particle size distributions) was compiled. This data set will be used by the improved ground hydrology parameterization designed for the Goddard Institute for Space Studies General Circulation Model (GISS GCM) Model 3. The data set specifies the top and bottom depths and the percent abundance of sand, silt, and clay of individual soil horizons in each of the 106 soil types cataloged for nine continental divisions. When combined with the World Soil Data File, the result is a global data set of variations in physical properties throughout the soil profile. These properties are important in the determination of water storage in individual soil horizons and exchange of water with the lower atmosphere. The incorporation of this data set into the GISS GCM should improve model performance by including more realistic variability in land-surface properties.

  12. Particle-size distribution in soils of West Antarctica

    NASA Astrophysics Data System (ADS)

    Abakumov, E. V.

    2010-03-01

    The particle-size distribution in soils sampled near Russian polar stations in West Antarctica has been studied. It is shown that the soils of the Subantarctic zone (the Bellingshausen Station on King George Island) are characterized by a higher content of silt and clay in the fine earth fraction and by a higher content of the fine earth fraction in comparison with the soils of the proper Antarctic tundra barrens near the Lenin-gradskaya Station and the Antarctic cold desert near the Russkaya Station. In the latter soils, the content of rock fragments is higher than that in the soils of the Antarctic tundra barrens. In the soils of the tundra barrens, a considerable accumulation of fine earth may take place in large cavities (hollows) on the stony bedrock surface. Desert pavements are formed in both types of Antarctic landscapes.

  13. Particle size and X-ray analysis of Feldspar, Calvert, Ball, and Jordan soils

    NASA Technical Reports Server (NTRS)

    Chapman, R. S.

    1977-01-01

    Pipette analysis and X-ray diffraction techniques were employed to characterize the particle size distribution and clay mineral content of the feldspar, calvert, ball, and jordan soils. In general, the ball, calvert, and jordan soils were primarily clay size particles composed of kaolinite and illite whereas the feldspar soil was primarily silt-size particles composed of quartz and feldspar minerals.

  14. Tissue distribution of inhaled micro- and nano-sized cerium oxide particles in rats: results from a 28-day exposure study.

    PubMed

    Geraets, Liesbeth; Oomen, Agnes G; Schroeter, Jeffry D; Coleman, Victoria A; Cassee, Flemming R

    2012-06-01

    In order to obtain more insight into the tissue distribution, accumulation, and elimination of cerium oxide nanoparticles after inhalation exposure, blood and tissue kinetics were investigated during and after a 28-day inhalation study in rats with micro- and nanocerium oxide particles (nominal primary particle size: < 5000, 40, and 5-10 nm). Powder aerosolization resulted in comparable mass median aerodynamic diameter (1.40, 1.17, and 1.02 μm). After single exposure, approximately 10% of the inhaled dose was measured in lung tissue, as was also estimated by a multiple path particle dosimetry model (MPPD). Though small differences in pulmonary deposition efficiencies of cerium oxide were observed, no consistent differences in pulmonary deposition between the micro- and nanoparticles were observed. Each cerium oxide sample was also distributed to tissues other than lung after a single 6-h exposure, such as liver, kidney, and spleen and also brain, testis, and epididymis. No clear particle size-dependent effect on extrapulmonary tissue distribution was observed. Repeated exposure to cerium oxide resulted in significant accumulation of the particles in the (extra)pulmonary tissues. In addition, tissue clearance was shown to be slow, and, overall, insignificant amounts of cerium oxide were eliminated from the body at 48- to 72-h post-exposure. In conclusion, no clear effect of the primary particle size or surface area on pulmonary deposition and extrapulmonary tissue distribution could be demonstrated. This is most likely explained by similar aerodynamic diameter of the cerium oxide particles in air because of the formation of aggregates and irrespective possible differences in surface characteristics. The implications of the accumulation of cerium oxide particles for systemic toxicological effects after repeated chronic exposure via ambient air are significant and require further exploration.

  15. Preparation of large-particle-size monodisperse latexes in space

    NASA Technical Reports Server (NTRS)

    Vanderhoff, J. W.; El-Aasser, M. S.; Micale, F. J.; Sudol, E. D.; Tseng, C. M.; Silwanowicz, A.; Sheu, H. R.; Kornfeld, D. M.

    1986-01-01

    Results are reported of latex sphere polymerization experiments performed on two flights of the Columbia and three flights of the Challenger. The trials were carried out because polymerization of the spheres in space avoids coagulation, nucleation of a new crop of particles, and excessive stirring requirements, and allows growth of spheres larger than 4 microns diam. The Monodisperse Latex Reactor (MLR) held four stirred 100 cc sealed stainless steel cylindrical containers. The mixtures were monitored for the conversion times, volume decreases as spheres formed and the mixture temperature. The spheres were grown from 0.19 micron seeds. Details of the flight preparation efforts are outlined. In flights which did not experience mechanical malfunctions spheres 3-30 microns diam were grown that had noticeably lower size variations than did the ground-based control particles. The 10 micron diam spheres grown on STS-6 were accepted as standard reference material by the NBS and became the first products made in space to be commercially sold on earth; the 30 micron spheres also became NBS standards. The experiments confirmed all projected benefits of producing the spheres in space, as well as provided the opportunity to grow more larger offsize spheres by finishing the growths on earth.

  16. Intrinsic speckle noise in in-line particle holography due to polydisperse and continuous particle sizes

    NASA Astrophysics Data System (ADS)

    Edwards, Philip J.; Hobson, Peter R.; Rodgers, G. J.

    2000-08-01

    In-line particle holography is subject to image deterioration due to intrinsic speckle noise. The resulting reduction in the signal to noise ratio (SNR) of the replayed image can become critical for applications such as holographic particle velocimetry (HPV) and 3D visualisation of marine plankton. Work has been done to extend the mono-disperse model relevant to HPV to include poly-disperse particle fields appropriate for the visualisation of marine plankton. Continuous and discrete particle fields are both considered. It is found that random walk statistics still apply for the poly-disperse case. The speckle field is simply the summation of the individual speckle patters due to each scatter size. Therefor the characteristic speckle parameter (which encompasses particle diameter, concentration and sample depth) is alos just the summation of the individual speckle parameters. This reduces the SNR calculation to the same form as for the mono-disperse case. For the continuous situation three distributions, power, exponential and Gaussian are discussed with the resulting SNR calcuated. The work presented here was performed as part of the Holomar project to produce a working underwater holographic camera for recording plankton.

  17. Control over Particle Size Distribution by Autoclaving Poloxamer-Stabilized Trimyristin Nanodispersions.

    PubMed

    Göke, Katrin; Roese, Elin; Arnold, Andreas; Kuntsche, Judith; Bunjes, Heike

    2016-09-06

    Lipid nanoparticles are under investigation as delivery systems for poorly water-soluble drugs. The particle size in these dispersions strongly influences important pharmaceutical properties like biodistribution and drug loading capacity; it should be below 500 nm for direct injection into the bloodstream. Consequently, small particles with a narrow particle size distribution are desired. Hitherto, there are, however, only limited possibilities for the preparation of monodisperse, pharmaceutically relevant dispersions. In this work, the effect of autoclaving at 121 °C on the particle size distribution of lipid nanoemulsions and -suspensions consisting of the pharmaceutically relevant components trimyristin and poloxamer 188 was studied. Additionally, the amount of emulsifier needed to stabilize both untreated and autoclaved particles was assessed. In our study, four dispersions of mean particle sizes from 45 to 150 nm were prepared by high-pressure melt homogenization. The particle size distribution before and after autoclaving was characterized using static and dynamic light scattering, differential scanning calorimetry, and transmission electron microscopy. Asymmetrical flow field-flow fractionation was used for particle size distribution analyses and for the determination of free poloxamer 188. Upon autoclaving, the mean particle size increased to up to 200 nm, but not proportionally to the initial size. At the same time, the particle size distribution width decreased remarkably. Heat treatment thus seems to be a promising approach to achieve the desired narrow particle size distribution of such dispersions. Related to the lipid content, suspension particles needed more emulsifier for stabilization than emulsion droplets, and smaller particles more than larger ones.

  18. Ultrafine particle size as a tracer for aircraft turbine emissions.

    PubMed

    Riley, Erin A; Gould, Timothy; Hartin, Kris; Fruin, Scott A; Simpson, Christopher D; Yost, Michael G; Larson, Timothy

    2016-08-01

    Ultrafine particle number (UFPN) and size distributions, black carbon, and nitrogen dioxide concentrations were measured downwind of two of the busiest airports in the world, Los Angeles International Airport (LAX) and Hartsfield-Jackson International Airport (ATL - Atlanta, GA) using a mobile monitoring platform. Transects were located between 5 km and 10 km from the ATL and LAX airports. In addition, measurements were taken at 43 additional urban neighborhood locations in each city and on freeways. We found a 3-5 fold increase in UFPN concentrations in transects under the landing approach path to both airports relative to surrounding urban areas with similar ground traffic characteristics. The latter UFPN concentrations measured were distinct in size distributional properties from both freeways and across urban neighborhoods, clearly indicating different sources. Elevated concentrations of Black Carbon (BC) and NO2 were also observed on airport transects, and the corresponding pattern of elevated BC was consistent with the observed excess UFPN concentrations relative to other urban locations.

  19. Vertical Variation of Ice Particle Size in Convective Cloud Tops

    NASA Technical Reports Server (NTRS)

    Van Diedenhoven, Bastiaan; Fridlind, Ann M.; Cairns, Brian; Ackerman, Andrew S.; Yorks, John E.

    2016-01-01

    A novel technique is used to estimate derivatives of ice effective radius with respect to height near convective cloud tops (dr(sub e)/dz) from airborne shortwave reflectance measurements and lidar. Values of dr(sub e)/dz are about -6 micrometer/km for cloud tops below the homogeneous freezing level, increasing to near 0 micrometer/km above the estimated level of neutral buoyancy. Retrieved dr(sub e)/dz compares well with previously documented remote sensing and in situ estimates. Effective radii decrease with increasing cloud top height, while cloud top extinction increases. This is consistent with weaker size sorting in high, dense cloud tops above the level of neutral buoyancy where fewer large particles are present and with stronger size sorting in lower cloud tops that are less dense. The results also confirm that cloud top trends of effective radius can generally be used as surrogates for trends with height within convective cloud tops. These results provide valuable observational targets for model evaluation.

  20. Ultrafine particle size as a tracer for aircraft turbine emissions

    NASA Astrophysics Data System (ADS)

    Riley, Erin A.; Gould, Timothy; Hartin, Kris; Fruin, Scott A.; Simpson, Christopher D.; Yost, Michael G.; Larson, Timothy

    2016-08-01

    Ultrafine particle number (UFPN) and size distributions, black carbon, and nitrogen dioxide concentrations were measured downwind of two of the busiest airports in the world, Los Angeles International Airport (LAX) and Hartsfield-Jackson International Airport (ATL - Atlanta, GA) using a mobile monitoring platform. Transects were located between 5 km and 10 km from the ATL and LAX airports. In addition, measurements were taken at 43 additional urban neighborhood locations in each city and on freeways. We found a 3-5 fold increase in UFPN concentrations in transects under the landing approach path to both airports relative to surrounding urban areas with similar ground traffic characteristics. The latter UFPN concentrations measured were distinct in size distributional properties from both freeways and across urban neighborhoods, clearly indicating different sources. Elevated concentrations of Black Carbon (BC) and NO2 were also observed on airport transects, and the corresponding pattern of elevated BC was consistent with the observed excess UFPN concentrations relative to other urban locations.

  1. Particle Size Concentration Distribution and Influences on Exhaled Breath Particles in Mechanically Ventilated Patients

    PubMed Central

    Chen, Yi-Fang; Huang, Sheng-Hsiu; Wang, Yu-Ling; Chen, Chun-Wan

    2014-01-01

    Humans produce exhaled breath particles (EBPs) during various breath activities, such as normal breathing, coughing, talking, and sneezing. Airborne transmission risk exists when EBPs have attached pathogens. Until recently, few investigations had evaluated the size and concentration distributions of EBPs from mechanically ventilated patients with different ventilation mode settings. This study thus broke new ground by not only evaluating the size concentration distributions of EBPs in mechanically ventilated patients, but also investigating the relationship between EBP level and positive expiratory end airway pressure (PEEP), tidal volume, and pneumonia. This investigation recruited mechanically ventilated patients, with and without pneumonia, aged 20 years old and above, from the respiratory intensive care unit of a medical center. Concentration distributions of EBPs from mechanically ventilated patients were analyzed with an optical particle analyzer. This study finds that EBP concentrations from mechanically ventilated patients during normal breathing were in the range 0.47–2,554.04 particles/breath (0.001–4.644 particles/mL). EBP concentrations did not differ significantly between the volume control and pressure control modes of the ventilation settings in the mechanically ventilated patients. The patient EBPs were sized below 5 µm, and 80% of them ranged from 0.3 to 1.0 µm. The EBPs concentrations in patients with high PEEP (> 5 cmH2O) clearly exceeded those in patients with low PEEP (≤ 5 cmH2O). Additionally, a significant negative association existed between pneumonia duration and EBPs concentration. However, tidal volume was not related to EBPs concentration. PMID:24475230

  2. Measurement of the atmospheric aerosol particle size distribution in a highly polluted mega-city in Southeast Asia (Dhaka-Bangladesh)

    NASA Astrophysics Data System (ADS)

    Salam, Abdus; Mamoon, Hassan Al; Ullah, Md. Basir; Ullah, Shah M.

    2012-11-01

    Aerosol particle size distribution was measured with an aerodynamic particle sizer (APS) spectrometer continuously from January 21 to April 24, 2006 in Dhaka, Bangladesh. Particles number, surface and mass distributions data were stored automatically with Aerosol Instrument Manager (AIM) software on average every half an hour in a computer attached to the APS. The grand total average of number, surface and mass concentrations were 8.2 × 103 ± 7.8 × 103 particles cm-3, 13.3 × 103 ± 11.8 × 103 μm2 cm-3 and 3.04 ± 2.10 mg m-3, respectively. Fine particles with diameter smaller than 1.0 μm aerodynamic diameter (AD) dominated the number concentration, accounted for 91.7% of the total particles indicating vehicular emissions were dominating in Dhaka air either from fossil fuel burning or compressed natural gas (CNGs). The surface and mass concentrations between 0.5 and 1.0 μm AD were about 56.0% and 26.4% of the total particles, respectively. Remarkable seasonal differences were observed between winter and pre-monsoon seasons with the highest monthly average in January and the lowest in April. Aerosol particles in winter were 3.79 times higher for number, 3.15 times for surface and 2.18 times for mass distributions than during the pre-monsoon season. Weekends had lower concentrations than weekdays due to less vehicular traffic in the streets. Aerosol particles concentrations were about 15.0% (ranging from 9.4% to 17.3%) higher during traffic peak hours (6:00am-8:00pm) than off hours (8:00pm-6:00am). These are the first aerosol size distribution measurements with respect to number, surface and mass concentrations in real time at Dhaka, Bangladesh.

  3. Note: Evaluation of slurry particle size analyzers for chemical mechanical planarization process.

    PubMed

    Jang, Sunjae; Kulkarni, Atul; Qin, Hongyi; Kim, Taesung

    2016-04-01

    In the chemical mechanical planarization (CMP) process, slurry particle size is important because large particles can cause defects. Hence, selection of an appropriate particle measuring system is necessary in the CMP process. In this study, a scanning mobility particle sizer (SMPS) and dynamic light scattering (DLS) were compared for particle size distribution (PSD) measurements. In addition, the actual particle size and shape were confirmed by transmission electron microscope (TEM) results. SMPS classifies the particle size according to the electrical mobility, and measures the particle concentration (single particle measurement). On the other hand, the DLS measures the particle size distribution by analyzing scattered light from multiple particles (multiple particle measurement). For the slurry particles selected for evaluation, it is observed that SMPS shows bi-modal particle sizes 30 nm and 80 nm, which closely matches with the TEM measurements, whereas DLS shows only single mode distribution in the range of 90 nm to 100 nm and showing incapability of measuring small particles. Hence, SMPS can be a better choice for the evaluation of CMP slurry particle size and concentration measurements.

  4. Note: Evaluation of slurry particle size analyzers for chemical mechanical planarization process

    NASA Astrophysics Data System (ADS)

    Jang, Sunjae; Kulkarni, Atul; Qin, Hongyi; Kim, Taesung

    2016-04-01

    In the chemical mechanical planarization (CMP) process, slurry particle size is important because large particles can cause defects. Hence, selection of an appropriate particle measuring system is necessary in the CMP process. In this study, a scanning mobility particle sizer (SMPS) and dynamic light scattering (DLS) were compared for particle size distribution (PSD) measurements. In addition, the actual particle size and shape were confirmed by transmission electron microscope (TEM) results. SMPS classifies the particle size according to the electrical mobility, and measures the particle concentration (single particle measurement). On the other hand, the DLS measures the particle size distribution by analyzing scattered light from multiple particles (multiple particle measurement). For the slurry particles selected for evaluation, it is observed that SMPS shows bi-modal particle sizes 30 nm and 80 nm, which closely matches with the TEM measurements, whereas DLS shows only single mode distribution in the range of 90 nm to 100 nm and showing incapability of measuring small particles. Hence, SMPS can be a better choice for the evaluation of CMP slurry particle size and concentration measurements.

  5. An experimental study of nanoparticle focusing with aerodynamic lenses

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoliang; McMurry, Peter H.

    2006-12-01

    High sampling efficiencies of analyte ions, molecules or particles are needed to maximize the sensitivity of mass spectrometers. "Ion funnels", which utilize electrodynamic focusing, have been shown to effectively focus ions with mass-to-charge ratio (m/z) ranging from ~100 to 5000. Focusing efficiencies of ion funnels drop for higher m/z values because very high voltages are needed to overcome the particle inertia. Conventional "aerodynamic lenses" utilize inertia to focus down to 25 nm in diameter (~5 MDa); to date, Brownian diffusion has prevented the effective focusing of particles smaller than this. We recently reported a design procedure that should, in principle, extend focusing with aerodynamic lenses to particles as small as 3 nm (~10 kDa), thereby bridging the gap between the ion funnel and the conventional aerodynamic lenses. In this paper, we report for the first time experimental results for the performance of these new "nanolenses". Measurements were done using spherical oil droplets, proteins, and sodium chloride particles ranging in size from 3 to 30 nm diameter. We found that particle transport efficiencies from atmospheric pressure to vacuum through the aerodynamic lens system were greater than 80% for 10-30 nm particles, and greater than 50% for a ~3.8 nm protein (Lysozyme from chicken egg white, molecular weight 14.3 kDa). Particle beam diameters were about a factor of two greater than predicted by our numerical simulations, but provide clear evidence that the nanolenses effectively focus all three particle types.

  6. The aerodynamics of Manduca sexta: digital particle image velocimetry analysis of the leading-edge vortex.

    PubMed

    Bomphrey, Richard J; Lawson, Nicholas J; Harding, Nicholas J; Taylor, Graham K; Thomas, Adrian L R

    2005-03-01

    Here we present the first digital particle image velocimetry (DPIV) analysis of the flow field around the wings of an insect (the tobacco hawkmoth Manduca sexta, tethered to a 6-component force-moment balance in a wind tunnel). A leading-edge vortex (LEV) is present above the wings towards the end of the downstroke, as the net upward force peaks. Our DPIV analyses and smoke visualisations match the results of previous flow visualisation experiments at midwing, and we extend the experiments to provide the first analysis of the flow field above the thorax. Detailed DPIV measurements show that towards the end of the downstroke, the LEV structure is consistent with that recently reported in free-flying butterflies and dragonflies: the LEV is continuous across the thorax and runs along each wing to the wingtip, where it inflects to form the wingtip trailing vortices. The LEV core is 2-3 mm in diameter (approximately 10% of local wing chord) both at the midwing position and over the centreline at 1.2 m s(-1) and at 3.5 m s(-1) flight speeds. At 1.2 m s(-1) the measured LEV circulation is 0.012+/-0.001 m(2) s(-1) (mean +/-S.D.) at the centreline and 0.011+/-0.001 m(2) s(-1) halfway along the wing. At 3.5 m s(-1) LEV circulation is 0.011+/-0.001 m(2) s(-1) at the centreline and 0.020+/-0.004 m(2) s(-1) at midwing. The DPIV measurements suggest that if there is any spanwise flow in the LEV towards the end of the downstroke its velocity is less than 1 m s(-1). Estimates of force production show that the LEV contributes significantly to supporting body weight during bouts of flight at both speeds (more than 10% of body weight at 1.2 m s(-1) and 35-65% of body weight at 3.5 m s(-1)).

  7. High-solids paint overspray aerosols in a spray painting booth: particle size analysis and scrubber efficiency

    SciTech Connect

    Chan, T.L.; D'arcy, J.B.; Schreck, R.M.

    1986-07-01

    Particle size distributions of high-solids acrylic-enamel paint overspray aerosols were determined isokinetically in a typical downdraft spray painting booth in which a 7-stage cascade impactor was used. Three different industrial paint atomizers were used, and the paint aerosols were characterized before and after a paint both scrubber. The mass median aerodynamic diameter (MMAD) of a metallic basecoat and an acrylic clearcoat paint aerosol from air-atomized spray guns ranged from 4-12 ..mu..m and was dependent on atomization pressure. When the paint booth was operated under controlled conditions simulating those in a plant, the collection efficiency of paint overspray aerosols by a paint scrubber was found to be size dependent and decreased sharply for particles smaller than 2 ..mu..m to as low as 64% for clearcoat paint particles of 0.6 ..mu..m. Improvement in the overall particulate removal efficiency can be achieved by optimizing the spray painting operations so as to produce the least amount of fine overspray paint aerosols less than 2 ..mu..m. Maintaining a higher static pressure drop across the paint both scrubber also will improve scrubber performance.

  8. Comparison of particle size distributions and elemental partitioning from the combustion of pulverized coal and residual fuel oil.

    PubMed

    Linak, W P; Miller, C A; Wendt, J O

    2000-08-01

    U.S. Environmental Protection Agency (EPA) research examining the characteristics of primary PM generated by the combustion of fossil fuels is being conducted in efforts to help determine mechanisms controlling associated adverse health effects. Transition metals are of particular interest, due to the results of studies that have shown cardiopulmonary damage associated with exposure to these elements and their presence in coal and residual fuel oils. Further, elemental speciation may influence this toxicity, as some species are significantly more water-soluble, and potentially more bio-available, than others. This paper presents results of experimental efforts in which three coals and a residual fuel oil were combusted in three different systems simulating process and utility boilers. Particle size distributions (PSDs) were determined using atmospheric and low-pressure impaction as well as electrical mobility, time-of-flight, and light-scattering techniques. Size-classified PM samples from this study are also being utilized by colleagues for animal instillation experiments. Experimental results on the mass and compositions of particles between 0.03 and > 20 microns in aerodynamic diameter show that PM from the combustion of these fuels produces distinctive bimodal and trimodal PSDs, with a fine mode dominated by vaporization, nucleation, and growth processes. Depending on the fuel and combustion equipment, the coarse mode is composed primarily of unburned carbon char and associated inherent trace elements (fuel oil) and fragments of inorganic (largely calcium-alumino-silicate) fly ash including trace elements (coal). The three coals also produced a central mode between 0.8- and 2.0-micron aerodynamic diameter. However, the origins of these particles are less clear because vapor-to-particle growth processes are unlikely to produce particles this large. Possible mechanisms include the liberation of micron-scale mineral inclusions during char fragmentation and burnout

  9. Particle size effects on protein and virus-like particle adsorption on perfusion chromatography media.

    PubMed

    Wu, Yige; Abraham, Dicky; Carta, Giorgio

    2015-01-02

    The resin structure, chromatographic behavior, and adsorption kinetics of proteins and virus-like-particles (VLPs) are studied for POROS HS 20 and POROS HS 50 (23 and 52 μm mean diameter, respectively) to determine the effects of particle size on perfusion chromatography and to determine the predictive ability of available models. Transmission electron microscopy (TEM) and inverse size-exclusion chromatography (iSEC) show similar structures for the two resins, both containing 200-1000 nm pores that transect a network of much smaller pores. For non-binding conditions, trends of the height equivalent to a theoretical plate (HETP) as a function of reduced velocity are consistent with perfusion. The estimated intraparticle flow fractions for these conditions are 0.0018 and 0.00063 for POROS HS 20 and HS 50, respectively. For strong binding conditions, confocal laser scanning microscopy (CLSM) shows asymmetrical intraparticle concentrations profiles and enhanced rates of IgG adsorption on POROS HS 20 at 1000 cm/h. The corresponding effective diffusivity under flow is 2-3 times larger than for non-flow conditions and much larger than observed for POROS HS 50, consistent with available models. For VLPs, however, adsorption is confined to a thin layer near the particle surface for both resins, suggesting that the bound VLPs block the pores.

  10. The permeability of poly-disperse porous media and effective particle size

    NASA Astrophysics Data System (ADS)

    Markicevic, B. I.; Preston, C.; Osterroth, S.; Iliev, O.; Hurwitz, M.

    2015-11-01

    The interactions between the fluid and solid phases in porous media account for the openness and length of the flow path that the fluid needs to travel within. The same reasoning applies for both mono- and poly-disperse media, and is reflected in the adoption of the same permeability models. The only difference is that an effective particle size diameter has to be used for the poly-disperse samples. A filtration experiment is used to form a particle layer, filter cake, consisting of particles of different sizes. Both inflow and outflow particle size distribution are measured by particle counting method, and from their difference, the particle size distribution in the cake is determined. In a set of experiments, the filtration history is altered by changing (i) filtration medium; (ii) suspension flow rate; and (iii) particle concentration, where in all cases investigated the cake permeability remains constant. In order to predict the permeability of poly-disperse cake from the analytical models, the particle size distribution moments are calculated, and the permeability is found for each moment. Comparing the experimental to the analytical permeability values the effective particle size is found, where the permeability calculated by using the harmonic mean of the particle size distribution reproduces the permeability experimental value best. Finally, in the parametric study, reducing the cake porosity and/or lowering the particle retention shifts effective particle size used in the permeability model toward higher moments of the particle size distribution function.

  11. Size, shape and flow characterization of ground wood chip and ground wood pellet particles

    SciTech Connect

    Rezaei, Hamid; Lim, C. Jim; Lau, Anthony; Sokhansanj, Shahab

    2016-07-11

    Size, shape and density of biomass particles influence their transportation, fluidization, rates of drying and thermal decomposition. Pelleting wood particles increases the particle density and reduces the variability of physical properties among biomass particles. In this study, pine chips prepared for pulping and commercially produced pine pellets were ground in a hammer mill using grinder screens of 3.2, 6.3, 12.7 and 25.4mmperforations. Pellets consumed about 7 times lower specific grinding energy than chips to produce the same size of particles. Grinding pellets produced the smaller particles with narrower size distribution than grinding chips. Derived shape factors in digital image analysis showed that chip particles were rectangular and had the aspect ratios about one third of pellet particles. Pellet particles were more circular shape. The mechanical sieving underestimated the actual particle size and did not represent the size of particles correctly. Instead, digital imaging is preferred. Angle of repose and compressibility tests represented the flow properties of ground particles. Pellet particles made a less compacted bulk, had lower cohesion and did flow easier in a pile of particles. In conclusion, particle shape affected the flow properties more than particle size

  12. Size, shape and flow characterization of ground wood chip and ground wood pellet particles

    DOE PAGES

    Rezaei, Hamid; Lim, C. Jim; Lau, Anthony; ...

    2016-07-11

    Size, shape and density of biomass particles influence their transportation, fluidization, rates of drying and thermal decomposition. Pelleting wood particles increases the particle density and reduces the variability of physical properties among biomass particles. In this study, pine chips prepared for pulping and commercially produced pine pellets were ground in a hammer mill using grinder screens of 3.2, 6.3, 12.7 and 25.4mmperforations. Pellets consumed about 7 times lower specific grinding energy than chips to produce the same size of particles. Grinding pellets produced the smaller particles with narrower size distribution than grinding chips. Derived shape factors in digital image analysismore » showed that chip particles were rectangular and had the aspect ratios about one third of pellet particles. Pellet particles were more circular shape. The mechanical sieving underestimated the actual particle size and did not represent the size of particles correctly. Instead, digital imaging is preferred. Angle of repose and compressibility tests represented the flow properties of ground particles. Pellet particles made a less compacted bulk, had lower cohesion and did flow easier in a pile of particles. In conclusion, particle shape affected the flow properties more than particle size« less

  13. Carbon-based phytoplankton size classes retrieved via ocean color estimates of the particle size distribution

    NASA Astrophysics Data System (ADS)

    Kostadinov, Tihomir S.; Milutinović, Svetlana; Marinov, Irina; Cabré, Anna

    2016-04-01

    Owing to their important roles in biogeochemical cycles, phytoplankton functional types (PFTs) have been the aim of an increasing number of ocean color algorithms. Yet, none of the existing methods are based on phytoplankton carbon (C) biomass, which is a fundamental biogeochemical and ecological variable and the "unit of accounting" in Earth system models. We present a novel bio-optical algorithm to retrieve size-partitioned phytoplankton carbon from ocean color satellite data. The algorithm is based on existing methods to estimate particle volume from a power-law particle size distribution (PSD). Volume is converted to carbon concentrations using a compilation of allometric relationships. We quantify absolute and fractional biomass in three PFTs based on size - picophytoplankton (0.5-2 µm in diameter), nanophytoplankton (2-20 µm) and microphytoplankton (20-50 µm). The mean spatial distributions of total phytoplankton C biomass and individual PFTs, derived from global SeaWiFS monthly ocean color data, are consistent with current understanding of oceanic ecosystems, i.e., oligotrophic regions are characterized by low biomass and dominance of picoplankton, whereas eutrophic regions have high biomass to which nanoplankton and microplankton contribute relatively larger fractions. Global climatological, spatially integrated phytoplankton carbon biomass standing stock estimates using our PSD-based approach yield ˜ 0.25 Gt of C, consistent with analogous estimates from two other ocean color algorithms and several state-of-the-art Earth system models. Satisfactory in situ closure observed between PSD and POC measurements lends support to the theoretical basis of the PSD-based algorithm. Uncertainty budget analyses indicate that absolute carbon concentration uncertainties are driven by the PSD parameter No which determines particle number concentration to first order, while uncertainties in PFTs' fractional contributions to total C biomass

  14. Effect of the Size Distribution of Nanoscale Dispersed Particles on the Zener Drag Pressure

    NASA Astrophysics Data System (ADS)

    Eivani, A. R.; Valipour, S.; Ahmed, H.; Zhou, J.; Duszczyk, J.

    2011-04-01

    In this article, a new relationship for the calculation of the Zener drag pressure is described in which the effect of the size distribution of nanoscale dispersed particles is taken into account, in addition to particle radius and volume fraction, which have been incorporated in the existing relationships. Microstructural observations indicated a clear correlation between the size distribution of dispersed particles and recrystallized grain sizes in the AA7020 aluminum alloy. However, the existing relationship to calculate the Zener drag pressure yielded a negligible difference of 0.016 pct between the two structures homogenized at different conditions resulting in totally different size distributions of nanoscale dispersed particles and, consequently, recrystallized grain sizes. The difference in the Zener drag pressure calculated by the application of the new relationship was 5.1 pct, being in line with the experimental observations of the recrystallized grain sizes. Mathematical investigations showed that the ratio of the Zener drag pressure from the new equation to that from the existing equation is maximized when the number densities of all the particles with different sizes are equal. This finding indicates that in the two structures with identical parameters except the size distribution of nanoscale dispersed particles, the one that possesses a broader size distribution of particles, i.e., the number densities of particles with different sizes being equal, gives rise to a larger Zener drag pressure than that having a narrow size distribution of nanoscale dispersed particles, i.e., most of the particles being in the same size range.

  15. Quantum electrodynamics analysis of optical binding in counterpropagating beams and effect of particle size.

    PubMed

    Rodriguez, Justo

    2008-10-01

    A general expression for optical binding energy between particles of any size, in counterpropagating beams with and without interference, is derived using quantum electrodynamics. The effect of particle size on the optically induced interparticle energy surface, which has been the subject of recent research, is explored. Significant changes in this surface when particle size approaches the wavelength of the optical field are revealed. Finally, optically induced particle arrays that may be fabricated with these potentials are briefly discussed.

  16. Background dust emission following grassland fire: a snapshot across the particle-size spectrum highlights how high-resolution measurements enhance detection

    SciTech Connect

    Whicker, Jeffrey J; Martin, Luis M; Field, Jason P; Villegas, Juan C; Brehsears, David D; Law, Darin J; Urgeghe, Anna M

    2009-01-01

    Dust emission rates vary temporally and with particle size. Many studies of dust emission focus on a particular temporal scale and the portion of the particle-size spectrum associated with a single instrument; fewer studies have assessed dust emission across the particle-size spectrum and associated temporal scales using multiple instruments. Particularly lacking are measurements following disturbances such as fire that are high-resolution and focused on finer particles - those with direct implications for human health and potential for long-distance biogeochemical transport - during less windy but more commonly occurring background conditions. We measured dust emissions in unburned and burned semiarid grassland using four different instruments spanning different combinations of temporal resolution and particle-size spectrum: Big Springs Number Eight (BSNE) and Sensit instruments for larger saltating particles, DustTrak instruments for smaller suspended particles, and Total Suspended Particulate (TSP) samplers for measuring the entire range of particle sizes. Unburned and burned sites differed in vegetation cover and aerodynamic roughness, yet surprisingly differences in dust emission rates were only detectable for saltation using BSNE and for smaller aerosols using DustTrak. Our results, surprising in the lack of consistently detected differences, indicate that high-resolution DustTrak measurements offered the greatest promise for detecting differences in background emission rates and that BSNE samplers, which integrate across height, were effective for longer intervals. More generally, our results suggest that interplay between particle size, temporal resolution, and integration across time and height can be complex and may need to be considered more explicitly for effective sampling for background dust emissions.

  17. A note on the stochastic nature of particle cohesive force and implications to threshold friction velocity for aerodynamic dust entrainment

    NASA Astrophysics Data System (ADS)

    Shao, Yaping; Klose, Martina

    2016-09-01

    There is considerable interest to determine the threshold for aeolian dust emission on Earth and Mars. Existing schemes for threshold friction velocity are all deterministic in nature, but observations show that in the dust particle size range the threshold friction velocity scatters strongly due to stochastic inter-particle cohesion. In the real world, there always exists a certain amount of free dust which can be easily lifted from the surface by weak winds or even turbulence, as exemplified by dust devils. It has been proposed in the dust-devil research community, that the pressure drop at dust-devil center may be a major mechanism for dust-devil dust emission, known as the Δp effect. It is questioned here whether the Δp effect is substantial or whether the elevated dust concentration in dust devils is due to free dust emission. A simple analysis indicates that the Δp effect appears to be small and the dust in dust devils is probably due to free dust emission and dust convergence. To estimate free dust emission, it is useful to define a lower limit of dust-particle threshold friction velocity. A simple expression for this velocity is proposed by making assumptions to the median and variance of inter-particle cohesive force. The simple expression is fitted to the data of the Arizona State University Vortex Generator. While considerable uncertainty remains in the scheme, this note highlights the need for additional research on the stochastic nature of dust emission.

  18. Carbon-based phytoplankton size classes retrieved via ocean color estimates of the particle size distribution

    NASA Astrophysics Data System (ADS)

    Kostadinov, T. S.; Milutinović, S.; Marinov, I.; Cabré, A.

    2015-05-01

    Owing to their important roles in biogeochemical cycles, phytoplankton functional types (PFTs) have been the aim of an increasing number of ocean color algorithms. Yet, none of the existing methods are based on phytoplankton carbon (C) biomass, which is a fundamental biogeochemical and ecological variable and the "unit of accounting" in Earth System models. We present a novel bio-optical algorithm to retrieve size-partitioned phytoplankton carbon from ocean color satellite data. The algorithm is based on existing algorithms to estimate particle volume from a power-law particle size distribution (PSD). Volume is converted to carbon concentrations using a compilation of allometric relationships. We quantify absolute and fractional biomass in three PFTs based on size - picophytoplankton (0.5-2 μm in diameter), nanophytoplankton (2-20 μm) and microphytoplankton (20-50 μm). The mean spatial distributions of total phytoplankton C biomass and individual PFTs, derived from global SeaWiFS monthly ocean color data, are consistent with current understanding of oceanic ecosystems, i.e. oligotrophic regions are characterized by low biomass and dominance of picoplankton, whereas eutrophic regions have large biomass to which nanoplankton and microplankton contribute relatively larger fractions. Global spatially integrated phytoplankton carbon biomass standing stock estimates using our PSD-based approach yield on average ~0.2-0.3 Gt of C, consistent with analogous estimates from two other ocean color algorithms, and several state-of-the-art Earth System models. However, the range of phytoplankton C biomass spatial variability globally is larger than estimated by any other models considered here, because the PSD-based algorithm is not a priori empirically constrained and introduces improvement over the assumptions of the other approaches. Satisfactory in situ closure observed between PSD and POC measurements lends support to the theoretical basis of the PSD-based algorithm

  19. Event-based total suspended sediment particle size distribution model

    NASA Astrophysics Data System (ADS)

    Thompson, Jennifer; Sattar, Ahmed M. A.; Gharabaghi, Bahram; Warner, Richard C.

    2016-05-01

    One of the most challenging modelling tasks in hydrology is prediction of the total suspended sediment particle size distribution (TSS-PSD) in stormwater runoff generated from exposed soil surfaces at active construction sites and surface mining operations. The main objective of this study is to employ gene expression programming (GEP) and artificial neural networks (ANN) to develop a new model with the ability to more accurately predict the TSS-PSD by taking advantage of both event-specific and site-specific factors in the model. To compile the data for this study, laboratory scale experiments using rainfall simulators were conducted on fourteen different soils to obtain TSS-PSD. This data is supplemented with field data from three construction sites in Ontario over a period of two years to capture the effect of transport and deposition within the site. The combined data sets provide a wide range of key overlooked site-specific and storm event-specific factors. Both parent soil and TSS-PSD in runoff are quantified by fitting each to a lognormal distribution. Compared to existing regression models, the developed model more accurately predicted the TSS-PSD using a more comprehensive list of key model input parameters. Employment of the new model will increase the efficiency of deployment of required best management practices, designed based on TSS-PSD, to minimize potential adverse effects of construction site runoff on aquatic life in the receiving watercourses.

  20. Particle-size segregation in dense granular avalanches

    NASA Astrophysics Data System (ADS)

    Gray, John Mark Nicholas Timm; Gajjar, Parmesh; Kokelaar, Peter

    2015-01-01

    Particles of differing sizes are notoriously prone to segregate, which is a chronic problem in the manufacture of a wide variety of products that are used by billions of people worldwide every day. Segregation is the single most important factor in product non-uniformity, which can lead to significant handling problems as well as complete batches being discarded at huge financial loss. It is generally regarded that the most important mechanism for segregation is the combination of kinetic sieving and squeeze expulsion in shallow granular avalanches. These free-surface flows are more common than one might expect, often forming part of more complicated flows in drums, heaps and silos, where there is mass exchange with underlying regions of static or slowly moving grains. The combination of segregation and solid-fluid granular phase transitions creates incredibly complicated and beautiful patterns in the resulting deposits, but a full understanding of such effects lies beyond our capabilities at present. This paper reviews recent advances in our ability to model the basic segregation processes in a single avalanche (without mass exchange) and the subtle feedback effects that they can have on the bulk flow. This is particularly important for geophysical applications, where segregation can spontaneously self-channelize and lubricate the flow, significantly enhancing the run-out of debris-flows, pyroclastic flows, rock-falls and snow-slab avalanches.

  1. Vortex Particle-Mesh simulations of Vertical Axis Wind Turbine flows: from the blade aerodynamics to the very far wake

    NASA Astrophysics Data System (ADS)

    Chatelain, P.; Duponcheel, M.; Caprace, D.-G.; Marichal, Y.; Winckelmans, G.

    2016-09-01

    A Vortex Particle-Mesh (VPM) method with immersed lifting lines has been developed and validated. Based on the vorticity-velocity formulation of the Navier-Stokes equations, it combines the advantages of a particle method and of a mesh-based approach. The immersed lifting lines handle the creation of vorticity from the blade elements and its early development. LES of Vertical Axis Wind Turbine (VAWT) flows are performed. The complex wake development is captured in details and over very long distances: from the blades to the near wake coherent vortices, then through the transitional ones to the fully developed turbulent far wake (beyond 10 rotor diameters). The statistics and topology of the mean flow are studied. The computational sizes also allow insights into the detailed unsteady vortex dynamics, including some unexpected topological flow features.

  2. Effect of UV radiations to control particle size of Mn-Zn spinel ferrite nano-particles

    NASA Astrophysics Data System (ADS)

    Ameen Ramiza, F.; Ajmal, S. K.; Khan, M. B.; Nasim, A.; Jamil, Y.; Kashif, K.; Amira, S.

    2016-08-01

    MnxZn1-xFe2O4 (0.0 < x < 1.0) ferrite nano particles were synthesized for concentration varying from 0.27 to 0.87 to obtain chemically homogenous powder for obtaining fine particle size by co precipitation technique. Keeping in view the interest of scientists for particle size, the present work focus on the impact of UV radiation to control the particle size of prepared fine magnetic particles. The particles were digested for ninety minutes at a temperature of 90oC. The samples were divided into four equal quantities and were subjected to different doses of UV radiation. The chemically produced samples of Mn-Zn ferrite nano particles were analyzed by XRD which confirmed cubic spinel structure of the material. The average crystallite size (t), lattice parameter (a) and other structural parameters of UV-irradiated MnxZni-xFe2O4 spinel ferrite were calculated from XRD data. The spinel peak of the irradiated sample when compared with the control sample, shifted from 35.38 to 35.15. In few samples, additional peaks supporting the ferrite structure were also observed. The variation in the particle sizes observed for various doses of UV irradiation were in the range of 17.6 to 6.2 nm, whereas the particle size of the control was 8.82nm. The experiment was repeated for different concentrations, at the same digestion temperature and time revealed the similar results indicating that UV radiations can have a remarkable effect to control the phase and size of nano size fine magnetic ferrite particles. The present work successfully document the impact of UV to control the particle size.

  3. Size distribution of radioactive particles collected at Tokai, Japan 6 days after the nuclear accident.

    PubMed

    Miyamoto, Yutaka; Yasuda, Kenichiro; Magara, Masaaki

    2014-06-01

    Airborne radioactive particles released by the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident in 2011 were collected with a cascade low-pressure impactor at the Japan Atomic Energy Agency (JAEA) in Tokai, Japan, 114 km south of the FDNPP. Size-fractionated samples were collected twice, in the periods of March 17-April 1, 2011, and May 9-13, 2011. These size-fractionated samplings were carried out in the earliest days at a short distance from the FDNPP. Radioactivity of short-lived nuclides (several ten days of half-life) was determined as well as (134)Cs and (137)Cs. The elemental composition of size-fractionated samples was also measured. In the first collection, the activity median aerodynamic diameter (AMAD) of (129m)Te, (140)Ba, (134)Cs, (136)Cs and (137)Cs was 1.5-1.6 μm, while the diameter of (131)I was 0.45 μm. The diameters of (134)Cs and (137)Cs in the second collection were expressed as three peaks at <0.5 μm, 0.94 μm, and 7.8 μm. The (134)Cs/(137)Cs ratio of the first collection was 1.02 in total, but the ratio in the fine fractions was 0.91. A distribution map of (134)Cs/(137)Cs - (136)Cs/(137)Cs ratios was helpful in understanding the change of radioactive Cs composition. The Cs composition of size fractions <0.43 μm and the composition in the 1.1-2.1 μm range (including the AMAD of 1.5-1.6 μm) were similar to the calculated compositions of fuels in the reactors No. 1 and No. 3 at the FDNPP using the ORIGEN-II code. The Cs composition collected in May, 2011 was similar to the calculation results of reactor No. 2 fuel composition. The change of Cs composition implies that the radioactive Cs was released from the three reactors at the FDNPP via different processes.

  4. Size effect on solid solid reaction growth between Cu film and Se particles

    NASA Astrophysics Data System (ADS)

    Kaito, Chihiro; Nonaka, Akira; Kimura, Seiji; Suzuki, Nobuhiko; Saito, Yoshio

    1998-03-01

    A recently developed experimental method of producing a compound by making use of the reaction between thin film and ultrafine particles has been used for copper selenide crystal formation to elucidate the particle size effect on the reaction process. In the case of reaction between Cu film Se particles with size of μm order, CuSe crystals were grown on Se particles by the diffusion of predominantly Cu atoms. In the case of Se particles of the order of 100 nm, amorphous Se particles changed into copper selenide particles by the mutual diffusion of Cu and Se atoms. If the size of Se particles was less than 20 nm, a part of the Cu film changed to copper selenide crystal due to the diffusion of Se atoms to the Cu film. Morphological differences have also been shown and discussed to be the result of the particle size effect.

  5. Retrieval of particle size distribution in the dependent model using the moment method.

    PubMed

    Sun, Xiaogang; Tang, Hong; Dai, Jingmin

    2007-09-03

    The problem of determining particle size distribution using the moment method in the spectral extinction technique is studied. The feasibility and reliability of the retrieval of spherical particle size distribution using the moment method are investigated. The single spherical particle extinction efficiency, which is derived theoretically using the Mie's solution to Maxwell's equation, is approximated with a higher order polynomial in order to apply the moment method. Simulation and experimental results indicate that a fairly reasonable representation of the particle size distribution can be obtained using the moment method in the dependent model algorithm. The method has advantages of simplicity, rapidity, and suitability for in-line particle size measurement.

  6. Multifrequency Retrieval of Cloud Ice Particle Size Distributions

    DTIC Science & Technology

    2005-01-01

    calculate the scattering by nonspherical particles. The T - matrix code was obtained from Barber and Hill (1990) for axi-symmetric oblate spheroids...wave, the T - matrix code calculates the scattering characteristics for a nonspherical particle. The T-matrix nonspherical ice particles are oblate

  7. Mie Scattering by Ensembles of Particles with Very Large Size Parameters

    NASA Astrophysics Data System (ADS)

    Wolf, S.

    2006-10-01

    MIEX is a computer program for the simulation of Mie scattering in case of arbitrarily large size parameters. The elements of the scattering matrix, efficiency factors as well as the corresponding cross sections, the albedo and the scattering asymmetry parameter are calculated. Single particles as well as particle ensembles consisting of several components and particle size distributions can be considered.

  8. Superselective Particle Embolization Enhances Efficacy of Radiofrequency Ablation: Effects of Particle Size and Sequence of Action

    SciTech Connect

    Tanaka, Toshihiro; Isfort, Peter; Braunschweig, Till Westphal, Saskia; Woitok, Anna; Penzkofer, Tobias Bruners, Philipp; Kichikawa, Kimihiko; Schmitz-Rode, Thomas Mahnken, Andreas H.

    2013-06-15

    Purpose. To evaluate the effects of particle size and course of action of superselective bland transcatheter arterial embolization (TAE) on the efficacy of radiofrequency ablation (RFA). Methods. Twenty pigs were divided into five groups: group 1a, 40-{mu}m bland TAE before RFA; group 1b, 40-{mu}m bland TAE after RFA; group 2a, 250-{mu}m bland TAE before RFA; group 2b, 250-{mu}m bland TAE after RFA and group 3, RFA alone. A total of 40 treatments were performed with a combined CT and angiography system. The sizes of the treated zones were measured from contrast-enhanced CTs on days 1 and 28. Animals were humanely killed, and the treated zones were examined pathologically. Results. There were no complications during procedures and follow-up. The short-axis diameter of the ablation zone in group 1a (mean {+-} standard deviation, 3.19 {+-} 0.39 cm) was significantly larger than in group 1b (2.44 {+-} 0.52 cm; P = 0.021), group 2a (2.51 {+-} 0.32 cm; P = 0.048), group 2b (2.19 {+-} 0.44 cm; P = 0.02), and group 3 (1.91 {+-} 0.55 cm; P < 0.001). The greatest volume of ablation was achieved by performing embolization with 40-{mu}m particles before RFA (group 1a; 20.97 {+-} 9.65 cm{sup 3}). At histology, 40-{mu}m microspheres were observed to occlude smaller and more distal arteries than 250-{mu}m microspheres. Conclusion. Bland TAE is more effective before RFA than postablation embolization. The use of very small 40-{mu}m microspheres enhances the efficacy of RFA more than the use of larger particles.

  9. In situ particle size distributions and volume concentrations from a LISST-100 laser particle sizer and a digital floc camera

    NASA Astrophysics Data System (ADS)

    Mikkelsen, Ole A.; Hill, Paul S.; Milligan, Timothy G.; Chant, Robert J.

    2005-10-01

    A LISST-100 in situ laser particle sizer was deployed together with a digital floc camera during field work in the Newark Bay area (USA) and along the Apennine margin (the Adriatic Sea, Italy). The purpose of these simultaneous deployments was to investigate how well in situ particle (floc) sizes and volume concentrations from the two different instruments compared. In the Adriatic Sea the two instruments displayed the same temporal variation, but the LISST provided lower estimates of floc size by a factor of 2-3, compared to the DFC. In the Newark Bay area, the LISST provided higher values of floc size by up to a factor of 2. When floc size was computed using only the overlapping size bins from the two instruments the discrepancy disappeared. The reason for the discrepancy in size was found to be related to several issues: First, the LISST measured particles in the 2.5-500 μm range, whereas the camera measured particles in the 135-9900 μm range, so generally the LISST should provide lower estimates of floc size, as it measures the smaller particles. Second, in the Newark Bay area scattering from particles >500 μm generally caused the LISST to overestimate the volume of particles in its largest size bin, thereby increasing apparent floc size. Relative to the camera, the LISST generally provided estimates of total floc volume that were lower by a factor of 3. Factors that could explain this discrepancy are errors arising from the accuracy of the LISST volume conversion coefficient and image processing. Regardless of these discrepancies, the shapes of the size spectra from the instruments were similar in the regions of overlap and could be matched by multiplying with an appropriate correction coefficient. This facilitated merging of the size spectra from the LISST and the DFC, yielding size spectra in the 2.5-9900 μm range. The merged size spectra generally had one or more peaks in the coarse end of the spectrum, presumably due to the presence of flocs. The fine

  10. Global Retrieval of Cloud Particle Size and Optical Thickness Using ISCCP Data

    NASA Technical Reports Server (NTRS)

    Welch, Ronald M.; Han, Qingyuan

    1998-01-01

    The primary thrust of this investigation is to develop an algorithm to retrieve cloud particle sizes using ISCCP data. The research under this grant has been successful in obtaining initial results of global distribution of ice-particle sizes. Further research about possible problems caused by nonsphericity of ice particle sizes is currently underway. An algorithm of retrieving ice-cloud particle sizes using ISCCP CX data has been developed. The first survey of ice-particle size in a near-global scale has been completed. Comparison with in situ measurements of ice crystal sizes during FIRE I shows good agreement. The initial results show that the global mean size of ice crystals (De) is about 60 micron. This result is consistent with the range of in situ measurements all over the world if definitions of effective particle size are unified (see next section). The survey also shows that there is no distinct difference of ice-particle sizes between continental and maritime ice-clouds. There are many different definitions of effective particle size used in ice-cloud research. Simple comparisons between values of in situ measurement and satellite remote sensing are misleading and may lead to incorrect conclusions. We reviewed different definitions of effective particle sizes used in the literature and compared their relative magnitudes.

  11. Preparation of gold nanoparticles and determination of their particles size via different methods

    SciTech Connect

    Iqbal, Muhammad; Usanase, Gisele; Oulmi, Kafia; Aberkane, Fairouz; Bendaikha, Tahar; Fessi, Hatem; Zine, Nadia; Agusti, Géraldine; Errachid, El-Salhi; Elaissari, Abdelhamid

    2016-07-15

    Graphical abstract: Preparation of gold nanoparticles via NaBH{sub 4} reduction method, and determination of their particle size, size distribution and morphology by using different techniques. - Highlights: • Gold nanoparticles were synthesized by NaBH{sub 4} reduction method. • Excess of reducing agent leads to tendency of aggregation. • The particle size, size distribution and morphology were investigated. • Particle size was determined both experimentally as well as theoretically. - Abstract: Gold nanoparticles have been used in various applications covering both electronics, biosensors, in vivo biomedical imaging and in vitro biomedical diagnosis. As a general requirement, gold nanoparticles should be prepared in large scale, easy to be functionalized by chemical compound of by specific ligands or biomolecules. In this study, gold nanoparticles were prepared by using different concentrations of reducing agent (NaBH{sub 4}) in various formulations and their effect on the particle size, size distribution and morphology was investigated. Moreover, special attention has been dedicated to comparison of particles size measured by various techniques, such as, light scattering, transmission electron microscopy, UV spectrum using standard curve and particles size calculated by using Mie theory and UV spectrum of gold nanoparticles dispersion. Particle size determined by various techniques can be correlated for monodispersed particles and excess of reducing agent leads to increase in the particle size.

  12. Use of a generalized Stokes number to determine the aerodynamic capture efficiency of non-Stokesian particles from a compressible gas flow

    NASA Technical Reports Server (NTRS)

    Israel, R.; Rosner, D. E.

    1983-01-01

    The aerodynamic capture efficiency of small but nondiffusing particles suspended in a high-speed stream flowing past a target is known to be influenced by parameters governing small particle inertia, departures from the Stokes drag law, and carrier fluid compressibility. By defining an effective Stokes number in terms of the actual (prevailing) particle stopping distance, local fluid viscosity, and inviscid fluid velocity gradient at the target nose, it is shown that these effects are well correlated in terms of a 'standard' (cylindrical collector, Stokes drag, incompressible flow, sq rt Re much greater than 1) capture efficiency curve. Thus, a correlation follows that simplifies aerosol capture calculations in the parameter range already included in previous numerical solutions, allows rational engineering predictions of deposition in situations not previously specifically calculated, and should facilitate the presentation of performance data for gas cleaning equipment and aerosol instruments.

  13. Understanding particle size and distance driven competition of interparticle interactions and effective single-particle anisotropy

    NASA Astrophysics Data System (ADS)

    Pacakova, B.; Mantlikova, A.; Niznansky, D.; Kubickova, S.; Vejpravova, J.

    2016-05-01

    Magnetic response of single-domain nanoparticles (NPs) in concentrated systems is strongly affected by mutual interparticle interactions. However, particle proximity significantly influences single-particle effective anisotropy. To solve which of these two phenomena plays a dominant role in the magnetic response of real NP systems, systematic study on samples with well-defined parameters is required. In our work, we prepared a series of nanocomposites constituted of highly-crystalline and well-isolated CoFe2O4 NPs embedded in an amorphous SiO2 matrix using a single-molecule precursor method. This preparation method enabled us to reach a wide interval of particle size and concentration. We observed that the characteristic parameters of the single-domain state (coercivity, blocking temperature) and dipole-dipole interaction energy ({{E}\\text{d-\\text{d}}} ) scaled with each other and increased with increasing {{≤ft({{d}\\text{XRD}}/r\\right)}3} , where d XRD was the NP diameter and r was the interparticle distance. Our results are in excellent agreement with Monte-Carlo simulations of the particle growth. Moreover, we demonstrated that the contribution of {{E}\\text{d-\\text{d}}} acting as an additional energetic barrier to the superspin reversal or as an average static field did not sufficiently explain how the concentrated NP systems responded to an external magnetic field. Alternations in the blocking temperature and coercivity of our NP systems accounted for reformed relaxations of the NP superspins and modified effective anisotropy energy of the interacting NPs. Therefore, the concept of modified NP effective anisotropy explains the magnetic response of our concentrated NP systems better than the concept of the energy barrier influenced by interparticle interactions.

  14. Particle size distributions of oil mists in workplace atmospheres and their exposure concentrations to workers in a fastener manufacturing industry.

    PubMed

    Chen, Mei-Ru; Tsai, Perng-Jy; Chang, Chih-Ching; Shih, Tung-Sheng; Lee, Wen-Jhy; Liao, Pao-Chi

    2007-07-19

    This study was set out to characterize size distributions of oil mists in three workplace atmospheres of the forming, threading, and heat treatment in a fastener manufacturing industry and to assess their exposures to workers. Particle size segregating samplings were conducted on the workplace atmospheres of the three selected industrial processes by using the modified Marple 8-stage cascade impactor (m-Marple). We found that mass median aerodynamic diameter (MMAD) of the fine mode and coarse mode fell to the range 0.309-0.501 microm and 8.16-13.0 microm, respectively. The fractions of inhaled particles exposed to different regions of the respiratory tracts found that the alveolar region was consistently higher than both head and tracheobronchial regions in all three studied exposure groups. Personal inhalable oil mist samplings were conducted on workers in the three selected processes revealed their exposure levels as: threading workers (2.11 mg/m3)>forming workers (1.58 mg/m3)>heat treatment workers (0.0801 mg/m3). The estimated respirable exposure concentrations for both forming and threading workers (1.34 mg/m3 and 1.40 mg/m3, respectively) were higher than the level known for "increased risk of pulmonary injury" (0.20 mg/m3) suggesting that appropriate control measures should be taken to reduce their exposures to the oil mists of the respirable fraction immediately.

  15. Assessment of active pharmaceutical ingredient particle size in tablets by Raman chemical imaging validated using polystyrene microsphere size standards.

    PubMed

    Kuriyama, Atsushi; Ozaki, Yukihiro

    2014-04-01

    Particle size is a critical parameter for controlling pharmaceutical quality. The aim of this study was to assess the size of the micrometer-scale active pharmaceutical ingredients (API) in tablets using Raman chemical imaging and to understand the effects of formulation on particle size. Model tablets containing National Institute of Standards and Technology traceable polystyrene microsphere size standards were developed to determine the binarization threshold value of Raman chemical images for API particle sizing in specific formulations and processes. Three sets of model tablets containing 5, 10, and 15 μm polystyrene microspheres, used to mimic API, were prepared using a commercial tablet formulation (Ebastel tablets, mean API particle size was about 5 μm). Raman mapping with a 50× objective (NA, 0.75) was applied to tablet cross-sections, and particle size of polystyrene microspheres was estimated from binary images using several binarization thresholds. Mean particle size for three sets of polystyrene microspheres showed good agreement between pre- and postformulation (the slope = 1.024, R = 1.000) at the specific threshold value ((mean + 0.5σ) of the polystyrene-specific peak intensity histogram), regardless of particle agglomeration, tablet surface roughness, and laser penetration depth. The binarization threshold value showed good applicability to Ebastel tablets, where the API-specific peak intensity histogram showed a pattern similar to that of polystyrene microspheres in model tablets. The model tablets enabled determination of an appropriate binarization threshold for assessing the mean particle size of micrometer-scale API in tablets by utilizing the unique physicochemical properties of polystyrene microspheres.

  16. Performance and operating envelope of imaging and scattering particle sizing instruments

    NASA Technical Reports Server (NTRS)

    Hovenac, Edward A.

    1987-01-01

    Scattering and imaging type particle sizing instruments are analyzed in terms of their ability to make accurate determinations of particle size distributions, number density, and total mass. Sources of counting and sizing errors are explained. Ways are described of identifying these errors and how these errors can effect the measurements.

  17. Effect of pressure and fat content on particle sizes in microfluidized milk.

    PubMed

    Olson, D W; White, C H; Richter, R L

    2004-10-01

    Average diameters and particle size distributions in fluid milks with different fat contents and subjected to various homogenization pressures with a "microfluidizer" were evaluated. Skim, 2%, and whole milks were microfluidized at 50, 100, 150, and 200 MPa. Cream containing 41% milk fat was microfluidized at 50, 100, and 150 MPa. Particle sizes were determined by laser light scattering. As microfluidization pressure was increased from 50 to 100 MPa, particle sizes in skim, 2%, and whole milks decreased. Microfluidization at pressures greater than 100 MPa had little additional effect on reducing the particle sizes in skim and 2% milks compared with microfluidization at 100 MPa, but the particle sizes in whole milk increased as the microfluidization pressure was increased from 100 to 200 MPa due to formation of homogenization clusters. The particle sizes in cream increased as the microfluidization pressure was increased from 50 to 150 MPa. When the microfluidization pressure was held constant, the particle sizes increased as the milk fat concentration was increased. The coefficients of variations of the volume-weighted particle size distributions for cream were higher than for skim, 2%, and whole milks. Larger "big" particles and smaller "small" particles were formed in whole milk after microfluidization at 200 MPa than at 100 MPa. Although microfluidization can be used to produce small particles in skim, 2%, and whole milks, a higher than optimum pressure (above 100 MPa) applied to whole milk will not lead to the minimum d(43) (volume-weighted average diameter) due to formation of clusters.

  18. Research on bimodal particle extinction coefficient during Brownian coagulation and condensation for the entire particle size regime

    NASA Astrophysics Data System (ADS)

    Tang, Hong; Lin, Jian-Zhong

    2011-12-01

    The extinction coefficient of atmospheric aerosol particles influences the earth's radiation balance directly or indirectly, and it can be determined by the scattering and absorption characteristics of aerosol particles. The problem of estimating the change of extinction coefficient due to time evolution of bimodal particle size distribution is studied, and two improved methods for calculating the Brownian coagulation coefficient and the condensation growth rate are proposed, respectively. Through the improved method based on Otto kernel, the Brownian coagulation coefficient can be expressed simply in powers of particle volume for the entire particle size regime based on the fitted polynomials of the mean enhancement function. Meanwhile, the improved method based on Fuchs-Sutugin kernel is developed to obtain the condensation growth rate for the entire particle size regime. And then, the change of the overall extinction coefficient of bimodal distributions undergoing Brownian coagulation and condensation can be estimated comprehensively for the entire particle size regime. Simulation experiments indicate that the extinction coefficients obtained with the improved methods coincide fairly well with the true values, which provide a simple, reliable, and general method to estimate the change of extinction coefficient for the entire particle size regime during the bimodal particle dynamic processes.

  19. Effect of particle size on the performance of batchwise centrifugal filtration.

    PubMed

    Hwang, K J

    2001-01-01

    The effect of particle size distribution on the performance of batchwise centrifugal filtration is studied. By analyzing the velocity of particles in a filter, a numerical program is designed for simulating the migration and deposition of particles. The particle size distributions and the average specific filtration resistances of cake are then estimated under various rotating speeds of the centrifuge. A large deviation of particle concentration profiles in the filter chamber will occur if the particle size distribution is not taken into consideration. A more heterogeneous cake will form under a lower rotating speed due to the sedimentation effect of particles. The predicted results of particle size distribution and average specific filtration resistance of cake agree well with the available experimental data.

  20. Measurement of asphaltene particle size distributions in crude oils diluted with n-heptane

    SciTech Connect

    Ferworn, K.A.; Svrcek, W.Y.; Mehrotra, A.K. )

    1993-05-01

    The formation and growth of asphaltene particles from heavy crude oils diluted with n-heptane at 22 C and atmospheric pressure was studied using a laser particle analyzer. The results obtained with six crude oil samples indicate that the asphaltene precipitation is an instantaneous process leading to a unimodal, log-normal distribution. At typical laboratory conditions, the particles remained essentially unaltered in size and population density. A vast majority of the particles were noted to be far from round in shape, with the mean particle size ranging from 4.5 to 291 [mu]m. It was found that the oil-to-diluent ratio is an important parameter in determining the size of the generated asphaltene particles; higher dilution ratios yielded larger particles. The mean asphaltene particle size was also found to increase with the average molar mass and the asphaltene content of crude oils.

  1. Comparison and assessment of four sediment particle-size analysis methodologies

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Sediment particle-size analysis is a fundamental component of a wide variety of environmental disciplines such as sediment transport dynamics, subsurface and groundwater flow, lacustrine depositional history, and nutrient transport. There are several readily available methods for measuring particle ...

  2. Influence of particle size on physical and sensory attributes of mango pulp powder

    NASA Astrophysics Data System (ADS)

    Sharma, M.; Kadam, D. M.; Chadha, S.; Wilson, R. A.; Gupta, R. K.

    2013-09-01

    The present investigation was aimed to observe the effect of particle size on physical, sensory and thermal properties of foam-mat dried mango pulp powder. Mango pulp of Dussehri variety was foam-mat dried using 3% egg white at 65ºC. Dried foam-mats were pulverized and passed through a sieve shaker for obtaining three grades of powder with 50, 60, and 85 mesh size sieves. The particle size of these samples measured using laser diffraction particle size analyzer ranged from 191.26 to 296.19 μm. The data was analysed statistically using ANOVA of SAS. There was a linear increase in lightness (`L' value) with a decrease in particle size, however, `a' value decreased with a decrease in particle size, indicating the decrease in redness. An increase in bulk density and decrease in water solubility index and water absorption index % were observed with a decrease in particle size. Particle size had a significant effect on sensory parameters. Particle size in the range of 258.01 to 264.60μmwas found most acceptable with respect to sensory characteristics. This finding can be exploited for various commercial applicationswhere powder quality is dependent on the particle size and has foremost priority for end users.

  3. Size and temperature dependent plasmons of quantum particles

    NASA Astrophysics Data System (ADS)

    Xiao, Mufei; Rakov, Nikifor

    2015-08-01

    This work reports on the influences of temperature changes on plasmons of metallic particles that are so small that electric carriers in the conduction band are forced to be at discrete sub-bands due to quantum confinement. In the framework of the electron-in-a-box model and with an every-electron-count computational scheme, the spatial electric distribution inside the particle is calculated. In the calculations, the intra-subband fluctuations are taken into account. The numerical results have shown that the small-particle plasmon frequency shifts with the temperature. The findings suggest that it would be possible to control the plasmons of quantum particles externally.

  4. Size matters in the water uptake and hygroscopic growth of atmospherically relevant multicomponent aerosol particles.

    PubMed

    Laskina, Olga; Morris, Holly S; Grandquist, Joshua R; Qin, Zhen; Stone, Elizabeth A; Tivanski, Alexei V; Grassian, Vicki H

    2015-05-14

    Understanding the interactions of water with atmospheric aerosols is crucial for determining the size, physical state, reactivity, and climate impacts of this important component of the Earth's atmosphere. Here we show that water uptake and hygroscopic growth of multicomponent, atmospherically relevant particles can be size dependent when comparing 100 nm versus ca. 6 μm sized particles. It was determined that particles composed of ammonium sulfate with succinic acid and of a mixture of chlorides typical of the marine environment show size-dependent hygroscopic behavior. Microscopic analysis of the distribution of components within the aerosol particles show that the size dependence is due to differences in the mixing state, that is, whether particles are homogeneously mixed or phase separated, for different sized particles. This morphology-dependent hygroscopicity has consequences for heterogeneous atmospheric chemistry as well as aerosol interactions with electromagnetic radiation and clouds.

  5. An experimental and theoretical study of the seepage migration of suspended particles with different sizes

    NASA Astrophysics Data System (ADS)

    Bai, Bing; Xu, Tao; Guo, Zhiguang

    2016-12-01

    This study experimentally investigates the effect of particle size, particle concentration and flow velocity on the migration of suspended particles of size 1.02-47 μm in porous media. The results show that at the same flow velocity, the peak values of the breakthrough curves decrease and corresponding pore volumes increase slightly with increasing particles size. The migration velocity of smaller suspended particles is even greater than water flow velocity, which is attributed to the size exclusion effect. With increase of the injected particle concentration, the deposition coefficients of small single particles increase at first and then tend to a steady state or even decrease slightly, explained by the maximum retention concentration. The dispersivity of small particles decreases with increasing velocity. However, at a high flow velocity, the hydrodynamic dispersivity becomes increasingly dominant with the increase of particle size. The deposition coefficients for large-sized particles are higher than those for small-sized particles, which is attributed to considerable mass removal due to straining. An analytical solution, considering the release effect of sorbed particles, is developed to account for the one-dimensional flow and dispersive effect using a source function method, and then three transport parameters—dispersivity, deposition coefficient and release coefficient—are fitted using the experimental results. Finally, suspended-particle migration is predicted by the proposed model for short-time constant-concentration injection and repeated three-pulse injection. Overall, particle size has a significant effect on the seepage migration parameters of suspended particles in porous media such as the particle velocity, dispersivity and deposition coefficient.

  6. Simultaneous 3D location and size measurement of bubbles and sand particles in a flow using interferometric particle imaging.

    PubMed

    Ouldarbi, L; Pérret, G; Lemaitre, P; Porcheron, E; Coëtmellec, S; Gréhan, G; Lebrun, D; Brunel, M

    2015-09-01

    We present a system to characterize a triphasic flow in a 3D volume (air bubbles and solid irregular particles in water) using only one CCD sensor. A cylindrical interferometric out-of-focus imaging setup is used to determine simultaneously the 3D position and the size of bubbles and irregular sand particles in a flow. The 3D position of the particles is deduced from the ellipticity of their out-of-focus image. The size of bubbles is deduced from analysis of interference fringes. The characteristics of irregular sand particles are obtained from analysis of their speckle-like pattern. Experiments are confirmed by simulations.

  7. A numerical study of the particle size distribution of an aerosol undergoing turbulent coagulation

    NASA Astrophysics Data System (ADS)

    Reade, Walter C.; Collins, Lance R.

    2000-07-01

    Coagulation and growth of aerosol particles subject to isotropic turbulence has been explored using direct numerical simulations. The computations follow the trajectories of 262 144 initial particles as they are convected by the turbulent flow field. Collision between two parent particles leads to the formation of a new daughter particle with the mass and momentum (but not necessarily the energy) of the parent particles. The initially monodisperse population of particles will develop a size distribution over time that is controlled by the collision dynamics. In an earlier study, Sundaram & Collins (1997) showed that collision rates in isotropic turbulence are controlled by two statistics: (i) the radial distribution of the particles and (ii) the relative velocity probability density function. Their study considered particles that rebound elastically; however, we find that the formula that they derived is equally valid in a coagulating system. However, coagulation alters the numerical values of these statistics from the values they attain for the elastic rebound case. This difference is substantial and must be taken into consideration to properly predict the evolution of the size distribution of a population of particles. The DNS results also show surprising trends in the relative breadth of the particle size distribution. First, in all cases, the standard deviation of the particle size distribution of particles with finite Stokes numbers is much larger than the standard deviation for either the zero-Stokes-number or infinite-Stokes-number limits. Secondly, for particles with small initial Stokes numbers, the standard deviation of the final particle size distribution decreases with increasing initial particle size; however, the opposite trend is observed for particles with slightly larger initial Stokes numbers. An explanation for these phenomena can be found by carefully examining the functional dependence of the radial distribution function on the particle size

  8. The effect of particle size and porosity on spectral contrast in the mid-infrared

    USGS Publications Warehouse

    Salisbury, J.W.; Eastes, J.W.

    1985-01-01

    Contrary to previous work, we find that the decreasing intensity of fundamental molecular vibration bands with decreasing particle size is due primarily to increasing porosity of the finer particle size ranges, rather than to particle size per se. This implies that laser reflectance measurements from orbiting spacecraft should avoid loss of spectral contrast for fine particulate surfaces, because such measurements near zero phase angle will benefit from the opposition effect. ?? 1985.

  9. Anomalous change of Airy disk with changing size of spherical particles

    NASA Astrophysics Data System (ADS)

    Pan, Linchao; Zhang, Fugen; Meng, Rui; Xu, Jie; Zuo, Chenze; Ge, Baozhen

    2016-02-01

    Use of laser diffraction is considered as a method of reliable principle and mature technique in measurements of particle size distributions. It is generally accepted that for a certain relative refractive index, the size of the scattering pattern (also called Airy disk) of spherical particles monotonically decreases with increasing particle size. This fine structure forms the foundation of the laser diffraction method. Here we show that the Airy disk size of non-absorbing spherical particles becomes larger with increasing particle size in certain size ranges. To learn more about this anomalous change of Airy disk (ACAD), we present images of Airy disk and curves of Airy disk size versus particle size for spherical particles of different relative refractive indices by using Mie theory. These figures reveal that ACAD occurs periodically for non-absorbing particles and will disappear when the absorbing efficiency is higher than certain value. Then by using geometrical optics (GO) approximation, we derive the analytical formulae for the bounds of the size ranges where ACAD occurs. From the formulae, we obtain laws of ACAD as follows: (1) for non-absorbing particles, ACAD occurs periodically, and when the particle size tends to infinity, the period tends to a certain value. As the relative refractive index increases, (2) the particle size ranges where ACAD occurs shift to smaller values, (3) the period of ACAD becomes smaller, and (4) the width of the size ranges where ACAD occurs becomes narrower. In addition, we can predict from the formulae that ACAD also exists for particles whose relative refractive index is smaller than 1.

  10. Predicting the film and lens water volume between soil particles using particle size distribution data

    NASA Astrophysics Data System (ADS)

    Mohammadi, M. H.; Meskini-Vishkaee, F.

    2012-12-01

    SummaryWe develop four conceptual approaches to quantify the volume of water lenses between soil particles (ɛi) and adsorbed water films (δi) coating soil particles based on soil Particle Size Distribution (PSD) data. Method 1 is based on expression of the ɛi as matric suction independent pendular rings and method 2 is based on expression of the ɛi as function of matric suction. Methods 3 and 4 are based on the coupling of δi estimated with van der Waals and electrostatic forces, with ɛi estimated with methods 1 and 2 respectively. We show that the filling angle of the lens water is independent of surface tension but increases with the porosity. The four methods are applied to predict effects of ɛi and δi on Soil Moisture Characteristics (SMC) in eighty soil samples selected from UNSODA database. The total component of the ɛi in soil water content ranged from 0.0111 (L3 L-3) to 0.1604 (L3 L-3), with the average of 0.0703 (L3 L-3) for method 1 and from 0.0082 (L3 L-3) to 0.0523 (L3 L-3), with the average of 0.0237 (L3 L-3) for method 2. The component of δi is less than 0.0121 of each pore water content. Results showed that for methods 1 and 2, the component of the ɛi in the soil water content was partially relevant for the prediction of SMC, especially in dry range. Moreover, the accuracy of the method 1 was slightly greater than that of the method 2. We attribute the methods error to the roughness of soil particles, high surface energy content of clay particles and, to the simplified pore geometric concepts that does not effectively reflect the pore geometry. We conclude that the main advantage of the present approaches is developing two different methods for estimation of the volume of the lens water by using only the PSD data and bulk density which are measured easily.

  11. Coarsening Behavior of the (Ti, Nb)(C, N) Complex Particle in a Microalloyed Steel Weld Heat-Affected Zone Considering the Critical Particle Size

    NASA Astrophysics Data System (ADS)

    Moon, Joonoh; Kim, Sanghoon; Lee, Jongbong; Lee, Changhee

    2007-11-01

    Our recent report revealed the effect of critical particle size on the particle coarsening behavior of the TiN particle. In the present work, the equation for critical particle size is extended by considering the change of particle volume fraction during the continuous thermal cycle. By considering the concept of modified critical particle size, coarsening of the (Ti, Nb)(C, N) complex particle is calculated, and the calculated results are in good agreement with experimental data.

  12. Deconvolution of the particle size distribution of ProRoot MTA and MTA Angelus.

    PubMed

    Ha, William Nguyen; Shakibaie, Fardad; Kahler, Bill; Walsh, Laurence James

    2016-01-01

    Objective Mineral trioxide aggregate (MTA) cements contain two types of particles, namely Portland cement (PC) (nominally 80% w/w) and bismuth oxide (BO) (20%). This study aims to determine the particle size distribution (PSD) of PC and BO found in MTA. Materials and methods The PSDs of ProRoot MTA (MTA-P) and MTA Angelus (MTA-A) powder were determined using laser diffraction, and compared to samples of PC (at three different particle sizes) and BO. The non-linear least squares method was used to deconvolute the PSDs into the constituents. MTA-P and MTA-A powders were also assessed with scanning electron microscopy. Results BO showed a near Gaussian distribution for particle size, with a mode distribution peak at 10.48 μm. PC samples milled to differing degrees of fineness had mode distribution peaks from 19.31 down to 4.88 μm. MTA-P had a complex PSD composed of both fine and large PC particles, with BO at an intermediate size, whereas MTA-A had only small BO particles and large PC particles. Conclusions The PSD of MTA cement products is bimodal or more complex, which has implications for understanding how particle size influences the overall properties of the material. Smaller particles may be reactive PC or unreactive radiopaque agent. Manufacturers should disclose particle size information for PC and radiopaque agents to prevent simplistic conclusions being drawn from statements of average particle size for MTA materials.

  13. Method for preparing spherical thermoplastic particles of uniform size

    DOEpatents

    Day, J.R.

    1975-11-17

    Spherical particles of thermoplastic material of virtually uniform roundness and diameter are prepared by cutting monofilaments of a selected diameter into rod-like segments of a selected uniform length which are then heated in a viscous liquid to effect the formation of the spherical particles.

  14. Effect of Particle Size Distribution on Slurry Rheology: Nuclear Waste Simulant Slurries

    SciTech Connect

    Chun, Jaehun; Oh, Takkeun; Luna, Maria L.; Schweiger, Michael J.

    2011-07-05

    Controlling the rheological properties of slurries has been of great interest in various industries such as cosmetics, ceramic processing, and nuclear waste treatment. Many physicochemical parameters, such as particle size, pH, ionic strength, and mass/volume fraction of particles, can influence the rheological properties of slurry. Among such parameters, the particle size distribution of slurry would be especially important for nuclear waste treatment because most nuclear waste slurries show a broad particle size distribution. We studied the rheological properties of several different low activity waste nuclear simulant slurries having different particle size distributions under high salt and high pH conditions. Using rheological and particle size analysis, it was found that the percentage of colloid-sized particles in slurry appears to be a key factor for rheological characteristics and the efficiency of rheological modifiers. This behavior was shown to be coupled with an existing electrostatic interaction between particles under a low salt concentration. Our study suggests that one may need to implement the particle size distribution as a critical factor to understand and control rheological properties in nuclear waste treatment plants, such as the U.S. Department of Energy’s Hanford and Savannah River sites, because the particle size distributions significantly vary over different types of nuclear waste slurries.

  15. Particle size selection in post-spark dusty plasma in non-uniform electric field

    NASA Astrophysics Data System (ADS)

    Kim, Woongsik; Pikhitsa, Peter V.; Choi, Mansoo

    2016-11-01

    We report a strong size-selective effect of the non-uniform external electric field on unitary charged nanoparticles in a residual dusty plasma generated by spark discharge. It has been found that the field influences the outcome particle size distribution function considerably by expelling smaller particles out of the residual plasma cloud so that they cannot neutralize or agglomerate. Meantime, larger particles being dragged by the plasma cloud neutralize and disappear at walls; therefore, the particle size distribution function shifts to small sizes. We give a simple theory explaining the field effect and suggest its application for a patterning technique.

  16. Particle sizing by measurement of forward-scattered light at two angles

    NASA Technical Reports Server (NTRS)

    Buchele, D. R.

    1983-01-01

    Fundamental and practical limitations to particle sizing by measurement of forward scattered light are presented. Methods to minimize the limitations are described. Two types of instruments are compared.

  17. Characterization of particle size distribution from diesel engines fueled with palm-biodiesel blends and paraffinic fuel blends

    NASA Astrophysics Data System (ADS)

    Lin, Yuan-Chung; Lee, Chia-Fon; Fang, Tiegang

    Biodiesels are promoted as alternative fuels and their applications in diesel engines have been investigated by many researchers. However, the particle size distribution emitted from heavy-duty diesel engines fueled with palm-biodiesel blended with premium diesel fuel and paraffinic fuel blended with palm-biodiesel has seldom been addressed. Thus, five test fuels were used in this work to study the particle size distribution: D100 (premium diesel fuel), B100 (100% palm-biodiesel), B20 (20 vol% palm-biodiesel+80 vol% D100), BP9505 (95 vol% paraffinic fuel+5 vol% palm-biodiesel) and BP8020 (80 vol% paraffinic fuel+20 vol% palm-biodiesel). A Micro-Orifice Uniform Deposit Impactor (MOUDI) equipped with aluminum filters was used to collect size-resolved samples. Experimental results indicated that palm-biodiesel blends and paraffinic fuel blends could improve combustion efficiency in diesel engines, but pure palm-biodiesel could cause incomplete combustion. Adding palm-biodiesel to diesel fuel would slightly increase particles with diameter <0.31 μm but paraffinic fuel blends could decrease particles with diameter <1 μm. The mass median diameter of overall particles (MMD o) and σg,o are 0.439 μm and 3.88 for D100; 0.380 μm and 3.24 for B20; 0.465 μm and 4.22 for B100; 1.40 μm and 4.92 for BP9505; 1.46 μm and 2.25 for BP8020. There are more particles with low aerodynamic diameters (diameter <0.31 μm) in the exhaust of D100, B20 and B100 fuels. On the other hand, a greater fraction of particulate matter of BP9505 and BP8020 existed in coarse particles (diameter: 2.5-10 μm). Energy efficiency also increases significantly by 12.3-15.1% with the introduction of paraffinic fuel blends into the engine. Nevertheless, paraffinic fuel blends also reduce the emission of particulate matters by 36.0-38.4%. Carbon monoxide was decreased by 36.8-48.5%. Total hydrocarbon is 39.6-41.7% less than diesel fuel combustion. Nitrogen oxides emission is about 5% lower for paraffinic

  18. Flow chamber analysis of size effects in the adhesion of spherical particles

    PubMed Central

    Decuzzi, P; Gentile, F; Granaldi, A; Curcio, A; Causa, F; Indolfi, C; Netti, P; Ferrari, M

    2007-01-01

    The non-specific adhesion of spherical micro- and nano-particles to a cell substrate is investigated in a parallel plate flow chamber. Differently from prior in-vitro analyses, the total volume of the particles injected into the flow chamber is kept fixed whilst the particle diameter is changed in the range 0.5–10 μm. It is shown that: (i) the absolute number of particles adherent to the cell layer per unit surface decreases with the size of the particle as d−1.7; (ii) the volume of the particles adherent per unit surface increases with the size of the particles as d+1.3. From these results and considering solely non-specific particles, the following hypothesis are generated (i) use the smallest possible particles in biomedical imaging and (ii) use the largest possible particles in drug delivery. PMID:18203435

  19. Measuring the mass, density, and size of particles and cells using a suspended microchannel resonator

    NASA Astrophysics Data System (ADS)

    Godin, Michel; Bryan, Andrea K.; Burg, Thomas P.; Babcock, Ken; Manalis, Scott R.

    2007-09-01

    We demonstrate the measurement of mass, density, and size of cells and nanoparticles using suspended microchannel resonators. The masses of individual particles are quantified as transient frequency shifts, while the particles transit a microfluidic channel embedded in the resonating cantilever. Mass histograms resulting from these data reveal the distribution of a population of heterogeneously sized particles. Particle density is inferred from measurements made in different carrier fluids since the frequency shift for a particle is proportional to the mass difference relative to the displaced solution. We have characterized the density of polystyrene particles, Escherichia coli, and human red blood cells with a resolution down to 10-4g/cm3.

  20. Chemical characterization, nano-particle mineralogy and particle size distribution of basalt dust wastes.

    PubMed

    Dalmora, Adilson C; Ramos, Claudete G; Oliveira, Marcos L S; Teixeira, Elba C; Kautzmann, Rubens M; Taffarel, Silvio R; de Brum, Irineu A S; Silva, Luis F O

    2016-01-01

    Understanding the geochemistry of basalt alteration is central to the study of agriculture systems. Various nano-minerals play an important role in the mobilization of contaminants and their subsequent uptake by plants. We present a new analytical experimental approach in combination with an integrated analytical protocol designed to study basalt alteration processes. Recently, throughout the world, ultra-fine and nano-particles derived from basalt dust wastes (BDW) during "stonemeal" soil fertilizer application have been of great concern for their possible adverse effects on human health and environmental pollution. Samples of BDW utilized were obtained from companies in the Nova Prata mining district in southern Brazil for chemical characterization and nano-mineralogy investigation, using an integrated application of advanced characterization techniques such as X-ray diffraction (XRD), High Resolution-Transmission Electron microscopy (HR-TEM)/Energy Dispersive Spectroscopy (EDS)/(selected-area diffraction pattern) SAED, Field Emission-Scanning Electron Microscopy (FE-SEM/EDS), and granulometric distribution analysis. The investigation has revealed that BDW materials are dominated by SiO2, Al2O3, and Fe2O3, with a complex micromineralogy including alkali feldspar, augite, barite, labradorite, hematite, heulandrite, gypsum, kaolinite, quartz, and smectite. In addition, we have identified a number of trace metals such as Cd, Cu, Cr, and Zn, that are preferentially concentrated into the finer, inhalable, dust fraction and, thus, could present a health hazard in the urban areas around the basalt mining zone. The implication of this observation is that use of these nanometric-sized particulates as soil fertilizer may present different health challenges to those of conventional fertilizers, inviting future work regarding the relative toxicities of these materials. Our investigation on the particle size distribution, nano-particle mineralogy and chemical composition in

  1. Mathematical model parameters for describing the particle size spectra of knife-milled corn stover

    SciTech Connect

    Bitra, V.S.P; Womac, A.R.; Yang, Y.T.; Miu, P.I.; Igathanathane, C.

    2009-09-01

    Particle size distributions of Corn stover (Zea mays L.) created by a knife mill were determined using integral classifying screens with sizes from 12.7 to 50.8 mm, operating at speeds from 250 to 500 rpm, and mass input rates ranging from 1 to 9 kg min_1. Particle distributions were classified using American Society of Agricultural and Biological Engineers (ASABE) standardised sieves for forage analysis that incorporated a horizontal sieving motion. The sieves were made from machined-aluminium with their thickness proportional to the sieve opening dimensions. A wide range of analytical descriptors that could be used to mathematically represent the range of particle sizes in the distributions were examined. The correlation coefficients between geometric mean length and screen size, feed rate, and speed were 0.980, 0.612, and _0.027, respectively. Screen size and feed rate directly influenced particle size, whereas operating speed had a weak indirect relation with particle size. The Rosin Rammler equation fitted the chopped corn stover size distribution data with coefficient of determination (R2) > 0.978. This indicated that particle size distribution of corn stover was well-fit by the Rosin Rammler function. This can be attributed to the fact that Rosin Rammler expression was well suited to the skewed distribution of particle sizes. Skewed distributions occurred when significant quantities of particles, either finer or coarser, existed or were removed from region of the predominant size. The mass relative span was slightly greater than 1, which indicated that it was a borderline narrow to wide distribution of particle sizes. The uniformity coefficient was <4.0 for 19.0 50.8 mm screens, which indicated particles of relatively uniform size. Knife mill chopping of corn stover produced fine-skewed mesokurtic particles with 12.7 50.8 mm screens. Size-related parameters, namely, geometric mean length, Rosin Rammler size parameter, median length, effective length, and

  2. Inert particles size distribution influence on heterogeneous detonation suppression

    NASA Astrophysics Data System (ADS)

    Kratova, Yu. V.; Fedorov, A. V.

    2016-10-01

    Interaction of a detonation wave propagating in the cellular detonation mode with a cloud of non-reactive particles is numerically studied. It is demonstrated that the presence of inert particles alters the detonation wave structure and its velocity. The influence of various parameters of the non-reactive cloud is investigated. The critical length of the cloud sufficient for detonation suppression is determined. It is shown that the disperse composition and the non-uniform distribution of particles in the cloud are important parameters affecting the detonation propagation mode.

  3. Determination of the mineral distribution in pulverized coal using densitometry and laser particle sizing

    SciTech Connect

    Hong Zhang; Yan-xue Mo; Ming Sun; Xian-yong Wei

    2005-12-01

    Coal particle size and mineral matter content have important effects on coal combustion. The mineral content of five Chinese coals was determined by a method combining densitometry and particle-size analysis. The finer particles of pulverized samples were found to contain more mineral content. Rank also had a significant influence on the particle-size ash-content distribution of pulverized coal particles. The sharpest size-ash distribution was found in pulverized anthracite samples; a broader distribution was found with bituminous coal samples, while a uniform distribution was observed in pulverized lignite samples. Ash in higher ash anthracite or lower ash bituminous coal is more evenly distributed. It is a combined effect of size distribution, yield, and proximate analysis of their density separation fractions. Mineral matter tends to distribute more evenly in finer pulverized coals. This results from a relative increase of the low-density fraction in the finer particles. 13 refs., 10 figs., 10 tabs.

  4. Effect of particle size on fracture toughness of SiC/Al composite material

    NASA Technical Reports Server (NTRS)

    Flom, Y.; Arsenault, R. J.

    1989-01-01

    Discontinuous SiC/Al composites with SiC particles of different sizes were fabricated in order to study the role of particle size on the fracture process. The fracture process is confined to a very narrow band and takes place within the matrix in composites containing small SiC particle sizes. In the composite reinforced with SiC particles of 20 microns and above fracture of SiC begins to dominate. The matrix is influenced by the high density of dislocations generated at SiC/Al interfaces due to the difference in coefficient of thermal expansion between SiC and the Al matrix. Crack initiation fracture toughness does not depend on SiC particle size. Crack growth fracture toughness increases as the size of the SiC particle increase.

  5. Size-selective separation of submicron particles in suspensions with ultrasonic atomization.

    PubMed

    Nii, Susumu; Oka, Naoyoshi

    2014-11-01

    Aqueous suspensions containing silica or polystyrene latex were ultrasonically atomized for separating particles of a specific size. With the help of a fog involving fine liquid droplets with a narrow size distribution, submicron particles in a limited size-range were successfully separated from suspensions. Performance of the separation was characterized by analyzing the size and the concentration of collected particles with a high resolution method. Irradiation of 2.4MHz ultrasound to sample suspensions allowed the separation of particles of specific size from 90 to 320nm without regarding the type of material. Addition of a small amount of nonionic surfactant, PONPE20 to SiO2 suspensions enhanced the collection of finer particles, and achieved a remarkable increase in the number of collected particles. Degassing of the sample suspension resulted in eliminating the separation performance. Dissolved air in suspensions plays an important role in this separation.

  6. Particle size effect for metal pollution analysis of atmospherically deposited dust

    NASA Astrophysics Data System (ADS)

    Al-Rajhi, M. A.; Al-Shayeb, S. M.; Seaward, M. R. D.; Edwards, H. G. M.

    The metallic compositions of 231 atmospherically deposited dust samples obtained from widely-differing environments in Riyadh city, Saudi Arabia, have been investigated in relation to the particle size distributions. Sample data are presented which show that particle size classification is very important when analysing dust samples for atmospheric metal pollution studies. By cross-correlation and comparison, it was found that the best way to express the results of the metal concentration trend was as an average of particle ratios. Correlations between the six metals studied, namely Pb, Cr, Ni, Cu, Zn and Li, were found for every particle size (eight categories) and reveal that the metal concentrations increased as the particle size decreased. On the basis of this work, it is strongly recommended that future international standards for metal pollutants in atmospherically deposited dusts should be based on particle size fractions.

  7. Dense medium radiative transfer theory for two scattering layers with a Rayleigh distribution of particle sizes

    SciTech Connect

    West, R.; Tsang, Leung; Winebrenner, D.P. )

    1993-03-01

    Dense medium radiative transfer theory is applied to a three-layer model consisting of two scattering layers overlying a homogeneous half space with a size distribution of particles in each layer. A model with a distribution of sizes gives quite different results than those obtained from a model with a single size. The size distribution is especially important in the low frequency limit when scattering is strongly dependent on particle size. The size distribution and absorption characteristics also affect the extinction behavior as a function of fractional volume. Theoretical results are also compared with experimental data. The sizes, permittivities, and densities used in the numerical illustrations are typical values for snow.

  8. A review: Different methods producing different particles size and distribution in synthesis of calcium carbonate nano particles

    NASA Astrophysics Data System (ADS)

    Sulimai, N. H.; Rusop, M.; Alrokayan, Salman A. H.; Khan, Haseeb A.

    2016-07-01

    Carbonates exist as 73 percent of world crust carbon. Abundance and bioavailability of Calcium Carbonates offer reliable resources, costs saving and environmental friendly potentials in its applications. Studies proven nano-sized Calcium Cabonate (nCC) employs a more significant characteristics compared to larger sizes. Properties of nCC is affected by the dispersion of the particles in which agglomeration occurs. It is important to gain more understanding of the conditions contributing or stunting the agglomeration to gain more control of the particles morphology and dynamic. A few recent studies with different methods to prepare calcium carbonate nanoparticles were listed in Table 1 .Particle size and dispersity of calcium carbonate are affected by different conditions of its preparation. Other factors such as mechanical aggression, concentration of solution, temperature of precipitation, pH of reaction are all contributing factors towards particle sizes and distribution.

  9. Morphologically and size uniform monodisperse particles and their shape-directed self-assembly

    DOEpatents

    Collins, Joshua E.; Bell, Howard Y.; Ye, Xingchen; Murray, Christopher Bruce

    2015-11-17

    Monodisperse particles having: a single pure crystalline phase of a rare earth-containing lattice, a uniform three-dimensional size, and a uniform polyhedral morphology are disclosed. Due to their uniform size and shape, the monodisperse particles self assemble into superlattices. The particles may be luminescent particles such as down-converting phosphor particles and up-converting phosphors. The monodisperse particles of the invention have a rare earth-containing lattice which in one embodiment may be an yttrium-containing lattice or in another may be a lanthanide-containing lattice. The monodisperse particles may have different optical properties based on their composition, their size, and/or their morphology (or shape). Also disclosed is a combination of at least two types of monodisperse particles, where each type is a plurality of monodisperse particles having a single pure crystalline phase of a rare earth-containing lattice, a uniform three-dimensional size, and a uniform polyhedral morphology; and where the types of monodisperse particles differ from one another by composition, by size, or by morphology. In a preferred embodiment, the types of monodisperse particles have the same composition but different morphologies. Methods of making and methods of using the monodisperse particles are disclosed.

  10. Methods for Determining Particle Size Distributions from Nuclear Detonations.

    DTIC Science & Technology

    1987-03-01

    contains the following components (See Fig. 1): laser source, 2) sample cell, 3) Photomultiplier tube (PMT), and 4) autocor- relator. In PCS, light ...from the laser source is scattered from particles that are suspended in a clear liquid. This scattered light is then detected by the photomultiplier...and laser light observed at time t and t + v For particles that are monodisperse the autocorrelation function becomes (5:2): C( 1 ) ( )(1>[+be ms F

  11. [Size distributions of organic carbon (OC) and elemental carbon (EC) in Shanghai atmospheric particles].

    PubMed

    Wang, Guang-Hua; Wei, Nan-Nan; Liu, Wei; Lin, Jun; Fan, Xue-Bo; Yao, Jian; Geng, Yan-Hong; Li, Yu-Lan; Li, Yan

    2010-09-01

    Size distributions of organic carbon (OC), elemental carbon (EC) and secondary organic carbon (SOC) in atmospheric particles with size range from < 0.49, 0.49-0.95, 0.95-1.50, 1.50-3.00, 3.00-7.20, > 7.20 microm, collected in Jiading District, Shanghai were determined. For estimating size distribution of SOC in these atmospheric particles, a method of determining (OC/EC)(pri) in atmospheric particles with different sizes was discussed and developed, with which SOC was estimated. According to the correlation between OC and EC, main sources of the particles were also estimated roughly. The size distributions of OC and SOC showed a bi-modal with peaks in the particles with size of < 0.49 microm and > 3.0 microm, respectively. EC showed both of a bi-modal and tri-modal. Compared with OC, EC was preferably enriched in particles with size of < 0.49 microm. Mass concentrations of OC and EC in fine particles (< 3.00 microm) accounted for 59.8%-80.0% and 58.1%-82.4% of those in total suspended particles. OC and EC were preferably enriched in fine particles (< 3.00 microm). The concentrations of SOC in the particles with different sizes accounted for 15.7%-79.1% of OC in the particles with corresponding size. Concentrations of SOC in fine aerosols (< 3.00 microm) and coarse aerosols (> 3.00 microm) accounted for 41.4% and 43.5% of corresponding OC. Size distributions of OC, EC and SOC showed time-dependence. The correlation between OC and EC showed that the main contribution to atmospheric particles in Jiading District derived from light petrol vehicles exhaust.

  12. Particle motion in a periodic driving flow. The role of added mass force and the finite size of particles

    NASA Astrophysics Data System (ADS)

    Ruiz Chavarria, Gerardo; Lopez Sanchez, Erick Javier

    2016-11-01

    The motion of particles in a fluid is an open problem. The main difficulty arises from the fact that hydrodynamical forces acting on a particle depend on the flow properties. In addition, the form and the size of particles must be taken into account. In this work we present numerical results of the particle transport in a periodic driving flow in a channel flushing into an open domain. To study the transport of particles we solve the equation of motion for a spherical particle in which we include the drag, the gravity, the buoyancy, the added mass and the history force. Additionally we include the corrections for a particle of finite size. For solving this equation a knowledge of the velocity field is required. To obtain the velocity field we solve the Navier Stokes and the continuity equations with a finite volume method. In the flow under study a vorticity dipole and a spanwise vortex are present, both have an important influence on the motion of particles. The dipole enhances displacement of particles because flow between vortices behaves like a jet and the spanwise vortex produces the lifting and deposition of particles from/to the bottom. We observe clustering of particles both into the channel and in the open domain as observed in coastal systems. The authors acknowledge DGAPA-UNAM by support under project PAPIIT IN115315 "Ondas y estructuras coherentes en dinámica de fluidos".

  13. To chew or not to chew: fecal particle size in herbivorous reptiles and mammals.

    PubMed

    Fritz, Julia; Hummel, Jürgen; Kienzle, Ellen; Streich, W Jürgen; Clauss, Marcus

    2010-11-01

    A major difference between reptile and mammalian herbivores is that the former do not masticate their food. Actually, food particle size reduction by chewing is usually considered one of the adaptations facilitating the higher metabolic rates of mammals. However, quantitative comparisons of ingesta particle size between the clades have, to our knowledge, not been performed so far. We measured mean fecal particle size (MPS) in 79 captive individuals of 14 reptile herbivore species (tortoises, lizards, and Corucia zebrata) by wet sieving and compared the results with a mammalian dataset. MPS increased with body mass in both clades, but at a significantly higher level in reptiles. Limited evidence in free-ranging and captive individuals of Testudo hermanni indicates that in reptiles, the ability to crop food and food particle size significantly influence fecal particle size. The opportunistic observation of a drastic particle size difference between stomach and intestinal contents corroborates findings that in reptiles, in contrast to terrestrial mammals, significant ingesta particle size reduction does occur in the gastrointestinal tract, most likely owing to microbial action during very long ingesta retention. Whether behavioral adaptations to controlling ingesta particle size, such as deliberate small bite sizes, are adaptive strategies in reptiles remains to be investigated.

  14. SPECIATION OF GAS-PHASE AND FINE PARTICLE EMISSIONS FROM BURNING OF FOLIAR FUELS

    EPA Science Inventory

    Particle size distributions (10-1000 nm aerodynamic diameter), physical and chemical properties of fine particle matter (PM2.5) with aerodynamic diameter <2.5 micrometers, and gas-phase emissions from controlled open burning of assorted taxa were measured. Chemical speciation of ...

  15. A "TEST OF CONCEPT" COMPARISON OF AERODYNAMIC AND MECHANICAL RESUSPENSION MECHANISMS FOR PARTICLES DEPOSITED ON FIELD RYE GRASS (SECALE CERCELE). PART I. RELATIVE PARTICLE FLUX RATES

    EPA Science Inventory

    Resuspension of uniform latex micro spheres deposited on a single seed pod of field rye grass stalk and head was investigated experimentally in a wind tunnel. The experiment was designed to distinguish aerodynamic (viscous and turbulent) mechanisms from mechanical resuspension re...

  16. Small scale variations of the atmosphere and their implications for the size of noctilucent cloud particles

    NASA Astrophysics Data System (ADS)

    Baumgarten, Gerd; Fiedler, Jens; Lübken, Franz-Josef; Ridder, Christine

    2016-04-01

    Noctilucent clouds (NLC) in the summer mesopause region (about 83 km altitude) are well known since more than 130 years. They are primarily made of ice particles of a few tens of nanometers and thus much smaller than the wavelength of visible light. Nevertheless, lidar measurements allow calculating particle size and inferring particle shape when combined with optical and microphysical modeling of non-spherical ice particles. We use the ALOMAR RMR-lidar, located in Northern Norway at 69°N, that is able to measure NLC with sub-second resolution. The signal levels at three widely separated wavelengths from 335 nm to 1064 nm allow deriving particle sizes with a temporal resolution of two minutes. We will use lidar observations between 2008 and 2014 to investigate the shape of the size distribution. The fundamental question of the shape of the size distribution is a link to the microphysics but also to atmospheric variability by turbulence and waves. Due to large sounding volumes (compared to the lidar sounding volume) this shape of the size distribution is of essential importance for most optical remote sensing methods that depend on assumptions about the width of the size distribution when retrieving mean particle sizes. The actual shape of the size distribution is of essential importance for most optical remote sensing methods (which have larger sounding volumes than the lidar) that depend on assumptions about the width of the size distribution when retrieving mean particle sizes.

  17. Metal uptake by corn grown on media treated with particle-size fractionated biosolids.

    PubMed

    Chen, Weiping; Chang, Andrew C; Wu, Laosheng; Zhang, Yongsong

    2008-03-15

    Particle-size of biosolids may affect plant uptake of heavy metals when the biosolids are land applied. In this study, corn (Zea mays L.) was grown on sand media treated with biosolids to study how particle-size of biosolids affected the plant uptake of cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn). Two biosolids, the Nu-Earth biosolids and the Los Angeles biosolids, of dissimilar surface morphology were utilized. The former exhibited a porous and spongy structure and had considerably greater specific surface area than that of the latter, which was granular and blocky. The specific surface area of the Los Angeles biosolids was inversely proportional to its particle-size, while that of Nu-Earth biosolids did not change significantly with particle-size. For each biosolid, the metal concentrations were not affected by particle sizes. The biomass yields of plants grown on the treated media increased as the biosolid particle-size decreased, indicating that plant uptake of nutrients from biosolids was dependent on interactions at the root-biosolids interface. The effect of particle-size on a metal's availability to plants was element-specific. The uptake rate of Cd, Zn, Cu, and Ni was correlated with the surface area of the particles, i.e., smaller particles having higher specific area provided greater root-biosolids contact and resulted in enhanced uptake of Cd and Zn and slightly less increased uptake of Cu and Ni. The particle morphology of biosolids had limited influence on the plant tissue concentrations of Cr and Pb. For both types of biosolids, total metal uptake increased as biosolid particle-size decreased. Our research indicates that biosolid particle-size distribution plays a deciding role in plant uptake of heavy metals when they are land applied.

  18. A new apparatus for real-time assessment of the particle size distribution of disintegrating tablets.

    PubMed

    Quodbach, Julian; Kleinebudde, Peter

    2014-11-01

    The aim of this study is the introduction of a novel apparatus that is capable of continuously measuring the particle size reduction of disintegrating tablets and analysis of the obtained results. The apparatus is constructed such that no particles pass directly through the pumping system. Thereby, the overall energy input into the particle suspension is reduced, and continuous measurement is possible without rapid destruction of the generated particles. The detected particle sizes at the beginning and at the end of the measurement differ greatly, depending on the applied disintegrant. The median particle sizes at the end of the measurement vary between 621.5 and 178.0 μm for different disintegrants. It is demonstrated that the particle size reduction follows an exponential function and that the fit parameters can be used to describe the disintegration behavior. A strong correlation between the median particle size of crospovidone disintegrants and generated particle size of the tablets is observed. This could be due to a more homogeneous distribution of the disintegrant particles in the tablets. Similar trends are observed for sodium starch glycolate and croscarmellose sodium. The new apparatus provides an innovative method to describe disintegrant effectiveness and efficiency.

  19. Preparation of 1,3,5-triamo-2,4,6-trinitrobenzene of submicron particle size

    DOEpatents

    Rigdon, Lester P.; Moody, Gordon L.; McGuire, Raymond R.

    2001-05-01

    A method is disclosed for the preparation of very small particle size, relatively pure 1,3,5-triamino-2,4,6-trinitrobenzene (TATB). Particles of TATB prepared according to the disclosed method are of submicron size and have a surface area in the range from about 3.8 to 27 square meters per gram.

  20. COMPARISON OF TWO PARTICLE-SIZE SPECTROMETERS FOR AMBIENT AEROSOL MEASUREMENTS. (R827354C002)

    EPA Science Inventory

    There is an ongoing debate on the question which size fraction of particles in ambient air may be responsible for human health effects observed in epidemiological studies. Since there is no single instrument available for the measurement of the particle-size distribution over ...

  1. Wheat bran particle size influence on phytochemical extractability and antioxidant properties

    Technology Transfer Automated Retrieval System (TEKTRAN)

    It is unknown if particle size plays a role in extracting health promoting compounds in wheat bran because the extraction of antioxidant and phenolic compounds with particle size reduction has not been well documented. In this study, unmilled whole bran (coarse treatment) was compared to whole bran ...

  2. A query for effective mean particle size of dry and high moisture corns

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Eighteen dry and high moisture corns submitted to the University of Wisconsin Soil and Forage Analysis Laboratory (Marshfield, WI) for routine analysis were retained for mean particle size (MPS) and chemistry determinations. Mean particle size of corns was determined by the methods of the American S...

  3. Particle size distribution of hydrocyanic acid in gari, a cassava-based product.

    PubMed

    Maduagwu, E N; Fafunso, M

    1980-12-01

    A reciprocal relationship was observed between the cyanide content of gari and particle size. Hydrocyanic acid (HCN) content was positively correlated (r = 0.62) with sugar content but the correlation with starch content was poor (r = 0.33). From both the nutritional and toxicological standpoints, it would appear that larger particles size in gari is beneficial.

  4. Preparation of 1,3,5-triamino-2,4,6-trinitrobenzene of submicron particle size

    DOEpatents

    Rigdon, Lester P.; Moody, Gordon L.; McGuire, Raymond R.

    2001-01-01

    A method is disclosed for the preparation of very small particle size, relatively pure 1,3,5-triamino-2,4,6-trinitrobenzene (TATB). Particles of TATB prepared according to the disclosed method are of submicron size and have a surface area in the range from about 3.8 to 27 square meters per gram.

  5. Particle size determinants in the human immunodeficiency virus type 1 Gag protein.

    PubMed

    Garnier, L; Ratner, L; Rovinski, B; Cao, S X; Wills, J W

    1998-06-01

    The retroviral Gag protein plays the central role in the assembly process and can form membrane-enclosed, virus-like particles in the absence of any other viral products. These particles are similar to authentic virions in density and size. Three small domains of the human immunodeficiency virus type 1 (HIV-1) Gag protein have been previously identified as being important for budding. Regions that lie outside these domains can be deleted without any effect on particle release or density. However, the regions of Gag that control the size of HIV-1 particles are less well understood. In the case of Rous sarcoma virus (RSV), the size determinant maps to the CA (capsid) and adjacent spacer sequences within Gag, but systematic mapping of the HIV Gag protein has not been reported. To locate the size determinants of HIV-1, we analyzed a large collection of Gag mutants. To our surprise, all mutants with defects in the MA (matrix), CA, and the N-terminal part of NC (nucleocapsid) sequences produced dense particles of normal size, suggesting that oncoviruses (RSV) and lentiviruses (HIV-1) have different size-controlling elements. The most important region found to be critical for determining HIV-1 particle size is the p6 sequence. Particles lacking all or small parts of p6 were uniform in size distribution but very large as measured by rate zonal gradients. Further evidence for this novel function of p6 was obtained by placing this sequence at the C terminus of RSV CA mutants that produce heterogeneously sized particles. We found that the RSV-p6 chimeras produced normally sized particles. Thus, we present evidence that the entire p6 sequence plays a role in determining the size of a retroviral particle.

  6. Number size distribution of fine and ultrafine fume particles from various welding processes.

    PubMed

    Brand, Peter; Lenz, Klaus; Reisgen, Uwe; Kraus, Thomas

    2013-04-01

    Studies in the field of environmental epidemiology indicate that for the adverse effect of inhaled particles not only particle mass is crucial but also particle size is. Ultrafine particles with diameters below 100 nm are of special interest since these particles have high surface area to mass ratio and have properties which differ from those of larger particles. In this paper, particle size distributions of various welding and joining techniques were measured close to the welding process using a fast mobility particle sizer (FMPS). It turned out that welding processes with high mass emission rates (manual metal arc welding, metal active gas welding, metal inert gas welding, metal inert gas soldering, and laser welding) show mainly agglomerated particles with diameters above 100 nm and only few particles in the size range below 50 nm (10 to 15%). Welding processes with low mass emission rates (tungsten inert gas welding and resistance spot welding) emit predominantly ultrafine particles with diameters well below 100 nm. This finding can be explained by considerably faster agglomeration processes in welding processes with high mass emission rates. Although mass emission is low for tungsten inert gas welding and resistance spot welding, due to the low particle size of the fume, these processes cannot be labeled as toxicologically irrelevant and should be further investigated.

  7. A technique to measure the size of particles in laser Doppler velocimetry applications

    NASA Technical Reports Server (NTRS)

    Hess, C. F.

    1985-01-01

    A method to measure the size of particles in Laser Doppler Velocimeter (LDV) applications is discussed. Since in LDV the velocity of the flow is assocated with the velocity of particles to establish how well they follow the flow, in the present method the interferometric probe volume is surrounded by a larger beam of different polarization or wavelength. The particle size is then measured from the absolute intensity scattered from the large beam by particles crossing the fringes. Experiments using polystrene particles between 1.1 and 3.3 microns and larger glass beads are reported. It is shown that the method has an excellent size resolution and its accuracy is better than 10% for the particle size studied.

  8. Improved cholesterol phenotype analysis by a model relating lipoprotein life cycle processes to particle size[S

    PubMed Central

    van Schalkwijk, Daniël B.; de Graaf, Albert A.; van Ommen, Ben; van Bochove, Kees; Rensen, Patrick C. N.; Havekes, Louis M.; van de Pas, Niek C. A.; Hoefsloot, Huub C. J.; van der Greef, Jan; Freidig, Andreas P.

    2009-01-01

    Increased plasma cholesterol is a known risk factor for cardiovascular disease. Lipoprotein particles transport both cholesterol and triglycerides through the blood. It is thought that the size distribution of these particles codetermines cardiovascular disease risk. New types of measurements can determine the concentration of many lipoprotein size-classes but exactly how each small class relates to disease risk is difficult to clear up. Because relating physiological process status to disease risk seems promising, we propose investigating how lipoprotein production, lipolysis, and uptake processes depend on particle size. To do this, we introduced a novel model framework (Particle Profiler) and evaluated its feasibility. The framework was tested using existing stable isotope flux data. The model framework implementation we present here reproduced the flux data and derived lipoprotein size pattern changes that corresponded to measured changes. It also sensitively indicated changes in lipoprotein metabolism between patient groups that are biologically plausible. Finally, the model was able to reproduce the cholesterol and triglyceride phenotype of known genetic diseases like familial hypercholesterolemia and familial hyperchylomicronemia. In the future, Particle Profiler can be applied for analyzing detailed lipoprotein size profile data and deriving rates of various lipolysis and uptake processes if an independent production estimate is given. PMID:19515990

  9. Effects of surface charge, micro-bubble size and particle size on removal efficiency of electro-flotation.

    PubMed

    Han, M Y; Kim, M K; Ahn, H J

    2006-01-01

    Flotation is a water treatment alternative to sedimentation, and uses small bubbles to remove low-density particles from potable water and wastewater. The effect of zeta potential, bubble size and particle size on removal efficiency of the electro-flotation process was investigated because previous model-simulations indicated that these attributes are critical for high collision efficiency between micro-bubbles and particles. Solutions containing Al3+ as the metal ion were subjected to various conditions. The zeta potentials of bubbles and particles were similar under identical conditions, and their charges were influenced by metal ion concentration and pH. Maximum removal efficiency was 98 and 12% in the presence and absence of flocculation, respectively. Removal efficiency was higher when particle size was similar to bubble size. These results agree with modelling simulations and indicate that collision efficiency is greater when the zeta potential of one is negative and that of the other is positive and when their sizes are similar.

  10. Mixture state and size of Asian dust particles collected at southwestern Japan in spring 2000

    NASA Astrophysics Data System (ADS)

    Zhang, Daizhou; Iwasaka, Yasunobu; Shi, Guangyu; Zang, Jiaye; Matsuki, Atsushi; Trochkine, Dmitri

    2003-12-01

    Atmospheric particles were collected at Kumamoto (32°48'N, 130°45'E), a coastal city in southwestern Japan, during three dust storm events in spring 2000. The elemental composition and size of individual dust particles and their mixture state with sea salt, sulfate, and nitrate were analyzed using electron microscopes and an energy dispersive X-ray spectrometer. About 60 ˜ 85% of dust particles were internally mixed with sea salt. Weather records indicated these particles were most probably formed by the collisions and coagulations of dust particles and sea-salt particles. The relative weight ratios of mineral components to sea salt in individual particles showed that the mixtures of particles were dominated by mineral, by sea salt, or by both. Size distributions of the particles segregated by the mixture levels of mineral and sea salt in the three dust storm events were similar and all distributions showed a diameter range of 1 ˜ 8 μm with maximum mode around 3 μm. Out of 1 ˜ 8 μm, dust particles were rarely detected. The combination of dust particles with sea salt caused an increase in size of the dust particles. Therefore the decrease of particle concentrations in the range of diameter >3 μm suggests the critical diameter for dust particle dispersion was possibly around 3 μm and a dust particle might be removed rapidly if it became larger than this scale in the marine atmosphere. Detection of sulfate and nitrate revealed that 91% or more dust particles contained sulfate and 27% or less contained nitrate. The comparisons of the relative weight ratios of sodium, sulfur, and chlorine in mixture particles and in sea-salt particles confirmed previous results that mineral materials could enhance particulate sulfate and nitrate formation and restrain chlorine depletion from the sea-salt components in mixture particles.

  11. Particle size effect for cobalt Fischer-Tropsch catalysts based on in situ CO chemisorption

    NASA Astrophysics Data System (ADS)

    Yang, Jia; Frøseth, Vidar; Chen, De; Holmen, Anders

    2016-06-01

    The cobalt particle size effect on activity and selectivity for CO hydrogenation was revisited on cobalt catalysts supported on a large variety of supports at 483 K, 1.85 bar, and H2/CO/Ar = 15/1.5/33.5 Nml/min. The size dependence of the activity and selectivity was analyzed in terms of site coverage and rate constants based on SSITKA experimental results. It was found that the Co particle size index estimated by the conventional method, namely, ex situ hydrogen chemisorption, could not correlate well the activity and selectivity as a function of the particle size index. The same holds for the site coverage of CO and intermediates leading to methane formation. However, the cobalt particle size index based on in situ CO chemisorption measured at 373 K provides a good correlation for turnover frequencies (TOFs) at reaction conditions. It was observed that TOF for CO conversion (TOFCO) increased with increasing particle size index of cobalt and SSITKA experiments showed that this was possibly due to increased site coverage of CO. The TOF for methane formation (TOFCH4) increased with particle size and remained constant at higher particle sizes possibly due to combined effect from the site coverage of intermediates leading to methane (θCHx) and the pseudo-first-order rate constant (kt). The results suggest that the support can play an important role for the size dependence of the activity and selectivity of CO hydrogenation on Co catalysts.

  12. Particle size distribution and PM10 of volcanic ashes in Guadeloupe during the major eruption of Soufrière Hills in February 2010

    NASA Astrophysics Data System (ADS)

    Molinie, Jack; Bernard, Marie-Lise; Komorowski, Jean-Christophe; Euphrasie-Clotilde, Lovely; Brute, France-Nor; Roussas, Andre

    2014-05-01

    On the 11 February 2010, fifteen minutes after midday, an explosive eruption of Soufriere Hills volcano sent tephra over the neighbour Caribbean islands. The volcanic ashes benefit from the vertical wind distribution of the moment to reach Guadeloupe island and cover it ground near 5 hours after the ash venting. Since the first ashes arrival over the town of Pointe-a-Pitre (located at 80 km at the South East of Soufriere hills volcano) to the end of the event, we measured the mean particle concentrations and particle size distributions every twenty minutes. Measurements were performed at a building roof of the town using an optical particles counter Lighthouse IAQ 3016 mainly used in indoor air quality studies and which provides up to 6 particle size channels of simultaneous counting with aerodynamic diameters classes ranging from 0.3 to >10 µm. The airborne particulate matter mass concentration, with equivalent aerodynamic diameters less than 10 µm (PM10) were measured by the local air quality network Gwad'air, in the vicinity of the site used to study this ash fall.. The maximum concentration of small particles with diameter lesser than 1µm (D0.3-1) was observed one hour before the larger particles. This result may imply a difference in shape and density between particles D0.3-1 and particles D1-10 (1particle concentrations of particles D0.3-1+ D1-10. This result is probably related to the large variability in the density distribution of the particles. Moreover, we observed a variation over time in the shape and the composition of the collected volcanic ashes which impacts on the exposed population, especially their

  13. The effect of dispersoid particle size on the superplasticity of Al-Mg alloy

    SciTech Connect

    Chanda, T.; Ghosh, A.K.; Lavender, C.

    1995-12-31

    An Al-Mg alloy containing dispersoid forming elements such as Mn, Cr and Zr was thermomechanically processed with variations in processing history to produce nearly the same grain size ({approximately}6 {micro}m), but different distribution of size and density of intermetallic particles. Mechanical response of these materials were studied within the superplastic deformation regime in terms of stress-strain, stress-strain rate characteristics, cavitation and grain growth, and superplastic tensile elongation. In this work particles of approximately 500 nm size have been found to cause grain refinement after 90% rolling reduction contrary to previous findings of 2 {micro}m particles in an Al-0.45% Cu alloy. Particles with 200 to 500 nm size favorably influence superplastic elongation, but particle sizes in the range of 600 to 900 nm appear to have adverse effect in terms of superplastic flow properties, due to excessive cavitation.

  14. Determining size-specific emission factors for environmental tobacco smoke particles

    SciTech Connect

    Klepeis, Neil E.; Apte, Michael G.; Gundel, Lara A.; Sextro, Richard G.; Nazaroff, William W.

    2002-07-07

    Because size is a major controlling factor for indoor airborne particle behavior, human particle exposure assessments will benefit from improved knowledge of size-specific particle emissions. We report a method of inferring size-specific mass emission factors for indoor sources that makes use of an indoor aerosol dynamics model, measured particle concentration time series data, and an optimization routine. This approach provides--in addition to estimates of the emissions size distribution and integrated emission factors--estimates of deposition rate, an enhanced understanding of particle dynamics, and information about model performance. We applied the method to size-specific environmental tobacco smoke (ETS) particle concentrations measured every minute with an 8-channel optical particle counter (PMS-LASAIR; 0.1-2+ micrometer diameters) and every 10 or 30 min with a 34-channel differential mobility particle sizer (TSI-DMPS; 0.01-1+ micrometer diameters) after a single cigarette or cigar was machine-smoked inside a low air-exchange-rate 20 m{sup 3} chamber. The aerosol dynamics model provided good fits to observed concentrations when using optimized values of mass emission rate and deposition rate for each particle size range as input. Small discrepancies observed in the first 1-2 hours after smoking are likely due to the effect of particle evaporation, a process neglected by the model. Size-specific ETS particle emission factors were fit with log-normal distributions, yielding an average mass median diameter of 0.2 micrometers and an average geometric standard deviation of 2.3 with no systematic differences between cigars and cigarettes. The equivalent total particle emission rate, obtained integrating each size distribution, was 0.2-0.7 mg/min for cigars and 0.7-0.9 mg/min for cigarettes.

  15. Phase Separation of Binary Charged Particle Systems with Small Size Disparities using a Dusty Plasma.

    PubMed

    Killer, Carsten; Bockwoldt, Tim; Schütt, Stefan; Himpel, Michael; Melzer, André; Piel, Alexander

    2016-03-18

    The phase separation in binary mixtures of charged particles has been investigated in a dusty plasma under microgravity on parabolic flights. A method based on the use of fluorescent dust particles was developed that allows us to distinguish between particles of slightly different size. A clear trend towards phase separation even for smallest size (charge) disparities is observed. The diffusion flux is directly measured from the experiment and uphill diffusion coefficients have been determined.

  16. Particle Size Control for PIV Seeding Using Dry Ice

    DTIC Science & Technology

    2010-03-01

    in flight actually being carried out, the observations, drawings and notes of Leonardo da Vinci showed an analytical process to develop a way for...theoretical particle response: dvp dt = −C(vp − U) C = 18µ ρpd2p 86 87 Bibliography 1. Linscott, R. N. and Da Vinci , L., The Notebooks of Leonardo Da Vinci

  17. Design of a Particle Shadow-graph Velocimetry and Size (PSVS) System to Determine Particle Size and Density Distributions in Hanford Nuclear Tank Wastes - 12280

    SciTech Connect

    Fountain, M.S.; Blanchard, J.; Erikson, R.L.; Kurath, D.E.; Howe, D.T.; Adkins, H.; Jenks, J.

    2012-07-01

    Accurate particle size and density distributions for nuclear tank waste materials are essential information that helps determine the engineering requirements for a host of waste management unit operations (e.g., tank mixing, pipeline transport, and filtration). The most prevalent approach for determining particle size and density distribution is highly laborious and involves identifying individual particles using scanning electron microscope/x-ray diffraction and then acquiring the density of the materials from the technical literature. Other methods simply approximate individual particle densities by assuming chemical composition, rather than obtaining actual measurements of particle density. To overcome these limitations, a Particle Shadow-graph Velocimetry and Size (PSVS) system has been designed to simultaneously obtain particle size and density distributions for a broad range of Hanford tank waste materials existing as both individual particles and agglomerates. The PSVS system uses optical hardware, a temperature-controlled settling column, and particle introduction chamber to accurately and reproducibly obtain images of settling particles. Image analysis software provides a highly accurate determination of both particle terminal velocity and equivalent spherical particle diameter. The particle density is then calculated from Newton's terminal settling theory. The PSVS system was designed to accurately image particle/agglomerate sizes between 10 and 1000 μm and particle/agglomerate densities ranging from 1.4 to 11.5 g/cm{sup 3}, where the maximum terminal velocity does not exceed 10 cm/s. Preliminary testing was completed with standard materials and results were in good agreement with terminal settling theory. Recent results of this method development are presented, as well as experimental design. The primary goal of these PSVS system tests was to obtain accurate and reproducible particle size and velocity measurements to estimate particle densities within

  18. Measurement of snow particle size and speed in powder snow avalanches

    NASA Astrophysics Data System (ADS)

    Ito, Yoichi; Nishimura, Kouichi; Naaim-Bouvet, Florence; Bellot, Hervé; Thibert, Emmanuel; Ravanat, Xavier; Fontaine, Firmin

    2015-04-01

    Generally snow avalanches consist a dense-flow layer at the bottom and a powder snow cloud on top. Snow particle size and speed are key parameters to describe the turbulent condition in the powder cloud, however, the information on the particles were not well investigated. In this study, we observed powder snow avalanches using a snow particle counter (SPC) to measure the particle size and speed. The SPC is an optical device consisting a laser diode and photodiode; a pulse signal proportional to its diameter is generated resulting from a snow particle passing through the sensing volume. In general use, the signals are sent to a transducer and divided into 32 size classes based on particle diameter to observe the snow particle size distribution and mass flux at 1-s intervals. In this study, the direct output signal from the transducer was also acquired at a high frequency to obtain the original pulse signal produced by each snow particle. Then the speed of each particle can be calculated using the peak of the pulse, which corresponds to particle diameter and the duration over which the particle passes through the sampling area. We also employed an ultrasonic anemometer to measure air flow speed. Both sensors were installed at the Col du Lautaret Pass in the French Alps. The results of the particle size and speed distribution were then compared with airflow movement in the powder cloud. The ratio of the particle and airflow speeds changed by the particle size distribution and the distance from the dense-flow layer.

  19. Intensity and polarization of light scattered by size distributions of randomly oriented nonspherical particles

    NASA Technical Reports Server (NTRS)

    Mishchenko, M. I.; Travis, L. D.

    1993-01-01

    Calculations of light scattering by small particles are important in many diverse fields of science and engineering. In many cases of practical interest, scattering particles are nonspherical and are distributed over sizes and orientations. However, accurate light scattering computations for ensembles of nonspherical particles are difficult and time-consuming, and the literature in which such calculations are reported is rather scarce. In this paper, the T-matrix approach, as extended recently to randomly oriented particles, is used to calculate rigorously light scattering by size distributions of randomly oriented axially symmetric particles. To model the variation of particle sizes in real ensembles, we use a power law distribution typical of some terrestrial aerosols. Contour plots of intensity and degree of linear polarization for polydisperse prolate and oblate spheroids of different aspect ratios and effective equivalent-sphere size parameters from 0 to 10 are calculated and compared with calculations for equivalent spheres. The angular scattering behavior of nonspherical polydispersions is found to be greatly different from that of spheres, while the scattering properties of oblate and prolate spheroids of the same aspect ratio are similar. With increasing particle size, both intensity and polarization become more shape-dependent. In general, nonspherical particles are stronger side scatterers and weaker backscatterers than equivalent spheres. With increasing aspect ratio of nonspherical particles polarization tends to be predominantly positive. Possible effects of particle nonsphericity on optical remote sensing of atmospheric aerosols are discussed.

  20. Uncertainty in volcanic ash particle size distribution and implications for infrared remote sensing and airspace management

    NASA Astrophysics Data System (ADS)

    Western, L.; Watson, M.; Francis, P. N.

    2014-12-01

    Volcanic ash particle size distributions are critical in determining the fate of airborne ash in drifting clouds. A significant amount of global airspace is managed using dispersion models that rely on a single ash particle size distribution, derived from a single source - Hobbs et al., 1991. This is clearly wholly inadequate given the range of magmatic compositions and eruptive styles that volcanoes present. Available measurements of airborne ash lognormal particle size distributions show geometric standard deviation values that range from 1.0 - 2.5, with others showing mainly polymodal distributions. This paucity of data pertaining to airborne sampling of volcanic ash results in large uncertainties both when using an assumed distribution to retrieve mass loadings from satellite observations and when prescribing particle size distributions of ash in dispersion models. Uncertainty in the particle size distribution can yield order of magnitude differences to mass loading retrievals of an ash cloud from satellite observations, a result that can easily reclassify zones of airspace closure. The uncertainty arises from the assumptions made when defining both the geometric particle size and particle single scattering properties in terms of an effective radius. This has significant implications for airspace management and emphasises the need for an improved quantification of airborne volcanic ash particle size distributions.

  1. Ion acoustic and dust acoustic waves at finite size of plasma particles

    SciTech Connect

    Andreev, Pavel A. Kuz'menkov, L. S.

    2015-03-15

    We consider the influence of the finite size of ions on the properties of classic plasmas. We focus our attention at the ion acoustic waves for electron-ion plasmas. We also consider the dusty plasmas where we account the finite size of ions and particles of dust and consider the dispersion of dust acoustic waves. The finite size of particles is a classical effect as well as the Coulomb interaction. The finite size of particles considerably contributes to the properties of the dense plasmas in the small wavelength limit. Low temperature dense plasmas, revealing the quantum effects, are also affected by the finite size of plasma particles. Consequently, it is important to consider the finite size of ions in the quantum plasmas as well.

  2. The Effect of Particle Size on Hydrolysis Reaction Rates and Rheological Properties in Cellulosic Slurries

    NASA Astrophysics Data System (ADS)

    Dasari, Rajesh K.; Berson, R. Eric

    The effect of varying initial particle sizes on enzymatic hydrolysis rates and rheological properties of sawdust slurries is investigated. Slurries with four particle size ranges (33 μm < x ≤ 75 μm, 150 μm < x ≤ 180 μm 295 μm < x ≤ 425 μm, and 590 μm < x ≤ 850 μm) were subjected to enzymatic hydrolysis using an enzyme dosage of filter paper units per gram of cellulose at 50°C and 250 rpm in shaker flasks. At lower initial particle sizes, higher enzymatic reaction rates and conversions of cellulose to glucose were observed. After 72 h 50 and 55% more glucose was produced from the smallest size particles than the largest size ones, for initial solids concentration of 10 and 13% (w/w), respectively. The effect of initial particle size on viscosity over a range of shear was also investigated. For equivalent initial solids concentration, smaller particle sizes result in lower viscosities such that at a concentration of 10% (w/w), the viscosity decreased from 3000 cP for 150 μm < x ≤ 180 μm particle size slurries to 61.4 cP for 33 μm < x ≤ 75 μm particle size slurries. Results indicate particle size reduction may provide a means for reducing the long residence time required for the enzymatic hydrolysis step in the conversion of biomass to ethanol. Furthermore, the corresponding reduction in viscosity may allow for higher solids loading and reduced reactor sizes during large-scale processing.

  3. Particle Size Effect on Wetting Kinetics of a Nanosuspension Drop: MD Simulations

    NASA Astrophysics Data System (ADS)

    Shi, Baiou; Webb, Edmund

    The behavior of nano-fluids, or fluid suspensions containing nanoparticles, has garnered tremendous attention recently for applications in advanced manufacturing. In our previous results from MD simulations, for a wetting system with different advancing contact angles, cases where self-pinning was observed were compared to cases where it was not and relevant forces on particles at the contact line were computed. To advance this work, the roles of particle size and particle loading are examined. Results presented illustrate how particle size affects spreading kinetics and how this connects to dynamic droplet morphology and relevant forces that exist nearby the contact line region. Furthermore, increased particle size in simulations permits a more detailed investigation of particle/substrate interfacial contributions to behavior observed at the advancing contact line. Based on changes in spreading kinetics with particle size, forces between the particle and liquid front are predicted and compared to those computed from simulations. At high loading, particle/particle interactions become relevant and forces computed between particles entrained to an advancing contact line will be presented.

  4. Laboratory and field evaluations of the LISST-100 instrument for suspended particle size determinations

    USGS Publications Warehouse

    Gartner, J.W.; Cheng, R.T.; Wang, P.-F.; Richter, K.

    2001-01-01

    Advances in technology have resulted in a new instrument that is designed for in-situ determination of particle size spectra. Such an instrument that can measure undisturbed particle size distributions is much needed for sediment transport studies. The LISST-100 (Laser In-Situ Scattering and Transmissometry) uses the principle of laser diffraction to obtain the size distribution and volume concentration of suspended material in 32 size classes logarithmically spaced between 1.25 and 250 ??m. This paper describes a laboratory evaluation of the ability of LISST-100 to determine particle sizes using suspensions of single size, artificial particles. Findings show the instrument is able to determine particle size to within about 10% with increasing error as particle size increases. The instrument determines volume (or mass) concentration using a volume conversion factor Cv. This volume conversion factor is theoretically a constant. In the laboratory evaluation Cv is found to vary by a factor of about three over the particle size range between 5 and 200 ??m. Results from field studies in South San Francisco Bay show that values of mass concentration of suspended marine sediments estimated by LISST-100 agree favorably with estimates from optical backscatterance sensors if an appropriate value of Cv, according to mean size, is used and the assumed average particle (aggregate) density is carefully chosen. Analyses of size distribution of suspended materials in South San Francisco Bay over multiple tide cycles suggest the likelihood of different sources of sediment because of different size characteristics during flood and ebb cycles. ?? 2001 Elsevier Science B.V.

  5. Mars Dust: Characterization of Particle Size and Electrostatic Charge Distribution

    NASA Technical Reports Server (NTRS)

    Mazumder, M. K.; Saini, D.; Biris, A. S.; Sriama, P. K.; Calle, C.; Buhler, C.

    2004-01-01

    Some of the latest pictures of Mars surface sent by NASA's Spirit rover in early January, 2004, show very cohesive, "mud-like" dust layers. Significant amounts of dust clouds are present in the atmosphere of Mars [1-4]. NASA spacecraft missions to Mars confirmed hypotheses from telescopic work that changes observed in the planet's surface markings are caused by wind-driven redistribution of dust. In these dust storms, particles with a wide range of diameters (less than 1 micrometer to 50 micrometers) are a serious problem to solar cells, spacecraft, and spacesuits. Dust storms may cover the entire planet for an extended period of time [5]. It is highly probable that the particles are charged electrostatically by triboelectrification and by UV irradiation.

  6. Investigation of aged aerosols in size-resolved Asian dust storm particles transported from Beijing, China to Incheon, Korea using low-Z particle EPMA

    NASA Astrophysics Data System (ADS)

    Geng, H.; Hwang, H. J.; Liu, X.; Dong, S.; Ro, C.-U.

    2013-10-01

    This is the first study of Asian dust storm (ADS) particles collected in Beijing, China and Incheon, Korea during the same spring ADS event. Using a seven-stage May impactor and a quantitative electron probe X-ray microanalysis (ED-EPMA, also known as low-Z particle EPMA), we examined the composition and morphology of 4200 aerosol particles at stages 1-6 (with a size cut-off of 16, 8, 4, 2, 1, and 0.5 μm in equivalent aerodynamic diameter, respectively) collected during an ADS event on 28-29 April 2005. The results showed that there were large differences in the chemical compositions between particles in sample S1 collected in Beijing immediately after the peak time of the ADS and in samples S2 and S3, which were collected in Incheon approximately 5 h and 24 h later, respectively. In sample S1, mineral dust particles accounted for more than 88% in relative number abundance at stages 1-5, and organic carbon (OC) and reacted NaCl-containing particles accounted for 24% and 32%, respectively, at stage 6. On the other hand, in samples S2 and S3, in addition to approximately 60% mineral dust, many sea salt particles reacted with airborne SO2 and NOx, often mixed with mineral dust, were encountered at stages 1-5, and (C, N, O, S)-rich particles (likely a mixture of water-soluble organic carbon with (NH4)2SO4 and NH4NO3) and K-containing particles were abundantly observed at stage 6. This suggests that the secondary aerosols and the internal mixture of mineral dust with sea spray aerosol increased when the ADS particles passed over the Yellow Sea. In the reacted or aged mineral dust and sea salt particles, nitrate-containing and both nitrate- and sulfate-containing species vastly outnumbered the sulfate-containing species, implying that ambient nitrogen oxides had a greater influence on the atmospheric particles during the ADS episode than SO2. In addition to partially- or totally-reacted CaCO3, reacted or aged Mg-containing aluminosilicates (likely including amesite

  7. Production of Large-Particle-Size Monodisperse Latexes in Microgravity

    NASA Technical Reports Server (NTRS)

    Vanderhoff, J. W.; Micale, F. J.; El-Aasser, M. S.; Kornfeld, M.

    1985-01-01

    A latex is a suspension of very tiny (micrometer-size) plastic spheres in water, stabilized by emulsifiers. The growth of billions of these tiny plastic spheres to sizes larger than can be grown on Earth is attempted while keeping all of them exactly the same size and perfectly spherical. Thus far on several of the Monodisperse Latex Reactor (MLR) flights, the latex spheres have been returned to Earth with standard deviations of better than 1.4%. In microgravity the absence of buoyancy effects has allowed growth of the balls up to 30 micrometers in diameter thus far. The MLR has now flown 5 times on the Shuttle. The MLR has now produced the first commercial space product; that is the first commercial material ever manufactured in space and marketed on Earth. Once it is demonstrated that these large-size-monodisperse latexes can be routinely produced in quantity and quality, they can be marketed for many types of scientific applications. They can be used in biomedical research for such things as drug carriers and tracers in the body, human and animal blood flow studies, membrane and pore-sizing in the body, and medical diagnostic tests.

  8. Concentration, Size Distribution, and Infectivity of Airborne Particles Carrying Swine Viruses

    PubMed Central

    Alonso, Carmen; Raynor, Peter C.; Davies, Peter R.; Torremorell, Montserrat

    2015-01-01

    When pathogens become airborne, they travel associated with particles of different size and composition. Particle size determines the distance across which pathogens can be transported, as well as the site of deposition and the survivability of the pathogen. Despite the importance of this information, the size distribution of particles bearing viruses emitted by infectious animals remains unknown. In this study we characterized the concentration and size distribution of inhalable particles that transport influenza A virus (IAV), porcine reproductive and respiratory syndrome virus (PRRSV), and porcine epidemic diarrhea virus (PEDV) generated by acutely infected pigs and assessed virus viability for each particle size range. Aerosols from experimentally infected pigs were sampled for 24 days using an Andersen cascade impactor able to separate particles by size (ranging from 0.4 to 10 micrometer (μm) in diameter). Air samples collected for the first 9, 20 and the last 3 days of the study were analyzed for IAV, PRRSV and PEDV, respectively, using quantitative reverse transcription polymerase chain reaction (RT-PCR) and quantified as geometric mean copies/m3 within each size range. IAV was detected in all particle size ranges in quantities ranging from 5.5x102 (in particles ranging from 1.1 to 2.1μm) to 4.3x105 RNA copies/m3 in the largest particles (9.0–10.0μm). PRRSV was detected in all size ranges except particles between 0.7 and 2.1μm in quantities ranging from 6x102 (0.4–0.7μm) to 5.1x104 RNA copies/m3 (9.0–10.0μm). PEDV, an enteric virus, was detected in all particle sizes and in higher quantities than IAV and PRRSV (p < 0.0001) ranging from 1.3x106 (0.4–0.7μm) to 3.5x108 RNA copies/m3 (9.0–10.0μm). Infectious status was demonstrated for the 3 viruses, and in the case of IAV and PRRSV, viruses were isolated from particles larger than 2.1μm. In summary, our results indicated that airborne PEDV, IAV and PRRSV can be found in a wide range of

  9. Interaction of tallow and hay particle size on ruminal parameters.

    PubMed

    Lewis, W D; Bertrand, J A; Jenkins, T C

    1999-07-01

    Four nonlactating ruminally cannulated Holstein cows were used in a 4 x 4 Latin square experiment with 4 21-d periods to determine if the effects of dietary fat would be affected by hay particle length. Treatments consisted of two levels of tallow (0 and 5%) and two hay particle lengths (short-cut and long-cut) in a 2 x 2 factorial. Diets contained alfalfa hay, corn silage, and concentrate [1:1:2, dry matter (DM) basis] fed as a total mixed ration (TMR) once per day. Samples of the 0 and 5% tallow TMR were ground and incubated in situ in polyester bags for 24 and 48 h. Ruminal samples were taken on day 21 at 0800 h and at 2-h intervals until 1600 h. The total tract digestibilities of acid detergent fiber (ADF) and neutral detergent fiber (NDF) were not affected by tallow or by hay by tallow interactions. There was a trend for tallow to improve total tract digestibility of crude protein (CP) (70.2 vs. 74.7%). After 48 h of ruminal incubation, tallow significantly decreased the digestibilities of DM, ADF, and NDF. No hay length by tallow interactions for DM, NDF, ADF or CP digestibilities occurred after 24 or 48 h. Tallow increased concentrations of propionate and decreased concentrations of acetate and valerate and the acetate-to-propionate ratio. Total volatile fatty acids increased when tallow was added to diets with short-cut hay, which suggests that when unprotected fat is added to diets with a high level of hay, a short-cut hay length may be advantageous. This result may be due to shorter rumen retention time of feed particles, which reduces the time for fatty acids to exert antimicrobial effects. Or, it may because the increased surface area of the hay particle provides more area for microbial attachment and increased fermentation.

  10. Individual Aerosol Particles from Biomass Burning in Southern Africa. 1; Compositions and Size Distributions of Carbonaceous Particles

    NASA Technical Reports Server (NTRS)

    Posfai, Mihaly; Simonics, Renata; Li, Jia; Hobbs, Peter V.; Buseck, Peter R.

    2003-01-01

    Individual aerosol particles in smoke plumes from biomass fires and in regional hazes in southern Africa were studied using analytical transmission electron microscopy (TEM), which allowed detailed characterization of carbonaceous particle types in smoke and determination of changes in particle properties and concentrations during smoke aging. Based on composition, morphology, and microstructure, three distinct types of carbonaceous particles were present in the smoke: organic particles with inorganic (K-salt) inclusions, tar ball particles, and soot. The relative number concentrations of organic particles were largest in young smoke, whereas tar balls were dominant in a slightly aged (1 hour) smoke from a smoldering fire. Flaming fires emitted relatively more soot particles than smoldering fires, but soot was a minor constituent of all studied plumes. Further aging caused the accumulation of sulfate on organic and soot particles, as indicated by the large number of internally mixed organic/sulfate and soot/sulfate particles in the regional haze. Externally mixed ammonium sulfate particles dominated in the boundary layer hazes, whereas organic/sulfate particles were the most abundant type in the upper hazes. Apparently, elevated haze layers were more strongly affected by biomass smoke than those within the boundary layer. Based on size distributions and the observed patterns of internal mixing, we hypothesize that organic and soot particles are the cloud-nucleating constituents of biomass smoke aerosols. Sea-salt particles dominated in the samples taken in stratus clouds over the Atlantic Ocean, off the coast of Namibia, whereas a distinct haze layer above the clouds consisted of aged biomass smoke particles.

  11. Individual aerosol particles from biomass burning in southern Africa: 1. Compositions and size distributions of carbonaceous particles

    NASA Astrophysics Data System (ADS)

    Pósfai, MiháLy; Simonics, RenáTa; Li, Jia; Hobbs, Peter V.; Buseck, Peter R.

    2003-07-01

    Individual aerosol particles in smoke plumes from biomass fires and in regional hazes in southern Africa were studied using analytical transmission electron microscopy (TEM), which allowed detailed characterization of carbonaceous particle types in smoke and determination of changes in particle properties and concentrations during smoke aging. Based on composition, morphology, and microstructure, three distinct types of carbonaceous particles were present in the smoke: organic particles with inorganic (K-salt) inclusions, "tar ball" particles, and soot. The relative number concentrations of organic particles were largest in young smoke, whereas tar balls were dominant in a slightly aged (˜1 hour) smoke from a smoldering fire. Flaming fires emitted relatively more soot particles than smoldering fires, but soot was a minor constituent of all studied plumes. Further aging caused the accumulation of sulfate on organic and soot particles, as indicated by the large number of internally mixed organic/sulfate and soot/sulfate particles in the regional haze. Externally mixed ammonium sulfate particles dominated in the boundary layer hazes, whereas organic/sulfate particles were the most abundant type in the upper hazes. Apparently, elevated haze layers were more strongly affected by biomass smoke than those within the boundary layer. Based on size distributions and the observed patterns of internal mixing, we hypothesize that organic and soot particles are the cloud-nucleating constituents of biomass smoke aerosols. Sea-salt particles dominated in the samples taken in stratus clouds over the Atlantic Ocean, off the coast of Namibia, whereas a distinct haze layer above the clouds consisted of aged biomass smoke particles.

  12. Number size distribution, mass concentration, and particle composition of PM1, PM2.5, and PM10 in bag filling areas of carbon black production.

    PubMed

    Kuhlbusch, T A J; Neumann, S; Fissan, H

    2004-10-01

    Number size characteristics and PM10 mass concentrations of particles emitted during the packaging of various kinds of carbon blacks were measured continuously in the bag filling areas of three carbon black plants and concurrently at ambient comparison sites. PM10, PM2.5, and PM1 dust fractions were also determined in the bag filling areas. The filter samples were then analyzed for elemental and organic carbon. Comparisons of the measured number size distributions and mass concentrations during bag filling activities with those measured parallel at the ambient site and with those determined during nonworking periods in the work area enabled the characterization of emitted particles. PM10 mass concentrations were consistently elevated (up to a factor of 20 compared to ambient concentrations) during working periods in the bag filling area. Detailed analysis revealed that the carbon black particles released by bag filling activities had a size distribution starting at approximately 400 nm aerodynamic diameter (dae) with modes around 1 microm dae and > 8 microm dae. Ultrafine particles (< 100 nm dae), detected in the bag filling areas, were most likely attributed to noncarbon black sources such as forklift and gas heater emissions.

  13. Effect of particle size on arsenic bioaccessibility in gold mine tailings of Nova Scotia.

    PubMed

    Meunier, Louise; Koch, Iris; Reimer, Kenneth J

    2011-05-01

    Tailings samples from the Goldenville and Montague abandoned gold mines in Nova Scotia, Canada were subjected to bioaccessibility tests to examine the effects of the choice of particle size fraction on the bioaccessibility of arsenic. The proportion of finer grains (<150μm) in this sample set varied from 6.0 to 66wt.%. Samples were sieved to <250, <150, and <45μm particle size fractions. The arsenic bioaccessibility ranged from less than 1.0 to 48%, but no systematic variation was observed (p>0.13) precluding the association of greater percent arsenic bioaccessibility with a specific particle size fraction, method or site. On the other hand, the highest bioaccessible arsenic concentrations (up to 5200mgkg(-1)) were consistently observed in samples sieved to the <45μm particle size, for both the physiologically based extraction test and a glycine-buffered bioaccessibility method (in 89 and 87% of samples tested, respectively). This was due to higher total arsenic concentrations in the same particle size fraction. Grain maps obtained by X-ray absorption spectroscopy indicate that samples with the highest percent arsenic bioaccessibility contain amorphous pentavalent arsenic distributed throughout the sample as well as grains coated with pentavalent arsenic. Arsenic bioaccessibilities lower than 10% were found in samples with encapsulated arsenopyrite and some grains composed primarily of pentavalent arsenic. The <45μm particle size fraction appears to yield conservative (protective) estimates of the bioaccessible dose of arsenic, but wide variations exist in particle size distribution and arsenic bioaccessibility between samples. As well, sieving to <45μm may exclude potentially relevant particles by restricting the study to an average particle size that is smaller than the average size of particles found on human hands, and may unduly influence the resulting bioaccessibility measurements.

  14. A Review of Discrete Element Method (DEM) Particle Shapes and Size Distributions for Lunar Soil

    NASA Technical Reports Server (NTRS)

    Lane, John E.; Metzger, Philip T.; Wilkinson, R. Allen

    2010-01-01

    As part of ongoing efforts to develop models of lunar soil mechanics, this report reviews two topics that are important to discrete element method (DEM) modeling the behavior of soils (such as lunar soils): (1) methods of modeling particle shapes and (2) analytical representations of particle size distribution. The choice of particle shape complexity is driven primarily by opposing tradeoffs with total number of particles, computer memory, and total simulation computer processing time. The choice is also dependent on available DEM software capabilities. For example, PFC2D/PFC3D and EDEM support clustering of spheres; MIMES incorporates superquadric particle shapes; and BLOKS3D provides polyhedra shapes. Most commercial and custom DEM software supports some type of complex particle shape beyond the standard sphere. Convex polyhedra, clusters of spheres and single parametric particle shapes such as the ellipsoid, polyellipsoid, and superquadric, are all motivated by the desire to introduce asymmetry into the particle shape, as well as edges and corners, in order to better simulate actual granular particle shapes and behavior. An empirical particle size distribution (PSD) formula is shown to fit desert sand data from Bagnold. Particle size data of JSC-1a obtained from a fine particle analyzer at the NASA Kennedy Space Center is also fitted to a similar empirical PSD function.

  15. A concept of an automated function control for ambient aerosol measurements using mobility particle size spectrometers

    NASA Astrophysics Data System (ADS)

    Bastian, S.; Löschau, G.; Wiedensohler, A.

    2014-04-01

    An automated function control unit was developed to regularly check the ambient particle number concentration derived from a mobility particle size spectrometer as well as its zero-point behaviour. The function control allows unattended quality assurance experiments at remote air quality monitoring or research stations under field conditions. The automated function control also has the advantage of being able to get a faster system stability response than the recommended on-site comparisons with reference instruments. The method is based on a comparison of the total particle number concentration measured by a mobility particle size spectrometer and a condensation particle counter while removing diffusive particles smaller than 20 nm in diameter. In practice, the small particles are removed by a set of diffusion screens, as traditionally used in a diffusion battery. Another feature of the automated function control is to check the zero-point behaviour of the ambient aerosol passing through a high-efficiency particulate air (HEPA) filter. The performance of the function control is illustrated with the aid of a 1-year data set recorded at Annaberg-Buchholz, a station in the Saxon air quality monitoring network. During the period of concern, the total particle number concentration derived from the mobility particle size spectrometer slightly overestimated the particle number concentration recorded by the condensation particle counter by 2 % (grand average). Based on our first year of experience with the function control, we developed tolerance criteria that allow a performance evaluation of a tested mobility particle size spectrometer with respect to the total particle number concentration. We conclude that the automated function control enhances the quality and reliability of unattended long-term particle number size distribution measurements. This will have beneficial effects for intercomparison studies involving different measurement sites, and help provide a higher

  16. Influence of Particle Size on Reaction Selectivity in Cyclohexene Hydrogenation and Dehydrogenation over Silica-Supported Monodisperse Pt Particles

    SciTech Connect

    Rioux, R. M.; Hsu, B. B.; Grass, M. E.; Song, H.; Somorjai, Gabor A.

    2008-07-11

    The role of particle size during the hydrogenation/dehydrogenation of cyclohexene (10 Torr C{sub 6}H{sub 10}, 200-600 Torr H{sub 2}, and 273-650 K) was studied over a series of monodisperse Pt/SBA-15 catalysts. The conversion of cyclohexene in the presence of excess H{sub 2} (H{sub 2}:C{sub 6}H{sub 10} ratio = 20-60) is characterized by three regimes: hydrogenation of cyclohexene to cyclohexane at low temperature (< 423 K), an intermediate temperature range in which both hydrogenation and dehydrogenation occur; and a high temperature regime in which the dehydrogenation of cyclohexene dominates (> 573 K). The rate of both reactions demonstrated maxima with temperature, regardless of Pt particle size. For the hydrogenation of cyclohexene, a non-Arrhenius temperature dependence (apparent negative activation energy) was observed. Hydrogenation is structure insensitive at low temperatures, and apparently structure sensitive in the non-Arrhenius regime; the origin of the particle-size dependent reactivity with temperature is attributed to a change in the coverage of reactive hydrogen. Small particles were more active for dehydrogenation and had lower apparent activation energies than large particles. The selectivity can be controlled by changing the particle size, which is attributed to the structure sensitivity of both reactions in the temperature regime where hydrogenation and dehydrogenation are catalyzed simultaneously.

  17. The effect of particle size on the morphology and thermodynamics of diblock copolymer/tethered-particle membranes

    SciTech Connect

    Zhang, Bo; Edwards, Brian J.

    2015-06-07

    A combination of self-consistent field theory and density functional theory was used to examine the effect of particle size on the stable, 3-dimensional equilibrium morphologies formed by diblock copolymers with a tethered nanoparticle attached either between the two blocks or at the end of one of the blocks. Particle size was varied between one and four tenths of the radius of gyration of the diblock polymer chain for neutral particles as well as those either favoring or disfavoring segments of the copolymer blocks. Phase diagrams were constructed and analyzed in terms of thermodynamic diagrams to understand the physics associated with the molecular-level self-assembly processes. Typical morphologies were observed, such as lamellar, spheroidal, cylindrical, gyroidal, and perforated lamellar, with the primary concentration region of the tethered particles being influenced heavily by particle size and tethering location, strength of the particle-segment energetic interactions, chain length, and copolymer radius of gyration. The effect of the simulation box size on the observed morphology and system thermodynamics was also investigated, indicating possible effects of confinement upon the system self-assembly processes.

  18. The effect of particle size on the morphology and thermodynamics of diblock copolymer/tethered-particle membranes.

    PubMed

    Zhang, Bo; Edwards, Brian J

    2015-06-07

    A combination of self-consistent field theory and density functional theory was used to examine the effect of particle size on the stable, 3-dimensional equilibrium morphologies formed by diblock copolymers with a tethered nanoparticle attached either between the two blocks or at the end of one of the blocks. Particle size was varied between one and four tenths of the radius of gyration of the diblock polymer chain for neutral particles as well as those either favoring or disfavoring segments of the copolymer blocks. Phase diagrams were constructed and analyzed in terms of thermodynamic diagrams to understand the physics associated with the molecular-level self-assembly processes. Typical morphologies were observed, such as lamellar, spheroidal, cylindrical, gyroidal, and perforated lamellar, with the primary concentration region of the tethered particles being influenced heavily by particle size and tethering location, strength of the particle-segment energetic interactions, chain length, and copolymer radius of gyration. The effect of the simulation box size on the observed morphology and system thermodynamics was also investigated, indicating possible effects of confinement upon the system self-assembly processes.

  19. Ti particle-reinforced surface layers in Al: Effect of particle size on microstructure, hardness and wear

    SciTech Connect

    Mordyuk, B.N.; Silberschmidt, V.V.; Prokopenko, G.I.; Nesterenko, Yu.V.; Iefimov, M.O.

    2010-11-15

    Two types of Ti particles are used in an ultrasonic impact peening (UIP) process to modify sub-surface layers of cp aluminium atomized, with an average size of approx. 20 {mu}m and milled (0.3-0.5 {mu}m). They are introduced into a zone of severe plastic deformation induced by UIP. The effect of Ti particles of different sizes on microstructure, phase composition, microhardness and wear resistance of sub-surface composite layers in aluminium is studied in this paper. The formed layers of a composite reinforced with smaller particles have a highly misoriented fine-grain microstructure of its matrix with a mean grain size of 200-400 nm, while reinforcement with larger particles results in relatively large Al grains (1-2 {mu}m). XRD, SEM, EDX and TEM studies confirm significantly higher particle/matrix bonding in the former case due to formation of a Ti{sub 3}Al interlayer around Ti particles with rough surface caused by milling. Different microstructures determine hardness and wear resistance of reinforced aluminium layers: while higher magnitudes of microhardness are observed for both composites (when compared with those of annealed and UIP-treated aluminium), the wear resistance is improved only in the case of reinforcement with small particles.

  20. Particle size reduction in debris flows: Laboratory experiments compared with field data from Inyo Creek, California

    NASA Astrophysics Data System (ADS)

    Arabnia, O.; Sklar, L. S.; Mclaughlin, M. K.

    2014-12-01

    Rock particles in debris flows are reduced in size through abrasion and fracture. Wear of coarse sediments results in production of finer particles, which alter the bulk material rheology and influence flow dynamics and runout distance. Particle wear also affects the size distribution of coarse particles, transforming the initial sediment size distribution produced on hillslopes into that delivered to the fluvial channel network. A better understanding of the controls on particle wear in debris flows would aid in the inferring flow conditions from debris flow deposits, in estimating the initial size of sediments entrained in the flow, and in modeling debris flow dynamics and mapping hazards. The rate of particle size reduction with distance traveled should depend on the intensity of particle interactions with other particles and the flow boundary, and on rock resistance to wear. We seek a geomorphic transport law to predict rate of particle wear with debris flow travel distance as a function of particle size distribution, flow depth, channel slope, fluid composition and rock strength. Here we use four rotating drums to create laboratory debris flows across a range of scales. Drum diameters range from 0.2 to 4.0 m, with the largest drum able to accommodate up to 2 Mg of material, including boulders. Each drum has vanes along the boundary to prevent sliding. Initial experiments use angular clasts of durable granodiorite; later experiments will use less resistant rock types. Shear rate is varied by changing drum rotational velocity. We begin experiments with well-sorted coarse particle size distributions, which are allowed to evolve through particle wear. The fluid is initially clear water, which rapidly acquires fine-grained wear products. After each travel increment all coarse particles (mass > 0.4 g) are weighed individually. We quantify particle wear rates using statistics of size and mass distributions, and by fitting various comminution functions to the data

  1. Radial particle-size segregation during packing of particulates into cylindrical containers

    USGS Publications Warehouse

    Ripple, C.D.; James, R.V.; Rubin, J.

    1973-01-01

    In a series of experiments, soil materials were placed in long cylindrical containers, using various packing procedures. Soil columns produced by deposition and simultaneous vibratory compaction were dense and axially uniform, but showed significant radial segregation of particle sizes. Similar results were obtained with deposition and simultaneous impact-type compaction when the impacts resulted in significant container "bouncing". The latter procedure, modified to minimize "bouncing" produced dense, uniform soil columns, showing little radial particle-size segregation. Other procedures tested (deposition alone and deposition followed by compaction) did not result in radial segregation, but produced columns showing either relatively low or axially nonuniform densities. Current data suggest that radial particle-size segregation is mainly due to vibration-induced particle circulation in which particles of various sizes have different circulation rates and paths. ?? 1973.

  2. Particle size and surfactant effects on chemical mechanical polishing of glass using silica-based slurry

    SciTech Connect

    Zhang Zefang; Liu Weili; Song Zhitang

    2010-10-01

    This study explores the effect of particle size and surfactant on the chemical mechanical polishing (CMP) of glass using colloidal silica-based slurry. It was found that the material removal rate strongly depends on the particle size and the types of surfactants and that the rms roughness was independent of particle size and correlated to surfactants. On the basis of polishing results, it was concluded that the main polishing mechanism was changed from indentation mechanism to surface-area mechanism, with the variation of particle size. In addition, the molecular structure, charge type, and lubricating effect of the surfactants play an important role in the dispersion of abrasive particles and in the CMP performance.

  3. Size Differentiation Of A Continuous Stream Of Particles Using Acoustic Emissions

    NASA Astrophysics Data System (ADS)

    Nsugbe, E.; Starr, A.; Foote, P.; Ruiz-Carcel, C.; Jennions, I.

    2016-11-01

    Procter and Gamble (P&G) require an online system that can monitor the particle size distribution of their washing powder mixing process. This would enable the process to take a closed loop form which would enable process optimisation to take place in real time. Acoustic Emission (AE) was selected as the sensing method due to its non-invasive nature and primary sensitivity to frequencies which particle events emanate. This work details the results of the first experiment carried out in this research project. This experiment involved the use of AE to distinguish between the sizes of sieved polyethylene particle (53-250microns) and glass beads (150-600microns) which were dispensed on a target plate using a funnel. By conducting a threshold analysis of the impact peaks in the signal, the sizes of the particles could be distinguished and a signal feature was found which could be directly linked to the sizes of the particles.

  4. Soot particle sizing based on analytical formula derived from laser-induced incandescence decay signals

    NASA Astrophysics Data System (ADS)

    Wu, Jian; Chen, Linghong; Yan, Mingming; Wu, Xuecheng; Gréhan, Gérard; Cen, Kefa

    2017-01-01

    The laser-induced incandescence (LII) signal during a heat-conduction-dominated cooling process was used to derive an analytical formula to describe the relationship between the soot particle size and the LII signal decay time by exponential fitting. The formula was used to determine particle sizes based on the experimental LII signals at different detection wavelengths for an atmospheric C2H4/air diffusion flame. The results agree with those obtained from temporal temperature measurements. The measurements and numerical calculations demonstrate that particle sizing depends weakly on the maximum temperature in the formula within a typical heat-up temperature range. The results show that based on this formula, a compact single-color LII detection system can be used for particle sizing with low uncertainty under most practical combustion conditions, at least in cases where heat conduction is dominant and occurs in a free molecular regime during particle cooling.

  5. Effect of particle size in a limestone-hydrochloric acid reaction system.

    PubMed

    Sun, Bo; Zhou, Qulan; Chen, Xi; Xu, Tongmo; Hui, Shien

    2010-07-15

    Experimental characterization of the wet flue gas desulfurization process is carried out using a model limestone-hydrochloric acid reaction system, with in-situ measurement of the dissolution rate and particle size distribution. The limestone source, initial particle size distribution, working temperature and pH value are varied in large ranges. The dissolution rate is found to be higher when the average particle size is smaller, the temperature is higher, or the pH is lower. An empirical equation is established to correlate the dissolution rate with the particle size and working conditions, which agrees well with measurements. The results may be useful for providing insights to improve the efficiency of the wet flue gas desulfurization process, as well as other solid particle-liquid solution reactions.

  6. Submicrometer-Sized Thermometer Particles Exploiting Selective Nucleic Acid Stability.

    PubMed

    Puddu, Michela; Mikutis, Gediminas; Stark, Wendelin J; Grass, Robert N

    2016-01-27

    Encapsulated nucleic acid selective damage quantification by real-time polymerase chain reaction is used as sensing mechanism to build a novel class of submicrometer size thermometer. Thanks to the high thermal and chemical stability, and the capability of storing the read accumulated thermal history, the sensor overcomes some of current limitations in small scale thermometry.

  7. Estimation of particle number size distributions from mass based model simulations and comparison to observations

    NASA Astrophysics Data System (ADS)

    Engler, Christa; Heinold, Bernd; Tegen, Ina

    2014-05-01

    The atmospheric Chemistry Transport Model system COSMO-MUSCAT was used to determine the particle mass concentrations of dust and anthropogenically emitted aerosol particles over Europe. The model system consists of the online coupled code of the operational forecast model COSMO (Schättler et al., 2009) and the chemistry-transport model MUSCAT (Wolke et al., 2012). For a four-months-period in 2008 (May to August), the dust and anthropogenic aerosol mass concentrations for six different species (sulfate, nitrate, ammonium, organic and elemental carbon and sea salt) were simulated. For the dust, five different size bins were used and a representative particle size and density were assumed for each size bin. Afterwards, the number concentration was calculated. For the anthropogenic aerosol, lognormal modes were assumed with a representative mode diameter, sigma and density for each component. These parameters were then used to convert the simulated mass concentrations to number concentrations and number size distributions for each component. Those individual size distributions can then be summed up to a total particle number size distribution. A first comparison with measurement data from the Cape Verde Islands showed a good agreement between observed and simulated dust particle size distributions. Both, the shape of the number size distributions and the order of magnitude of the particle number concentrations compared well. Only for the smallest size bin, observed numbers were occasionally higher, which can be explained by anthropogenic or biomass burning aerosol, which is included in the measurements of the total particle size distributions but was not included in the model runs. Comparisons of measured and simulated size distributions of the anthropogenic aerosol will be available soon. In case the data are available, we will also present an estimation of the particle number concentrations with the aerosol microphysical aerosol module ext-M7 for the duration of a

  8. Effect of sulfate and carbonate minerals on particle-size distributions in arid soils

    USGS Publications Warehouse

    Goossens, Dirk; Buck, Brenda J.; Teng, Yuazxin; Robins, Colin; Goldstein, Harland L.

    2014-01-01

    Arid soils pose unique problems during measurement and interpretation of particle-size distributions (PSDs) because they often contain high concentrations of water-soluble salts. This study investigates the effects of sulfate and carbonate minerals on grain-size analysis by comparing analyses in water, in which the minerals dissolve, and isopropanol (IPA), in which they do not. The presence of gypsum, in particular, substantially affects particle-size analysis once the concentration of gypsum in the sample exceeds the mineral’s solubility threshold. For smaller concentrations particle-size results are unaffected. This is because at concentrations above the solubility threshold fine particles cement together or bind to coarser particles or aggregates already present in the sample, or soluble mineral coatings enlarge grains. Formation of discrete crystallites exacerbates the problem. When soluble minerals are dissolved the original, insoluble grains will become partly or entirely liberated. Thus, removing soluble minerals will result in an increase in measured fine particles. Distortion of particle-size analysis is larger for sulfate minerals than for carbonate minerals because of the much higher solubility in water of the former. When possible, arid soils should be analyzed using a liquid in which the mineral grains do not dissolve, such as IPA, because the results will more accurately reflect the PSD under most arid soil field conditions. This is especially important when interpreting soil and environmental processes affected by particle size.

  9. Achieving Size Independent Hit-Rate in Single Particle Mass Spectrometry

    SciTech Connect

    Zelenyuk, Alla; Yang, Juan; Imre, Dan G.; Choi, Eric Y.

    2009-04-01

    Recent improvements in single particle mass spectrometers make it possible to optically detect, size, and characterize the compositions of individual particles with diameters larger than a micron and smaller than 100 nm. Based on particle detection in two stages of optical detection these instruments generate a precisely timed trigger pulse, which is used to fire the ion generation laser or lasers. Practical experience shows that the wide size range results in small, but significant differences in laser trigger timing between small and large particles. If not treated, the instrument hit-rate becomes size dependent and instrument operator is forced to optimize the instrument for the desired size range, while having to contend with a lower hit-rate for the other. The present paper presents an analysis of the problem, demonstrating that size dependence of laser trigger timing stems from the differences in the particle position within the detection laser beam at the instant of detection. It shows that it is possible to compensate for these differences by generation a laser trigger delay coefficient for individual particles as a function of particle time of flight, i.e. its size. The study also shows that a single function can be used to characterize particles with a wide range of densities.

  10. Fluorescent biodegradable PLGA particles with narrow size distributions: preparation by means of selective centrifugation.

    PubMed

    Gaumet, Marie; Gurny, Robert; Delie, Florence

    2007-09-05

    Size is the most studied parameter in the field of nanoparticle characterization but few studies have been performed on biodegradable particles with well-defined sizes. The aim of this work was to prepare fluorescent biodegradable polymeric particles having well-defined sizes and well-characterized surface properties. Poly(D,L-lactide-co-glycolide acid) particles were prepared by the emulsion evaporation process. Filtration and centrifugation were used to produce particle fractions in the narrow size range from polydispersed batches, and the efficiency of separation was compared. Selective centrifugation allowed for the preparation of five classes of particles having narrow size distribution (0.1, 0.3, 0.6, 1 and 2 microm). Particles were characterized in terms of size distribution, surface morphology, charge, residual surfactant and hydrophilicity. The results showed similar surface properties for all the batches. 3,3'-Dioctadecyloxacarbo-cyanine perchlorate has been successfully incorporated as a fluorescent dye and its ability to remain associated with the particles during cell culture experiments has been proven. Such particles may be used as an adequate tool for studying cellular uptake.

  11. Deformation Behavior of Sub-micron and Micron Sized Alumina Particles in Compression.

    SciTech Connect

    Sarobol, Pylin; Chandross, Michael E.; Carroll, Jay; Mook, William; Boyce, Brad; Kotula, Paul Gabriel; McKenzie, Bonnie Beth; Bufford, Daniel Charles; Hall, Aaron Christopher.

    2014-09-01

    The ability to integrate ceramics with other materials has been limited due to high temperature (>800degC) ceramic processing. Recently, researchers demonstrated a novel process , aerosol deposition (AD), to fabricate ceramic films at room temperature (RT). In this process, sub - micro n sized ceramic particles are accelerated by pressurized gas, impacted on the substrate, plastically deformed, and form a dense film under vacuum. This AD process eliminates high temperature processing thereby enabling new coatings and device integration, in which ceramics can be deposited on metals, plastics, and glass. However, k nowledge in fundamental mechanisms for ceramic particle s to deform and form a dense ceramic film is still needed and is essential in advancing this novel RT technology. In this wo rk, a combination of experimentation and atomistic simulation was used to determine the deformation behavior of sub - micron sized ceramic particle s ; this is the first fundamental step needed to explain coating formation in the AD process . High purity, singl e crystal, alpha alumina particles with nominal size s of 0.3 um and 3.0 um were examined. Particle characterization, using transmission electron microscopy (TEM ), showed that the 0.3 u m particles were relatively defect - free single crystals whereas 3.0 u m p articles were highly defective single crystals or particles contained low angle grain boundaries. Sub - micron sized Al 2 O 3 particles exhibited ductile failure in compression. In situ compression experiments showed 0.3um particles deformed plastically, fractured, and became polycrystalline. Moreover, dislocation activit y was observed within the se particles during compression . These sub - micron sized Al 2 O 3 particles exhibited large accum ulated strain (2 - 3 times those of micron - sized particles) before first fracture. I n agreement with the findings from experimentation , a tomistic simulation s of nano - Al 2 O 3 particles showed dislocation slip and

  12. Acoustophoretic separation of airborne millimeter-size particles by a Fresnel lens

    PubMed Central

    Cicek, Ahmet; Korozlu, Nurettin; Adem Kaya, Olgun; Ulug, Bulent

    2017-01-01

    We numerically demonstrate acoustophoretic separation of spherical solid particles in air by means of an acoustic Fresnel lens. Beside gravitational and drag forces, freely-falling millimeter-size particles experience large acoustic radiation forces around the focus of the lens, where interplay of forces lead to differentiation of particle trajectories with respect to either size or material properties. Due to the strong acoustic field at the focus, radiation force can divert particles with source intensities significantly smaller than those required for acoustic levitation in a standing field. When the lens is designed to have a focal length of 100 mm at 25 kHz, finite-element method simulations reveal a sharp focus with a full-width at half-maximum of 0.5 wavelenghts and a field enhancement of 18 dB. Through numerical calculation of forces and simulation of particle trajectories, we demonstrate size-based separation of acrylic particles at a source sound pressure level of 153 dB such that particles with diameters larger than 0.5 mm are admitted into the central hole, whereas smaller particles are rejected. Besides, efficient separation of particles with similar acoustic properties such as polyethylene, polystyrene and acrylic particles of the same size is also demonstrated. PMID:28252033

  13. Acoustophoretic separation of airborne millimeter-size particles by a Fresnel lens

    NASA Astrophysics Data System (ADS)

    Cicek, Ahmet; Korozlu, Nurettin; Adem Kaya, Olgun; Ulug, Bulent

    2017-03-01

    We numerically demonstrate acoustophoretic separation of spherical solid particles in air by means of an acoustic Fresnel lens. Beside gravitational and drag forces, freely-falling millimeter-size particles experience large acoustic radiation forces around the focus of the lens, where interplay of forces lead to differentiation of particle trajectories with respect to either size or material properties. Due to the strong acoustic field at the focus, radiation force can divert particles with source intensities significantly smaller than those required for acoustic levitation in a standing field. When the lens is designed to have a focal length of 100 mm at 25 kHz, finite-element method simulations reveal a sharp focus with a full-width at half-maximum of 0.5 wavelenghts and a field enhancement of 18 dB. Through numerical calculation of forces and simulation of particle trajectories, we demonstrate size-based separation of acrylic particles at a source sound pressure level of 153 dB such that particles with diameters larger than 0.5 mm are admitted into the central hole, whereas smaller particles are rejected. Besides, efficient separation of particles with similar acoustic properties such as polyethylene, polystyrene and acrylic particles of the same size is also demonstrated.

  14. A simulation study about tracking of micro sized particles close to contact

    NASA Astrophysics Data System (ADS)

    Yücel, Harun; Okumuşoǧlu, Nazmi Turan

    2017-02-01

    The tracking of micro sized colloidal particles which are optically trapped is an important method to gain information about the pair interaction potential between particles suspended in a liquid. To track the particles which are close to contact is difficult because the overlapping of the particle diffraction patterns causes systematic errors in the position detection. Recently, a template based the particle finding algorithm was reported and verified experimentally. Here, we perform simulations in order to determine the precision of that algorithm, as one cannot know the real positions of the particles in the experiment. We generate the particle images by using fitted curve to experimental data. As a result, we found that the proposed algorithm predicts correctly the positions with an isolated reference particle and it has the maximum error about 0.065 pixels (5.5nm) in the particle images.

  15. Aerosol Particle Size as a Factor in Pulmonary Toxicity

    DTIC Science & Technology

    1974-12-01

    second rCptresents rhi sical clearance b\\ muco- ciliar \\ traIS- Ix~rt to the throat for subsequent swallowing. Expeilimcntal data indicate that the anterior...particles b v macr.phages with translocation tu the ciliated airways and, (d) transfer of pxarticles to the lymphatic system including lymph nodes. Thie...can remain suspnded in air for long periods (due to viscous drag) and can undergo rapid dissolution in the body ’. From 13halen (1972). 361 AINIRL-TR

  16. Deconvolution of the particle size distribution of ProRoot MTA and MTA Angelus

    PubMed Central

    Ha, William Nguyen; Shakibaie, Fardad; Kahler, Bill; Walsh, Laurence James

    2016-01-01

    Abstract Objective Mineral trioxide aggregate (MTA) cements contain two types of particles, namely Portland cement (PC) (nominally 80% w/w) and bismuth oxide (BO) (20%). This study aims to determine the particle size distribution (PSD) of PC and BO found in MTA. Materials and methods The PSDs of ProRoot MTA (MTA-P) and MTA Angelus (MTA-A) powder were determined using laser diffraction, and compared to samples of PC (at three different particle sizes) and BO. The non-linear least squares method was used to deconvolute the PSDs into the constituents. MTA-P and MTA-A powders were also assessed with scanning electron microscopy. Results BO showed a near Gaussian distribution for particle size, with a mode distribution peak at 10.48 μm. PC samples milled to differing degrees of fineness had mode distribution peaks from 19.31 down to 4.88 μm. MTA-P had a complex PSD composed of both fine and large PC particles, with BO at an intermediate size, whereas MTA-A had only small BO particles and large PC particles. Conclusions The PSD of MTA cement products is bimodal or more complex, which has implications for understanding how particle size influences the overall properties of the material. Smaller particles may be reactive PC or unreactive radiopaque agent. Manufacturers should disclose particle size information for PC and radiopaque agents to prevent simplistic conclusions being drawn from statements of average particle size for MTA materials. PMID:27335899

  17. The Isolation of DNA by Polycharged Magnetic Particles: An Analysis of the Interaction by Zeta Potential and Particle Size

    PubMed Central

    Haddad, Yazan; Xhaxhiu, Kledi; Kopel, Pavel; Hynek, David; Zitka, Ondrej; Adam, Vojtech

    2016-01-01

    Magnetic isolation of biological targets is in major demand in the biotechnology industry today. This study considers the interaction of four surface-modified magnetic micro- and nanoparticles with selected DNA fragments. Different surface modifications of nanomaghemite precursors were investigated: MAN37 (silica-coated), MAN127 (polyvinylpyrrolidone-coated), MAN158 (phosphate-coated), and MAN164 (tripolyphosphate-coated). All particles were positive polycharged agglomerated monodispersed systems. Mean particle sizes were 0.48, 2.97, 2.93, and 3.67 μm for MAN37, MAN127, MAN164, and MAN158, respectively. DNA fragments exhibited negative zeta potential of −0.22 mV under binding conditions (high ionic strength, low pH, and dehydration). A decrease in zeta potential of particles upon exposure to DNA was observed with exception of MAN158 particles. The measured particle size of MAN164 particles increased by nearly twofold upon exposure to DNA. Quantitative PCR isolation of DNA with a high retrieval rate was observed by magnetic particles MAN127 and MAN164. Interaction between polycharged magnetic particles and DNA is mediated by various binding mechanisms such as hydrophobic and electrostatic interactions. Future development of DNA isolation technology requires an understanding of the physical and biochemical conditions of this process. PMID:27104527

  18. The Isolation of DNA by Polycharged Magnetic Particles: An Analysis of the Interaction by Zeta Potential and Particle Size.

    PubMed

    Haddad, Yazan; Xhaxhiu, Kledi; Kopel, Pavel; Hynek, David; Zitka, Ondrej; Adam, Vojtech

    2016-04-20

    Magnetic isolation of biological targets is in major demand in the biotechnology industry today. This study considers the interaction of four surface-modified magnetic micro- and nanoparticles with selected DNA fragments. Different surface modifications of nanomaghemite precursors were investigated: MAN37 (silica-coated), MAN127 (polyvinylpyrrolidone-coated), MAN158 (phosphate-coated), and MAN164 (tripolyphosphate-coated). All particles were positive polycharged agglomerated monodispersed systems. Mean particle sizes were 0.48, 2.97, 2.93, and 3.67 μm for MAN37, MAN127, MAN164, and MAN158, respectively. DNA fragments exhibited negative zeta potential of -0.22 mV under binding conditions (high ionic strength, low pH, and dehydration). A decrease in zeta potential of particles upon exposure to DNA was observed with exception of MAN158 particles. The measured particle size of MAN164 particles increased by nearly twofold upon exposure to DNA. Quantitative PCR isolation of DNA with a high retrieval rate was observed by magnetic particles MAN127 and MAN164. Interaction between polycharged magnetic particles and DNA is mediated by various binding mechanisms such as hydrophobic and electrostatic interactions. Future development of DNA isolation technology requires an understanding of the physical and biochemical conditions of this process.

  19. Particle size and surface area distributions of pharmaceutical powders by microcomputerized mercury porosimetry.

    PubMed

    Carli, F; Motta, A

    1984-02-01

    The Mayer-Stowe theory was applied to derive the particle size distribution of powders of pharmaceutical interest using mercury porosimetry. Particle size data obtained by this approach are fairly comparable with data derived by other, more popular, techniques such as the electrical sensing zone or the air jet sieving methods provided that the experimental value of the mercury-powder contact angle and the state of aggregation of the powder are carefully studied. Furthermore, by applying the Rootare-Prenzlow method a surface area distribution can also be derived from the same porosimetry data used to obtain the particle size distribution. All experiments were carried out with a microcomputerized mercury porosimeter, which allows storage of data during the analysis and a subsequent fast elaboration at the end of the run, with fully printed data on pore size, pore volume, surface area, and particle size of the powder sample.

  20. Particle size analysis of sediments, soils and related particulate materials for forensic purposes using laser granulometry.

    PubMed

    Pye, Kenneth; Blott, Simon J

    2004-08-11

    Particle size is a fundamental property of any sediment, soil or dust deposit which can provide important clues to nature and provenance. For forensic work, the particle size distribution of sometimes very small samples requires precise determination using a rapid and reliable method with a high resolution. The Coulter trade mark LS230 laser granulometer offers rapid and accurate sizing of particles in the range 0.04-2000 microm for a variety of sample types, including soils, unconsolidated sediments, dusts, powders and other particulate materials. Reliable results are possible for sample weights of just 50 mg. Discrimination between samples is performed on the basis of the shape of the particle size curves and statistical measures of the size distributions. In routine forensic work laser granulometry data can rarely be used in isolation and should be considered in combination with results from other techniques to reach an overall conclusion.

  1. Particle sizing by weighted measurements of scattered light

    NASA Technical Reports Server (NTRS)

    Buchele, Donald R.

    1988-01-01

    A description is given of a measurement method, applicable to a poly-dispersion of particles, in which the intensity of scattered light at any angle is weighted by a factor proportional to that angle. Determination is then made of four angles at which the weighted intensity is four fractions of the maximum intensity. These yield four characteristic diameters, i.e., the diameters of the volume/area mean (D sub 32 the Sauter mean) and the volume/diameter mean (D sub 31); the diameters at cumulative volume fractions of 0.5 (D sub v0.5 the volume median) and 0.75 (D sub v0.75). They also yield the volume dispersion of diameters. Mie scattering computations show that an average diameter less than three micrometers cannot be accurately measured. The results are relatively insensitive to extraneous background light and to the nature of the diameter distribution. Also described is an experimental method of verifying the conclusions by using two microscopic slides coated with polystyrene microspheres to simulate the particles and the background.

  2. Ultrafine particle size distributions near freeways: Effects of differing wind directions on exposure

    NASA Astrophysics Data System (ADS)

    Kozawa, Kathleen H.; Winer, Arthur M.; Fruin, Scott A.

    2012-12-01

    High ambient ultrafine particle (UFP) concentrations may play an important role in the adverse health effects associated with living near busy roadways. However, UFP size distributions change rapidly as vehicle emissions dilute and age. These size changes can influence UFP lung deposition rates and dose because deposition in the respiratory system is a strong function of particle size. Few studies to date have measured and characterized changes in near-road UFP size distributions in real-time, thus missing transient variations in size distribution due to short-term fluctuations in wind speed, direction, or particle dynamics. In this study we measured important wind direction effects on near-freeway UFP size distributions and gradients using a mobile platform with 5-s time resolution. Compared to more commonly measured perpendicular (downwind) conditions, parallel wind conditions appeared to promote formation of broader and larger size distributions of roughly one-half the particle concentration. Particles during more parallel wind conditions also changed less in size with downwind distance and the fraction of lung-deposited particle number was calculated to be 15% lower than for downwind conditions, giving a combined decrease of about 60%. In addition, a multivariate analysis of several variables found meteorology, particularly wind direction and temperature, to be important in predicting UFP concentrations within 150 m of a freeway (R2 = 0.46, p = 0.014).

  3. Ultrafine particle size distributions near freeways: Effects of differing wind directions on exposure.

    PubMed

    Kozawa, Kathleen H; Winer, Arthur M; Fruin, Scott A

    2012-12-01

    High ambient ultrafine particle (UFP) concentrations may play an important role in the adverse health effects associated with living near busy roadways. However, UFP size distributions change rapidly as vehicle emissions dilute and age. These size changes can influence UFP lung deposition rates and dose because deposition in the respiratory system is a strong function of particle size. Few studies to date have measured and characterized changes in near-road UFP size distributions in real-time, thus missing transient variations in size distribution due to short-term fluctuations in wind speed, direction, or particle dynamics. In this study we measured important wind direction effects on near-freeway UFP size distributions and gradients using a mobile platform with 5-s time resolution. Compared to more commonly measured perpendicular (downwind) conditions, parallel wind conditions appeared to promote formation of broader and larger size distributions of roughly one-half the particle concentration. Particles during more parallel wind conditions also changed less in size with downwind distance and the fraction of lung-deposited particle number was calculated to be 15% lower than for downwind conditions, giving a combined decrease of about 60%. In addition, a multivariate analysis of several variables found meteorology, particularly wind direction and temperature, to be important in predicting UFP concentrations within 150 m of a freeway (R(2) = 0.46, p = 0.014).

  4. Sizing colloidal particles from their contribution to the effective refractive index: Experimental results

    NASA Astrophysics Data System (ADS)

    Sánchez-Pérez, C.; García-Valenzuela, A.; Sato-Berrú, R. Y.; Flores-Flores, J. O.; Barrera, R. G.

    2011-01-01

    In this work we assess experimentally a new methodology for sizing non-absorbing colloidal particles in situ. It requires measuring the real and imaginary part of the effective refractive index per unit volume fraction occupied by the particles. The mean size and refractive e index of the particles are determined from a suitable model for the effective refractive index of dilute colloids. We present results of experiments made with polystyrene and silica nano-particles and compare them with dynamic light scattering and electron microscopy measurements.

  5. Effect of the size of elementary soil particles on the soil moisture characteristic curve

    NASA Astrophysics Data System (ADS)

    Sudnitsyn, I. I.

    2015-07-01

    Statistical analysis of water vapor sorption by light clayey brown forest soil and its elementary particles of different diameters has revealed extremely close correlations and linear relationships between the logarithm of total soil water potential (pressure) and the water contents in the separated particle-size fractions (due to the hydration of exchangeable cations in the diffuse layer near the surface of soil solid phase), as well as between the water content of particle-size fractions and the logarithm of their diameter (due to the differences in the specific surface area and mineralogy of these particles).

  6. Particle size analysis of nanocrystals: improved analysis method.

    PubMed

    Keck, Cornelia M

    2010-05-05

    The influence of optical parameters, additional techniques (e.g. PIDS technology) and the importance of light microscopy were investigated by comparing laser diffraction data obtained via the conventional method and an optimized analysis method. Also the influence of a possible dissolution of nanocrystals during a measurement on the size result obtained was assessed in this study. The results reveal that dissolution occurs if unsaturated medium or microparticle saturated medium is used for the measurements. The dissolution is erratic and the results are not reproducible. Dissolution can be overcome by saturating the measuring medium prior to the measurement. If nanocrystals are analysed the dispersion medium should be saturated with the nanocrystals, because the solubility is higher than for coarse micro-sized drug material. The importance of using the optimized analysis method was proven by analysing 40 different nanosuspensions via the conventional versus the optimized sizing method. There was no large difference in the results obtained for the 40 nanosuspensions using the conventional method. This would have led to the conclusion, that all the 40 formulations investigated are physically stable. However, the analysis via the optimized method revealed that from 40 formulations investigated only four were physically stable. In conclusion an optimized analysis saves time and money and avoids misleading developments, because discrimination between "stable" and "unstable" can be done reliably at a very early stage of the development.

  7. Values of Particle Size Particle Density & Slurry Viscosity to use in Waste Feed Delivery Transfer System Analysis

    SciTech Connect

    JEWETT, J R

    2002-01-30

    Recommended values have been developed for particle size distribution, particle density, and slurry viscosity that maybe used in slurry flow calculations that support the design of the piping system that is being modified to deliver Hanford wastes from the underground storage tanks to the planned Waste Treatment Plant for vitrification. The objective of this document is to provide recommended values for three waste properties to be used in a planned revision of the Waste Feed Delivery Transfer System Analysis. These properties are particle size distribution (PSD), particle density, and slurry viscosity. In this document, the results of laboratory and engineering studies will be collated and summarized to provide a succinct source of physical property data for use in the hydraulic analysis of the transfer system.

  8. Estimation of particle size variations for laser speckle rheology of materials.

    PubMed

    Hajjarian, Zeinab; Nadkarni, Seemantini K

    2015-03-01

    Laser speckle rheology (LSR) is an optical technique for assessing the viscoelastic properties of materials with several industrial, biological, and medical applications. In LSR, the viscoelastic modulus, G*(ω), of a material is quantified by analyzing the temporal fluctuations of speckle patterns. However, the size of scattering particles within the material also influences the rate of speckle fluctuations, independent of sample mechanical properties, and complicates the accurate estimation of G*(ω). Here, we demonstrate that the average particle size may be retrieved from the azimuth-angle dependence of time-averaged speckle intensities, permitting the accurate quantification of the viscoelastic moduli of materials with unknown particle size distribution using LSR.

  9. Influence of burning of fireworks on particle size distribution of PM10 and associated barium at Nagpur.

    PubMed

    Khaparde, Vaishali V; Pipalatkar, Pradeep P; Pustode, Tushar; Rao, C V Chalapati; Gajghate, Daulat G

    2012-01-01

    Influence of burning of fireworks on particle size distribution of PM(10) and associated barium (Ba) were studied at a congested residential cum commercial area of Nagpur city, India. Sampling was carried out by cascade impactor having 50% cut-off aerodynamic diameters of <10, 9, 5.8, 4.7, 3.3, 2.1, 1.1, 0.7, and <0.4 μm, 2 days before diwali, during diwali, celebrations of marriage functions, and New Year's Eve. Noticeably, increased levels of PM(10) and Ba were observed during diwali as compared to days before diwali and other activities. PM(10) levels were increased by four to nine times whereas Ba levels were increased by eight to 20 times higher in alveolar region, when compared with the levels observed before diwali. Probability of deposition of Ba mass in alveolar region varied between 14 and 27 ng/h with higher deposition when the burning of fireworks activity was lower near the site. Trimodal distribution of Ba was observed on the first 2 days of diwali at 0.4-2.1, 2.1-4.7, and 4.7 to less than PM(10) micrometer range. While on the third day, it appeared bimodal with 70% contribution in coarse fraction whereas on the fourth day, distribution appeared unimodal with 66% contribution in alveolar region (<0.4-1.1 μm). Distribution of Ba varied with respect to particle size, in accordance with the intensity of the fireworks used on different days and distance between the burning of firecrackers from the monitoring site.

  10. Values of Particle Size, Particle Density & Slurry Viscosity to use in Waste Feed Delivery Transfer System Analysis

    SciTech Connect

    JEWETT, J R

    2002-03-14

    The objective of this document is to provide recommended values for three waste properties to be used in a planned revision of the Waste Feed Delivery Transfer System Analysis (Julyk et al. 2001). These properties are particle size distribution (PSD), particle density, and slurry viscosity. In this document, the results of laboratory and engineering studies will be collated and summarized to provide a succinct source of physical property data for use in the hydraulic analysis of the transfer system.

  11. Systems and methods of varying charged particle beam spot size

    SciTech Connect

    Chen, Yu-Jiuan

    2014-09-02

    Methods and devices enable shaping of a charged particle beam. A modified dielectric wall accelerator includes a high gradient lens section and a main section. The high gradient lens section can be dynamically adjusted to establish the desired electric fields to minimize undesirable transverse defocusing fields at the entrance to the dielectric wall accelerator. Once a baseline setting with desirable output beam characteristic is established, the output beam can be dynamically modified to vary the output beam characteristics. The output beam can be modified by slightly adjusting the electric fields established across different sections of the modified dielectric wall accelerator. Additional control over the shape of the output beam can be excreted by introducing intentional timing de-synchronization offsets and producing an injected beam that is not fully matched to the entrance of the modified dielectric accelerator.

  12. Particle size distribution of ambient aerosols in an industrial area.

    PubMed

    Rao, B Padma; Srivastava, A; Yasmin, F; Ray, S; Gupta, N; Chauhan, C; Rao, C V C; Wate, S R

    2012-05-01

    Aerosol samples of PM(10) and PM(2.5) were collected from 38 sampling locations in and around the industrial area. The 24 h average mass concentration of PM(10) and PM(2.5) was 137.5 and 61.5 μg/m(3) respectively during summer, 122 and 97.5 μg/m(3) respectively in winter and 70 and 54 μg/m(3) respectively during post monsoon season. The relative contribution of coarse, fine and ultrafine particle to ambient air was analyzed for its temporal and seasonal variability in an industrialized area. This paper aims to establish baseline between PM(10) and PM(2.5) mass concentration levels.

  13. Comparison of calculated sulfate scattering efficiencies as estimated from size-resolved particle measurements at three national locations

    NASA Astrophysics Data System (ADS)

    Malm, William C.; Pitchford, Marc L.

    Size distributions and resulting optical properties of sulfur aerosols were investigated at three national parks by a Davis Rotating-drum Universal-size-cut Monitoring (DRUM) impactor. Sulfur size distribution measurements for 88, 177, and 315 consecutive time periods were made at Grand Canyon National Park during January and February 1988, Meadview, AZ during July, August, and September 1992, and at Shenandoah National Park during summer, 1990, respectively. The DRUM impactor is designed to collect aerosols with an aerodynamic diameter between 0.07 and 15.0 μm in eight size ranges. Focused beam particle-induced X-ray emission (PIXE) analysis of the aerosol deposits produces a time history of size-resolved elemental composition of varied temporal resolution. As part of the quality assurance protocol, an interagency monitoring of protected visual environments (IMPROVE) channel A sampler collecting 0-2.5 μm diameter particles was operated simultaneously alongside the DRUM sampler. During these sampling periods, the average sulfur mass, interpreted as ammonium sulfate, is 0.49, 2.30, and 10.36 μg m -3 at Grand Canyon, Meadview, and Shenandoah, respectively. The five drum stages were "inverted" using the Twomey (1975) scheme to give 486 size distributions, each made up of 72 discreet pairs of d C/dlog( D) and diameter ( D). From these distributions mass mean diameters ( Dg), geometric standard deviations ( σg), and mass scattering efficiencies ( em)) were calculated. The geometric mass mean diameters in ascending order were 0.21 μm at Meadview, 0.32 μm at Grand Canyon, and 0.42 μm at Shenandoah corresponding σg were 2.1, 2.3, and 1.9. Mie theory mass scattering efficiencies calculated from d C/dlog( D) distributions for the three locations were 2.05, 2.59, and 3.81 m 2 g -1, respectively. At Shenandoah, mass scattering efficiencies approached five but only when the mass median diameters were approximately 0.4 μm and σg were about 1.5. σg near 1.5 were

  14. An optical particle size spectrometer for aircraft-borne measurements in IAGOS-CARIBIC

    NASA Astrophysics Data System (ADS)

    Hermann, Markus; Weigelt, Andreas; Assmann, Denise; Pfeifer, Sascha; Muller, Thomas; Conrath, Thomas; Voigtlander, Jens; Heintzenberg, Jost; Wiedensohler, Alfred; Martinsson, Bengt G.; Deshler, Terry; Brenninkmeijer, Carl A. M.; Zahn, Andreas

    2016-05-01

    The particle number size distribution is an important parameter to characterize the atmospheric aerosol and its influence on the Earth's climate. Here we describe a new optical particle size spectrometer (OPSS) for measurements of the accumulation mode particle number size distribution in the tropopause region on board a passenger aircraft (IAGOS-CARIBIC observatory: In-service Aircraft for a Global Observing System - Civil Aircraft for Regular Investigation of the Atmosphere Based on an Instrument Container). A modified KS93 particle sensor from RION Co., Ltd., together with a new airflow system and a dedicated data acquisition system, is the key component of the CARIBIC OPSS. The instrument records individual particle pulse signal curves in the particle size range 130-1110 nm diameter (for a particle refractive index of 1.47-i0.006) together with a time stamp and thus allows the post-flight choice of the time resolution and the size distribution bin width. The CARIBIC OPSS has a 50 % particle detection diameter of 152 nm and a maximum asymptotic counting efficiency of 98 %. The instrument's measurement performance shows no pressure dependency and no particle coincidence for free tropospheric conditions. The size response function of the CARIBIC OPSS was obtained by a polystyrene latex calibration in combination with model calculations. Particle number size distributions measured with the new OPSS in the lowermost stratosphere agreed within a factor of 2 in concentration with balloon-borne measurements over western North America. Since June 2010 the CARIBIC OPSS is deployed once per month in the IAGOS-CARIBIC observatory.

  15. Sizing of irregular particles using a near backscattered laser Doppler system

    SciTech Connect

    Wu Xuecheng; Grehan, Gerard; Cen, Kefa; Ren, Kuan Fang; Wang Qinhui; Luo Zhongyang; Fang Mengxiang

    2007-12-20

    A near backscattered laser Doppler system was presented to carry out velocity and size distribution measurements for irregular particles in two-phase flows. The technique uses amplitudes of particles Doppler signals to estimate the particle size distribution in a statistical manner. Holve's numerical inversion scheme is employed to unfold the dependence of the scattered signals on both particle trajectory and orientation through the measurement volume. The performance and error level of the technique were simulated, and several parameters including the number of particle samples, the fluctuation of irregular particle response function, inversion algorithms, and types of particle size distribution were extensively investigated. The results show that the size distributions for those irregular particles even with strong fluctuations in response function can be successfully reconstructed with an acceptable error level using a Phillips-Twomey-non-negative least-squares algorithm instead of a non-negative least-squares one. The measurement system was then further experimentally verified with irregular quartz sands. Using inversion matrix obtained from the calibration experiment, the average measurement error for the mixing quartz sands with a size range of 200-560 {mu}m are found to be about 23.3%, which shows the reliability of the technique and the potential for it to be applied to industrial measurement.

  16. Ion size effects on the electrokinetics of spherical particles in salt-free concentrated suspensions

    NASA Astrophysics Data System (ADS)

    Roa, Rafael; Carrique, Felix; Ruiz-Reina, Emilio

    2012-02-01

    In this work we study the influence of the counterion size on the electrophoretic mobility and on the dynamic mobility of a suspended spherical particle in a salt-free concentrated colloidal suspension. Salt-free suspensions contain charged particles and the added counterions that counterbalance their surface charge. A spherical cell model approach is used to take into account particle-particle electro-hydrodynamic interactions in concentrated suspensions. The finite size of the counterions is considered including an entropic contribution, related with the excluded volume of the ions, in the free energy of the suspension, giving rise to a modified counterion concentration profile. We are interested in studying the linear response of the system to an electric field, thus we solve the different electrokinetic equations by using a linear perturbation scheme. We find that the ionic size effect is quite important for moderate to high particles charges at a given particle volume fraction. In addition for such particle surface charges, both the electrophoretic mobility and the dynamic mobility suffer more important changes the larger the particle volume fraction for each ion size. The latter effects are more relevant the larger the ionic size.

  17. [Particle Size and Number Density Online Analysis for Particle Suspension with Polarization-Differentiation Elastic Light Scattering Spectroscopy].

    PubMed

    Chen, Wei-kang; Fang, Hui

    2016-03-01

    The basic principle of polarization-differentiation elastic light scattering spectroscopy based techniques is that under the linear polarized light incidence, the singlely scattered light from the superficial biological tissue and diffusively scattered light from the deep tissue can be separated according to the difference of polarization characteristics. The novel point of the paper is to apply this method to the detection of particle suspension and, to realize the simultaneous measurement of its particle size and number density in its natural status. We design and build a coaxial cage optical system, and measure the backscatter signal at a specified angle from a polystyrene microsphere suspension. By controlling the polarization direction of incident light with a linear polarizer and adjusting the polarization direction of collected light with another linear polarizer, we obtain the parallel polarized elastic light scattering spectrum and cross polarized elastic light scattering spectrum. The difference between the two is the differential polarized elastic light scattering spectrum which include only the single scattering information of the particles. We thus compare this spectrum to the Mie scattering calculation and extract the particle size. We then also analyze the cross polarized elastic light scattering spectrum by applying the particle size already extracted. The analysis is based on the approximate expressions taking account of light diffusing, from which we are able to obtain the number density of the particle suspension. We compare our experimental outcomes with the manufacturer-provided values and further analyze the influence of the particle diameter standard deviation on the number density extraction, by which we finally verify the experimental method. The potential applications of the method include the on-line particle quality monitoring for particle manufacture as well as the fat and protein density detection of milk products.

  18. Role of relative size of asperities and adhering particles on the adhesion force.

    PubMed

    Kumar, Aditya; Staedler, Thorsten; Jiang, Xin

    2013-11-01

    Adhesion force between silica microspheres of different sizes and different rough surfaces (silicon and diamond like carbon) has been measured with an atomic force microscope (AFM). Surface roughness, asperity geometry, and size of adhering particles play an important role in determining the adhesion force. Adhesion force linearly increases with size of adhering particle for smooth surfaces and can be described by the JRK model. Adhesion force of adhering particle bigger than in size to the asperities decreases with surface roughness and can be described by the Rabinovich model. For the particles smaller than or similar in size to the asperities, the adhesion force increases with surface roughness. In later case, the interaction of adhering particles with valley portion of asperities is dominated and the contact area increases. On the basis of Rabinovich model, a new equation, which takes the relative size of adhering particles and asperities into account, is derived and compared with experimental results. The normalized adhesion force decreases with ratio of root-mean-square (rms) roughness to radius of adhering particle up to 0.0025, followed by increasing normalized adhesion forces.

  19. Effect of particle size on oral absorption of carvedilol nanosuspensions: in vitro and in vivo evaluation

    PubMed Central

    Liu, Dandan; Pan, Hao; He, Fengwei; Wang, Xiaoyu; Li, Jinyu; Yang, Xinggang; Pan, Weisan

    2015-01-01

    The purpose of this work was to explore the particle size reduction effect of carvedilol on dissolution and absorption. Three suspensions containing different sized particles were prepared by antisolvent precipitation method or in combination with an ultrasonication process. The suspensions were characterized for particle size, surface morphology, and crystalline state. The crystalline form of carvedilol was changed into amorphous form after antisolvent precipitation. The dissolution rate of carvedilol was significantly accelerated by a reduction in particle size. The intestinal absorption of carvedilol nanosuspensions was greatly improved in comparison with microsuspensions and solution in the in situ single-pass perfusion experiment. The in vivo evaluation demonstrated that carvedilol nanosuspensions and microsuspensions exhibited markedly increased Cmax (2.09- and 1.48-fold) and AUC0−t (2.11- and 1.51-fold), and decreased Tmax (0.34- and 0.48-fold) in contrast with carvedilol coarse suspensions. Moreover, carvedilol nanosuspensions showed good biocompatibility with the rat gastric mucosa in in vivo gastrointestinal irritation test. The entire results implicated that the dissolution rate and the oral absorption of carvedilol were significantly affected by the particle size. Particle size reduction to form nanosized particles was found to be an efficient method for improving the oral bioavailability of carvedilol. PMID:26508852

  20. Observations of the sensitivity of beam attenuation to particle size in a coastal bottom boundary layer

    NASA Astrophysics Data System (ADS)

    Hill, P. S.; Boss, E.; Newgard, J. P.; Law, B. A.; Milligan, T. G.

    2011-02-01

    The goal of this study was to test the hypothesis that the aggregated state of natural marine particles constrains the sensitivity of optical beam attenuation to particle size. An instrumented bottom tripod was deployed at the 12-m node of the Martha's Vineyard Coastal Observatory to monitor particle size distributions, particle size-versus-settling-velocity relationships, and the beam attenuation coefficient (cp) in the bottom boundary layer in September 2007. An automated in situ filtration system on the tripod collected 24 direct estimates of suspended particulate mass (SPM) during each of five deployments. On a sampling interval of 5 min, data from a Sequoia Scientific LISST 100x Type B were merged with data from a digital floc camera to generate suspended particle volume size distributions spanning diameters from approximately 2 μm to 4 cm. Diameter-dependent densities were calculated from size-versus-settling-velocity data, allowing conversion of the volume size distributions to mass distributions, which were used to estimate SPM every 5 min. Estimated SPM and measured cp from the LISST 100x were linearly correlated throughout the experiment, despite wide variations in particle size. The slope of the line, which is the ratio of cp to SPM, was 0.22 g m-2. Individual estimates of cp:SPM were between 0.2 and 0.4 g m-2 for volumetric median particle diameters ranging from 10 to 150 μm. The wide range of values in cp:SPM in the literature likely results from three factors capable of producing factor-of-two variability in the ratio: particle size, particle composition, and the finite acceptance angle of commercial beam-transmissometers.

  1. Evaluating unsupervised methods to size and classify suspended particles using digital in-line holography

    USGS Publications Warehouse

    Davies, Emlyn J.; Buscombe, Daniel D.; Graham, George W.; Nimmo-Smith, W. Alex M.

    2015-01-01

    Substantial information can be gained from digital in-line holography of marine particles, eliminating depth-of-field and focusing errors associated w