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1
Pan, Lei, Sean Golden, Shoeleh Assemi, Marc Freddy Sime, Xuming Wang, Yuesheng Gao und Jan Miller. „Characterization of Particle Size and Composition of Respirable Coal Mine Dust“. Minerals 11, Nr. 3 (08.03.2021): 276. http://dx.doi.org/10.3390/min11030276.
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Respirable coal mine dust (RCMD) particles, particularly the nano-sized fraction (<1 μm) of the RCMD if present, can cause severe lung diseases in coal miners. Characterization of both the particle size and chemical composition of such RCMD particles remains a work in progress, in particular, with respect to the nano-sized fraction of RCMD. In this work, various methods were surveyed and used to obtain both the size and chemical composition of RCMD particles, including scanning electron microscopy (SEM), scanning transmission electron microscopy (S-TEM), dynamic light scattering (DLS), and asymmetric flow field-flow fractionation (AsFIFFF). It was found that the micron-sized fraction (>1 μm) of RCMD particles collected at the miner location, from an underground coal mine, contained more coal particles, while those collected at the bolter location contained more rock dust particles. Two image processing procedures were developed to determine the size of individual RCMD particles. The particle size distribution (PSD) results showed that a significant amount (~80% by number) of nano-sized particles were present in the RCMD sample collected in an underground coal mine. The presence of nano-sized RCMD particles was confirmed by bulk sample analysis, using both DLS and AsFIFFF. The mode particle size at the peak frequency of the size distribution was found to be 300–400 nm, which was consistent with the result obtained from SEM analysis. The chemical composition data of the nano-sized RCMD showed that not only diesel particles, but also both coal and rock dust particles were present in the nano-sized fraction of the RCMD. The presence of the nano-sized fraction of RCMD particles may be site and location dependent, and a detailed analysis of the entire size range of RCMD particles in different underground coal mines is needed.
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Kontkanen, Jenni, Chenjuan Deng, Yueyun Fu, Lubna Dada, Ying Zhou, Jing Cai, Kaspar R. Daellenbach et al. „Size-resolved particle number emissions in Beijing determined from measured particle size distributions“. Atmospheric Chemistry and Physics 20, Nr. 19 (05.10.2020): 11329–48. http://dx.doi.org/10.5194/acp-20-11329-2020.
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Abstract. The climate and air quality effects of aerosol particles depend on the number and size of the particles. In urban environments, a large fraction of aerosol particles originates from anthropogenic emissions. To evaluate the effects of different pollution sources on air quality, knowledge of size distributions of particle number emissions is needed. Here we introduce a novel method for determining size-resolved particle number emissions, based on measured particle size distributions. We apply our method to data measured in Beijing, China, to determine the number size distribution of emitted particles in a diameter range from 2 to 1000 nm. The observed particle number emissions are dominated by emissions of particles smaller than 30 nm. Our results suggest that traffic is the major source of particle number emissions with the highest emissions observed for particles around 10 nm during rush hours. At sizes below 6 nm, clustering of atmospheric vapors contributes to calculated emissions. The comparison between our calculated emissions and those estimated with an integrated assessment model GAINS (Greenhouse Gas and Air Pollution Interactions and Synergies) shows that our method yields clearly higher particle emissions at sizes below 60 nm, but at sizes above that the two methods agree well. Overall, our method is proven to be a useful tool for gaining new knowledge of the size distributions of particle number emissions in urban environments and for validating emission inventories and models. In the future, the method will be developed by modeling the transport of particles from different sources to obtain more accurate estimates of particle number emissions.
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Friedman, B., A. Zelenyuk, J. Beránek, G. Kulkarni, M. Pekour, A. G. Hallar, I. B. McCubbin, J. A. Thornton und D. J. Cziczo. „Aerosol measurements at a high elevation site: composition, size, and cloud condensation nuclei activity“. Atmospheric Chemistry and Physics Discussions 13, Nr. 7 (09.07.2013): 18277–306. http://dx.doi.org/10.5194/acpd-13-18277-2013.
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Abstract. Measurements of cloud condensation nuclei (CCN) concentrations, single particle composition and size distributions at a high-elevation research site from March 2011 are presented. The temporal evolution of detailed single particle composition is compared with changes in CCN activation on four days, two of which include new particle formation and growth events. Sulfate-containing particles dominated the single particle composition by number; biomass burning particles, sea salt particles, and particles containing organic components also were present. CCN activation largely followed the behavior of the sulfate-containing particle types; biomass burning particle types also likely contained hygroscopic material that impacted CCN activation. Newly formed particles also may contribute to CCN activation at higher supersaturation conditions. Derived aerosol hygroscopicity parameters from the size distribution and CCN concentration measurements are within the range of previous reports of remote continental kappa values.
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Friedman, B., A. Zelenyuk, J. Beranek, G. Kulkarni, M. Pekour, A. Gannet Hallar, I. B. McCubbin, J. A. Thornton und D. J. Cziczo. „Aerosol measurements at a high-elevation site: composition, size, and cloud condensation nuclei activity“. Atmospheric Chemistry and Physics 13, Nr. 23 (09.12.2013): 11839–51. http://dx.doi.org/10.5194/acp-13-11839-2013.
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Abstract. Measurements of cloud condensation nuclei (CCN) concentrations, single particle composition and size distributions at a high-elevation research site from March 2011 are presented. The temporal evolution of detailed single particle composition is compared with changes in CCN activation on four days, two of which include new particle formation and growth events. Sulfate-containing particles dominated the single particle composition by number; biomass burning particles, sea salt particles, and particles containing organic components were also present. CCN activation largely followed the behavior of the sulfate-containing particle types; biomass burning particle types also likely contained hygroscopic material that impacted CCN activation. Newly formed particles also may contribute to CCN activation at higher supersaturation conditions. Derived aerosol hygroscopicity parameters from the size distribution and CCN concentration measurements are within the range of previous reports of remote continental kappa values.
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Davies, P., und J. Popplewell. „Particle size analysis of micrometre-sized particles using magnetic liquids“. Journal of Physics D: Applied Physics 20, Nr. 11 (14.11.1987): 1540–41. http://dx.doi.org/10.1088/0022-3727/20/11/028.
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Zhang, Lin, Guang Hui Min, Hua Shun Yu, Hong Mei Chen und Gang Feng. „The Size and Morphology of Fine CaB6 Powder Synthesized by Nanometer CaCO3 as Reactant“. Key Engineering Materials 326-328 (Dezember 2006): 369–72. http://dx.doi.org/10.4028/www.scientific.net/kem.326-328.369.
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Based on the CaCO3-B4C-C system to prepare calcium hexaboride (CaB6) powder, the influence of B4C size on the CaB6 powder was investigated in this paper, in which micro-sized B4C in various size and nano-sized CaCO3 were as main raw materials. XRD and SEM were used to characterize the phase pattern, size and morphology of CaB6 powder particles respectively. Laser particle size analyzer was employed to determine the size distribution of CaB6 particles. It was found that the size of B4C had a dominant effect on the size and distribution of CaB6 powder particles. When B4C particles were much coarser than CaCO3, the CaB6 synthesized appeared as aggregates which size relied on B4C, however, the size of every CaB6 particle was determined by CaCO3. When B4C particles size was fine to several microns, the CaB6 particles synthesized were dispersive and the size of them has great relation to B4C. Synthesis models were also established to describe various reaction processes.
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Rastello, Marie, Fabrice Rastello, Hervé Bellot, Frédéric Ousset, François Dufour und Lorenz Meier. „Size of snow particles in a powder-snow avalanche“. Journal of Glaciology 57, Nr. 201 (2011): 151–56. http://dx.doi.org/10.3189/002214311795306637.
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AbstractLittle quantitative information is available concerning the size of ice particles in the turbulent clouds of powder-snow avalanches. To quantify particle size distributions, we have developed an experimental device that collects particles in real-scale powder avalanches. The device was placed on the concrete bunker of the Swiss Vallée de la Sionne avalanche dynamics test site. On 31 January 2003, a large powder-snow avalanche struck the bunker and we were able to collect particle samples. The collected particles have been photographed and the pictures digitized. An image analysis tool allows us to determine an equivalent particle radius. The captured particles have a geometric mean of 0.16 mm; the largest particles were 0.8 mm in size and the smallest particles 0.03 mm.
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Chatain, Mélodie, Raphaël Alvarez, Aurélien Ustache, Emmanuel Rivière, Olivier Favez und Cyril Pallares. „Simultaneous Roadside and Urban Background Measurements of Submicron Aerosol Number Concentration and Size Distribution (in the Range 20–800 nm), along with Chemical Composition in Strasbourg, France“. Atmosphere 12, Nr. 1 (06.01.2021): 71. http://dx.doi.org/10.3390/atmos12010071.
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The adverse health impact of particles and ultrafine particles (UFP) is proven, highlighting the need of measuring the particle number concentration (PNC) dominated by UFP. So far, PNC had never been measured in the Strasbourg urban area (France). The present study on particle size distribution and PNC measurements by an UFP-3031 analyzer was conducted during winter 2019 on a background and a roadside multi-instrumented sites (Black Carbon, chemical speciation, particulate matter 10 μm or less in diameter—PM10 mass). This paper shows significantly higher particle number concentrations of particles below 100 nm at the traffic site compared to the background site. The presence of a road axis thus mainly influences UFP, contrary to larger particles whose levels are more homogeneous over the agglomeration. During the measurement period, the nature of the particles (particle size contribution and chemical composition) was different between periods of high PM10 mass concentrations and periods of high PNC. High PM10 mass concentrations were associated with a high contribution of particles larger than 100 nm but they did not show specific chemical signature. On the other hand, during the periods with high PNC, the chemical composition was modified with an increase of the primary carbonaceous fraction compared to the periods with low PNC, but there was then no clear change in size distribution. Overall, this study illustrates that PM10 mass concentrations were barely representative of UFP and PNC variations, confirming that the monitoring of the latter metrics is necessary to better evaluate the particles toxicity, knowing that this toxicity also depends on the particle’s chemical composition.
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Rajkovic, V., D. Bozic, M. Popovic und M. T. Jovanovic. „The influence of powder particle size on properties of Cu-Al2O3 composites“. Science of Sintering 41, Nr. 2 (2009): 185–92. http://dx.doi.org/10.2298/sos0902185r.
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Inert gas atomized prealloyed copper powder containing 2 wt.% Al (average particle size ? 30 ?m) and a mixture consisting of copper (average particle sizes ? 15 ?m and 30 ?m) and 4 wt.% of commercial Al2O3 powder particles (average particle size ? 0.75 ?m) were milled separately in a high-energy planetary ball mill up to 20 h in air. Milling was performed in order to strengthen the copper matrix by grain size refinement and Al2O3 particles. Milling in air of prealloyed copper powder promoted formation of finely dispersed nano-sized Al2O3 particles by internal oxidation. On the other side, composite powders with commercial micro-sized Al2O3 particles were obtained by mechanical alloying. Following milling, powders were treated in hydrogen at 400 0C for 1h in order to eliminate copper oxides formed on their surface during milling. Hot-pressing (800 0C for 3 h in argon at pressure of 35 MPa) was used for compaction of milled powders. Hot-pressed composite compacts processed from 5 and 20 h milled powders were additionally subjected to high temperature exposure (800?C for 1 and 5h in argon) in order to examine their thermal stability. The results were discussed in terms of the effects of different size of starting powders, the grain size refinement and different size of Al2O3 particles on strengthening, thermal stability and electrical conductivity of copper-based composites.
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Reddington, C. L., K. S. Carslaw, D. V. Spracklen, M. G. Frontoso, L. Collins, J. Merikanto, A. Minikin et al. „Primary versus secondary contributions to particle number concentrations in the European boundary layer“. Atmospheric Chemistry and Physics 11, Nr. 23 (05.12.2011): 12007–36. http://dx.doi.org/10.5194/acp-11-12007-2011.
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Abstract. It is important to understand the relative contribution of primary and secondary particles to regional and global aerosol so that models can attribute aerosol radiative forcing to different sources. In large-scale models, there is considerable uncertainty associated with treatments of particle formation (nucleation) in the boundary layer (BL) and in the size distribution of emitted primary particles, leading to uncertainties in predicted cloud condensation nuclei (CCN) concentrations. Here we quantify how primary particle emissions and secondary particle formation influence size-resolved particle number concentrations in the BL using a global aerosol microphysics model and aircraft and ground site observations made during the May 2008 campaign of the European Integrated Project on Aerosol Cloud Climate Air Quality Interactions (EUCAARI). We tested four different parameterisations for BL nucleation and two assumptions for the emission size distribution of anthropogenic and wildfire carbonaceous particles. When we emit carbonaceous particles at small sizes (as recommended by the Aerosol Intercomparison project, AEROCOM), the spatial distributions of campaign-mean number concentrations of particles with diameter >50 nm (N50) and >100 nm (N100) were well captured by the model (R2≥0.8) and the normalised mean bias (NMB) was also small (−18% for N50 and −1% for N100). Emission of carbonaceous particles at larger sizes, which we consider to be more realistic for low spatial resolution global models, results in equally good correlation but larger bias (R2≥0.8, NMB = −52% and −29%), which could be partly but not entirely compensated by BL nucleation. Within the uncertainty of the observations and accounting for the uncertainty in the size of emitted primary particles, BL nucleation makes a statistically significant contribution to CCN-sized particles at less than a quarter of the ground sites. Our results show that a major source of uncertainty in CCN-sized particles in polluted European air is the emitted size of primary carbonaceous particles. New information is required not just from direct observations, but also to determine the "effective emission size" and composition of primary particles appropriate for different resolution models.
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PORTELLA, F. J., L. J. CASTON und S. LEESON. „APPARENT FEED PARTICLE SIZE PREFERENCE BY BROILERS“. Canadian Journal of Animal Science 68, Nr. 3 (01.09.1988): 923–30. http://dx.doi.org/10.4141/cjas88-102.
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Broiler chicks of different ages were used to study particle size disappearance and the effect of particle size on feed intake. The disappearance of particles larger than 1.18 mm was obvious at all ages. However, it was noticed that at 8 and 16 d disappearance of particles between > 1.18 mm and < 2.36 mm was most pronounced. As birds became older, disappearance rate was greatest for particles > 2.36 mm. Throughout a 24-h period, particle breakdown was noted. Birds did eat these smaller particles at the end of a 24-h period, especially when the concentration of large particles was reduced. Chemical analysis revealed that birds selected material on the basis of particle size, since nutrient composition of the diet and of different diet fractions did not change throughout the day. Changing particle size abruptly from crumbles to pellets did not adversely affect overall feed consumption (P > 0.05) or bird performance. Key words: Broiler, particle size preference, crumbles, pellets
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Kaatz, F. H., G. M. Chow und A. S. Edelstein. „Narrowing sputtered nanoparticle size distributions“. Journal of Materials Research 8, Nr. 5 (Mai 1993): 995–1000. http://dx.doi.org/10.1557/jmr.1993.0995.
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By adjusting the sputtering rate and gas pressure, it is possible to form nanoparticles of different sizes, phases, and materials. We have investigated the spatial distribution of sputtered particle formation using a vertical, linear arrangement of substrates. Collecting the particles soon after they are formed, before they have time to grow and agglomerate, allows one to obtain a narrow size distribution. In the case of molybdenum, a narrow distribution of cubic particles is formed at relatively large distances (8 cm) from the source. These cubic particles collide and self-assemble in the vapor into arrays of larger cubic particles. The particle size histograms are fitted to lognormal distribution functions. How supersaturation occurs is discussed qualitatively as a function of the distance from the substrate, sputtering rate, and the mean free path in the vapor. This method of nanocrystalline particle formation has potential use in magnetic and opto-electronic (quantum dot) applications, where a narrow size distribution is required.
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Pang, Wei Qiang, Xiao Bing Shi und Yang Li. „Preparation, Characterization of Co3O4 Nano-Particles and its Catalytic Effect on the Combustion of Fuel Rich Propellants“. Advanced Materials Research 560-561 (August 2012): 284–88. http://dx.doi.org/10.4028/www.scientific.net/amr.560-561.284.
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The mono-dispersed Co3O4 nano-particles were prepared by means of solid phase synthetical method. The particle size, specific surface area, crystal structure and morphology of the samples were characterized by laser particle size analysis, x-ray diffraction (XRD) and transmission electron microscopy (TEM), respectively. The catalytic effects of nano-particles on the combustion of fuel rich propellant were investigated. The results show that the Co3O4 nano-particles prepared are uniform and with relatively wide size distribution curve. The catalytic effect of Co3O4 nano-particles on the fuel rich propellant is stronger than those of micro-sized Co3O4 particles and CuO nano-particles.
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Volgina, Liudmila, und Anastasiia Romanova. „Hydraulic size of non-spherical solid particles“. E3S Web of Conferences 97 (2019): 05034. http://dx.doi.org/10.1051/e3sconf/20199705034.
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The paper studies impact of determining the diameter of solid particles on the calculation of the hydraulic particle size in the water flow. The relevance of the topic is also connected with the use of calculation of hydraulic size in hydraulic engineering in forecasting: downstream erosion, the formation of shoals, canals, bottom spillages, etc. Most of the empirical formulas for calculating the hydraulic particle size are applicable to spherical particles. However, the nature of the solid particles rarely has a spherical shape. The aim of this work is to investigate experimentally the dependence of the hydraulic size of the diameter of the solid particles. Different approaches to determining the diameter solid particles are analyzed, as for non-spherical particles finding the diameter is an independent and complex problem. For the experimental research solid particles of different shapes and sizes were used. The diameter is included in the empirical formulas for hydraulic size linearly, and to the power of 2 or 0.5. Therefore, the dependence of the experimental hydraulic size on the diameter was correlated with the corresponding functions. The shape of the particle significantly affects the value of the hydraulic size and depends on the diameter to the power of (0.5).
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Abe, Shigeaki, Yusaku Hamba, Nobuki Iwadera, Tsukasa Akasaka, Shuichi Yamagata, Yasutaka Yawaka, Junichiro Iida, Motohiro Uo, Tetsu Yonezawa und Fumio Watari. „Biocompatibility and Biodistribution of Several Nano-Sized Ceramics Particles“. Key Engineering Materials 529-530 (November 2012): 625–29. http://dx.doi.org/10.4028/www.scientific.net/kem.529-530.625.
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We succeeded in determination the biodistribution of several nano-sized particles administered to mice through the tail vein. After administration, these particles were observed in the lung, liver and spleen. The distribution behaviors depend upon not only chemical species but also the particles size. To estimate their cytocompatibility, these particles were exposed to osteoblastic cell at several concentrations. When the concentration reached at 10 ppm, their viability remained at 80% or more even nano-sized particle contained rare earth element. Only CuO particles indicated the viability decrease. The effect depended on the particle size. These results suggested that the chemical species played a dominant key in the biodistribution and biocompatibility of nanoparticles compared with the size-effect.
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Pfeifer, Sascha, Thomas Müller, Kay Weinhold, Nadezda Zikova, Sebastiao Martins dos Santos, Angela Marinoni, Oliver F. Bischof et al. „Intercomparison of 15 aerodynamic particle size spectrometers (APS 3321): uncertainties in particle sizing and number size distribution“. Atmospheric Measurement Techniques 9, Nr. 4 (07.04.2016): 1545–51. http://dx.doi.org/10.5194/amt-9-1545-2016.
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Abstract. 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 is needed.
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Pfeifer, S., T. Müller, K. Weinhold, N. Zikova, S. Santos, A. Marinoni, O. F. Bischof et al. „Intercomparison of 15 aerodynamic particle size spectrometers (APS 3321): uncertainties in particle sizing and number size distribution“. Atmospheric Measurement Techniques Discussions 8, Nr. 11 (03.11.2015): 11513–32. http://dx.doi.org/10.5194/amtd-8-11513-2015.
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Abstract. 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 μm is needed.
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Wang, Shu Lin, Zhao Wang, Bing Hao Li und Man Xu. „Preparation of Spherical Silica with Controllable Size“. Solid State Phenomena 281 (August 2018): 65–70. http://dx.doi.org/10.4028/www.scientific.net/ssp.281.65.
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The spherical silica particles were prepared by sol-gel method with TEOS as precursor, ethanol as solvent in the presence of ammonia. The effects of reaction temperature and the amount of ammonia and TEOS on the size and morphology of silica particles were investigated. The hydrolysis temperature , alkali and TEOS content does not affect the morphology of silica, the silica particles were spherical; With the increase of hydrolysis temperature, particle size of silica showed first increased and then decreased, when the hydrolysis temperature is 30 °C, the silica particle size up to 0.6 μm, when the hydrolysis temperature is 60 °C, the silica particle size is 0.15 μm; With the increase of the content of alkali, silica particle size showed first increased and then decreased, when the alkali content is 20 ml, the silica particle size up to 0.6 μm and when the alkali content is 10 ml, the silica particle size is 0.2 μm; With the increase of TEOS dosage, the amount of spherical silica increased and the particle size of silica spherical particles first increased and then decreased.
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ITO, YOICHI, FLORENCE NAAIM-BOUVET, KOUICHI NISHIMURA, HERVÉ BELLOT, EMMANUEL THIBERT, XAVIER RAVANAT und FIRMIN FONTAINE. „Measurement of snow particle size and velocity in avalanche powder clouds“. Journal of Glaciology 63, Nr. 238 (23.01.2017): 249–57. http://dx.doi.org/10.1017/jog.2016.130.
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ABSTRACTParticle size, particle speed and airflow speed have been measured in the powder snow clouds of avalanches to investigate the suspension and transportation processes of snow particles. The avalanches were artificially triggered at the Lautaret full-scale avalanche test-site (French Alps) where an ultrasonic anemometer and a snow particle counter were setup in an avalanche track for measurements. Relatively large particles were observed during passage of the avalanche head and then the size of the particles slightly decreased as the core of the avalanche passed the measurement station. The particle size distribution was well fitted by a gamma distribution function. A condition for suspension of particles within the cloud based on the ratio of vertical velocity fluctuation to particle settling velocity suggests that the large particles near the avalanche head are not lifted up by turbulent diffusion, but rather ejected by a process involving collisions between the avalanche flow and the rough snow surface. Particle speeds were lower than the airflow speed when large particles were present in the powder cloud.
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Ni, Zeng Lei, Ai Qin Wang und Jing Pei Xie. „Effects of Particle Size and Distribution on the Microstructure and Mechanical Properties of SiC Reinforced Al-30Si Alloy Composite“. Applied Mechanics and Materials 271-272 (Dezember 2012): 12–16. http://dx.doi.org/10.4028/www.scientific.net/amm.271-272.12.
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This paper studied the combined effects of particle size and distribution on the mechanical properties of the SiC particle reinforced Al-30Si alloy composites. The microstructure of experimental material was analyzed by SEM, the tensile strength and physical properties were examined. The results show that, with the increase of the SiC particle size in the composites, the clustering degree of the SiC particles decreases in the matrix, the SiC particles distribute more ununiformly. The tensile strength is influenced by the SiC particle size, the tensile strength of the composite reinforced by 13μm sized SiC particles is the highest.
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Denjean, C., P. Formenti, B. Picquet-Varrault, Y. Katrib, E. Pangui, P. Zapf und J. F. Doussin. „A new experimental approach to study the hygroscopic and optical properties of aerosols: application to ammonium sulfate particles“. Atmospheric Measurement Techniques 7, Nr. 1 (23.01.2014): 183–97. http://dx.doi.org/10.5194/amt-7-183-2014.
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Abstract. A new methodology for the determination of the changes due to hygroscopic growth with relative humidity of the number size distribution and optical properties of polydispersed aerosols is described. This method uses the simulation chamber CESAM where the hygroscopic properties of polydispersed aerosol particles can be investigated in situ by exposing them to RH ranging from 0 to 100% for approximately 1 h. In situ humidification is used to provide simultaneous information on the RH-dependence of the particle size and the corresponding scattering coefficient (σscat), and that for the entire size distribution. Optical closure studies, based on integrated nephelometer and aethalometer measurements, Mie scattering calculations and measured particle size distributions, can therefore be performed to yield derived parameters such as the complex refractive index (CRI) at λ = 525 nm. The CRI can also be retrieved in the visible spectrum by combining differential mobility analyzer (DMA) and white light aerosol spectrometer (Palas Welas®) measurements. We have applied this methodology to ammonium sulfate particles, which have well known optical and hygroscopic properties. The CRI obtained from the two methods (1.54–1.57) compared favourably to each other and are also in reasonable agreement with the literature values. The particle's growth was compared to values obtained for one selected size of particles (150 nm) with a H-TDMA and the effect of the residence time for particles humidification was investigated. When the humidification was performed in the chamber for a few minutes, a continuous increase of the ammonium sulfate particle's size and σscat was observed from RH values as low as 30% RH. Comparison of the measured and modelled values based on Köhler and Mie theories shows that layers of water are adsorbed on ammonium sulfate particles below the deliquescence point. In contradiction, the particle's growth reported with H-TDMAs showed a prompt deliquescence of ammonium sulfate particles with no continuous growth in size at low RH. These findings highlight the need to allow sufficient time for particle-water vapour equilibrium in investigating the aerosols hygroscopic properties. H-TDMA instruments induce limited residence time for humidification and seem to be insufficient for water adsorption on ammonium sulfate particles.
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Operti, Maria Camilla, Yusuf Dölen, Jibbe Keulen, Eric A. W. van Dinther, Carl G. Figdor und Oya Tagit. „Microfluidics-Assisted Size Tuning and Biological Evaluation of PLGA Particles“. Pharmaceutics 11, Nr. 11 (08.11.2019): 590. http://dx.doi.org/10.3390/pharmaceutics11110590.
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Polymeric particles made up of biodegradable and biocompatible polymers such as poly(lactic-co-glycolic acid) (PLGA) are promising tools for several biomedical applications including drug delivery. Particular emphasis is placed on the size and surface functionality of these systems as they are regarded as the main protagonists in dictating the particle behavior in vitro and in vivo. Current methods of manufacturing polymeric drug carriers offer a wide range of achievable particle sizes, however, they are unlikely to accurately control the size while maintaining the same production method and particle uniformity, as well as final production yield. Microfluidics technology has emerged as an efficient tool to manufacture particles in a highly controllable manner. Here, we report on tuning the size of PLGA particles at diameters ranging from sub-micron to microns using a single microfluidics device, and demonstrate how particle size influences the release characteristics, cellular uptake and in vivo clearance of these particles. Highly controlled production of PLGA particles with ~100 nm, ~200 nm, and >1000 nm diameter is achieved through modification of flow and formulation parameters. Efficiency of particle uptake by dendritic cells and myeloid-derived suppressor cells isolated from mice is strongly correlated with particle size and is most efficient for ~100 nm particles. Particles systemically administered to mice mainly accumulate in liver and ~100 nm particles are cleared slower. Our study shows the direct relation between particle size varied through microfluidics and the pharmacokinetics behavior of particles, which provides a further step towards the establishment of a customizable production process to generate tailor-made nanomedicines.
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Duan, Yu Feng, und Zhao Xia Fu. „Preparation and Characterization of Magnetic Toner Particles by Direct Polymerization Method“. Advanced Materials Research 217-218 (März 2011): 1702–7. http://dx.doi.org/10.4028/www.scientific.net/amr.217-218.1702.
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In this study a kind of black toner, containing polymer, magnetic iron oxide pigment, and several other additives, was prepared by a suspension polymerization method. The morphology, influence factor of particle size, and glass transition of prepared toner were discussed. SEM image showed that the produced micron-sized particles have a spherical surface and the various chemicals were mixed into monomers during manufacturing of the particles. Discussion about particle formation and stability concluded that the toner particle size related with stabilizer concentration, stirrer speed, and crosslinking agent concentration. The bigger particles, resulted from droplets coalescence during polymerization process, disappeared when enough PVA stabilizer was used in the aqueous medium. .Increasing the stirrer speed corresponded to the decrease of the particles size. But any increase in stirrer speed t did not contribute to size reduction in small particles below 2μm. It was found that particle size decrease with the addition of crosslinking agent. The DSC result indicated the glass transition of polymerized toner could be effectively adjusted according to Fox equation through change the monomer ratio.
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Uchiyama, Hideki. „Measurement of particle size distribution of suspended particles.“ Japan journal of water pollution research 9, Nr. 12 (1986): 763–66. http://dx.doi.org/10.2965/jswe1978.9.763.
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25
Hirosawa, Fumie, Tomohiro Iwasaki und Masashi Iwata. „Particle Impact Energy Variation with the Size and Number of Particles in a Planetary Ball Mill“. MATEC Web of Conferences 333 (2021): 02016. http://dx.doi.org/10.1051/matecconf/202133302016.
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To investigate the mechanical energy applying to the particles in a grinding process using a planetary ball mill, the impact energy of particles was estimated by simulating the behavior of the particles and grinding balls using the discrete element method (DEM) under different conditions of the size and number of particles, corresponding to their variations during milling. As the impact energy contributing to the particle breakage, we focused on the particle impact energy generated at particle-to-grinding ball/wall and particle-to-particle collisions. The particle size and the number of particles affected the level of particle impact energy at a single collision and the number of collisions of particles, respectively, resulting in an increase of the total impact energy of particles with decreasing particle size and increasing number of particles. The result suggests that milling conditions such as the size of grinding balls should be adjusted appropriately based on the variation of the size and number of particles so that the particles can receive large amounts of the impact energy during milling.
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Hirosawa, Fumie, Tomohiro Iwasaki und Masashi Iwata. „Particle Impact Energy Variation with the Size and Number of Particles in a Planetary Ball Mill“. MATEC Web of Conferences 333 (2021): 02016. http://dx.doi.org/10.1051/matecconf/202133302016.
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To investigate the mechanical energy applying to the particles in a grinding process using a planetary ball mill, the impact energy of particles was estimated by simulating the behavior of the particles and grinding balls using the discrete element method (DEM) under different conditions of the size and number of particles, corresponding to their variations during milling. As the impact energy contributing to the particle breakage, we focused on the particle impact energy generated at particle-to-grinding ball/wall and particle-to-particle collisions. The particle size and the number of particles affected the level of particle impact energy at a single collision and the number of collisions of particles, respectively, resulting in an increase of the total impact energy of particles with decreasing particle size and increasing number of particles. The result suggests that milling conditions such as the size of grinding balls should be adjusted appropriately based on the variation of the size and number of particles so that the particles can receive large amounts of the impact energy during milling.
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Kargu, Wranj, und Garren Batceor. „POWDER PARTICLE SHAPE AND SIZE DIFFERENTIATION“. International Journal Of Multidisciplinary Research And Studies 05, Nr. 02 (09.03.2022): 01–09. http://dx.doi.org/10.33826/ijmras/v05i02.4.
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The separation of particles in keeping with shape is important for improving the standard of powder products. the form of a particle significantly affects its bulk properties. Various kinds of shape separators reported up to now are reviewed during this paper to supply useful information when choosing the foremost effective one, and also the separation mechanism and features are compared. Problems within the further development of the technique are explained.
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Lian, Li, Lu Taijing, Yasushi Zaizu und T. Ogawa. „Size distribution of ultrafine particles in KDP aqueous solutions“. Journal of Materials Research 11, Nr. 2 (Februar 1996): 387–90. http://dx.doi.org/10.1557/jmr.1996.0047.
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Quantitative and qualitative investigations on the size distribution of ultrafine particles in KDP solutions were performed by a laser light scanning particle counter and by comparing with scattering polystyrene particles of standard size. The ultrafine particles are of a size distribution from <70 nm to 2000 nm, and the density of the particles sharply decreased with increasing particle size. Most of them were smaller than 100 nm, and almost no particles were >1000 nm. The size of the visual particles, which are distinguished individually by a laser light-scattering technique,3 was estimated in the size range from 200 nm to 1000 nm. The reliability of the results was evaluated.
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Prochaska, Adam B., Paul M. Santi und Jerry D. Higgins. „Relationships between size and velocity for particles within debris flows“. Canadian Geotechnical Journal 45, Nr. 12 (Dezember 2008): 1778–83. http://dx.doi.org/10.1139/t08-088.
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Estimation of the impact forces from boulders within a debris flow is important for the design of structural mitigation elements. Boulder impact force equations are most sensitive to the inputs of particle size and particle velocity. Current guidelines recommend that a design boulder should have a size equal to the depth of flow and a velocity equal to that of the flow. This study used video analysis software to investigate the velocities of different sized particles within debris flows. Particle velocity generally decreased with increasing particle size, but the rate of decrease was found to be dependent on the abilities of particles to rearrange within debris flows.
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Tkacik, Peter T., Jerry L. Dahlberg, James E. Johnson, James J. Hoth, Rebecca A. Szer und Samuel E. Hellman. „Sizing of airborne particles in an operating room“. PLOS ONE 16, Nr. 4 (05.04.2021): e0249586. http://dx.doi.org/10.1371/journal.pone.0249586.
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Medical procedures that produce aerosolized particles are under great scrutiny due to the recent concerns surrounding the COVID-19 virus and increased risk for nosocomial infections. For example, thoracostomies, tracheotomies and intubations/extubations produce aerosols that can linger in the air. The lingering time is dependent on particle size where, e.g., 500 μm (0.5 mm) particles may quickly fall to the floor, while 1 μm particles may float for extended lengths of time. Here, a method is presented to characterize the size of <40 μm to >600 μm particles resulting from surgery in an operating room (OR). The particles are measured in-situ (next to a patient on an operating table) through a 75mm aperture in a ∼400 mm rectangular enclosure with minimal flow restriction. The particles and gasses exiting a patient are vented through an enclosed laser sheet while a camera captures images of the side-scattered light from the entrained particles. A similar optical configuration was described by Anfinrud et al.; however, we present here an extended method which provides a calibration method for determining particle size. The use of a laser sheet with side-scattered light provides a large FOV and bright image of the particles; however, the particle image dilation caused by scattering does not allow direct measurement of particle size. The calibration routine presented here is accomplished by measuring fixed particle distribution ranges with a calibrated shadow imaging system and mapping these measurements to the in-situ imaging system. The technique used for generating and measuring these particles is described. The result is a three-part process where 1) particles of varying sizes are produced and measured using a calibrated, high-resolution shadow imaging method, 2) the same particle generators are measured with the in-situ imaging system, and 3) a correlation mapping is made between the (dilated) laser image size and the measured particle size. Additionally, experimental and operational details of the imaging system are described such as requirements for the enclosure volume, light management, air filtration and control of various laser reflections. Details related to the OR environment and requirements for achieving close proximity to a patient are discussed as well.
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Antony, S. J., und M. Ghadiri. „Size Effects in a Slowly Sheared Granular Media“. Journal of Applied Mechanics 68, Nr. 5 (08.01.2001): 772–75. http://dx.doi.org/10.1115/1.1387443.
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In this paper, we analyze the nature of stress distribution experienced by large particles in a dense granular media subjected to slow shearing, using the distinct element method. The particles were generated in a three-dimensional cuboidal periodic cell in which a large solid spherical particle was submerged (“submerged particle”) at the center of a bed of monodispersed spherical particles. The granular systems with different size ratio (i.e., the ratio of the diameter of submerged particle to that of the surrounding monodispersed particles) were subjected to quasi-static shearing under constant mean stress condition. The evolution of stress distribution in the submerged particle during shearing was carefully tracked down and presented here. The nature of stress distribution is bifurcated into two components, viz., (i) hydrostatic and (ii) deviatoric components. It has been shown that, for size ratio greater than c.a. 10, the nature of stress distribution in the submerged particle is hydrostatically dominant (increases the ‘fluidity’). For smaller size ratios, the nature of stress distribution in the submerged particle is dominantly deviatoric.
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Kim, S., S. H. Cho und H. Park. „Effects of particle size distribution on the cake formation in crossflow microfiltration“. Water Supply 2, Nr. 2 (01.04.2002): 305–11. http://dx.doi.org/10.2166/ws.2002.0077.
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In crossflow microfiltration, the tendency of particle deposition of polydisperse suspensions has been established experimentally and compared with that of monodisperse suspensions. The mass transfers of particles are different according to size in polydisperse suspensions. The most particles, which deposit to membrane surface without clogging pore in microfiltration, are much larger than 0.1 μm. Among these particles, smaller particles are easier to deposit than larger particles because of shear-induced diffusion and particle deposition depends on the size distribution of small particles. Effective particle diameter is introduced as a representative particle size which can reflect the diffusivity of each particle according to size and it describes the tendency of particle deposition very well in polydisperse suspensions. The effect of effective particle diameter is larger than that of feed concentration. The most important factor affecting particle deposition of polydisperse suspensions is effective particle diameter. The results of our research suggest that the effective particle diameter can be an important factor which can represent the potential for cake formation.
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Fang, Guor-Cheng, Yuh-Shen Wu, Shih-Yo Chang, Jui-Yeh Rau, Shih-Han Huang und Chi-Kwong Lin. „Characteristic study of ionic species in nano, ultrafine, fine and coarse particle size mode at a traffic sampling site“. Toxicology and Industrial Health 22, Nr. 1 (Februar 2006): 27–37. http://dx.doi.org/10.1191/0748233706th241oa.
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A micro-orifice uniform deposit impactor (MOUDI) and a nano-MOUDI were used to measure the atmospheric coarse (PM2.5-10), fine (PM2.5), ultrafine (PM0.056 - 1) and nano (< 0.056 μm) particle concentrations at a traffic sampling site in central Taiwan during the winter period from November 2004 to January 2005. Meanwhile, concentrations of major ionic species (Cl-, NO3−, SO42−, NH4+, Na+, K+, Ca2+ and Mg2+) were also extracted from various particle size modes (nano, ultrafine, fine and coarse) and analysed by ion chromatography (DIONEX-100). The mass size distribution of ambient suspended particles exhibited two modes. The size ranges of the particles at these two particle size modes were between 1.0 and 1.8 mm and 3.2 and 5.6 mm, respectively. The average mass media aerodynamic diameter (MMAD) of suspended particles was 0.99 mm in this study. In addition, statistical methods, such as correlation coefficient and principal component analysis, were also used to identify the possible pollutant source for various particles size modes (nano, ultrafine, fine and coarse) during the winter months at a traffic sampling site in central Taiwan
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Hu, Ying Yan, Jun Feng Wang, Can Li und Jian Qiang Li. „Characterization of Cooling Rate and Microstructure of Rapidly Solidified Spherical Mono-Sized Sn-1.0Ag-0.5Cu Particles“. Materials Science Forum 960 (Juni 2019): 274–83. http://dx.doi.org/10.4028/www.scientific.net/msf.960.274.
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Spherical mono-sized Sn-1.0Ag-0.5Cu (wt.%) particles with diameter ranging from 124.0 to 337.4μm were prepared by the pulsated orifice ejection method (termed “POEM”).These spherical Sn-1.0Ag-0.5Cu particles exhibit a good spherical shape and a narrow size distribution, suggesting that liquid Sn-1.0Ag-0.5Cu can completely break the balance between the surface tension and the liquid static pressure in the crucible micropores and accurately control the volume of the droplets. Furthermore, the relationship between cooling rate and microstructures of spherical Sn-1.0Ag-0.5Cu particles was studied with a specific focus on different particle diameter during the rapid solidification. The cooling rate of spherical Sn-1.0Ag-0.5Cu particles with different diameter was evaluated by the Newton’s cooling model. It is revealed that the cooling rate decreases gradually with the increase of particle size during the rapidly solidified process. When the particle diameter is equal to 75 μm, the cooling rate of the Sn-1.0Ag-0.5Cu particle achieves 4.30×103 K/s which indicates that smaller particles can rapidly solidified due to their higher cooling rate. Meanwhile, the cooling rate decreases rapidly when the particle diameter increases between 75 and 100 μm. Furthermore, the different particle diameter with different cooling rate has a great influence on the solidification microstructure of Sn-1.0Ag-0.5Cu particles. The cooling rate and grain boundary size decreases with the increase of particle diameter during the rapid solidification. In addition, the phase size of βSn increases with the decrease of particle size. Smaller particles have relatively high cooling rate and it gives less solidification time as compared to larger particles. It is an effective route for fabrication of high-quality spherical Sn-1.0Ag-0.5Cu particles. Keywords: Spherical Sn-1.0Ag-0.5Cu particles; Rapid solidification; Structural; Cooling rate
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Tomonari, Masanori, Kiyonobu Ida, Hiromi Yamashita und Tetsu Yonezawa. „Size-Controlled Oxidation-Resistant Copper Fine Particles Covered by Biopolymer Nanoskin“. Journal of Nanoscience and Nanotechnology 8, Nr. 5 (01.05.2008): 2468–71. http://dx.doi.org/10.1166/jnn.2008.237.
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Size-controlled oxidation-resistant copper fine particles were prepared from insoluble CuO micron-sized particles. The particle sizes were quite uniform and could be varied only by the concentration of the complex reagent from 45 to 175 nm. No template material was needed for size control. Gelatin was selected as the protective polymer. Addition of protease after formation of copper fine particles decomposed preferentially loop and tail parts of gelatin. The remaining nanoskin gelatin layer, covered on the particle surface, prevents oxidation of copper.
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Xu, Jie, Kalpesh Mahajan, Wei Xue, Jessica O. Winter, Maciej Zborowski und Jeffrey J. Chalmers. „Simultaneous, single particle, magnetization and size measurements of micron sized, magnetic particles“. Journal of Magnetism and Magnetic Materials 324, Nr. 24 (Dezember 2012): 4189–99. http://dx.doi.org/10.1016/j.jmmm.2012.07.039.
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Voigtländer, J., T. Tuch, W. Birmili und A. Wiedensohler. „Correlation between traffic density and particle size distribution in a street canyon and the dependence on wind direction“. Atmospheric Chemistry and Physics 6, Nr. 12 (22.09.2006): 4275–86. http://dx.doi.org/10.5194/acp-6-4275-2006.
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Abstract. Combustion of fossil fuel in gasoline and diesel powered vehicles is a major source of aerosol particles in a city. In a street canyon, the number concentration of particles smaller than 300 nm in diameter, which can be inhaled and cause serious health effects, is dominated by particles originating from this source. In this study we measured both, particle number size distribution and traffic density continuously in a characteristic street canyon in Germany for a time period of 6 months. The street canyon with multistory buildings and 4 traffic lanes is very typical for larger cities. Thus, the measurements also are representative for many other street canyons in Europe. In contrast to previous studies, we measured and analyzed the particle number size distribution with high size resolution using a Twin Differential Mobility Analyzer (TDMPS). The measured size range was from 3 to 800 nm, separated into 40 size channels. Correlation coefficients between particle number concentration for integrated size ranges and traffic counts of 0.5 were determined. Correlations were also calculated for each of the 40 size channels of the DMPS system, respectively. We found a maximum of the correlation coefficients for nucleation mode particles in the size range between 10 and 20 nm in diameter. Furthermore, correlations between traffic and particles in dependence of meteorological data were calculated. Relevant parameters were identified by a multiple regression method. In our experiment only wind parameters have influenced the particle number concentration significantly. High correlation coefficients (up to 0.8) could be observed in the lee side of the street canyon for particles in the range between 10 and 100 nm in diameter. These values are significantly higher than correlation coefficients for other wind directions and other particle sizes. A minimum was found in the luff side of the street. These findings are in good agreement with theory of fluid dynamics in street canyons.
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Ensor, David, Robert Donovan und Bruce Locke. „Particle Size Distributions in Clean Rooms“. Journal of the IEST 30, Nr. 6 (01.11.1987): 44–49. http://dx.doi.org/10.17764/jiet.1.30.6.m24044316827q326.
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Measurements of particle size distributions smaller than 0.1 μm in Class 100 clean rooms are summarized. The size distributions were measured in operational rooms during periods of time with little activity—the so-called "at rest" conditions. A simple particle number balance model is proposed, illustrating the importance of filter penetration and atmospheric aerosol on the concentration of submicrometer particles. Preliminary calculations are used to explain the absence of < 0.1 μm diameter particles in the clean rooms tested. A ratio of condensation nucleus counter concentration to optical particle counter concentration is suggested as a parameter to provide an indication of changes in clean room particle size distribution.
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Liu, Jun, Mehmet Sarikaya und Ilhan A. Aksay. „Crystal structure-size relationship in ultrafine metallic particles“. Proceedings, annual meeting, Electron Microscopy Society of America 47 (06.08.1989): 266–67. http://dx.doi.org/10.1017/s0424820100153300.
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Ultrafine particles usually have unique physical properties. This study illustrates how the lattice defects and interfacial structures between particles are related to the size of ultrafine crystalline gold particles.Colloidal gold particles were produced by reducing gold chloride with sodium citrate at 100°C. In this process, particle size can be controlled by changing the concentration of the reactant. TEM samples are prepared by transferring a small amount of solution onto a thin (5 nm) carbon film which is suspended on a copper grid. In this work, all experiments were performed with Philips 430T at 300 kV.With controlled seeded growth, particles of different sizes are produced, as shown in Figure 1. By a careful examination, it can be resolved that very small particles have lattice defects with complex interfaces. Some typical particle structures include multiple twins, resulting in a five-fold symmetry bicrystals, and highly disordered regions. Many particles are too complex to be described by simple models.
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Nestorovic, Gordana, Slobodan Jovanovic und Katarina Jeremic. „The influence of some factors on the electrical conductivity and particle size of core/shell polystyrene/polyaniline composites“. Journal of the Serbian Chemical Society 70, Nr. 11 (2005): 1263–71. http://dx.doi.org/10.2298/jsc0511263n.
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The electrically conductive, micron-sized, core/shell polystyrene (PS)/polyaniline (PANI) composite particles were synthesized by chemical oxidative polymerization of aniline in the presence of micron-sized PS particles in 1 M HCl. The conditions of the dispersion polymerization of styrene were optimized. The influence of the initiator type employed for the chemical oxidative polymerization of aniline and the aniline (ANI) concentration on the PS/PANI particle size and size distribution and their conductivity was investigated. The obtained results show that the conductivity of the samples increased with increasing ANI concentration. The conductivity of the PS/PANI composite particles obtained with the highest ANI concentration was of the same order of magnitude as that for PANI powder. The particle size did not depend on the concentration of ANI, while the particle size distribution was narrower at higher concentrations of ANI. .
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Pronk, W., B. Sinnet, S. Meylan und M. Boller. „Characterization of nano- and microparticles in Swiss waters and their role in potable water production“. Water Supply 6, Nr. 1 (01.01.2006): 21–29. http://dx.doi.org/10.2166/ws.2006.004.
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Particles in lake water samples originating from the Swiss lakes of Zurich and Constance were analysed, showing an exponential increase of particle number with decreasing particle size down to the detection limit (350 nm). Investigation of nanoparticles in Lake Zurich by microscopic methods showed that relatively large numbers of clay particles are present with different Al/Si composition and sizes. The small-sized clay particles (ca. 80 nm) tend to build aggregates with a size of 500–1,000 nm. In karstic spring water, the particle count and size distribution is strongly dependent on the precipitation rate. At high precipitation rates, channel flow occurs in the subsoil, leading to high particle counts among the whole size range and a larger average particle size. In membrane treatment by microfiltration and ultrafiltration this leads to membrane fouling due to pore blocking and cake formation, the latter being associated with the presence of organic compounds.
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Cappa, Christopher D., Katheryn R. Kolesar, Xiaolu Zhang, Dean B. Atkinson, Mikhail S. Pekour, Rahul A. Zaveri, Alla Zelenyuk und Qi Zhang. „Understanding the optical properties of ambient sub- and supermicron particulate matter: results from the CARES 2010 field study in northern California“. Atmospheric Chemistry and Physics 16, Nr. 10 (27.05.2016): 6511–35. http://dx.doi.org/10.5194/acp-16-6511-2016.
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Abstract. Measurements of the optical properties (absorption, scattering and extinction) of PM1, PM2.5 and PM10 made at two sites around Sacramento, CA, during the June 2010 Carbonaceous Aerosols and Radiative Effects Study (CARES) are reported. These observations are used to establish relationships between various intensive optical properties and to derive information about the dependence of the optical properties on photochemical aging and sources. Supermicron particles contributed substantially to the total light scattering at both sites, about 50 % on average. A strong, linear relationship is observed between the scattering Ångström exponent for PM10 and the fraction of the scattering that is contributed by submicron particles (fsca, PM1) at both sites and with similar slopes and intercepts (for a given pair of wavelengths), suggesting that the derived relationship may be generally applicable for understanding variations in particle size distributions from remote sensing measurements. At the more urban T0 site, the fsca, PM1 increased with photochemical age, whereas at the downwind, more rural T1 site the fsca, PM1 decreased slightly with photochemical age. This difference in behavior reflects differences in transport, local production and local emission of supermicron particles between the sites. Light absorption is dominated by submicron particles, but there is some absorption by supermicron particles ( ∼ 15 % of the total). The supermicron absorption derives from a combination of black carbon that has penetrated into the supermicron mode and from dust, and there is a clear increase in the mass absorption coefficient of just the supermicron particles with increasing average particle size. The mass scattering coefficient (MSC) for the supermicron particles was directly observed to vary inversely with the average particle size, demonstrating that MSC cannot always be treated as a constant in estimating mass concentrations from scattering measurements, or vice versa. The total particle backscatter fraction exhibited some dependence upon the relative abundance of sub- versus supermicron particles; however this was modulated by variations in the median size of particles within a given size range; variations in the submicron size distribution had a particularly large influence on the observed backscatter efficiency and an approximate method to account for this variability is introduced. The relationship between the absorption and scattering Ångström exponents is examined and used to update a previously suggested particle classification scheme. Differences in composition led to differences in the sensitivity of PM2.5 to heating in a thermodenuder to the average particle size, with more extensive evaporation (observed as a larger decrease in the PM2.5 extinction coefficient) corresponding to smaller particles; i.e., submicron particles were generally more susceptible to heating than the supermicron particles. The influence of heating on the particle hygroscopicity varied with the effective particle size, with larger changes observed when the PM2.5 distribution was dominated by smaller particles.
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Tan, Vu T., La The Vinh, Vu Minh Khoi, Huynh Dang Chinh, Pham Van Tuan und Tran Ngoc Khiem. „A New Approach for the Fabrication of Tetragonal BaTiO3 Nanoparticles“. Journal of Nanoscience and Nanotechnology 21, Nr. 4 (01.04.2021): 2692–701. http://dx.doi.org/10.1166/jnn.2021.19097.
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For the first time, the BaTiO3 nano-sized particles were obtained through solid-state reaction by employing the titanium oxide nanoparticle. Meanwhile, by using TiO2 with micro-sized particles, the synthesized BaTiO3 shows the micro-sized. The XRD pattern confirms that both BaTiO3 nano-sized and micro-sized particles display the tetragonal structure. Both SEM and TEM analysis revealed that the size of the nano-sized material is in the range of 30–50 nm; in the meantime, the microsized material shows a size of 500 nm. The Eg of both BaTiO3 micro-sized and nano-sized were calculated by using the Kubelka-Munk function. The shifted bandgap of BaTiO3 nano-sized particle is nearly 0.24 eV larger than that of BaTiO3 miro-sized particle due to the particle size effect. The P-E measurement of n-BaTiO3 proved that the obtained BaTiO3 nano-sized is ferroelectric material. The result may provide a new route for the fabrication of barium titanate nanoparticle with ferroelectric properties.
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Shimosaka, Atsuko, Yoshiyuki Shirakawa und Jusuke Hidaka. „Effects of Particle Shape and Size Distribution on Size Segregation of Particles“. JOURNAL OF CHEMICAL ENGINEERING OF JAPAN 46, Nr. 3 (2013): 187–95. http://dx.doi.org/10.1252/jcej.12we179.
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Lyu, Yan, Tingting Xu, Xiang Li, Tiantao Cheng, Xin Yang, Xiaomin Sun und Jianmin Chen. „Size distribution of particle-associated polybrominated diphenyl ethers (PBDEs) and their implications for health“. Atmospheric Measurement Techniques 9, Nr. 3 (14.03.2016): 1025–37. http://dx.doi.org/10.5194/amt-9-1025-2016.
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Abstract. In order to better understand the size distribution of particle-associated PBDEs and their deposition pattern in the human respiratory tract, we carried out a 1-year campaign during 2012–2013 for the measurement of size-resolved particles at the urban site of Shanghai. The results showed that particulate PBDEs exhibited a bimodal distribution with a mode peak in the accumulation particle size range and the second mode peak in the coarse particle size ranges. As the number of bromine atoms in the molecule increases, accumulation-mode peak intensity increased while coarse-mode peak intensity decreased. This change was consistent with the variation of PBDEs' subcooled vapor pressure. Absorption and adsorption processes dominated the distribution of PBDEs among the different size particles. The evaluated deposition flux of Σ13 PBDEs was 26.8 pg h−1, in which coarse particles contributed most PBDEs in head and tracheobronchial regions, while fine-mode particles contributed major PBDEs in the alveoli region. In association with the fact that fine particles can penetrate deeper into the respiratory system, fine-particle-bound highly brominated PBDEs can be inhaled more deeply into human lungs and cause a greater risk to human health.
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Lyu, Y., T. Xu, X. Li, T. Cheng, X. Yang, X. Sun und J. Chen. „Particle-size distribution of polybrominated diphenyl ethers (PBDEs) and its implications for health“. Atmospheric Measurement Techniques Discussions 8, Nr. 12 (09.12.2015): 12955–92. http://dx.doi.org/10.5194/amtd-8-12955-2015.
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Abstract. In order better to understand the particle-size distribution of particulate PBDEs and their deposition pattern in human respiratory tract, we made an one year campaign 2012–2013 for the measurement of size-resolved aerosol particles at Shanghai urban site. The results showed that particulate PBDEs exhibited a bimodal distribution with a mode peak in the accumulation particle size range and the second mode peak in the coarse particle size ranges. As the number of bromine atoms in the molecule increased, accumulation mode peak intensity increased while coarse mode peak intensity decreased. This change was the consistent with the variation of PBDEs' sub-cooled vapor pressure. Absorption and adsorption process dominated the distribution of PBDEs among the different size particles. Evaluated deposition flux of Σ13PBDE was 26.8 pg h−1, in which coarse particles contributed most PBDEs in head and tracheobronchial regions, while fine mode particles contributed major PBDEs in the alveoli region. In associated with the fact that fine particles can penetrate deeper into the respiratory system, fine particle-bound highly brominated PBDEs can be inhaled more deeply into human lungs and cause a greater risk to human health.
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Ouyang, F., und M. Isaacson. „Observation of the quantum size effect in the STEM“. Proceedings, annual meeting, Electron Microscopy Society of America 47 (06.08.1989): 230–31. http://dx.doi.org/10.1017/s0424820100153129.
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The study of small particles or microclusters has been very active in recent years. When the particle size becomes smaller, its electronic properties deviate from those of bulk material and become size dependent. This phenomenon is refered to as the quantum size effect.One of the frequently used probes for studying the electronic states of small particles is the surface plasmon (SP) excitation. Genzel et al. studied the optical absorption peaks from silver particles in glass. They found a blue shift of the SP peak when the particle size becomes smaller (see Fig 2). Electron energy loss spectroscopy (EELS) studies have also been performed. Recently vom Felde et al. reported broad beam EELS with large momentum transfer from potassium particles embedded in a MgO matrix. They observed that the surface plasmon energy increases when particle size becomes smaller, and there is a positive dispersion for particles of size 40 Å.
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Garnier, Laurence, Lee Ratner, Benjamin Rovinski, Shi-Xian Cao und John W. Wills. „Particle Size Determinants in the Human Immunodeficiency Virus Type 1 Gag Protein“. Journal of Virology 72, Nr. 6 (01.06.1998): 4667–77. http://dx.doi.org/10.1128/jvi.72.6.4667-4677.1998.
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ABSTRACT 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.
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Mori, Yasushige, Tetsu Tsunamoto und Hitoshi Nakayama. „Computer Simulation of Electrorheological Fluids in the Binary System of Particle Size“. International Journal of Modern Physics B 13, Nr. 14n16 (30.06.1999): 1822–27. http://dx.doi.org/10.1142/s0217979299001843.
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One of the typical electrorheological (ER) fluids consists of suspension of fine particles in the liquid of low dielectric constant. Particles for ER fluids generally have a size distribution, and some experimental results were reported which showed the effect of particle size on the shear stress of ER fluids. On the other hand, the simulation by dielectric polarization model concluded that the shear stress calculated did not depend on the particle size under the same volume fraction of particles. In order to understand the effect of particle size, the two dimensional computer simulation was carried out for a system containing particles of different size, by using a model similar to that reported by Klingenberg et al. It was found that the shear stress of uniform size system did not depend on the particle size. When small and large particles, with the diameter ratio of 1:2, were mixed in equal numbers of particles, the chain-like clusters consisiting of both sizes of particles were formed. The shear stress and the response time of the binary size system were close to those of uniform size system, if the total volume fraction of particles was kept constant.
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Bordoloi, Ankur D., und Evan Variano. „Rotational kinematics of large cylindrical particles in turbulence“. Journal of Fluid Mechanics 815 (20.02.2017): 199–222. http://dx.doi.org/10.1017/jfm.2017.38.
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The rotational kinematics of inertial cylinders in homogeneous isotropic turbulence is investigated via laboratory experiments. The effects of particle size and shape on rotation statistics are measured for near-neutrally buoyant particles whose sizes are within the inertial subrange of turbulence. To examine the effects of particle size, three right-circular cylinders (aspect ratio $\unicode[STIX]{x1D706}=1$) are considered, with size $d_{eq}=16\unicode[STIX]{x1D702}$, $27\unicode[STIX]{x1D702}$ and $67\unicode[STIX]{x1D702}$. Here, $d_{eq}$ is the diameter of a sphere whose volume is equal to that of the particle and $\unicode[STIX]{x1D702}$ is the Kolmogorov length scale. Results show that the variance of the particle rotation rate follows a $-4/3$ power-law scaling with respect to $d_{eq}$. To examine the effect of particle shape, two cylinders with identical volumes and different aspect ratios ($\unicode[STIX]{x1D706}=1$ and $\unicode[STIX]{x1D706}=4$) are measured. Their motion also scales with $d_{eq}$ regardless of shape. Simultaneous measurements of orientation and rotation for $\unicode[STIX]{x1D706}=4$ particles allows a decomposition of rotation along the primary axes of each particle. This analysis shows that there is no preference for rotation about a particle’s symmetry axis, unlike the preference displayed by sub-Kolmogorov-scale particles in previous studies.