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Small Particle Size (small + particle_size)
Selected AbstractsVISCOUS PROPERTIES OF TARO FLOUR EXTRUDED WITH WHEY PROTEINS TO SIMULATE WEANING FOODS,JOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 3 2002C. I. ONWULATA Taro flour, derived from the corm of Colocasia Esculenta cv. Lehua, a root tuber grown in the tropical regions of the world, was extruded with whey protein concentrate (WPC), whey protein isolate (WPI) or lactalbumin (LAC), to derive blends containing 20% protein, simulating the protein content of some weaning foods. Taro flour is unique because of its extremely small particle size (1,5 micron) and high mucilage or gum content, making it a possible replacement for corn or wheat starch in weaning foods. Extrusion processing temperatures were from 100 to 130C and moisture of the feed blends was held constant at 18%. The extrudates were pulverized, made into powders, and rehydrated to make a paste. Viscosities of the feed blends before extrusion and the pastes made from the extrudates were determined using a Rapid Visco Analyzer (RVA) to determine peak, final, and breakdown viscosities. Water solubility and absorption indices were also determined. Extrudates made from taro containing whey products expanded more than taro alone; were easier to grind into powders; and rehydrated readily in water to form pastes. Before extrusion, the peak viscosities of the blends were 5000, 2600, 1600, 1600 cP for taro flour, taro with WPI, taro with WPC, or taro with LAC, respectively. After extrusion cooking, the viscosities for taro flour, taro with WPI, taro with WPC, or taro with LAC were 110, 65, 70 or 90 cP, respectively. Taro extrudates without protein absorbed the most water, and were more soluble than products containing whey proteins or LAC. The addition of whey proteins reduced peak viscosities, but WPI and taro pastes were characteristic of weaning foods. Both extrusion cooking and the [source] Methyl methacrylate emulsion polymerization at low monomer concentration: Kinetic modeling of nucleation, particle size distribution, and rate of polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 14 2001Jorge Herrera-Ordóñez Abstract The results of a mathematical model developed in the authors' previous work are discussed and compared against final number (N) and size distribution of particles (PSD) and the rate of polymerization (RP) experimental data of methyl methacrylate (MMA) emulsion polymerization above the critical micelle concentration (cmc) of the surfactant. On the basis of the model results, the hypothesis that the observed bimodal PSD can be ascribed to secondary nucleation as proposed in the literature is questionable. It is discussed that this PSD can also be caused by differences in the growing rate of different-size particles as predicted for styrene emulsion polymerization. Because of the small particle size obtained at low initial monomer concentration, the high rate of free-radical desorption reduces the accumulation of these species; therefore, the autoacceleration effect is less pronounced for the conditions under study compared with the usual behavior of the RP during MMA emulsion polymerization above cmc. Similarities and differences between model predictions and experimental data are discussed. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2547,2556, 2001 [source] Fast analysis in liquid chromatography using small particle size and high pressureJOURNAL OF SEPARATION SCIENCE, JSS, Issue 12 2006Dao T.-T. Abstract In order to enhance chromatographic performances in terms of efficiency and rapidity, LC has recently evolved in the development of short columns packed with small particles (sub-2 ,m) working at high pressures (>400 bar). This approach has been described 30 years ago according to the fundamental chromatographic equations. However, systems and columns compatible with such high pressures have been introduced in the market in 2004 only. Advantages of small particles working at high pressure will be discussed in terms of sensitivity, efficiency, resolution, and analysis time. Potential problems encountered with high pressure in terms of frictional heating and solvent compressibility will also be discussed even if systems working at a maximum pressure of 1000 bar are not influenced by these parameters and give reliable and reproducible results. Several applications will highlight the potential and interest of this new technology. [source] Kinetics of Electrophoretic Deposition for Nanocrystalline Zinc Oxide CoatingsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2004Yuan-Chung Wang An integrated process combining the preparation of ZnO nanoparticles and the formation of ZnO coatings using electrophoretic deposition (EPD) is reported. The work focuses on the deposition kinetics of nanocrystalline ZnO coatings on copper electrodes during EPD by direct measurement of the thickness of the deposited layer. The experimental results show that the EPD process is a powerful route to fabricate uniform coatings with desired thickness and excellent surface smoothness, which might be attributed to small particle size and narrow size distribution. On the other hand, the deposition kinetics changes with applied voltage and deposition time. The deposition thickness increases with increasing applied voltage and deposition time. In a short deposition time, the deviation of deposition rate between the theoretical and experimental values is caused by voltage drops during deposition, and the discrepancy increases with the applied voltage. Moreover, the increasing voltage drop and depletion of the suspension lead to decreasing current and lower deposition rate after longer deposition time. The critical transition time of deposition kinetics is found to exponentially decrease with increasing applied voltage. [source] Preparation of tin nanocomposite as anode material by molten salts method and its application in lithium ion batteriesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 11 2009Mohd Faiz Hassan Abstract A nanocomposite material (SnO2Co3O4) has been synthesized as an anode material for lithium-ion batteries by the molten salt method. Characterization by X-ray diffraction (XRD) and transmission electron microscopy (TEM) showed that the composite has a small particle size. The electrochemical performance was examined, including the charge,discharge and cycling properties. The experimental results showed that the sample containing the highest amount of Co3O4 compound exhibited a specific capacity of 355,mAh g,1 after 40 cycles, with cycling at 70,mA g,1 (35.2% higher than for the sample containing a lower amount of Co3O4). It seems that increasing the amount of Co3O4 can give good capacity retention and high specific capacity. [source] Characterization of an insoluble polyimide oligomer by matrix-assisted laser desorption/ionization time-of-flight mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 20 2002Anthony P. Gies In the past two years, papers have appeared in the literature which demonstrate that matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectra can be obtained from matrix-analyte preparations which have been produced by grinding the two materials together until a powder of small particle size is obtained. In the present study that methodology was modified and applied to an insoluble polyimide oligomer, poly(4,4,-oxydiphenylenepyromellitimide) (POPM). Two matrix materials were employed in this analysis, 1,8 dihydroxyanthrone (dithranol) and 3-aminoquinoline, with and without an additional cationizing agent. The spectra obtained by this method are shown to be sensitive to the matrix employed in the analysis as well as the quantity of cationizing agent combined with the matrix. Copyright © 2002 John Wiley & Sons, Ltd. [source] Liposome-Encapsulated Hemoglobin Reduces the Size of Cerebral Infarction in Rats: Effect of Oxygen AffinityARTIFICIAL ORGANS, Issue 2 2009Dai Fukumoto Abstract Liposome-encapsulated hemoglobin (LEH) with a low oxygen affinity (l-LEH, P50 = 45 mm Hg) was found to be protective in the rodent and primate models of ischemic stroke. This study investigated the role of LEH with a high O2 affinity (h-LEH, P50 = 10 mm Hg) in its protective effect on brain ischemia. The extent of cerebral infarction was determined 24 h after photochemically induced thrombosis of the middle cerebral artery from the integrated area of infarction detected by triphenyltetrazolium chloride staining in rats receiving various doses of h-LEH as well as l-LEH. Both h-LEH and l-LEH significantly reduced the extent of cortical infarction. h-LEH remained protective at a lower concentration (minimal effective dose [MED]: 0.08 mL/kg) than l-LEH (MED: 2 mL/kg) in the cortex. h-LEH reduced the infarction extent in basal ganglia as well (MED: 0.4 mL/kg), whereas l-LEH provided no significant protection. h-LEH provided better protection than l-LEH. The protective effect of both high- and low-affinity LEH may suggest the importance of its small particle size (230 nm) as compared to red blood cells. The superiority of h-LEH over l-LEH supports an optimal O2 delivery to the ischemic penumbra as the mechanism of action in protecting against brain ischemia and reperfusion. [source] Measurement of the size distribution of water-filled pores at different matric potentials by stray field nuclear magnetic resonanceEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 1 2005N. R. A. Bird Summary The water retention characteristic provides the traditional data set for the derivation of a soil's pore-size distribution. However, the technique employed to achieve this requires that assumptions be made about the way pores interconnect. We explore an alternative approach based on stray field nuclear magnetic resonance (STRAFI-NMR) to probe the water-filled pores of both saturated and unsaturated soils, which does not require information relating to pore connectivity. We report the relative size distributions of water-occupied pores in saturated and unsaturated samples of two sets of glass beads of known particle size, two sands, and three soils (a silty loam, a sandy loam and a loamy sand), using measurements of the NMR T1 proton relaxation time of water. The T1 values are linearly related to pore size and consequently measured T1 distributions provide a measure of the pore-size distribution. For both the sands and the glass beads at saturation the T1 distributions are unimodal, and the samples with small particle sizes show a shift to small T1 values indicating smaller voids relative to the samples with larger particles. Different matric potentials were used to reveal how the water-occupied pore-size distribution changes during drainage. These changes are inconsistent with, and demonstrate the inadequacies of, the commonly employed parallel-capillary tube model of a soil pore space. We find that not all pores of the same size drain at the same matric potential. Further, we observe that the T1 distribution is shifted to smaller values beyond the distribution at saturation. This shift is explained by a change in the weighted average of the relaxation rates as the proportion of water in the centre of water-filled pores decreases. This is evidence for the presence of pendular structures resulting from incomplete drainage of pores. For the soils the results are similar except that at saturation the T1 distributions are bimodal or asymmetrical, indicative of inter-aggregate and intra-aggregate pore spaces. We conclude that the NMR method provides a characterization of the water-filled pore space which complements that derived from the water retention characteristic and which can provide insight into the way pore connectivity impacts on drainage. [source] Efficient Luminescence from Rare-Earth Fluoride Nanoparticles with Optically Functional Shells,ADVANCED FUNCTIONAL MATERIALS, Issue 7 2006M. Lezhnina Abstract Rare-earth fluorides are a class of materials with considerable potential in optical applications. Fluoride lattices typically permit high coordination numbers for the hosted rare-earth ions, and the high ionicity of the rare-earth-to-fluorine bond leads to a wide bandgap and very low vibrational energies. These factors make rare-earth fluorides very useful in optical applications employing vacuum ultraviolet and near-infrared excitation. The preparation of nanometer-sized particles has opened the door for new properties and devices if the performance of their macroscopic counterparts can be conserved in the nanometer regime. However, at small particle sizes, defect surface states and adhering water reduce the optical efficiency. These shortcomings can be reduced by applying protective shells around the luminescent cores, which can also be involved in the luminescent process. [source] Ketoprofen nanoparticle gels formed by evaporative precipitation into aqueous solutionAICHE JOURNAL, Issue 7 2006Xiaoxia Chen Abstract Aqueous nanoparticle gels of a poorly-water soluble drug, ketoprofen, were produced by evaporative precipitation into aqueous solution (EPAS). Liquid droplets of surfactant stabilized ketoprofen containing residual solvent were dispersed in water from 60 to 90°C below the melting point of pure ketoprofen. The carboxylic acid group in ketoprofen dissociates in pure water, providing electrostatic stabilization of the droplets to complement steric stabilization. Stable amorphous ketoprofen particles with a mean size of 135 nm, measured by dynamic light scattering, were formed with only 0.1% w/v poloxamer 407, resulting in an exceptionally high drug-to-surfactant ratio of 10:1. For 5% w/v poloxamer 407, interactions with ketoprofen produced a bluish, transparent gel composed of ,50 nm particles. In 2 min, 98% of the ketoprofen in the gel nanoparticles dissolved. The favorable interactions between the ketoprofen and poloxamer 407, along with the electrostatic and steric stabilization, lead to gelation, which further stabilizes the unusually small particles. The rapidly dissolving wet gels with extremely small particle sizes, one month stability, and relatively low viscosities, are of interest in transdermal and parenteral delivery; furthermore, the gels may be dried for oral delivery. © 2006 American Institute of Chemical Engineers AIChE J, 2006 [source] Size Measurement of Very Small Spherical Particles by Mie Scattering Imaging (MSI)PARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 5 2004Arne Graßmann Abstract The Mie Scattering Imaging method (MSI) gathers out-of-focus images of dispersed spherical particles present in a laser light sheet and extracts the individual particle diameter from these images. The general idea of the method has been around for more than a decade and a number of papers has dealt with it over recent years. Our work focuses on small particle sizes from 20 ,m down to 2 ,m, a range which has not been tackled so far although it is of great importance in particle systems. We present an optical set-up with a special arrangement of camera lenses that allows to work in this range. An evaluation algorithm based on correlation of the experimental optical information with theoretical Mie scattering was found to give the most accurate results for particle sizing. Besides accuracy measurements on solid spheres the versatility of the method is demonstrated by an example of transient droplet growth between 2,7,,m. [source] Nanoparticle Production with Stirred-Media Mills: Opportunities and LimitsCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 9 2010C. Knieke Abstract Nanoparticles can be produced by wet grinding in stirred-media mills. In the lower nanometer range a true grinding limit exists, where the transferred energy from the grinding media is no longer sufficient to induce further breakage of the particles even after stressing events with high stress energies. Variations in process conditions lead to the conclusion that the grinding limit is hardly affected by most of the investigated process parameters. However, at high solids concentrations and/or small particle sizes, a drastic increase in suspension viscosity occurs, which leads to a dampening of the grinding media motion and to a reduction in the transferred stress energy. Hence, the rheological behavior can limit the grinding process, and a viscous dampening-related grinding limit can be reached prior to the true grinding limit. [source] | |||||||||||||