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Particle Size Distribution (particle + size_distribution)
Kinds of Particle Size Distribution Selected AbstractsQUALITY AND CONSUMER ACCEPTANCE OF AKARA (FRIED COWPEA PASTE) PROCESSED FROM WET- AND DRY-MILLED COWPEA (VIGNA UNGUICULATA) MEAL WITH SPECIFIED PARTICLE SIZE DISTRIBUTIONJOURNAL OF FOOD QUALITY, Issue 3 2007MELISSA A. VANCHINA ABSTRACT Direct quality indicators of cowpea paste and akara produced from traditionally wet-milled peas, and hammer-milled (dry-milled) and freeze-dried (wet-milled) meals were examined in this study. Both meal samples studied were formulated to consist of 65% medium-sized particles and 35% large particles by weight. Particle volume mean diameters (µm) of the three paste samples were not significantly different from one another at the various stages during akara production. Scanning electron micrographs of akara crumb were converted to threshold images and analyzed. There was no significant difference in the amount of air found in the akara samples. Akara produced from both meals was found acceptable by sensory panelists with no significant difference in any of the attributes or overall liking among the three samples. [source] Particle Size Distribution (Texture) of Eroded Soil MaterialJOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 5 2002F. Basic Abstract The total quantity of erosional drift on a Stagnic Luvisol on which six tillage methods were used was measured over 5 years of investigation. The texture of the tilled soil and the erosional drift for each trial method was recorded in the same plots. The results obtained suggested that erosional drift was generally richer in silt and clay particles. The standard deviations of coarse sand indicated that approximately the same quantity of coarse sand was found in plot soil and in erosional drift for all tillage methods. Sometimes more and sometimes fewer fine sand particles were found in erosional drift than in plot soil. In most cases, more silt particles were found in erosional drift than in plot soil. The standard deviation and coefficient of variation for clay and silt were higher in erosional drift than in plot soil for all methods. The highest content of clay particles was recorded in erosional drift from the no-tillage treatment in all investigation years. The results suggest that the correct choice of tillage method (no-tillage and ploughing across the slope) on a Stagnic Luvisol can protect the soil on a slope. [source] Measurement based modeling and control of bimodal particle size distribution in batch emulsion polymerizationAICHE JOURNAL, Issue 8 2010Mazen Alamir Abstract In this article, a novel modeling approach is proposed for bimodal Particle Size Distribution (PSD) control in batch emulsion polymerization. The modeling approach is based on a behavioral model structure that captures the dynamics of PSD. The parameters of the resulting model can be easily identified using a limited number of experiments. The resulting model can then be incorporated in a simple learning scheme to produce a desired bimodal PSD while compensating for model mismatch and/or physical parameters variations using very simple updating rules. © 2010 American Institute of Chemical Engineers AIChE J, 2010 [source] Coupled Single-Particle and Population Balance Modeling for Particle Size Distribution of Poly(propylene) Produced in Loop ReactorsMACROMOLECULAR REACTION ENGINEERING, Issue 2 2010Zheng-Hong Luo Abstract A comprehensive model was developed for the PSD of PP produced in loop reactors. The polymeric multilayer model (PMLM) was first applied to calculate the single particle growth rate under intraparticle transfer limitations. In order to obtain the comprehensive model, the PMLM was solved together with a steady-state particle population equation to predict the PSD in the loop reactors. The simulated PSD data obtained under steady-state polymerization conditions agreed with the actual data collected from industrial scale plant. The comprehensive model was also used to predict the effects of some critical factors, including the intraparticle mass and heat transfer limitations, the feed catalyst particle size and the catalyst deactivation, etc., on the PSD. [source] Experimental Study on Particle Size Distribution and Concentration Using Transmission Fluctuation Spectrometry with the Autocorrelation TechniquePARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 3 2005Xiaoai Guo Abstract Based on the statistical characteristics of the transmission fluctuations in the particle suspension, transmission fluctuation spectrometry with autocorrelation (TFS-AC) is described theoretically, with the assumptions of geometric ray propagation and completely absorbent particles in the suspension. The experiments presented here are realized in a focused Gaussian beam with the TFS-AC technique. The acquisition of transmission fluctuation signals is achieved by using a high-resolution digital oscilloscope. The transition function of TFS-AC is obtained by varying the autocorrelation time. With a modified iterative Chahine inversion algorithm, solving a linear equation retrieves information on the particle size distribution and particle concentration. Some experimental results on spherical and non-spherical particles are presented and discussed. The experiments cover a particle size range from 1,m to 1000,,m and a particle concentration of up to 12,%. [source] Analysis of Particle Size Distribution by Particle TrackingPARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 5 2004Christiane Finder Abstract Particle tracking is performed using a combination of dark field or fluorescence video microscopy with automatic image analysis. The optical detection together with the image analysis software allows for the time resolved localization of individual particles with diameters between 100 and 1000,nm. Observation of their Brownian motion over a set of time intervals leads to the determination of their mean square displacements under the given room temperature and viscosity. Hereby, the radii of a set of particles visible within a given optical frame are derived simultaneously. Rapid data analysis leads to reliable particle size histograms. The applicability of this method is demonstrated on polystyrene latices and PMMA nanospheres with radii between 51,nm and 202,nm. [source] The Effect of Particle Size Distribution on Pressure Drop through Packed Beds of Cooked Wood ChipsTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2005Quak Foo Lee Abstract The pressure drop of process liquors through columns of wood chips determines the operability, efficiency and control of both batch and continuous pulp digesters and the quality of the pulp produced from them. Pressure drop was measured through columns of industrial white spruce chips (produced with a chipping head-rig) as a function of the chip size distribution and the extent of delignification. Flow resistance depended on the porosity of the chip bed which was affected by the kappa number of the chips (which affected their flexibility) and chip size distribution, the compaction forces applied to the column, and the liquid superficial velocity. The chip beds were compressible and inelastic. Previous work from the literature using the Ergun equation to characterize pressure losses through chip beds is examined and compared with results of this work. La perte de charge des liqueurs de procédés dans des colonnes de copeaux de bois détermine l'opérabilité, l'efficacité et le contrôle des digesteurs de pâtes discontinus et continus, ainsi que la qualité de la pâte produite. La perte de charge a été mesurée dans des colonnes de copeaux d'épinette (produits avec une machine de fabrication de copeaux) en fonction de la distribution de taille des copeaux et du degré de délignification. La résistance à l'écoulement dépend de la porosité du lit de copeaux qui est influencée par le nombre de kappa des copeaux (qui influe sur leur flexibilité) et la distribution de taille des copeaux, les forces de compaction appliquées à la colonne ainsi que la vitesse de liquide superficielle. Les lits de copeaux sont compressibles et inélastiques. Un travail antérieur de la littérature scientifique faisant appel à l'équation d'Ergun pour caractériser les pertes de charge dans les lits de copeaux est examiné et comparé aux résultats du présent travail. [source] Particle Size Distributions from Static Light Scattering with Regularized Non-Negative Least Squares ConstraintsPARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 6 2006Alejandro R. Roig Abstract Simulated data from static light scattering produced by several particle size distributions (PSD) of spherical particles in dilute solution is analyzed with a regularized non-negative least squares method (r-NNLS). Strong fluctuations in broad PSD's obtained from direct application of NNLS are supressed through an averaging procedure, as introduced long ago in the inversion problem in dynamic light scattering. A positive correlation between the best PSD obtained from several averaging schemes and the condition number of the respective data transfer matrices was obtained. The performance of the method is found to be similar to that of constrained regularization (CONTIN), which uses also NNLS as a starting solution, but incorporates another regularizing strategy. [source] Juice Clarification by Thermostable Fractions of Marsh Grapefruit PectinmethylesteraseJOURNAL OF FOOD SCIENCE, Issue 5 2002M. Corredig ABSTRACT: Orange juice clarification by thermostable pectinmethylesterase (TS-PME), isolated from grapefruit pulp by ammonium sulfate precipitation, and ion-exchange and affinity chromatography was investigated. TSPME, having different specific activities, induced different clarification behavior of reconstituted orange juice at 2 units/ml. Based on percent transmittance, TS-PME fraction with the lower specific activity clarified juices earlier than TS-PME at higher specific activity. Particle size distribution of the cloud-soluble fraction showed that TS-PME increased the average particle size from 0.7 ,m to 1 mm and maintained a monomodal distribution. After 27 d of storage at 4 °C, samples of clarified juice still showed a large population of small cloud particles when measured by diffraction light scattering. [source] Quantifying effects of particulate properties on powder flow properties using a ring shear testerJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 9 2008Hao Hou Abstract Effects of particle size, morphology, particle density, and surface silicification, on powder flow properties were investigated using a ring shear tester. Flow properties were quantified by flow function (FF), that is, unconfined yield strength, fc, as a function of major principal stress. A total of 11 powders from three series of microcrystalline cellulose (MCC): Avicel (regular MCC, elongated particles), Prosolv (silicified MCC, elongated particles), and Celphere (spherical MCC), were studied. Particle size distribution in each type of MCC was systematically different. Within each series, smaller particles always led to poorer powder flow properties. The slope of FF line was correlated to degree of powder consolidation by external stress. A key mechanism of the detrimental effect of particle size reduction on flow properties was the larger powder specific surface area. Flow properties of Celphere were significantly better than Avicel of comparable particles size, suggesting spherical morphology promoted better powder flow properties. Flow properties of powders different in densities but similar in particle size, shape, and surface properties were similar. When corrected for density effect, higher particle density corresponded to better flow behavior. Surface silicification significantly improved flow properties of finer MCC, but did not improve those of coarser. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:4030,4039, 2008 [source] Synthesis of Mixed Conducting Ceramic Oxides SrFeCo0.5Oy Powder by Hybrid Microwave HeatingJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2002Di Huo Mixed conducting ceramic oxide SrFeCo0.5Oy powders were prepared by a conventional solid-state reaction method and two types of hybrid microwave heating methods. XRD, SEM/EDS (energy-dispersive spectroscopy), and TEM/EDX (energy-dispersive X-ray microanalysis) were used to characterize the products. The conventional heated sample is a three-phase mixture composed of a predominant orthorhombic Sr4(Fe1,xCox)6O13±, phase, a cubic perovskite SrFe1,xCoxO3,, phase, and a CoO phase. Phase components of the direct hybrid heated samples are similar to those of the conventional heated sample, except that its predominant phase is a cubic perovskite SrFe1,xCoxO3,, phase other than the orthorhombic Sr4(Fe1,xCox)6O13±, phase. The indirect hybrid heated sample is mainly composed of a cubic perovskite Sr(Fe,Co)1.5Oy phase, with a trace amount of orthorhombic phase and spinel (Fe,Co) oxides. The cobalt content of the Sr(Fe,Co)1.5Oy phase is much higher than that of the SrFe1,xCoxO3,, phase. Particle size distribution of the conventional heated sample is very wide. The indirect hybrid heated sample has a relatively narrow particle size distribution, with an average particle size of 3,4 ,m, but the particles stick to form agglomerates. The morphology of the direct hybrid heated sample is similar to that of the conventional heated sample, except that submicrometer grade particles were rarely observed. [source] Starch and fibre distribution in maize silages in relation to particle sizeJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 3 2003I Fernandez Abstract In a first trial the particle size distribution of four maize silages was measured by two different sieving methods, dry and wet sieving. Particle size distribution was quantified by three values, mean particle size, extent of dispersion, and proportion of large particles. Wet sieving separated particles better than dry sieving and was more suitable for measuring maize silage particle size. In a second trial the particle size distribution of 10 maize hybrids grown in the same conditions was measured by wet sieving. Starch proportion in large particles varied widely between maize hybrids, from 39.7 to 82.4%, against a variation from 75.4 to 100% for cell wall proportion in the same class of particles, and these variations might be predicted by dry matter distribution. © 2003 Society of Chemical Industry [source] A Chemical Model for the Dispersion of Fillers in a Polymeric MatrixTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 6 2002Tomas Lozano Abstract Particle size distribution affects strongly physical and mechanical properties of filled polymers. The proposed model uses agglomerate size population balance in its new mathematical formulation expressing agglomeration, break-up and erosion as an evolution of one particle subjected to mean-filed type interaction with others. The erosion parameters have been calculated with experiments in an internal mixer. Controlled breakup of agglomerates was carried out through capillary dies to evaluate breakup parameters. Calcium carbonate filled polypropylene system was used to validate the formulation. La distribution de taille des particules influe fortement sur les propriétés physiques et mécaniques des polymères composites. Un modèle basé sur les bilans de population de taille des agglomérats est proposé. La nouvelle formulation mathématique exprime l'agglomération, la rupture et l'érosion en fonction de l'évolution d'une particule soumise à une interaction représentative moyennée avec les autres. Les paramètres d'érosion ont été calculés lors d'expériences dans un mélangeur interne. La rupture contrôlée des agglomérats a été effectuée dans des filières capillaires afin d'évaluer les paramètres de rupture. La formulation est validée avec le système composite polypropylène-carbonate de calcium. [source] Particle size distributions from small-angle scattering using global scattering functionsJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 4 2004G. Beaucage Control and quantification of particle size distribution is of importance in the application of nanoscale particles. For this reason, polydispersity in particle size has been the focus of many simulations of particle growth, especially for nanoparticles synthesized from aerosols such as fumed silica, titania and alumina. Single-source aerosols typically result in close to a log-normal distribution in size and micrograph evidence generally supports close to spherical particles, making such particles ideal candidates for considerations of polydispersity. Small-angle X-ray scattering (SAXS) is often used to measure particle size in terms of the radius of gyration, Rg, using Guinier's law, as well as particle surface area, S/V, from the Porod constant B and the scattering invariant Q. In this paper, the unified function is used to obtain these parameters and various moments of the particle size distribution are calculated. The particle size obtained from BET analysis of gas adsorption data directly agrees with the moment calculated from S/V. Scattering results are also compared with TEM particle-counting results. The potential of scattering to distinguish between polydisperse single particles and polydisperse particles in aggregates is presented. A generalized index of polydispersity for symmetric particles, PDI = BRg4/(1.62G), where G is the Guinier prefactor, is introduced and compared with other approaches to describe particle size distributions in SAXS, specifically the maximum-entropy method. [source] Cospray dried antibiotics for dry powder lung deliveryJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 8 2008Handoko Adi Abstract The aim of this study was to assess the potential of delivering a combination antibiotic therapy, containing doxycycline and ciprofloxacin (both hydrochloride) as a dry powder (DPI) formulation for inhalation. Single and combination antibiotics were produced by spray drying. Particle size distributions were characterized by laser diffraction and imaging conducted by scanning electron microscopy. Solid-state characterisation of the antibiotics was carried out using differential scanning calorimetry, dynamic vapour sorption, X-ray powder diffraction, and differential scanning calorimetry. Using the Aerolizer® device, the aerosol performance was measured using multistage liquid impinger and analysed using high performance liquid chromatography (R2,=,1.0, CV,=,0.4,1.0%). Furthermore, a disk diffusion test was performed for the assessment of the in vitro antimicrobial activity of the raw and spray dried antibiotics against bacteria. Results showed that cospray drying of the ciprofloxacin and doxycycline produced an antibiotic formulation (in a 1:1 ratio) suitable for inhalation that showed to be physically more stable then the analogous single spray dried antibiotic. The cospray dried powder has improved dispersion over the less stable single spray dried ciprofloxacin. The spray dried antibiotics were observed to have similar antimicrobial activity to the original antibiotics for Staphylococcus aureus, Pseudomonas aeruginosa and Streptococcus pyrogenes, suggesting the spray drying process does not affect the anti-bacterial activity of the drug. Cospray dried antibiotics from a DPI is thus feasible and can potentially be an attractive delivery alternative to the more conventional systemic delivery route. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97: 3356,3366, 2008 [source] Factors affecting the deposition of inhaled porous drug particlesJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 7 2002Cynthia J. Musante Abstract Recent findings indicate that the inhalation of large manufactured porous particles may be particularly effective for drug delivery. In this study, a mathematical model was employed to systematically investigate the effects of particle size, particle density, aerosol polydispersity, and patient ventilatory parameters on deposition patterns of inhaled drugs in healthy human lungs. Aerodynamically similar particles with densities of 0.1, 1.0, and 2.0 g/cm3 were considered. Particle size distributions were defined with mass median aerodynamic diameters (MMADs) ranging from 1 to 3 ,m and geometric standard deviations ranging from 1.5 to 2.5, representing particles in the respirable size range. Breathing rates of 30 and 60 L/min with tidal volumes of 500 to 3000 mL were assumed, simulating shallow to deep breaths from a dry powder inhaler. Particles with a high density and a small geometric diameter had slightly greater deposition fractions than particles that were aerodynamically similar, but had lower density and larger geometric size (typical of manufactured porous particles). This can be explained by the fact that particles with a small geometric diameter deposit primarily by diffusion, which is a function of geometric size but is independent of density. As MMAD increased, the effect of density on deposition was less pronounced because of the decreased efficiency of diffusion for large particles. These data suggest that polydisperse aerosols containing a significant proportion of submicron particles will deposit in the pulmonary airways with greater efficiency than aerodynamically similar aerosols comprised of geometrically larger porous particles. © 2002 Wiley-Liss Inc. and the American Pharmaceutical Association J Pharm Sci 91:1590,1600, 2002 [source] Laboratory simulation of the salt weathering of schist: II.EARTH SURFACE PROCESSES AND LANDFORMS, Issue 5 2007Fragmentation of fine schist particles Abstract Recent developments in long term landform evolution modelling have created a new demand for quantitative salt weathering data, and in particular data describing the size distribution of the weathered rock fragments. To enable future development of rock breakdown models for use in landscape evolution and soil production models, laboratory work was undertaken to extend existing schist/salt weathering fragmentation studies to include an examination of the breakdown of sub-millimetre quartz chlorite schist particles in a seasonally wet tropical climate. Laser particle sizing was used to assess the impact of different experimental procedures on the resulting particle size distribution. The results reveal that salt weathering under a range of realistic simulated tropical wet season conditions produces a significant degree of schist particle breakdown. The fragmentation of the schist is characterized by splitting of the larger fragments into mid-sized product with finer material produced, possibly from the breakdown of mid-sized fragments when weathering is more advanced. Salinity, the salt addition method and temperature were all found to affect weathering rates. Subtle differences in mineralogy also produce variations in weathering patterns and rates. It is also shown that an increase in drying temperature leads to accelerated weathering rates, however, the geometry of the fracture process is not significantly affected. Copyright © 2006 John Wiley & Sons, Ltd. [source] Mineral soil surface crusts and wind and water erosionEARTH SURFACE PROCESSES AND LANDFORMS, Issue 9 2004Michael J. Singer Abstract The ,rst few millimetres of soil largely control the soil's response to the eroding forces of wind and water. The tendency of soils to form surface seals and crusts in,uences the processes of wind and water erosion differently. For wind, dry particle size distribution and particle organization determine the shear strength and threshold wind velocity necessary to initiate particle movement. In loams and clay loams, seals and crusts decrease roughness but increase surface soil strength, generally decreasing wind erosion. Conversely, in sand and sandy loams, loose erodible sandy material may either deposit on the crust and is subject to erosion or it may disrupt the crust, accelerating the erosion process. For water erosion, particle size distribution and structure determine in,ltration rate, time to ponding, and energy required for soil particle detachment. Seals and crusts tend to decrease in,ltration rate and time to ponding thus increasing overland ,ow and soil erosion. This paper brie,y reviews how permanent and time-dependent soil properties in,uence surface seals and crusts and how these affect soil erosion by wind and water. The tendency of a soil to form a seal and crust depends to some degree on the time-dependent property of soil structural stability, which tends to increase with increasing clay content and smectitic mineralogy which are permanent properties. These permanent properties and their effect on structure are variable depending on dynamic properties of exchangeable sodium percentage and soil solution electrical conductivity. Antecedent water content prior to irrigation or rainfall, rate of wetting before an erosive event and aging, the time between wetting and an erosive event, greatly in,uence the response of soil structure to raindrop impact. The effect of these dynamic processes is further in,uenced by the static and dynamic properties of the soil. Weak structure will be less in,uenced by wetting rate than will a soil with strong structure. Process-based models of wind and water erosion need to consider the details of the interactions between soil static and dynamic properties and the dynamic processes that occur prior to erosive events. Copyright © 2004 John Wiley & Sons, Ltd. [source] Indigestibility of plant cell wall by the Australian plague locust, Chortoicetes terminiferaENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 3 2004F.J. Clissold Abstract The plant cell wall may play an important role in defence against herbivores since it can be both a barrier to, and nutrient diluter of, the easily digested cell contents. The aim of this study was to investigate the digestibility of the cell wall of three grasses, Triticum aestivum L., Dactyloctenium radulans (R. Br.) Beauv., and Astrebla lappacea (Lindl.) Domin, by the Australian plague locust, Chortoicetes terminifera Walker (Orthoptera: Acrididae, Acridinae) as determined by the Van Soest method [Van Soest PJ, Robertson JB & Lewis BA (1991) Methods for dietary fiber, neutral detergent fiber, and nonstarch polysaccharides in relation to animal nutrition. Journal of Dairy Science 74: 3583,3597]. Determination of plant cell wall digestion by locusts required a precise methodological procedure to determine both the exact intake and the concentration of cell wall in the diet and the faeces. Plant cell wall determination is affected by the particle size distribution of the dried plant material. All three grasses differed in the percentage of cell wall per gram dry matter and the proportions of hemicellulose, cellulose, and acid-detergent sulphuric lignin within the cell wall. The locust was unable to digest the cell wall of any of the grasses. Thus, plant cell walls are a mechanical barrier hindering locusts assimilating nutrients. That is, access, rather than nutrient concentration per se, may be limiting nutrient factor. [source] Zeolite synthesis employing alkaline waste effluents from the aluminum industryENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 2 2002A. La Iglesia Zeolites 4A, 13X, Y, and HZSM5 have been synthesized from alkaline residues from aluminum finishing plants. These residues could contain concentrations of sodium aluminate and sodium hydroxide between 200 and 300 Kg/m3, and small concentrations of heavy metal cations (Cd, Co, Cr, Cu, Mn, and Zn). These contaminants make handling and disposal of these residues difficult. However, the physicochemical properties of the synthesized zeolites (cation exchange capacity of 3 mmol g,1, specific surface area between 600,900 m2g,1, particle size distribution between 0.5,2 ,m and whiteness of 97%) make them useful as detergents and catalysts. Analysis of the chemical composition of the raw materials and the reaction products demonstrates that the heavy metal cation content in the synthesized zeolites is low enough to allow their industrial use (lower than that of the original residues). Therefore, the production of various types of zeolites for industrial use could be used for the elimination of these residues from the aluminum industry. [source] Silver Nanoparticles with Controlled Dispersity and Their Assembly into SuperstructuresADVANCED ENGINEERING MATERIALS, Issue 5 2010Karsten Moh In this paper we report on the influence of particle size distribution, particle substrate interaction, and drying behavior on the self-assembly process using ligand stabilized silver particles. Two-dimensional particle arrays were characterized using transmission electron microscopy and extensive image analysis. The formation of such structures was observed in situ using an environmental scanning electron microscope in WET-STEM mode. The results confirm that a small particle size distribution is crucial for the formation of regular particle patterns with long range order, but also the particle substrate interaction and the particle density have an influence on the degree of ordering. Additionally, we find that separated binary particle assemblies keep the orientation of their two-dimensional hexagonal lattices over alternating domains of small and big particles. This is probably enabled due to the formation of dislocations and a small change of the course of the lattice lines within the respective boundary. [source] Primary particle size distribution of eroded material affected by degree of aggregate slaking and seal developmentEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 1 2009D. N. Warrington Summary Primary particle size distribution (PSD) of eroded sediment can be used to estimate potential nutrient losses from soil and pollution hazards to the environment. We studied eroded sediment PSDs from three saturated soils, packed in trays (20 × 40 × 4 cm), that had undergone either minimal aggregate slaking (MAS) or severe aggregate slaking (SAS) prior to a 60 mm simulated rainstorm (kinetic energy, 15.9 kJ m,3; droplet diameter, 2.97 mm) and collected runoff at regular intervals. The degree of aggregate slaking was controlled by the rate at which soils were wetted to saturation. The PSDs of eroded materials and of parent soils were determined using a laser particle size analyser. For each soil, PSD frequency curves of eroded sediments and parent soils were generally of a similar shape but most eroded sediments had larger clay contents than their parent soils. In the SAS treatment, cumulative clay enrichment in the eroded materials was inversely related to the parent soil clay content, these being 28.5, 26.6 and 22.8% richer in clay than their parent soils for the loam, sandy clay and clay, respectively. Generally, total clay loss was greater from soils with SAS than from those with MAS because of erosion rates; however, clay enrichment of sediments, compared with parent soil clay contents, was mostly greater in samples with MAS. Greater clay enrichment took place during the early seal development stage in the loam, but could not readily be associated with specific stages of seal development for the clay. In the sandy clay, the relation between seal development and clay enrichment in the eroded material depended on the initial degree of aggregate slaking. The observed large preferential loss of clay by erosion in cultivated soils re-emphasizes the need to employ erosion control measures. [source] MEL-type Pure-Silica Zeolite Nanocrystals Prepared by an Evaporation-Assisted Two-Stage Synthesis Method as Ultra-Low- k Materials,ADVANCED FUNCTIONAL MATERIALS, Issue 12 2008Yan Liu Abstract A MEL-type pure-silica zeolite (PSZ), prepared by spin-on of nanoparticle suspensions, has been shown to be a promising ultra-low-dielectric-constant (k) material because of its high mechanical strength, hydrophobicity, and chemical stability. In our previous works, a two-stage synthesis method was used to synthesize a MEL-zeolite nanoparticle suspension, in which both nanocrystal yield and particle size of the zeolite suspension increased with increasing synthesis time. For instance, at a crystal yield of 63%, the particle size is 80,nm, which has proved to be too large because it introduces a number of problems for the spin-on films, including large surface roughness, surface striations, and large mesopores. In the current study, the two-stage synthesis method is modified into an evaporation-assisted two-stage method by adding a solvent-evaporation process between the two thermal-treatment steps. The modified method can yield much smaller particle sizes (e.g., 14,vs. 80,nm) while maintaining the same nanocrystal yields as the two-stage synthesis. Furthermore, the nanoparticle suspensions from the evaporation-assisted two-stage synthesis show a bimodal particle size distribution. The primary nanoparticles are around 14,nm in size and are stable in the final suspension with 60% solvent evaporation. The factors that affect nanocrystal synthesis are discussed, including the concentration, pH value, and viscosity. Spin-on films prepared by using suspensions synthesized this way have no striations and improved elastic modulus (9.67,±,1.48,GPa vs. 7.82,±,1.30,GPa), as well as a similar k value (1.91,±,0.09 vs. 1.89,±,0.08) to the previous two-stage synthesized films. [source] First-year post-fire erosion rates in Bitterroot National Forest, Montana,HYDROLOGICAL PROCESSES, Issue 8 2007Kevin M. Spigel Abstract Accelerated runoff and erosion commonly occur following forest fires due to combustion of protective forest floor material, which results in bare soil being exposed to overland flow and raindrop impact, as well as water repellent soil conditions. After the 2000 Valley Complex Fires in the Bitterroot National Forest of west-central Montana, four sets of six hillslope plots were established to measure first-year post-wildfire erosion rates on steep slopes (greater than 50%) that had burned with high severity. Silt fences were installed at the base of each plot to trap eroded sediment from a contributing area of 100 m2. Rain gauges were installed to correlate rain event characteristics to the event sediment yield. After each sediment-producing rain event, the collected sediment was removed from the silt fence and weighed on site, and a sub-sample taken to determine dry weight, particle size distribution, organic matter content, and nutrient content of the eroded material. Rainfall intensity was the only significant factor in determining post-fire erosion rates from individual storm events. Short duration, high intensity thunderstorms with a maximum 10-min rainfall intensity of 75 mm h,1 caused the highest erosion rates (greater than 20 t ha,1). Long duration, low intensity rains produced little erosion (less than 0·01 t ha,1). Total C and N in the collected sediment varied directly with the organic matter; because the collected sediment was mostly mineral soil, the C and N content was small. Minimal amounts of Mg, Ca, and K were detected in the eroded sediments. The mean annual erosion rate predicted by Disturbed WEPP (Water Erosion Prediction Project) was 15% less than the mean annual erosion rate measured, which is within the accuracy range of the model. Published in 2007 by John Wiley & Sons, Ltd. [source] New Design of a Ceramic Filter for Diesel Emission Control ApplicationsINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 6 2005Aleksander J. Pyzik Diesel particulate filters (DPF) made from an advanced ceramic material (ACM) based on mullite have demonstrated high filtration efficiency, low-pressure drop, high-temperature handling capability, and excellent mechanical integrity at a porosity of 60% or higher. Due to the ability to control microstructure, total porosity, and particle size distribution, Dow's acicular mullite can be tailored to meet requirements for deep bed filtration and fine particles emission control. In addition, the ACM DPF is suitable for catalyzed applications and it can retain its performance with a broad range of catalysts and over a wide range of catalyst loadings. This study describes a material selected for a DPF design that meets current diesel particulate emission control requirements as well as a four-way NOx control system. [source] Microstructure and mechanical properties related to particle size distribution and composition in dark chocolateINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 1 2009Emmanuel Ohene Afoakwa Summary Composition in dark chocolate was varied and the effects determined on microstructure, using light microscopy, and mechanical properties of molten and tempered chocolates, using a TA.HD Plus Texture Analyser. Compositional parameters were particle size distribution (PSD) (D90 of 18, 25, 35 and 50 ,m), fat (25%, 30% and 35%) and lecithin (0.3% and 0.5%) contents. Micrographs revealed wide variations in sugar crystalline network structure and inter-particle interaction strengths related to PSD and fat level. Samples containing 25% fat had more crystal agglomerates, well flocculated with greater particle-to-particle interaction strengths than those with higher (30% and 35%) fat contents. Increasing the D90 to 35,50 ,m caused broadening of the PSD, with particles becoming coarser, which were similar at all fat levels. Mechanical analysis showed that PSD, fat and lecithin content significantly influenced firmness of molten chocolate and hardness of solid (tempered) chocolate with significant interactions among factors. Particle size was inversely correlated with firmness (1235,173 g) and hardness (7062,5546 g). Greatest effect of PSD was with 25% fat and 0.3% lecithin. With higher fat and lecithin contents, the PSD influence was reduced. It was concluded that PSD, fat and lecithin contents and their interactions were central to mechanical properties of dark chocolates. [source] Synthesis and characterization of uniform-sized hollow chitosan microspheresADVANCES IN POLYMER TECHNOLOGY, Issue 1 2009Shan Wang Abstract Hollow chitosan (CS) microspheres were obtained using an inverse-emulsion crosslinking method. The temperature and viscosity of the CS emulsion affected the characteristics of the derived microspheres. The microspheres were characterized by differential scanning calorimetry, Fourier transform infrared (FT-IR) spectroscopy, transmission electron microscopy, optical microscopy, scanning electron microscopy (SEM), and laser particle size analysis. FT-IR indicated the sequence of transformations taking place before, during, and after the crosslinking of CS. Optical microscopy and SEM confirmed the spherical morphology of the gel. The formation of hollow microspheres with a single cavity was identified by SEM. The CS microspheres exhibited a narrow particle size distribution. Furthermore, particle size could be controlled by changing the stirring speed. © 2009 Wiley Periodicals, Inc. Adv Polym Techn 28:40,47, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20145 [source] Analysis of scattering from polydisperse structure using Mellin convolutionJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 2 2006Norbert Stribeck This study extends a mathematical concept for the description of heterogeneity and polydispersity in the structure of materials to multiple dimensions. In one dimension, the description of heterogeneity by means of Mellin convolution is well known. In several papers by the author, the method has been applied to the analysis of data from materials with one-dimensional structure (layer stacks or fibrils along their principal axis). According to this concept, heterogeneous structures built from polydisperse ensembles of structural units are advantageously described by the Mellin convolution of a representative template structure with the size distribution of the templates. Hence, the polydisperse ensemble of similar structural units is generated by superposition of dilated templates. This approach is particularly attractive considering the advantageous mathematical properties enjoyed by the Mellin convolution. Thus, average particle size, and width and skewness of the particle size distribution can be determined from scattering data without the need to model the size distributions themselves. The present theoretical treatment demonstrates that the concept is generally extensible to dilation in multiple dimensions. Moreover, in an analogous manner, a representative cluster of correlated particles (e.g. layer stacks or microfibrils) can be considered as a template on a higher level. Polydispersity of such clusters is, again, described by subjecting the template structure to the generalized Mellin convolution. The proposed theory leads to a simple pathway for the quantitative determination of polydispersity and heterogeneity parameters. Consistency with the established theoretical approach of polydispersity in scattering theory is demonstrated. The method is applied to the best advantage in the field of soft condensed matter when anisotropic nanostructured materials are to be characterized by means of small-angle scattering (SAXS, USAXS, SANS). [source] Particle size distributions from small-angle scattering using global scattering functionsJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 4 2004G. Beaucage Control and quantification of particle size distribution is of importance in the application of nanoscale particles. For this reason, polydispersity in particle size has been the focus of many simulations of particle growth, especially for nanoparticles synthesized from aerosols such as fumed silica, titania and alumina. Single-source aerosols typically result in close to a log-normal distribution in size and micrograph evidence generally supports close to spherical particles, making such particles ideal candidates for considerations of polydispersity. Small-angle X-ray scattering (SAXS) is often used to measure particle size in terms of the radius of gyration, Rg, using Guinier's law, as well as particle surface area, S/V, from the Porod constant B and the scattering invariant Q. In this paper, the unified function is used to obtain these parameters and various moments of the particle size distribution are calculated. The particle size obtained from BET analysis of gas adsorption data directly agrees with the moment calculated from S/V. Scattering results are also compared with TEM particle-counting results. The potential of scattering to distinguish between polydisperse single particles and polydisperse particles in aggregates is presented. A generalized index of polydispersity for symmetric particles, PDI = BRg4/(1.62G), where G is the Guinier prefactor, is introduced and compared with other approaches to describe particle size distributions in SAXS, specifically the maximum-entropy method. [source] The microencapsulation of terbinafine via in situ polymerization of melamine-formaldehyde and their application to cotton fabricJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010Gökhan Erkan Abstract In this study an antifungal pharmaceutical agent, terbinafine, was microencapsulated by using in situ polymerization. The polymerization was carried out at four mole ratio level and preparations were applied to the 100% cotton fabric. X-ray diffractometry, DSC, FTIR, BET, contact angle measurements, particle size distribution and imaging techniques were performed. Best results were obtained in the case of 8 : 1 mole ratio. Strength of microcapsule applied fabrics to washing and fungus were also determined. After 25 washing cycle, microcapsules were still in the fabric and had antifungal properties against A. niger. Antifungal strength against T. rubrum was observed up to 15 washing cycles. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] | ||||||||||||||||||||||||||||||||||||||||