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Particle Deposition (particle + deposition)
Selected AbstractsParticle deposition indoors: a reviewINDOOR AIR, Issue 4 2002A. C. K. Lai First page of article [source] Groutability of cement-based grout with consideration of viscosity and filtration phenomenonINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 16 2009Jong-Sun Kim Abstract The groutability depends on the properties of the grout, its injection processes, and on the mechanical properties of the soil formation. During the process of pouring cement-based grouting into a porous medium, a variation with time occurs in the viscosity of grout suspension. In addition, the particle filtration phenomenon will limit the expansion of the grouted zone because cement particles are progressively stagnant within the soil matrix. In this paper, a closed-form solution was derived by implementing the mass balance equations and the generalized phenomenological filtration law, which can be used to evaluate the deposition of cement-based grout in the soil matrix. The closed-form solution relevant to a particular spherical flow was modified by a step-wise numerical calculation, considering the variable viscosity caused by a chemical reaction, and the decrease in porosity resulting from grout particle deposition in the soil pores. A series of pilot-scale chamber injection tests was performed to verify that the developed step-wise numerical calculation is able to evaluate the injectable volume of grout and the deposition of grout particles. The results of the chamber injection tests concurred well with that of the step-wise numerical calculation. Based on the filtration phenomenon, a viable approach for estimating the groutability of cement-based grout in a porous medium was also suggested, which might facilitate a new insight in the design of the grouting process. Copyright © 2009 John Wiley & Sons, Ltd. [source] Electric field controlled electrospray deposition for precise particle pattern and cell pattern formationAICHE JOURNAL, Issue 10 2010Jingwei Xie Abstract Photolithography, soft lithography, and ink jetting have been used for automated micropattern fabrication. However, most of the methods for microfabrication of surface pattern are limited to the investigation of material properties of substrates with high-cost and complex procedures. In the present study, we show a simple (single-step) yet versatile and robust approach to generate biodegradable polymeric particle patterns on a substrate using electrospray deposition through a mask. Various particle patterns including patterned dots, circles, squares, and bands can be easily formed and the features of particle patterns could also be tailored using different masks and electrostatic focusing effects. Furthermore, cell patterns can be achieved on the surface of particle patterns by blocking the areas without particle deposition on the substrate and culturing cells on the substrate. Polymeric particle patterns and cell patterns developed in this study could be used in the high throughput screening of sustained release formulations, cell-based sensing, and drug discovery. In addition to experimental results, an analysis of the associated electric field is used to investigate quantitatively the nature of focusing effect. Scaling analysis is also applied to obtain the dominate terms in electrospray deposition process. © 2010 American Institute of Chemical Engineers AIChE J, 2010 [source] Correlation equation for predicting filter coefficient under unfavorable deposition conditionsAICHE JOURNAL, Issue 5 2008You-Im Chang Abstract A new correlation equation for predicting the filter coefficient under unfavorable deposition conditions is presented. By adopting the triangular network model of using the Brownian dynamic simulation method, as the sum of four individual deposition mechanisms, e.g., the Brownian diffusion, the DLVO interactions, the gravitational force, and the interception, the correlation equation is obtained by regressing against a broad range of parameter values governing particle deposition in deep bed filtration. The new correlation equation is able to describe previous experimental results well, especially for those submicro particles with significant Brownian motion behavior. © 2008 American Institute of Chemical Engineers AIChE J, 2008 [source] Direct drug loading into preformed porous solid dosage units by the controlled particle deposition (CPD), a new concept for improved dissolution using SCF-technologyJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 10 2008Ragna S. Wischumerski Abstract The controlled particle deposition (CPD), a supercritical fluid precipitation process, is used to load porous tablets with ibuprofen to improve drug dissolution. Porous tablets (porosity 44.3,±,5.5%), consisting of microcrystalline cellulose pellets and hydroxyethylcellulose, or sugar cubes (porosity 37.2,±,0.5%), are used as carrier material. Loading experiments are conducted at 313 K and 25 MPa, drug concentrations between 6.25 and 33.3 mg ibuprofen/mL supercritical carbon dioxide and contact times of 15.5 h or 5 min. The resulting products have drug contents of 3,5 g ibuprofen/mL void volume in the carrier. Comparison of a predicted value, calculated from pore volume and loading concentration to the actual drug concentrations yielded by the loading process demonstrates the efficiency and controllability of the process. The mean particle size d50 of deposited ibuprofen is around 25 µm, half the size of the starting material. Drug dissolution from loaded carriers is significantly increased by a rise in the dissolution coefficient from 0.07 min,1 for the starting material to 0.13 or 0.14 min,1 for the CPD products. The CPD method therefore is presented as a feasible and controllable process to load porous solid dosage forms with drug particles in order to improve dissolution. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:4416,4424, 2008 [source] Electrostatics of pharmaceutical inhalation aerosolsJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 12 2009Philip Chi Lip Kwok Abstract Objectives This review focuses on the key findings and developments in the rapidly expanding research area of pharmaceutical aerosol electrostatics. Key findings Data from limited in-vivo and computational studies suggest that charges may potentially affect particle deposition in the airways. Charging occurs naturally in the absence of electric fields through triboelectrification, that is contact or friction for solids and flowing or spraying for liquids. Thus, particles and droplets emitted from pulmonary drug delivery devices (dry powder inhalers, metered dose inhalers with or without spacers, and nebulisers) are inherently charged. Apparatus with various operation principles have been employed in the measurement of pharmaceutical charges. Aerosol charges are dependent on many physicochemical parameters, such as formulation composition, device construction, relative humidity and solid-state properties. In some devices, electrification has been purposefully applied to facilitate powder dispersion and liquid atomisation. Summary Currently, there are no regulatory requirements on characterising electrostatic properties of inhalation aerosols. As research in this area progresses, the new knowledge gained may become valuable for the development and regulation of inhalation aerosol products. [source] Tissue distribution of radioactivity following intranasal administration of radioactive microspheresJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 5 2001J. E. Eyles The aim of this study was to increase understanding of the kinetics of microparticle distribution and elimination following intranasal application. To do this we investigated the in-vivo distribution of radioactivity following intranasal instillation of scandium-46 labelled styrene-divinyl benzene 7-,m-diameter microspheres. Groups of BALB/c mice received 0.250 mg (47.5 kBq) particles suspended in either 50-,l or 10-,l volumes of phosphate buffered saline. The in-vivo distribution of radioactivity was influenced by the volume of liquid that was used to instil the microsphere suspension. Comparatively large (50 ,l) administration vehicle volumes resulted in substantial bronchopulmonary deposition (, 50% of administered dose). Intranasal instillation of microspheres suspended in 10-,l volumes tended to restrict particle deposition initially to the nasal cavity. For both administration vehicle volumes tested, the radioactivity per unit mass of excised nasal-associated lymphoid tissue (NALT) was found to be consistently elevated relative to other tissues. This corroborates the findings of other workers who have previously identified NALT as an active site of microparticle accumulation following intranasal application. Elimination via the alimentary canal was the principal fate of intranasally applied radiolabeled material. No significant concentration of radioactivity within excised gut-associated lymphoid tissue (GALT) (Peyer's patches) was noted. At latter time points we observed, in mice that received the 50-,l volume particle suspension nasally, accumulation of potentially relevant quantities of radioactivity in the liver (0.3% after 576 h) and spleen (0.04% after 576 h). Thus, our data corroborate the notion that epithelial membranes in the lung are probably less exclusive to the entry of microparticulates into systemic compartments than are those mucosae in the gastrointestinal tract or nasopharynx. This effect may contribute to the effectiveness of pulmonary delivered antigen-loaded microparticles as humoral immunogens. [source] Nanosized Diamond Deposition via Plasma MediumPLASMA PROCESSES AND POLYMERS, Issue S1 2007Babak Shokri Abstract An arc jet plasma technique is used to produce nanosized diamond particle deposition and for the deposition of diamond-like carbon at high growth rates. In this case, atomic hydrogen produced in the arc plasma participates in the methane decomposition. In addition, a thermodynamic modeling will be presented for the nucleation of stable diamond as nanoparticles and thin films and the computation was made in the range of the applied plasma reactor. [source] Forced Alveolar Flows and Mixing in the LungPROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2009David Borer The air flows deep inside the lung are not only important in gas exchange processes but they also determine the efficiency of particle deposition and retention. The study aims at quantifying the relative influence of different flow components in the transport of small particles in alveolar geometries such as convective breathing patterns, wall movement, gravitational settling and Brownian motion. In addition, the possibility and efficiency of external forcing is studied, relying on the mechanism of internal acoustic streaming. A viscous oscillating boundary layer flow is converted into a steady, viscosity-independent bulk motion which is very efficient at low Reynolds numbers. The streaming can be controlled by external parameters (excitation amplitude, frequency, beam shape) and may thus be of diagnostic and therapeutic relevance. Numerical simulations are performed to analyze the flow patterns in 3D model geometries and to measure deposition rates. (© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Numerical simulation of flow and heat transfer in connection of gasifier to the radiant syngas coolerASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2009Jianjun Ni Abstract The connection of gasifier to the radiant syngas cooler has been regarded as a key technology for heat recovery system. Multiphase flow and heat transfer processes presented in this work considers particle deposition and radiation model to mixture of non-gray gas with particles. An axisymmetric simulation of the multiphase flow in an industrial scale connection is performed. The standard k -, model, Renormalization group (RNG) k -, model and Realizable k -, model turbulence model are proposed. The particle motion is modeled by discrete random walk model. The discrete ordinates model (DOM), P-1 and discrete transfer model (DTRM) are used to model the radiative heat transfer. The effect of particles on the radiative heat transfer was taken into account when the DOM and P-1 model were used. The absorption coefficient of the gas mixture is calculated by means of a weighted-sum-of-gray-gas (WSGG) model. The results with the DOM and P-1 model are very similar and close to practical condition. A large number of particles are deposited on the cone of gasifier which is the top of connection. Maximum temperature difference is approximate 7 K when the cooling tube heights change from 0.5 m to 1.5 m. The temperature inside has a linear relationship with operating temperature. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Fluid Mechanics, Cell Distribution, and Environment in Cell Cube BioreactorsBIOTECHNOLOGY PROGRESS, Issue 1 2003John G. Auni Cultivation of MRC-5 cells and attenuated hepatitis A virus (HAV) for the production of VAQTA, an inactivated HAV vaccine ( 1), is performed in the Cell Cube reactor, a laminar flow fixed-bed bioreactor with an unusual diamond-shaped, diverging-converging flow geometry. These disposable bioreactors have found some popularity for the production of cells and gene therapy vectors at intermediate scales of operation ( 2, 3). Early testing of the Cell Cube revealed that the fluid mechanical environment played a significant role in nonuniform cell distribution patterns generated during the cell growth phase. Specifically, the reactor geometry and manufacturing artifacts, in combination with certain inoculum practices and circulation flow rates, can create cell growth behavior that is not simply explained. Via experimentation and computational fluid dynamics simulations we can account for practically all of the observed cell growth behavior, which appears to be due to a complex mixture of flow distribution, particle deposition under gravity, fluid shear, and possibly nutritional microenvironment. [source] Toward Quantifying the Relative Importance of Invertebrate Consumption and Bioturbation in Puerto Rican StreamsBIOTROPICA, Issue 4 2008Wyatt. ABSTRACT Although many tropical stream consumers have large effects on resource quantity and quality, little is known about the relative importance of consumption versus bioturbation. We quantified egestion rates of freshwater shrimps (Atya spp. and Xiphocaris elongata) and mayflies (Leptophlebiidae) in two forest streams within the Luquillo Experimental Forest, Puerto Rico. Consumer body size was a strong predictor of egestion rates, with mass-specific egestion rates declining with body size and per-individual egestion rates increasing with body size. We used these egestion rates, together with published rates of epilithon removal by consumers and epilithon accrual by particle deposition and periphytic growth (i.e., with and without consumer access), to estimate the importance of consumption and bioturbation after storm events and during base-flow conditions. Our estimates suggest that direct consumption of epilithon can only account for a minor proportion (< 5%) of material removed following storm events, with most removal likely resulting from bioturbation. During base-flow conditions, we found that consumers (largely shrimps) may be capable of consuming a significant proportion of the material that would otherwise accrue on benthic substrata, but this result was limited to one high-elevation site. Our study suggests that bioturbation is the dominant process that redistributes and entrains fine particles after storm events, and that a variable fraction of deposited and accrued benthic material may be consumed during base-flow conditions. Our results underscore the importance of tropical stream animals in altering the benthic environment through both consumption and bioturbation, and suggest that consumer-mediated material cycling is likely to be context dependent. RESUMEN A pesar de que muchos de los consumidores en ríos tropicales tienen grandes efectos en la cantidad y calidad de los recursos, se sabe poco sobre la importancia relativa del consumo y los biodisturbios. Por ello, cuantificamos las tasas de egestión de los camarones (Atya spp. y Xiphocaris elongata) y los efemerópteros (Leptophlebiidae) en dos quebradas dentro del Bosque Experimental de Luquillo, Puerto Rico. El tamaño corporal de los consumidores fue un buen indicador de las tasas de egestión, y las tasas de egestión por masa disminuyeron con el tamaño corporal y las por individuo aumentaron con el tamaño corporal. Usamos estas tasas de egestión, junto con tasa publicadas de remoción de perifiton por los consumidores y acumulación de epiliton por la deposición y el crecimiento de perifiton (ej. con y sin consumidores), para estimar la importancia del consumo y los biodisturbios luego de tormentas y durante condiciones de flujo basal. Nuestros resultados sugieren que el consumo directo de epiliton representa una proporción menor (< 5%) del material removido luego de las tormentas, la mayor parte de la remoción es probablemente el resultado de los biodisturbios. Durante condiciones de flujo basal, encontramos que los consumidores (mayormente camarones) pueden ser capaces de consumir una proporción importante del material que de otra forma se acumularía sobre el substrato béntico, pero este resultado se limita a uno solo de los sitios. Nuestro estudio sugiere que los biodisturbios son el proceso que predomina en la redistribución y mueve partículas luego de las tormentas, y que una fracción variable del material béntico depositado y acumulado puede ser consumida durante condiciones de flujo basal. Nuestros resultados enfatizan la importancia de los animales en alterar el ambiente béntico de los ríos tropicales a través del consumo y los biodisturbios, y sugiere que el reciclaje de los materiales por los consumidores es un proceso que probablemente depende del contexto. [source] Study on flow patterns in different types of direct coal liquefaction reactorsASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2009Xiangkun Ren Abstract Hot mold flow patterns in bubble reactor, ebullated reactor and loop reactor have been researched and compared in hydrogen,oil system and hydrogen,oil coal slurry system of direct coal liquefaction (DCL) pilot plant under high temperature and high pressure. The results demonstrate that the ebullated reactor and loop reactor (on the condition of optimum recycle ratio) show good performance of back-mixing, which can not only reduce temperature differences between top and bottom in the reactor, but also avoid big solid particles deposition that easily occurs during liquefaction process. The ebullated reactor used in the first demonstration plant has good performance. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] | ||||||||||||||||