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Granular Structure (granular + structure)
Selected AbstractsImplications of ideas on super-hydrophobicity for water repellent soilHYDROLOGICAL PROCESSES, Issue 17 2007G. McHale Abstract Water repellence is an important factor in soil erosion due to its role in inhibiting the re-establishment of vegetation after fire and due to its enhancement of run-off. Water repellence is studied across a range of diverse disciplines, such as chemistry, materials, textiles and soil and reclamation science. In recent years many basic studies of water repellence of materials have focused on the role of the sub-mm surface topography of a material in modifying the intrinsic hydrophobicity imparted by the surface chemistry to create super-hydrophobicity. In this report, we first illustrate the types of hydrophobic effects created by a suitable coupling of small scale surface topography with surface chemistry using three materials: an etched metal, a foam and a micro-fabricated pillar structure. These experiments demonstrate the general applicability of the ideas and suggest that they could apply to a granular material such as, a fine sandy soil, particularly when the grains have become coated with a hydrophobic layer. This applicability is confirmed by contact angle measurements of droplets of water on hydrophobic sand. A theoretical model describing the application of these ideas in a loose-packed, but regular, array of uniform spherical grains is then presented and discussed. When the grains are in a dry state initially, the effect of the surface is to increase the apparent water repellence as observed through the contact angle. However, when the spaces between the grains are filled with water, the effect is to provide greater wetting. To qualitatively confirm the enhancement of contact angle caused by the granular structure, model surfaces using 600 and 250 µm hydrophobic glass beads were created. On these surfaces, the contact angle of droplets of water was increased from 108° to 126° and 140° , respectively. Copyright © 2007 John Wiley & Sons, Ltd. [source] Microstructural deformation mechanisms of unsaturated granular soilsINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 5 2002J. A. Gili Abstract A discrete model for unsaturated granular soils has been developed. Three discrete entities have been defined: particles, water menisci and pores. Local interaction forces and water transfer mechanisms have been integrated into a model through the appropriate equilibrium and balance equations. The results of several numerical tests using this model have been described and discussed. Simulations include wetting and drying under load tests, the application of suction cycles and the effect of a deviatoric stress ratio on wetting-induced collapse. The model reacts just as true granular soil samples behave in laboratory tests. The model provides a new insight into the internal mechanisms leading to large-scale features of behaviour such as wetting-induced collapse or the increase in soil strength provided by suction. The paper also stresses that matric suction changes acting on a granular structure are capable of explaining most of the macroscopic features of stress,strain behaviour. Copyright © 2002 John Wiley & Sons, Ltd. [source] Geometrical modeling of granular structures in two and three dimensions.INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 4 2009Application to nanostructures Abstract A granular structure can be modeled by a parallelepiped containing spherical balls in three dimensions or by a rectangle filled with disks in two dimensions. These grains (spherical balls or disks) are separated by interfaces called grain boundaries and their size correspond to a size distribution, which is obtained experimentally. The geometrical modeling of such a structure consists in determining the repartition of the set of disjoint grains according to these specifications. In this paper, a new constructive algorithm based on an advancing-front approach, usually used in the context of mesh generation, is proposed. This algorithm is nearly linear in complexity, robust and fast in both two and three dimensions. Enhancements in computing time and density are observed and reported via comparisons with existing methods. Moreover, we propose a method to transform spherical balls (disks) into polyhedral (polygonal) cells similar to the real grain shapes. Examples of nanostructure modeling in two and three dimensions are presented. Copyright © 2009 John Wiley & Sons, Ltd. [source] The functional properties of popped, flaked, extruded and roller-dried foxtail millet (Setaria italica)INTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 9 2004Singh R. Ushakumari Summary Foxtail millet grains were decorticated in rice-milling machinery and the decorticated millet was processed to prepare flaked, extrusion cooked and roller-dried products, whereas the native grains were subjected to high-temperature, short-time treatment to prepare popped millet. The nutrient composition and some of the functional properties of the products were determined, principally solubility and swelling power in water, oil absorption capacity and pasting characteristics. Carbohydrate and lipid profiles of the products were also studied. The changes in the starch granular structure caused by heat treatment were examined by scanning electron microscopy. The degree of starch gelatinization was highest in the case of roller-dried millet followed by popped, flaked and extruded products. It was concluded that the cereal processing technologies that were investigated could be successfully applied to foxtail millet to prepare ready-to-eat or use products, thereby increasing its utilization as a food. [source] Synthesis of Nanotube Array Composed of an Amorphous Matrix Embedded with NaCl-Type SiC Crystallites by Chemical Vapor Infiltration TechniquesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2010Wen Yang Highly dense oriented arrays of nanotubes were synthesized via a chemical vapor infiltration process using anodic alumina membrane as a template. The nanotubes have a unique granular structure, which is composed of SiC nanocrystals embedded in an amorphous matrix. X-ray diffraction and high-resolution transmission electron microscopy examinations both indicate an NaCl-type crystalline structure of the SiC nanocrystals in the nanotubes. The process described here can be extended to the preparation of other nanomaterials that are suitable to be obtained via a vapor,solid approach. [source] Transport and Reaction Characteristics of Reconstructed Polyolefin ParticlesMACROMOLECULAR REACTION ENGINEERING, Issue 6 2008Libor Seda Abstract The 3D spatial structure of porous polyethylene particles was reconstructed from their X-ray micro-tomography images. Several polyolefin particles with an artificial granular structure were generated. Transport in reconstructed particles was calculated for the case of a monomer diffusing through both the pores and the polymer. The calculated degassing characteristics of reconstructed polyolefin particles can be compared to experiments. Monomer mass transport limitations are important not only in the early stage of particle growth, but also in fully-developed polyolefin particles. The problems and limitations of the developed method are discussed. The method developed allows prediction of the effect of particle structure on mass transport limitations for real particle structures. [source] Magnetoresistance, transport noise and granular structure in polycrystalline superconductorsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 3 2007I. García-Fornaris Abstract In this work we present a theoretical study on the magnetic field dependence of the electrical resistance R (Ba) and the transport noise (TN) in a high- Tc polycrystalline superconductors. In the model, we have considered the ceramic superconductor as a series-parallel array of Josephson devices and the intergranular magnetic field is described within the framework of the intragranular flux-trapping model. The obtained results qualitatively reproduce the hysteretic behavior of the R (Ba) dependence in increasing and decreasing applied magnetic fields. We have found that the hysteretic behavior in the R (Ba) dependence changes appreciably if different statistical distributions of the geometric factors of grains are used. In addition, such changes are also reflected in the TN, which is produced by the electric current rearrangement in the array with increasing applied magnetic fields. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Ultrasound pretreatment of cassava chip slurry to enhance sugar release for subsequent ethanol productionBIOTECHNOLOGY & BIOENGINEERING, Issue 3 2008Saoharit Nitayavardhana Abstract The use of ultrasound pretreatment to enhance liquefaction and saccharification of cassava chips was investigated. Cassava chip slurry samples were subjected to sonication for 10,40 s at three power levels of low (2 W/mL), medium (5 W/mL), and high (8 W/mL). The samples were simultaneously exposed to enzymes to convert starch into glucose. The cassava particle size declined nearly 40-fold following ultrasonic pretreatment at high power input. Scanning electron micrographs of both unsonicated (control) and sonicated samples showed disruption of fibrous material in cassava chips but did not affect the granular structure of starch. Reducing sugar release improved in direct proportion to the power input and sonication time. The reducing sugar increase was as much as 180% with respect to the control groups. The slurry samples with enzyme addition during sonication resulted in better reducing sugar release than the samples with enzyme addition after sonication. The heat generated during sonication below starch gelatinization temperature apparently had no effect on the reducing sugar release. The reducing sugar yield and energy efficiency of ultrasound pretreated samples increased with total solids (TS) contents. The highest reducing sugar yield of 22 g/100 g of sample and efficiency of 323% were obtained for cassava slurry with 25% TS at high power. The reducing sugar yield at the completion of reaction (R,) were over twofold higher compared to the control groups. The integration of ultrasound into a cassava-based ethanol plant may significantly improve the overall ethanol yield. Biotechnol. Bioeng. 2008;101: 487,496. © 2008 Wiley Periodicals, Inc. [source] Geometrical modeling of granular structures in two and three dimensions.INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 4 2009Application to nanostructures Abstract A granular structure can be modeled by a parallelepiped containing spherical balls in three dimensions or by a rectangle filled with disks in two dimensions. These grains (spherical balls or disks) are separated by interfaces called grain boundaries and their size correspond to a size distribution, which is obtained experimentally. The geometrical modeling of such a structure consists in determining the repartition of the set of disjoint grains according to these specifications. In this paper, a new constructive algorithm based on an advancing-front approach, usually used in the context of mesh generation, is proposed. This algorithm is nearly linear in complexity, robust and fast in both two and three dimensions. Enhancements in computing time and density are observed and reported via comparisons with existing methods. Moreover, we propose a method to transform spherical balls (disks) into polyhedral (polygonal) cells similar to the real grain shapes. Examples of nanostructure modeling in two and three dimensions are presented. Copyright © 2009 John Wiley & Sons, Ltd. [source] Increased dopamine and its metabolites in SH-SY5Y neuroblastoma cells that express tyrosinaseJOURNAL OF NEUROCHEMISTRY, Issue 2 2003Takafumi Hasegawa Abstract Oxidized metabolites of dopamine, known as dopamine quinone derivatives, are thought to play a pivotal role in the degeneration of dopaminergic neurons. Although such quinone derivatives are usually produced via the autoxidation of catecholamines, tyrosinase, which is a key enzyme in melanin biosynthesis via the production of DOPA and subsequent molecules, may potentially accelerate the induction of catecholamine quinone derivatives by its oxidase activity. In the present study, we developed neuronal cell lines in which the expression of human tyrosinase was inducible. Overexpression of tyrosinase in cultured cell lines resulted in (i) increased intracellular dopamine content; (ii) induction of oxidase activity not only for DOPA but also for dopamine; (iii) formation of melanin pigments in cell soma; and (iv) increased intracellular reactive oxygen species. Interestingly, the expressed tyrosinase protein was initially distributed in the entire cytoplasm and then accumulated to form catecholamine-positive granular structures by 3 days after the induction. The granular structures consisted of numerous rounded, dark bodies of melanin pigments and were largely coincident with the distribution of lysosomes. This cellular model that exhibits increased dopamine production will provide a useful tool for detailed analyses of the potentially noxious effects of oxidized catecholamine metabolites. [source] Activation of MKK6, an upstream activator of p38, in Alzheimer's diseaseJOURNAL OF NEUROCHEMISTRY, Issue 2 2001Xiongwei Zhu Mitogen-activated protein kinase (MAPK) p38 has been implicated in the pathogenesis of Alzheimer's disease, but the upstream cascade leading to p38 activation has not been elucidated in the disease. In the present study, we focused on mitogen-activated protein kinase kinase 6 (MKK6), one of the upstream activators of p38 MAPK. We found that MKK6 was not only increased but also specifically associated with granular structures in the susceptible neurons in the hippocampus and cortex of Alzheimer's disease patients, but was only weakly diffuse in the cytoplasm in neurons in control cases. Immunoblot analysis demonstrated a significant increase of MKK6 level in Alzheimer's disease compared with age-matched controls. In this regard, in hippocampal and cortical regions of individuals with Alzheimer's disease, the activated phospho-MKK6 was localized exclusively in association with pathological alterations including neurofibrillary tangles, senile plaques, neuropil threads and granular structures, overlapping with activated p38 MAPK suggesting both a functional and mechanic link. By immunoblot analysis, phospho-MKK6 is also significantly increased in AD compared with control cases. Together, these findings lend further credence to the notion that the p38 MAPK pathway is dysregulated in Alzheimer's disease and also indicates an active role for this pathway in disease pathogenesis. [source] Identification of an aging-related spherical inclusion in the human brainPATHOLOGY INTERNATIONAL, Issue 10 2002Takemi Kimura Inclusions, such as corpora amylacea, axonal spheroids and ubiquitin-positive granular structures, are present in aged brains. We found a phosphorylated tau-positive inclusion in brain tissues obtained from 13 non-demented subjects and five patients with Alzheimer's disease. This inclusion was spherical and 3,20 µm in size. It was most frequently detected in the hippocampal CA1 region and in the prosubiculum but was not present in the white matter. The density of this inclusion increased significantly with aging and decreased after the occurrence of neurofibrillary tangles. The presence of the inclusion was confirmed using immunoelectron microscopy. These findings show a possibility that the inclusion is a novel aging-related structure in the human brain. [source] Strategic Localization of Toll-like Receptor 4 in the Digestive Tract of Blunt Snout Bream (Megalobrama amblycephala)ANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 6 2009G. Y. Zhang Summary This study was performed to determine the localization strategies of Toll-like Receptor 4 (TLR4) in digestive tract (oesophagus, bulbodium, foregut, midgut and hindgut) of Blunt snout bream (Megalobrama amblycephala) using immunohistochemical staining method. TLR4 positive cells were observed throughout the digestive tract. In the oesophagus, some positive reactions in lamina propria were found around small blood vessels and there were also some positive cells within the stratified squamous epithelium. Lots of positive cells were observed in the muscular layer of the oesophagus. In bulbodium, foregut and hindgut, the expression of TLR4 was mainly restricted to the apical surface of epithelial cells located at the bottom of the mucosal folds and the mesenchymal cells in lamina propria. It was very interesting that epithelial cells in the midgut, but none in other parts, had many TLR4 positive cytoplasmic granular structures which were also periodic acid Schiff positive. These findings suggested that TLR4 was expressed in a compartmentalized manner in the Blunt snout bream (M. amblycephala) digestive tract and provided novel information about the in vivo localization of pattern recognition receptors. [source] | ||||||||||||||||