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System Consisting (system + consisting)
Kinds of System Consisting Selected AbstractsChemInform Abstract: Catalytic Asymmetric Intramolecular Hydroamination of Alkynes in the Presence of a Catalyst System Consisting of Pd(0)-Methyl Norphos (or Tolyl Renorphos)-benzoic Acid.CHEMINFORM, Issue 16 2009Meda Narsireddy Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] A Tunable Solid-State Fluorescence System Consisting of Organic Salts of Anthracene-2,6-disulfonic Acid with Primary Amines.CHEMINFORM, Issue 33 2005Yuji Mizobe Abstract For Abstract see ChemInform Abstract in Full Text. [source] Crystalline/Crystalline Phase Transitions in Polymer Systems Consisting of Finite-Size Crystals in Each Crystalline Phase: Generalized Gibbs-Thomson EquationMACROMOLECULAR THEORY AND SIMULATIONS, Issue 7 2010Matsuo Hirami Abstract For polymer systems of two crystalline phases of one polymer component, each phase being consisted of polymer crystals of a finite size, we derive the crystalline-crystalline phase transition relationship, i.e., generalized Gibbs-Thomson equation. Its application combined with the crystalline-liquid transition relationship (usual Gibbs-Thomson equation) to the phase behavior of PT phase diagram of polyethylene (PE) is investigated, where the orthorhombic-hexagonal phase transition of PE crystal under high pressure being involved. Comparison with experimental data leads to the estimates of the structural characteristics such as the ratios of (the end surface free energy of polymer crystal/crystal length) for the respective crystalline phases. [source] Comparison of Additional Costs for Several Replacement Strategies of Randomly Ageing Reinforced Concrete PipesCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 7 2009Franck Schoefs Some of them carry seawater and can deteriorate with time because of internal corrosion. Because of the low O2 content of aggressive water, slow corrosion is expected for such applications. If the RCPs are not periodically replaced, they will eventually fail. Replacement strategies for these pipes depend on (1) the risks associated with the failure of the water distribution network, and (2) the costs associated with replacing the pipes, including the removal of existing pipes, installation of new pipes, and associated production losses. Because of the lack of statistical data regarding RCP failure, the development of a risk-based replacement strategy is not an easy task. This article demonstrates how predictive models for the evolution of the failure of RCPs and the associated consequences of failure can be used to develop risk-based replacement strategies for RCPs. An application for the replacement strategies of a network modeled as a system consisting of 228 RCPs is presented as a case study. We focus on the assessment of the number of replaced components that governs the costs. The main objective of this article is to provide a theoretical approach for comparing replacement strategies, based on (1) the results of a reliability study, (2) the representation of the distributions of failed components (binomial distribution), and (3) the decision tree representation for replacement of RCPs. A focus on the scatter of the induced costs themselves is suggested to emphasize the financial risk. [source] Remodeling of the actin cytoskeleton of target hepatocytes and NK cells during induction of apoptosisCYTOSKELETON, Issue 2 2001W. Marty Blom Abstract Natural Killer cells are immune cells that recognize and eliminate altered and non-self cells from the circulation. To study the interaction between NK cells and target cells, we set up an experimental system consisting of rat Interleukin-2 activated Natural Killer cells (A-NK cells) and rat hepatocytes with a masked Major Histocompatibility Complex (MHC). The masking of the MHC induces recognition of the hepatocytes by the NK cells as non-self. We showed that in vitro apoptosis is rapidly induced in the hepatocytes [Blom et al., 1999] after co-incubation with A-NK cells. Now we describe the morphological changes that occur during and after interaction of A-NK cells with hepatocytes. Confocal laser scanning microscopy showed that the actin cytoskeleton of the NK cells was remodeled during attack of hepatocytes. Some NK cells were in close contact with the hepatocytes while others had formed actin-containing dendrites of varying length that made contact with the hepatocytes. However, dendrite formation is not obligatory for induction of apoptosis because cells that were unable to form these did induce FAS-dependent apoptosis in hepatocytes. Apparently both direct as well as distant contact resulted in apoptosis. Formation of the dendrites was calcium-dependent as EGTA largely prevented it. Importantly, chelation of the calcium also suppressed killing of the hepatocytes. Within 1 h after addition of the A-NK cells, morphological changes in hepatocytes that are characteristic of apoptosis, such as the formation of apoptotic bodies and fragmented nuclei, became apparent. Specifically, the actin cytoskeleton of the hepatocytes was remodeled resulting in the formation of the apoptotic bodies. Inhibition of caspase activity by z-Val-Ala-DL-Asp-fluoromethylketone (100 ,M) partly protected against the rearrangement of the actin filaments in the hepatocytes. Cell Motil. Cytoskeleton 49:78,92, 2001. © 2001 Wiley-Liss, Inc. [source] Cascading effects of variation in plant vigour on the relative performance of insect herbivores and their parasitoidsECOLOGICAL ENTOMOLOGY, Issue 1 2002Tiit Teder Abstract 1. Consequences of variation in food plant quality were estimated for a system consisting of two monophagous noctuid herbivores and three ichneumonid parasitoids. 2. In a natural population, pupal weights of the herbivores in this system, Nonagria typhae and Archanara sparganii, were found to be highly variable. Pupal weights increased strongly and consistently with the increase in the vigour of the host plant, Typha latifolia, providing support for the plant vigour hypothesis. Correspondingly, as the moths do not feed as adults, a strong, positive correlation between host vigour and fecundity of the herbivores would be expected. 3. There were strong and positive relationships between adult body sizes of the parasitoids and the sizes of their lepidopteran hosts. Moreover, a direct, positive link between plant quality and parasitoid size was documented. 4. For all three parasitoids, cascading effects of plant quality on body size were weaker than for the herbivores. Differences in the importance of adult feeding and oviposition behaviour suggest that dependence of fitness on body size is also weaker in the parasitoids than in the moths. It is therefore concluded that the numerical response of the herbivore population to a change in plant quality should exceed the corresponding response in the parasitoids. 5. The results of this work imply that variation in plant variables may affect performance of different trophic levels to a different extent. It is suggested that the importance of adult feeding for the reproductive success (capital vs. income breeding strategies) in both herbivores and parasitoids is an essential aspect to consider when predicting responses of such a system to changes in plant quality. [source] A brainlike learning system with supervised, unsupervised, and reinforcement learningELECTRICAL ENGINEERING IN JAPAN, Issue 1 2008Takafumi Sasakawa Abstract According to Hebb's cell assembly theory, the brain has the capability of function localization. On the other hand, it is suggested that in the brain there are three different learning paradigms: supervised, unsupervised, and reinforcement learning, which are related deeply to the three parts of brain: cerebellum, cerebral cortex, and basal ganglia, respectively. Inspired by the above knowledge of the brain in this paper we present a brainlike learning system consisting of three parts: supervised learning (SL) part, unsupervised learning (UL) part, and reinforcement learning (RL) part. The SL part is a main part learning input,output mapping; the UL part is a competitive network dividing input space into subspaces and realizes the capability of function localization by controlling firing strength of neurons in the SL part based on input patterns; the RL part is a reinforcement learning scheme, which optimizes system performance by adjusting the parameters in the UL part. Numerical simulations have been carried out and the simulation results confirm the effectiveness of the proposed brainlike learning system. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 162(1): 32,39, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20600 [source] Analysis of major alkaloids in Rhizoma coptidis by capillary electrophoresis-electrospray-time of flight mass spectrometry with different background electrolytesELECTROPHORESIS, Issue 10 2008Junhui Chen Abstract CE-based techniques with DAD and detection ESI-TOF-MS have been developed for the analysis of seven protoberberine alkaloids and one aporphinoid alkaloid in Huanglian (Rhizoma coptidis), a well-known traditional Chinese herbal medicine. One aqueous BGE and one nonaqueous BGE were developed for CE-DAD and CE-MS analyses, and the CE-ESI-TOF-MS conditions including nebulizer gas pressure, the sheath-liquid composition, its flow rate, etc. were optimized. Eight main alkaloids in R. coptidis could be separated with baseline resolution by CE-DAD with these two different BGEs, and identified by TOF-MS analysis. Moreover, three major alkaloids (berberine, palmatine, and jatrorrhizine) could be quantified accurately by CE-DAD and CE-MS with the BGE system consisting of 50:50 v/v water and ACN containing 50,mM ammonium acetate at pH,6.8. Both techniques provided similar LODs and could be applied with confidence within similar linear dynamic range. However, reproducibility and speed of analysis were better using CE-DAD. When the CE technique was compared with the RP-HPLC method, the CE-DAD and CE-MS methods provided greater efficiency and faster analysis speed, i.e., achieving baseline resolution for all the eight main basic compounds in less than 14,min. The CE method, as a viable alternative to HPLC, is suitable for use as a routine procedure for the rapid identification and quantification of basic compounds in herbal or natural product applications. [source] Historical Aspects of Idiopathic Generalized EpilepsiesEPILEPSIA, Issue 2005Peter Wolf Summary:, Early in these proceedings, the origin of the three terms in the title, "idiopathic generalized epilepsy," is discussed with respect to their significance over time, and typical misunderstandings. In the mid-20th century, a rather chaotic use of a multitude of often loosely defined terms had developed, which increasingly became an obstacle to a meaningful international discussion. The International League against Epilepsy (ILAE) took the initiative to develop an internationally accepted terminology with a classification system consisting of a classification of seizures (1981) and a classification of syndromes (1989). The Idiopathic Generalized Epilepsies are one of its four major groups emerging from a double dichotomy of generalized versus localization-related and idiopathic versus symptomatic. The inclusion of biologic aspects such as syndrome-specific ages of onset ("age-related syndromes") or syndrome-specific relations of seizure occurrence to the sleep,wake cycle ("Epilepsy with Grand Mal on Awaking") meant that the syndrome classification merged the more biological views of the German school with the more neurophysiological ones of the French. Apart from establishing a common international language concerning epilepsy, the International Classification of Epilepsies and Epileptic Syndromes became an important stimulator of research, especially concerning the idiopathic epilepsies. In particular, genetic and functional imaging investigations aim at a better understanding of these conditions. It is now understood that most idiopathic syndromes have a,sometimes complex,genetic background, but we are also becoming aware of the inappropriateness of the time-honored term "generalized" and part of our dichotomies. Both localization-related and "generalized" idiopathic epilepsies seem to share a principle of ictogenesis based on functional anatomic pathogenic networks, and we seem to move toward understanding them as functional system disorders of the brain. [source] Haematopoietic progenitor cells from the common marmoset as targets of gene transduction by retroviral and adenoviral vectorsEUROPEAN JOURNAL OF HAEMATOLOGY, Issue 4 2001Hitoshi Hibino Abstract: To establish a new non-human primate model for human cytokine and gene therapy, we characterized lymphocytes and haematopoietic progenitor cells of the small New World monkey, the common marmoset. We first assessed the reactions of marmoset bone marrow (BM) and peripheral blood (PB) cells to mouse anti-human monoclonal antibodies (mAbs) for the purpose of isolating marmoset lymphocytes and haematopoietic progenitor cells. Both cell fractions stained with CD4 and CD8 mAbs were identified as lymphocytes by cell proliferation assay and morphological examination. Myeloid-specific mAbs such as CD14 and CD33 did not react with marmoset BM and PB cells. No available CD34 and c-kit mAbs could be used to purify the marmoset haematopoietic progenitor cells. Furthermore, we studied the in vitro transduction of the bacterial ,-galactosidase (LacZ) gene into CFU-GM derived from marmoset BM using retroviral and adenoviral vectors. The transduction efficiency was increased by using a mixed culture system consisting of marmoset BM stromal cells and retroviral producer cells. It was also possible to transduce LacZ gene into marmoset haematopoietic progenitor cells with adenoviral vectors as well as retroviral vectors. The percentage of adenovirally transduced LacZ-positive clusters was 15% at day 4 (multiplicity of infection=200), but only 1,2% at day 14. The differential use of viral vector systems is to be recommended in targeting different diseases. Our results suggested that marmoset BM progenitor cells were available to examine the transduction efficiency of various viral vectors in vitro. [source] Expression of individual immunoglobulin genes occurs in an unusual system consisting of multiple independent lociEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 9 2004Donna Abstract Humoral immunity is effected through the rearrangement of immunoglobulin (Ig) genes in individual somatic cells committed to the B,lymphocyte lineage. Haplotype or allelic exclusion restricts B,lymphocytes to the expression of a single Ig receptor that can sustain further somatic modification. In most species, a specific Ig chain is encoded at a single genetic locus. However, in cartilaginous fish, hundreds of independent Ig heavy- (IgH) and Ig light-chain (IgL) gene loci are present, many of which are joined in the germ line. Ig gene transcripts have been amplified from single peripheral blood lymphocytes isolated from the clearnose skate (Raja eglanteria) using reverse-transcription PCR, and a single productive IgH transcript was detected in the majority of cells analyzed. Similarly, only a single IgL transcript was detected in over half of the individual cells. Taken together, these findings suggest that a mechanism for haplotype exclusion arose early in the evolution of antibody diversity and is independent of a single genetic locus. [source] Cohesive-zone modelling of the deformation and fracture of spot-welded jointsFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 10 2005M. N. CAVALLI ABSTRACT The deformation and failure of spot-welded joints have been successfully modelled using a cohesive-zone model for fracture. This has been accomplished by implementing a user-defined, three-dimensional, cohesive-zone element within a commercial finite-element package. The model requires two material parameters for each mode of deformation. Results show that the material parameters from this type of approach are transferable for identical spot welds in different geometries where a single parameter (such as maximum stress) is not. The approach has been demonstrated using a model system consisting of spot-welded joints made from 5754 aluminium sheets. The techniques for determining the cohesive fracture parameters for both nugget fracture and nugget pullout are described in this paper. It has been demonstrated that once the appropriate cohesive parameters for a weld are determined, quantitative predictions can be developed for the strengths, deformations and failure mechanisms of different geometries with nominally identical welds. [source] Linking the flame-retardant mechanisms of an ethylene-acrylate copolymer, chalk and silicone elastomer system with its intumescent behaviourFIRE AND MATERIALS, Issue 6 2005Anna Hermansson Abstract In this paper the flame-retardant mechanisms of a flame-retardant system consisting of ethylene-acrylate copolymer, chalk and silicone elastomer are linked to its foaming process and to its formation of a final intumescent structure. Thermocouples were placed inside and at the surface of cone calorimeter test specimens in order to measure the temperature at different depths during the formation of the intumescent structure. The temperature and visual observations of the foaming process were then linked to chemical reactions seen with thermogravimetric analysis and also coupled with earlier knowledge of the flame-retardant mechanism. A correlation is seen between the chemical reactions, the temperature (inside and at the surface of a cone calorimeter test specimen) as measured by thermocouples and visual observations in the intumescent process. Further, the outcome of this study provides useful information for achieving a deeper understanding of the flame-retardant mechanisms of the ethylene-acrylate copolymer, chalk and silicone elastomer system. Copyright © 2005 John Wiley & Sons, Ltd. [source] Combination of a hydroxy-functional organophosphorus oligomer and a multifunctional carboxylic acid as a flame retardant finishing system for cotton: Part II.FIRE AND MATERIALS, Issue 5 2003Formation of calcium salt during laundering Abstract Multifunctional carboxylic acids, such as 1,2,3,4-butanetetracarboxylic acid (BTCA), were used to bond a hydroxy-functional organophosphorus oligomer (FR) to cotton fabric in the presence of a catalyst, such as sodium hypophosphite (NaH2PO2). Previously, it was found that the cotton fabric treated with FR and BTCA showed a high level of phosphorus retention after one home laundering cycle. However, the flame retardant properties quickly deteriorated as the number of home laundering cycles was increased. In this research, it was found that the free carboxylic acid groups bound to the cotton fabric form an insoluble calcium salt during home laundering, thus diminishing the flame retardant properties of the treated cotton fabric. It was also found that the free carboxylic acid groups on the treated cotton fabric were esterified by triethanolamine (TEA), and that the formation of calcium salt on the fabric was suppressed by the esterification of the free carboxylic acid groups by TEA. The cotton fabric treated with BTCA and the hydroxy-functional organophosphorus oligomer significantly improved its flame retardance when a new catalyst system consisting of hypophosphorous acid (H3PO2) and TEA was used in the system. Copyright © 2003 John Wiley & Sons, Ltd. [source] Abolishing the Tax-Free Threshold in Australia: Simulating Alternative Reforms,FISCAL STUDIES, Issue 2 2009John Creedy H24; H31 Abstract This paper examines the role of the tax-free income tax threshold in a complex tax and transfer system consisting of a range of taxes and benefits, each with its own taper rates and thresholds. Considering a tax and benefit system with benefit taper rates whereby some benefits are received by income groups other than those at the bottom of the distribution, it is suggested that a tax-free threshold is not a necessary requirement to achieve redistribution. Four alternative policy changes, each involving the elimination of the tax-free threshold in Australia and designed to achieve approximate revenue neutrality, were examined using the Melbourne Institute Tax and Transfer Simulator. A range of implications were examined, including labour supply responses to tax changes and the effects of policy changes on inequality and social welfare. The results demonstrate that it is possible to eliminate the tax-free threshold under approximate overall revenue and distribution neutrality, but that it is impossible to improve labour supply incentives at the same time. In order to achieve improved incentives, either revenue or distribution neutrality has to be sacrificed. [source] Glucose-dependent cell size is regulated by a G protein-coupled receptor system in yeast Saccharomyces cerevisiaeGENES TO CELLS, Issue 3 2005Hisanori Tamaki In the yeast, Saccharomyces cerevisiae, cell size is affected by the kind of carbon source in the medium. Here, we present evidence that the Gpr1 receptor and Gpa2 G, subunit are required for both maintenance and modulation of cell size in response to glucose. In the presence of glucose, mutants lacking GPR1 or GPA2 gene showed smaller cells than the wild-type strain. Physiological studies revealed that protein synthesis rate was reduced in the mutant strains indicating that reduced growth rate, while the level of mRNAs for CLN1, 2 and 3 was not affected in all strains. Gene chip analysis also revealed a down-regulation in the expression of genes related to biosynthesis of not only protein but also other cellular component in the mutant strains. We also show that GPR1 and GPA2 are required for a rapid increase in cell size in response to glucose. Wild-type cells grown in ethanol quickly increased in size by addition of glucose, while little change was observed in the mutant strains, in which glucose-dependent cell cycle arrest caused by CLN1 repression was somewhat alleviated. Our study indicates that the yeast G-protein coupled receptor system consisting of Gpr1 and Gpa2 regulates cell size by affecting both growth rate and cell division. [source] Solute movement through intact columns of cryoturbated Upper ChalkHYDROLOGICAL PROCESSES, Issue 13 2008M. Mahmood-ul-Hassan Abstract Cryoturbated Upper Chalk is a dichotomous porous medium wherein the intra-fragment porosity provides water storage and the inter-fragment porosity provides potential pathways for relatively rapid flow near saturation. Chloride tracer movement through 43 cm long and 45 cm diameter undisturbed chalk columns was studied at water application rates of 0·3, 1·0, and 1·5 cm h,1. Microscale heterogeneity in effluent was recorded using a grid collection system consisting of 98 funnel-shaped cells each 3·5 cm in diameter. The total porosity of the columns was 0·47 ± 0·02 m3 m,3, approximately 13% of pores were , 15 µm diameter, and the saturated hydraulic conductivity was 12·66 ± 1·31 m day,1. Although the column remained unsaturated during the leaching even at all application rates, proportionate flow through macropores increased as the application rate decreased. The number of dry cells (with 0 ml of effluent) increased as application rate decreased. Half of the leachate was collected from 15, 19 and 22 cells at 0·3, 1·0, 1·5 cm h,1 application rates respectively. Similar breakthrough curves (BTCs) were obtained at all three application rates when plotted as a function of cumulative drainage, but they were distinctly different when plotted as a function of time. The BTCs indicate that the columns have similar drainage requirement irrespective of application rates, as the rise to the maxima (C/Co) is almost similar. However, the time required to achieve that leaching requirement varies with application rates, and residence time was less in the case of a higher application rate. A two-region convection,dispersion model was used to describe the BTCs and fitted well (r2 = 0·97,0·99). There was a linear relationship between dispersion coefficient and pore water velocity (correlation coefficient r = 0·95). The results demonstrate the microscale heterogeneity of hydrodynamic properties in the Upper Chalk. Copyright © 2007 John Wiley & Sons, Ltd. [source] Hydrological regime analysis of the Selenge River basin, MongoliaHYDROLOGICAL PROCESSES, Issue 14 2003X. Ma Abstract Arid and semi-arid regions are very vulnerable to environmental changes. Climate change studies indicate that the environment in such areas will steadily deteriorate with global warming; inland lakes will shrink and desert areas will expand. Mongolia is a landlocked country in north-central Asia that contains a unique ecological system consisting of taiga, steppe, and desert from north to south. The Selenge River basin (280 000 km2) in northern Mongolia is a semi-arid region underlain by permafrost, between latitudes 46 and 52°N, and longitudes 96 and 109°E. The issue of sustainable development of the basin is very important owing to its limited natural resources, including fresh water, forest, and rangeland. To examine the water cycle processes in the basin, a hydrological analysis was carried out using a simple scheme for the interaction between the land surface and atmosphere (big-leaf model) coupled to a hydrological model for the period 1988,92 to estimate the hydrological regime of the basin. Annual precipitation in this period averaged 298 mm, ranging from 212 to 352 mm at a 1 ° × 1 ° resolution based on data from 10 gauges, and the estimated annual evapotranspiration averaged 241 mm, ranging between 153 and 300 mm. This indicates that evapotranspiration accounts for the overwhelming majority of the annual precipitation, averaging 81% and ranging between 64 and 96%. The annual potential evapotranspiration in the basin averaged 2009 mm; the ratio of evapotranspiration (actual to potential evapotranspiration) was 0·12 and the wetness index (annual precipitation to potential evapotranspiration) was 0·15. Copyright © 2003 John Wiley & Sons, Ltd. [source] Use of TLC-FID and GC-MS/FID to examine the effects of migratory state, diet and captivity on preen wax composition in White-throated Sparrows Zonotrichia albicollisIBIS, Issue 4 2010RAYMOND H. THOMAS Preen wax is important for plumage maintenance and other functions. Its chemical composition is complex, and separating and quantifying its components, commonly by gas chromatography (GC), can be challenging. We present a simple analytical system consisting of thin-layer chromatography/flame ionization detection (TLC-FID) using a solvent system of 100% toluene to analyse the complex compound classes present in preen wax. We used GC and TLC-FID to investigate the effects of migratory status, diet and captivity on the preen wax composition of White-throated Sparrows Zonotrichia albicollis, and to measure the quantity of preen wax on the head, primary and tail feathers. White-throated Sparrows produced preen wax containing only monoesters regardless of migratory state. The monoesters contained several isomers consisting of homologous series of fatty alcohols (C10,C20) and fatty acids (C13,C19) esterified together in different combinations to form monoesters with total carbon numbers ranging from C23 to C38. Weighted average monoester carbon number was greater in captive birds than in wild birds and was greater in captives fed a formulated diet enriched with sesame oil than in birds fed the same diet enriched with fish oil. Captivity and migratory state also affected the complexity of the mixture of monoesters. There was significantly more preen wax on head feathers compared with primary and tail feathers. We suggest that among its many functions, preen wax may play a role in drag reduction by affecting the physical properties of feathers, and/or the fluid flow at their surfaces. [source] Observation of neutral density variations accompanying streamer progression across air gapsIEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 1 2009Tetsuo Fukuchi Member Abstract Neutral density variations accompanying progression of streamers across needle-to-rod air gaps of length 0.75 and 1 m were observed with the use of a laser shadowgraph system consisting of astronomical telescopes for beam expansion and reduction, and an acousto-optic laser deflector for high-speed imaging. The system had a spatial resolution of about 1 mm over an annular observation region of outer diameter 28 cm and inner diameter 11 cm, and a temporal resolution in the order of microseconds. The system was also used to observe neutral density variations accompanying shock waves which resulted from a spark discharge. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source] Analysis of the solid phase stress tensor in multiphase porous mediaINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 4 2007William G. Gray Abstract Conservation equations for mass, momentum, energy, and entropy are formulated for the phases and interfaces of a three-phase system consisting of a solid and two immiscible fluids. The microscale equations are averaged to the macroscale by integration over a representative elementary volume. Thermodynamic statements for each of the phases and interface entities are also formulated at the microscale and then averaged to the macroscale. This departure from most uses of thermodynamics in macroscale analysis ensures consistency between models and parameters at the two scales. The expressions for the macroscale rates of change of internal energy are obtained by differentiating the derived forms for energy and making use of averaging theorems. These thermodynamic expressions, along with the conservation equations, serve as constraints on the entropy inequality. A linearization of the resulting equations is employed to investigate the theoretical origins of the Biot coefficient that relates the hydrostatic part of the total stress tensor to the normal force applied at the solid surface by the pore fluids. The results here are placed in the context of other formulations and expressions that appear in the literature. Copyright © 2006 John Wiley & Sons, Ltd. [source] Theoretical and numerical analyses of convective instability in porous media with temperature-dependent viscosityINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 10 2003Ge Lin Abstract Exact analytical solutions of the critical Rayleigh numbers have been obtained for a hydrothermal system consisting of a horizontal porous layer with temperature-dependent viscosity. The boundary conditions considered are constant temperature and zero vertical Darcy velocity at both the top and bottom of the layer. Not only can the derived analytical solutions be readily used to examine the effect of the temperature-dependent viscosity on the temperature-gradient driven convective flow, but also they can be used to validate the numerical methods such as the finite-element method and finite-difference method for dealing with the same kind of problem. The related analytical and numerical results demonstrated that the temperature-dependent viscosity destabilizes the temperature-gradient driven convective flow and therefore, may affect the ore body formation and mineralization in the upper crust of the Earth. Copyright © 2003 John Wiley & Sons, Ltd. [source] A finite element solution of acoustic propagation in rigid porous mediaINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 10 2005A. Bermśdez Abstract This paper deals with the acoustical behaviour of a rigid porous material. A finite element method to compute both the response to an harmonic excitation and the free vibrations of a three-dimensional finite multilayer system consisting of a free fluid and a rigid porous material is considered. The finite element used is the lowest order face element introduced by Raviart and Thomas, that eliminates the spurious or circulation modes with no physical meaning. For the porous medium a Darcy's like model and the Allard,Champoux model are taken into account. The numerical results show that the finite element method allows us to compute the response curve for the coupled system and the complex eigenfrequencies. Some of them have a small imaginary part but there are also overdamped modes. Copyright © 2004 John Wiley & Sons, Ltd. [source] Exploration of a Standing Mesochannel System with Antimatter/Matter Atomic Probes,ADVANCED MATERIALS, Issue 24 2008Hiroyuki K. M. Tanaka Positronium, a system consisting of an electron and its antimatter, a positron, offers a new technique to explore vertical accessibility and connectivity. Here, we show how this technique can be used to map out the vertical profile of mesoporous silica channel systems by comparing a standing (perpendicular to the substrate) 2D hexagonal with a lying (parallel to the substrate) 2D hexagonal mesoporous film. [source] Thermodynamic optimization of a solar system for cogeneration of water heating and absorption coolingINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 13 2008R. Hovsapian Abstract This paper presents a contribution to understanding the behavior of solar-powered air conditioning and refrigeration systems with a view to determining the manner in which refrigeration rate, mass flows, heat transfer areas, and internal architecture are related. A cogeneration system consisting of a solar concentrator, a cavity-type receiver, a gas burner, and a thermal storage reservoir is devised to simultaneously produce heat (hot water) and cooling (absorption refrigerator system). A simplified mathematical model, which combines fundamental and empirical correlations, and principles of classical thermodynamics, mass and heat transfer, is developed. The proposed model is then utilized to simulate numerically the system transient and steady-state response under different operating and design conditions. A system global optimization for maximum performance (or minimum exergy destruction) in the search for minimum pull-down and pull-up times, and maximum system second law efficiency is performed with low computational time. Appropriate dimensionless groups are identified and the results are presented in normalized charts for general application. The numerical results show that the three-way maximized system second law efficiency, ,II,max,max,max, occurs when three system characteristic mass flow rates are optimally selected in general terms as dimensionless heat capacity rates, i.e. (,ss, ,wxwx, ,Hs)opt=(0.335, 0.28, 0.2). The minimum pull-down and pull-up times, and maximum second law efficiencies found with respect to the optimized operating parameters are sharp and, therefore, important to be considered in actual design. As a result, the model is expected to be a useful tool for simulation, design, and optimization of solar energy systems in the context of distributed power generation. Copyright © 2008 John Wiley & Sons, Ltd. [source] A numerical approach revealing the impact of rheological properties on mouthfeel caused by foodINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 6 2007Katrin Mathmann Summary In contrast to the static chemoreceptor-related flavour perception, texture of food capable of flow is detected dynamically with oral mechanoreceptors while the food is manipulated in the mouth. The resulting sensation called mouthfeel strongly depends on the different physical properties of food. Aim of the current study is to determine numerically the occurring fluid mechanical forces in food suspensions using a simplified tongue-palate model system consisting of two parallel plates. For this purpose, the equations of fluid and particle motion are numerically solved by using structured overlapping grids. In the computational experiment, a density neutral fluid system between the plates is compressed by moving the upper plate with constant velocity down to the other one. It has been found that suspended particles move with the fluid flow but have only minor effect on the global flow field in the applied concentration. [source] Reduced model of discrete-time dynamic image segmentation system and its bifurcation analysisINTERNATIONAL JOURNAL OF IMAGING SYSTEMS AND TECHNOLOGY, Issue 4 2009Ken'ichi Fujimoto Abstract We have developed a discrete-time dynamic image segmentation system consisting of chaotic neurons and a global inhibitor. Our system receives an image with isolated regions and can output segmented images in time series based on oscillatory responses of chaotic neurons. In this article, we derive a reduced model to find intrinsic properties of the system of dynamic image segmentation. Using numerical method for analyzing dynamical systems, we investigated bifurcation phenomena of a fixed point observed in the reduced model. As the results, in a model of two coupled chaotic neurons, we found that a set of Neimark-Sacker bifurcations causes the generation of an in-phase oscillatory response, which is unsuitable for the purpose of dynamic image segmentation. The bifurcation analysis gives appropriate parameter values to exclude the generation of in-phase oscillatory responses, i.e., our dynamic image segmentation system can work well. © 2009 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 19, 283,289, 2009 [source] The , point interaction two-center systemINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 7 2009H. Hogreve Abstract Motivated by the behavior of molecules in strong magnetic fields, we study the quantum system consisting of a particle (electron) interacting with two fixed (nuclear) centers by ,-type point interactions. Spectral properties and resonances of this model as a function of the internuclear separation are investigated qualitatively and quantitatively. We prove analyticity, monotonicity, and other features, compare them with corresponding attributes of related Coulomb systems, and point out the consequences for molecules. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009 [source] Interaction of a two-level cyclic XY n -spin model with a two-mode cavity field in off-resonant statesINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 2 2008Horacio Grinberg Abstract The interaction of the XY n -spin cyclic model with a two-mode cavity field in the rotating-wave approximation is investigated in the framework of a generalized Jaynes,Cummings two-level system consisting of the vacuum state and a thermally averaged manifold of excited sates. Computation of the energy of this manifold allows this interaction to be examined in off-resonant states. Time evolution of the population inversion, photon distribution, and temperature distribution for an excited initial state are computed via second- and third-order perturbation expansion of the time evolution operator matrix elements for the excited and ground states, respectively and for an ideal squeezed initial coherent state of the cavity field. It was assumed that the two modes have initially the same photon distribution. The pattern of the spin population inversion appears as a manifestation of multiple and complicated inerferences, which is mathematically reflected in a double discrete summation that appears in the calculation of the dynamics. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 [source] Theoretical studies on transimination of vitamin B6 analogsINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 1 2002Antoni Salvą Abstract The transimination reaction of vitamin B6 analogs has been studied by semiempirical quantum mechanics calculations (PM3 Hamiltonian) on a model reactive system consisting of the Schiff base made from a pyridoxal-5'-phosphate (PLP) model compound, methylamine and two auxiliary water molecules. The mechanism of this reaction has been theoretically established through the description of the energy and the geometric parameters of the intermediates and transition-state structures in the gas phase and in water solution by means of the use of two different solvation models. The description of the reaction pathway for transimination through the structures that have resulted from the calculations supports the existence of a geminal diamine as the main intermediate. The reaction also involves the occurrence of internal hydrogen transfers and water-mediated hydrogen transfers as rate-limiting steps. This study highlights the key role of water molecules not only in the formation of selected hydrogen bonds but also as true reactives. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002 [source] | ||||||||||||||||||||||||||||||||||||||||||||||