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In this review, we demonstrate how differentiated membrane domains can be detected in epithelial cells using conventional light and electron microscopy, freeze-fracture electron microscopy and the immunoand cytochemical detection of membrane components. Using specific examples from the kidney, we show how the polarized insertion of these components into either apical or basolateral plasma membrane regions on either side of the tight junction barrier is related to specific functions of principal and intercalated cells in the collecting duct. In addition, distinct basal and lateral membrane domains have been revealed in some cells that are maintained in the absence of a tight junctional barrier in the plane of the membrane. This suggests that other factors, possibly related to cytoskeletal elements, may be involved in the functional segregation of these membrane areas. We propose that epithelial cell plasma membranes should be subdivided into apical, lateral and basal regions, and that the term “basolateral” may be an oversimplification. 相似文献
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Lelio Camilleri Raymond G. Harder Mark Olsen 《Language Resources and Evaluation》1990,24(5-6):495-500
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Patients presenting with ischemic chest pain and electrocardiographic evidence of global T-wave inversion are most frequently women with intact left ventricular function and no critical stenosis of major coronary vessels. Hence, this syndrome has a good immediate and long-term prognosis. 相似文献
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A numerical assessment of the load bearing capacity of externally pressurized moderately thick tubes
Leone Corradi Valentino Di Marcello Lelio Luzzi Fulvio Trudi 《International Journal of Pressure Vessels and Piping》2009,86(8):525-532
The collapse behavior of cylindrical shells pressurized from outside is examined. Attention is focused on tubes of moderate thickness, as required by very deep water pipelines or some innovative nuclear power plant proposals. Their collapse is expected to be dominated by yielding but, because of the decreasing nature of the post-collapse evolution, interaction with instability is likely to be significant enough to demand consideration. At present, no quantitative assessment of such effect is available, because little study has been devoted to tubes in this thickness range.Plasticity–instability interaction is activated by imperfections and to assess their influence on a systematic numerical study is undertaken. Computations produce a meaningful measure of the collapse pressure and it is proposed that the allowable pressure be determined on its basis, by introducing a suitable safety factor. This is chosen so that results reproduce those provided by presently accepted procedures in the well explored and reliable range of medium-thin tubes. When the same factor is applied to thicker tubes, the resulting allowable pressure is significantly higher than the values suggested by codes, which apparently react to the present lack of knowledge by assuming an extremely conservative attitude. 相似文献
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Lelio Camilleri 《Minds and Machines》1992,2(4):365-377
The paper treats issues concerning the modular modelisation of musical mental processes. Some musical phenomena, like musical illusions, are explained in the framework of modularity and hypotheses are advanced in which the modular model seems very promising for the study of musical perception and cognition. In addition, arguments are proposed to distinguish between levels of abstraction and knowledge in musical cognitive processes.Moreover, some aspects about the theory of musical competence and the theory of musical processing are identified and the possibilities for the integration of varying theoretical assertions are considered in light of these distinctions. 相似文献
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In the last few years, there has been a renewed interest in the molten salt reactor (MSR), one of the “Generation IV International Forum” concepts, which adopts a circulating molten salt mixture as both heat generator (fuel) and coolant. The heat transfer of a fluid with internal heat generation depends on the strength of the source whose influence on the heat exchange process is significant enough to demand consideration. At present, few studies have been performed on the subject from either an experimental or a numerical point of view.This study considers fluids with a wide range of Reynolds numbers, flowing through smooth and straight circular tubes within which the flow is hydrodynamically developed but thermally developing (conditions of interest for MSR core channels). The study aims at an assessment of the heat transfer modelling for a large variety of fluids (with Prandtl numbers in the range 0≤Pr≤104), in particular taking into account the influence of the internal heat generation on the temperature distribution, which plays an important role in the case of molten salts for nuclear reactors. To this purpose, the general and unified solution of the heat transfer equation is applied to the turbulent Graetz problem with boundary conditions of the third kind and arbitrary heat source distribution, incorporating recent formulations for turbulent flow and convection.Computed results are shown to be in a good agreement with experimental data concerning heat transfer evaluations for both fully developed and thermally developing flow conditions, over a large range of Prandtl numbers (10?2<Pr<104). Finally, a preliminary correlation, which includes the Prandtl number range of interest for molten salts, is proposed for the Nusselt number predictions in the case of simultaneous uniform wall heat flux and internal heat generation. 相似文献
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Esposito Luciana; Vitagliano Luigi; Zagari Adriana; Mazzarella Lelio 《Protein engineering, design & selection : PEDS》2000,13(12):825-828
The structural analysis of a deamidated derivative of ribonucleaseA, determined at 0.87 Å resolution, reveals a highly significantnegative correlation between CN and CO bond distances in peptidegroups. This trend, i.e. the CO bond lengthens when the CN bondshortens, is also found in seven out of eight protein structures,determined at ultrahigh resolution (<0.95 Å). In fiveof them the linear correlation is statistically significantat the 95% confidence level. The present findings are consistentwith the traditional view of amide resonance and, although alreadyfound in small peptide structures, they represent a new andimportant result. In fact, in a protein structure the fine detailsof the peptide geometry are only marginally affected by thecrystal field and they are mostly produced by intramolecularand solvent interactions. The analysis of very high-resolutionprotein structures can reveal subtle information about localelectronic features of proteins which may be critical to folding,function or ligand binding. 相似文献