Home  About us  Contact
 

Of Models (of + models)

Distribution by Scientific Domains
Medical Sciences50%
Physics and Astronomy20%

Kinds of Of Models

  • variety of models
    		•

    Selected Abstracts

    Particle-in-Cell Simulation of Stationary Plasma Thruster

    CONTRIBUTIONS TO PLASMA PHYSICS, Issue 8-9 2007
    F. Taccogna
    Abstract A very good example for the application of PIC techniques for detailed studies of low-temperature plasmas is the Hall thrusters. Here, a variety of models with different complexities are needed to get better insight into the physics of these systems. Particular emphasis has been spent for the geometrical scaling, for the simulation of the plasma-wall interaction inside the acceleration channel and for ion-neutral collision into the plume emitted from the thruster. Results show the axial acceleration mechanism, the secondary electron emission instability, the azimuthal fluctuations into the channel and the ion backflow and electron trapping in the plume. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Heparan sulfate proteoglycans in experimental models of diabetes: a role for perlecan in diabetes complications

    DIABETES/METABOLISM: RESEARCH AND REVIEWS, Issue 6 2001
    Karin Conde-Knape
    Abstract Proteoglycans are ubiquitous extracellular proteins that serve a variety of functions throughout the organism. Unlike other glycoproteins, proteoglycans are classified based on the structure of the glycosaminoglycan carbohydrate chains, not the core proteins. Perlecan, a member of the heparan sulfate proteoglycan (HSPG) family, has been implicated in many complications of diabetes. Decreased levels of perlecan have been observed in the kidney and in other organs, both in patients with diabetes and in animal models. Perlecan has an important role in the maintenance of the glomerular filtration barrier. Decreased perlecan in the glomerular basement membrane has a central role in the development of diabetic albuminuria. The involvement of this proteoglycan in diabetic complications and the possible mechanisms underlying such a role have been addressed using a variety of models. Due to the importance of nephropathy among diabetic patients most of the studies conducted so far relate to diabetes effects on perlecan in different types of kidney cells. The various diabetic models used have provided information on some of the mechanisms underlying perlecan's role in diabetes as well as on possible factors affecting its regulation. However, many other aspects of perlecan metabolism still await full elucidation. The present review provides a description of the models that have been used to study HSPG and in particular perlecan metabolism in diabetes and some of the factors that have been found to be important in the regulation of perlecan. Copyright © 2001 John Wiley & Sons, Ltd. [source]

    On the distribution of wildfire sizes

    ENVIRONMETRICS, Issue 6 2003
    Frederic Paik Schoenberg
    Abstract A variety of models for the wildfire size distribution are examined using data on Los Angeles County wildfires greater than 100 acres between 1950 and 2000. In addition to graphs and likelihood criteria, Kolmogorov,Smirnoff and Cramer,von Mises statistics are used to compare the models. The tapered Pareto distribution appears to fit the data quite well and offers some advantages over the untapered Pareto distribution, while alternatives including the lognormal, half-normal, exponential and extremal distributions fit poorly. The size distribution appears to be quite stable over the examination period, though inspection of the transformed wildfire sizes for the tapered Pareto reveals some limited trend in the residuals, indicating a very slight gradual decrease in the average fire size in Los Angeles County over these 50 years. Copyright © 2003 John Wiley & Sons, Ltd. [source]

    Transepidermal water loss reflects permeability barrier status: validation in human and rodent in vivo and ex vivo models

    EXPERIMENTAL DERMATOLOGY, Issue 7 2006
    Joachim W. Fluhr
    Abstract:, Permeability barrier function is measured with instruments that assess transepidermal water loss (TEWL), either with closed- or open-loop systems. Yet, the validity of TEWL as a measure of barrier status has been questioned recently. Hence, we tested the validity of this measure by comparing TEWL across a wide range of perturbations, with a variety of methods, and in a variety of models. TEWL rates with two closed-chamber systems (VapoMeter and H4300) and one closed-loop system (MEECO) under different experimental in vivo conditions were compared with data from four open-loop instruments, i.e. TM 210, TM 300, DermaLab and EP 1. The instruments were compared in vivo both in humans and hairless mice skin subjected to different degrees of acute barrier disruption. The values obtained with bioengineering systems were correlated with absolute water loss rates, determined gravimetrically. Measurements with both closed and open systems correlated not only with each other, but each method detected different degrees of barrier dysfunction. Although all instruments differentiated among gradations in TEWL in the mid-range of barrier disruption in vivo, differences in very low and very high levels of disruption were less accurately measured with the H4300 and DermaLab systems. Nevertheless, a high Pearson correlation coefficient (r) was calculated for data from all instruments vs. gravimetrically assessed TEWL. Together, these results verify the utility of TEWL as a measure of permeability barrier status. Moreover, all tested instruments are reliable tools for the assessment of variations in permeability barrier function. [source]

    On the estimation of fatigue life in notches differentiating the phases of crack initiation and propagation

    FATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 1 2010
    J. VÁZQUEZ
    ABSTRACT Over the last three decades, a variety of models have been developed in order to predict the life of components under fatigue. Some of the models are based on the definition of the fatigue process as a combination of the phases of crack initiation and crack propagation, considering component life as the sum of the duration of each phase. Other models consider only one of the phases; some consider only initiation while others only propagation, though in this case, from cracks with lengths in the order of the microstructural dimensions. This article will carry out a comparative analysis of the methods that consider life as the sum of the duration of both phases. In this same line, it proposes yet another method, which simulates crack growth according to damage theories. In analysing the behaviour of each model, this paper will describe various elements: the prediction that each of them produces regarding notched specimens submitted to testing, the advantages and inconveniences of each, and lastly, the possibilities of applying each of the models to more realistic geometries. [source]

    PD-1 signalling in CD4+ T cells restrains their clonal expansion to an immunogenic stimulus, but is not critically required for peptide-induced tolerance

    IMMUNOLOGY, Issue 1 2010
    Joanne E. Konkel
    Summary The ultimate outcome of T-cell recognition of peptide,major histocompatibility complex (MHC) complexes is determined by the molecular conte