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Model Characteristics (model + characteristic)

Distribution by Scientific Domains

Medical Sciences	50%

Selected Abstracts

Factors affecting fluid flow in strike,slip fault systems: coupled deformation and fluid flow modelling with application to the western Mount Isa Inlier, Australia

GEOFLUIDS (ELECTRONIC), Issue 1 2009
A. FORD
Abstract Deformation and focused fluid flow within a mineralized system are critical in the genesis of hydrothermal ore deposits. Dilation and integrated fluid flux due to coupled deformation and fluid flow in simple strike,slip fault geometries were examined using finite difference analysis in three dimensions. A series of generic fault bend and fault jog geometries consistent with those seen in the western Mount Isa Inlier were modelled in order to understand how fault geometry parameters influence the dilation and integrated fluid flux. Fault dip, fault width, bend/jog angle, and length were varied, and a cross-cutting fault and contrasting rock types were included. The results demonstrate that low fault dips, the presence of contrasts in rock type, and wide faults produce highest dilation and integrated fluid flux values. Increasing fault bend lengths and angles increases dilation and integrated fluid flux, but increasing fault jog length or angle has the opposite effect. There is minimal difference between the outputs from the releasing and restraining fault bend and jog geometries. Model characteristics producing greater fluid flows and/or gradients can be used in a predictive capacity in order to focus exploration on regions with more favorable fault geometries, provided that the mineralized rocks had Mohr,Coulomb rheologies similar to the ones used in the models. [source]

Combination of thalidomide and cisplatin in an head and neck squamous cell carcinomas model results in an enhanced antiangiogenic activity in vitro and in vivo

INTERNATIONAL JOURNAL OF CANCER, Issue 8 2007
Gergely P. Vasvari
Abstract Thalidomide is an immunomodulatory, antiangiogenic drug. Although there is evidence that it might be more effective in combination with chemotherapy the exact mechanism of action is unclear. Therefore, we investigated its effect in combination with metronomically applied cisplatin in a xenotransplant mouse model characteristic for advanced head and neck squamous cell carcinomas, its possible synergistic action in vitro, and which tumor-derived factors might be targeted by thalidomide. Although thalidomide alone was ineffective, a combined treatment with low-dose cisplatin inhibited significant tumor growth, proliferation and angiogenesis in vivo as well as migration and tube formation of endothelial cells in vitro. Noteworthy, the latter effect was enhanced after coapplication of cisplatin in nontoxic doses. An inhibitory effect on tumor cell migration was also observed suggesting a direct antitumor effect. Although thalidomide alone did not influence cell proliferation, it augmented antiproliferative response after cisplatin application emphasizing the idea of a potentiated effect when both drugs are combined. Furthermore, we could show that antiangiogenic effects of thalidomide are related to tumor-cell derived factors including vascular endothelial growth factor, basic fibroblast growth factor, hepatocyte growth factor and Il-8 some known and with, granulocyte colony stimulating growth factor and granulocyte macrophage colony stimulating growth factor, some new target molecules of thalidomide. Altogether, our findings reveal new insights into thalidomide-mediated antitumor and antiangiogenic effects and its interaction with cytostatic drugs. © 2007 Wiley-Liss, Inc. [source]

Otitis media in a mouse model for Down syndrome

INTERNATIONAL JOURNAL OF EXPERIMENTAL PATHOLOGY, Issue 5 2009
Fengchan Han
Summary The Ts65Dn mouse shares many phenotypic characteristics of human Down syndrome. Here, we report that otitis media, characterized by effusion in the middle ear and hearing loss, was prevalent in Ts65Dn mice. Of the 53 Ts65Dn mice tested, 81.1% had high auditory-evoked brainstem response (ABR) thresholds for at least one of the stimulus frequencies (click, 8 kHz, 16 kHz and 32 kHz), in at least one ear. The ABR thresholds were variable and showed no tendency toward increase with age, from 2 to 7 months of age. Observation of pathology in mice, aged 3,4 months, revealed middle ear effusion in 11 of 15 Ts65Dn mice examined, but only in two of 11 wild-type mice. The effusion in each mouse varied substantially in volume and inflammatory cell content. The middle ear mucosae were generally thickened and goblet cells were distributed with higher density in the epithelium of the middle ear cavity of Ts65Dn mice as compared with those of wild-type controls. Bacteria of pathogenic importance to humans also were identified in the Ts65Dn mice. This is the first report of otitis media in the Ts65Dn mouse as a model characteristic of human Down syndrome. [source]

Comparing Safety Climate between Two Populations of Hospitals in the United States

HEALTH SERVICES RESEARCH, Issue 5p1 2009
Sara J. Singer
Objective. To compare safety climate between diverse U.S. hospitals and Veterans Health Administration (VA) hospitals, and to explore the factors influencing climate in each setting. Data Sources. Primary data from surveys of hospital personnel; secondary data from the American Hospital Association's 2004 Annual Survey of Hospitals. Study Design. Cross-sectional study of 69 U.S. and 30 VA hospitals. Data Collection. For each sample, hierarchical linear models used safety-climate scores as the dependent variable and respondent and facility characteristics as independent variables. Regression-based Oaxaca,Blinder decomposition examined differences in effects of model characteristics on safety climate between the U.S. and VA samples. Principal Findings. The range in safety climate among U.S. and VA hospitals overlapped substantially. Characteristics of individuals influenced safety climate consistently across settings. Working in southern and urban facilities corresponded with worse safety climate among VA employees and better safety climate in the U.S. sample. Decomposition results predicted 1.4 percentage points better safety climate in U.S. than in VA hospitals: ,0.77 attributable to sample-characteristic differences and 2.2 due to differential effects of sample characteristics. Conclusions. Results suggest that safety climate is linked more to efforts of individual hospitals than to participation in a nationally integrated system or measured characteristics of workers and facilities. [source]

Generalized strain probing of constitutive models

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 15 2004
Youssef M. A. Hashash
Abstract Advanced material constitutive models are used to describe complex soil behaviour. These models are often used in the solution of boundary value problems under general loading conditions. Users and developers of constitutive models need to methodically investigate the represented soil response under a wide range of loading conditions. This paper presents a systematic procedure for probing constitutive models. A general incremental strain probe, 6D hyperspherical strain probe (HSP), is introduced to examine rate-independent model response under all possible strain loading conditions. Two special cases of HSP, the true triaxial strain probe (TTSP) and the plane-strain strain probe (PSSP), are used to generate 3-D objects that represent model stress response to probing. The TTSP, PSSP and general HSP procedures are demonstrated using elasto-plastic models. The objects resulting from the probing procedure readily highlight important model characteristics including anisotropy, yielding, hardening, softening and failure. The PSSP procedure is applied to a Neural Network (NN) based constitutive model. It shows that this probing is especially useful in understanding NN constitutive models, which do not contain explicit functions for yield surface, hardening, or anisotropy. Copyright © 2004 John Wiley & Sons, Ltd. [source]

The Growing Pains of Integrated Health Care for the Elderly: Lessons from the Expansion of PACE

THE MILBANK QUARTERLY, Issue 2 2004
DIANE L. GROSS
The early success of the demonstration Program of All-Inclusive Care for the Elderly (PACE) led to its designation as a permanent Medicare program in 1997. But the growth in the number of programs and enrollment has lagged and does not meet expectations. This article offers insights into the mechanisms influencing the expansion of PACE, from information obtained in interviews and surveys of administrators, medical directors, and financial officers in 27 PACE programs. Sixteen barriers to expansion were found, including competition, PACE model characteristics, poor understanding of the program among referral sources, and a lack of financing for expansion. This experience offers important lessons for providing integrated health care to the frail elderly. [source]

On the use of logarithmic scales for analysis of diffraction data

ACTA CRYSTALLOGRAPHICA SECTION D, Issue 12 2009
Alexandre Urzhumtsev
Predictions of the possible model parameterization and of the values of model characteristics such as R factors are important for macromolecular refinement and validation protocols. One of the key parameters defining these and other values is the resolution of the experimentally measured diffraction data. The higher the resolution, the larger the number of diffraction data Nref, the larger its ratio to the number Nat of non-H atoms, the more parameters per atom can be used for modelling and the more precise and detailed a model can be obtained. The ratio Nref/Nat was calculated for models deposited in the Protein Data Bank as a function of the resolution at which the structures were reported. The most frequent values for this distribution depend essentially linearly on resolution when the latter is expressed on a uniform logarithmic scale. This defines simple analytic formulae for the typical Matthews coefficient and for the typically allowed number of parameters per atom for crystals diffracting to a given resolution. This simple dependence makes it possible in many cases to estimate the expected resolution of the experimental data for a crystal with a given Matthews coefficient. When expressed using the same logarithmic scale, the most frequent values for R and Rfree factors and for their difference are also essentially linear across a large resolution range. The minimal R -factor values are practically constant at resolutions better than 3,Å, below which they begin to grow sharply. This simple dependence on the resolution allows the prediction of expected R -factor values for unknown structures and may be used to guide model refinement and validation. [source]

A Global Sensitivity Test for Evaluating Statistical Hypotheses with Nonidentifiable Models

BIOMETRICS, Issue 2 2010
D. Todem
Summary We consider the problem of evaluating a statistical hypothesis when some model characteristics are nonidentifiable from observed data. Such a scenario is common in meta-analysis for assessing publication bias and in longitudinal studies for evaluating a covariate effect when dropouts are likely to be nonignorable. One possible approach to this problem is to fix a minimal set of sensitivity parameters conditional upon which hypothesized parameters are identifiable. Here, we extend this idea and show how to evaluate the hypothesis of interest using an infimum statistic over the whole support of the sensitivity parameter. We characterize the limiting distribution of the statistic as a process in the sensitivity parameter, which involves a careful theoretical analysis of its behavior under model misspecification. In practice, we suggest a nonparametric bootstrap procedure to implement this infimum test as well as to construct confidence bands for simultaneous pointwise tests across all values of the sensitivity parameter, adjusting for multiple testing. The methodology's practical utility is illustrated in an analysis of a longitudinal psychiatric study. [source]