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2010

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Articles 5521 - 5550 of 8625

Full-Text Articles in Physical Sciences and Mathematics

Browse Biomass Removal And Nutritional Condition Of Moose Alces Alces, C Tom Seaton, Thomas F. Paragi, Rodney D. Boertje, Knut Kielland, Stephen Dubois, Craig L. Fleener Jan 2010

Browse Biomass Removal And Nutritional Condition Of Moose Alces Alces, C Tom Seaton, Thomas F. Paragi, Rodney D. Boertje, Knut Kielland, Stephen Dubois, Craig L. Fleener

Craig L Fleener

No abstract provided.

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An Analysis Of Temperature Variations Using Remote Sensing Approach In Lokoja Area, Fanan Ujoh Mr, Olarewaju O. Ifatimehin Mr, Sunday Ishaya Mr Jan 2010

An Analysis Of Temperature Variations Using Remote Sensing Approach In Lokoja Area, Fanan Ujoh Mr, Olarewaju O. Ifatimehin Mr, Sunday Ishaya Mr

Dr. Fanan Ujoh

This study investigates the thermal variations of the different land use/cover types in urban Lokoja town retrieved from Landsat TM imagery of 1987. Band 2, 3, 4 and 6 of the imagery were used in the classification, estimation of NDVI, land surface emissivity values, and satellite sensor temperature. The Qin et al’s mono window algorithm was employed to obtain the land surface temperatures of the different land use/cover types classified. The results indicate that there is a significant variation in temperatures among the different land use/cover types in Lokoja. The built up area and the vacant area have the highest …

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Discrete Nonparametric Algorithms For Outlier Detection With Genomic Data, Debashis Ghosh Jan 2010

Discrete Nonparametric Algorithms For Outlier Detection With Genomic Data, Debashis Ghosh

Debashis Ghosh

In high-throughput studies involving genetic data such as from gene expression mi- croarrays, dierential expression analysis between two or more experimental conditions has been a very common analytical task. Much of the resulting literature on multiple comparisons has paid relatively little attention to the choice of test statistic. In this article, we focus on the issue of choice of test statistic based on a special pattern of dierential expression. The approach here is based on recasting multiple comparisons procedures for assessing outlying expression values. A major complication is that the resulting p-values are discrete; some theoretical properties of sequential testing …

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Detecting Outlier Genes From High-Dimensional Data: A Fuzzy Approach, Debashis Ghosh Jan 2010

Detecting Outlier Genes From High-Dimensional Data: A Fuzzy Approach, Debashis Ghosh

Debashis Ghosh

A recent nding in cancer research has been the characterization of previously undis- covered chromosomal abnormalities in several types of solid tumors. This was found based on analyses of high-throughput data from gene expression microarrays and motivated the development of so-called `outlier' tests for dierential expression. One statistical issue was the potential discreteness of the test statistics. Using ideas from fuzzy set theory, we develop fuzzy outlier detection algorithms that have links to ideas in multiple comparisons. Two- and K-sample extensions are considered. The methodology is illustrated by application to two microarray studies.

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Links Between Analysis Of Surrogate Endpoints And Endogeneity, Debashis Ghosh, Jeremy M. Taylor, Michael R. Elliott Jan 2010

Links Between Analysis Of Surrogate Endpoints And Endogeneity, Debashis Ghosh, Jeremy M. Taylor, Michael R. Elliott

Debashis Ghosh

There has been substantive interest in the assessment of surrogate endpoints in medical research. These are measures which could potentially replace \true" endpoints in clinical trials and lead to studies that require less follow-up. Recent research in the area has focused on assessments using causal inference frameworks. Beginning with a simple model for associating the surrogate and true endpoints in the population, we approach the problem as one of endogenous covariates. An instrumental variables estimator and general two-stage algorithm is proposed. Existing surrogacy frameworks are then evaluated in the context of the model. A numerical example is used to illustrate …

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Meta-Analysis For Surrogacy: Accelerated Failure Time Models And Semicompeting Risks Modelling, Debashis Ghosh, Jeremy M. Taylor, Daniel J. Sargent Jan 2010

Meta-Analysis For Surrogacy: Accelerated Failure Time Models And Semicompeting Risks Modelling, Debashis Ghosh, Jeremy M. Taylor, Daniel J. Sargent

Debashis Ghosh

There has been great recent interest in the medical and statistical literature in the assessment and validation of surrogate endpoints as proxies for clinical endpoints in medical studies. More recently, authors have focused on using meta-analytical methods for quanti cation of surrogacy. In this article, we extend existing procedures for analysis based on the accelerated failure time model to this setting. An advantage of this approach relative to proportional hazards model is that it allows for analysis in the semi-competing risks setting, where we constrain the surrogate endpoint to occur before the true endpoint. A novel principal components procedure is …

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Spline-Based Models For Predictiveness Curves, Debashis Ghosh, Michael Sabel Jan 2010

Spline-Based Models For Predictiveness Curves, Debashis Ghosh, Michael Sabel

Debashis Ghosh

A biomarker is dened to be a biological characteristic that is objectively measured and evaluated as an indicator of normal biologic processes, pathogenic processes, or pharmacologic responses to a therapeutic intervention. The use of biomarkers in cancer has been advocated for a variety of purposes, which include use as surrogate endpoints, early detection of disease, proxies for environmental exposure and risk prediction. We deal with the latter issue in this paper. Several authors have proposed use of the predictiveness curve for assessing the capacity of a biomarker for risk prediction. For most situations, it is reasonable to assume monotonicity of …

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Combining Multiple Models With Survival Data: The Phase Algorithm, Debashis Ghosh, Zheng Yuan Jan 2010

Combining Multiple Models With Survival Data: The Phase Algorithm, Debashis Ghosh, Zheng Yuan

Debashis Ghosh

In many scientic studies, one common goal is to develop good prediction rules based on a set of available measurements. This paper proposes a model averaging methodology using proportional hazards regression models to construct new estimators of predicted survival probabilities. A screening step based on an adaptive searching algorithm is used to handle large numbers of covariates. The nite-sample properties of the proposed methodology is assessed using simulation studies. Application of the method to a cancer biomarker study is also given.

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Author Guidelines For Reporting Scale Development And Validation Results In The Journal Of The Society For Social Work And Research, Peter Cabrera-Nguyen Jan 2010

Author Guidelines For Reporting Scale Development And Validation Results In The Journal Of The Society For Social Work And Research, Peter Cabrera-Nguyen

Elián P. Cabrera-Nguyen

In this invited article, Cabrera-Nguyen provides guidelines for reporting scale development and validation results. Authors' attention to these guidelines will help ensure the research reported in JSSWR is rigorous and of high quality. This article provides guidance for those using exploratory factor analysis (EFA) and confirmatory factor analysis (CFA). In addition, the article provides helpful links to resources addressing structural equation modeling, multiple imputation for missing data, and a general resource for quantitative data analysis.

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Accounting For Response Misclassification And Covariate Measurement Error Improves Powers And Reduces Bias In Epidemiologic Studies, Dunlei Cheng, Adam J. Branscum, James D. Stamey Jan 2010

Accounting For Response Misclassification And Covariate Measurement Error Improves Powers And Reduces Bias In Epidemiologic Studies, Dunlei Cheng, Adam J. Branscum, James D. Stamey

Dunlei Cheng

Purpose: To quantify the impact of ignoring misclassification of a response variable and measurement error in a covariate on statistical power, and to develop software for sample size and power analysis that accounts for these flaws in epidemiologic data. Methods: A Monte Carlo simulation-based procedure is developed to illustrate the differences in design requirements and inferences between analytic methods that properly account for misclassification and measurement error to those that do not in regression models for cross-sectional and cohort data. Results: We found that failure to account for these flaws in epidemiologic data can lead to a substantial reduction in …

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A Bayesian Approach To Sample Size Determination For Studies Designed To Evaluate Continuous Medical Tests, Dunlei Cheng, Adam J. Branscum, James D. Stamey Jan 2010

A Bayesian Approach To Sample Size Determination For Studies Designed To Evaluate Continuous Medical Tests, Dunlei Cheng, Adam J. Branscum, James D. Stamey

Dunlei Cheng

We develop a Bayesian approach to sample size and power calculations for cross-sectional studies that are designed to evaluate and compare continuous medical tests. For studies that involve one test or two conditionally independent or dependent tests, we present methods that are applicable when the true disease status of sampled individuals will be available and when it will not. Within a hypothesis testing framework, we consider the goal of demonstrating that a medical test has area under the receiver operating characteristic (ROC) curve that exceeds a minimum acceptable level or another relevant threshold, and the goals of establishing the superiority …

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Tectonic Environments Of Ancient Civilizations: Opportunities For Archaeoseismological And Anthropological Studies, Eric R. Force, Bruce G. Mcfadgen Jan 2010

Tectonic Environments Of Ancient Civilizations: Opportunities For Archaeoseismological And Anthropological Studies, Eric R. Force, Bruce G. Mcfadgen

Eric R Force

The close spatial relation between ancient civilizations and active tectonic boundaries is robust in the Eastern Hemisphere but counterintuitive given the seismic dis- advantages it implies. Explanations for the observation remain debatable, and no single explanation seems sufficient. Some possibly important factors are unrelated to seismicity, e.g., the influence of tectonism on local water resources and on resource diversity. When examined on finer spatial scales, the relation is still robust. A quan- tifiable influence of tectonism on civilization locations even along Mediterranean shores is suggested by their distribution. The stronger links of tectonism with derivative civilizations suggests a role of …

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How A Bayesian Might Estimate The Distribution Of Cronbach’S Alpha From Ordinal-Dynamic Scaled Data A Case Study Measuring Nursing Home Resident Quality Of Life, Byron J. Gajewski, Diane K. Boyle, Sarah Thompson Jan 2010

How A Bayesian Might Estimate The Distribution Of Cronbach’S Alpha From Ordinal-Dynamic Scaled Data A Case Study Measuring Nursing Home Resident Quality Of Life, Byron J. Gajewski, Diane K. Boyle, Sarah Thompson

Byron J Gajewski

We demonstrate the utility of a Bayesian based approach for calculating intervals of Cronbach’s alpha from a psychological instrument having ordinal responses with a dynamic scale. A small number of response options on an instrument will cause traditional-based interval estimates to be biased. Ordinal-based solutions are problematic because there is no clear mechanism for handling the dynamic scale. One way to remedy the bias is to adjust with a Bayesian approach. The Bayesian approach adjusts the bias and allows theoretically simple calculations of Cronbach’s alpha and intervals. We demonstrate the calculations of the Bayesian approach while at the same time …

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Creation Of Synthetic Discrete Response Regression Models, Joseph Hilbe Jan 2010

Creation Of Synthetic Discrete Response Regression Models, Joseph Hilbe

Joseph M Hilbe

The development and use of synthetic regression models has proven to assist statisticians in better understanding bias in data, as well as how to best interpret various statistics associated with a modeling situation. In this article I present code that can be easily amended for the creation of synthetic binomial, count, and categorical response models. Parameters may be assigned to any number of predictors (which are shown as continuous, binary, or categorical), negative binomial heterogeneity parameters may be assigned, and the number of levels or cut points and values may be specified for ordered and unordered categorical response models. I …

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Grafika Inżynierska Ćw., Wojciech M. Budzianowski Jan 2010

Grafika Inżynierska Ćw., Wojciech M. Budzianowski

Wojciech Budzianowski

No abstract provided.

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Projektowanie Procesów Biotechnologicznych Proj., Wojciech M. Budzianowski Jan 2010

Projektowanie Procesów Biotechnologicznych Proj., Wojciech M. Budzianowski

Wojciech Budzianowski

No abstract provided.

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Projektowanie I Optymalizacja Procesów Proj., Wojciech M. Budzianowski Jan 2010

Projektowanie I Optymalizacja Procesów Proj., Wojciech M. Budzianowski

Wojciech Budzianowski

No abstract provided.

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Metody Numeryczne Lab., Wojciech M. Budzianowski Jan 2010

Metody Numeryczne Lab., Wojciech M. Budzianowski

Wojciech Budzianowski

No abstract provided.

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Odnawialne Źródła Energii W., Wojciech M. Budzianowski Jan 2010

Odnawialne Źródła Energii W., Wojciech M. Budzianowski

Wojciech Budzianowski

No abstract provided.

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Statistical Criteria For Selecting The Optimal Number Of Untreated Subjects Matched To Each Treated Subject When Using Many-To-One Matching On The Propensity Score, Peter C. Austin Jan 2010

Statistical Criteria For Selecting The Optimal Number Of Untreated Subjects Matched To Each Treated Subject When Using Many-To-One Matching On The Propensity Score, Peter C. Austin

Peter Austin

Propensity-score matching is increasingly being used to estimate the effects of treatments using observational data. In many-to-one (M:1) matching on the propensity score, M untreated subjects are matched to each treated subject using the propensity score. The authors used Monte Carlo simulations to examine the effect of the choice of M on the statistical performance of matched estimators. They considered matching 1–5 untreated subjects to each treated subject using both nearest-neighbor matching and caliper matching in 96 different scenarios. Increasing the number of untreated subjects matched to each treated subject tended to increase the bias in the estimated treatment effect; …

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The Performance Of Different Propensity-Score Methods For Estimating Differences In Proportions (Risk Differences Or Absolute Risk Reductions) In Observational Studies, Peter C. Austin Jan 2010

The Performance Of Different Propensity-Score Methods For Estimating Differences In Proportions (Risk Differences Or Absolute Risk Reductions) In Observational Studies, Peter C. Austin

Peter Austin

Propensity score methods are increasingly being used to estimate the effects of treatments on health outcomes using observational data. There are four methods for using the propensity score to estimate treatment effects: covariate adjustment using the propensity score, stratification on the propensity score, propensity-score matching, and inverse probability of treatment weighting (IPTW) using the propensity score. When outcomes are binary, the effect of treatment on the outcome can be described using odds ratios, relative risks, risk differences, or the number needed to treat. Several clinical commentators suggested that risk differences and numbers needed to treat are more meaningful for clinical …

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Computing An Incompressible Viscous Fluid Flow Using Neural Network Based On Modified Adaptive Smoothing Errors, Philadelphia University Jan 2010

Computing An Incompressible Viscous Fluid Flow Using Neural Network Based On Modified Adaptive Smoothing Errors, Philadelphia University

Philadelphia University, Jordan

No abstract provided.

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An Investigation Of Speech Enhancement Using Wavelet Filtering Method, International Journal Of Speech Technology, Philadelphia University Jan 2010

An Investigation Of Speech Enhancement Using Wavelet Filtering Method, International Journal Of Speech Technology, Philadelphia University

Philadelphia University, Jordan

No abstract provided.

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Jordanian Commercial Bank Strategies In High- Rate Of Return Realization And Its Relation With Liquidity Gap Management Performance, Philadelphia University Jan 2010

Jordanian Commercial Bank Strategies In High- Rate Of Return Realization And Its Relation With Liquidity Gap Management Performance, Philadelphia University

Philadelphia University, Jordan

No abstract provided.

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Testing Lyoequivalency For Three Commercially Sustainedrelease Tablets Containing Diltiazem Hydrochloride, Philadelphia University Jan 2010

Testing Lyoequivalency For Three Commercially Sustainedrelease Tablets Containing Diltiazem Hydrochloride, Philadelphia University

Philadelphia University, Jordan

No abstract provided.

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The Novel And The Experimentation, Philadelphia University Jan 2010

The Novel And The Experimentation, Philadelphia University

Philadelphia University, Jordan

No abstract provided.

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Neural-Network-Based Fuzzy Identifier: Design And Evaluation, Philadelphia University Jan 2010

Neural-Network-Based Fuzzy Identifier: Design And Evaluation, Philadelphia University

Philadelphia University, Jordan

No abstract provided.

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Using Database Marketing To Enhance Direct Marketing Alternatives In Jordanian Industrial Shareholders Corporations, Philadelphia University Jan 2010

Using Database Marketing To Enhance Direct Marketing Alternatives In Jordanian Industrial Shareholders Corporations, Philadelphia University

Philadelphia University, Jordan

No abstract provided.

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Diurnal Patterns Of Blowing Sand, John E. Stout Jan 2010

Diurnal Patterns Of Blowing Sand, John E. Stout

John E. Stout

The diurnal pattern of blowing sand results from a complex process that involves an interaction between solar heating, thermal instability, atmospheric turbulence, wind strength, and surface threshold conditions. During the day, solar heating produces thermal instability, which enhances the convective mixing of high momentum winds from the upper levels of the atmosphere to the surface layer. The sun also dries the sand surface so that the critical threshold is as low as possible. Thus, in the afternoon, the combination of strong turbulent winds and a low surface threshold increases the likelihood that winds may intermittently exceed the critical threshold of …

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Strichartz Estimates On Schwarzschild Black Hole Backgrounds, Jeremy Marzoula, Jason Metcalfe, Daniel Tataru, Mihai H. Tohaneanu Jan 2010

Strichartz Estimates On Schwarzschild Black Hole Backgrounds, Jeremy Marzoula, Jason Metcalfe, Daniel Tataru, Mihai H. Tohaneanu

Mihai H. Tohaneanu

We study dispersive properties for the wave equation in the Schwarzschild space-time. The first result we obtain is a local energy estimate. This is then used, following the spirit of [29], to establish global-in-time Strichartz estimates. A considerable part of the paper is devoted to a precise analysis of solutions near the trapping region, namely the photon sphere.

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