The islets of Langerhans, ranging in size from clusters of a few cells to several thousand cells, are scattered near large blood vessels. While the beta-cell mass in mammals is proportional to body weight, the size ranges of islets are similar between species with different body sizes, possibly reflecting an ...

Abstract This study among 267 Greek teachers and their partners tested and expanded the recently proposed Spillover-Crossover model (SCM) of well-being. Accordingly, experiences built up at work spill over to the home domain, and then influence the partner. The authors integrated equity theory in the model by formulating hypotheses about ...

: The aim of this study was to develop and validate a method for predicting energy expenditure (EE) using a footwear-based system with integrated accelerometer and pressure sensors. : We developed a footwear-based device with an embedded accelerometer and insole pressure sensors for the prediction of EE. The data from ...

Surveys typically characterize lay knowledge of eyewitness factors as low and highly variable. However, there are notable differences across methodologies, samples, and individual factors. To examine these differences systematically, we took a meta-analytic approach to reviewing the findings of 23 surveys assessing lay knowledge of eyewitness issues. Our analyses examined ...

Knowledge of real change values for clinical balance measures can guide clinicians and researchers in interpretation of change scores to evaluate the effectiveness of therapeutic interventions. We are not aware of studies that have reported minimum change values for single-leg-stance-time (SLST) in community-dwelling older adults. A measure of absolute reliability, ...

Aim  Reliable measurement of disease progression and the effect of therapeutic interventions in Duchenne muscular dystrophy (DMD) require clinically meaningful and scientifically sound rating scales. Therefore, we need robust evidence to support such tools. The North Star Ambulatory Assessment (NSAA) is a promising, clinician-rated scale with potential uses spanning clinical ...

Chronic venous disease, a disorder involving venous return from the legs, is a growing epidemic in the developed world. Numerous studies have been conducted in the past two decades in an attempt to elucidate its underlying pathophysiology. Many theories have been proposed to address the profound inflammatory dysregulation, with the ...

Most animals exhibit significant neurological and morphological change throughout their lifetime. No robots to date, however, grow new morphological structure while behaving. This is due to technological limitations but also because it is unclear that morphological change provides a benefit to the acquisition of robust behavior in machines. Here I ...

Background There is limited information on reliable and valid measures of physical activity in older people with impaired function. Objective This study was conducted to compare the accuracy of single-axis accelerometers in recognizing postures and transitions and step counting with the accuracy of video recordings in people with stroke (n=14), ...

Experience has shown us that when data are pooled from multiple studies to create an integrated summary, an analysis based on naïvely-pooled data is vulnerable to the mischief of Simpson's Paradox. Using the proportions of patients with a target adverse event (AE) as an example, we demonstrate the Paradox's effect ...

Bayesian statistical methods are used for meta-analysis in many disciplines, including medicine, molecular biology, and engineering, but have not yet been applied for quantitative synthesis of plant pathology studies. In this paper, we illustrate the key concepts of Bayesian statistics and outline the differences between Bayesian and classical (frequentist) methods ...

We consider random effects meta-analysis where the outcome variable is the occurrence of some event of interest. The data structures handled are where one has one or more groups in each study, and in each group either the number of subjects with and without the event, or the number of ...

We discuss the diffusion of clusters of integrins (and other similar membrane proteins) on a cell membrane with a cortical cytoskeleton. We argue that protein clusters--in contrast with normal oligomers, which are forced to pass through cytoskeletal barriers all at once--should be treated essentially as many-legged random walkers that can ...

When missing data occur in one or more covariates in a regression model, multiple imputation (MI) is widely advocated as an improvement over complete-case analysis (CC). We use theoretical arguments and simulation studies to compare these methods with MI implemented under a missing at random assumption. When data are missing ...

A meta-analysis of the reliability of the scores from a specific test, also called reliability generalization, allows the quantitative synthesis of its properties from a set of studies. It is usually assumed that part of the variation in the reliability coefficients is due to some unknown and implicit mechanism that ...

Treatment noncompliance and missing outcomes at posttreatment assessments are common problems in field experiments in naturalistic settings. Although the two complications often occur simultaneously, statistical methods that address both complications have not been routinely considered in data analysis practice in the prevention research field. This paper shows that identification and ...

Often a binary variable is generated by dichotomizing an underlying continuous variable measured at a specific time point according to a prespecified threshold value. In the event that the underlying continuous measurements are from a longitudinal study, one can use the repeated-measures model to impute missing data on responder status ...

A fundamental challenge in meta-analyses of published epidemiological dose-response data is the estimate of the function describing how the risk of disease varies across different levels of a given exposure. Issues in trend estimate include within studies variability, between studies heterogeneity, and nonlinear trend components. We present a method, based ...

Fueled by the hydrolysis of ATP, the motor protein kinesin literally walks on two legs along the biopolymer microtubule. The number of accidental backsteps that kinesin takes appears to be much larger than what one would expect given the amount of free energy that ATP hydrolysis makes available. This indicates ...

Honey bees provide important pollination services to crops and wild plants. The agricultural use of systemic insecticides, such as neonicotinoids, may harm bees through their presence in pollen and nectar, which bees consume. Many studies have tested the effects on honey bees of imidacloprid, a neonicotinoid, but a clear picture ...

Several approaches exist for handling missing covariates in the Cox proportional hazards model. The multiple imputation (MI) is relatively easy to implement with various software available and results in consistent estimates if the imputation model is correct. On the other hand, the fully augmented weighted estimators (FAWEs) recover a substantial ...

The purpose of this review is to systematically evaluate the effects of an essential-oil mouthwash (EOMW) compared to a chlorhexidine mouthwash with respect to plaque and parameters of gingival inflammation. PubMed/MEDLINE and Cochrane CENTRAL databases were searched for studies up to and including September 2010 to identify appropriate articles. A ...

Microarray experiments frequently produce multiple missing values (MVs) due to flaws such as dust, scratches, insufficient resolution or hybridization errors on the chips. Unfortunately, many downstream algorithms require a complete data matrix. The motivation of this work is to determine the impact of MV imputation on downstream analysis, and whether ...

The aim of the study was to identify which fall-risk tool is most accurate for assessing adults in the hospital setting. Falls can have physical, emotional, social, and financial consequences. Risk assessment affords the first opportunity in prevention. To standardize the use of a fall-risk tool across the Baylor Health ...

Methionine is the first-limiting amino acid in corn and soybean meal-based poultry diets. Therefore, its supplementation level is of primary economic importance to poultry production. The responses to the methionine sources dl-methionine (DLM) and methionine-hydroxy analog-free acid (HMTBA) have been compared using various methodologies. The so-called common plateau nonlinear model ...

In this article, we use meta-analysis to analyze gender differences in recent studies of mathematics performance. First, we meta-analyzed data from 242 studies published between 1990 and 2007, representing the testing of 1,286,350 people. Overall, d = 0.05, indicating no gender difference, and variance ratio = 1.08, indicating nearly equal ...

Summary Evidence synthesis, both qualitatively and quantitatively through meta-analysis, is central to the development of evidence-based medicine. Unfortunately, meta-analysis is often complicated by the suspicion that the available studies represent a biased subset of the evidence, possibly due to publication bias or other systematically different effects in small studies. A ...

Ramsey, Spirtes and Glymour (RSG) critique a method proposed by Neumann et al. (2010) for the discovery of functional networks from fMRI meta-analysis data. We concur with this critique, but are unconvinced that directed graphical models (DGMs) are generally useful for estimating causal effects. We express our reservations using the ...

Methodology for the meta-analysis of individual patient data with survival end-points is proposed. Motivated by questions about the reliance on hazard ratios as summary measures of treatment effects, a parametric approach is considered and percentile ratios are introduced as an alternative to hazard ratios. The generalized log-gamma model, which includes ...

Missing data has remained a major disparity in trauma outcomes research due to missing race and insurance data. Multiple imputation (M.IMP) has been recommended as a solution to deal with this major drawback. Using the National Data Trauma Bank (NTDB) as an example, a complete dataset was developed by deleting ...

Multiple-treatments meta-analyses are increasingly used to evaluate the relative effectiveness of several competing regimens. In some fields which evolve with the continuous introduction of new agents over time, it is possible that in trials comparing older with newer regimens the effectiveness of the latter is exaggerated. Optimism bias, conflicts of ...

Regime shifts in the marine environment have recently received much attention. To date, however, few large-scale meta-analyses have been carried out due to insufficient data coverage and integration between sustained observational datasets because of diverse methodologies used in data collection, recording and archival. Here we review the available data on ...

This study seeks to examine whether existing study-level data meta-analysis approaches can be used to produce unbiased and precise effect estimates relative to meta-analyses conducted using patient-level data, where a recurrent event is the outcome of interest. Data from two studies focusing on the prevention of falls in the hospital ...

Purpose:  To study and quantify the difference in incidence of progression between methods for the assessment of glaucomatous visual field progression. Methods:  We identified 2450 articles published up to April 2009 in the following data sources: PubMed, EMBASE, and Cochrane. Ten studies covering 30 methods were included. All studies aimed ...

We recently showed that palm board measures are systematically inaccurate for full-cue surfaces within reach of one's hand, whereas free-hand gestures and reaching actions are quite accurate for such surfaces (Durgin, Hajnal, Li, Tonge, & Stigliani, 2010). Proffitt and Zadra (2010) claim that our demonstration that palm boards are highly ...

Trauma registry data are usually incomplete. Various methods for dealing with missing data have been used, some of which lead to biased results. One method that reduces bias, multiple imputation (MI), has not been widely adopted. There is no standardization of the approach to missing data across trauma registries. This ...

In this paper, a simulation study is conducted to systematically investigate the impact of dichotomizing longitudinal continuous outcome variables under various types of missing data mechanisms. Generalized linear models (GLM) with standard generalized estimating equations (GEE) are widely used for longitudinal outcome analysis, but these semi-parametric approaches are only valid ...

Missing items are common in quality of life (QoL) questionnaires and present a challenge for research in this field. It remains unclear which of the various methods proposed to deal with missing data performs best in this context. We compared personal mean score, full information maximum likelihood, multiple imputation, and ...

The Points to Consider Document on Missing Data was adopted by the Committee of Health and Medicinal Products (CHMP) in December 2001. In September 2007 the CHMP issued a recommendation to review the document, with particular emphasis on summarizing and critically appraising the pattern of drop-outs, explaining the role and ...

We performed a simulation study comparing the statistical properties of the estimated log odds ratio from propensity scores analyses of a binary response variable, in which missing baseline data had been imputed using a simple imputation scheme (Treatment Mean Imputation), compared with three ways of performing multiple imputation (MI) and ...

Longitudinal study designs are indispensable for investigating age-related functional change. There now are well-established methods for addressing missing data in longitudinal studies. Modern missing data methods not only minimize most problems associated with missing data (e.g., loss of power and biased parameter estimates), but also have valuable new applications such ...

Data mining is based on data files which usually contain errors in the form of missing values. This paper focuses on a methodological framework for the development of an automated data imputation model based on artificial neural networks. Fifteen real and simulated data sets are exposed to a perturbation experiment, ...

BACKGROUND: The purpose of alpha-fetoprotein (AFP) and abdominal ultrasound (US) cannot be discerned in administrative data. AIM: We developed an algorithm to identify AFP and US used as surveillance tests for hepatocellular carcinoma (HCC). METHODS: We evaluated 300 AFP and 301 US tests from a VA database. Surveillance predictors in ...

Missing data are ubiquitous in clinical trials for rheumatic diseases, and it is important to accommodate them using appropriate statistical techniques. We review some of the basic considerations for missing data and survey a range of statistical techniques for analysis of longitudinal clinical trial data with missingness. Using clinical trial ...

Multiple imputation is particularly well suited to deal with missing data in large epidemiologic studies, because typically these studies support a wide range of analyses by many data users. Some of these analyses may involve complex modeling, including interactions and nonlinear relations. Identifying such relations and encoding them in imputation ...

Meta-analysis provides a useful framework for combining information across related studies and has been widely utilized to combine data from clinical studies in order to evaluate treatment efficacy. More recently, meta-analysis has also been used to assess drug safety. However, because adverse events are typically rare, standard methods may not ...

Systematic reviews and accompanying meta-analyses are the cornerstones of evidence-based medicine. Systematic reviews summarize clinical evidence; meta-analyses provide summary estimates of the treatment effect or the diagnostic test accuracy. Although deemed to provide the highest level of evidence, their clinical value is limited as they can only summarize aggregated data. ...

Modern management of blunt aortic injury (BAI) is based on evidence from mostly well-conducted meta-analyses as surrogates for prospective randomized controlled trials. There are several obvious pros and cons to this strategy. The advantages rest on the fact that it is unlikely that a prospective randomized trial comparing open surgical ...

The form of the species richness-productivity relationship (SRPR) is both theoretically important and contentious. In an effort to distill general patterns, ecologists have undertaken meta-analyses, within which each SRPR data set is first classified into one of five alternative forms: positive, humped (unimodal), negative, U-shaped (unimodal), and no relationship. Herein, ...

Genome-wide association studies have recently identified many new loci associated with human complex diseases. These newly discovered variants typically have weak effects requiring studies with large numbers of individuals to achieve the statistical power necessary to identify them. Likely, there exist even more associated variants, which remain to be found ...