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Methods Use (methods + use)

Distribution by Scientific Domains

Medical Sciences	40%

Selected Abstracts

How the 1977 World Health Organization report on alcohol-related disabilities came to be written: a provisional analysis

ADDICTION, Issue 11 2007
Griffith Edwards
ABSTRACT Background In 1977 the World Health Organization (WHO) published a report entitled ,Alcohol-Related Disabilities'. The crucial contribution of this report was to differentiate between alcohol dependence, on one hand, and alcohol-related disabilities (or problems) on the other hand. Essentially, it offered a bi-axial mapping of the field of concern. Aims This paper seeks to identify the multiple influences which shaped the evolution of this report. Methods Use is made of unpublished archival material and recall of personal involvement, together with relevant published material. Results Three major influences made it possible to move beyond the confines of previous WHO thinking on alcohol: the multi-disciplinary nature of the input; the internationality of the enterprise; and the expectations set that the concepts developed should speak to the practical world. Conclusions The arena of drug and alcohol policy has, for more than a century, been rich in its reports. This case study, although limited in its immediate content, points to the need for further analysis of the history of such reports. [source]

Velocity analysis based on data correlation

GEOPHYSICAL PROSPECTING, Issue 6 2008
T. Van Leeuwen
ABSTRACT Several methods exist to automatically obtain a velocity model from seismic data via optimization. Migration velocity analysis relies on an imaging condition and seeks the velocity model that optimally focuses the migrated image. This approach has been proven to be very successful. However, most migration methods use simplified physics to make them computationally feasible and herein lies the restriction of migration velocity analysis. Waveform inversion methods use the full wave equation to model the observed data and more complicated physics can be incorporated. Unfortunately, due to the band-limited nature of the data, the resulting inverse problem is highly nonlinear. Simply fitting the data in a least-squares sense by using a gradient-based optimization method is sometimes problematic. In this paper, we propose a novel method that measures the amount of focusing in the data domain rather than the image domain. As a first test of the method, we include some examples for 1D velocity models and the convolutional model. [source]

Imaging FRET standards by steady-state fluorescence and lifetime methods

MICROSCOPY RESEARCH AND TECHNIQUE, Issue 12 2007
Beatriz Domingo
Abstract Imaging fluorescence resonance energy transfer (FRET) between molecules labeled with fluorescent proteins is emerging as a powerful tool to study changes in ions, ligands, and molecular interactions in their physiological cellular environment. Different methods use either steady-state fluorescence properties or lifetime to quantify the FRET rate. In addition, some provide the absolute FRET efficiency whereas others are simply a relative index very much influenced by the actual settings and instrumentation used, which makes the interpretation of a given FRET rate very difficult. The use and exchange of FRET standards in laboratories using these techniques would help to overcome this drawback. We report here the construction and systematic evaluation of FRET standard probes of varying FRET efficiencies. The standards for intramolecular FRET were protein fusions of the cyan and yellow variants of A. victoria green fluorescent protein (ECFP and citrine) joined by short linkers or larger protein spacers, or ECFP tagged with a tetracysteine motif and labeled with the biarsenical fluorochrome, FlAsH. Negative and positive controls of intermolecular FRET were also used. We compared these FRET standards with up to four FRET quantification methods: ratioing of acceptor to donor emission, donor intensity recovery upon acceptor photobleach, sensitized emission after spectral unmixing of raw images, and fluorescence lifetime imaging (FLIM). The latter was obtained with a frequency-domain setup able to provide high quality lifetime images in less than a second, and is thus very well suited for live cell studies. The FRET rates or indexes of the standards were in good agreement regardless of the method used. For the CFP-tetraCys/FlAsH pair, the rate calculated from CFP quenching was faster than that obtained by FLIM. Microsc. Res. Tech., 2007. © 2007 Wiley-Liss, Inc. [source]

Physical,chemical determinants of coil conformations in globular proteins

PROTEIN SCIENCE, Issue 6 2010
Lauren L. Perskie
Abstract We present a method with the potential to generate a library of coil segments from first principles. Proteins are built from ,-helices and/or ,-strands interconnected by these coil segments. Here, we investigate the conformational determinants of short coil segments, with particular emphasis on chain turns. Toward this goal, we extracted a comprehensive set of two-, three-, and four-residue turns from X-ray,elucidated proteins and classified them by conformation. A remarkably small number of unique conformers account for most of this experimentally determined set, whereas remaining members span a large number of rare conformers, many occurring only once in the entire protein database. Factors determining conformation were identified via Metropolis Monte Carlo simulations devised to test the effectiveness of various energy terms. Simulated structures were validated by comparison to experimental counterparts. After filtering rare conformers, we found that 98% of the remaining experimentally determined turn population could be reproduced by applying a hydrogen bond energy term to an exhaustively generated ensemble of clash-free conformers in which no backbone polar group lacks a hydrogen-bond partner. Further, at least 90% of longer coil segments, ranging from 5- to 20 residues, were found to be structural composites of these shorter primitives. These results are pertinent to protein structure prediction, where approaches can be divided into either empirical or abinitio methods. Empirical methods use database-derived information; abinitio methods rely on physical,chemical principles exclusively. Replacing the database-derived coil library with one generated from first principles would transform any empirically based method into its corresponding abinitio homologue. [source]

Potential utility of actuarial methods for identifying specific learning disabilities

PSYCHOLOGY IN THE SCHOOLS, Issue 6 2010
Nicholas Benson
This article describes how actuarial methods can supplant discrepancy models and augment problem solving and Response to Intervention (RTI) efforts by guiding the process of identifying specific learning disabilities (SLD). Actuarial methods use routinized selection and execution of formulas derived from empirically established relationships to make predictions that fall within a plausible range of possible future outcomes. In the case of SLD identification, the extent to which predictions are reasonable can be evaluated by their ability to categorize large segments of the population into subgroups that vary considerably along a spectrum of risk for academic failure. Although empirical comparisons of actuarial methods to clinical judgment reveal that actuarial methods consistently outperform clinical judgment, multidisciplinary teams charged with identifying SLD currently rely on clinical judgment. Actuarial methods provide educators with an empirically verifiable indicator of student need for special education and related services that could be used to estimate the relative effects of exclusionary criteria. This indicator would provide a defensible endpoint in the process of identifying SLD as well as a means of informing and improving the SLD identification process. © 2010 Wiley Periodicals, Inc. [source]