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Efficient Representation (efficient + representation)
Selected AbstractsElastic Potential Grids: Accurate and Efficient Representation of Intermolecular Interactions for Fully Flexible DockingCHEMMEDCHEM, Issue 8 2009Sina Kazemi Potential fields represented by irregular, deformable 3D grids provide an accurate and efficient lookup table function for evaluating intermolecular interactions in docking algorithms that consider target flexibility. Target movements can be translated into appropriate displacements of grid intersection points in a binding site region if the irregular deformable 3D grid is modeled as a homogeneous linear elastic body. [source] Performance of Sub-Saharan Vertebrates as Indicator Groups for Identifying Priority Areas for ConservationCONSERVATION BIOLOGY, Issue 1 2003Joslin L. Moore Often, these sets of important areas, referred to as priority sets, have been identified through use of data on a single taxon (e.g., birds), which is assumed to act as an indicator for all biodiversity. Using a database of the distributions of 3882 vertebrate species in sub-Saharan Africa, we conducted one of very few large-scale tests of this assumption. We used six potential indicator groups,birds, mammals, amphibians, snakes, threatened birds, and threatened mammals,to find priority sets of 200 areas that best represent the species in that group. Priority sets of grid cells designed to maximize representation of a single indicator group captured 83,93% of species in the other groups. This high degree of representation is consistent with observed high levels of overlap in the patterns of distribution of species in different groups. Those species of highest conservation interest were more poorly represented, however, with only 75,88% of other groups' threatened species and 63,76% of other groups' narrow-range species represented in the priority sets. We conclude that existing priority sets based on indicator groups provide a pragmatic basis for the immediate assessment of priorities for conservation at a continental scale. However, complete and efficient representation,especially of narrow-range species,will not be achieved through indicator groups alone. Therefore, priority-setting procedures must remain flexible so that new areas important for other taxa can be incorporated as data become available. Resumen: La meta de la identificación de prioridades globales y continentales de conservación es la identificación de áreas particularmente valiosas para la conservación en las cuales enfocar esfuerzos más detallados. A menudo, estos conjuntos de áreas importantes (referidas como conjuntos prioritarios) han sido identificados utilizando datos de un solo taxón (e. g. aves), el cual se supone que actúa como indicador de toda la biodiversidad. Utilizando una base de datos de la distribución de 3882 especies de vertebrados en África sub-Sahara, realizamos una de las pocas pruebas a gran escala de este supuesto. Utilizamos seis grupos de indicadores potenciales (aves, mamíferos, anfibios, serpientes, aves amenazadas y mamíferos amenazados ) para encontrar conjuntos prioritarios de 200 áreas que mejor representan las especies de ese grupo. Conjuntos prioritarios de celdas matriciales diseñadas para maximizar la representatividad de un grupo indicador capturaron 83,93% de las especies de los otros grupos. Este alto grado de representatividad es consistente con los altos niveles de superposición observados en los patrones de distribución de especies en los diferentes grupos. Sin embargo, las especies de mayor interés para la conservación estaban poco representadas, con solo 75,88% de las especies amenazadas de otros grupos y 63,76% de las especies de distribución restringida de otros grupos representados en los conjuntos prioritarios. Concluimos que los conjuntos prioritarios existentes, basados en grupos indicadores, proporcionan una base pragmática para la evaluación inmediata de las prioridades de conservación a escala continental. Sin embargo, no se logrará la representación completa y eficiente,especialmente de especies de distribución restringida,solo con grupos indicadores. Por lo tanto, los procedimientos de definición de prioridades deben permanecer flexibles para que se puedan incorporar nuevas áreas importantes para otros taxones a medida que se obtienen los datos. [source] Changes in neural activity associated with learning to articulate novel auditory pseudowords by covert repetitionHUMAN BRAIN MAPPING, Issue 11 2008Andreas M. Rauschecker Abstract Learning to articulate novel combinations of phonemes that form new words through a small number of auditory exposures is crucial for development of language and our capacity for fluent speech, yet the underlying neural mechanisms are largely unknown. We used functional magnetic resonance imaging to reveal repetition,suppression effects accompanying such learning and reflecting discrete changes in brain activity due to stimulus-specific fine-tuning of neural representations. In an event-related design, subjects were repeatedly exposed to auditory pseudowords, which they covertly repeated. Covert responses during scanning and postscanning overt responses showed evidence of learning. An extensive set of regions activated bilaterally when listening to and covertly repeating novel pseudoword stimuli. Activity decreased, with repeated exposures, in a subset of these areas mostly in the left hemisphere, including premotor cortex, supplementary motor area, inferior frontal gyrus, superior temporal cortex, and cerebellum. The changes most likely reflect more efficient representation of the articulation patterns of these novel words in two connected systems, one involved in the perception of pseudoword stimuli (in the left superior temporal cortex) and one for processing the output of speech (in the left frontal cortex). Both of these systems contribute to vocal learning. Hum Brain Mapp 2008. © 2007 Wiley-Liss, Inc. [source] Surface wavelets: a multiresolution signal processing tool for 3D computational modellingINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 3 2001Kevin Amaratunga Abstract In this paper, we provide an introduction to wavelet representations for complex surfaces (surface wavelets), with the goal of demonstrating their potential for 3D scientific and engineering computing applications. Surface wavelets were originally developed for representing geometric objects in a multiresolution format in computer graphics. These wavelets share all of the major advantages of conventional wavelets, in that they provide an analysis tool for studying data, functions and operators at different scales. However, unlike conventional wavelets, which are restricted to uniform grids, surface wavelets have the power to perform signal processing operations on complex meshes, such as those encountered in finite element modelling. This motivates the study of surface wavelets as an efficient representation for the modelling and simulation of physical processes. We show how surface wavelets can be applied to partial differential equations, stated either in integral form or in differential form. We analyse and implement the wavelet approach for a model 3D potential problem using a surface wavelet basis with linear interpolating properties. We show both theoretically and experimentally that an O(h) convergence rate, hn being the mesh size, can be obtained by retaining only O((logN) 7/2N) entries in the discrete operator matrix, where N is the number of unknowns. The principles described here may also be extended to volumetric discretizations. Copyright © 2001 John Wiley & Sons, Ltd. [source] Piecewise travelling-wave basis functions for wiresMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 5 2006I. García-Tuñón Abstract This paper presents a method of moments (MoM) formulation for large thin-wire structures. In our approach, a modified version of the well-known Rao,Wilton,Glisson (RWG) basis functions for wires including a linear phase term is considered. This additional term allows an efficient representation of the travelling-wave modes on each wire, while it preserves the main advantages of RWG bases for arbitrarily complex wire topologies. The paper contains a detailed description of the algorithm used for the computation of the impedance matrix integrals. Finally, some results for scattering problems are presented to show the agreement with the conventional RWG-MoM solution. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 960,966, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21533 [source] | |||||||||||||