Home About us Contact
|
Home About us Contact | ||
|
|
||
Minimum Distance (minimum + distance)
Selected AbstractsSpatial Autocorrelation Analysis and the Identification of Operational Units for Conservation in Continuous PopulationsCONSERVATION BIOLOGY, Issue 4 2002José Alexandre Felizola Diniz-Filho We show that spatial autocorrelation analysis, applied to phenotypic or molecular data, can be used to describe the geographic structure and therefore can help define optimum strategies for conserving genetic variability within species. We propose that the intercept of a spatial correlogram can be an indication of the minimum distance between samples that can conserve and assess genetic diversity with maximum efficiency at lower costs. This parameter can be used both to define units and to establish sampling strategies for conservation programs. We illustrate the utility of this approach by autocorrelation analyses applied to three data sets: isozyme variability among Eugenia dysenterica populations in Brazilian Cerrado and within populations of Adenophora glandiflora in Korea, and microsatellite variation among Ursus arctos populations in North America. Our results suggest that the intercept of spatial correlograms is a useful parameter for establishing operational units for intraspecific conservation in continuous populations, based on overall genetic or phenotypic variability, by defining the minimum geographic distance at which samples are independent. Resumen: A pesar de los avances recientes en la identificación de la estructura genética poblacional mediante la tecnología de marcadores moleculares, la definición de las unidades intraespecíficas para la conservación es aún problemática. Esto sucede particularmente cuando la variación genética y fenotípica se encuentra distribuida de manera continua en un espacio geográfico. Demostramos que el análisis de autocorrelación espacial, aplicado a los datos fenotípicos o moleculares puede ser usado para describir la estructura geográfica y, por lo tanto, puede ayudar a definir estrategias óptimas para la conservación de la variabilidad genética en las especies. Proponemos que el intercepto de un correlograma espacial puede ser un indicador de la distancia mínima entre muestras que pueden conservar y evaluar la diversidad genética con mayor eficiencia a un costo más bajo. Este parámetro puede ser usado tanto para definir unidades como para establecer estrategias de muestreo para los programas de conservación. Ejemplificamos la utilidad de este método mediante la aplicación de análisis de autocorrelación a tres grupos de datos: variabilidad de isozomas entre poblaciones de Adenophora dysenterica en el cerrado brasileño, dentro de poblaciones de Adenophora glandiflora en Korea y variación microsatélite entre poblaciones de Ursus arctos en América del Norte. Nuestros resultados sugieren que el intercepto de los correlogramas espaciales son un parámetro útil que puede establecer unidades operacionales para conservación intraespecífica en poblaciones continuas, en base a la variabilidad general genética o fenótipica, al definir la distancia geográfica mínima a la cual las muestras son independientes. [source] Estimating the minimum distance of large-block turbo codes using iterative multiple-impulse methodsEUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 5 2007Stewart Crozier A difficult problem for turbo codes is the efficient and accurate determination of the distance spectrum, or even just the minimum distance, for specific interleavers. This is especially true for large blocks, with many thousands of data bits, if the distance is high. This paper compares a number of recent distance estimation techniques and introduces a new approach, based on using specific event impulse patterns and iterative processing, that is specifically tailored to handle long interleavers with high spread. The new method is as reliable as two previous iterative multiple-impulse methods, but with much lower complexity. A minimum distance of 60 has been estimated for a rate 1/3, 8-state, turbo code with a dithered relative prime (DRP) interleaver of length K,=,65,536. Copyright © 2007 John Wiley & Sons, Ltd. [source] Regionalisation of chemical variability in European mountain lakesFRESHWATER BIOLOGY, Issue 12 2009LLUÍS CAMARERO Summary 1. We carried out a coordinated survey of mountain lakes covering the main ranges across Europe (including Greenland), sampling 379 lakes above the local tree line in 2000. The objectives were to identify the main sources of chemical variability in mountain lakes, define a chemical classification of lakes, and develop tools to extrapolate our results to regional lake populations through an empirical regionalisation or upscaling of chemical properties. 2. We investigated the main causes of chemical variability using factor analysis (FA) and empirical relationships between chemistry and several environmental variables. Weathering, sea salt inputs, atmospheric deposition of N and S, and biological activity in soils of the catchment were identified as the major drivers of lake chemistry. 3. We tested discriminant analysis (DA) to predict the lake chemistry. It was possible to use the lithology of the catchments to predict the range of Ca2+ and SO42, into which a lake of unknown chemistry will decrease. Lakes with lower SO42, concentrations have little geologically derived S, and better reflect the variations in atmospheric S loading. The influence of marine aerosols on lakewater chemistry could also be predicted from the minimum distance to the sea and altitude of the lakes. 4. The most remarkable result of FA was to reveal a factor correlated to DOC (positively) and NO3, (negatively). This inverse relationship might be the result either of independent processes active in the catchment soils and acting in an opposite sense, or a direct interaction, e.g. limitation of denitrification by DOC availability. Such a relationship has been reported in the recent literature in many sites and at all scales, appearing to be a global pattern that could reflect the link between the C and N cycles. 5. The concentration of NO3, is determined by both atmospheric N deposition and the processing capacity of the catchments (i.e. N uptake by plants and soil microbes). The fraction of the variability in NO3, because of atmospheric deposition is captured by an independent factor in the FA. This is the only factor showing a clear pattern when mapped over Europe, indicating lower N deposition in the northernmost areas. 6. A classification has been derived which takes into account all the major chemical features of the mountain lakes in Europe. FA provided the criteria to establish the most important factors influencing lake water chemistry, define classes within them, and classify the surveyed lakes into each class. DA can be used as a tool to scale up the classification to unsurveyed lakes, regarding sensitivity to acidification, marine influence and sources of S. [source] Reciprocal-space imaging of a real quasicrystal.JOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 4 2008A feasibility study with PILATUS 6M How many of the theoretically densely distributed Bragg reflections of a quasicrystal can be observed employing an area detector and synchrotron radiation? How does the reflection density of a real quasicrystal change as a function of exposure time, and what is the minimum distance between reflections? What does the distribution of diffuse scattering look like? To answer these questions, the Bragg reflection density of a perfect icosahedral quasicrystal with composition Al64Cu23Fe13 was measured employing a novel type of single-photon-counting X-ray pixel detector, PILATUS 6M, which allows noise-free data collection with the extraordinarily large dynamic range of 20,bit. The reflection density was found to be two orders of magnitude lower than expected for a strictly quasiperiodic structure. Moreover, diffuse scattering reflects significant structural disorder, breaking six-dimensional F -lattice symmetry. These findings have some implications for the interpretation of physical properties. [source] The gradual covering problemNAVAL RESEARCH LOGISTICS: AN INTERNATIONAL JOURNAL, Issue 6 2004Zvi Drezner Abstract In this paper we investigate the gradual covering problem. Within a certain distance from the facility the demand point is fully covered, and beyond another specified distance the demand point is not covered. Between these two given distances the coverage is linear in the distance from the facility. This formulation can be converted to the Weber problem by imposing a special structure on its cost function. The cost is zero (negligible) up to a certain minimum distance, and it is a constant beyond a certain maximum distance. Between these two extreme distances the cost is linear in the distance. The problem is analyzed and a branch and bound procedure is proposed for its solution. Computational results are presented. © 2004 Wiley Periodicals, Inc. Naval Research Logistics, 2004 [source] The Covariance Structure of Italian Male WagesTHE MANCHESTER SCHOOL, Issue 6 2000Lorenzo Cappellari Using an unbalanced panel of Italian male wages covering the 1974,88 interval, in this study we estimate the parameters of the wage covariance structure by minimum distance. Estimated variance components models allow for a linear trend in permanent wages, so that wage profile convergence can be assessed by considering the covariance between intercepts and slopes of such individual trends. Evidence of permanent wage convergence is found in the overall wage distribution, but not within white collar workers data; this contrasts with human capital interpretations of wage dynamics and suggests that other factors, such as the egalitarian wage-setting framework fully effective until the mid-1980s, could have played a major role in shaping the wage distribution. [source] Regular low-density parity-check codes from oval designsEUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 5 2003Steven R. Weller This paper presents a construction of low-density parity-check (LDPC) codes based on the incidence matrices of oval designs. The new LDPC codes have regular parity-check matrices and Tanner graphs free of 4-cycles. Like the finite geometry codes, the codes from oval designs have parity-check matrices with a large proportion of linearly dependent rows and can achieve significantly better minimum distances than equivalent length and rate randomly constructed LDPC codes. Further, by exploiting the resolvability of oval designs, and also by employing column splitting, we are able to produce 4-cycle free LDPC codes for a wide range of code rates and lengths while maintaining code regularity. Copyright © 2003 AEI. [source] | ||||||||||