Optimal random sampling designs in random field sampling

A Horvitz-Thompson predictor is proposed for spatial sampling when the characteristic of interest is modeled as a random field. Optimal sampling designs are deduced under this context. Fixed and variable sample size are considered

Application of interpolation methods and geostatistical modeling in the evaluation of air quality in Bogotá D.C.

En el presente trabajo se presenta la aplicación de diferentes métodos de interpolación espacial de las mediciones de concentraciones de contaminantes atmosféricos obtenidos por la Red de Monitoreo de Calidad del Aire en las estaciones fijas ubicadas en diferentes puntos del distrito capital, para obtener superficies completas del territorio con el objeto de determinar las diferencias entre los métodos y realizar predicciones más precisas del nivel de contaminación en cualquier parte del área de estudio que puedan proporcionar información más realista de la calidad del aire en Bogotá DC.In this paper we present how to use different methods of spatial interpolation of the measurements of concentrations of air pollutants given by the RMCAB in the fixed stations in Bogota and obtain wider surfaces of the territory. All of this to determine the differences between them and be able to make more accurate predictions of the contamination in any area, this will result in a more precise data about the quality of the air in Bogota, DC

Dirac Matrices for Chern-Simons Gravity

A genuine gauge theory for the Poincar\'e, de Sitter or anti-de Sitter algebras can be constructed in (2n-1)-dimensional spacetime by means of the Chern-Simons form, yielding a gravitational theory that differs from General Relativity but shares many of its properties, such as second order field equations for the metric. The particular form of the Lagrangian is determined by a rank n, symmetric tensor invariant under the relevant algebra. In practice, the calculation of this invariant tensor can be reduced to the computation of the trace of the symmetrized product of n Dirac Gamma matrices \Gamma_{ab} in 2n-dimensional spacetime. While straightforward in principle, this calculation can become extremely cumbersome in practice. For large enough n, existing computer algebra packages take an inordinate long time to produce the answer or plainly fail having used up all available memory. In this talk we show that the general formula for the trace of the symmetrized product of 2n Gamma matrices \Gamma_{ab} can be written as a certain sum over the integer partitions s of n, with every term being multiplied by a numerical coefficient \alpha_{s}. We then give a general algorithm that computes the \alpha-coefficients as the solution of a linear system of equations generated by evaluating the general formula for different sets of tensors B^{ab} with random numerical entries. A recurrence relation between different coefficients is shown to hold and is used in a second, "minimal" algorithm to greatly speed up the computations. Runtime of the minimal algorithm stays below 1 min on a typical desktop computer for up to n=25, which easily covers all foreseeable applications of the trace formula.Comment: v2: 6 pages, no figures. Based on talk presented at I Cosmosul, Rio de Janeiro, Brazil, August 2011. v3: references adde

El humanismo renacentista: esbozo y actualidad

Vuitenes Jornades de Foment de la Investigació de la FCHS (Any 2002-2003

OPTIMAL RANDOM SAMPLING DESIGNS IN RANDOM FIELD SAMPLING

A Horvitz-Thompson predictor is proposed for spatial sampling when the characteristic of interest is modeled as a random field. Optimal sampling designs are deduced under this context. Fixed and variable sample size are considered.

Can fundamentals explain cross-country correlations of asset returns?.

Previous studies show that existing correlations between national returns are higher than correlations between the national growth rates of fundamental variables. This paper examines the ability of intertemporal asset pricing models to explain cross-country correlations of national returns. We find that when capital markets are assumed to be fully integrated, a simple intertemporal general equilibrium model is able to explain the observed co-variability of domestic asset returns but generates too little variability in those returns. Results improve considerably if a less restrictive version is employed. In that setting, both domestic variability and cross-country co-variability of returns are consistent with capital market integration.Asset pricing models; Cross-country correlations;

Control of lactate accumulation in ruminants using Prevotella bryantii

Overfeeding ruminants with readily fermentable carbohydrates alters the normal balance of microbes in the rumen compartment causing changes in the fermentation pattern and rumen function. The resulting increase in the molar concentrations of ruminal lactate and/or volatile fatty acids (VFAs), and a decrease in ruminal pH may lead animals to experience acute or subacute acidosis. The objective of this study was to test the hypothesis that lactic acid accumulation can be inhibited by inoculating the rumen with volatile acid-producing bacteria that would compete with lactic acid-producing bacteria for substrate (starch).;We used strain 25A of Prevotella bryantii that had been selected as a rapid starch fermenter from a mixed rumen population as a rumen inoculum for in vitro or in vivo ruminal fermentations. In studies conducted in vitro; strain 25A reduced the accumulation of lactate by 90% when added to mixed rumen fermentations that contained excess soluble carbohydrates, and cultures had greater amounts of succinate and propionate compared with the controls. Morphological, biochemical and genetic analysis (sequencing of the 16S rRNA gene) indicated that strain 25A is related to Prevotella bryantii. Amylolytic strain 25A showed an ability to reduce ruminal lactate accumulation (85%) in goats in a model of acute acidosis, and was able to drive starch fermentation to VFAs and away from lactate accumulation. When the ability of this bacterium to prevent lactate accumulation was tested in lactating cows, ruminal pH was favourable (above 6) and lactate accumulation was reduced, but significant changes in ruminal VFA profile and animal milk yields were not observed

A low-power reconfigurable ADC for biomedical sensor interfaces

This paper presents a 12-bit low-voltage low-power reconfigurable Analog-to-Digital Converter (ADC). The design employs Switched Capacitor (SC) techniques and implements a Successive Approximation (SA) algorithm. The ADC can be tuned to handle a large variety of biopotential signals, with digitally selectable resolution and input signal amplitude. It achieves 10.4-bit of effective resolution sampling at 56kS/s, with a power consumption below 3μW from a 1V voltage supply.Ministerio de Educación y Ciencia TEC2006-03022Junta de Andalucía TIC-0281