Suchergebnisse

La actividad humana ha ido en aumento en el continente antártico, lo que ha significado un impacto en áreas litorales por medio de los residuos, los cuales afectan a las comunidades bentónicas intermareales que han sido poco estudiadas. El presente estudio tiene como objetivo determinar los parámetros comunitario de los macroinvertebrados bentónicos en el intermareal de bahía Chile/Discovery (Isla Greenwich) y su relación con variables fisicoquímicas (materia orgánica, hidrocarburos totales del petróleo, fósforo libre y nitrógeno total) en las proximidades del emisario de la base naval Arturo Prat. Para ello, se tomaron muestras de sedimento en dos transectos paralelos a la línea de costa, los cuales estaban ubicados a ambos lados del emisario a 25, 50, 200 y 300 metros de distancia. Se identificaron un total de 10 taxones de los cuales Harpacticoidea y Oligochaeta fueron los más abundante. Los valores de abundancia por muestra variaron entre 256 y 12.176 (Ind*m-2). Mientras que el promedio del índice de Shannon-Wiener (H') varió entre 0,57 (± DS= 0,53) y 1,32 (± DS= 1,26) y la uniformidad promedio (J´) varió entre 0,32 (± DS= 0,29) y 0,63 (± DS= 0,60). El análisis de componentes principales mostró una relación directa entre la abundancia y la concentración de las variables fisicoquímicas. La composición del sedimento intermareal estuvo compuesta principalmente por Arena muy gruesa y Grava en las estaciones muestreadas. Por otro lado, los resultados obtenidos muestran que las variables fisicoquímicas, composición taxonómica, equidad y valores de diversidad eran similares a las obtenidas para otras áreas de la Isla Rey Jorge.

We present a broadband ferromagnetic resonance study of the Gilbert damping enhancement (α) due to spin pumping in NiFe/Pt bilayers. The bilayers, which have negligible interfacial spin memory loss, are studied as a function of the Pt layer thickness (tPt) and temperature (100–293 K). Within the framework of diffusive spin pumping theory, we demonstrate that Dyakonov-Perel (DP) or Elliot-Yaffet (EY) spin relaxation mechanisms acting alone are incompatible with our observations. In contrast, if we consider that the relation between spin relaxation characteristic time (τs) and momentum relaxation characteristic time (τp) is determined by a superposition of DP and EY mechanisms, the qualitative and quantitative agreement with experimental results is excellent. Remarkably, we found that τp must be determined by the out-of-plane electrical resistivity (ρ) of the Pt film and hence its spin diffusion length (λPt) is independent of tPt. Our work settles the controversy regarding the tPt dependence of λPt by demonstrating its fundamental connection with ρ considered along the same direction of spin current flow. ; This work was supported by FONDECYT Grant No. 3170908, ANID FONDECYT/REGULAR 1201102, ANID PIA/APOYO AFB180002, ANID FONDEQUIP EQM140161, and European Union's Horizon 2020 research and innovation program under the Marie Skłodowska-Curie Grant Agreement No. 645658 (DAFNEOX Project). ; Peer reviewed

We propose a semiparametric nonlinear mixed-effects model (SNMM) using penalized splines to classify longitudinal data and improve the prediction of a binary outcome. The work is motivated by a study in which different hormone levels were measured during the early stages of pregnancy, and the challenge is using this information to predict normal versus abnormal pregnancy outcomes. The aim of this paper is to compare models and estimation strategies on the basis of alternative formulations of SNMMs depending on the characteristics of the data set under consideration. For our motivating example, we address the classification problem using a particular case of the SNMM in which the parameter space has a finite dimensional component (fixed effects and variance components) and an infinite dimensional component (unknown function) that need to be estimated. The nonparametric component of the model is estimated using penalized splines. For the parametric component, we compare the advantages of using random effects versus direct modeling of the correlation structure of the errors. Numerical studies show that our approach improves over other existing methods for the analysis of this type of data. Furthermore, the results obtained using our method support the idea that explicit modeling of the serial correlation of the error term improves the prediction accuracy with respect to a model with random effects, but independent errors. ; The first author was supported by Proyecto DI Regular 37.0/2016 VRIEA PUCV; FONDECYT grants 1120739, 1130233, and 1141256; Ministerio de Economía y Competitividad and FEDER, Spain, grants MTM2013-40941-P and MTM2016-74931-P; FONDAP grant 15130011; and grant 16-MATH-03 SIDRE from CONICYT MATH-AmSud Program. The third author was supported by FONDECYT grant 1141256; and grant 16-MATH-03 SIDRE from CONICYT MATH-AmSud Program. The fourth author was supported by the Basque Government through the BERC 360 2014-2017 and the Department of Education, Language Policy and Culture of the Basque Government IT-620-13 programs and Basque Government Industry Department under the ELKARTEK Program, by the Spanish Ministry of Economy and Competitiveness MINECO: BCAM Severo Ochoa excellence accreditation SEV-2013-0323 and MTM2014-52184-P, and by the RISE Horizon 2020 European Project GEAGAM (644602). The fifth author was funded by grants MTM2014-56535-R and ECO2015-66593-P of the Ministerio de Economía y Competitividad, Spain. Contributions of the second, fourth, and fifth authors were partially supported by grants FONDECYT1120739 and 1141256 while visiting PUCV and CIMFAV-UV.

Enthält u.a. Rezensionen von: Agosin, Marjorie: Tapestries of hope, threads of love: The Arpillera movement in Chile, 1974-1994. - Albuquerque : University of New Mexico Press, 1996. - 142 S

How was Chile transformed both politically and economically during the two decades of center-left coalition (Concertación) government that followed the country's return to democracy in 1990? How did the coalition manage to hold on to power for so long—but not longer? And were its policies in fact substantially different from those that preceded them? Addressing these questions, the authors of this landmark volume critically assess the successes and failures of Concertación politics and policies in post-Pinochet Chile