Aportaciones previas sobre la presencia y petrografía de rocas ultramáficas asociadas a granitoides calcoalcalinos precoces en la zona de Vivero (Lugo)

[Resumen] Asociadas con tonalitas, granodioritas y adamellitas, pertenecientes a la serie calcoalcalina precoz de granitos hercínicos, aparecen en la zona de Vivero unas rocas que muestran características diferentes a las de otros tipos relacionados con granitos hercínicos de esta serie en el NW. de la Península. Se trata de rocas ultramáficas y máficas con carácter básico en afloramientos cartografiables, presentando diversos tipos petrográficos, desde peridotitas a hornblenditas, incluyendo también gabros/ dioritas, monzonitas y melanotonalitas[Abstract] In the Vivero area (Lugo), there are some ultramafic and mafic rocks associated with tonalites, granodiorites and adamellites belonging to the older Hercynian calc-alcaline granite serie. These rocks show different characteristics to those of other types related to these granites in the NW. of Spain, appearing in quite large outcróps including severaI petrographic types from peridotites to hornblendites; gabbros/diorites, monzonites and melatonalite

Entropy and temperature of black holes in a gravity's rainbow

The linear relation between the entropy and area of a black hole can be derived from the Heisenberg principle, the energy-momentum dispersion relation of special relativity, and general considerations about black holes. There exist results in quantum gravity and related contexts suggesting the modification of the usual dispersion relation and uncertainty principle. One of these contexts is the gravity's rainbow formalism. We analyze the consequences of such a modification for black hole thermodynamics from the perspective of two distinct rainbow realizations built from doubly special relativity. One is the proposal of Magueijo and Smolin and the other is based on a canonical implementation of doubly special relativity put forward recently by the authors. In these scenarios, we obtain modified expressions for the entropy and temperature of black holes. We show that, for a family of doubly special relativity theories satisfying certain properties, the temperature can vanish in the limit of zero black hole mass. For the Magueijo and Smolin proposal, this is only possible for some restricted class of models with bounded energy and unbounded momentum. With the proposal of a canonical implementation, on the other hand, the temperature may vanish for more general theories; in particular, the momentum may also be bounded, with bounded or unbounded energy. This opens new possibilities for the outcome of black hole evaporation in the framework of a gravity's rainbow.Comment: 11 pages, 2 new references added, version accepted for publication in Physical Review

Inefficiency persistence and heterogeneity in Colombian electricity distribution utilities

The electricity reform in Colombia has exhibited gains in terms of reliability but its effects on firms efficiency and service quality have not been clear. Previous studies evaluating the performance of distribution companies after the reform have not found evidence of improvements, although large differences in efficiency have been found among firms. This suggests high inefficiency persistence and heterogeneity in the Colombian distribution sector. In this paper, we propose an extension of dynamic stochastic frontier models that accounts for unobserved heterogeneity in the inefficiency persistence and in the technology. The model incorporates total expenses, service quality and energy losses in an efficiency analysis of Colombian distributors over fifteen years after the reform. We identify the presence of high inefficiency persistence in the sector, and important differences between firms. In particular, rural companies and firms with small customers present low persistence and evidence the largest gains in efficiency during the period. However, increases in efficiency are only manifested during the last five years when the main improvements in service quality and energy losses are presented. Overall, inefficiency persistence, customer density and consumption density are found to be important criteria to be considered for regulatory purposes

Inefficiency persistence and heterogeneity in Colombian electricity distribution utilities

The electricity reform in Colombia has exhibited gains in terms of reliability but its effects on firms efficiency and service quality have not been clear. Previous studies evaluating the performance of distribution companies after the reform have not found evidence of improvements, although large differences in efficiency have been found among firms. This suggests high inefficiency persistence and heterogeneity in the Colombian distribution sector. In this paper, we propose an extension of dynamic stochastic frontier models that accounts for unobserved heterogeneity in the inefficiency persistence and in the technology. The model incorporates total expenses, service quality and energy losses in an efficiency analysis of Colombian distributors over fifteen years after the reform. We identify the presence of high inefficiency persistence in the sector, and important differences between firms. In particular, rural companies and firms with small customers present low persistence and evidence the largest gains in efficiency during the period. However, increases in efficiency are only manifested during the last five years when the main improvements in service quality and energy losses are presented. Overall, inefficiency persistence, customer density and consumption density are found to be important criteria to be considered for regulatory purposes

Inefficiency persistence and heterogeneity in Colombian electricity utilities

The electricity reform in Colombia has exhibited gains in terms of reliability but its effects on firm efficiency and service quality have not been clear. Previous studies evaluating the performance of distribution companies after the reform have not found evidence of improvements, although large differences in efficiency have been found among firms. This suggests high inefficiency persistence and heterogeneity in the Colombian distribution sector. In this paper, we propose an extension of dynamic stochastic frontier models that accounts for unobserved heterogeneity in the inefficiency persistence and in the technology. The model incorporates total expenses, service quality and energy losses in an efficiency analysis of Colombian distributors over fifteen years after the reform. We identify the presence of high inefficiency persistence in the sector, and important differences between firms. In particular, rural companies and firms with small customers present low persistence and evidence the largest gains in efficiency during the period. However, increases in efficiency are only manifested during the last five years when the main improvements in service quality and energy losses are presented. Overall, inefficiency persistence, customer density and consumption density are found to be important criteria to be considered for regulatory purposes.Jorge E. Galán acknowledges from the Energy Policy Research Group at the University of Cambridge and the financial support Spanish Ministry of Education and Science, research project ECO2012-3401

Improving classification for brain computer interfaces using transitions and a moving window

Proceeding of: Biosignals 2009. International Conference on Bio-inspired Systems and Signal Processing, BIOSTEC 2009. Porto (Portugal), 14-17 January 2009The context of this paper is the brain-computer interface (BCI), and in particular the classification of signals with machine learning methods. In this paper we intend to improve classification accuracy by taking advantage of a feature of BCIs: instances run in sequences belonging to the same class. In that case, the classiffication problem can be reformulated into two subproblems: detecting class transitions and determining the class for sequences of instances between transitions. We detect a transition when the Euclidean distance between the power spectra at two different times is larger than a threshold. To tackle the second problem, instances are classified by taking into account, not just the prediction for that instance, but a moving window of predictions for previous instances. Experimental results show that our transition detection method improves results for datasets of two out of three subjects of the BCI III competition. If the moving window is used, classification accuracy is further improved, depending on the window size.Publicad

Los pinceles de la química

La química desarrolla un papel muy importante en diferentes campos de investigación. Normalmente cuando se habla de química la gente piensa en reacciones y síntesis de nuevos proyectos. Sin embargo, un campo poco conocido para la química es el mundo de la restauración de pinturas. Nombres tan conocidos como Lewis, Hückel, Diels-Alder se imparten en nuestras aulas, pero por qué se menosprecia los disolventes. Los solventes son muy importantes en las reacciones químicas aunque muchas veces los obviemos. En cambio, toman mucha relevancia al restaurar pinturas