Modified spinning black holes

In the context of f(R) modified gravity theories we determine that the black holes existence is determined by the sign of a parameter dependent of the mass, the charge, the spin and the scalar curvature. We obtain the different astrophysical objects derived from the presence of different horizons. Thermodynamics for this kind of black holes is studied for negative values of the curvature, revealing that we can distinguish between two kinds of BH: fast and slow.Comment: 4 pages, 6 figures, Contribution to the ERE2011 Spanish Relativity Meeting, Madrid 201

The test of Random Rhythm Generation and neuropsychological performance in schizophrenic patients

Producción CientíficaThe objective of this study was the assessment of neuropsychological performance in a sample of schizophrenic patients using a new computer-administered instrument, the Test of Random Rhythm Generation (ARG). The test was applied to a group of 20 DSM-IV schizophrenic patients (SG) and 20 sex- and age-matched controls (CG). The Positive and Negative Syndrome Scale (PANSS) and Frankfurt Complaint Questionnaire (Frankfurter Beschwerdefragebogen, FBF) were used to study patients' psychopathology. The neuroleptic treatment received by each patient during the last month was converted into daily equivalents of chlorpromazine. In the ARG, the subject is asked to press the space key of the computer at a rhythm as irregular as possible. The test aims at assessing the individual's ability to create random rhythms by means of sequences of blows, which is hypothetically associated with a high neuropsychological performance. The data were analyzed by means of three different mathematical techniques. Results showed that schizophrenic patients generated more regular and rhythmic sequences than controls (correlation dimension in SG = 2.78 +/- 0.81, in CG = 3.69 +/- 0.64, p < 0.01). This suggests that neuropsychological performance measured by the ARG was worse in patients compared to controls. ARG is proposed as a new technique to evaluate neuropsychological performance with the following advantages: (1) its short-time application tit usually takes no more than 10 minutes), (2) personnel only require a short training to learn how to apply it, and (3) different analyses of the data are quickly carried out by the computer program

Collocation analysis for UMLS knowledge-based word sense disambiguation

BACKGROUND: The effectiveness of knowledge-based word sense disambiguation (WSD) approaches depends in part on the information available in the reference knowledge resource. Off the shelf, these resources are not optimized for WSD and might lack terms to model the context properly. In addition, they might include noisy terms which contribute to false positives in the disambiguation results. METHODS: We analyzed some collocation types which could improve the performance of knowledge-based disambiguation methods. Collocations are obtained by extracting candidate collocations from MEDLINE and then assigning them to one of the senses of an ambiguous word. We performed this assignment either using semantic group profiles or a knowledge-based disambiguation method. In addition to collocations, we used second-order features from a previously implemented approach.Specifically, we measured the effect of these collocations in two knowledge-based WSD methods. The first method, AEC, uses the knowledge from the UMLS to collect examples from MEDLINE which are used to train a Naïve Bayes approach. The second method, MRD, builds a profile for each candidate sense based on the UMLS and compares the profile to the context of the ambiguous word.We have used two WSD test sets which contain disambiguation cases which are mapped to UMLS concepts. The first one, the NLM WSD set, was developed manually by several domain experts and contains words with high frequency occurrence in MEDLINE. The second one, the MSH WSD set, was developed automatically using the MeSH indexing in MEDLINE. It contains a larger set of words and covers a larger number of UMLS semantic types. RESULTS: The results indicate an improvement after the use of collocations, although the approaches have different performance depending on the data set. In the NLM WSD set, the improvement is larger for the MRD disambiguation method using second-order features. Assignment of collocations to a candidate sense based on UMLS semantic group profiles is more effective in the AEC method.In the MSH WSD set, the increment in performance is modest for all the methods. Collocations combined with the MRD disambiguation method have the best performance. The MRD disambiguation method and second-order features provide an insignificant change in performance. The AEC disambiguation method gives a modest improvement in performance. Assignment of collocations to a candidate sense based on knowledge-based methods has better performance. CONCLUSIONS: Collocations improve the performance of knowledge-based disambiguation methods, although results vary depending on the test set and method used. Generally, the AEC method is sensitive to query drift. Using AEC, just a few selected terms provide a large improvement in disambiguation performance. The MRD method handles noisy terms better but requires a larger set of terms to improve performance

State Capacity and Economic Development: A Network Approach

We study the direct and spillover effects of local state capacity using the network of Colombian municipalities. We model the determination of local and national state capacity as a network game in which each municipality, anticipating the choices and spillovers created by other municipalities and the decisions of the national government, invests in local state capacity and the national government chooses the presence of the national state across municipalities to maximize its own payoff. We then estimate the parameters of this model using reduced-form instrumental variables techniques and structurally (using GMM, simulated GMM or maximum likelihood). To do so we exploit both the structure of the network of municipalities, which determines which municipalities create spillovers on others, and the historical roots of local state capacity as the source of exogenous variation. These historical instruments are related to the presence of colonial royal roads and local presence of the colonial state in the 18th century, factors which we argue are unrelated to current provision of public goods and prosperity except through their impact on their own and neighbors’ local state capacity. Our estimates of the effects of state presence on prosperity are large and also indicate that state capacity decisions are strategic complements across municipalities. As a result, we find that bringing all municipalities below median state capacity to the median, without taking into account equilibrium responses of other municipalities, would increase the median fraction of the population above poverty from 57% to 60%. Approximately 57% of this is due to direct effects and 43% to spillovers. However, if we take the equilibrium response of other municipalities into account, the median would instead increase to 68%, a sizable change driven by equilibrium network effects.We are grateful to Alberto Ciancio, Amanda Culp, and Nicolas Idrobo for superb research assistance, and Maria Angelica Bautista, Flavio Cunha, Frank Ditraglia, Andrew Foster, Elena Paltseva, James Poterba, Pascual Restrepo, Xun Tang, Petra Todd, Ken Wolpin, Roman Zarate, participants at the Stockholm School of Economics/SITE conference on Institutional Challenges in Emerging Economies, participants at the George Mason center for Public Choice Seminar, and participants at the RECODE 2013 Meetings in Ottawa, the BREAD/NBER development meetings in Cambridge, the LACEA/LAMES meetings in Mexico City, the MIT Public Finance/labor Workshop, and the UPenn Empirical Micro Workshop for valuable suggestions. Acemoglu gratefully acknowledges financial support from ARO MURI W911NF-12-1-0509

The Myth of the Frontier

One of the most salient explanations for the distinctive path of economic and political development of the United States is captured by the 'Frontier (or Turner) thesis'. Turner argued that it was the presence of the open frontier which explained why the United States became democratic and, at least implicitly, prosperous. In this paper we provide a simple test of this idea. We begin with the contradictory observation that almost every Latin American country had a frontier in the 19th century as well. We show that while the data does not support the Frontier thesis, it is consistent with a more complex 'conditional Frontier thesis.' In this view, the effect of the frontier is conditional on the way that the frontier was allocated and this in turn depends on political institutions at the time of frontier expansion. We show that for countries with the worst political institutions, there is a negative correlation between the historical extent of the frontier and contemporary income per-capita. For countries with better political institutions this correlation is positive. Though the effect of the frontier on democracy is positive irrespective of initial political institutions, it is larger the better were these institutions. In essence, Turner saw the frontier as having positive effects on development because he already lived in a country with good institutions.

Luxación traumática anterior de prótesis total de rodilla

Se presenta un caso de luxación anterior de una prótesis total de rodilla no constreñida que conserva el ligamento cruzado posterior. Su etiopatogenia es diferente a la de las subluxaciones o luxaciones posteriores de prótesis totales de rodilla semiconstreñidas que no conservan el ligamento cruzado posterior. La reducción de la misma se consiguió sin dificultad bajo anestesia general. A pesar de la laxitud residual existente tras el tratamiento conservador, el resultado funcional después de 4 años fue satisfactorio y sin evidenciar nuevos episodios de subluxación o reluxación de la prótesis

Employment Expectations and Gross Flows by Type of Work Contract

There is growing interest in understanding firms’ temporary and permanent employment practices and how institutional changes shape them. Using data on Spanish establishments, we examine: (a) how employers adjust temporary and permanent job and worker flows to prior employment expectations, and (b) how the 1994 and 1997 labour reforms promoting permanent employment affected establishments’ employment practices. Generally, establishments’ prior employment expectations are realized through changes in all job and worker flows. However, establishments uniquely rely on temporary hires as a buffer to confront diminishing long-run employment expectations. None of the reforms significantly affected establishments’ net temporary or permanent employment flows.http://deepblue.lib.umich.edu/bitstream/2027.42/40032/3/wp646.pd

Accounting for changes in the Spanish wage distribution : the role of employment composition

A pesar de una rápida disminución del desempleo, los salarios reales en España apenas aumentaron durante el periodo 1995-2006. Una posible explicación de este comportamiento se refiere a la importancia de los efectos composición derivados de algunos cambios estructurales, tales como el aumento del peso del empleo en la construcción y en el sector servicios, el incremento de la participación laboral femenina, y la llegada masiva de inmigrantes. Utilizando datos de tres olas de la Encuesta de Estructura Salarial, se descompone la variación salarial observada durante este periodo en dos componentes, el debido a los cambios en las características de los puestos de trabajo y de los trabajadores, y el causado por los cambios en los rendimientos de dichas características. Así, mediante regresiones cuantílicas que estiman ecuaciones de salarios condicionadas a determinados percentiles de la distribución salarial, se construyen las istribuciones contrafactuales que se hubieran observado de haberse mantenido constantes las características de los puestos de trabajo y de los trabajadores. El principal resultado es que la falta de crecimiento de los salarios reales en España durante el periodo 1995-2006 se debe, sobre todo, a la caída de los rendimientos, especialmente de la educación y de la experiencia laboral en los deciles elevados de la distribución salarial, y no tanto a cambios en la composición del empleo que, computados sobre un conjunto amplio de características, tuvieron un efecto global positivo sobre los salario