Rotating and counterrotating relativistic thin disks as sources of stationary electrovacuum spacetimes

A detailed study is presented of the counterrotating model (CRM) for electrovacuum stationary axially symmetric relativistic thin disks of infinite extension without radial stress, in the case when the eigenvalues of the energy-momentum tensor of the disk are real quantities, so that there is not heat flow. We find a general constraint over the counterrotating tangential velocities needed to cast the surface energy-momentum tensor of the disk as the superposition of two counterrotating charged dust fluids. We then show that, in some cases, this constraint can be satisfied if we take the two counterrotating tangential velocities as equal and opposite or by taking the two counterrotating streams as circulating along electro-geodesics. However, we show that, in general, it is not possible to take the two counterrotating fluids as circulating along electro-geodesics nor take the two counterrotating tangential velocities as equal and opposite. A simple family of models of counterrotating charged disks based on the Kerr-Newman solution are considered where we obtain some disks with a CRM well behaved. We also show that the disks constructed from the Kerr-Newman solution can be interpreted, for all the values of parameters, as a matter distribution with currents and purely azimuthal pressure without heat flow. The models are constructed using the well-known "displace, cut and reflect" method extended to solutions of vacuum Einstein-Maxwell equations. We obtain, in all the cases, counterrotating Kerr-Newman disks that are in agreement with all the energy conditions.Comment: 22 pages, 7 figures, Late

Exchange Rate Market Expectations and Central Bank Policy: The case of the Mexican Peso-US Dollar from 2005-2009

We examine two approaches characterized by different tail features to extract market expectations on the Mexican peso-US dollar exchange rate. Expectations are gauged by risk-neutral densities. The methods used to estimate these densities are the Volatility Function Technique (VFT) and the Generalized Extreme Value (GEV) approach. We compare these methods in the context of monetary policy announcements in Mexico and the US. Once the surprise component of the announcements is considered, our results indicate that, although both VFT and GEV suggest similar dynamics at the center of the distribution, these two methods show significantly different patterns in the tails. Our empirical evidence shows that the GEV model captures better the extreme values.Exchange rates, monetary policy, risk-neutral densities

From Hydra to Humans: Insights into molecular mechanisms of aging and longevity

Human aging is characterized by progressive functional decline that coincides with both increased morbidity and mortality. Aging affects every human being and only few individuals achieve longevity, a very special phenotype marked by extraordinary healthy aging. This thesis consists of three chapters; each one is devoted to a separate project that contributes to the growing body of knowledge about aging and longevity. The work required the compilation, management and analysis of diverse big data sets and the application of cutting-edge statistical and computational methods. Chapter 1 - A functional genomics study was conducted in the potentially immortal freshwater polyp Hydra using body part-specific microarray and RNA sequencing data. The results revealed gene expression patterns that allow boundary maintenance during Hydra’s continuous cell proliferation and tissue self-renewal. Furthermore, this study provided evidence for de-acetylation as a key mechanism underlying compartmentalization. Surprisingly, FoxO, which is known to substantially drive developmental processes and stem cell renewal in Hydra, did not seem to be affected by the acetylation status. Chapter 2 - Long-lived individuals (LLI, >95 years of age) epitomize the healthy aging phenotype and are thought to carry beneficial genetic variants that predispose to human longevity. Despite extensive research efforts, only few of these genetic factors in LLI have been identified so far. In contrast to previous investigations which mainly focused on intronic variants, a genome-wide exome-based case-control study was performed. DNA samples of more than 1,200 German LLI, including 599 centenarians (≥100 years), and about 6,900 younger controls were used for single-variant and gene-based association analyses that yielded two new candidate longevity genes, fructosamine 3 kinase related protein (FN3KRP) and phosphoglycolate phosphatase (PGP). FN3KRP functions in the deglycation of proteins to restore their function, while PGP via controlling glycerol-3-phosphate levels affects both glucose and fat metabolism. Given the biological functions of the genes, their longevity-associations appear very plausible. Chapter 3 - In recent years, the intestinal microbiome (GM) has increasingly gained attention in aging and longevity research. A 16S rRNA microbiome study was conducted using 1301 stool samples of healthy individuals (age range: 19 - 104 years) that were drawn from three cohorts. The aim was to investigate potential associations among GM composition, host genetics and environmental factors during aging. The GM composition changed with age, showing an increase of opportunistic pathogens that may generate an inflammatory environment in the gut. Age explained only ~1% of the inter-individual variation, whereas anthropometric measures, genetic background and dietary patterns together explained 20%. Strikingly, clear GM population stratification in terms of four enterotype-like clusters was observed, which were predominantly associated with dietary patterns. The correction for these clusters was shown to increase the comparability of findings from the different cohorts. In addition, the LLI showed a specific gut microbial pattern, which is in line with previously published reports. The present work shows that a thorough bioinformatics expertise helps to address the complexity of the two phenotypes aging and longevity. One highlight of the thesis is the discovery of two new candidate longevity loci that, in view of the limited output of previous study approaches, enlarge the existing database

Protein Repeats from First Principles

Some natural proteins display recurrent structural patterns. Despite being highly similar at the tertiary structure level, repeating patterns within a single repeat protein can be extremely variable at the sequence level. We use a mathematical definition of a repetition and investigate the occurrences of these in sequences of different protein families. We found that long stretches of perfect repetitions are infrequent in individual natural proteins, even for those which are known to fold into structures of recurrent structural motifs. We found that natural repeat proteins are indeed repetitive in their families, exhibiting abundant stretches of 6 amino acids or longer that are perfect repetitions in the reference family. We provide a systematic quantification for this repetitiveness. We show that this form of repetitiveness is not exclusive of repeat proteins, but also occurs in globular domains. A by-product of this work is a fast quantification of the likelihood of a protein to belong to a family.Fil: Turjanski, Pablo Guillermo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Computación; ArgentinaFil: Parra, Rodrigo Gonzalo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Espada, Rocío. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Becher, Veronica Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Computación; ArgentinaFil: Ferreiro, Diego. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales; Argentin

A Survey on the Attitudes of Learners and Teachers towards the Use of the L1 in ELT in Spanish Secondary Education.

Abstract:Spanish secondary education is increasingly embracing a bilingual methodology that enables the learning of content subjects through the English language. Nevertheless, English as a foreign language teaching tends to make use of the students’ mother tongue and the use of the first language plays a controversial role which has been discussed throughout the history of second language acquisition. This dissertation focuses on the students and teachers’ attitudes towards the use of Spanish as a resource during the process of learning English. More concretely, it aims to show how students and teachers perceive that the sporadic use of Spanish in the secondary-education EFL classroom can be beneficial for learning English. For this purpose, two questionnaires were designed—one for teachers and one for students— and were completed accordingly by students and teachers in order to contribute with new insights and new research findings for the study of this subject matter. The results allow a detailed analysis about the different points of view by the participants. Both teachers and students consider the role of Spanish may be helpful for the productivity of learning English in the classroom.Resumen:La educación secundaria obligatoria en España cada vez se está adaptando más a un modelo bilingüe basado en el aprendizaje de otras materias a través del inglés como vehículo de comunicación. La enseñanza del inglés como lengua extranjera es un aprendizaje en el que se suele recurrir al uso de la lengua materna de los alumnos. Sin embargo, esta práctica ha generado mucha controversia a lo largo de la historia de la adquisición de un segundo idioma. Por ello este trabajo se centra en analizar las preferencias de los estudiantes y profesores ante el uso del español como recurso durante el proceso de aprendizaje del inglés. En concreto, el objetivo de este trabajo es demostrar cómo perciben los estudiantes y profesores que el uso esporádico del español en las clases de inglés en secundaria pueda favorecer el aprendizaje de la lengua meta. Para ello, se diseñaron dos cuestionarios que fueron completados por el alumnado y el profesorado respectivamente, con el objeto de aportar nuevos conocimientos sobre el estudio de este tema. Los resultados permiten obtener un amplio análisis con información detallada sobre los distintos puntos de vista de los participantes, los cuales consideran el uso de la lengua española como una ayuda esencial en la productividad del aprendizaje del inglés como segunda lengua.<br /

Kinetic study of pilot-scale supercritical CO2 extraction of rosemary (Rosmarinus officinalis) leaves

NOTICE: This is the author’s version of a work that was accepted for publication in Journal of Supercritical Fluids. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Journal of Supercritical Fluids, 55 (2011). http://dx.doi.org/10.1016/j.supflu.2010.09.030Rosmarinus officinalis (rosemary) extracts were obtained in a supercritical pilot-scale plant. Based on experimental information available in the literature for analytical or low-scale processes, extraction temperature and pressure were selected to be 313 K and 30 MPa. At these extraction conditions, the kinetic behavior of the pilot-scale overall extraction curve were determined with respect to yield, antioxidant activity and carnosic acid content. The overall extraction curve was represented using Sovova’s model; the average deviation between measured and calculated yields was lower than 2%. Mass transfer coefficients in the fluid and solid phases were determined and were compared with previous data reported in the literature for low-scale rosemary supercritical extraction. A two-stage depressurization procedure was accomplished and the effect of both on-line fractionation and extraction time on the antioxidant activity of the samples collected was studied. The antioxidant activity of the different fractions could be straight correlated with the carnosic acid content with a regression coefficient of 0.92This work has been financed by Universidad Autónoma de Madrid and Comunidad Autónoma de Madrid (ALIBIRD-S2009/AGR-1469) and project FUN-C-FOOD, CSD2007-00063 (CONSOLIDER-INGENIO) from Ministerio de Ciencia e Innovación, Spain