On the Whitham Hierarchies: Reductions and Hodograph Solutions

A general scheme for analyzing reductions of Whitham hierarchies is presented. It is based on a method for determining the $S$-function by means of a system of first order partial differential equations. Compatibility systems of differential equations characterizing both reductions and hodograph solutions of Whitham hierarchies are obtained. The method is illustrated by exhibiting solutions of integrable models such as the dispersionless Toda equation (heavenly equation) and the generalized Benney system.Comment: 24 page

Recycling probability and dynamical properties of germinal center reactions

We introduce a new model for the dynamics of centroblasts and centrocytes in a germinal center. The model reduces the germinal center reaction to the elements considered as essential and embeds proliferation of centroblasts, point mutations of the corresponding antibody types represented in a shape space, differentiation to centrocytes, selection with respect to initial antigens, differentiation of positively selected centrocytes to plasma or memory cells and recycling of centrocytes to centroblasts. We use exclusively parameters with a direct biological interpretation such that, once determined by experimental data, the model gains predictive power. Based on the experiment of Han et al. (1995b) we predict that a high rate of recycling of centrocytes to centroblasts is necessary for the germinal center reaction to work reliably. Furthermore, we find a delayed start of the production of plasma and memory cells with respect to the start of point mutations, which turns out to be necessary for the optimization process during the germinal center reaction. The dependence of the germinal center reaction on the recycling probability is analyzed.Comment: 30 pages, 8 figure

«No levantes la voz».

Sin resume

SNR-calibrated Type Ia supernova models

Current Type Ia supernova (SN Ia) models can reproduce most visible+IR + UV observations. In the X-ray band, the determination of elemental abundance ratios in supernova remnants (SNRs) through their spectra has reached enough precision to constrain SN Ia models. Martínez-Rodríguez et al have shown that the Ca/S mass ratio in SNRs cannot be reproduced with the standard nuclear reaction rates for a wide variety of SN Ia models, and suggested that the 12C+16O reaction rate could be overestimated by a factor as high as ten. We show that the same Ca/S ratio can be obtained by simultaneously varying the rates of the reactions 12C + 16O, 12C + 12C, 16O + 16O, and 16O(¿, a)12C within the reported uncertainties. We also show that the yields of the main products of SN Ia nucleosynthesis do not depend on the details of which rates are modified, but can be parametrized by an observational quantity such as Ca/S. Using this SNR-calibrated approach, we then proceed to compute a new set of SN Ia models and nucleosynthesis for both Chandrasekhar and sub-Chandrasekhar mass progenitors with a 1D hydrodynamics and nucleosynthesis code. We discuss the nucleosynthesis of the models as a function of progenitor metallicity, mass, and deflagration-to-detonation transition density. The yields of each model are almost independent on the reaction rates modified for a common Ca/S ratio.Peer ReviewedPostprint (author's final draft

El modelo textual de Basilea y en efecto

El objetivo de este trabajo es presentar un análisis de en efecto, adoptando un modelo textual (Modelo de Basilea) elaborado fundamentalmente a partir de la lengua italiana. El análisis parte de asumir la hipótesis de que el valor informativo asociado con una dada expresión lingüística juega un papel fundamental en la determinación de su función, alcance y relieve. Igualmente se tratará de poner de manifiesto la problemática que genera el no coincidente uso de la puntuación en italiano y español, por lo que a los marcadores discursivos se refiere.This paper’s goal is to offer an analysis of the Spanish item en efecto using a text model (Basel Model) that has been elaborated mainly on the basis of Italian language’s data. The analysis is based on assuming the hypothesis that the information value associated with a given linguistic expression plays a critical role in determining its function, scope and relief. Also the paper will seek to highlight the problems generated by the mismatched punctuation in Italian and Spanish, in terms of discursive markers

Armored glass university ceilings

Las barreras que encuentran las mujeres para ocupar las más altas posiciones profesionales están bien estudiadas, pese a lo cual persisten. La situación laboral de las mujeres ha mejorado, pero los puestos de responsabilidad siguen mayoritariamente en manos masculinas, como si los varones buscaran continuamente nuevos mecanismos de mantenerse en el poder, de manera similar a los virus que año tras se modifican para sobrevivir a las vacunas. Las barreras persisten, a pesar de que en las últimas décadas las alumnas hayan conseguido superar en cantidad y calidad a los varones entre el alumnado universitario. Las mujeres siguen sin poder acceder a las mejores posiciones académicas. Entre el profesorado universitario apenas llegan al 40% y las cátedras siguen estando masculinizadas, habiendo conseguido las mujeres llegar -después de muchos esfuerzos y algunas medidas políticas- a tan sólo el 20%, lo que se vislumbra a todas luces insuficiente dada su mayor formación. Ante este panorama, el futuro se presenta difícil, salvo que la institución universitaria decidiera hacer suya la causa de la Igualdad, pasando a asumir su importante papel referente para las nuevas generaciones, para el resto de organizaciones y para la sociedad en general.The barriers that women face to occupy the highest professional positions are well studied, yet they persist. The employment situation of women has improved, but the positions of power are still predominantly in male hands, as if men continually seek new mechanisms to keep, like viruses that change every year to survive the way vaccines. Barriers persist, although in recent decades women have managed to overcome in quantity and quality to men among university students. Women are still unable to access the best academic positions. Among university faculty only reach 40% and full professor position remain masculinized, having managed to reach the women -after many efforts and some policies- measures only 20%, which is seen clearly insufficient given their greater training. Against this background, the future is difficult, unless the university decided to endorse the cause of equality, going to assume its role of reference for the new generations and to other organizations and society in general