A wide family of singularity-free cosmological models

In this paper a family of non-singular cylindrical perfect fluid cosmologies is derived. The equation of state corresponds to a stiff fluid. The family depends on two independent functions under very simple conditions. A sufficient condition for geodesic completeness is provided.Comment: 7 pages, RevTeX

Average power prediction in microcells

A propagation model to estimate the average received power in an urban microcell environment has been developed. This model can be used both in line of sight (LOS) and non line of sight (NLOS) conditions in any regular or irregular microcell structure.Peer ReviewedPostprint (published version

High-frequency collective excitations in molten and glassy Te studied by inelastic neutron scattering

7 págs.; 5 figs.; 1 tab. ; PACS number s : 61.25.Mv, 61.43.Er, 61.20.Lc, 61.12. qhttp://dx.doi.org/10.1103/PhysRevB.73.094201The spectra of collective excitations of liquid and glassy tellurium have been studied by means of inelastic neutron scattering. Here we report on the dynamics of liquid Te as measured at two different temperatures, just above melting (Tm =723 K) and at ∼1000 K as well as the glass that is studied at room temperature. Estimates for the velocity of propagating excitations for both temperatures have been obtained from the experimental data, and a contrasting behavior is found with respect to anomalies shown by the adiabatic sound velocity measured by ultrasound methods. The origin of such differences is finally discussed. © 2006 The American Physical Society.This work was supported in part by Grant No. MAT2002- 04178-C04 SpainPeer Reviewe

BDAFRICA: Design and implementation of a database of Postcolonial African literature published in Spain

Este trabajo demuestra que no existe un repositorio que incluya los autores poscoloniales africanos publicados hasta el momento en España y que permita, por ende, realizar estudios cuantitativos y cualitativos del impacto de esta literatura con la precisión deseable. Esto supone una carencia tanto para investigaciones académicas como para el sector editorial a la hora de analizar tendencias de selección y recepción en el mercado. Ante esta situación, el objetivo primordial de este trabajo es diseñar e implementar una base de datos, basada en MySQL y delimitada por unos parámetros muy concretos, que recoja todas las obras de autores africanos publicadas en castellano en España entre 1972 (año en que España se unió al sistema ISBN) y 2014. Tras determinar unos criterios de diseño y unos protocolos de compilación específcos, el desarrollo metodológico se ha dividido en cuatro fases: recopilación, almacenamiento, tratamiento y difusión de los datos. Así, la base de datos BDÁFRICA consigue un doble objetivo: por un lado, proporciona a los investigadores datos fables en los que basar sus estudios y, por otro, permitiría ofrecer por primera vez datos estadísticos de la evolución de la publicación de obras de autores africanos en España en los últimos 42 años.English version of abstract: This paper evidences the absence of a repository or database that scompiles the publications of Postcolonial African writing in Spain, thus precluding comprehensive quantitative or qualitative studies on the impact of these works. This is a significant obstacle for both academic research and the book market, which up to now has been unable to analyse market selection and reception trends. To cater for this need, the aim of this paper is to describe the design and implementation of a relational database, based on MySQL and set up using specific and accurate parameters, that includes all the literary works penned by African writers and published in Spain and in Spanish from 1972 (when Spain first joined the ISBN system) to 2014. After determining a number of specific design criteria and compilation protocols, the methodology has been divided into four steps: data collection, storage, statistical processing and online dissemination. Thus, the database BDAFRICA achieves a twofold objective: firstly, it provides researchers with unbiased data as a framework for their studies, and secondly, it offers unprecedented statistics on the evolution of the publication of African literature in Spain over the last 42 years.Published versio

Non-singular radiation cosmological models

In this paper we analyse the possibility of constructing singularity-free inhomogeneous cosmological models with a pure radiation field as matter content. It is shown that the conditions for regularity are very easy to implement and therefore there is a huge number of such spacetimes.Comment: 13 pages, LaTex, ws-mpla, to appear in Modern Physics Letters

Arqueología: imagen y proyección social

Sin resume