El procés més important de la terra

El mecanisme que fa que els vegetals i alguns bacteris elaborin matèria orgànica determina l'existència de la vida en el nostre planet

Gravitational radiation from nonaxisymmetric spherical Couette flow in a neutron star

The gravitational wave signal generated by global, nonaxisymmetric shear flows in a neutron star is calculated numerically by integrating the incompressible Navier--Stokes equation in a spherical, differentially rotating shell. At Reynolds numbers \Rey \gsim 3 \times 10^{3}, the laminar Stokes flow is unstable and helical, oscillating Taylor--G\"ortler vortices develop. The gravitational wave strain generated by the resulting kinetic-energy fluctuations is computed in both $+$ and $\times$ polarizations as a function of time. It is found that the signal-to-noise ratio for a coherent, $10^{8}$-{\rm s} integration with LIGO II scales as $6.5 (\Omega_*/10^{4} {\rm rad} {\rm s}^{-1})^{7/2}$ for a star at 1 {\rm kpc} with angular velocity $\Omega_*$. This should be regarded as a lower limit: it excludes pressure fluctuations, herringbone flows, Stuart vortices, and fully developed turbulence (for \Rey \gsim 10^{6}).Comment: (1) School of Physics, University of Melbourne, Parkville, VIC 3010, Australia. (2) Departamento de Fisica, Escuela de Ciencias,Universidad de Oriente, Cumana, Venezuela, (3) Department of Mechanical Engineering, University of Melbourne, Parkville, VIC 3010, Australia. Accepted for publication in The Astrophysical Journal Letter

Gravitational radiation from pulsar glitches

The nonaxisymmetric Ekman flow excited inside a neutron star following a rotational glitch is calculated analytically including stratification and compressibility. For the largest glitches, the gravitational wave strain produced by the hydrodynamic mass quadrupole moment approaches the sensitivity range of advanced long-baseline interferometers. It is shown that the viscosity, compressibility, and orientation of the star can be inferred in principle from the width and amplitude ratios of the Fourier peaks (at the spin frequency and its first harmonic) observed in the gravitational wave spectrum in the plus and cross polarizations. These transport coefficients constrain the equation of state of bulk nuclear matter, because they depend sensitively on the degree of superfluidity.Comment: 28 page

Bibliometric analysis about university social responsibility

Se presenta un estudio descriptivo cuyo objetivo general fue conocer la producción científica sobre “Responsabilidad Social Universitaria” (RSU). Se realizó un análisis bibliométrico de 94 documentos obtenidos a través de las bases de datos Redalyc, Scielo y a través de la Biblioteca Electrónica de Ciencia y Tecnología del Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina). Los resultados mostraron que RSU es un campo de estudio reciente que comienza a tener visibilidad en las bases consideradas, el número de publicaciones ha aumentado a partir del año 2007. Venezuela, México, Colombia y Chile son los países que más documentos publicados acumulan. Cinco revistas se presentan como las más productivas. El 90% de los documentos analizados están firmados por un solo autor. No se han encontrado estudios bibliométricos previos en este tema.A descriptive study is presented which goal was to know about University Social Responsibility’s scientific production. A bibliometric analysis of 94 documents obtained from Redalyc and Scielo data bases and from Science and Technology Electronic Library from Science, Technology and Productive Innovation Ministry (Argentina) was carried out. Results showed that University Social Responsibility is a recently study area with newly visibility in considered bases, the number of publications has grown since 2007. Venezuela, Mexico, Colombia and Chile are the countries which present more published documents in the area. Five journals are the most productive. The 90% of the analyzed documents are signed by only one author. Bibliometric studies about this topic were not found.Fil: Pacenza, Maria Ines. Universidad Nacional de Mar del Plata. Facultad de Psicología; ArgentinaFil: Silva Peralta, Yamila Fernanda. Universidad Nacional de Mar del Plata. Facultad de Psicología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata; Argentin

Association of C2, a derivative of the radial artery pressure waveform, with new onset of type 2 diabetes mellitus: the MESA study.

BackgroundAlthough microvascular dysfunction is known to result from diabetes, it might also lead to diabetes. Lower values of C2, a derivative of the radial artery pressure waveform, indicate microvascular dysfunction and predict hypertension and cardiovascular disease (CVD). We studied the association of C2 with incident diabetes in subjects free of overt CVD.MethodsAmong multi-ethnic participants (n = 5214), aged 45-84 years with no diabetes, C2 was derived from the radial artery pressure waveform. Incident diabetes (N = 651) was diagnosed as new fasting glucose ≥ 126 mg/dL or antidiabetic medicine over ~ 10 years. The relative incidence density (RID) for incident diabetes per standard deviation (SD) of C2 was studied during ~ 10 years follow-up using four levels of adjustment.ResultsMean C2 at baseline was 4.58 ± 2.85 mL/mmHg × 100. The RID for incident diabetes per SD of C2 was 0.90 (95% CI 0.82-0.99, P = 0.03). After adjustment for demographics plus body size, the corresponding RID was 0.81 (95% CI 0.73-0.89, P < 0.0001); body mass index (BMI) was the dominant covariate here. After adjustment for demographics plus cardiovascular risk factors, the RID was 0.98 (95% CI 0.89, 1.07, P = 0.63). After adjustment for all the parameters in the previous models, the RID was 0.87 (95% CI 0.78, 0.96, P = 0.006).ConclusionsIn a multi-ethnic sample free of overt CVD and diabetes at baseline, C2 predicted incident diabetes after adjustment for demographics, BMI and CVD risk factors. Differences in arterial blood pressure wave morphology may indicate a long-term risk trajectory for diabetes, independently of body size and the classical risk factors

I-V curves of Fe/MgO (001) single- and double-barrier tunnel junctions

In this work, we calculate with ab initio methods the current-voltage characteristics for ideal single- and double-barrier Fe/MgO (001) magnetic tunnel junctions. The current is calculated in the phase-coherent limit by using the recently developed SMEAGOL code, combining the nonequilibrium Green function formalism with density-functional theory. In general we find that double-barrier junctions display a larger magnetoresistance, which decays with bias at a slower pace than their single-barrier counterparts. This is explained in terms of enhanced spin filtering from the middle Fe layer sandwiched in between the two MgO barriers. In addition, for double-barrier tunnel junctions, we find a well defined peak in the magnetoresistance at a voltage of V=0.1 V. This is the signature of resonant tunneling across a majority quantum well state. Our findings are discussed in relation to recent experiments

Establecimientos colaboradores, una herramienta para el aprendizaje y el uso del catalán

En aquest article s'explica l'experiència que ha permès al Centre de Normalització Lingüística L'Heura arribar a les 1.342 pràctiques lingüístiques durant els anys acadèmics 2010-2013, utilitzant la xarxa dels establiments col·laboradors (EC) de Santa Coloma de Gramenet. Per entendre com s'ha assolit aquesta xifra, el procés es presenta dividit en tres etapes: el naixement dels EC (2003-2006), la consolidació de la xarxa d'EC i la posada en marxa del carnet de les pràctiques lingüístiques (2007-2010) i l'extensió d'aquestes pràctiques a l'alumnat (2010-). En la darrera part de l'article, s'analitzen les pràctiques des d'un punt de vista quantitatiu i qualitatiu a partir del carnet i de les fitxes d'avaluació dels alumnes participants.The article explains the experience which has enabled the Heura Centre for Language Standardisation to reach the figure of 1,342 language practice sessions during the 2010-2013 academic years, using the network of collaborating establishments (ECs) in Santa Coloma de Gramenet. To understand how they have achieved this number, the process has been broken down and presented in three stages: birth of the ECs (2003-2006), consolidation of the EC network and introduction of the language practice card (2007-2010), and the extension of these practice sessions throughout the student body (2010-). The last section of the article analyses such practice from a quantitative and qualitative perspective, based on the practice card and participating students’ assessment files.En este artículo se explica la experiencia que ha permitido al Centro de Normalización Lingüística L’Heura llegar a las 1.342 prácticas lingüísticas en los años académicos 2010-2013, utilizando la red de los establecimientos colaboradores (EC) de Santa Coloma de Gramenet. Para comprender cómo se ha alcanzado esa cifra, el proceso se presenta dividido en tres etapas: el nacimiento de los EC (2003-2006), la consolidación de la red de EC y la puesta en marcha del carné de las prácticas lingüísticas (2007-2010), y la extensión de dichas prácticas al alumnado (2010-). En la última parte del artículo, se analizan las prácticas desde un punto de vista cuantitativo y cualitativo a partir del carné y de las fichas de evaluación de los alumnos participantes