Magnetohydrodynamic equilibria in barotropic stars

Although barotropic matter does not constitute a realistic model for magnetic stars, it would be interesting to confirm a recent conjecture that states that magnetized stars with a barotropic equation of state would be dynamically unstable (Reisenegger 2009). In this work we construct a set of barotropic equilibria, which can eventually be tested using a stability criterion. A general description of the ideal MHD equations governing these equilibria is summarized, allowing for both poloidal and toroidal magnetic field components. A new finite-difference numerical code is developed in order to solve the so-called Grad-Shafranov equation describing the equilibrium of these configurations, and some properties of the equilibria obtained are briefly discussed.Comment: Conference Proceedings, Magnetic Fields in the Universe IV (2013

Oxidized Forms of Antiaromatic Oligomers of Biphenylene

Rsumen de la comunicaciónThe importance of antiaromatic molecules in Chemistry and more recently in material science is rising. In the particular case of applications in electronics, the antiaromatic skeleton offers the favorable situation of high energy (i.e., destabilized) occupied molecular orbitals allowing to ease oxidation, doping or electron transfer to form conductive and photo-active substrates.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

Charge Transfer mechanism in the Surface Enhanced Raman Scattering of 2,2'-bipyridine recorded on a silver electrode

Nowadays, Surface Enhanced Raman Spectroscopy (SERS) has become a powerful technique to investigate the electronic structure of surface-molecule hybrid systems due to the huge enhancement of the Raman signal. It is established that the origin of this enhancement has two main contributions; the electromagnetic (EM), related to surface plasmons, and the chemical mechanism, due to resonant charge transfer (CT) processes between the adsorbate and the metal. With the aim to investigate the SERS-CT of bipyridine and to identify charge transfer process, the spectra were recorded on silver electrode by using three different wavelengths (473, 532 and 785 nm) in a range from 0.0 up to -1.4 V electrode potential. The electrode potential was modelled in the calculations with atomic silver wires of different size and charge attached to the BPy molecule (AgnBPyq, with q = 0 for n = 2 and q = ±1 for n = 3, 5, 7) and were computed with Density Functional Theory (DFT). Although BPy shows a trans conformation in solution, a cis conformation was chosen for its chelating properties. The results indicate that the intensification of the ~1550 cm-1 band at negative potentials is due the Franck-Condon factors related to the resonant CT process from the metal to the BPy molecule.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Early Cretaceous absolute geomagnetic paleointensities from Córdoba province (Argentina)

We present here new paleointensity and geochronology results from Early Cretaceous volcanic rocks of Sierra Chica de Cordoba (Argentina). The new K-Ar isotopic ages of 5 samples range from 136 to 122 Ma. Twenty five samples from 7 individual flows yielded acceptable paleointensity estimates. The mean paleointensity values per flow are ranging from 53.0±1.9 to 25.4±2.6 μT and the corresponding Virtual Dipole Moments (VDMs) are ranging from 9.3±1.3 to 4.6±0.5 (1022 Am2). This corresponds to the mean value of 7.3±1.7x1022 Am2, which is compatible to the present geomagnetic axial dipole. Currently available selected paleointensity data from 80 to 130 Ma suggest that geomagnetic field strength frequently fluctuated before and during the Cretaceous Normal Superchron while the magnetic polarity maintained stable. The mean paleointensities derived from Cordoba lavas agree remarkably well with those obtained from the Parana Magmatic Province (133-132 Ma). This reinforces the hypothesis about the unreliability of ‘Mesozoic Dipole Low'.Fil: Cejudo Ruiz, Ruben. Universidad Nacional Autónoma de México; MéxicoFil: Goguitchaichvili, Avto. Universidad Nacional Autónoma de México; MéxicoFil: Geuna, Silvana Evangelina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; ArgentinaFil: Alva-Valdivia, Luis M.. Universidad Nacional Autónoma de México; MéxicoFil: Solé, Jesus. Universidad Nacional Autónoma de México; MéxicoFil: Morales, Juan. Universidad Nacional Autónoma de México; Méxic

Multi-Fluid Simulation of the Magnetic Field Evolution in Neutron Stars

Using a numerical simulation, we study the effects of ambipolar diffusion and ohmic diffusion on the magnetic field evolution in the interior of an isolated neutron star. We are interested in the behavior of the magnetic field on a long time scale, over which all Alfven and sound waves have been damped. We model the stellar interior as an electrically neutral plasma composed of neutrons, protons and electrons, which can interact with each other through collisions and electromagnetic forces. Weak interactions convert neutrons and charged particles into each other, erasing chemical imbalances. As a first step, we assume that the magnetic field points in one fixed Cartesian direction but can vary along an orthogonal direction. We start with a uniform-density background threaded by a homogeneous magnetic field and study the evolution of a magnetic perturbation as well as the density fluctuations it induces in the particles. We show that the system evolves through different quasi-equilibrium states and estimate the characteristic time scales on which these quasi-equilibria occur.Comment: It will be published in AIP Proceedings of the Conference '40 Years of Pulsars: Milisecond Pulsars, Magnetars and More' held at University of McGill, Montreal, Canada, August 2007. Contributed Talk at Conference '40 Years of Pulsars: Milisecond Pulsars, Magnetars and More

Investigación, políticas y desarrollo en el Perú

Este capítulo se presenta en cuatro secciones. La primera presenta una breve revisión acerca de la evolución de la salud materno-infantil y del acceso a los servicios de salud durante la última década, la misma que busca ir más allá de los simples promedios, para identificar aquellos grupos que se han visto menos beneficiados con las tendencias positivas encontradas en la mayoría de indicadores tradicionales. A continuación, la segunda sección aborda dos temas fundamentales: la problemática para establecer la importancia de la causalidad entre una determinada variable socioeconómica —como educación, ingreso familiar, etnicidad y género, entre otras— y la salud de los niños y sus madres; y la importancia de las características de las familias y las redes sociales como determinantes de las desigualdades en salud. La tercera sección plantea dos líneas de acción orientadas a fortalecer nuestra capacidad de profundizar el conocimiento acerca de la conexión entre los antecedentes familiares, la acción pública y las desigualdades en salud materno-infantil en el Perú: la primera se centra en mejoras en la información —tanto a nivel de encuestas de hogares como de registros administrativos—, que nos permitan un mejor entendimiento del papel de las redes familiares y sociales como determinantes de la salud materno-infantil; y la segunda línea plantea la necesidad de que las innovaciones necesarias para reducir las desigualdades en salud se diseñen e implementen considerando una estrategia sólida de evaluación que permita aprender de manera sistemática acerca de lo que mejor funciona en diferentes contextos para atender a los sectores más vulnerables. El texto cierra con un resumen de los principales planteamientos del documento, poniendo énfasis en la necesidad de incorporar las líneas de acción propuestas a una agenda que permita promover el desarrollo de políticas basadas en evidencia empírica sólida.Maternal and child health, Peru