Evolution of magnetic fields through cosmological perturbation theory

The origin of galactic and extra-galactic magnetic fields is an unsolved problem in modern cosmology. A possible scenario comes from the idea of these fields emerged from a small field, a seed, which was produced in the early universe (phase transitions, inflation, ...) and it evolves in time. Cosmological perturbation theory offers a natural way to study the evolution of primordial magnetic fields. The dynamics for this field in the cosmological context is described by a cosmic dynamo like equation, through the dynamo term. In this paper we get the perturbed Maxwell's equations and compute the energy momentum tensor to second order in perturbation theory in terms of gauge invariant quantities. Two possible scenarios are discussed, first we consider a FLRW background without magnetic field and we study the perturbation theory introducing the magnetic field as a perturbation. The second scenario, we consider a magnetized FLRW and build up the perturbation theory from this background. We compare the cosmological dynamo like equation in both scenarios

Geodesic Deviation Equation in Bianchi Cosmologies

We present the Geodesic Deviation Equation (GDE) for the Friedmann-Robertson-Walker(FRW) universe and we compare it with the equation for Bianchi type I model. We justify consider this cosmological model due to the recent importance the Bianchi Models have as alternative models in cosmology. The main property of these models, solutions of Einstein Field Equations (EFE) is that they are homogeneous as the FRW model but they are not isotropic. We can see this because they have a non-null Weyl tensor in the GDE.Comment: Submitted to Journal of Physics: Conference Series (JPCS), ERE200

El crecimiento de las exportaciones menores y el sistema de fomento de las exportaciones en Colombia

En este estudio se hará un intento de explicar el crecimiento de las exportaciones menores durante los últimos veinte años a la luz de las políticas colombianas de fomento de las exportaciones. El esfuerzo de fomento de las exportaciones menores se inició a base de aproximaciones sucesivas en las cuales varió con frecuencia la definición de las exportaciones menores y las políticas algunas veces cambiaron de un año a otro

Noncommutative Geometry Inspired Rotating Black Hole in Three Dimensions

We find a new rotating black hole in three-dimensional anti-de Sitter space using an anisotropic perfect fluid inspired by the noncommutative black hole. We deduce the thermodynamical quantities of this black hole and compare them with those of a rotating BTZ solution.Comment: 7 page

Boundary Term in Metric f(R) Gravity: Field Equations in the Metric Formalism

The main goal of this paper is to get in a straightforward form the field equations in metric f(R) gravity, using elementary variational principles and adding a boundary term in the action, instead of the usual treatment in an equivalent scalar-tensor approach. We start with a brief review of the Einstein-Hilbert action, together with the Gibbons-York-Hawking boundary term, which is mentioned in some literature, but is generally missing. Next we present in detail the field equations in metric f(R) gravity, including the discussion about boundaries, and we compare with the Gibbons-York-Hawking term in General Relativity. We notice that this boundary term is necessary in order to have a well defined extremal action principle under metric variation.Comment: 12 pages, title changes by referee recommendation. Accepted for publication in General Relativity and Gravitation. Matches with the accepted versio

Prevalencia de bacteriuria asintomática en embarazadas de 12 a 16 semana de gestación

ResumenAntecedentes: La bacteriuria asistomática (BA) se presenta entre el 4-7% del total de embarazos; se puede tener como concecuencia el desarrollo de pielonefritis, que puede conducir a parto pretérmino y bajo peso al nacer.[Maldonado HF, Antolinez LY, Solano MNC, Tejeiro ML, Valbuena AR. Prevalencia de bacteriuria asintomática en embarazadas de 12 a 16 semana de gestación. MedUNAB 2005;8:78-81].Palabras clave: Bacteriuria asistomática, Urocultivo, Pielonefritis, Edad gestacional, Embarzo, Control prenata

The conceptualisation and measurement of DSM-5 Internet Gaming Disorder: the development of the IGD-20 Test

Background: Over the last decade, there has been growing concern about ‘gaming addiction’ and its widely documented detrimental impacts on a minority of individuals that play excessively. The latest (fifth) edition of the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders (DSM-5) included nine criteria for the potential diagnosis of Internet Gaming Disorder (IGD) and noted that it was a condition that warranted further empirical study. Aim: The main aim of this study was to develop a valid and reliable standardised psychometrically robust tool in addition to providing empirically supported cut-off points. Methods: A sample of 1003 gamers (85.2% males; mean age 26 years) from 57 different countries were recruited via online gaming forums. Validity was assessed by confirmatory factor analysis (CFA), criterion-related validity, and concurrent validity. Latent profile analysis was also carried to distinguish disordered gamers from non-disordered gamers. Sensitivity and specificity analyses were performed to determine an empirical cut-off for the test. Results: The CFA confirmed the viability of IGD-20 Test with a six-factor structure (salience, mood modification, tolerance, withdrawal, conflict and relapse) for the assessment of IGD according to the nine criteria from DSM-5. The IGD-20 Test proved to be valid and reliable. According to the latent profile analysis, 5.3% of the total participants were classed as disordered gamers. Additionally, an optimal empirical cut-off of 71 points (out of 100) seemed to be adequate according to the sensitivity and specificity analyses carried

Enfermedad ateroembólica. Presentación de un caso de afectación multisistémica y revisión de la literatura

The atheroembolic disease is an entity characterized by obstruction of multiple small arteries by cholesterol crystals. The incidence rises steeply with advancing age and following an invasive procedure involving arteries in patients with atherosclerosis. Actually it has a growing interest due to the increased frequency and to the lack of appropriate therapy. In this paper we report a clinical case of multiple system disease secondary to anticoagulant therapy in a 69 years old patient. We review the pathogenesis, clinical features, laboratory dates and pathology of the diseas