Fast temporal correlation between hard X-ray and ultraviolet continuum brightenings

Recent Solar Maximum Mission (SMM) observations have shown fast and simultaneous increases in hard X-rays (HXR, E25 keV) and ultraviolet continuum (UVC, lambda lambda approx. equals 1600 and 1388 A) radiation. A simple and natural explanation is given for this phenomenon to happen, which does not involve extreme conditions for energy transport processes, and confirms earlier results on the effect of XUV photoionization in the solar atmosphere

Limit theorems for a general stochastic rumour model

We study a general stochastic rumour model in which an ignorant individual has a certain probability of becoming a stifler immediately upon hearing the rumour. We refer to this special kind of stifler as an uninterested individual. Our model also includes distinct rates for meetings between two spreaders in which both become stiflers or only one does, so that particular cases are the classical Daley-Kendall and Maki-Thompson models. We prove a Law of Large Numbers and a Central Limit Theorem for the proportions of those who ultimately remain ignorant and those who have heard the rumour but become uninterested in it.Comment: 13 pages, to appear in SIAM Journal on Applied Mathematic

Non-radial pulsations in the Be/X binaries 4U0115+63 and SAXJ2103.5+4545

The discovery of non-radial pulsations (NRP) in the Be/X binaries of the Magellanic Clouds (MC, eg. Fabrycky 2005, Coe et al. 2005, Schmidtke & Cowley 2005) provided a new approach to understand these complex systems, and, at the same time, favoured the synergy between two different fields: stellar pulsations and X-ray binaries. This breakthrough was possible thanks to the MACHO and OGLE surveys. However, in our Galaxy, only two Be/X have been reported to show NRP: GROJ2058+42 (Kiziloglu et al. 2007) and LSI+61 235 (Sarty et al. 2009). Our objective is to study the short-term variability of Galactic Be/X binaries, compare them to the Be/X of the MC and to the isolated Galactic Be observed with CoRoT and Kepler. We present preliminary results of two Be/X stars, namely 4U0115+63 and SAXJ2103.5+4545 showing multiperiodicity and periodicity respectively, most probably produced by non-radial pulsations.Comment: 2 pages, 2 figures, IAUS 272 "Active OB stars: structure, evolution, mass loss and critical limits" conference, Paris, July 2010, submitte

Estabilidad Dinámica Lateral De Vigas De Pared Delgada Considerando Efectos Geométricos No Lineales.

En este trabajo se presenta el análisis de la inestabilidad dinámica lateral de vigas de pared delgada doblemente simétricas. Como aspecto distintivo se considera el efecto de la predeformación estática en el plano de carga, que tiene una importancia crucial en el caso estático, como ha sido recientemente mostrado por los autores, Machado y Cortínez (2005). El análisis se basa en un modelo geométricamente no lineal que es adecuadamente linealizado manteniendo el acoplamiento entre la predeformación estática en el plano de carga con el movimiento lateral-torsional correspondiente al movimiento inestable. Mediante una solución numérica se obtienen las regiones paramétricas de inestabilidad y se discute la importancia del nuevo efecto considerado mediante la comparación con los resultados provenientes del análisis clásico.Fil: Machado, Sebastián Pablo. Universidad Tecnológica Nacional. Facultad Regional Bahía Blanca; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Cortínez, Víctor Hugo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Tecnológica Nacional. Facultad Regional Bahía Blanca; Argentin

Editorial: Grazing behavior and welfare of ruminants

The domestication and use of animals for our benefit entails responsibility for their quality of life (1). Animal welfare is a prerequisite for any ethical and sustainable animal production system to be socially defensible and acceptable (2). In nature, animals evolved in a changing environment and developed adaptive mechanisms to increase fitness (3). Cattle evolved in extensive grasslands and rangelands, in herds and families with complex social hierarchy and adapt to challenges posed by their environment through natural selection. Grazing animals face a number of challenges, including tick-borne diseases and lack of access to water and shade. Under human control, it is our responsibility to help animals to cope with such stressors and provide them a good life. This Research Topic aims to identify stressors present in pastoral husbandry systems; assess to the extent they affect health, welfare and production, and propose solutions to mitigate or overcome stressors

The shear deformation effect on the nonlinear dynamic of a simple rotor blade

The nonlinear planar response of a cantilever rotating slender beam to a principal parametric resonance of its first bending mode is analyzed considering the effect of shear deformation. The equation of motion is obtained in the form of an integro-partial differential equation, taking into account mid-plane stretching, a rotation speed and modal damping. A composite linear elastic material is considered and the cross-section properties are assumed to be constant given the assumption of small strains. The beam is subjected to a harmonic transverse load in the presence of internal resonance. The internal resonance can be activated for a range of the beam rotating speed, where the second natural frequency is approximately three times the first natural frequency. The method of multiple scales method is used to derive four-first ordinary differential equations that govern the evolution of the amplitude and phase of the response. These equations are used to determine the steady state responses and their stability. Nonlinear normal modes are obtained for the two models, considering and neglecting the effect of shear deformation. The results of the analysis show that the equilibrium solutions are influenced by the transverse shear effect. When this effect is ignored the amplitude of vibration is reduced significantly, thus altering the dynamic response of the beam. This alteration can lead to an incorrect stability prediction of the periodic solutions.Fil: Machado, Sebastián Pablo. Universidad Tecnológica Nacional. Facultad Regional Bahía Blanca. Grupo de Análisis de Sistemas Mecánicos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Saravia, César Martín. Universidad Tecnológica Nacional. Facultad Regional Bahía Blanca. Grupo de Análisis de Sistemas Mecánicos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Recomendaciones de carácter ambiental para fortalecer algunos sectores de la comunidad frente a la introducción de transnacionales mineras, caso de estudio : Quinchía, Risaralda 2005-2014

Este trabajo de grado está constituido por tres capítulos, que contextualizan las recomendaciones de carácter ambiental para fortalecer algunos sectores de la comunidad urbana, comercial y mineros tradicionales de Irra, Miraflores y CORPOARE por la introducción de transnacionales mineras caso de estudio: Quinchía, Risaralda entre los años 2005-2013. Inicialmente se establecieron algunos aspectos socioeconómicos afectados por la fase de exploración de las transnacionales mineras en el municipio. Para realizar la caracterización socioeconómica se realizaron 178 encuestas en los tres sectores anteriormente mencionados, la información fue tomada del proyecto de extensión del semillero de Economía Ambiental y de los Recursos Naturales al cual pertenecen los autores. Estas encuestas permitieron un acercamiento a la realidad de los mineros tradicionales, además permitió establecer las variables socioeconómicas en el casco urbano del municipio de Quinchía. En el segundo capítulo se evaluó los impactos ambientales más significativos de la exploración de transnacionales mineras en los aspectos biofísicos para determinar la incidencia de los mismos en la dinámica territorial del municipio de Quinchía y por tanto en comunidades que históricamente han realizado dicha actividad como medio de ingresos económicos. Además se propone elaborar diferentes recomendaciones de carácter ambiental para fortalecer a la comunidad que de una u otra forma ha sido afectada por la ejecución de proyectos mineros en este municipio en los últimos 10 años. Además se analizaron los impactos ambientales negativos más significativos asociados a la llegada de las transnacionales mineras, a fin de establecer ciertas recomendaciones generales que contribuyan a mejorar la gestión ambiental y por ende disminuir los efectos generados a la comunidad

A consistent total Lagrangian finite element for composite closed section thin walled beams

This work presents a consistent geometrically exact finite element formulation of the thin-walled anisotropic beam theory. The present formulation is thought to address problems of composite beams with nonlinear behavior. The constitutive formulation is based on the relations of composite laminates and thus the cross sectional stiffness matrix is obtained analytically. The variational formulation is written in terms of generalized strains, which are parametrized with the director field and its derivatives. The generalized strains and generalized beam forces are obtained by introducing a transformation that maps generalized components into physical components. A consistent tangent stiffness matrix is obtained by parametrizing the finite rotations with the total rotation vector; its derivation is greatly simplified by obtention of the derivatives of the director field via interpolation of nodal triads. Several numerical examples are presented to show the accuracy of the formulation and also its frame invariance and path independence.Fil: Saravia, César Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina. Universidad Tecnológica Nacional. Facultad Regional Bahía Blanca; ArgentinaFil: Machado, Sebastián Pablo. Universidad Tecnológica Nacional. Facultad Regional Bahía Blanca. Grupo de Investigación en Multifísica Aplicada. - Comisión de Investigaciones Científicas de la Provincia de Buenos Aires. Grupo de Investigación en Multifísica Aplicada; ArgentinaFil: Cortínez, Víctor Hugo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina. Universidad Tecnológica Nacional. Facultad Regional Bahía Blanca; Argentin