THE EFFECT OF SOLIDIFICATION RATE AND SOLUTIONIZING QUENCH RATE ON THE MECHANICAL PROPERTIES AND HARDENING RESPONSE OF ALUMINUM ALLOYS: A QUANTITATIVE COMPARISON

A comparative study of five aluminum alloys was performed to characterize the effect of solidification rate and quench rate on casting microstructure and properties. The alloys were cast in the geometry for Jominy End Quench (JEQ) testing, so as to take advantage of the JEQ test’s ability to give data on multiple quench rates in a single sample and illustrate the quench sensitivity of an alloy. While the Jominy End Quench test has been used in aluminum alloys, the effects of solidification rates have not been assessed in depth. The work done by other studies has either focused on a single alloy across multiple solidification rates, or on multiple alloys using a single solidification rate. To this end, three molds were created: a sand mold, a semi-permanent mold and a permanent mold, with the intent of casting JEQ bars out of multiple aluminum alloys for direct comparison. The tensile strength, hardness, porosity, and electrical conductivity were assessed, in an attempt to compare the quench sensitivities of the samples. This study will provide a starting point for more in-depth analyses of the alloys, i.e. the kinetics of precipitation strengthening over a range of length scales (cooling rates)

Confidence in the Beef Production System as a Key Factor to Mitigate the Impact of BSE on Beef Consumption

Recent food scares in the food market has caused a reduction in consumer's confidence in the food system that it has induced a significant reduction in consumption in a sector, the beef sector that was already characterized by a saturated trend in quantity terms. In this context, all participants in the beef production system are facing to a great challenge, to retrieve consumer's confidence in the food chain and to mitigate the reduction in beef consumption. The aim of the paper is to analyse the impact of consumer's confidence in the food system as well as other factors on the explanation of food consumption reduction. A structural modelling approach has been used to analyse factors affecting the reduction in beef consumption in two different regions characterised by different production systems and different marketing strategies (PGI beef label). Results indicate that main factor explaining the reduction in beef consumption is the confidence in the beef and a positive relation has been found. Moreover, confidence in a product is directly related to the perceived quality offered by farmers and other decision makers on the beef chain, and to the consumer involvement with the product. Therefore, the main implication is that participants in the food chain has to develop adequate communication strategies such as quality labelling in order to increase consumers perceive quality because, higher quality perception will recover consumers' confidence in beef, and therefore, it will mitigate beef consumption reduction.food confidence, consumer behaviour, structural equation modelling, beef sector, quality label, Food Consumption/Nutrition/Food Safety,

Gravitational Waves from Abelian Gauge Fields and Cosmic Strings at Preheating

Primordial gravitational waves provide a very important stochastic background that could be detected soon with interferometric gravitational wave antennas or indirectly via the induced patterns in the polarization anisotropies of the cosmic microwave background. The detection of these waves will open a new window into the early Universe, and therefore it is important to characterize in detail all possible sources of primordial gravitational waves. In this paper we develop theoretical and numerical methods to study the production of gravitational waves from out-of-equilibrium gauge fields at preheating. We then consider models of preheating after hybrid inflation, where the symmetry breaking field is charged under a local U(1) symmetry. We analyze in detail the dynamics of the system in both momentum and configuration space, and show that gauge fields leave specific imprints in the resulting gravitational wave spectra, mainly through the appearence of new peaks at characteristic frequencies that are related to the mass scales in the problem. We also show how these new features in the spectra correlate with string-like spatial configurations in both the Higgs and gauge fields that arise due to the appearance of topological winding numbers of the Higgs around Nielsen-Olesen strings. We study in detail the time evolution of the spectrum of gauge fields and gravitational waves as these strings evolve and decay before entering a turbulent regime where the gravitational wave energy density saturates.Comment: This paper is dedicated to the memory of Lev Kofman. Added references and comments in Sec. III.B. Version accepted in PR

A Gravitational Wave Background from Reheating after Hybrid Inflation

The reheating of the universe after hybrid inflation proceeds through the nucleation and subsequent collision of large concentrations of energy density in the form of bubble-like structures moving at relativistic speeds. This generates a significant fraction of energy in the form of a stochastic background of gravitational waves, whose time evolution is determined by the successive stages of reheating: First, tachyonic preheating makes the amplitude of gravity waves grow exponentially fast. Second, bubble collisions add a new burst of gravitational radiation. Third, turbulent motions finally sets the end of gravitational waves production. From then on, these waves propagate unimpeded to us. We find that the fraction of energy density today in these primordial gravitational waves could be significant for GUT-scale models of inflation, although well beyond the frequency range sensitivity of gravitational wave observatories like LIGO, LISA or BBO. However, low-scale models could still produce a detectable signal at frequencies accessible to BBO or DECIGO. For comparison, we have also computed the analogous gravitational wave background from some chaotic inflation models and obtained results similar to those found by other groups. The discovery of such a background would open a new observational window into the very early universe, where the details of the process of reheating, i.e. the Big Bang, could be explored. Moreover, it could also serve in the future as a new experimental tool for testing the Inflationary Paradigm.Comment: 22 pages, 18 figures, uses revtex

Estimación de economías de aglomeración en el Perú: sector formal y sector informal

En el presente documento se estima la contribución de las economías de aglomeración en la productividad de las ciudades y su aporte en el sector formal e informal. Asimismo, se evalúa cuál de estos dos sectores es el más beneficiado. La metodología aplicada para calcular la contribución involucra una regresión en dos etapas. En la primera etapa, se estima la productividad por ciudades; y, en la segunda, la elasticidad de la productividad respecto al tamaño de la población. Los resultados reportan que las economías de aglomeración contribuyen a la productividad en 0,0396, es decir, duplicar el tamaño de una ciudad está asociado con un incremento aproximado del salario promedio de 4%. Cabe resaltar que el sector informal es el más beneficiado con una elasticidad de 0,0453; mientras que, el sector formal presenta una elasticidad estimada no significativa (0,0085)

Los estudiantes de las Ciencias Médicas, futuros guardianes de batas blancas

Medical science students: future guardians of white coats Los estudiantes de las Ciencias Médicas, futuros guardianes de batas blanca

Consejo y prevención a pacientes mayores en hospitales y residencias geriátricas en España

ResumenObjetivosConocer el perfil sociosanitario de los pacientes mayores atendidos en consultas; conocer las acciones preventivas que se llevan a cabo, de forma rutinaria, en hospitales, residencias geriátricas y otros centros asistenciales en España.DiseñoEstudio descriptivo transversal, basado en un cuestionario a médicos que atienden a población mayor de 65años en España (2013).EmplazamientoCentros de diferentes comunidades autónomas en España.Participantes: Un total de 420 médicos de hospitales, residencias y otros centros. Se obtuvieron datos de 840 consultas a pacientes geriátricos.Mediciones principalesVariables principales de resultados: dependencia, comorbilidad, motivo de consulta, actuación en consulta y recomendación de estilos de vida saludable. Factor asociado, tipo de institución en la que se atendió al paciente. Análisis de prevalencias y diferencias con Chi-cuadrado.ResultadosEl 66,7% presentaban dependencia, siendo mayor entre las mujeres: 68,9% vs 62,4% (p=0,055). El 88,6% de mujeres atendidas con 85 o más años presentaban comorbilidad, mientras que en hombres de ese mismo grupo de edad eran un 79,8%. Solo un 6,6% de pacientes con comorbilidad recibieron recomendaciones saludables durante la consulta. El 79,6% de pacientes atendidos en hospitales recibieron recomendaciones de estilo de vida saludable, mientras que en las residencias geriátricas las recibieron el 59,62% de los pacientes (p<0,001).ConclusionesSe detecta una escasa acción preventiva y de promoción de la salud hacia las personas mayores, con diferencias entre hospitales y residencias geriátricas. Parece necesario incentivar la actitud promotora de salud y las intervenciones preventivas en la práctica clínica gerontológica.AbstractObjectiveTo establish the profile of elderly patients, and to assess current preventive actions in hospitals, geriatric residences, and different health-care centres in Spain.DesignCross-sectional descriptive study, based on a questionnaire to be answered by doctors who treat the elderly population in Spain (2013).SettingHealth-care centres from different regions of Spain.ParticipantsA total of 420 practitioners from hospitals, residences and other community centres, with data from 840 geriatric clinics.Main measurementsMain outcome variables are: dependence, reason for assistance, comorbidity, professional consultation, and life style recommendations. Association factor, type of institution where patients have been attended. Analysis of prevalence and association using Chi-squared test.OutcomesTwo-thirds (66.7%) of the study population were shown to be dependent, with a higher percentage among women than men: 68.9% vs. 62.4% (P=.055). It was also found that among the population aged 85 or more, 88.6% of the women and 85.2% of the men suffered comorbidity. In spite of these results, only 6.6% of the patients suffering comorbidity received additional advice concerning healthy-lifestyle. A large majority (79.6%) of the patients treated in hospitals received advice concerning healthy lifestyle, while 59.62% of those treated in nursing homes received it (P<.001).ConclusionsIt was observed that there is a lack of preventive action related to health promotion among the elderly, with differences between hospitals and geriatric residences. This suggests that it is time to put forward new specialised programs addressed to health professionals, in order to reinforce health promotion attitudes and preventive interventions in gerontology clinical practice

Reduction of Courant algebroids and generalized complex structures

We present a theory of reduction for Courant algebroids as well as Dirac structures, generalized complex, and generalized K\"ahler structures which interpolates between holomorphic reduction of complex manifolds and symplectic reduction. The enhanced symmetry group of a Courant algebroid leads us to define \emph{extended} actions and a generalized notion of moment map. Key examples of generalized K\"ahler reduced spaces include new explicit bi-Hermitian metrics on \CC P^2.Comment: 34 pages. Presentation greatly improved, one subsection added, errors corrected, references added. v3: a few changes in the presentation, material slightly reorganized, final version to appear in Adv. in Mat

Jump capacity in cerebral palsy soccer players

Los objetivos del presente estudio fueron determinar en jugadores de fútbol con parálisis cerebral la altura de vuelo durante la realización del salto sin contramovimiento y con contramovimiento, y observar la relación de las variables antropométricas y de la clase funcional con la altura de vuelo y con el índice elástico. Trece jugadores de fútbol 7 diagnosticados con parálisis cerebral participaron en el estudio. La altura de vuelo durante el salto sin contramovimiento (20.45±4.45 cm) y con contramovimiento (24.33±5.37 cm) fue inferior a la obtenida en otros estudios con jugadores de fútbol sin parálisis cerebral. La altura de los jugadores e índice de masa corporal mostraron una correlación significativa con la altura del salto con contramovimiento (r=0,67 y r=-0,71, respectivamente).The aims of the present study were to determine in elite soccer players with cerebral palsy the jump height during a squat jump and during a countermovement jump, and to observe the relationship of the anthropometric parameters and the functional class with the jump height and the elastic index. Thirteen “soccer 7” players diagnosed with cerebral palsy took part in the study. The jump height for a squat jump (20.45±4.45 cm) and a countermovement jump (24.33±5.37 cm) was lower than the obtained in other studies in soccer players without cerebral palsy. The height of the players and their body mass index showed a significant correlation with the jump height during a countermovement jump (r=0.67 and r=- 0.71)