A search for new hot subdwarf stars by means of Virtual Observatory tools

Hot subdwarf stars are faint, blue objects, and are the main contributors to the far-UV excess observed in elliptical galaxies. They offer an excellent laboratory to study close and wide binary systems, and to scrutinize their interiors through asteroseismology, as some of them undergo stellar oscillations. However, their origins are still uncertain, and increasing the number of detections is crucial to undertake statistical studies. In this work, we aim at defining a strategy to find new, uncatalogued hot subdwarfs. Making use of Virtual Observatory tools we thoroughly search stellar catalogues to retrieve multi-colour photometry and astrometric information of a known sample of blue objects, including hot subdwarfs, white dwarfs, cataclysmic variables and main sequence OB stars. We define a procedure to discriminate among these spectral classes, particularly designed to obtain a hot subdwarf sample with a low contamination factor. In order to check the validity of the method, this procedure is then applied to two test sky regions: the Kepler FoV and to a test region of around (RA:225, DEC:5) deg. As a result, we obtained 38 hot subdwarf candidates, 23 of which had already a spectral classification. We have acquired spectroscopy for three other targets, and four additional ones have an available SDSS spectrum, which we used to determine their spectral type. A temperature estimate is provided for the candidates based on their spectral energy distribution, considering two-atmospheres fit for objects with clear infrared excess. Eventually, out of 30 candidates with spectral classification, 26 objects were confirmed to be hot subdwarfs, yielding a contamination factor of only 13%. The high rate of success demonstrates the validity of the proposed strategy to find new uncatalogued hot subdwarfs. An application of this method to the entire sky will be presented in a forthcoming work.Comment: 13 pages, 7 figure

Min-Max Predictive Control of a Five-Phase Induction Machine

In this paper, a fuzzy-logic based operator is used instead of a traditional cost function for the predictive stator current control of a five-phase induction machine (IM). The min-max operator is explored for the first time as an alternative to the traditional loss function. With this proposal, the selection of voltage vectors does not need weighting factors that are normally used within the loss function and require a cumbersome procedure to tune. In order to cope with conflicting criteria, the proposal uses a decision function that compares predicted errors in the torque producing subspace and in the x-y subspace. Simulations and experimental results are provided, showing how the proposal compares with the traditional method of fixed tuning for predictive stator current control.Ministerio de Economía y Competitividad DPI 2016-76493-C3-1-R y 2014/425Unión Europea DPI 2016-76493-C3-1-R y 2014/425Universidad de Sevilla DPI 2016-76493-C3-1-R y 2014/42

A Hamiltonian functional for the linearized Einstein vacuum field equations

By considering the Einstein vacuum field equations linearized about the Minkowski metric, the evolution equations for the gauge-invariant quantities characterizing the gravitational field are written in a Hamiltonian form by using a conserved functional as Hamiltonian; this Hamiltonian is not the analog of the energy of the field. A Poisson bracket between functionals of the field, compatible with the constraints satisfied by the field variables, is obtained. The generator of spatial translations associated with such bracket is also obtained.Comment: 5 pages, accepted in J. Phys.: Conf. Serie

Estudio de la marcha en la infancia

El análisis de la marcha se ha visto reforzado por la aparición de sistemas de invetigación de nueva tecnología como son las plataformas de fuerzas monitorizadas que permiten estudiar, con alta precisión, el desarrollo cinético y en parte cinemático de la marcha. Con este sistema hemos estudiado el paso de 62 niños de 5 y 6 años de edad, para determinar los valores de normalidad de los parámetros temporoespaciales y las magnitudes de las fuerzas de reacción pie-suelo en los tres ejes de plano espaciales. Hemos encontrado diferencias estadísticamente significativas entre estas edades para la longitud de paso, tiempo de doble apoyo y la mayoría de las fuerzas de reacción del suelo, indicando una evolución de la marcha en este periodo

Pilates Mat and body composition of postmenopausal women

El objetivo de este trabajo es cuantificar, mediante Absorciometría Dual Fotónica de Rayos- X (DXA), las modificaciones de la composición corporal que la práctica de Pilates Mat produce en mujeres posmenopaúsicas de vida sedentaria. Tras un programa de ejercicios de 9 meses de duración a razón de 2 sesiones por semana de 60 minutos cada una, se observó un aumento significativo del compartimento muscular a nivel de tronco (p=0,028), abdomen (p=0,010) y brazos (p=0,042), así como una disminución significativa de la grasa de las piernas (p=0,000). La densidad mineral ósea de la columna lumbar (L2, L3 y L4) también aumentó de forma significativa. Los resultados sugieren que la práctica de Pilates Mat en mujeres posmenopaúsicas mejora su composición corporalThe aim of this study was to quantify the changes in body composition after Mat Pilates practice in postmenopausal sedentary women using Dual X-ray Photon Absorptiometry (DXA). After a 9-month exercise program consisting of 2 sessions per week of 60 minutes each, a significant increase was observed in the muscle mass of the trunk (p = 0.028), abdomen (p = 0.010) and arms (p = 0.042). A significant decrease was observed in the leg fat mass (p = 0.000). Bone mineral density of the lumbar spine (L2, L3 and L4) also increased significantly. The results suggest that the practice of Mat Pilates in postmenopausal women improves their body compositio