807 research outputs found

    The interception of a corner kick from the contraints-led perspective

    Full text link
    El comportamiento motor surge de la continua interacción entre tres limitadores (organismo, entorno y tarea), que nunca actúan de forma aislada. Este artículo estudia su efecto en el rendimiento, comportamiento motor y comportamiento visual de porteros de fútbol durante el lanzamiento de córner. 31 participantes, divididos en tres grupos en función del nivel de juego, intentaron atrapar el balón procedente del lanzamiento de córner en dos situaciones (estática y dinámica), mientras que se registraron sus movimientos oculares. Entre los resultados se observa que los expertos tienen un rendimiento más estable, mientras que los otros grupos rinden peor en la situación más difícil; que los expertos realizan un inicio más tardío de la carrera hacia el balón y un patrón motor más rápido para atraparlo; y que la información contenida en los jugadores implicados no es relevante, ya que los porteros dedican valores cercanos al 0% del tiempo total a su fijaciónMotor behavior arises from the continuous interaction between three constraints (organism, environment and task), which never act in isolation. This paper studies the effect of the constraints on the performance, motor behavior and visual search behavior of soccer goalkeepers during the corner kick. 31 participants, divided into three groups depending on the level of play, tried to catch the ball out of a corner kick in two situations (static and dynamic), while their eye movements were recorded. Among the results it is observed that the experts have a more stable performance, while the other groups perform worse in the most difficult situation; that the experts make a later start of their run up towards the ball and a faster motor pattern to catch it; and that the that the information of the players involved is not relevant, goalkeepers dedicate values close to 0% of their visual total time to themLa presente investigación se llevó a cabo mientras el primer autor y la segunda autora disfrutaban de una beca FPU (Formación del Profesorado Universitario) otorgada por el Ministerio de Educación, Cultura y Deporte del Gobierno de España

    Painlev\'e-Gullstrand synchronizations in spherical symmetry

    Full text link
    A Painlev\'e-Gullstrand synchronization is a slicing of the space-time by a family of flat spacelike 3-surfaces. For spherically symmetric space-times, we show that a Painlev\'e-Gullstrand synchronization only exists in the region where (dr)21(dr)^2 \leq 1, rr being the curvature radius of the isometry group orbits (22-spheres). This condition says that the Misner-Sharp gravitational energy of these 2-spheres is not negative and has an intrinsic meaning in terms of the norm of the mean extrinsic curvature vector. It also provides an algebraic inequality involving the Weyl curvature scalar and the Ricci eigenvalues. We prove that the energy and momentum densities associated with the Weinberg complex of a Painlev\'e-Gullstrand slice vanish in these curvature coordinates, and we give a new interpretation of these slices by using semi-metric Newtonian connections. It is also outlined that, by solving the vacuum Einstein's equations in a coordinate system adapted to a Painlev\'e-Gullstrand synchronization, the Schwarzschild solution is directly obtained in a whole coordinate domain that includes the horizon and both its interior and exterior regions.Comment: 16 page

    Microwave Background Anisotropies and Nonlinear Structures I. Improved Theoretical Models

    Full text link
    A new method is proposed for modelling spherically symmetric inhomogeneities in the Universe. The inhomogeneities have finite size and are compensated, so they do not exert any measurable gravitational force beyond their boundary. The region exterior to the perturbation is represented by a Friedmann-Robertson-Walker (FRW) Universe, which we use to study the anisotropy in the cosmic microwave background (CMB) induced by the cluster. All calculations are performed in a single, global coordinate system, with nonlinear gravitational effects fully incorporated. An advantage of the gauge choices employed here is that the resultant equations are essentially Newtonian in form. Examination of the problem of specifying initial data shows that the new model presented here has many advantages over `Swiss cheese' and other models. Numerical implementation of the equations derived here is described in a subsequent paper.Comment: 10 pages, 4 figures; Monthly Notices of the Royal Astronomical Society (MNRAS), in pres

    Chameleonic Generalized Brans--Dicke model and late-time acceleration

    Full text link
    In this paper we consider Chameleonic Generalized Brans--Dicke Cosmology in the framework of FRW universes. The bouncing solution and phantom crossing is investigated for the model. Two independent cosmological tests: Cosmological Redshift Drift (CRD) and distance modulus are applied to test the model with the observation.Comment: 20 pages, 15 figures, to be published in Astrophys. Space Sci. (2011

    Social sciences research in neglected tropical diseases 2: A bibliographic analysis

    Get PDF
    The official published version of the article can be found at the link below.Background There are strong arguments for social science and interdisciplinary research in the neglected tropical diseases. These diseases represent a rich and dynamic interplay between vector, host, and pathogen which occurs within social, physical and biological contexts. The overwhelming sense, however, is that neglected tropical diseases research is a biomedical endeavour largely excluding the social sciences. The purpose of this review is to provide a baseline for discussing the quantum and nature of the science that is being conducted, and the extent to which the social sciences are a part of that. Methods A bibliographic analysis was conducted of neglected tropical diseases related research papers published over the past 10 years in biomedical and social sciences. The analysis had textual and bibliometric facets, and focussed on chikungunya, dengue, visceral leishmaniasis, and onchocerciasis. Results There is substantial variation in the number of publications associated with each disease. The proportion of the research that is social science based appears remarkably consistent (<4%). A textual analysis, however, reveals a degree of misclassification by the abstracting service where a surprising proportion of the "social sciences" research was pure clinical research. Much of the social sciences research also tends to be "hand maiden" research focused on the implementation of biomedical solutions. Conclusion There is little evidence that scientists pay any attention to the complex social, cultural, biological, and environmental dynamic involved in human pathogenesis. There is little investigator driven social science and a poor presence of interdisciplinary science. The research needs more sophisticated funders and priority setters who are not beguiled by uncritical biomedical promises

    Performance of spanish white Macael marble exposed to narrow- and medium-range temperature cycling

    Get PDF
    Se aplican ciclos de estrés térmico de medio (100/-20 ºC y 75/-20 ºC) y bajo (50/-20 ºC) rango sobre probetas de mármol blanco de Macael (Almería, España), y se evalúa ciclo a ciclo su incidencia mediante ultrasonidos. Los resultados indican un considerable descenso de velocidad de los ultrasonidos en las muestras sometidas a estrés de 100/-20 ºC, más moderado en el caso de 75/-20 ºC, poco significativo en el caso de 50/-20 ºC. Las variaciones de velocidad tienen lugar durante los primeros 5-7 ciclos, permaneciendo los valores constantes en ciclos posteriores. Los resultados proporcionados por medidas de dureza de Schmidt, y de rotura por compresión uniaxial son coincidentes con los proporcionados por los ultrasonidos. Las imágenes de microscopía petrográfica y electrónica (SEM) manifiestan una cierta descohesión granular en zonas muy superficiales de las probetas sometidas a 40 ciclos de 100/-20 ºC. La coincidencia entre los datos por las técnicas de rotura por compresión, medidas de dureza superficial y ultrasonidos indican la validez de estas dos últimas —técnicas no destructivas, NDT— en el control de la incidencia de ciclos de stress térmico sobre las características mecánicas de materiales pétreos.White marble specimens from Macael in the Spanish province of Almeria were exposed to narrow- (50/ -20 ºC) and medium- (100/-20 ºC and 75/-20 ºC) range thermal stress cycles. The effects were monitored with ultrasound techniques. Ultrasound velocity declined considerably in samples subjected to 100/-20 ºC cycles, more moderately when the range was 75/-20 ºC and insignificantly when it was narrowed to 50/-20 ºC. All variations were recorded in the first five to seven cycles, with values flattening thereafter. The Schmidt hardness and compression test results concurred with the ultrasound findings. Petrographic and scanning electron microscope (SEM) imaging revealed some very superficial granular decohesion in the specimens subjected to forty 100/-20 ºC cycles. The concurrent results from compression testing on the one hand and surface hardness and ultrasound measurements on the other confirmed the validity of the latter two nondestructive techniques (NDT) for determining the effects of thermal stress cycling on stone mechanical strength.La investigación presentada en este artículo es parte del Proyecto MAT 2004-06804-CO2-0 del Plan Nacional de Investigación científica, Desarrollo e Innovación Tecnológica (Ministerio de Ciencia y Tecnología) y llevado a cabo en el Grupo de Investigación RNM 0179 de la Junta de Andalucía

    Caspase-8 binding to cardiolipin in giant unilamellar vesicles provides a functional docking platform for bid

    Get PDF
    Caspase-8 is involved in death receptor-mediated apoptosis in type II cells, the proapoptotic programme of which is triggered by truncated Bid. Indeed, caspase-8 and Bid are the known intermediates of this signalling pathway. Cardiolipin has been shown to provide an anchor and an essential activating platform for caspase-8 at the mitochondrial membrane surface. Destabilisation of this platform alters receptor-mediated apoptosis in diseases such as Barth Syndrome, which is characterised by the presence of immature cardiolipin which does not allow caspase-8 binding. We used a simplified in vitro system that mimics contact sites and/or cardiolipin-enriched microdomains at the outer mitochondrial surface in which the platform consisting of caspase-8, Bid and cardiolipin was reconstituted in giant unilamellar vesicles. We analysed these vesicles by flow cytometry and confirm previous results that demonstrate the requirement for intact mature cardiolipin for caspase-8 activation and Bid binding and cleavage. We also used confocal microscopy to visualise the rupture of the vesicles and their revesiculation at smaller sizes due to alteration of the curvature following caspase-8 and Bid binding. Biophysical approaches, including Laurdan fluorescence and rupture/tension measurements, were used to determine the ability of these three components (cardiolipin, caspase-8 and Bid) to fulfil the minimal requirements for the formation and function of the platform at the mitochondrial membrane. Our results shed light on the active functional role of cardiolipin, bridging the gap between death receptors and mitochondria

    She\u27s So Bubbly

    Get PDF
    We introduce the Automatic Learning for the Rapid Classification of Events (ALeRCE) broker, an astronomical alert broker designed to provide a rapid and self-consistent classification of large etendue telescope alert streams, such as that provided by the Zwicky Transient Facility (ZTF) and, in the future, the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST). ALeRCE is a Chilean-led broker run by an interdisciplinary team of astronomers and engineers working to become intermediaries between survey and follow-up facilities. ALeRCE uses a pipeline that includes the real-time ingestion, aggregation, cross-matching, machine-learning (ML) classification, and visualization of the ZTF alert stream. We use two classifiers: a stamp-based classifier, designed for rapid classification, and a light curve–based classifier, which uses the multiband flux evolution to achieve a more refined classification. We describe in detail our pipeline, data products, tools, and services, which are made public for the community (see https://alerce.science). Since we began operating our real-time ML classification of the ZTF alert stream in early 2019, we have grown a large community of active users around the globe. We describe our results to date, including the real-time processing of 1.5 × 10⁸ alerts, the stamp classification of 3.4 × 10⁷ objects, the light-curve classification of 1.1 × 10⁶ objects, the report of 6162 supernova candidates, and different experiments using LSST-like alert streams. Finally, we discuss the challenges ahead in going from a single stream of alerts such as ZTF to a multistream ecosystem dominated by LSST
    corecore