Interception of a corner kick in football: A task analysis

Debido a la inexistencia de estudios previos, la presente investigación tiene como objetivo realizar un análisis de la tarea, que es atrapar un balón procedente de un lanzamiento de córner. Para ello se analizó el rendimiento, el comportamiento motor y los movimientos oculares de jóvenes porteros cuando realizaban esta tarea. Además se compararon las variables en función de los aciertos o fallos durante el blocaje. Los resultados muestran que los fallos en el blocaje se deben a que los porteros iniciaron su carrera demasiado pronto y además utilizaron un patrón inadecuado del movimiento de sus manos y salto. El análisis de los movimientos oculares muestra que el balón es la zona informativa más importante, pero no se obtienen diferencias entre los aciertos y los fallos en el blocajeDue to the inexistence of previous studies, the present research is aimed at performing an analysis of the task of intercepting a ball coming from a corner kick. With that objective in mind, the motor behaviour and eye movements of young goalkeepers were analysed when performing the aforementioned task. Also, variables dependent on the number of right and wrong movements during the interception were compared. Results show that errors in blocking are due to the fact that goalkeepers began their run too early and also used an inadequate pattern of hand movement and jump. The analysis of eye movements shows that the ball is the most important informational zone, but no differences were found between hits and misses in the interception.La presente investigación se llevo a cabo mientras el primer autor disfrutaba de una beca FPU (Formación del Profesorado Universitario) otorgada por el Ministerio de Educación, Cultura y Deporte del Gobierno de Españ

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

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

Carnot, Stirling, Ericsson stochastic heat engines: Efficiency at maximum power

This work obtains the efficiency at maximum power for a stochastic heat engine performing Carnot-like, Stirling-like and Ericsson-like cycles. For the mesoscopic engine a Brownian particle trapped by an optical tweezers is considered. The dynamics of this stochastic engine is described as an overdamped Langevin equation with a harmonic potential, whereas is in contact with two thermal baths at different temperatures, namely, hot ($T_h$) and cold ($T_c$). The harmonic oscillator Langevin equation is transformed into a macroscopic equation associated with the mean value $\langle x^2(t)\rangle$ using the original Langevin approach. At equilibrium stationary state this quantity satisfies a state-like equation from which the thermodynamic properties are calculated. To obtained the efficiency at maximum power it is considered the finite-time cycle processes under the framework of low dissipation approach.Comment: 2 3pages, 5 figure

Electronic plasma diffusion with radiation reaction force and time-dependent electric field

In this work the explicit solution of the electronic plasma diffusion with radiation reaction force, under the action of an exponential decay external electric field is given. The electron dynamics is described by a classical generalized Langevin equation characterized by an Ornstein-Uhlenbeck-type friction memory kernel, with an effective memory time which accounts for the effective thermal interaction between the electron and its surroundings (thermal collisions between electrons + radiation reaction force). The incident electric field exerts an electric force on the electron, which in turn can induce an additional damping to the braking radiation force, allowing a delay in the electron characteristic time. This fact allows that the effective memory time be finite and positive, and as a consequence, obtaining physically admissible solutions of the stochastic Abraham-Lorentz-like equation. It is shown that the diffusion process is quasi-Markovian which includes the radiation effects.Comment: 16 pages, 8 figure

An unidentified TeV source in the vicinity of Cygnus OB2

Deep observation (∼113 hrs) of the Cygnus region at TeV energies using the HEGRA stereoscopic system of air Čerenkov telescopes has serendipitously revealed a signal positionally inside the core of the OB association Cygnus OB2, at the edge of the 95% error circle of the EGRET source 3EG J2033+4118, and ∼0.5° north of Cyg X-3. The source centre of gravity is RA αJ2000: 20hr32m07s± 9.2stats±2.2syss, Dec δJ2000: +41°30′30″2.0stat±0.4′sys. The source is steady, has a post-trial significance of +4.6σ, indication for extension with radius 5.6′ at the ∼3σ level, and has a differential power-law flux with hard photon index of - 1.9 ± 0.3stat ± 0.3sys. The integral flux above 1 TeV amounts ∼3% that of the Crab. No counterpart for the TeV source at other wavelengths is presently identified, and its extension would disfavour an exclusive pulsar or AGN origin. If associated with Cygnus OB2, this dense concentration of young, massive stars provides an environment conducive to multi-TeV particle acceleration and likely subsequent interaction with a nearby gas cloud. Alternatively, one could envisage γ-ray production via a jet-driven termination shock.F. A. Aharonian, ... G. P. Rowell, ... [et al

The Analyticity of a Generalized Ruelle's Operator

In this work we propose a generalization of the concept of Ruelle operator for one dimensional lattices used in thermodynamic formalism and ergodic optimization, which we call generalized Ruelle operator, that generalizes both the Ruelle operator proposed in [BCLMS] and the Perron Frobenius operator defined in [Bowen]. We suppose the alphabet is given by a compact metric space, and consider a general a-priori measure to define the operator. We also consider the case where the set of symbols that can follow a given symbol of the alphabet depends on such symbol, which is an extension of the original concept of transition matrices from the theory of subshifts of finite type. We prove the analyticity of the Ruelle operator and present some examples

Long-range pollution transport during the MILAGRO-2006 campaign: a case study of a major Mexico City outflow event using free-floating altitude-controlled balloons

One of the major objectives of the Megacities Initiative: Local And Global Research Observations (MILAGRO-2006) campaign was to investigate the long-range transport of polluted Mexico City Metropolitan Area (MCMA) outflow and determine its downwind impacts on air quality and climate. Six research aircraft, including the National Center for Atmospheric Research (NCAR) C-130, made extensive chemical, aerosol, and radiation measurements above MCMA and more than 1000 km downwind in order to characterize the evolution of the outflow as it aged and dispersed over the Mesa Alta, Sierra Madre Oriental, Coastal Plain, and Gulf of Mexico. As part of this effort, free-floating Controlled-Meteorological (CMET) balloons, commanded to change altitude via satellite, made repeated profile measurements of winds and state variables within the advecting outflow. In this paper, we present an analysis of the data from two CMET balloons that were launched near Mexico City on the afternoon of 18 March 2006 and floated downwind with the MCMA pollution for nearly 30 h. The repeating profile measurements show the evolving structure of the outflow in considerable detail: its stability and stratification, interaction with other air masses, mixing episodes, and dispersion into the regional background. Air parcel trajectories, computed directly from the balloon wind profiles, show three transport pathways on 18–19 March: (a) high-altitude advection of the top of the MCMA mixed layer, (b) mid-level outflow over the Sierra Madre Oriental followed by decoupling and isolated transport over the Gulf of Mexico, and (c) low-level outflow with entrainment into a cleaner northwesterly jet above the Coastal Plain. The C-130 aircraft intercepted the balloon-based trajectories three times on 19 March, once along each of these pathways; in all three cases, peaks in urban tracer concentrations and LIDAR backscatter are consistent with MCMA pollution. In comparison with the transport models used in the campaign, the balloon-based trajectories appear to shear the outflow far more uniformly and decouple it from the surface, thus forming a thin but expansive polluted layer over the Gulf of Mexico that is well aligned with the aircraft observations. These results provide critical context for the extensive aircraft measurements made during the 18–19 March MCMA outflow event and may have broader implications for modelling and understanding long-range transport

Mesenchymal stem cell-based therapy for ischemic stroke

Ischemic stroke represents a major, worldwide health burden with increasing incidence. Patients affected by ischemic strokes currently have few clinically approved treatment options available. Most currently approved treatments for ischemic stroke have narrow therapeutic windows, severely limiting the number of patients able to be treated. Mesenchymal stem cells represent a promising novel treatment for ischemic stroke. Numerous studies have demonstrated that mesenchymal stem cells functionally improve outcomes in rodent models of ischemic stroke. Recent studies have also shown that exosomes secreted by mesenchymal stem cells mediate much of this effect. In the present review, we summarize the current literature on the use of mesenchymal stem cells to treat ischemic stroke. Further studies investigating the mechanisms underlying mesenchymal stem cells tissue healing effects are warranted and would be of benefit to the field

On the general one-dimensional XY Model: positive and zero temperature, selection and non-selection

We consider $(M,d)$ a connected and compact manifold and we denote by $\mathcal{B}_i$ the Bernoulli space $M^{\Z}$ of sequences represented by $$x=(... x_{-3},x_{-2},x_{-1},x_0,x_1,x_2,x_3,...),$$ where $x_i$ belongs to the space (alphabet) $M$. The case where $M=\mathbb{S}^1$, the unit circle, is of particular interest here. The analogous problem in the one-dimensional lattice $\mathbb{N}$ is also considered. %In this case we consider the potential $A: {\cal B}=M^\mathbb{N} \to \mathbb{R}.$ Let A: \mathcal{B}_i \rar \R be an {\it observable} or {\it potential} defined in the Bernoulli space $\mathcal{B}_i$. The potential $A$ describes an interaction between sites in the one-dimensional lattice $M^\mathbb{Z}$. Given a temperature $T$, we analyze the main properties of the Gibbs state $\hat{\mu}_{\frac{1}{T} A}$ which is a certain probability measure over ${\cal B}_i$. We denote this setting "the general XY model". In order to do our analysis we consider the Ruelle operator associated to $\frac{1}{T} A$, and, we get in this procedure the main eigenfunction $\psi_{\frac{1}{T} A}$. Later, we analyze selection problems when temperature goes to zero: a) existence, or not, of the limit (on the uniform convergence) $$V:=\lim_{T\to 0} T\, \log(\psi_{\frac{1}{T} A}),\,\,\,\,\text{a question about selection of subaction},$$ and, b) existence, or not, of the limit (on the weak$^*$ sense) $$\tilde{\mu}:=\lim_{T\to 0} \hat{\mu}_{\frac{1}{T}\, A},\,\,\,\,\text{a question about selection of measure}.$$ The existence of subactions and other properties of Ergodic Optimization are also considered