Free Form of the Foldy-Wouthuysen Transformation in External Electromagnetic Fields

We derive the exact Foldy-Wouthuysen transformation for Dirac fermions in a time independent external electromagnetic field in the basis of the Ritus eigenfunctions, namely the eigenfunctions of the operator $(\gamma \cdot \Pi)^2$, with $\Pi^\mu = p^\mu - e A^\mu$. In this basis, the transformation acquires a free form involving the dynamical quantum numbers induced by the field.Comment: 8 pages. Accepted in J. Phys. A: Math. and Theo. (Fast Track Communication

Quantum Entanglement in (d−1)(d-1)-Spherium

There are very few systems of interacting particles (with continuous variables) for which the entanglement of the concomitant eigenfunctions can be computed in an exact, analytical way. Here we present analytical calculations of the amount of entanglement exhibited by $s$-states of \emph{spherium}. This is a system of two particles (electrons) interacting via a Coulomb potential and confined to a $(d-1)$-sphere (that is, to the surface of a $d$-dimensional ball). We investigate the dependence of entanglement on the radius $R$ of the system, on the spatial dimensionality $d$, and on energy. We find that entanglement increases monotonically with $R$, decreases with $d$, and also tends to increase with the energy of the eigenstates. These trends are discussed and compared with those observed in other two-electron atomic-like models where entanglement has been investigated.Comment: 14 pages, 6 figures. J. Phys. A (2015). Accepte

Explosive first-order transition to synchrony in networked chaotic oscillators

Critical phenomena in complex networks, and the emergence of dynamical abrupt transitions in the macroscopic state of the system are currently a subject of the outmost interest. We report evidence of an explosive phase synchronization in networks of chaotic units. Namely, by means of both extensive simulations of networks made up of chaotic units, and validation with an experiment of electronic circuits in a star configuration, we demonstrate the existence of a first order transition towards synchronization of the phases of the networked units. Our findings constitute the first prove of this kind of synchronization in practice, thus opening the path to its use in real-world applications.Comment: Phys. Rev. Lett. in pres

Efecto de factores contextuales en la composición corporal de jugadores profesionales de fútbol. Un estudio retrospectivo

La exigencia de las demandas físicas en el fútbol ha evolucionado en los últimos años, poniendo de manifiesto la necesidad de investigar sobre aquellos aspectos que condicionan el rendimiento deportivo. Es por esto que el objetivo de este estudio fue describir la incidencia del entrenamiento individualizado, la compañía en las comidas, la raza y la demarcación sobre las variables antropométricas en jugadores de fútbol profesional. Para ello se desarrolló un estudio retrospectivo sobre 51 jugadores profesionales de la Segunda División B española durante las temporadas de 2015/2016, 2016/2017 y 2017/2018. La valoración antropométrica se realizó bajo las normas técnicas de medición recomendadas por el International Working Group of Kinanthropometry, adoptadas por la International Society for the Advancement of Kinanthropometry (ISAK). Los resultados revelaron que el entrenamiento individualizado y la compañía en las comidas fueron los factores que más influyeron sobre las variables antropométricas. Los valores de masa grasa y de masa muscular, y el sumatorio de pliegues son sensibles al efecto de la intervención sobre dichos factores. Los mayores niveles de interacción se producen entre la compañía en las comidas y el entrenamiento individualizado, y entre la demarcación y la compañía en las comidas. Considerando la composición corporal como un aspecto a tener en cuenta en el desarrollo del rendimiento, se concluye que la aplicación de ciertos contenidos del entrenamiento según las características individuales y el estilo de vida de los jugadores es un factor que posee una influencia significativa sobre los futbolistas profesionales

Innovación de la metodología docente en Farmacología a través del cine como recurso formativo.

Estudio interuniversitario del uso de las películas comerciales, como recurso educativo innovador, en la enseñanza de la Farmacología de manera sistemática en los alumnos de dicha asignatura de las universidades de Cádiz y Málaga. Cabello MR, Medina I, Moreno R. Innovación de la metodología docente en Farmacología a través del cine como recurso formativo.FEMVol. 20 (S2) Suplemento 2, Octubre 2017 ISSN: 2014-9832Objetivo Analizar la adquisición de competencias transversales, el grado de satisfacción y motivación de los alumnos de Farmacología con la utilización de las películas comerciales como recurso docente. MATERIAL Y METODOS Se realizó: 1- Preevaluación. Presentación y visualización de la película. 2- Resolución de las cuestiones planteadas con el trabajo personal y de grupo. 3- Debate. Realización de un postest, encuesta de satisfacción y valoración de la actividad por los estudiantes participantes. Valoración y análisis de los cuestionarios y análisis textual qualitativo de las observaciones de las encuestas de satisfacción. Resultados En todas las cuestiones de satisfacción de la actividad han considerado estar satisfechos/muy satisfechos el 70% de los estudiantes participantes. Confirmación de adquisición de competencias transversales y específicas de farmacología. Conclusión El recurso visual aumenta la motivación y el grado de satisfacción de los estudiantes. Se facilita el debate y discusión de puntos propuestos por el docente y los estudiantes, con un mayor aprovechamiento de la actividad. Consideramos una metodología muy útil y eficaz en el aprendizaje activo de los estudiantes.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

The last glacial termination on the eastern flank of the central Patagonian Andes (47ºS)

Few studies have examined in detail the sequence of events during the last glacial termination (T1) in the core sector of the Patagonian Ice Sheet (PIS), the largest ice mass in the Southern Hemisphere outside of Antarctica. Here we report results from Lago Edita (47°8′ S, 72°25′ W, 570 m a.s.l.), a small closed-basin lake located in a valley overridden by eastward-flowing Andean glaciers during the Last Glacial Maximum (LGM). The Lago Edita record shows glaciolacustrine sedimentation until 19 400 yr BP, followed by organic sedimentation in a closed-basin lake and a mosaic of cold-resistant hygrophilous conifers and rainforest trees, along with alpine herbs between 19 400 and 11 000 yr BP. Our data suggest that the PIS retreated at least  ∼  90 km from its LGM limit between  ∼  21 000 and 19 400 yr BP and that scattered, low-density populations of cold-resistant hygrophilous conifers, rainforest trees, high-Andean and steppe herbs thrived east of the Andes during the LGM and T1, implying high precipitation levels and southern westerly wind (SWW) influence at 47° S. The conifer Podocarpus nubigena increased between 14 500 and 13 000 yr BP, suggesting even stronger SWW influence during the Antarctic Cold Reversal, after which it declined and persisted until 11 000 yr BP. Large increases in arboreal pollen at  ∼  13 000 and  ∼  11 000 yr BP led to the establishment of forests near Lago Edita between 10 000 and 9000 yr BP, suggesting a rise in the regional tree line along the eastern Andean slopes driven by warming pulses at  ∼  13 000 and  ∼  11 000 yr BP and a subsequent decline in SWW influence at  ∼  11 000 yr BP. We propose that the PIS imposed a regional cooling signal along its eastern, downwind margin through T1 that lasted until the separation of the northern and southern Patagonian ice fields along the Andes during the Younger Dryas period. We posit that the withdrawal of glacial and associated glaciolacustrine environments through T1 provided a route for the dispersal of hygrophilous trees and herbs from the eastern flank of the central Patagonian Andes, contributing to the afforestation of the western Andean slopes and pacific coasts of central Patagonia during T1.Fil: Henríquez, William I.. Victoria University Of Wellington; Nueva ZelandaFil: Villa-Martinez, Rodrigo. Gaia-antártica Universidad de Magallanes; ChileFil: Vilanova, Isabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales ; ArgentinaFil: De Pol-Holz, Ricardo. Gaia-antártica Universidad de Magallanes; ChileFil: Moreno, Patricio. Instituto de Ecología y Biodiversidad, Departamento de; Chil

Disorder in quantum vacuum: Casimir-induced localization of matter waves

Disordered geometrical boundaries such as rough surfaces induce important modifications to the mode spectrum of the electromagnetic quantum vacuum. In analogy to Anderson localization of waves induced by a random potential, here we show that the Casimir-Polder interaction between a cold atomic sample and a rough surface also produces localization phenomena. These effects, that represent a macroscopic manifestation of disorder in quantum vacuum, should be observable with Bose-Einstein condensates expanding in proximity of rough surfaces

Occurrence of Clinical and Sub-Clinical Mastitis in Dairy Herds in the West Littoral Region in Uruguay

Twenty-nine dairy farms were selected to determine the incidence of clinical mastitis, prevalence of sub-clinical mastitis and bacterial aetiology in the West Littoral Region of Uruguay. In samples taken by the owner and frozen at -20°C during a week the incidence rate of clinical mastitis was determined as 1.2 cases per 100 cow-months at risk. Staphylococcus aureus was the most common isolated pathogen in 37.5% of 40 milk samples from clinical cases obtained in 1 month. No bacteria grew in the 32.5% of the total samples. A sub-sample including 1077 dairy cows from randomly selected farms was used to determine the prevalence of sub-clinical mastitis. These samples were taken on one visit to each farm. The prevalence was 52.4% on a cow basis and 26.7% on an udder quarter basis. In 55.1% of the quarters of the selected animals with more than 300 000 cells/ml there was no growth. The isolated pathogens from sub-clinical cases and their relative frequencies were: Staphylococcus aureus 62.8%, Streptococcus agalactiae 11.3%, Enterococcus sp. 8%, coagulase-negative staphylococci 7.4%, Streptococus uberis 6.4%, Streptococcus dysgalactiae 1.8%, Escherichia coli 1.5% and Staphylococcus hyicus coagulase-positive 0.6%

Improved energy-efficiency in cloud datacenters with interference-aware virtual machine placement

Virtualization is one of the main technologies used for improving resource efficiency in datacenters; it allows the deployment of co-existing computing environments over the same hardware infrastructure. However, the co-existing of environments — along with management inefficiencies — often creates scenarios of high-competition for resources between running workloads, leading to performance degradation. This phenomenon is known as Performance Interference, and introduces a non-negligible overhead that affects both a datacenter's Quality of Service and its energy-efficiency. This paper introduces a novel approach to workload allocation that improves energy-efficiency in Cloud datacenters by taking into account their workload heterogeneity. We analyze the impact of performance interference on energy-efficiency using workload characteristics identified from a real Cloud environment, and develop a model that implements various decision-making techniques intelligently to select the best workload host according to its internal interference level. Our experimental results show reductions in interference by 27.5% and increased energy-efficiency up to 15% in contrast to current mechanisms for workload allocation