4,177 research outputs found

    Oscillatory relaxation of zonal flows in a multi-species stellarator plasma

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    The low frequency oscillatory relaxation of zonal potential perturbations is studied numerically in the TJ-II stellarator (where it was experimentally detected for the first time). It is studied in full global gyrokinetic simulations of multi-species plasmas. The oscillation frequency obtained is compared with predictions based on single-species simulations using simplified analytical relations. It is shown that the frequency of this oscillation for a multi-species plasma can be accurately obtained from single-species calculations using extrapolation formulas. The damping of the oscillation and the influence of the different inter-species collisions is studied in detail. It is concluded that taking into account multiple kinetic ions and electrons with impurity concentrations realistic for TJ-II plasmas allows to account for the values of frequency and damping rate in zonal flows relaxations observed experimentally.Comment: 11 figures, 22 page

    Note: "Lock-in accelerometry" to follow sink dynamics in shaken granular matter

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    Understanding the penetration dynamics of intruders in granular beds is relevant not only for fundamental Physics, but also for geophysical processes and construction on sediments or granular soils in areas potentially affected by earthquakes. While the penetration of intruders in two dimensional (2D) laboratory granular beds can be followed using video recording, it is useless in three dimensional (3D) beds of non-transparent materials such as common sand. Here we propose a method to quantify the sink dynamics of an intruder into laterally shaken granular beds based on the temporal correlations between the signals from a reference accelerometer fixed to the shaken granular bed, and a probe accelerometer deployed inside the intruder. Due to its analogy with the working principle of a lock in amplifier, we call this technique Lock in accelerometry (LIA). During Earthquakes, some soils can lose their ability to sustain shear and deform, causing subsidence and sometimes substantial building damage due to deformation or tumblin

    Use of water troughs by wild rabbits (Oryctolagus cuniculus) in a farmland area of north–west Spain

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    Uso de bebederos por parte del conejo de monte (Oryctolagus cuniculus) en un paisaje agrícola en el noroeste de EspañaEn la península Ibérica, los bebederos son una herramienta de gestión de hábitat muy frecuente para incrementar las densidades de especies de caza menor, aunque el comportamiento de ingestión de agua de las especies “diana” no se ha estudiado en profundidad, como es el caso del conejo de monte (Oryctolagus cuniculus). Estudiamos el uso de bebederos por parte de conejos de monte durante 228 períodos de una semana en tres períodos consecutivos (junio–octubre) de 2008, 2009 y 2010 en un paisaje agrícola de noroeste de España, utilizando cámaras de fototrampeo. Los conejos utilizaron el 43% de los bebederos y se observó un número significativamente mayor de conejos bebiendo en bebederos rodeados por cobertura vegetal en comparación con bebederos situados en campos abiertos sin dicha cobertura vegetal. La mayoría de los conejos que bebieron fueron fotografiados de julio a septiembre (98%), si bien la utilización de bebederos no se relacionó claramente con la climatología. Los conejos bebieron principalmente durante la mañana (52% de los conejos) no tanto durante la tarde y noche, y raramente durante el mediodía. Los conejos se fotografiaron junto con perdices rojas (Alectoris rufa) en el 6% de las fotografías. Estos hallazgos sugieren que los bebederos son útiles para el conejo y otras especies con necesidades hídricas similares y que debieran ser colocados cerca de zonas con cobertura vegetal arbustiva.Installation of water troughs is a common approach to increase densities of small game species in the Iberian peninsula but little is known about the watering patterns of target species, such as the wild rabbit (Oryctolagus cuniculus). Using camera trapping, we monitored the use of water troughs by wild rabbits over 228 weeks in three consecutive periods, from June to October in 2008, 2009 and 2010, on farmland in north–west Spain. Wild rabbits used 43% of the water troughs. A significantly higher number of rabbits were observed drinking at troughs surrounded by shrub cover than at those in open fields. Most drinking events were recorded from July to September (98%), though the use of water troughs was not clearly related to weather. Wild rabbits drank mainly during the morning (52% of rabbits), less so in the evening and at night, and rarely in the afternoon. Wild rabbits were photographed together with red–legged partridges (Alectoris rufa) in 6% of photographs. These findings suggest water troughs are useful for species such as wild rabbits and should be allocated close to shrub areas.Uso de bebederos por parte del conejo de monte (Oryctolagus cuniculus) en un paisaje agrícola en el noroeste de EspañaEn la península Ibérica, los bebederos son una herramienta de gestión de hábitat muy frecuente para incrementar las densidades de especies de caza menor, aunque el comportamiento de ingestión de agua de las especies “diana” no se ha estudiado en profundidad, como es el caso del conejo de monte (Oryctolagus cuniculus). Estudiamos el uso de bebederos por parte de conejos de monte durante 228 períodos de una semana en tres períodos consecutivos (junio–octubre) de 2008, 2009 y 2010 en un paisaje agrícola de noroeste de España, utilizando cámaras de fototrampeo. Los conejos utilizaron el 43% de los bebederos y se observó un número significativamente mayor de conejos bebiendo en bebederos rodeados por cobertura vegetal en comparación con bebederos situados en campos abiertos sin dicha cobertura vegetal. La mayoría de los conejos que bebieron fueron fotografiados de julio a septiembre (98%), si bien la utilización de bebederos no se relacionó claramente con la climatología. Los conejos bebieron principalmente durante la mañana (52% de los conejos) no tanto durante la tarde y noche, y raramente durante el mediodía. Los conejos se fotografiaron junto con perdices rojas (Alectoris rufa) en el 6% de las fotografías. Estos hallazgos sugieren que los bebederos son útiles para el conejo y otras especies con necesidades hídricas similares y que debieran ser colocados cerca de zonas con cobertura vegetal arbustiva

    Metodologías e indicadores académicos, económicos, sociales y tecnológicos para la evaluación del impacto de la investigación científica universitaria

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    Given the importance of the research component to provide pertinent answers to economic and social problems and demands, decision-making in terms of scientific policy, resource management and infrastructure development in university institutions, it is necessary to evaluate the impact of scientific investigations carried out. Research is a strategy of searching for knowledge, as well as a source of innovation and constant learning of reality, becoming a key factor for technological and educational transformation. The purpose of this review article is to perform an analysis of the different methodologies and indicators academic, economic, social and technological that have been implemented to evaluate the impact of university research.Given the importance of the research component to provide pertinent answers to economic and social problems and demands, decision-making in terms of scientific policy, resource management and infrastructure development in university institutions, it is necessary to evaluate the impact of scientific investigations carried out. Research is a strategy of searching for knowledge, as well as a source of innovation and constant learning of reality, becoming a key factor for technological and educational transformation. The purpose of this review article is to perform an analysis of the different methodologies and indicators academic, economic, social and technological that have been implemented to evaluate the impact of university research.Dada la importancia del componente investigación para dar respuestas pertinentes a los problemas y demandas económicas y sociales, toma de decisiones en términos de política científica, gestión de recursos y desarrollo de infraestructura en las instituciones universitarias se hace necesario evaluar el impacto de las investigaciones científicas ejecutadas. La investigación es una estrategia de búsqueda del conocimiento, así como fuente de innovación y aprendizaje constante de la realidad, constituyéndose en un factor clave para la transformación tecnológica y educativa. El propósito de este artículo de revisión es realizar un análisis de las diferentes metodologías e indicadores académicos, económicos, sociales y tecnológicos que se han implementado para evaluar el impacto de las investigaciones universitarias

    Disorder induced phase segregation in La2/3Ca1/3MnO3 manganites

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    Neutron powder diffraction experiments on La2/3Ca1/3MnO3 over a broad temperature range above and below the metal-insulator transition have been analyzed beyond the Rietveld average approach by use of Reverse Monte Carlo modelling. This approach allows the calculation of atomic pair distribution functions and spin correlation functions constrained to describe the observed Bragg and diffuse nuclear and magnetic scattering. The results evidence phase separation within a paramagnetic matrix into ferro and antiferromagnetic domains correlated to anistropic lattice distortions in the vicinity of the metal-insulator transition.Comment: 3 pages, 4 figures. Submitted to Phys. Rev. Lett. Figure 1 replace

    Renormalization Group Analysis of a Quivering String Model of Posture Control

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    Scaling concepts and renormalization group (RG) methods are applied to a simple linear model of human posture control consisting of a trembling or quivering string subject to damping and restoring forces. The string is driven by uncorrelated white Gaussian noise intended to model the corrections of the physiological control system. We find that adding a weak quadratic nonlinearity to the posture control model opens up a rich and complicated phase space (representing the dynamics) with various non-trivial fixed points and basins of attraction. The transition from diffusive to saturated regimes of the linear model is understood as a crossover phenomenon, and the robustness of the linear model with respect to weak non-linearities is confirmed. Correlations in posture fluctuations are obtained in both the time and space domain. There is an attractive fixed point identified with falling. The scaling of the correlations in the front-back displacement, which can be measured in the laboratory, is predicted for both the large-separation (along the string) and long-time regimes of posture control.Comment: 20 pages, 13 figures, RevTeX, accepted for publication in PR

    The intriguing HI gas in NGC 5253: an infall of a diffuse, low-metallicity HI cloud?

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    (Abridged) We present new, deep HI line and 20-cm radio continuum data of the very puzzling blue compact dwarf galaxy NGC 5253, obtained with the ATCA as part of the `Local Volume HI Survey' (LVHIS). Our low-resolution HI maps show the disturbed HI morphology that NGC 5253 possesses, including tails, plumes and detached HI clouds. The high-resolution map reveals an HI plume at the SE and an HI structure at the NW that surrounds an Ha shell. We confirm that the kinematics of the neutral gas are highly perturbed and do not follow a rotation pattern. We discuss the outflow and infall scenarios to explain such disturbed kinematics, analyze the environment in which it resides, and compare it properties with those observed in similar star-forming dwarf galaxies. The radio-continuum emission of NGC 5253 is resolved and associated with the intense star-forming region at the center of the galaxy. We complete the analysis using multiwavelength data extracted from the literature. We estimate the SFR using this multiwavelength approach. NGC 5253 does not satisfy the Schmidt-Kennicutt law of star-formation, has a very low HI mass-to-light ratio when comparing with its stellar mass, and seems to be slightly metal-deficient in comparison with starbursts of similar baryonic mass. Taking into account all available multiwavelength data, we conclude that NGC 5253 is probably experiencing the infall of a diffuse, low-metallicity HI cloud along the minor axis of the galaxy, which is comprising the ISM and triggering the powerful starburst. The tidally disturbed material observed at the east and north of the galaxy is a consequence of this interaction, which probably started more than 100 Myr ago. The origin of this HI cloud may be related with a strong interaction between NGC 5253 and the late-type spiral galaxy M 83 in the past.Comment: 19 pages, 12 figures, accepted for publication in MNRA

    Dynamic screening of a localized hole during photoemission from a metal cluster

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    Recent advances in attosecond spectroscopy techniques have fueled the interest in the theoretical description of electronic processes taking place in the subfemtosecond time scale. Here we study the coupled dynamic screening of a localized hole and a photoelectron emitted from a metal cluster using a semi-classical model. Electron density dynamics in the cluster is calculated with Time-Dependent Density Functional Theory and the motion of the photoemitted electron is described classically. We show that the dynamic screening of the hole by the cluster electrons affects the motion of the photoemitted electron. At the very beginning of its trajectory, the photoemitted electron interacts with the cluster electrons that pile up to screen the hole. Within our model, this gives rise to a significant reduction of the energy lost by the photoelectron. Thus, this is a velocity dependent effect that should be accounted for when calculating the average losses suffered by photoemitted electrons in metals.Comment: 15 pages, 5 figure

    Atezolizumab in locally advanced or metastatic urothelial cancer : a pooled analysis from the Spanish patients of the IMvigor 210 cohort 2 and 211 studies

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    Funding: This study was funded by Roche Farma, Spain.The studies IMvigor 210 cohort 2 and IMvigor211 evaluated the efficacy of atezolizumab in patients with locally advanced or metastatic urothelial cancer (mUC) upon progression to platinum-based chemotherapy worldwide. Yet, the real impact of this drug in specific geographical regions is unknown. We combined individual-level data from the 131 patients recruited in Spain from IMvigor210 cohort 2 and IMvigor211 in a pooled analysis. Efficacy and safety outcomes were assessed in the overall study population and according to PD-L1 expression on tumour-infiltrating immune cells. Full data were available for 127 patients; 74 (58%) received atezolizumab and 53 (42%) chemotherapy. Atezolizumab patients had a numerically superior median overall survival although not reaching statistical significance (9.2 months vs 7.7 months). No statistically significant differences between arms were observed in overall response rates (20.3% vs 37.0%) or progression-free survival (2.1 months vs 5.3 months). Nonetheless, median duration of response was superior for the immunotherapy arm (non-reached vs 6.4 months; p = 0.005). Additionally, among the responders, the 12-month survival rates seemed to favour atezolizumab (66.7% vs 19.9%). When efficacy was analyzed based on PD-L1 expression status, no significant differences were found. Treatment-related adverse events of any grade occurred more frequently in the chemotherapy arm [46/57 (81%) vs 44/74 (59%)]. Patients who achieved an objective response on atezolizumab presented a longer median duration of response and numerically superior 12 month survival rates when compared with chemotherapy responders along with a more favorable safety profile. PD-L1 expression did not discriminate patients who might benefit from atezolizumab
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