3,388 research outputs found

    Structural instability of vortices in Bose-Einstein condensates

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    In this paper we study a gaseous Bose-Einstein condensate (BEC) and show that: (i) A minimum value of the interaction is needed for the existence of stable persistent currents. (ii) Vorticity is not a fundamental invariant of the system, as there exists a conservative mechanism which can destroy a vortex and change its sign. (iii) This mechanism is suppressed by strong interactions.Comment: 4 pages with 3 figures. Submitted to Phys. Rev. Let

    Uso del fuego prescrito para la creación de rodales cortafuegos: estudio del caso de Las Mesas de Ana López,Vega de San Mateo, Gran Canaria (España)

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    Wildland fire regimes are changing in Gran Canaria (Canary Islands, SW Spain) and large wildland fires (LWFs) are more likely to occur. This is a major change in the disturbance regime and it is a real threat for biodiversity. This paper studies prescribed burning as a mean to create fire resistant stands to allow wildland fire control. It is based in the recent (2002-2005) prescribed burning program in Gran Canaria. We are interested not only in setting fuel-breaks but in providing strategic locations for those (after Farsite and FlamMap simulations). In this paper, we also show a case study for the Mesas (August 17th, 2004) wildland fire and the prescribed burn fuel breaks established around it in the last years in which this fire was successfully anchor.Los regímenes de fuegos forestales están cambiando en Gran Canaria y los grandes incendios forestales son más probables que antiguamente. Esto es un cambio importante en el régimen de perturbaciones y una grave amenaza a la biodiversidad. El Plan de Prevención de Incendios Forestales de Gran Canaria, año 2002 dejó clara la obligación de cambiar las estructuras de vegetación de la Isla en dos ámbitos: paisaje y protección de zonas sensibles. El uso de fuego prescrito (años 2002-2005) ha resultado ser una herramienta especialmente eficiente en este ámbito y muy adecuada para compatibilizar las acciones de prevención de incendios con el mantenimiento de los procesos ecológicos. Estas primeras experiencias en Gran Canaria muestran la idoneidad de los tratamientos para establecer rodales resistentes al paso del fuego en zonas estratégicas (deducidas tras simulación con Farsite y FlamMap). Y revelan lo conveniente que es que estos rodales resistentes estén distribuidos por nuestros montes de modo que los incendios potencialmente grandes encuentren zonas en las que sea factible controlar los perímetros. Este control se pudo hacer eficientemente en el incendio de las Mesas de 17 de agosto de 2004

    Structural social capital and knowledge acquisition: implications of cluster membership

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    This paper analyzes the implications of belonging to a cluster through the relationship between structural capital and knowledge acquisition. Findings suggest structural social capital affects only indirectly to the knowledge acquisition through the relational and cognitive dimensions for firms member of the cluster . However, structural dimension also maintain a direct impact on knowledge for the external firms. Th is paper contributes to the cluster literature a better contextualization an d understanding of the relation between the structural social capital and knowledge acquisition. In addition, paper also contributes to consolidate the inter - organizational approach to social capital theory in order to understand how and in which context t he social capital dimensions are interrelated . Paper analyze s how firms can acquire valuable knowledge from their networks, overcoming the gap of the literature on how this process occurs inside and outside the clusters. Study propose s some recommendations for companies and institutions, and new complementary lines of research

    Estudio comparativo de los parámetros calidad de la leche, características tecnológicas y producción quesera de la Raza Merina de Grazalema frente al cruce con razas foráneas

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    En los últimos años se están incorporando masivamente en España, en general, y en Andalucía, en particular, razas ovinas foráneas de aptitud lechera, fundamentalmente las razas Assaf, Awassi y Lacaune. Su introducción está fomentando, asimismo, la realización de cruces indiscriminados con nuestras razas ovinas autóctonas, de aptitud lechera pero de menor especialización, al menos cuantitativamente (Casas et al., 2005). El objetivo de este estudio ha sido analizar en dos grupos de animales de un mismo rebaño (ovejas puras de raza Merina de Grazalema, y ovejas cruzadas Merina de Grazalema x Awassi) las características de la producción lechera, y proceder a la elaboración de quesos para estudiar las posibles diferencias tecnológicas de los quesos derivados de ambas elaboraciones. A través del mismo se ha comprobado una mayor producción lechera de las ovejas cruzadas (167.35±13.20 kg frente a 136.84±4.25 kg) pero con un porcentaje de grasa (6.25±0.34 % frente a 8.27±0.22 %), proteína (4.71±0.14 % frente a 5.80±0.09 %) y extracto seco (10.97±0.46 % frente a 14.07±0.28 %), estadísticamente inferior. En cuanto a los parámetros de aptitud tecnológica, los valores de tiempo de coagulación medio (24.70±0.77 minutos), dureza media (dureza del coágulo a los 30 minutos) de 25.03±2.27 mm, y el rendimiento en cuajada (327.50±5.70 g/l), mostraron cifras inferiores a las referenciadas por Casas et al. (2005) para la raza ovina Merina de Grazalema. Finalmente, la velocidad de endurecimiento resultó mayor a los valores obtenidos en el trabajo citado anteriormente (4.59±0.54 min.). Por otro lado, estos mismos parámetros mostraron valores inferiores en el tiempo de coagulación (19.60±0.62 minutos), velocidad de endurecimiento (3.97±0.38 min.) y rendimiento en cuajada (290.55±6.67), mientras que la dureza media (32.85±2.03 mm) fue superior en las ovejas cruzadas, respecto a los valores encontrados en esta misma explotación para los animales puros. Como consecuencia de todo ello, el rendimiento quesero real fue del 30.25 % para las ovejas puras frente al 23.70 % de las cruzadas. Esto determina que la producción quesera real que se obtiene por oveja pura, sea superior al de la cruzada (41.38 kg queso fresco/lactación frente a los 39.70 de la cruzada)

    The Spanish economy in EMU : the first ten years

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    This paper has been prepared to mark the tenth anniversary of Economic and Monetary Union (EMU). It seeks to give an overview of the Spanish economy's experience in this new institutional setting. It should be viewed as the result of a joint effort by a sizeable group of researchers from the Banco de España Directorate General Economics, Statistics and Research to rationalise the implications of a structural change on this scale.

    3D effects on transport and plasma control in the TJ-II stellarator

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    The effects of 3D geometry are explored in TJ-II from two relevant points of view: neoclassical transport and modification of stability and dispersion relation of waves. Particle fuelling and impurity transport are studied considering the 3D transport properties, paying attention to both neoclassical transport and other possible mechanisms. The effects of the 3D magnetic topology on stability, confinement and Alfven Eigenmodes properties are also explored, showing the possibility of controlling Alfven modes by modifying the configuration; the onset of modes similar to geodesic acoustic modes are driven by fast electrons or fast ions; and the weak effect of magnetic well on confinement. Finally, we show innovative power exhaust scenarios using liquid metals.This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014-2018 under grant agreement No 633053. The views and opinions expressed herein do not necessarily reflect those of the European Comission. This work has been also funded by the Spanish Ministerio de Economía y Competitividad under Projects ENE2013-48109-P, ENE2013-48679-R, ENE2014-52174-P, ENE2014-58918-R, ENE2014-56517-R, ENE2014-56517-R, ENE2015-64914-C3-1-R, ENE2015-70142-P. Research and data analysis done by Kurchatov team (chapters 2, 3 and 7) were funded by Russian Science Foundation, Project 14-22-00193. The work of AVM was partly supported by the Competitiveness Program of NRNU MEPhI

    Elisidepsin interacts directly with glycosylceramides in the plasma membrane of tumor cells to induce necrotic cell death

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    This is an open access article distributed under the terms of the Creative Commons Attribution License.-- et al.Plasma membrane integrity is essential for cell life. Any major break on it immediately induces the death of the affected cell. Different molecules were described as disrupting this cell structure and thus showing antitumor activity. We have previously defined that elisidepsin (Irvalec®, PM02734) inserts and self-organizes in the plasma membrane of tumor cells, inducing a rapid loss of membrane integrity, cell permeabilization and necrotic death. Here we show that, in sensitive HCT-116 colorectal cells, all these effects are consequence of the interaction of elisidepsin with glycosylceramides in the cell membrane. Of note, an elisidepsin-resistant subline (HCT-116-Irv) presented reduced levels of glycosylceramides and no accumulation of elisidepsin in the plasma membrane. Consequently, drug treatment did not induce the characteristic necrotic cell death. Furthermore, GM95, a mutant derivative from B16 mouse melanoma cells lacking ceramide glucosyltransferase (UGCG) activity and thus the synthesis of glycosylceramides, was also resistant to elisidepsin. Over-expression of UGCG gene in these deficient cells restored glycosylceramides synthesis, rendering them sensitive to elisidepsin, at a similar level than parental B16 cells. These results indicate that glycosylceramides act as membrane targets of elisidepsin, facilitating its insertion in the plasma membrane and the subsequent membrane permeabilization that leads to drug-induced cell death. They also indicate that cell membrane lipids are a plausible target for antineoplastic therapy.Funding: The work of CV, AM and CM was partially supported by Ministerio de Economía y Competitividad (www.mineco.gob.es) [grant numbers SAF2010-14916 and SAF2013-45800-R], and Instituto de Salud Carlos III (www.isciii.es) [grant numbers FIS-RECAVA RD06/0014/0025 and FIS-RIC RD12/0042/0019]. The work of MPL and CG was partially supported by Ministerio de Economía y Competitividad [grant number CTQ 2010-1645]. CM and AM hold FPI and JAE-Predoc (www.csic.es) fellowships, respectively.Peer Reviewe
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