Suchergebnisse

Among the aims of this work it is included the description of the domains involved in resent scientific papers related with the treatment and the analysis of the ozone layer and with the solar ultraviolet radiation levels (SUVRL). Furthermore, it's emphasized the more important developed strategies to face the analysis and monitoring of the ozone layer; also, Finding the trends in the scientific community association in order to do research into ozone layer. Finally, it's suggested a domain in which Andian countries can construct scientific community for tracking the SUVRL on terrestrial surface. Methodologically, it's searched the trace of the historical scientific criteria which defined the tools and theoretical advance in the present scientific development. It's found that after more than thirty five years, since the global problem announcement, it has been organized a very wide and strong international scientific community with which efforts pointed out and gear up governments and international organizations in order to control anthropogenic substances that emitted to the atmosphere hurt the ozone layer. It has been achieved successfully to reduce emissions of "fist generation substances" in more than 95 %, but since the major part of them will stay in the atmosphere for at least 40 or 50 years, it is necessary to continue with the efforts to enhance the current methods of control and measurement and to develop new precise and economical methods. ; Los propósitos de este trabajo son: a) describir los dominios en los que se centra parte de la literatura científica reciente, relacionada con la evaluación de la columna total de ozono y con los niveles de radiación solar ultravioleta B (RUVB); b) resaltar las más importantes estrategias desarrolladas en el abordaje del análisis y seguimiento de la capa de ozono; c) hallar las tendencias de asociación científica para la investigación de la capa de ozono; d) sugerir el ámbito en el cual los países Andinos pueden formar parte de la comunidad científica que estudia los niveles de la radiación ultravioleta solar en la superficie terrestre. Metodológicamente, se toman los hilos históricos de los criterios científicos que determinaron los avances teóricos e instrumentales que han conducido al nivel de desarrollo científico y tecnológico disponibles en la actualidad. Se encuentra que, después de más de treinta y cinco años de enunciado el problema ambiental de carácter global, se ha formado y organizado una amplia y fuerte comunidad científica internacional que desplegando esfuerzos, ha logrado direccionar y motivar a muchos sectores, desde los más altos niveles de gobierno de las organizaciones internacionales, para controlar sustancias antropogénicas que emitidas a la atmosfera, le hacen daño a la capa de ozono. Se ha logrado reducir las emisiones de las sustancias de primera generación en más de 95 %, pero dado que la mayor parte de ellas permanecerán en la atmosfera por al menos 40 o 50 años, se requiere continuar con los esfuerzos para mejorar los métodos de control y medición existentes y encontrar otros, más precisos, funcionales y económicos.

ELIN (European Languages Virtual Network) is a European Union Lifelong Learning Programme Project aimed at creating an informal social network to support and facilitate languages learning, this social environment is so called MyElvin. This social platform allows a very interesting combination of formal and informal learning activities. The research work behind this project aims to research and develop the connection between social networks, professional profiles and language learning in an informal educational context. At the core of the ELVIN project, there will be a web 2.0 social networking platform, MyElvin that connects employees/students for language practice based on their own professional/academic needs and abilities, using all relevant technologies. This paper presents the first system prototype that integrates social media and content repository.

Abstract. An analysis was made of the Precipitation Concentration Index using the new MOPREDAS database of monthly precipitation in Spain (Monthly Precipitation Data base of Spain). The database was compiled after exhaustive quality control of the complete digitalized Spanish Meterological Agency (AEMet) archives and contains a total set of 2670 complete and homogeneous monthly precipitation series from 1946 to 2005. Thus, MOPREDAS currently holds the densest information available for the 1946–2005 period for Spain and ensures a high resolution of results. The Precipitation Concentration Index (PCI) is a powerful indicator of the temporal distribution of precipitation, traditionally applied at annual scales; as the value increases, the more concentrated the precipitation. Furthermore PCI is a part of the well-known Fournier index, with a long tradition on natural system analyses, as for example soil erosion. In this paper, the mean values of annual, seasonal and wet and dry periods of PCI in the conterminous Spain and for two normal periods (1946–1975 and 1976–2005) were studied. Precipitation in Spain follows a general NW-SE spatial pattern during the wet (months) period due to the Atlantic storm track, while during the dry (months) period, it follows a predominantly N-S spatial pattern. As a result, the annual values of PCI combine the two patterns and show a SW-NE PCI gradient. The analyses of the two sub-periods show significant changes in the precipitation occurred in conterminous Spain from 1946 to 2005, and precipitation concentration increased across most of the IP. At an annual scale, PCI increases mostly due to an increase in precipitation concentration during the wet season. At a seasonal scale significant changes were detected between 1945–1975 and 1976–2005, particularly in autumn (increase of PCI values), while changes in winter, spring and summer were mostly localized and not generalized (both increase and decrease). Changes in PCI seem to be complex and appear to be related to global atmospheric features and synoptic and local factors affecting precipitation trends. We discuss the possible explanation linked to the atmospheric pattern and monthly trends and their implications.

A study on the electronic conduction mechanisms and electrically active defects in polycrystalline Sb2Se3 is presented. It is shown that, for temperatures above 200 K the electrical transport is dominated by thermal emission of free holes, ionized from shallow acceptors, over the inter-grain potential barriers. The temperature dependence of the holes mobility, limited by the inter-grain potential barriers, is the main contributor to the observed conductivity thermal activation energy. At lower temperatures, nearest-neigbour and Mott variable range hopping transport in the bulk of the grains are the dominant conduction mechanisms. Based on this study, the important parameters of the electronic structure of the Sb2Se3 thin-film such as free hole density and mobility, inter-grain potential barrier height, intergrain trap density, shallow acceptor ionization energy, acceptor density, net donor density 2 and compensation ratio are reported. ; P. M. P. Salomé acknowledges the funding of Fundacão para Ciência e Tecnologia (FCT) through the project IF/00133/2015. This research is supported by Development of novel ultrathin solar cell architectures for low-light, low-cost and flexible opto-electronic devices project (028075) co-funded by FCT and ERDF through COMPETE2020. B. Vermang has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement n 715027). A. Shongalova acknowledges the funding of Erasmus + program 2016/17. This work was funded by FEDER funds through the COMPETE 2020 Programme and by FCT -Portuguese Foundation for Science and Technology under the projects UID/CTM/50025/2013. The financial support from Brazilian funding agencies CNPq, CAPES and FAPEMIG is also acknowledged.

A study of the electronic conduction mechanisms and electrically active defects in polycrystalline Sb2Se3 is presented. It is shown that for temperatures above 200 K, the electrical transport is dominated by thermal emission of free holes, ionized from shallow acceptors, over the intergrain potential barriers. In this temperature range, the temperature dependence of the mobility of holes, limited by the intergrain potential barriers, is the main contributor to the observed thermal activation energy of the conductivity of 485 meV. However, at lower temperatures, nearest-neighbor and Mott variable range hopping transport in the bulk of the grains turn into the dominant conduction mechanisms. Important parameters of the electronic structure of the Sb2Se3 thin film such as the average intergrain potential barrier height ϕ = 391 meV, the intergrain trap density Nt = 3.4 × 1011 cm−2, the shallow acceptor ionization energy EA0 = 124 meV, the acceptor density NA = 1 × 1017 cm−3, the net donor density ND = 8.3 × 1016 cm−3, and the compensation ratio k = 0, 79 were determined from the analysis of these measurements. ; P. M. P. Salomé acknowledges the funding of Fundação para Ciencêa e Tecnologia (FCT) through the project IF/00133/ ̂2015. This research is supported by the Development of novel ultrathin solar cell architectures for low-light, low-cost, and flexible optoelectronic devices project (028075) co-funded by FCT and ERDF through COMPETE2020. B. Vermang has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (grant agreement no. 715027). A. Shongalova acknowledges the funding of Erasmus + program 2016/17. This work was funded by FEDER funds through the COMPETE 2020 Programme and by FCTPortuguese Foundation for Science and Technology under the projects UID/CTM/50025/2013. The financial support from Brazilian funding agencies CNPq, CAPES, and FAPEMIG is also acknowledged. ; info:eu-repo/semantics/publishedVersion