1,627 research outputs found

    Combined grazing incidence RBS and TEM analysis of luminescent nano-SiGe/SiO2 multilayers.

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    Multilayer structures with five periods of amorphous SiGe nanoparticles/SiO2 layers with different thickness were deposited by Low Pressure Chemical Vapor Deposition and annealed to crystallize the SiGe nanoparticles. The use of grazing incidence RBS was necessary to obtain sufficient depth resolution to separate the signals arising from the individual layers only a few nm thick. The average size and areal density of the embedded SiGe nanoparticles as well as the oxide interlayer thickness were determined from the RBS spectra. Details of eventual composition changes and diffusion processes caused by the annealing processes were also studied. Transmission Electron Microscopy was used to obtain complementary information on the structural parameters of the samples in order to check the information yielded by RBS. The study revealed that annealing at 900 °C for 60 s, enough to crystallize the SiGe nanoparticles, leaves the structure unaltered if the interlayer thickness is around 15 nm or higher

    Repercusión de los resultados electorales europeos de 2014 en la cobertura mediática de podemos

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    Los resultados de las elecciones al Parlamento Europeo de 2014 introducen nuevos actores en el tablero político. El objetivo de este trabajo es analizar las noticias publicadas sobre Podemos en los medios digitales españoles, con el fin de establecer la influencia de los resultados electorales en la agenda mediática. Aplicamos una combinación de técnicas cualitativas y cuantitativas para identificar el marco temático, los protagonistas y las caracterizaciones utilizadas en la cobertura informativa. Los resultados del estudio muestran que, generalmente, las diferencias en el tratamiento informativo se deben a motivos ideológicos y revelan coincidencias en las estrategias de viejos y nuevos medios digitales. No obstante, mientras los medios pertenecientes a grupos de comunicación siguen una línea más favorable a los grandes partidos, los medios sin vinculaciones empresariales realizan una cobertura sobre Podemos más numerosa y neutral

    Nanoporous PMMA: A novel system with different acoustic properties

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    The acoustic properties of closed cell nanoporous and microporous poly(methyl methacrylate) (PMMA) foams have been well characterized, showing that nanoporous PMMA exhibit a different absorption coefficient and transmission loss behavior in comparison with microporous PMMA. Experimental differences may be explained by the different wave propagation mechanism in the micro and nanoscale, which is determined by the confinement of both the gas (Knudsen regime) and the solid phases. These results place nanoporous materials as a new class of polymeric porous material with potential properties in the field of acoustics, especially in multifunctional systems requiring a certain degree of soundproofing

    La visita de cuevas como recurso didáctico para la enseñanza de la procesos endokársticos. Las cuevas de Noceda (O Courel, Lugo, No de España)

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    Se diseña una propuesta docente didáctica para la asignatura de Geología de 2º de Bachillerato de España, en la que se pretende favorecer el aprendizaje de los contenidos relativos al karst y al trabajo de campo en Geología. La propuesta comprende la visita al interior de las cuevas kársticas y trabajo de campo con el fin de identificar ocho elementos básicos: conducto freático, conducto vadoso, espeleotemas, depósitosfluviales, derrubios, surgencia kárstica, río subterráneo y sifón. Estos elementos permiten reconocer los procesos formadores de las cuevas: disolución química, sedimentación fluvial, desprendimientos rocosos y la precipitación de espeleotemas, en relación a la circulación subterránea del agua. Para ilustrarlo, se han definido siete puntos de interés en dos cuevas kársticas de acceso relativamente sencillo. Esta propuesta permitirá al estudiante conocer los relieves kársticos y cómo se originan y se desarrollan las cuevas, así como comprender cómo circula el agua en el karst. Finalmente, se propone un sistema de evaluación que combina la evaluación del profesor, coevaluación entre iguales y autoevaluación de la actividad y de un informe elaborado por los estudiantes mediante trabajo cooperativo, a partir de las observaciones de campo recogidas en un cuadern

    Individualization and Electrical Characterization of SiGe Nanowires

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    SiGe nanowires of different Ge atomic fractions up to 15% were grown and ex-situ n-type doped by diffusion from a solid source in contact with the sample. The phenomenon of dielectrophoresis was used to locate single nanowires between pairs of electrodes in order to carry out electrical measurements. The measured resistance of the as-grown nanowires is very high, but it decreases more than three orders of magnitude upon doping, indicating that the doping procedure used has been effectiv

    SiGe nanowires grown by LPCVD using Ga-Au catalysts

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    The use of Ga-Au alloys as metal catalysts for the growth of SiGe nanowires has been investigated. The grown nanowires are cylindrical and straight, with a defect-free crystalline structure, sharp nanowire-droplet interfaces and an almost constant Ge atomic fraction throughout all their length. These features represent significant improvements over the results obtained using pure A

    Description of the CLISSA application: climatology module for semi-automatic and automatic systems

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    Comunicación presentada en: 3ª Conferencia Internacional sobre Experiencias con Estaciones Meteorológicas Automáticas celebrada en 2003 en Torremolinos, Málaga.This software has been developed for the purpose of processing incoming data from the main climatological stations according to the current standards in force at the Spanish National Meteorology Institute (INM) and for the progressive replacement of traditional observation systems through automatic stations, in addition to providing support for climatological elements such as cloudiness, evaporation in Piche evaporimeter, etc., and weather phenomena (storm, dew, mist, dust clouds,...), not susceptible to automation as yet

    SiGe/Si nanowire axial heterostructures grown by LPCVD using Ga-Au

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    The use of Ga-Au alloys of different compositions as metal catalysts for the growth of abrupt SiGe/Si nanowire axial heterostructures has been investigated. The heterostructures grown in a continuous process by just switching the gas precursors, show uniform nanowire diameters, almost abrupt compositional changes and no defects between the different sections. These features represent significant improvements over the results obtained using pure Au

    Macroalgal- dominated coastal detritic communities from the Western Mediterranean and the Northeastern Atlantic

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    20 páginas, 6 tablas, 5 figuras, 1 apéndice.This is a qualitative comparison of the distribution of macroalgal-dominated coastal detritic communities from the Western Mediterranean and the Northeastern Atlantic, based on our own data from the Balearic Islands (Western Mediterranean) and available data from the literature. The macroalgal-dominated coastal detritic bottoms in both regions can be distinguished by the presence of a high number of regional exclusive non-carbonated species, and the presence of a high number of maërl-forming species in the Mediterranean. Furthermore, regional differences in the distribution of some exclusive species allowed the distinction of three zones in the Northeastern Atlantic (United Kingdom, French Brittany and Galicia), while no differences were found in the Western Mediterranean. However, the algal communities considered in the selected literature could not be qualitatively distinguished, and all the samples should be considered as maërl beds. Lithothamnion corallioides and Phymatolithon calcareum were the most widespread maërl forming species in the two regions, while in the Western Mediterranean Spongites fruticulosus was also very frequent. According to the differences in the species composition of the basal and erect strata of these beds, and also in their species richness, five different morphologies of macroalgal-dominated detritic bottoms can be distinguished. Their main characteristic species and their biogeographic distribution are detailed.The CANAL0209 survey was financed by the MarViva Foundation, the Govern de les Illes Balears and the IEO. The MEDITS_ES05_09 survey was supported by the BADEMECO project, financed by the IEO and the European Union.Peer reviewe
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