Size and dimensionality effects in superconducting Mo thin films

Molybdenum is a low Tc, type I superconductor whose fundamental properties are poorly known. Its importance as an essential constituent of new high performance radiation detectors, the so-called transition edge sensors (TESs) calls for better characterization of this superconductor, especially in thin film form. Here we report on a study of the basic superconducting features of Mo thin films as a function of their thickness. The resistivity is found to rise and the critical temperature decreases on decreasing film thickness, as expected. More relevant, the critical fields along and perpendicular to the film plane are markedly different, thickness dependent and much larger than the thermodynamic critical field of Mo bulk. These results are consistent with a picture of type II 2D superconducting films, and allow estimates of the fundamental superconducting lengths of Mo. The role of morphology in determining the 2D and type II character of the otherwise type I molybdenum is discussed. The possible consequences of this behaviour on the performance of radiation detectors are also addressed

Folletos varios de apologética españolista

Contiene: La cuestión de la buena prensa / Francisco Mª. Cruz._ 4ª ed. Los carlo-traidores : llaves / por C.M. Apsmav y el Dr. Leal._ 2ª ed. / Los carlo-traidores : memoria póstuma del General D. Salvador Soliva, con abundantes notas y documentos / por C.M. Apsmav y el Dr. Leal._ 2ª ed. Los carlo-traidores : los vendidos / por C.M. Apsmav y el Dr. Leal. El espíritu del carlismo / por Don O.L.H.P. La verdad acerca de una desautorización : artículos extractados del número 4 de "Tradición y Progreso"

Mechanical characterization of GdBCO/Ag and YBCO single grains fabricated by top-seeded melt growth at 77 and 300 K

YBaCuO and GdBaCuO + 15 wt% Ag large, single-grain, bulk superconductors have been fabricated via the top-seeded, melt-growth (TSMG) process using a generic NdBCO seed. The mechanical behavior of both materials has been investigated by means of three-point bending (TPB) and transversal tensile tests at 77 and 300 K. The strength, fracture toughness and hardness of the samples were studied for two directions of applied load to obtain comprehensive information about the effect of microstructural anisotropy on the macroscopic and microscopic mechanical properties of these technologically important materials. Splitting (Brazilian) tests were carried out on as-melt-processed cylindrical samples following a standard oxygenation process and with the load applied parallel to the growth-facet lines characteristic of the TSMG process. In addition, the elastic modulus of each material was measured by three different techniques and related to the microstructure of each sample using optical microscopy. The results show that both the mechanical properties and the elastic modulus of both YBCO and GdBCP/Ag are improved at 77 K. However, the GdBCO/Ag samples are less anisotropic and exhibit better mechanical behavior due to the presence of silver particles in the bulk, superconducting matrix. The splitting tensile strength was determined at 77 K and both materials were found to exhibit similar behavior, independently of their differences in microstructure.

Vortex pinning vs superconducting wire network: origin of periodic oscillations induced by applied magnetic fields in superconducting films with arrays of nanomagnets

Hybrid magnetic arrays embedded in superconducting films are ideal systems to study the competition between different physical (such as the coherence length) and structural length scales such as are available in artificially produced structures. This interplay leads to oscillation in many magnetically dependent superconducting properties such as the critical currents, resistivity and magnetization. These effects are generally analyzed using two distinct models based on vortex pinning or wire network. In this work, we show that for magnetic dot arrays, as opposed to antidot (i.e. holes) arrays, vortex pinning is the main mechanism for field induced oscillations in resistance R(H), critical current Ic(H), magnetization M(H) and ac-susceptibility χ ac(H) in a broad temperature range. Due to the coherence length divergence at Tc, a crossover to wire network behaviour is experimentally found. While pinning occurs in a wide temperature range up to Tc, wire network behaviour is only present in a very narrow temperature window close to Tc. In this temperature interval, contributions from both mechanisms are operational but can be experimentally distinguished.

La arquitectura negra en la comarca del Ocejón (Guadalajara)

Las numerosas muestras de la construcción tradicional que se han conservado en distintas localidades de la Sierra de Ayllón (especialmente en la provincia de Guadalajara, pero también en las limítrofes de Madrid y de Segovia) y que reciben el nombre de arquitectura negra por el uso predominante de la pizarra como material de construcción, forman uno de los conjuntos más singulares dentro de la arquitectura popular española. Estas formas, materiales y sistemas tradicionales de construir –que se extienden, con pequeñas diferencias, tanto en la vertiente occidental como en el área oriental del pico Ocejón (que con sus 2048 m es el de mayor altura de la provincia de Guadalajara y la referencia geográfica indiscutible de este grupo de localidades)– constituyen uno de los elementos más importantes y reconocibles del paisaje serrano del Ma- cizo de Ayllón y nos permiten comprender y aproximarnos, a través de sus numerosos valores, al soporte ambiental, social, económico y cultural que las hizo posibles.

COMUNICAR PARA MUDAR: Estudo das metodologias de desenvolvimento de comunidade e da comunicação para o desenvolvimento e para a mudança social

Estudo sobre as metodologias de comunicação nas propostas de desenvolvimento comunitário. Com base em pesquisa bibliográfica o trabalho objetivou evidenciar os aspectos explícitos e implícitos da comunicação presentes nas metodologias de desenvolvimento de comunidade publicadas no Brasil. Para tal, foi realizada ampla revisão da literatura sobre os conceitos de comunidade, desenvolvimento, pobreza e participação, metodologias de desenvolvimento de comunidade, comunicação para o desenvolvimento e comunicação para a mudança social. Ao final, a pesquisa evidenciou que os conceitos de desenvolvimento e de participação invariavelmente constituem o fundamento a partir dos quais se erigem tanto projetos de desenvolvimento comunitário como de comunicação para o desenvolvimento/mudança social. Um modelo de desenvolvimento necessariamente leva a um modelo de participação, e viceversa, que, em projetos de melhoria das condições de vida comunitária se constituem como elementos catalisadores das demais instâncias do trabalho. Ambas propostas apresentam muitos pontos em comum e diversos espaços para contribuições recíprocas.(AU)