Conocimiento actual de los principios fundamentales de la retracción del hormigón

Not availableLa retracción es, con frecuencia, responsable del agrietamiento del hormigón. Este trabajo resume el estado actual de conocimientos en cuanto a los principios que gobiernan el fenómeno de retracción en el hormigón. La tobermorita es el producto principal de los cementos portland hidratados y es, generalmente, la mayor fuente de retracción por secado en el cemento endurecido. Consecuentemente, la explicación de la retracción por secado se basa en la estructura cristalográfica de la tobermorita, en la naturaleza del agua asociada con ella y en los cambios de volumen que corresponden con los cambios de agua asociada. También se discute brevemente la influencia de otros factores, tales como la composición del cemento, el contenido de árido, la proporción de mezcla y las condiciones de curado

Search for large missing transverse momentum in association with one top-quark in proton-proton collisions at √s = 13 TeV with the ATLAS detector

This paper describes a search for events with one top-quark and large missing transverse momentum in the final state. Data collected during 2015 and 2016 by the ATLAS experiment from 13 TeV proton–proton collisions at the LHC corresponding to an integrated luminosity of 36.1 fb−1 are used. Two channels are considered, depending on the leptonic or the hadronic decays of the W boson from the top quark. The obtained results are interpreted in the context of simplified models for dark-matter production and for the single production of a vector-like T quark. In the absence of significant deviations from the Standard Model background expectation, 95% confidence-level upper limits on the corresponding production cross-sections are obtained and these limits are translated into constraints on the parameter space of the models considered

Search for large missing transverse momentum in association with one top-quark in proton-proton collisions at s√=13 TeV with the ATLAS detector

This paper describes a search for events with one top-quark and large missing transverse momentum in the final state. Data collected during 2015 and 2016 by the ATLAS experiment from 13 TeV proton–proton collisions at the LHC corresponding to an integrated luminosity of 36.1 fb−1 are used. Two channels are considered, depending on the leptonic or the hadronic decays of the W boson from the top quark. The obtained results are interpreted in the context of simplified models for dark-matter production and for the single production of a vector-like T quark. In the absence of significant deviations from the Standard Model background expectation, 95% confidence-level upper limits on the corresponding production cross-sections are obtained and these limits are translated into constraints on the parameter space of the models considered

Characterization of Mo species supported on SiO2 modified with Be2+ and Mg2+

Two series of modified carriers (m.c.) have been prepared by doping silica with various amounts of Be2+ and Mg2+. The prepared m.c. have been used as supports for the preparation of supported Mo((VI)) oxide catalysts. The magnitude of interactions between SiO2 and Be2+ or Mg2+ nitrates depends on the kind and content of the cation. After calcination at 600 degrees C a greater fraction of cations remains on the support surface as well dispersed M(NO2)(2) in the case of Mg2+ m.c. Concerning the Mo containing samples it was found that doping by Be2+ and Mg2+ causes a solid state transformation of octahedral MO(VI) to tetrahedral Mo-(VI). As before, the extent of the effect differs between Be2+ and Mg2+ and it varies with the content of cation. This effect has been attributed to the inhibition of the polymerization of monomeric Mo-(VI) species and/or to the formation of molybdate salts

Disseminated and recurrent infundibular folliculitis (D.R.I.F.): Report of a case successfully treated with isotretinoin

Disseminated and recurrent infundibular folliculitis, henceforth referred to as D.R.I.F., is a very rare, puritic, follicular, benign disease of unknown etiology seen mostly in black males. It is often self-limited and usually unresponsive to local or systemic treatment. How- ever, vitamin A, either alone or combined with vitamin E, is occasionally effective. We report a case of a patient with D.R.I.F. treated successfully with isotretinoin