Contexto estructural y paleogeográfico de los sistemas lacustres cenozoicos de España.

La evolución de los sistemas lacustres cenozoicos en España estuvo claramente influida por: l) la edificación de los orógenos pirenaico y bético y la intensa deformación interna que afectó la microplaca de Iberia. 2) l0s cambios de las condiciones paleogeogrlficas y paleoclimáticas generales que afectaron la región mediterránea occidental-atlántica oriental en la que se localizaba Iberia. Potentes sucesiones de carbonatos y evaporitas lacustres han sido reconocidas en la mayor parte de las cuencas cenozoicas españolas. Junto a estos depósitos se registra la presencia de otros menos frecuentes (carbón, devósitos bituminosos, diatomitas, arcillas especiales) también significativos desde un punto de vista geolimnolÓgico e interesantes desde una perspectiva económica. Los mayores y mis persistentes sistemas lacustres se ubicaron en las cuencas de antepaís, arealmente muy extensas. Los de menor entidad y mis corta evolución se formaron en cuencas limitadas por fallas de distintos tipos. En ambos casos los sistemas lacustres evolucionaron en estrecharelacióncon sistemas aiuviales y sus características hidroquírnicas estuvieron muy influidas por el reciclaje de depósitos de carbonatos, sulfatos y cloruros, fundamentalmente de edad mesozoica. Este reciclaje influyó tanto en la litologia de las sucesiones lacustres resultantes como sobre las caracteristicas de las asociaciones de organismos limnicos que se desarrollaron en los sistemas lacustres

Constructing Fresnel reflection coefficients by ruler and compass

A simple and intuitive geometical method to analyze Fresnel formulas is presented. It applies to transparent media and is valid for perpendicular and parallel polarizations. The approach gives a graphical characterization particularly simple of the critical and Brewster angles. It also provides an interpretation of the relation between the reflection coefficients for both basic polarizations as a symmetry in the plane

Microtubular SOFC based on an extruded support

Trabajo presentado al "IV Iberian Symposium on Hydrogen, Fuel Cells and Advanced Batteries" celebrado en Estoril (Portugal) del 26 al 28 de junio de 2013.In this work the processing route for an anode supported microtubular solid oxide fuel cell is adjusted. The fuel cell composition and microstructure design is based on previous work. In this work we have developed microtubular cells based on an extruded support. Firstly, Ni-YSZ anode was manufactured by Powder Extrusion Moulding (PEM). Feedstock composition and extruding parameters were adjusted to obtain tubular green bodies. An YSZ layer was then deposited as the electrolyte and the sintering parameters were optimized to obtain a dense layer. An active area of ~1 cm2 LSMYSZ was deposited as the cathode and its electrochemical performance was measured using pure hydrogen as fuel, yielding a power output at 0.5V of 0.7Wcm-2 at 8500C.Authors would like to thank financial support received from MICINN and Feder program of the European Community (MAT2010-19837-C06 and MAT2012-30763 projects), Madrid regional government (MATERYENER S2009 PPQ-1626 program), and also grant GA-LC-035/2012, financed by the Aragón Government and La Caixa Foundation.Peer Reviewe

High-performance Ni-YSZ thin-walled microtubes for anode-supported solid oxide fuel cells obtained by powder extrusion moulding

Aiming at the fabrication of microtubular anode-supports for Solid Oxide Fuel Cell (SOFC) applications, this contribution deals with the production of Ni-YSZ thin-walled tubes (<1 mm thickness) via Powder Extrusion Moulding (PEM). The overall method has been optimized with an emphasis on the effect of NiO particle size using two commercial NiO powders with mean sizes of 0.7 and 8 μm. A thermoplastic binder system based on polypropylene (PP), paraffin wax (PW) and stearic acid (SA) in volume ratios of 50, 46 and 4, respectively, was used along with corn starch as a pore forming agent. Different feedstocks with solid loadings varying from 45 to 65 vol% were processed and characterized to determine the optimal formulation. Typically, the mixtures exhibited a pseudoplastic behaviour from 100 to 1000 s. Feedstocks with finer NiO particles had the most balanced properties for PEM purposes and an optimal powder volume content of 65 vol% was established. After extrusion and debinding steps, defect-free and constant cross-section tubes with 15 mm of length and 4 mm of nominal diameter were obtained. The final microstructure and DC conductivity were found to be closely linked to the NiO particle size, yielding a higher degree of open porosity and a better performance when using finer NiO powder. Based on this study, the packing mechanism was found to be likely limited by the contribution of steric hindrances when dissimilar and coarse powders are mixed, which may play a decisive role in order to set tailored formulations.Authors would like to thank financial support received from MICINN and Feder program of the European Community (MAT2013-46452-C4-3R and MAT2012-30763 projects), and Madrid regional government (MATERYENER3CM S2013/MIT-2753 Program).Peer Reviewe

Integrated multi-stratigraphic study of the Coll de Terrers late Permian-Early Triassic continental succession from the Catalan Pyrenees (NE Iberian Peninsula): A geologic reference record for equatorial Pangaea

The most severe biotic crisis on Earth history occurred during the Permian-Triassic (PT) transition around 252 Ma. Whereas in the marine realm such extinction event is well-constrained, in terrestrial settings it is still poorly known, mainly due to the lack of suitable complete sections. This is utterly the case along the Western Tethys region, located at Pangaea's equator, where terrestrial successions are typically build-up of red beds often characterised by a significant erosive gap at the base of the Triassic strata. Henceforth, documenting potentially complete terrestrial successions along the PT transition becomes fundamental. Here, we document the exceptional Coll de Terrers area from the Catalan Pyrenees (NE Iberian Peninsula), for which a multidisciplinary research is conducted along the PT transition. The red-bed succession, located in a long E-W extended narrow rift system known as Pyrenean Basin, resulted from a continuous sedimentary deposition evolving from meandering (lower Upper Red Unit) to playa-lake/ephemeral lacustrine (upper Upper Red Unit) and again to meandering settings (Buntsandstein facies). Sedimentary continuity is suggested by preliminary cyclostratigraphic analysis that warrants further analysis. Our combined sedimentological, mineralogical and geochemical data infer a humid-semiarid-humid climatic trend across the studied succession. The uppermost Permian strata, deposited under an orbitally controlled monsoonal regime, yields a relatively diverse ichnoassemblage mainly composed of tetrapod footprints and arthropod trace fossils. Such fossils indicate appropriate life conditions and water presence in levels that also display desiccation structures. These levels alternate with barren intervals formed under dry conditions, being thus indicative of strong seasonality. All these features are correlated with those reported elsewhere in Gondwana and Laurasia, and suggest that the Permian-Triassic boundary might be recorded somewhere around the Buntsandstein base. Consequently, Coll de Terrers and the whole Catalan Pyrenees become key regions to investigate in detail the Permian extinction event and the Triassic ecosystems recovery

Mechanical and microstructural features of wire-and-arc additively manufactured carbon steel thick plates

Metal additive manufacturing (AM), in particular wire-and-arc additive manufacturing (WAAM), has become over the last few years the breakthrough technology to reduce the environmental impact and increase the efficiency of steel structures. Although intense research effort has been paid toward the mechanical characterization of WAAM-produced thin walls, little attention has been devoted to the investigation of multi-layered thick parts. These latter would indeed expand the application of WAAM for large-scale constructions requiring thicker cross-sections to withstand high loading conditions. The present work provides a comprehensive experimental investigation of mild steel WAAM thick plates from the fabrication to the mechanical and microstructural characterization. First, the fabrication process is presented in full details. From that, microstructural and mechanical characterization is described and discussed, showing a homogeneous microstructure with little influence on the mechanical response along the wall plate thickness, also considering different specimen orientations with respect to the printing directions. The results confirm good mechanical properties of the printed outcomes, in line with those of structural mild steels manufactured with conventional technologies. Little influence on the response along the thickness is reported, thus proving the required quality of WAAM thick parts for applications in the construction sector