Influencia de la microestructura en las propiedades mecánicas de alta temperatura de los Eutécticos Al2O3/Y3Al5O12 crecidos por solidificación direccional

En este trabajo se ha realizado un estudio del sistema eutéctico Al2O3/Y3Al5O12 crecido a distintas velocidades mediante solidificación direccional de zona flotante por calentamiento con láser. El análisis microestructural se ha realizado mediante Microscopía Electrónica de Barrido (MEB) y de Transmisión (MET), tanto en muestras tras el procesado con láser como en muestras sometidas a los distintos tratamientos termo-mecánicos. El estudio de las propiedades mecánicas se ha llevado a cabo mediante ensayos a velocidad de deformación constante y ensayos de fluencia -a carga de compresión constante- para diversos valores de tensión y de temperatura en atmósfera de aire. De los resultados obtenidos se deduce que la resistencia está íntimamente asociada a la microestructura de las muestras, la cual depende de la velocidad de solidificación. La presencia de dislocaciones es clara a altas velocidades de deformación, observándose los mecanismos activos de deformación típicos de la alúmina monocristalinas, como son la formación de bucles de dislocaciones para evitar obstáculos. Los valores de los exponentes de tensión y la energía de activación sugieren un comportamiento difusional para bajas velocidades de deformación, a las que no se observan dislocaciones.The Al2O3/Y3Al5O12 eutectic system melt grown by laser heating float zone in a range of pull rates has been studied. The microstructural analysis has been made by Scaning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) in as-fabricated and tested samples. The mechanical properties have been studied by compression tests at constant crosshead speed and compression creep for a range of stresses and temperatures in air. It has been determined that the resistance is intimately associated to processing. The presence of dislocations is clear after plastic deformation at high strain rates, being active the typical deformation mechanisms of alumina single crystals, like dislocation loop formation to avoid obstacles. The values of the stress exponents and the activation energy suggest a diffusional control for plastic deformation at low strain rates, where dislocations are not observed

Electromagnetic field enhancement effects in group IV semiconductor nanowires. A Raman spectroscopy approach

Semiconductor nanowires (NWs) are the building blocks of future nanoelectronic devices. Furthermore, their large refractive index and reduced dimension make them suitable for nanophotonics. The study of the interaction between nanowires and visible light reveals resonances that promise light absorption/scattering engineering for photonic applications. Micro-Raman spectroscopy has been used as a characterization tool for semiconductor nanowires. The light/nanowire interaction can be experimentally assessed through the micro-Raman spectra of individual nanowires. As compared to both metallic and dielectric nanowires, semiconductor nanowires add additional tools for photon engineering. In particular, one can grow heterostructured nanowires, both axial and radial, and also one could modulate the doping level and the surface condition among other factors than can affect the light/NW interaction. We present herein a study of the optical response of group IV semiconductor nanowires to visible photons. The study is experimentally carried out through micro-Raman spectroscopy of different group IV nanowires, both homogeneous and axially heterostructured (SiGe/Si). The results are analyzed in terms of the electromagnetic modelling of the light/nanowire interaction using finite element methods. The presence of axial heterostructures is shown to produce electromagnetic resonances promising new photon engineering capabilities of semiconductor nanowires.Junta de Castilla y Le on (Projects VA293U13 and VA081U16) and Spanish Government (CICYT MAT2010-20441-C02 (01 and 02) and ENE 2014-56069-C4-4-R). J. L. Pura was granted by the FPU programme (Spanish Government) (FPU14/00916)

Evaluación multidisciplinar 3D de una estructura kárstica asociada a colapso y subsidencia (Cuenca del Ebro)

La propagación de cavidades de disolución localizadas por debajo de series aluviales genera una serie de evidencias cuya representación superficial, en ocasiones, puede no ser indicativa de su extensión real en profundidad. La propagación de cavidades a través de medios heterogéneos, en los que pueden existir niveles cementados, puede producir cambios en la progresión de dichas cavidades y la identificación en superficie de grietas, colapsos, o zonas de subsidencia que pueden involucrar decenas de miles de metros cúbicos de material inestable. Cualquier tipo de evaluación de soluciones mitigadoras en estos contextos debe considerar la amplitud de estos volúmenes y el origen del proceso con independencia de la actividad registrada en superficie. En este trabajo se aborda un estudio integrado con el objetivo de determinar la estructura de un sector con evidencias de actividad kárstica superficial y evaluar su extensión y desarrollo tridimensional integrando el análisis geomorfológico, de inspección de campo, geofísica (GPR) y sondeos. The propagation of solution cavities located below alluvial deposits produce surficial evidences that, in some cases, cannot be representative of their actual extension at depth. Cavity propagation through heterogeneous media, for example with interbedded cemented levels, can produce changes in the propagation of deformation producing the identification of cracks, collapses or subsidence zones at the surface. These processes can involve thousands of cubic meters of unstable materials. Any evaluation of mitigation tasks, in this context, needs to consider: i) the amplitude of the affected volumes and ii) the in depth origin with independence of the surficial recorded activity In this work an integrated analysis is developed to evaluate the size and 3D structure of a sector with surficial evidences of karstic activity integrating geomorphological analysis, field inspection, geophysics (GPR) and boreholes

Extracciones quimicas secuenciales de metales pesados. Aplicacion en ciencias geologicas

Sequential chemical extraction methodologies are applied in Geological Sciences with the objective of determining the solid speciation for trace metals present in soil, sediment and rock samples. Such information is not available from a conventional chemica1 analysis. At the present time a wide variety of sequential protocols exists, but none of them has been imposed as an international standard method as yet. The fractions of solid material that these protocols usually allow to distinguish are the following: Exchangeable, carbonate, Fe-Mn oxide-hydroxide, organic, and residual. Different methods differ in the used reagents as well as in the experimental conditions, depending on the particular objectives. Sequential extraction methods are used in different fields of geological sciences, mainly in environmental geochemistry of aquatic systems (rivers, lakes, estuaries), edaphology and also in groundwater hydrology. In general, sequential extraction protocols involve important methodological problems which have been pointed out for severa1 authors. Among these problems are the following: Reagent selectivity, operative definition of methods, elemental redistribution (or readsorption), variable experimental conditions, scarcity of reference solid certificated materials, strong difficulty in order to validate the existing methods, and the evaluation of its precision. In spite of al1 methodological problems mentioned, at the present time sequential extraction protocols constitute the better approach in order to describe the geochemical association of trace elements with different fractions of solid materials.Las metodologías de extracción química secuencial se aplican en Geología con el objetivo de determinar la especiación de los metales traza en suelos, sedimentos o rocas, información que no se puede conseguir a partir únicamente de un análisis químico convencional sobre muestra total. En la actualidad existe una amplia variedad de protocolos de extracción secuencial diferentes, sin haberse impuesto todavía uno de ellos como un método estándar plenamente aceptado. Las fracciones de metales pesados que comúnmente se suelen diferenciar en los sólidos mediante este tipo de metodologías son: intercambiable, asociada a carbonatos, asociada a óxidos Fe y Mn, asociada a materia orgánica y fracción residual. Los distintos protocolos existentes difieren en los reactivos empleados y también en las condiciones experimentales, todo ello dependiendo de los objetivos concretos del estudio a realizar. Las extracciones secuenciales han encontrado unos campos de aplicación muy amplios en las ciencias geológicas, sobre todo en los estudios de geoquímica ambiental en medios acuáticos (ríos, lagos, estuarios), en edafología y también en hidrología subterránea. Los protocolos de extracción secuencial adolecen, en conjunto, de una serie de problemas metodológicos de cierta envergadura y que han sido abordados por distintos autores, pudiendo destacar entre ellos la selectividad de los reactivos empleados, la propia definición operativa de estos métodos, la redistribución (o readsorción) elemental, las condiciones experimentales bajo las que se pueden ejecutar los protocolos, la escasez de materiales sólidos de referencia y, derivados de este último problema, la dificultad de validación de los distintos métodos y la evaluación de su precisión. A pesar de todos estos inconvenientes metodológicos, los procedimientos de extracción secuencial constituyen en la actualidad la mejor aproximación para describir la asociación geoquímica de los elementos traza con las diferentes fracciones de los sólidos

Assessment of Tremor Severity in Patients with Essential Tremor Using Smartwatches

[Abstract] This paper presents a classification model for the automatic quantification of tremor severity in patients with essential tremor (ET). The system is based on the signals measured by two commercial smartwatches that the patients wear on their wrist and ankle. The smartwatches register acceleration and angular velocity in these body segments. A set of nine tremor features were used to train the classification algorithm. The proposed algorithm is based on a C4.5 decision tree classifier. It is able to assess rest and kinetic (postural or action) tremor. The method was evaluated using data collected from thirty-four patients with ET. The algorithm classifies the severity of tremor in five levels 0-4 corresponding to those in the Fahn-Tolosa-Marin tremor rating scale with a 94% accuracy. The method can be implemented in a networked platform for the remote monitoring and assessment of movement disorders such as ET or Parkinson’s disease.Ministerio de Economía, Industria u Competitividad; RTC-2015-3967-1Ministerio de Economía, Industria u Competitividad; DPI2015-68664-C4-1-RMinisterio de Economía, Industria u Competitividad; RTC-2015-4327-

Endotoxin-induced lung alveolar cell injury causes brain cell damage

Instituto de Salud Carlos III (ISCIII

Estudio de la citotoxicidad de cerámicas biomórficas de SiC recubiertas con vidrio bioactivo

La necesidad de desarrollar nuevos implantes basados en materiales bioactivos que sean capaces de soportar grandes cargas mecánicas ha llevado a la producción de sustratos metálicos recubiertos con cerámicas bioactivas. Recientemente se ha propuesto un dispositivo alternativo que consiste en un sustrato de carburo de silicio (SiC) biomórfico recubierto con vidrio bioactivo, mediante la técnica de Depósito por Láser Pulsado (PLD), y que dispone de la resistencia mecánica adecuada, además de gran ligereza y una porosidad intrínseca muy favorable de cara a la implantación. En este trabajo se presenta un estudio interdisciplinar de este nuevo material centrado en la morfología y porosidad de sustratos de SiC provenientes de diferentes maderas, la bioactividad de los recubrimientos producidos por PLD y en la evaluación in vitro con células de osteosarcoma MG-63 con la que se ha determinado la citotoxicidad de estos materiales y se ha estudiado la influencia de los mismos en la adhesión y la proliferación celular.In the past years there was a need to develop new tough bioactive materials capable to resist high loads when implanted in the body, that led to the production of bioactive coatings on metallic substrates. A new approach, which consists of biomorphic silicon carbide (SiC) coated with bioactive glass by Pulsed Laser Deposition (PLD), was recently presented. This new material joins the high mechanical strength, lightness and porosity of biomorphic SiC and the bioactive properties of PLD glass films. In this work, a multiple evaluation of this new material is presented starting from the biomorphic SiC morphology and porosity, following with the bioactivity in simulated body fluid of the coatings, and ending with a deep in vitro study with MG-63 cells. The citotoxicity of the SiC coated and uncoated and the cell proliferation and attachment were studied

Extensive studies on biomorphic SiC ceramics properties for medical applications

Biomorphic silicon carbide ceramics are light, tough and high-strength materials with interesting biomedical applications. The fabrication method of the biomorphic SiC is based in the infiltration of molten-Si in carbon preforms with open porosity. The final product is a biostructure formed by a tangle of SiC fibers. This innovative process allows the fabrication of complex shapes and the tailoring of SiC ceramics with optimised properties and controllable microstructures that will match the biomechanical requirements of the natural host tissue. An interdisciplinary approach of the biomorphic SiC fabricated from beech, sapelly and eucalyptus is presented. Their mechanical properties, microstructure and chemical composition were evaluated. The biocompatible behaviour of these materials has been tested in vitro

Cardiovascular Magnetic Resonance Imaging Evidence of Edema in Chronic Chagasic Cardiomyopathy

The persistence of inflammatory processes in the myocardium in varying degrees of chronic Chagas heart disease has been poorly investigated. We hypothesized that edema could occur in patients with chronic chagasic cardiomyopathy and corresponds to the persistence of inflammatory processes in the myocardium. Eighty-two Chagas disease (CD) seropositive patients (64.6% females; age = 58.9 ± 9.9) without ischemic heart disease or conditions that cause myocardial fibrosis and dilation were considered. Late gadolinium enhancement (LGE) and T2-weighted magnetic resonance imaging of edema were obtained and represented using a 17-segment model. Patients were divided into three clinical groups according to the left ventricular (LV) ejection fraction (EF) as G1 (EF > 60%; ), G2 (35% > EF  35% (). Deteriorations of the LV and RV systolic functions were positively correlated (; ) without evidence of LGE in the RV. Edema can be found in patients with chagasic cardiomyopathy in the chronic stage. In later stages of cardiac dilation with low LVEF, the LGE pattern involves subendocardium and mid locations. Deteriorations of RV and LV are positively correlated without evidence of fibrosis in the RV

Transport Properties of Random Walks on Scale-Free/Regular-Lattice Hybrid Networks

We study numerically the mean access times for random walks on hybrid disordered structures formed by embedding scale-free networks into regular lattices, considering different transition rates for steps across lattice bonds ($F$) and across network shortcuts ($f$). For fast shortcuts ($f/F\gg 1$) and low shortcut densities, traversal time data collapse onto an universal curve, while a crossover behavior that can be related to the percolation threshold of the scale-free network component is identified at higher shortcut densities, in analogy to similar observations reported recently in Newman-Watts small-world networks. Furthermore, we observe that random walk traversal times are larger for networks with a higher degree of inhomogeneity in their shortcut distribution, and we discuss access time distributions as functions of the initial and final node degrees. These findings are relevant, in particular, when considering the optimization of existing information networks by the addition of a small number of fast shortcut connections.Comment: 8 pages, 6 figures; expanded discussions, added figures and references. To appear in J Stat Phy