674 research outputs found

    New anallytic approximations based on the Magnus expansion

    Get PDF
    The Magnus expansion is a frequently used tool to get approximate analytic solutions of time-dependent linear ordinary differential equations and in particular the Schrödinger equation in quantum mechanics. However, the complexity of the expansion restricts its use in practice only to the first terms. Here we introduce new and more accurate analytic approximations based on the Magnus expansion involving only univariate integrals which also shares with the exact solution its main qualitative and geometric propertie

    Empleo de isótopos ambientales para discernir la contaminación salina de la cuenca del río Llobregat

    Get PDF
    La formación geológica salina de la comarca del Bages(Barcelona) y su explotación minera en diferentes puntos de la cuenca del Llobregat, influyen en la salinización de los ríos Cardener y Llobregat. La cuenca potásica catalana presenta dos peculiaridades: la formación salina tiene un afloramiento en Cardona, y en algunas zonas las capas de mineral se encuentran cerca de la superficie pero sin aflorar. La geología del terreno puede influir en la salinidad de las aguas de la cuenca por contacto directo con los materiales salinos. La actividad minera de Cardona (cerrada en 1990), Suria,Balsareny y Sallent, genera en la producción del mineral un residuo salino que se acumula en el exterior de las minas formándose las escombreras salinas o «runams». Sus salessolubles se disuelven con la lluvia, y pueden llegar a las aguas superficiales y aguas subterráneas del entorno. El objetivo de este trabajo es evaluar las aportaciones salinas a la cuenca del río Llobregat, separando las de origen natural y las de procedencia antrópica, utilizando la composición isotópica del azufre y del oxigeno del sulfato disuelto en sus aguas. También se cuantifica el origen natural y antrópico de los cloruros que se aportan

    Alteraciones fisarias tras radiación láser

    Get PDF
    Ante el auge actual de la radiación láser y al no encontrar bibliografía referente al posible efecto sobre el cartílago de crecimiento, hemos decidido hacer una valoración del mismo en un modelo experimental. Se utilizaron 50 ratas, estableciéndose cinco grupos de estudio de 10 animales cada uno, dependiendo de la dosis de radiación aplicada percutáneamente sobre la fisis femoral distal. Tras el estudio ultraestructural, histoquímico y morfométrico, hemos observado una serie de alteraciones indicadoras de un daño celular directo. Los hallazgos permiten concluir que este tipo de radiación está contraindicado absolutamente durante la fase de crecimiento óseo o en el esqueleto inmaduro.In view of the present importance of Laser Radiation, and due to the lack of references about its effects on the growth cartilage, we designed an experimental model in order to asses it. A total of 50 rats were used, establishing five groups of study at 10 animals each, depending on the dosis of radiation applied percutaneously on the distal femoral phisys. After the structural, histochemical and morphometric study, we observed a series of alterations indicating a direct celular damage at the physion. From the results, it is concluded that laser radiation should be on absolute contraindication during the phase of bone growth or in the inmature skeleton

    Phylogenenetic approach of the section Bulbocodii D.C. of Narcissus based on cpDNA. A case of taxonomic inflation ?

    Get PDF
    In this paper, we analyzed the phylogeny of the section Bulbocodii (genus Narcissus; Amarillydaceae) using the matK and trnL-F fragments of cpDNA in order to review the validity of the recognized taxa. Our results indicate that Narcissus obesus should be considered a valid species, and that N. blancoi is a distinct taxon. In addition, seven previously recognized species, N. juressianus, N. subnivalis, N. graellsii, N. conspicuus, N. citrinus, N. nivalis, and N. quintanilhae, should be assigned to an infraspecific rank under N. bulbocodium, as they are not valid species. In addition, we analyzed the distribution of the three morphological characters widely used in the systematics of this section and found that their variation does not agree with the phylogenetic results, rendering these characters limited taxonomical utility. This result suggests that the section Bulbocodii shows high morphological lability, which can explain the proliferation of nominal speciesinfo:eu-repo/semantics/publishedVersio

    Understanding the active sites of boron nitride for CWPO: An experimental and computational approach

    Get PDF
    Hexagonal boron nitride (h-BN) has been explored as a catalyst for degrading persistent organic pollutants in wastewater by Catalytic Wet Peroxide Oxidation (CWPO). Herein, the superior activity of the h-BN on the phenol degradation (model pollutant) compared to other metal-free catalysts, such as carbon-based ones, and the lower selectivity to CO encourage the potential application of h-BN catalysts in CWPO processes. Through a combined density functional theory calculations, experimental reactions and catalyst characterization approach, a com- prehensive study on the reaction mechanism has been conducted. According to this, only defected B atoms in the h-BN layer, protonated as B-(OH2)+, decompose the hydrogen peroxide into highly reactive hydroxyl radicals. The radical species diffuse towards inner h-BN regions and react with the phenol adsorbed by π-π interaction on the h-BN surface. Oxidation by-products cause carbonaceous deposits and progressive deactivation of the h-BN catalyst that can be directly regenerated by burning off in air.Comunidad de Madrid-S2018/EMT-4341Ministerio de Ciencia e Innovación y Agencia Estatal de Investigación de España, y fondos FEDER de la Unión Europea (MCIU/AEI/FEDER, UE)-RTI2018-095052-B-I00Ministerio de Ciencia e Innovación de España y EU-FEDER-PID2019-106871 GB-I00Junta de Andalucía-FEDER-US-1381410Comunidad de Madrid-PEJD-2018-PRE/AMB-901

    Comparación entre poblaciones de circones detríticos de rocas ordovícicas del Pirineo y de otros terrenos perigondwánicos: implicaciones paleogeográficas

    Get PDF
    The first LA-ICP-MS U-Pb detrital zircon ages from quartzites located in the Ordovician rocks from the Central Pyrenees (the Rabassa Dome, Andorra) were investigated. The four studied samples present very similar U-Pb age patterns. The main age populations correspond to Neoproterozoic (Ediacarian–Cryogenian, ca. 550–750 Ma), Grenvillian (Tonian–Stenian, ca. 850–1100 Ma), Paleoproterozoic (Orosirian, ca. 1900–2100 Ma) and Neoarchean (ca. 2500–2650 Ma). The results presented here enable us to discuss the lower Paleozoic paleoposition of the Pyrenean basement rocks. We have compared our samples with that from other Perigondwanan terrains such as Sardinia, Sicily and the Iberian Massif. The similarity with the Sardinian age distribution suggests that these two terranes could share the same source area and that they were paleogeographically close in Ordovician times in front of the Arabian-Nubian Shield. Comparisons with previous proposed reconstructions allow us to obtain a more complete view of the paleogeography of the Northern Gondwana margin during the Cambro-Ordovician.Se han estudiado los primeros datos de edades de LA-ICP-MS U-Pb en circones detríticos correspondientes a rocas ordovícicas del Pirineo central (Domo de la Rabassa, Andorra). Las cuatro muestras estudiadas presentan unos patrones de edades U-Pb muy similares. Las principales poblaciones corresponden al Neoproterozoico (Ediacárico – Criogénico, ca. 550-750 Ma), Grenvilliense (Tónico – Esténico, ca. 580-1100 Ma), Paleoproterozoico (Orosírico, ca. 1900-2100 Ma) y Neoarcaico (ca. 2500-2650 Ma). Los resultados presentados nos permiten discutir sobre la paleoposición de las rocas del basamento pirenaico durante el Paleozoico inferior. Se han comparado nuestras muestras con las de otros terrenos perigondwánicos tales como Cerdeña, Sicilia y el Macizo Ibérico. Las similitudes con la distribución de edades de las muestras de Cerdeña sugieren que estos dos terrenos podrían compartir las mismas áreas fuente y que se podrían encontrar en posiciones cercanas durante el Ordovícico, en frente del escudo de Arabia y Nubia. Las comparaciones con algunas reconstrucciones propuestas previamente nos han permitido obtener una visión más completa de la paleogeografía del margen norte de Gondwana durante el Cambro- Ordovícico.Depto. de Mineralogía y PetrologíaFac. de Ciencias GeológicasTRUEMinisterio de Economía y Competitividad (MINECO)Consolider-Ingenio 2010pu

    Sparse initial data indentification for parabolic pde and its finite element approximations

    Get PDF
    We address the problem of inverse source identification for parabolic equations from the optimal control viewpoint employing measures of minimal norm as initial data. We adopt the point of view of approximate controllability so that the target is not required to be achieved exactly but only in an approximate sense. We prove an approximate inversion result and derive a characterization of the optimal initial measures by means of duality and the minimization of a suitable quadratic functional on the solutions of the adjoint system. We prove the sparsity of the optimal initial measures showing that they are supported in sets of null Lebesgue measure. As a consequence, approximate controllability can be achieved efficiently by means of controls that are activated in a finite number of pointwise locations. Moreover, we discuss the finite element numerical approximation of the control problem providing a convergence result of the corresponding optimal measures and states as the discretization parameters tend to zero.The first author was supported by Spanish Ministerio de Economía y Competitividad under project MTM2011-22711. The third author was supported by the Advanced Grant NUMERIWAVES/FP7-246775 of the European Research Council Executive Agency, FA9550-14-1-0214 of the EOARD-AFOSR, FA9550-15-1-0027 of AFOSR, the BERC 2014-2017 program of the Basque Government, the MTM2011-29306 and SEV-2013-0323 Grants of the MINECO, the CIMI-Toulouse Excellence Chair in PDEs, Control and Numerics and a Humboldt Award at the University of Erlangen-Nürnberg

    Three novel mutations in the CFTR gene identified in Galician patients

    Get PDF
    AbstractWe report three novel CFTR missense mutations detected in Spanish patients from Galicia (North West of Spain). In the first case, a patient homozygous for a novel S1045Y mutation died due to pulmonary problems. In the other two cases, both heterozygous for novel mutations combined with the F508del mutation, clinical symptoms were different depending on the mutation, detected as M595I and A107V

    The feeding of American plaice (Hippoglossoides platessoides), Redfish (Sebastes marinus) and Cod (Gadus morhua) in the Flemish Cap during July 1988

    Get PDF
    A randomly stratified bottom-trawl survey was realized in the Flemish Cap (NAFO Div. 3M) in July 1988. The stomach contents of three species were studied: 320 of American plaice (Hippoglossoides platessoides), 203 of redfish (Sebastes Marinus) and 468 of cod (Gadus morhua). The cod specimens were classified taking into account age groups; in the case of other species by length classes. The food items, the prey occurrence index and the diversity index were determined too. The Schoener overlap index was calculated to study the intraspecific diet overlap in cod and the interspecific diet overlap between the three species. The relation between predator size (cod) and prey size (redfish) was also studied
    corecore