974 resultados para CU-I COMPLEXES


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El pie de imp. tomado del colofón

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Ubaldi, Baldo degli, 1327-1400. Practica Baldi 1525 : perutilis ac vere aurea practica iuris vtriusq[ue] monarche ac luminis. Impressum Lugduni : in calcographia dilige[n]tissimi i[m]pressoris Iohannis Crespin, 1525, 17 Augusti. [12], XCVI h. Sign.: A8,

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Sign.: a-d8, e6, f8, g6, h-r8, s6, t8, v6, x8, y6, z8, [et]10, []5; A-N8, O5, []5; 2A8, 2B6, 2C8, 2D6, 2E8, 2F6, 2G-2H8, 2J10, 2K-2L6, 2M8

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The electronic properties and the low environmental impact of Cu 3 BiS 3 make this compound a promising material for low-cost thin film solar cell technology. From the first principles, the electronic properties of the isoelectronic substitution of S by O in Cu 3 BiS 3 have been obtained using two different exchange-correlation potentials. This compound has an acceptor level below the conduction band, which modifies the opto-electronic properties with respect to the host semiconductor. In order to analyze a possible efficiency increment with respect to the host semiconductor, we have calculated the maximum efficiency of this photovoltaic absorber material.

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The reliability of Pb-free solder joints is controlled by their microstructural constituents. Therefore, knowledge of the solder microconstituents’ mechanical properties as a function of temperature is required. Sn-Ag-Cu lead-free solder alloy contains three phases: a Sn-rich phase, and the intermetallic compounds (IMCs) Cu6Sn5 and Ag3Sn. Typically, the Sn-rich phase is surrounded by a eutectic mixture of β-Sn, Cu6Sn5, and Ag3Sn. In this paper, we report on the Young’s modulus and hardness of the Cu6Sn5 and Cu3Sn IMCs, the β-Sn phase, and the eutectic compound, as measured by nanoindentation at elevated temperatures. For both the β-Sn phase and the eutectic compound, the hardness and Young’s modulus exhibited strong temperature dependence. In the case of the intermetallics, this temperature dependence is observed for Cu6Sn5, but the mechanical properties of Cu3Sn are more stable up to 200°C.

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Transition metals such as Fe, Cu, Mn, Ni, or Co are essential nutrients, as they are constitutive elements of a significant fraction of cell proteins. Such metals are present in the active site of many enzymes, and also participate as structural elements in different proteins. From a chemical point of view, metals have a defined order of affinity for binding, designated as the Irving-Williams series (Irving and Williams, 1948) Mg2+ menor que Mn2+ menor que Fe2+ menor que Co2+ menor que Ni2+ menor que Cu2+mayor queZn2+ Since cells contain a high number of different proteins harbouring different metal ions, a simplistic model in which proteins are synthesized and metals imported into a ?cytoplasmic soup? cannot explain the final product that we find in the cell. Instead we need to envisage a complex model in which specific ligands are present in definite amounts to leave the right amounts of available metals and protein binding sites, so specific pairs can bind appropriately. A critical control on the amount of ligands and metal present is exerted through specific metal-responsive regulators able to induce the synthesis of the right amount of ligands (essentially metal binding proteins), import and efflux proteins. These systems are adapted to establish the metal-protein equilibria compatible with the formation of the right metalloprotein complexes. Understanding this complex network of interactions is central to the understanding of metal metabolism for the synthesis of metalloenzymes, a key topic in the Rhizobium-legume symbiosis. In the case of the Rhizobium leguminosarum bv viciae (Rlv) UPM791 -Pisum sativum symbiotic system, the concentration of nickel in the plant nutrient solution is a limiting factor for hydrogenase expression, and provision of high amounts of this element to the plant nutrient solution is required to ensure optimal levels of enzyme synthesis (Brito et al., 1994).

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Based on our previous knowledge on Cu/Nb nanoscale metallic multilayers (NMMs), Cu/WNMMs show a good potential for applications as heat skins in plasma experiments and armors, and it could be expected that the substitution of Nb byWwould increase the strength, particularly at high temperatures. To check this hypothesis, Cu/WNMMs with individual layer thicknesses ranging between 5 and 30 nm were deposited by physical vapour deposition, and their mechanical properties were measured by nanoindentation. The results showed that, contrary to Cu/Nb NMMs, the hardness was independent of the layer thickness and decreased rapidlywith temperature, especially above 200 °C. This behavior was attributed to the growth morphology of theWlayers aswell as the jagged Cu/W interface, both a consequence of the lowW adatom mobility during deposition. Therefore, future efforts on the development of Cu/Wmultilayers should concentrate on optimization of theWdeposition parameters via substrate heating and/or ion assisted deposition to increase the W adatom mobility during deposition.

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En este trabajo doctoral se evaluó la bioaccesibilidad in vitro para As, Co, Cr, Cu, Ni, Pb y Zn (en la fracción menor de 100μm) por tres procedimientos distintos en 32 muestras de suelo superficial, recogidas en 16 parques infantiles de la ciudad de Madrid.. Dos de los métodos de extracción (SBET y extracción con HCl a pH=1.5) reproducen únicamente la fase gástrica, mientras que otro (RIVM) tiene en cuenta un proceso completo de digestión (gástrico+intestinal). La bioaccesibilidad (%) se definió frente a las concentraciones pseudototales de los elementos traza estudiados (agua regia), utilizando un modelo de regresión lineal pasando por el origen. Los dos métodos gástricos ofrecieron resultados similares y consistentes con datos de otros estudios, siendo el orden de bioaccesibilidad As ≈ Cu ≈ Pb ≈ Zn > Co > Ni > Cr, con rangos entre el 63 y el 7%. Para el procedimiento RIVM (gástrico + intestinal) se obtuvieron valores de un orden similar a los obtenidos en fase gástrica para los elementos As, Cu, Pb y Zn (muy similares para el Zn, algo superiores para Cu y Pb, y algo inferiores para As). Por el contrario, la bioaccesibilidad de Co y Cu es, en este caso, muy superior a la resultante de los ensayos en fase gástrica. El orden de bioaccesibilidad es Co ≈ Cu ≈ Pb > As ≈ Cr ≈ Zn, con rangos entre el 42 y el 69%. Los resultados de los tres procedimientos evaluados correlacionan muy intensamente para los elementos traza As, Cu, Pb y Zn, existiendo intensas correlaciones entre casi todos los elementos estudiados para las dos fases gástricas, no siendo así en el ensayo de digestión completa. Se estudiaron algunas propiedades físico-químicas de los suelos muestreados, así como su composición en algunos elementos mayoritarios con el objeto de evaluar su influencia sobre la bioaccesibilidad. Se observa una dependencia de la bioaccesibilidad (%) de distintos elementos respecto a algunas propiedades de los suelos estudiados, tales como: contenido en Fe, Ca (carbonatos) y P, materia orgánica y pH. El contenido en Fe resulta ser muy relevante en cuanto a la bioaccesibilidad obtenida. En todos los casos correlaciona negativamente con el porcentaje de bioaccesibilidad siendo más significativo este fenómeno en el caso de las extracciones en fase gástrica. Se sugiere que dada la baja solubilización de los óxidos de hierro en los medios extractantes empleados hay una fuerte adsorción de complejos aniónicos (metal-anión cloruro) sobre la superficie de estos óxidos de Fe, con la consiguientes disminución de la bioaccesibilidad. En cuanto al contenido en calcio (carbonatos) este dato parece muy relevante si nos referimos a la bioaccesibilidad del As. Efectivamente el As aparece ligado al Ca del suelo y su solubilización en medios ácidos implicaría un aumento de la bioaccesibilidad del As, mientras que su precipitación al pasar a pH básico (fase intestinal) provocaría una disminución de la bioaccesibilidad. La materia orgánica sólo se ha demostrado relevante respecto a los contenidos pseudototales para el Zn. Para el porcentaje de bioaccesibilidad es significativo para muchos elementos en los ensayos en fase gástrica. La influencia del pH de los suelos estudiados sólo parece ser muy significativo en el caso del Cr. Los valores altamente homogéneos del pH de los suelos estudiados sin duda hacen que este parámetro no resulte significativo para más elementos, tal como se desprende de estudios anteriores. ABSTRACT A total of 32 samples of superficial soil were collected from 16 playground areas in Madrid. The in vitro bioaccessibility of As, Co, Cr, Ni, Pb and Zn (fraction below 100μm) was evaluated by means of three extraction processes. Two of them (SBET and HCl-extraction, pH=1.5) simulate the gastric enviroment, while the other one (RIVM) reproduces a gastric+intestinal digestion sequence. Bioaccessibility (%) was compared against pseudo-total concentrations of trace elements studied (aqua regia) with a linear regression model (forced to intercept the origin) Both gastric methods offered very similar and consistent results with data from other studies, with bioaccessibilities following the order: As ≈ Cu ≈ Pb ≈ Zn > Co > Ni > Cr, and ranging from 63% to 7% The values obtained through RIVM (gastric+ intestinal) method are similar to those obtained in gastric environment for elements: As, Cu, Pb and Zn (very similar to Zn, to a higher extent Cu and Pb, and to a lower extent As). On the contrary the bioaccessibility obtained for elements Co and Cu is considerable higher than in gastric environment sequence. Bioaccessibilities follows the order Co ≈ Cu ≈ Pb >As ≈ Cr ≈ Zn, ranging between 42 and 69%. The three procedures used correlate very intensively to trace elements As,Cu, Pb and Zn, existing strong correlations between almost all elements studied for the two gastric environment, not in the case of the complete digestion sequence. Some soil physical – chemical properties selected were studied, as well as their composition in some main elements in order to assess their influence on bioaccessibility. A dependence was observed between different elements bioaccesibility (%) and some soil properties, such as: Fe, Ca (carbonate) content and P, organic matter and pH. Fe content becomes very relevant regarding the bioaccessibility obtained. In all cases it correlated negatively with bioaccessibility percentage being more significant this phenomenon in gastric environment extractions. It is suggested that given the low solubility of iron oxide in the extractant media used there has to be a strong adsorption of anionic complexes (metal – chloride anion) on these Fe oxides surface, with a consequent decrease of bioaccessibility. Regarding calcium (carbonate) content this data seems very relevant referred to As bioaccessibility. Indeed, As appears to be bound to soil Ca and its solubilisation in acid media would increase As bioaccessibility, while its precipitation at basic pH (intestinal environment) would cause a reduction in bioaccessibility. The influence of organic matter only seemed significant for Zn “total” content, while it is significant in terms of gastric bioaccessibility for many elements. Soil pH only seems to be very significant in case of Cr. The highly homogeneous values for soil pH makes the influence of this parameter negligible for the other elements, unlike what has been observed in several previous studies.

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El objetivo principal del presente proyecto es implantar un sistema de calidad en un laboratorio de caracterización de residuos, con el fin de obtener la acreditación otorgada por la Entidad Nacional de Acreditación (ENAC) como laboratorio de caracterización de residuos metalúrgicos no férreos. El sistema de calidad a implantar se basa en la Norma UNE-EN ISO/IEC 17025:2005 (requisitos generales para la competencia de los laboratorios de ensayo y calibración). Se trata por tanto de determinar los principales residuos de proceso y operación, de la metalurgia del Al, Cu, Zn y Pb, para posteriormente y mediante las normas UNEEN-CEN identificar los ensayos normalizados de caracterización de dichos residuos. y adecuar dichos ensayos a la norma. Finalmente se describe el proceso de implantación del sistema de calidad basado en la citada norma, y se hace un estudio económico que incluye tanto los gastos de inversión en equipos como los gastos de operación y mantenimiento (CAPEX y OPEX). Todo ello para poder ser acreditados por un organismo como ENAC.

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We present a helical unwinding assay for reversibly binding DNA ligands that uses closed circular DNA, topoisomerase I (Topo I), and two-dimensional agarose gel electrophoresis. Serially diluted Topo I relaxation reactions at constant DNA/ligand ratio are performed, and the resulting apparent unwinding of the closed circular DNA is used to calculate both ligand unwinding angle (φ) and intrinsic association constant (Ka). Mathematical treatment of apparent unwinding is formally analogous to that of apparent extinction coefficient data for optical binding titrations. Extrapolation to infinite DNA concentration yields the true unwinding angle of a given ligand and its association constant under Topo I relaxation conditions. Thus this assay delivers simultaneous structural and thermodynamic information describing the ligand–DNA complex. The utility of this assay has been demonstrated by using calichearubicin B (CRB), a synthetic hybrid molecule containing the anthraquinone chromophore of (DA) and the carbohydrate domain of calicheamicin γ1I. The unwinding angle for CRB calculated by this method is −5.3 ± 0.5°. Its Ka value is 0.20 × 106 M−1. For comparison, the unwinding angles of ethidium bromide and DA have been independently calculated, and the results are in agreement with canonical values for these compounds. Although a stronger binder to selected sites, CRB is a less potent unwinder than its parent compound DA. The assay requires only small amounts of ligand and offers an attractive option for analysis of DNA binding by synthetic and natural compounds.

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Cell surface heparan sulfate proteoglycan (HSPG) interactions with type I collagen may be a ubiquitous cell adhesion mechanism. However, the HSPG binding sites on type I collagen are unknown. Previously we mapped heparin binding to the vicinity of the type I collagen N terminus by electron microscopy. The present study has identified type I collagen sequences used for heparin binding and endothelial cell–collagen interactions. Using affinity coelectrophoresis, we found heparin to bind as follows: to type I collagen with high affinity (Kd ≈ 150 nM); triple-helical peptides (THPs) including the basic N-terminal sequence α1(I)87–92, KGHRGF, with intermediate affinities (Kd ≈ 2 μM); and THPs including other collagenous sequences, or single-stranded sequences, negligibly (Kd ≫ 10 μM). Thus, heparin–type I collagen binding likely relies on an N-terminal basic triple-helical domain represented once within each monomer, and at multiple sites within fibrils. We next defined the features of type I collagen necessary for angiogenesis in a system in which type I collagen and heparin rapidly induce endothelial tube formation in vitro. When peptides, denatured or monomeric type I collagen, or type V collagen was substituted for type I collagen, no tubes formed. However, when peptides and type I collagen were tested together, only the most heparin-avid THPs inhibited tube formation, likely by influencing cell interactions with collagen–heparin complexes. Thus, induction of endothelial tube morphogenesis by type I collagen may depend upon its triple-helical and fibrillar conformations and on the N-terminal heparin-binding site identified here.

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Nonobese diabetic (NOD) mice develop insulin-dependent diabetes mellitus due to autoimmune T lymphocyte-mediated destruction of pancreatic β cells. Although both major histocompatibility complex class I-restricted CD8+ and class II-restricted CD4+ T cell subsets are required, the specific role each subset plays in the pathogenic process is still unclear. Here we show that class I-dependent T cells are required for all but the terminal stages of autoimmune diabetes development. To characterize the diabetogenic CD8+ T cells responsible, we isolated and propagated in vitro CD8+ T cells from the earliest insulitic lesions of NOD mice. They were cytotoxic to NOD islet cells, restricted to H-2Kd, and showed a diverse T cell receptor β chain repertoire. In contrast, their α chain repertoire was more restricted, with a recurrent amino acid sequence motif in the complementarity-determining region 3 loop and a prevalence of Vα17 family members frequently joined to the Jα42 gene segment. These results suggest that a number of the CD8+ T cells participating in the initial phase of autoimmune β cell destruction recognize a common structural component of Kd/peptide complexes on pancreatic β cells, possibly a single peptide.