4,701 research outputs found

    Nuevos modelos de soberanía. Kosovo y la soberanía irrelevante

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    The question of sovereignty, though constantly evolving, has an enormous relevance both in the legal and the academic fields, and in the world of the Realpolitik. In the case of Kosovo it is possible to conclude that the question of sovereignty turns of less relevance than governance given that at least between 1999 and 2008 there is no state that can actually neither exercise it nor assert the competences and attributes attached to it. After the military intervention of NATO, United Nations deployed territorial administration which placed all the attributes of sovereignty and the instruments of power in the hands of foreign changing agents, unrelated to the territory and to the society of Kosovo. State authority is replaced and superseded by the functional authority of an international body that manages and governs the territory

    Role of oxygen-containing species at Pt(111) on the oxygen reduction reaction in acid media

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    The oxygen reduction reaction (ORR) is one of the fundamental reactions in electrochemistry and has been widely studied, but the mechanistic details of ORR still remain elusive. In this work, the role of electrochemically oxygenated species, such as adsorbed hydroxide, OHads, adsorbed oxygen, Oads, and Pt(111) oxide, PtO, in the ORR dynamics is studied by employing electrochemical techniques, i.e., combining rotating disk mass-transport control with potential sweep rate perturbation. In this framework, a reduction peak at 0.85 V, E ORR, is detected. This peak shows a different electrochemical dynamics than that of Pt(111) oxides. The data analysis suggests that neither OHads nor Oads are the main bottleneck in the mechanism. Instead, results support the reduction of a soluble intermediate species as the rate determining step in the mechanism. On the other hand, PtO species, which are generated at relatively high potentials and are responsible of surface disordering, strongly inhibit the ORR as long as they are adsorbed in the electrode surface.This study has been carried out in the framework of the European Commission FP7 Initial Training Network “ELCAT,” Grant Agreement No. 214936–2. Supports from the Spanish MINECO though project CTQ2013–44083-P and GV through PROMETEOII/2014/013 (FEDER) are greatly acknowledged

    Thermodynamic properties of hydrogen–water adsorption at terraces and steps of Pt(111) vicinal surface electrodes

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    In this work, the effect of temperature on the adsorption states of Pt(111) vicinal surface electrodes in perchloric acid is studied through a thermodynamic analysis. The method allows calculating thermodynamic properties of the interface. In this framework, the concept of the generalized isothermand the statistical thermodynamics description are applied to calculate formal entropies, enthalpies and Gibbs energies,ΔGi0, of the adsorption processes at two-dimensional terraces and one-dimensional steps. These values are compared with data from literature. Additionally, the effect of the step density onΔGi0 and on the lateral interactions between adsorbed species,ωij, at terraces and steps is also determined. Calculated ΔGi0 , entropies and enthalpies are almost temperature-independent, especially at steps, but they depend on the step orientation. In contrast,ΔGi0 and ωij at terraces depend on the step density, following a linear tendency for terrace lengths larger than 5 atoms. However, while ΔGi0 increases with the step density, ωij decreases. Results were explained by considering the modification in the energetic surface balance by hydrogen, Hads, andwater,H2Oads, co-adsorption on the electrode, which in turn determines the whole adsorption processes on terraces and steps.This study has been carried out in the framework of the European Commission FP7 Initial Training Network “ELCAT”, Grant Agreement No. 214936-2. Support from the Spanish MINECO though project CTQ2013-44083-P and GV through PROMETEOII/2014/013 (FEDER) are greatly acknowledged

    Accretion and UV variability in BP Tauri

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    BP Tau is one of the few classical T Tauri stars for which the presence of a hot spot in the surface has been reported without ambiguity. The most likely source of heating is gravitational energy released by the accreting material as it shocks with the stellar surface. This energy is expected to be radiated mainly at UV wavelengths. In this work we report the variations of the UV spectrum of BP Tau for 1992 January 5-19, when the star was monitored with IUE during two rotation periods. Our data indicate that lines that can be excited by recombination processes, such as those from O I and He II, have periodic-like light curves, whereas lines that are only collisionally excited do not follow a periodic-like trend. These results agree with the expectations of the magnetically channeled accretion models. The kinetic energy released in the accretion shocks is expected to heat the gas to temperatures of similar to 10(6) K, which henceforth produces ionizing radiation. The UV (Balmer) continuum and the O I and He II lines are direct outputs of the recombination process. However, the C IV, Si II, and Mg II lines are collisionally excited not only in the shock region but also in inhomogeneous accretion events and in the active (and flaring) magnetosphere, and therefore their light curves are expected to be blurred by these irregular processes. We also report the detection of warm infalling gas from the presence of redshifted (81 km s(-1)) absorption components in some of the high-resolution Mg II profiles available in the IUE and Hubble Space Telescope archives

    Oxygen reduction on nanostructured platinum surfaces in acidic media: Promoting effect of surface steps and ideal response of Pt(1 1 1)

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    In this paper, the role of surface steps on the electrocatalytic activity of platinum nanostructured surfaces for the oxygen reduction reaction (ORR) in acidic medium is evaluated by using stepped surfaces of structure Pt(S)[n(1 1 1) × (1 1 1)] with large terraces (20 ≤ n ≤ 50). It is realized that the inclusion of an even low amount of surface steps enhances the ORR, and linear activity trends are measured when currents at constant potential are plotted vs. the step density. As a consequence, an ideal ORR curve for a defect-free Pt(1 1 1) surface is extrapolated at zero defect density from experimental data and can be compared to that of a quasi-perfect Pt(1 1 1) electrode. It is clearly shown that surface steps promote the electrode activity toward ORR in acid medium. Results are discussed in light of available theoretical and experimental data.This work has been financially supported by a grant from COLCIENCIAS and the Universidad Nacional de Colombia in the framework of the National Program of Formation in Innovation Leaders (Contract No. 472 of 2007). Support from the Spanish MICYNN though project CTQ2010-16271 and GV through PROM-ETEO/2009/045 (FEDER) are also greatly acknowledged

    Oxygen reduction at platinum electrodes: The interplay between surface and surroundings properties

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    In this work, recent progress in the understanding of the mechanism of the oxygen reduction reaction at Pt surfaces is shortly reviewed. Specifically, the presence of a soluble and short-lived intermediate different to H2O2 in the ORR reaction path and the interrelated effect between the surface arrangement, adsorption of oxygen-containing species and water structure in the ORR reactivity in acid environments are discussed. Besides, the influence of the proton concentration on the ORR product distribution, the existence of a chemical step and the possible role of the soluble intermediate as a bifurcation point in the mechanism are also analyzed.The authors would like to thank Fundação de Amparo a Pesquisa do Estado de São Paulo (FAPESP - Procs. 2013/16930-7 and 2014/23486-9), Brazil (A.M.G-M) and the Spanish MINECO though project CTQ2016-76221-P (FEDER) and GV through PROMETEOII/2014/013 ( FEDER) (J.M.F.), for financial supports

    Blockade of the Interaction of Calcineurin with FOXO in Astrocytes Protects Against Amyloid-βInduced Neuronal Death

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    Astrocytes actively participate in neuro-inflammatory processes associated to Alzheimer’s disease (AD), and other brain pathologies. We recently showed that an astrocyte-specific intracellular signaling pathway involving an interaction of the phosphatase calcineurin with the transcription factor FOXO3 is a major driver in AD associated pathological inflammation, suggesting a potential new druggable target for this devastating disease. We have now developed decoy molecules to interfere with calcineurin/FOXO3 interactions, and tested them in astrocytes and neuronal co-cultures exposed to amyloid-β (Aβ) toxicity. We observed that interference of calcineurin/FOXO3 interactions exerts a protective action against A-induced neuronal death and favors the production of a set of growth factors that we hypothesize form part of a cytoprotective pathway to resolve inflammation. Furthermore, interference of the A-induced interaction of calcineurin with FOXO3 by decoy compounds significantly decreased amyloid-β protein precursor (AβPP) synthesis, reduced the AβPP amyloidogenic pathway, resulting in lower Alevels, and blocked the expression of pro-inflammatory cytokines TNFα and IL-6 in astrocytes. Collectively, these data indicate that interrupting pro-inflammatory calcineurin/FOXO3 interactions in astrocytes triggered by Aβ accumulation in brain may constitute an effective new therapeutic approach in AD. Future studies with intranasal delivery, or brain barrier permeable decoy compounds, are warranted

    Isotope Labelling for Reaction Mechanism Analysis in DBD Plasma Processes

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    Dielectric barrier discharge (DBD) plasmas and plasma catalysis are becoming an alternative procedure to activate various gas phase reactions. A low-temperature and normal operating pressure are the main advantages of these processes, but a limited energy efficiency and little selectivity control hinder their practical implementation. In this work, we propose the use of isotope labelling to retrieve information about the intermediate reactions that may intervene during the DBD processes contributing to a decrease in their energy efficiency. The results are shown for the wet reforming reaction of methane, using D2O instead of H2O as reactant, and for the ammonia synthesis, using NH3/D2/N2 mixtures. In the two cases, it was found that a significant amount of outlet gas molecules, either reactants or products, have deuterium in their structure (e.g., HD for hydrogen, CDxHy for methane, or NDxHy for ammonia). From the analysis of the evolution of the labelled molecules as a function of power, useful information has been obtained about the exchange events of H by D atoms (or vice versa) between the plasma intermediate species. An evaluation of the number of these events revealed a significant progression with the plasma power, a tendency that is recognized to be detrimental for the energy efficiency of reactant to product transformation. The labelling technique is proposed as a useful approach for the analysis of plasma reaction mechanisms
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