Interaction of oxygen with TiN (001): N↔O exchange and oxidation process

This work presents a detailed experimental and theoretical study of the oxidation of TiN(001) using a combination of synchrotron-based photoemission and density functional theory (DFT). Experimentally, the adsorption of O2 on TiN(001) was investigated at temperatures between 250 and 450K. At the lowest temperature, there was chemisorption of oxygen (O2,gas→2Oads) without significant surface oxidation. In contrast, at 450K the amount of O2 adsorbed increased continuously, there was no evidence for an oxygen saturation coverage, a clear signal in the Ti 2p core level spectra denoted the presence of TiOx species, and desorption of both N2 and NO was detected. The DFT calculations show that the adsorption/dissociation of O2 is highly exothermic on a TiN(001) substrate and is carried out mainly by the Ti centers. A high oxygen coverage (larger than 0.5 ML) may induce some structural reconstructions of the surface. The exchange of a surface N atom by an O adatom is a highly endothermic process (ΔE=2.84eV). However, the overall oxidation of the surface layer is thermodynamically favored due to the energy released by the dissociative adsorption of O2 and the formation of N2 or NO. Both experimental and theoretical results lead to conclude that a TiN+mO2→TiOx+NO reaction is an important exit channel for nitrogen in the oxidation process.Ministerio de Educación y Ciencia de España, MEC. MAT2005-01872Junta de Andalucía. FQM-132División de Ciencias Químicas del Departamento de Energía de EE. UU. DE-AC02-98CH10086Fundación japonesa para la Ciencia de los Materiale

Análisis del comportamiento a compresión de un laminado [0,90,0,90] de tejido no ondulado mediante un modelo 3D de elementos finitos

VI CONGRESO NACIONAL DE MATERIALES COMPUESTOS. Celebrado en Valencia, 27-29 de junio de 2005.El presente trabajo está dedicado al análisis numérico del comportamiento a compresión de un laminado [0, 90]a de tejido no ondulado o non-crimp fabric (NCF). Para ello se ha realizado un modelo tridimensional de elementos finitos del laminado a nivel mesoscópico en el que se han modelado los constituyentes del material, mazos de fibras y paquetes de resina, como entes homogéneos, sin considerar la microestructura que caracteriza a cada uno de ellos. Los resultados obtenidos con este modelo muestran que el mecanismo de fallo a compresión de un laminado de NCF está asociado a la curvatura que presentan los mazos de fibras en este tipo de materiales compuestos, como consecuencia del curado. En efecto, en la zona en que dicha curvatura es máxima aparecen deformaciones tangenciales de diferente signo cuya diferencia crece a medida que la carga de compresión aplicada aumenta hasta que llega un momento en que el material no es capaz de soportarlo y se produce el fallo.Unión Europea (FALCOM) G4RD-CT- 0069

A theoretical insight into the catalytic effect of a mixed-metal oxide at the nanometer level: The case of the highly active metal/CeOx/TiO2(110) catalysts

The structural and electronic properties of CeOx species supported on the rutile TiO2 110 surface have been examined by means of periodic density-functional calculations that use a generalized gradient approximation functional including a Hubbard-like type correction. Deposition of Ce atoms leads in a first step to Ce3+ ions bound to the surface through bridge and in-plane oxygen atoms, the released electrons occupying the Ti 3d empty orbitals. Further addition of Ce and molecular oxygen gives place to Ce2O3 dimers diagonally arranged on the surface, in agreement with the spots observed in the scanning tunnel microscope images. The formation process of CeOx nanoparticles NPs on the TiO2 surface is highly exothermic and our calculations show that the redox properties of the Ce III-Ce IV couple are significantly altered when it is supported on TiO2. In particular the reactivity against CO/O2 indicates that on the surface the presence of Ce III is favored over Ce IV species. Our results also indicate that the CeOx /TiO2 interface should be seen like a real mixed-metal oxide rather than a supported NP of ceria. Finally, in the context of the high catalytic activity of the M /CeOx /TiO2 M =Au,Cu,Pt systems in the water-gas shift reaction, we have examined the dissociation of water on the CeOx /TiO2 surface and estimated a barrier as small as 0.04 eV, i.e. 8 times smaller than that computed for a TiO2 oxygen vacancy. This result agrees with the experimental superior catalytic activity of the M /CeOx /TiO2 systems over M /TiO2.Gobierno de España. Ministerio Ciencia e Innovación (MICINN) MAT2005-01872 y CSD2008-0023Junta de Andalucía FQM-132Departamento de Energía de EE. UU. División de Subvención de Ciencias Químicas DE-AC02-98CH1088

The Front End Electronics of the Scintillator Pad Detector of LHCb Calorimeter

In this paper the Front End electronics of the Scintillator Pad Detector (SPD) is outlined. The SPD is a sub-system of the Calorimeter of the LHCb experiment designed to discriminate between charged and neutral particles for the first level trigger. The system design is presented, describing its different functionalities implemented through three different cards and several ASICs. These functionalities are signal processing and digitization, data transmission, interface with control and timing systems of the experiment, low voltage power supply distribution and monitoring. Special emphasis is placed on installation and commissioning subjects such as cabling, grounding, shielding and power distribution

Aspectos micromecánicos de grietas transversales de interfase entre fibra y matriz

IV CONGRESO NACIONAL DE MATERIALES COMPUESTOS. Celebrado en Gijón, los días 21,22 y 23 de Noviembre de 2001Se realiza un estudio micromecánico de la presencia de grietas transversales en materiales compuestos reforzados con fibra. El objetivo del estudio es clarificar la presencia de contacto entre la fibra y la matriz en la zona despegada en función del tamaño del despegue, asi como las razones de la aparición de esta zona de contacto. Esta cuestión es de importancia para establecer los parámetros que controlan la fractura y el modo en que ésta se produce. Para dilucidar estas cuestiones un especial énfasis es puesto en la caracterización del estado tensional en el entorno del.fondo de la grieta de interfase. El estudio se realiza por medio del Método de los Elementos de Contorno.A micromechanical study is carried out in presence o.f transversal cracks in flbre reinforced composite materials. The o~jetive of the study is to clarify the presence o( contact between the flbre and the matrix in the unbonded zone as a function of tlze size of the unhonded zone. as well as the reasons .for the appearance of th is contact zone. This question is of great importance lo establish the parameters that control the fi·acture and the mode under which it appears. To elucida te these questions, a special emphasis has been pul on the characterization of the stress state in the neighbourhood of the crack tip. The study is pe1jormed by means ofthe Boundmy Element Method

Cu Deposited on CeOx-Modified TiO2(110): Synergistic Effects at the Metal-Oxide Interface and the Mechanism of the WGS Reaction

Experimental techniques and DFT calculations have been combined to study and compare the effect of the metal-substrate interaction in Cu/TiO2(110) and Cu/CeOx/TiO2(110) catalysts for the water-gas shift (WGS) reaction. Experiments and theory show that CeOx nanoparticles affect the dispersion of copper on titania, and on the formed copper-ceria interface, there are synergistic effects which favor water dissociation and the WGS reaction. The minimum energy path for the WGS reaction on the new highly active catalytic system Cu/CeOx/TiO2(110) has been predicted by theoretical calculations. Main steps such as adsorption-dissociation of water and∗OCOH carboxyl intermediate formation-deprotonation have been characterized. In this very particular system, water splitting is no longer the rate-limiting step because it can dissociate overcoming an energy barrier of only 0.92 kcal/mol. One important insight of the present work is to show that easy full hydration of the ceria particles strongly lowers the reaction barrier for the deprotonation of the∗OCOH intermediate and facilitates the evolution of the WGS reaction. For the first time, a system has been found on which the WGS reaction is able to work with all the involved energy barriers below 12 kcal/mol. This remarkable behavior makes the metal/CeOx/TiO2 family a potential candidate for industrial application as catalysts in the WGS reaction. The change in the metal-support interactions when going from Cu/TiO2 to Cu/CeOx/TiO2 illustrates the importance of optimizing the oxide phase when improving the performance of metal/oxide catalysts for the WGS.Ministerio de Economía y Competitividad MAT2012-31526, CSD2008-0023U.S. Department of Energy DE-SC001270

The inflammatory potential of diet is related to incident frailty and slow walking in older adults

Background: Certain foods and dietary patterns have been associated with both inflammation and frailty. As chronic inflammation may play a role in frailty and disability, we examined the association of the inflammatory potential of diet with these outcomes. Methods: Data were taken from 1948 community-dwelling individuals =60 years old from the Seniors-ENRICA cohort, who were recruited in 2008–2010 and followed-up through 2012. Baseline diet data, obtained with a validated diet history, was used to calculate Shivappa's Dietary Inflammatory Index (DII), an “a priori” pattern score which is based on known associations of foods and nutrients with inflammation, and Tabung's Empirical Dietary Inflammatory Index (EDII), an “a posteriori” pattern score which was statistically derived from an epidemiological study. At follow-up, incident frailty was assessed with Fried's criteria, and incident limitation in instrumental activities of daily living (IADL) with the Lawton-Brody index. Statistical analyses were performed with logistic regression, and adjusted for the main confounders. Results: Compared with individuals in the lowest tertile of DII, those in the highest tertile showed higher risk of frailty (odds ratio [OR] 2.48; 95% confidence interval [CI]: 1.42, 4.44, p-trend = 0.001) and IADL disability (OR: 1.96; 95% CI: 1.03, 3.86, p-trend = 0.035). By contrast, EDII did not show an association with these outcomes. The DII score was associated with slow gait speed, both as a low score in the Short Physical Performance Battery test (OR: 1.82; 95% CI: 1.27, 2.62, p-trend = 0.001) and as a positive Fried's criterion (OR: 1.64; 95% CI: 1.08, 2.51, p-trend = 0.021), which use different thresholds. Conclusions: DII predicted frailty and IADL while EDII did not. DII is able to measure diet healthiness in terms of physical decline in addition to avoidance of inflammation

N doping of TiO 2(110) Photoemission and density-functional studies

The electronic properties of N-doped rutile TiO2(110) have been investigated using synchrotron-based photoemission and density-functional calculations. The doping via N+2 ion bombardment leads to the implantation of N atoms (∼5% saturation concentration) that coexist with O vacancies. Ti 2p core level spectra show the formation of Ti3+ and a second partially reduced Ti species with oxidation states between +4 and +3. The valence region of the TiO2−xNy(110) systems exhibits a broad peak for Ti3+ near the Fermi level and N-induced features above the O 2p valence band that shift the edge up by ∼0.5eV. The magnitude of this shift is consistent with the “redshift” observed in the ultraviolet spectrum of N-doped TiO2. The experimental and theoretical results show the existence of attractive interactions between the dopant and O vacancies. First, the presence of N embedded in the surface layer reduces the formation energy of O vacancies. Second, the existence of O vacancies stabilizes the N impurities with respect to N2(g) formation. When oxygen vacancies and N impurities are together there is an electron transfer from the higher energy 3d band of Ti3+ to the lower energy 2p band of the N2− impurities.Ministerio de Ciencia y Tecnología español MAT2005-01872Junta de Andalucía FQM-13