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

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

Uso de los anuncios televisivos como recurso didáctico en las disciplinas artísticas. Las "panaderas"

Esta investigación se centra en la posibilidad de ofrecer al docente de las disciplinas artísticas herramientas y estrategias para la inclusión didáctica de la Cultura Visual. La metodología de investigación es un estudio de caso con alumnado del Máster universitario en profesorado de educación secundaria y enseñanzas artísticas, de idiomas y deportivas. Se desarrolla durante el curso académico 2012-2013, en la Facultad de Educación de la Universidad de Alicante. El diseño de formación que se propone pasaría por cinco fases principales que garantizan la combinación de las artes visuales y musicales con finalidad pedagógica. La propuesta se articula mediante: el análisis de anuncios televisivos de alta carga estética, rítmica y musical; el descubrimiento de las fuentes de las que beben los creativos, relacionadas con los juegos de coordinación; el aprendizaje de ejercicios básicos de percusión corporal; la incorporación de elementos estéticos que aumentan la carga visual; para finalmente combinar los aspectos analizados y aprendidos en la creación de una nueva propuesta didáctica. Se parte del anuncio de Coca-Cola “al limón” del año 2003, en el que participó Mayumana; sobre el ritmo de las "panaderas" de Teruel, Segovia y Zamora durante la preparación del pan

Changing the physical and chemical properties of titanium oxynitrides TiN1-x Ox by changing the composition

The stability and structural properties of titanium oxynitrides, TiN1-x Ox, of different compositions are theoretically analyzed by means of first-principles periodic density-functional calculations. We show that at x=0.55-0.6 there is a change in the preferred structure from that of NaCl type to the α-TiO arrangement. For the NaCl-type structure the cell volume increases with x while it decreases with x for the α-TiO structure. The bulk moduli are always much larger for NaCl-type structures than for α-TiO and they decrease as the amount of O increases, moving from 280 GPa for TiN to 226 GPa for TiO (NaCl-type structure) or 197 GPa for α-TiO. Changes in the electronic structure with the composition are also considered. In general we found that in the two types of structure (NaCl and α-TiO), both the band gap and the ionic character increase with the O concentration.Ministerio de Ciencia e Innovación MAT2008-04918Consolider Ingenio CSD2008–0002

Role of vacancies in the structural stability of α-TiO: a first-principles study based on density-functional calculations

Many transition-metal monoxides formally having an fcc rock-salt structure exhibit a relatively high degree of vacancies, in particular, the most stable structure of stoichiometric titanium monoxide corresponds to a monoclinic phase, α-TiO, showing 15% vacancies. The role of such vacancies on the stability of the solid has been the subject of speculations for the last 30 years. We report in this work a theoretical study of the electronic structure of α-TiO based on generalized gradient approximation density functional calculations. Analysis of electron distribution changes induced by the creation of defects on the ideal rock-salt structure allows us to clarify the significant function played by both O and Ti ordered vacancies that work together on stabilization of the material. Stabilization of the monoclinic phase with respect to the cubic one involves a noticeable repolarization of the Ti 3d orbitals that simultaneously contribute to two cooperative mechanisms, (i) enhancement of the Ti-Ti bonding interactions through and around the oxygen vacancies, and (ii) electrostatic stabilization resulting from electron density accumulation in a oxygen vacancy (cation environment) together with electron density depletion in titanium vacancy (anionic environment

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

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

Reconfiguration Algorithm to Reduce Power Losses in Offshore HVDC Transmission Lines

The race to increase the efficiency and reduce the power losses in transmission systems has resulted in the substantial growth of high-voltage direct current (HVDC) transmission systems. Moreover, the interconnection of these transmission systems significantly increases their reliability. However, the control of these meshed grids is a key problem that usually is managed through the control of the VSCs in those grids, but the control of the VSC can be complemented with a reconfiguration algorithm. This paper proposes the use of the particle swarm optimization algorithm, in order to reconfigure meshed HVDC transmission systems and reduce losses. The proposed algorithm has been tested in the CIGRE benchmark grid, which comprises of several offshore wind farms that generate energy sent to the grid through several HVDC transmission lines. The results show that as the energy generation changes due to wind changes, the grid topology must be reconfigured in order to achieve the maximum efficiency. Doing this reconfiguration, power savings around 18–19% could be achieve

Complications Associated with Enteral Nutrition: CAFANE Study

[EN] Objectives: To determine the association between home enteral nutrition (HEN) administration modality and its complications in patients. Methods: This is a prospective multicenter longitudinal study including 15 Spanish hospitals, from April 2015 to March 2017. A 4-month follow-up period was conducted for each patient by home visit. The study subjects were adult patients who began their nutrient intake by tube feeding, known as HEN, during the recruitment period. The variables studied included the type and modality of HEN administration and its related complications, such as vomiting, regurgitation, constipation, diarrhea, and abdominal distention. Mechanical complications and bronchoaspiration were also evaluated. Descriptive variables were used for fitting. Results: The study consisted of 306 patients; 4 were lost due to death. Specific HEN modalities protected against constipation (odds ratio (OR) = 0.4) and regurgitation (OR = 0.4). The use of a nasogastric tube (NGT) resulted in a lower risk of diarrhea compared to percutaneous endoscopic gastrostomy (PEG) (OR = 0.4) but resulted in a higher risk of tube obstruction (OR = 7.4). The use of intermittent gravity versus bolus feeding was a protection factor against vomiting (OR = 0.4), regurgitation (OR = 0.3), constipation (OR = 0.3), diarrhea (OR = 0.4) and abdominal distension (OR = 0.4). The increase in the number of doses was a risk factor for the incidence of regurgitation (OR = 1.3). Conclusions: Gastrointestinal complications were the most frequent problems, but an adequate choice of the formula, route, feeding modality, number of doses, administration time, and dose volume can reduce the risk of these complications

De novo bone formation around implants with a surface based on a monolayer of multi‐phosphonate molecules. An experimental in vivo investigation

Objectives: The purpose of this experimental in vivo investigation was to evaluate the influence of modifying the implant surface by adding a monolayer of multiphosphonate molecules on the de novo bone formation and osseointegration. Material and Methods: The study was designed as an animal preclinical trial with intra-animal control and two healing periods, 2 and 8 weeks, to compare implants with an identical macro-design but with two different surfaces. Eight female Beagle dogs participated in the study. Control implants had a moderately rough surface combining sandblasting and acid etching; test implants had an additional monophosphonate layer covalently bonded to titanium. Histologic and radiographic (micro-CT) outcome variables were evaluated. Results: The first bone-to-implant contact (fBIC) was located more coronally for the test implants at the first (0.065 mm (95% CI = −0.82, 0.60)) and second healing milestones (0.17 mm (95% CI = −0.9, 0.55)). Most coronal BIC of the test implants displayed a higher percentage of osseointegration, +6.33% and +13.38% after 2 and 8 weeks, respectively; however, the differences were not statistically significant. The micro-CT examination did not show any BIC difference. Conclusions: The monophosphonate layer coating demonstrated clinical, histological, and radiographic results similar to the control surface