Effect of the Y(2)O(3)-ZrO(2) support composition on nickel catalyst evaluated in dry reforming of methane

Nickel catalysts with a load of 5 wt.% Ni, supported on pure ZrO(2) and ZrO(2) stabilized with 4 mol%, 8 mol% and 12 mol% of Y(2)O(3), were prepared by the polymerization method. The samples were characterized by X-ray diffraction (XRD), temperature-programmed reduction with hydrogen (TPR-H(2)), specific surface area (BET) and electronic paramagnetic resonance (EPR) and tested as catalysts for carbon dioxide reforming of methane. The XRD patterns showed the presence of the oxide precursor (NiO) and the tetragonal phase of a Y(2)O(3)-ZrO(2) solid solution. According to the TPR-H(2) analysis, the reduction of various NiO species was influenced by the composition of the support. Catalytic tests were conducted at 800 degrees C for 6 h, and the composition of the gaseous products and the catalytic conversion rate depended on the composition of the Y(2)O(3)-ZrO(2) solid solution and its influence on the supported NiO species. A direct relation was observed between the variation in the support, the nickel species supported on it and the performance in the catalytic tests. (C) 2008 Elsevier B.V. All rights reserved.

Tetragonal-cubic phase boundary in nanocrystalline ZrO(2)-Y(2)O(3) solid solutions synthesized by gel-combustion

By means of synchrotron X-ray powder diffraction (SXPD) and Raman spectroscopy, we have detected, in a series of nanocrystalline and compositionally homogeneous ZrO(2)-Y(2)O(3) solid solutions, the presence at room temperature of three different phases depending on Y(2)O(3) content, namely two tetragonal forms and the cubic phase. The studied materials, with average crystallite sizes within the range 7-10 nm, were synthesized by a nitrate-citrate gel-combustion process. The crystal structure of these phases was also investigated by SXPD. The results presented here indicate that the studied nanocrystalline ZrO(2)-Y(2)O(3) solid solutions exhibit the same phases reported in the literature for compositionally homogeneous materials containing larger (micro)crystals. The compositional boundaries between both tetragonal forms and between tetragonal and cubic phases were also determined. (C) 2011 Elsevier B.V. All rights reserved.

Carbon dioxide reforming of ethanol over Ni/Y(2)O(3)-ZrO(2) catalysts

Supported nickel catalysts of composition Ni/Y(2)O(3)-ZrO(2) were synthesized in one step by the polymerization method and compared with a nickel catalyst prepared by wet impregnation. Stronger interactions were observed in the formed catalysts between NiO species and the oxygen vacancies of the Y(2)O(3)-ZrO(2) in the catalysts made by polymerization, and these were attributed to less agglomeration of the NiO during the synthesis of the catalysts in one step. The dry reforming of ethanol was catalyzed with a maximum CO(2) conversion of 61% on the 5NiYZ catalyst at 800 degrees C, representing a better response than for the catalyst of the same composition prepared by wet impregnation. (C) 2009 Published by Elsevier B.V.

Theoretical study of the structure and stability of NbxOy, and NbxOy+ (x = 1-3; y = 2-5, 7, 8) clusters

Geometric, thermodynamic and electronic properties of cluster neutrals NbxOy and cations NbxOy+ (x = 1-3; y = 2-5, 7, 8) have been characterized theoretically. A DFT calculation using a hybrid combination of B3LYP with contracted Huzinaga basis sets. Numerical results of the relative stabilities, ionization potentials and band gaps of different clusters are in agreement with experiment. Analysis of dissociation channels supports the more stable building blocks as formed by NbO2, NbO2+ NbO3 and NbO3+ stoichiometries. The net atomic charges suggest that oxygen donor molecules can interact more favorably on central niobium atoms of cluster cations, while the interaction with oxygen acceptor molecules is more favorable on the terminal oxygen atoms of neutral clusters. A topological analysis of the electron localization function gradient field indicates that the clusters may be described as having a strong ionic interaction between Nb and O atoms. Published by Elsevier B.V. B.V.

Identification of allanite (Ce, Ca, Y)2(Al, Fe3+)3(SiO4)3OH found in marble from Chillagoe, Queensland using Raman spectroscopy

Samples of marble from Chillagoe, North Queensland have been analyzed using scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS) and Raman spectroscopy. Chemical analyses provide evidence for the presence of minerals other than limestone and calcite in the marble, including silicate minerals. Some of these analyses correspond to silicate minerals. The Raman spectra of these crystals were obtained and the Raman spectrum corresponds to that of allanite from the Arizona State University data base (RRUFF) data base. The combination of SEM with EDS and Raman spectroscopy enables the characterization of the mineral allanite in the Chillagoe marble.

Microwave ECR Plasma Assisted MOCVD of Y(2)O(3) Thin Films Using Y(tod)(3) Precursor and Their Characterization

Yttrium oxide (Y(2)O(3)) thin films were deposited by microwave electron cyclotron resonance (ECR) plasma assisted metal organic chemical vapour deposition (MOCVD) process using indigenously developed metal organic precursors Yttrium 2,7,7-trimethyl-3,5-octanedionates, commonly known as Y(tod)(3) which were synthesized by an ultrasound method. A series of thin films were deposited by varying the oxygen flow rate from 1-9 sccm, keeping all other parameters constant. The deposited coatings were characterized by X-ray photoelectron spectroscopy, glancing angle X-ray diffraction and infrared spectroscopy. Thickness and roughness for the films were measured by stylus profilometry. Optical properties of the coatings were studied by the spectroscopic ellipsometry. Hardness and elastic modulus of the films were measured by nanoindentation technique. Being that microwave ECR CVD process is operating-pressure-sensitive, optimum oxygen activity is very essential for a fixed flow rate of precursor, in order to get a single phase cubic yttrium oxide in the films. To the best of our knowledge, this is the first effort that describes the use of Y(tod)(3) precursor for deposition of Y(2)O(3) films using plasma assisted CVD process.

L'adquisició del catalá en una nena monolingüe dels 2 anys i 3 mesos als 3 anys i dos mesos. 'La adquisición del catalán en una niña monolingüe desde los 2 años y 3 meses hasta los 3 años y 2 meses'.

Establecer un orden en las flexiones catalanas que posibilite la comparación con otros estudios. La muestra la compone un solo individuo, niña de 2 años y 3 meses (al empezar la investigación, tres años y tres meses al terminarla), de ámbito socio-cultural medio, lengua materna catalana (residente en Badalona). La investigación lineal (12 meses) se articula alrededor de la bibliografía consultada y de las grabaciones (18 sesiones de 30-45 minutos) y análisis mediante el MLU de Brown, del lenguaje del sujeto de la muestra. Grabaciones magnetofónicas (18 grabaciones de 30, 45 minutos cada una). Bibliografía. MLU de Brown adaptado al catalán por Vilá (pero con las normas de cálculo de Brown). La adquisición de las flexiones es el resultado de un nivel determinado de complejidad cognitiva y lingüística, pero no se discierne en qué medida intervienen ambos factores. Para conocer cómo influyen los aspectos semánticos, sintácticos, pragmáticos y fonológicos en la adquisición del lenguaje son necesarios estudios transversales en niños bilingües.

NIR to visible up-conversion, infrared luminescence, thermoluminescence and defect centres in Y(2)O(3) : Er phosphor

Er(3+) doped Y(2)O(3) phosphor was prepared by the solution combustion method and characterized using powder x-ray diffraction and energy-dispersive analysis of x-ray mapping studies. Room temperature near infrared (NIR) to green up-conversion (UC) emissions in the region 520-580 nm {((2)H(11/2), (4)S(3/2)) -> (4)I(15/2)} and red UC emissions in the region 650-700 nm ((4)F(9/2) -> (4)I(15/2)) of Er(3+) ions have been observed upon direct excitation to the (4)I(11/2) level using similar to 972 nm laser radiation of nanosecond pulses. The possible mechanisms for the UC processes have been discussed on the basis of the energy level scheme, the pump power dependence as well as based on the temporal evolution. The excited state absorption is observed to be the dominant mechanism for the UC process. Y(2)O(3) : Er exhibits one thermally stimulated luminescence (TSL) peak around 367 degrees C. Electron spin resonance (ESR) studies were carried out to study the defect centres induced in the phosphor by gamma irradiation and also to identify the centres responsible for the TSL peak. Room temperature ESR spectrum of irradiated phosphor appears to be a superposition of at least three distinct centres. One of them (centre I) with principal g-values g(parallel to) = 2.0415 and g(perpendicular to) = 2.0056 is identified as O(2)(-) centre while centre II with an isotropic g-factor 2.0096 is assigned to an F(+)-centre (singly ionized oxygen vacancy). Centre III is also assigned to an F(+)-centre with a small g-factor anisotropy (g(parallel to) = 1.974 and g(perpendicular to) = 1.967). Additional defect centres are observed during thermal annealing experiments and one of them appearing around 330 degrees C grows with the annealing temperature. This centre (assigned to an F(+)-centre) seems to originate from an F-centre (oxygen vacancy with two electrons) and the F-centre appears to correlate with the observed TSL peak in Y2O3 : Er phosphor. The trap depth for this peak has been determined to be 0.97 eV from TSL data.

Biolabeling with nanoparticles based on Y(2)O(3):Nd(3+) and luminescence detection in the near-infrared

Neodymium based fluorescence presents several advantages in comparison to conventional rare earth or enzyme-substrate based fluorescence emitting sources (e.g.Tb, HRP). Based on this fact we have herein explored a Nd-based fluoroimmunoassay. We efficiently detected the presence of an oxidized low-density lipoprotein (oxLDL) in human plasma a well-known marker for cardiovascular diseases, which causes around 30% of deaths worldwide. Conventional fluoroimmunoassay uses time-resolved luminescence techniques, with detection in the visible range, to eliminate the fluorescence background from the biological specimens. By using an immunoassay based on functionalized Y(2)O(3):Nd(3+) nanoparticles, where the excitation and emission processes in the Nd(3+) ion occur in the near-infrared (NIR) region, we have succeeded in eliminating the interferences from the biological fluorescence background, avoiding the use of time-resolved techniques. This yields higher emission intensity from the Nd(3+)-nanolabels and efficient detection of anti-oxidized low-density lipoproteins (anti-oxLDL) by Y(2)O(3):Nd(3+)-antibody-antigen conjugation, leading to a novel biolabeling method. (C) 2010 Elsevier B.V. All rights reserved.

Mid- and near-infrared spectroscopic investigation of homogeneous cation distribution in MgxZnyAl(x+y)/2-layered double hydroxide (LDH)

In this report, a detailed FTIR fitting analysis was used to recognize Mg, Zn and Al homogeneous distribution in MgxZnyAl(x+y)/2-Layered double hydroxide (LDH) hydroxyl layer. In detail, OH-Mg2Al:OH-Mg3 ratios decreased from 95.2:4.8 (MIR) and 94.2:5.8 (NIR) to 58.9:41.1 (MIR) and 61.8:38.2 (NIR), when Mg:Al increased from 2.2:1.0 to 4.1:1.0 in MgAl-LDHs. These fitting results were similar with theoretical calculations of 94.3:5.7 and 59.0:41.0. In a further analysis of MgxZnyAl(x+y)/2-LDHs, OH bonded Zn2Mg, Zn2Al, MgZnAl, Mg2Al and Mg2Zn peaks were identified at 3420, 3430, 3445–3450, 3454 and 3545 cm-1, respectively. With the decrease of Mg:Zn from 3:1 to 1:3, metal-hydroxyl bands changed from OH-Mg2Al and MgZnAl (with a ratio of 49.4:50.6) to OH-MgZnAl and Zn2Al (with a ratio of 55.0:45.0). They were also similar with theoretical calculations of 47.6:52.4 and 54.6:45.4. As a result, these results show that there is an ordered cation distribution in MgxZnyAl(x+y)/2-LDH, and FTIR is feasible in recognizing this structure.

Pràctica 1 i 2 de la llicenciatura de Psicopedagogia. Bienni 2000-2002. 'Práctica 1 y 2 de la licenciatura de Psicopedagogía. Bienio 2000-2002'.

Material recopilatorio de información de utilidad para el alumnado de psicopedagogía durante las prácticas de la licenciatura. El material recoge los objetivos y finalidades de esta asignatura, los órganos y personas que intervienen y sus funciones, los criterios de calificación y evaluación, los seminarios y talleres que se imparten y las fichas de seguimiento de la asignatura en los dos años en que se distribuye.

PIAAR-R, niveles 1 y 2 : programa de intervención educativa para aumentar la atención y la reflexividad.

Este programa tiene como objetivo potenciar, fundamentalmente, los aspectos de reflexividad y atención en la ejecución de tareas en los niños-as de 7 a 14 años. Incluye: guía del profesor (común para ambos niveles), cuadernillo PIAAR-R 1 para el nivel 1 (incluye hoja de seguimiento), cuadernillo PIAAR-R 2 para el nivel 2 (incluye igualmente hoja de seguimiento) y 6 láminas ilustrativas para el nivel 1.

Contribuciones a la teoría de la atribución-indefensión : estudios 1 y 2.

Averiguar el valor de los modelos del desamparo aprendido y la teoría de la atribución, en su papel explicativo y de aportación de soluciones al problema del fracaso escolar. Incontrolabilidad: desamparo. Atribución causal: mediatizan aparición de síntomas. Muestreo por selección al azar. Primer estudio: estudiantes de COU de clase media-baja, número 52. Segundo estudio: estudiantes de COU de clase media-alta. Numero 65. Generalización: estudiantes de COU. Los sujetos fueron asignados al azar en un grupo de incontrolabilidad. Cada experimentador aplicaba las 3 pruebas a cada sujeto, una tras otra y sin intervalo entre ellas. Las pruebas fueron administradas individualmente y de forma simultánea por los 8 experimentadores previamente entrenados. Variables: VI= prueba de incontrolabilidad. VD= cuestionario atribucional. VA= prueba de anagramas. Prueba de incontrolabilidad: juego de cartulinas de colores y produce la situación de control y no control. Cuestionario atribucional: medir el estilo atribucional de los sujetos con respecto al éxito o al fracaso en la tarea previa. Prueba de anagramas: juego de cartulinas con letras, trata de medir el número de aciertos y de errores, las latencias post-error, latencia correcta y latencia total. Contraste de diferencia de medias. Primer estudio. A partir de los resultados obtenidos, cabe afirmar que las predicciones realizadas en base al modelo teórico han sido parcialmente corroboradas. Las influencias de factores metodológicos llevan a los autores a pensar en la necesidad de realizar una nueva contrastación. De todas formas concluyen diciendo que los sujetos tienden a mostrar los déficits cognitivos y motivacionales que el modelo de desamparo aprendido predice. Segundo estudio: Los resultados de este estudio no permiten concluir en ningún sentido siempre que se interpreten cautelosamente. Se se consideran independientemente del primer estudio, debería negarse la hipótesis y consecuentemente el modelo del que deriva. Después de realizar este estudio se registró que los sujetos sometidos a incontrolabilidad obtuvieron menos errores que los sujetos no sometidos a incontrolabilidad. Después de haber efectuado estos 2 estudios, los datos resultan contradictorios entre sí. Ante esta situación los autores creen que lo más adecuado es dejar en suspenso la validez del modelo. Deciden realizar un tercer estudio con un método similar, para ver si se obtiene alguna conclusión con respecto a las primigenias hipótesis y poder además investigar la causa de por qué el grupo de control tiene un menor rendimiento.