In-situ XANES experiments on Ni K-edge in mesoporous ZrO2-CeO2:Ni.

Ordered mesoporous ZrO2-CeO2 mixed oxides are potential candidates for catalytic applications. These systems, used as anodes in solid oxide fuel cells (SOFC), may lead to better performance of SOFCs, due to an enhancement on surface area, aiming to achieve a lower working temperature. The aim of this studies is to evaluate the reduction capacity of Ni2+ to Ni in ZrO2-x(mol)%CeO2 (x=50 and 90) samples impregnated with 60(wt.)%NiO. The synthesis was made with Zr and Ce chloride precursors, HCl aqueous solution, Pluronic P123, NH4OH to adjust the pH (3-4) and a teflon autoclave to perform a hydrothermal treatment (80oC/48h). The samples were dried and calcined, until 540oC in N2 and 4 hours in air. The NiO impregnation was made with an ethanol dispersion of Ni(NO3)£6H2O. The powder was calcinated in air until 350oC for 2 hours. Temperature-resolved XANES data at the Ni K-edge were collected at the DXAS beam line of the LNLS in transmission mode, using a Si(111) monochromator and a CCD detector. Sample preparation consisted of mixing »6mg of the powder samples with boron nitride and pressing into pellets. The data were acquired during an experiment of temperature programmed reduction (TPR) under a 5% H2/He until 600oC and mixtures of 20%CH4:5%O2/He, at temperatures from 400 to 600oC. All the reactions were monitored with a mass spectrometer. The data was analyzed with a linear combination fit of 2 standards for each valence number using Athena software. The Ni K-edge experiments demonstrated that for both contents of CeO2, NiO embedded in the porous zirconia-ceria matrix reduces at lower temperatures than pure NiO, revealing that the ZrO2-CeO2 support improves the reduction of impregnated NiO. Ni was oxidized to NiO after all reactions with methane and oxygen. Hydrogenated carbonaceous species were detected, but under reducing conditions, the hydrocarbon compounds are removed. The reaction of total oxidation of methane CH4:O2 (1:2 ratio) was observed at lower temperatures (around 400oC) for both samples.

Structural and textural studies of NiO impregnation in mesoporous ZrO2-CeO2 for catalysis applications.

The synthesis of zirconia-based ordered mesoporous structures for catalytic applications is a research area under development. These systems are also potential candidates as anodes in intermediate temperature solid oxide fuel cells (it-SOFC) due to an enhancement on their surface area [1-4]. The structural features of mesoporous zirconia-ceria materials in combination with oxygen storage/release capacity (OSC) are crucial for various catalytic reactions. The direct use of hydrocarbons as fuel for the SOFC (instead of pure H2), without the necessity of reforming and purification reactors can improve global efficiency of these systems [4]. The X-ray diffraction data showed that ZrO2-x%CeO2 samples with x>50 are formed by a larger fraction of the cubic phase (spatial group Fm3m), while for x<50 the major crystalline structure is the tetragonal phase (spatial group P42/nmc). The crystallite size of the cubic phase increases with increase in ceria content. The tetragonal crystallite size decreases when ceria content increases. After impregnation, the Rietveld analysis showed a NiO content around 60wt.% for all samples. The lattice parameters for the ZrO2 tetragonal phase are lower for higher ZrO2 contents, while for all samples the cubic NiO and CeO2 parameters do not present changes. The calculated densities are higher for higher ceria content, as expected. The crystallite size of NiO are similar (~20nm) for all samples and 55nm for the NiO standard. Nitrogen adsorption experiments revealed a broader particle size distribution for higher CeO2 content. The superficial area values were around 35m2/g for all samples, the average pore diameter and pore volumes were higher when increasing ceria content. After NiO impregnation the particle size distribution was the same for all samples, with two pore sizes, the first around 3nm and a broader peak around 10nm. The superficial area increased to approximately 45m2/g for all samples, and the pore volume was also higher after impregnation and increased when ceria content increased. These results point up that the impregnation of NiO improves the textural characteristics of the pristine material. The complementary TEM/EDS images present a homogeneous coating of NiO particles over the ZrO2-x%CeO2 support, showing that these samples are excellent for catalysis applications. [1] D. Y. Zhao, J. Feng, Q. Huo, N. Melosh, G. H. Fredrickson, B. F. Chmelka, G. D. Stucky, Science 279, 548-552 (1998). [2] C. Yu, Y. Yu, D. Zhao, Chem. Comm. 575-576 (2000). [3] A. Trovarelli, M. Boaro, E. Rocchini, C. de Leitenburg, G. Dolcetti, J. Alloys Compd. 323-324 (2001) 584-591. [4] S. Larrondo, M. A. Vidal, B. Irigoyen, A. F. Craievich, D. G. Lamas, I. O. Fábregas, et al. Catal. Today 107–108 (2005) 53-59.

Structural and reduction studies of ZrO2-CeO2:Ni for application in SOFC anodes.

Zirconia-ceria solid-solutions are extensively used as promoters for three-way catalysts, which are applied in the control of NOx, CO and hydrocarbons emission from automotive exhausts. In addition, thesematerials can be used as anodes in solid oxide fuel cells (SOFCs) operated with hydrocarbons. There areonly few works on ZrO2-CeO2 ordered mesoporous materials for catalytic applications and for anodes inSOFCs. The interest in these anodes relies on the fact that ZrO2-CeO2materials are mixed ionic/electronic conductors in reducing atmosphere and, therefore, fuel oxidation is produced on its entire surface, while it only occurs in the [anode/electrolyte/gas] interface (triple-phase boundaries) for electronic conductors. In this work, a synthesis method was developed usingZr and Ce chloride precursors, HCl aqueous solution, Pluronic P123 as the structure directing agent, NH4OH to adjust the pH (3-4) and a Teflon autoclave to perform hydrothermal treatment (80ºC/48 hours). The samples were dried and calcined, until 540ºC in N2and 4 hours in air. The X-ray diffraction data showed that powders with higher CeO2 content are formed by a larger fraction of the cubic CeO2 phase, while for a lower CeO2content the major crystalline structure is the tetragonal ZrO2 phase. The NiO impregnation was made with an ethanol dispersion of Ni(NO3)×6H2O. The resulting powder was calcinated in air until 350ºC for 2 hours. Temperature-programmed reduction (TPR) data were collected in order to evaluate the reduction profiles of ZrO2-x%CeO2:Ni samples in H2/Ar atmosphere. Results showed lower reduction temperatures for all ceria content in samples comparing to a NiO standard.

Size-dependent phase transitions in nanostructured zirconia-scandia solid solutions.

Size effects on phase stability and phase transitions in technologically relevant materials have received growing attention. Several works reported that metastable phases can be retained at room temperature in nanomaterials, these phases generally corresponding to the high-temperature polymorph of the same material in bulk state. Additionally, size-dependent shifts in solubility limits and/or in the transition temperatures for on heating or on cooling cycles have been observed. ZrO2-Sc2O3 (zirconia-scandia) solid solutions are known to exhibit very high oxygen ion conductivity provided their structure is composed of cubic and/or pseudocubic tetragonal phases. Unfortunately, for solid zirconia-scandia polycrystalline samples with typical micrometrical average crystal sizes, the high-conductivity cubic phase is only stable above 600°C. Depending on composition, three low-conductivity rhombo-hedral phases (β, γ and δ) are stable below 600°C down to room temperature, within the compositional range of interest for SOFCs. In previous investigations, we showed that the rhombohedral phases can be avoided in nanopowders with average crystallite size lower than 35 nm.

Seroprevalence and characterization of pestivirus infections in small ruminants and new world camelids in Switzerland

The seroprevalence of pestivirus infections in small ruminants and new world camelids in Switzerland was determined. In 5'059 sera of sheep from 382 herds, 503 sera of goats from 54 herds and 109 sera of alpacas and lamas from 53 herds, population prevalences of 16.1% (sheep), 25.4% (goats) and 4.6% (new world camelids), respectively, were found. In order to determine the source of infection, the serological reactions were further characterized by cross-neutralization against two pestiviruses representing the genotypes BVDV (Bovine Virus Diarrhea Virus)-1 and BDV (Border Disease Virus)-1. Based on the ratio of respective antibody titres, 56.1% of the infections in sheep were induced by a BDV-1, 12.9% by a BVDV-1 and 31.0% by an unresolved pestivirus. In goats, the corresponding proportions were 23.4%, 10.2% and 66.4%, respectively. In Alpacas and Lamas, the source of infection of 1 animal was BDV-1 and that of 4 seropositive animals remained unresolved. In view of the phylogenetic relationship between pestiviruses, the unresolved source of infection is most probably attributable to other pestivirus genotypes circulating in small ruminants and new world camelids. Due to the predominance of pestiviral genotypes other than BVDV-1, the risk of transmission of BVDV from persistently infected small ruminants and new world camelids to cattle appears to be moderate, apart from close direct contact in mixed animal husbandry, communal pasturing and grazing in the Alps.

Los derechos reproductivos: un debate necesario

Planned Parenthood Federation of America (PPFA) y el Centro de Promoción y Defensa de los Derechos Sexuales y Reproductivos (PROMSEX), como organizaciones auspiciantes del Primer Congreso Latinoamericano Jurídico sobre Derechos Reproductivos (Congreso Jurídico), quieren agradecer especialmente a Oscar Cabrera por sus aportaciones y su invaluable compromiso en coordinar, editar y escribir parte de esta publicación. Queremos expresar también nuestro profundo agradecimiento a las académicas que aportaron sus artículos sobre temas centrales para la región en relación al ejercicio de los derechos reproductivos. A ellas, Agustina Ramón Michell, Lidia Casas Becerra, Mercedes Cavallo y Claudia Ahumada, mil gracias. A las profesoras Rebecca Cook y Joanna Erdman y al profesor Bernard Dickens, nuestro sincero reconocimiento por su constante apoyo. Y un especial agradecimiento al Dr. Luis Lamas Puccio, ex vicedecano del Ilustre Colegio de Abogados de Lima, por su compromiso en la defensa de los derechos de las mujeres.

Entre el estigma y la ley. La interrupción legal del embarazo en el DF

Este artículo se origina en una investigación llevada a cabo mediante metodologías cualitativas de las ciencias sociales. Su objetivo es compartir algunos de los avances del estudio realizado en una clínica del Gobierno del Distrito Federal para explorar los efectos de la implantación de la interrupción legal del embarazo (ILE) en el personal que proporciona este servicio sanitario. Se subraya que además de disminuir los riesgos en la salud de las mujeres, la ILE con misoprostol impulsó un cambio de actitud de muchas usuarias, lo que expresa una disminución de los efectos negativos provocados por el estigma, aunque se sigue detectando la persistencia del estigma en las opiniones del personal sanitario. El fortalecimiento personal de las mujeres que se someten a este procedimiento legal se debe a que llevan a cabo el ejercicio pleno de un derecho.

Los finales de la educación básica en las cárceles en la provincia de Buenos Aires

La presente investigación tiene por tema la Educación Básica de Adultos y Jóvenes en las cárceles y en este universo se recorta el problema de investigación: Los fines que debería perseguir la Educación Básica de Adultos y Jóvenes en las cárceles de la Prov. de Bs. As. El tema propuesto resulta ser de gran interés debido a una serie de razones, que involucran la combinación de tres tópicos: la Educación, la Cárcel y los Derechos Humanos: - Porque se reconoce el Derecho a la Educación como Derecho Humano, a partir de la Normativa Internacional, pactos, convenciones y declaraciones surgidas en el ámbito de las Naciones Unidas y la Organización de Estados Americanos, que a su vez está establecido y asumido en la Constitución Nacional y Provincial, en la Ley Federal de la Educación y la Ley Provincial de Educación. - Porque la educación es un instrumento esencial para el desarrollo personal y la participación en la sociedad, en la medida que satisfaga las necesidades educativas de los sujetos de la acción educativa y sea una garantía real de los Derechos Humanos de las personas privadas de la libertad. El propósito de esta investigación se constituye de tres objetivos: - Reconocer la complejidad y la especificidad de la educación en el contexto de la cárcel. - Conocer con qué marcos conceptuales las escuelas con sede en cárceles plantean sus Proyectos Educativos Institucionales, Proyectos Curriculares y diagnósticos institucionales. - Reconocer que la Educación en Derechos Humanos, en tanto derecho y perspectiva pedagógica, es indispensable a la hora del diseño curricular en la Educación Básica en las cárceles. El marco teórico el enfoque descriptivo se pondrá en estado de situación el por qué y el para qué de la educación básica en la cárcel, basado en el análisis de la normativa referida al Derecho a la Educación como Derecho Humano de las personas privadas de la libertad y el análisis conceptual del enfoque educativo en el tratamiento penitenciario. Este enfoque cómo es la educación en el encierro en cuanto a la complejidad del acto educativo y las instituciones públicas involucradas, una aproximación a la caracterización del sujeto de la acción educativa en cuanto a su trayectoria de vida y el impacto del encierro en las dimensiones educativa, social y psicológica, y por último, se tratarán las perspectivas pedagógicas que se han desarrollado como tendencias en la Educación Básica de Adultos y en particular en el ámbito de las escuelas con sede en cárceles. En cuanto al enfoque prescriptivo, se presentarán los fines deseados para la educación básica de adultos en las cárceles, a partir del análisis de las perspectivas pedagógicas manifestadas en los Proyectos Educativos Institucionales y los proyectos curriculares de las EGBA con sede en cárceles, la propuesta concreta de fines y el análisis de la educación en y para los DDHH como un derecho y una perspectiva pedagógica indispensable y prioritaria a la hora de pensar los fines de la educación básica en cárceles