Grain boundary conductivity of high purity neodymium-doped ceria nanosystem with and without the doping of molybdenum oxide

Solid solutions of Ce1-xNdxO2-x/2 (0.05 <= x <= 0.2) and (Ce1-xNdx)(0.95)MO0.05O2-delta (0.05 <= x <= 0.2) have been synthesized by a modified sol-gel method. Both materials have very low content of SiO2 (similar to 27 ppm). Their structures and ionic conductivities were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM) and electrochemical impedance spectroscopy (M). The XRD patterns indicate that these materials are single phases with a cubic fluorite structure. The powders calcined at 300 degrees C with a crystal size of 5.7 nm have good sinterability, and the relative density could reach above 96% after being sintered at 1450 degrees C. With the addition Of MoO3, the sintering temperature could be decreased to 1250 degrees C. Impedance spectroscopy measurement in the temperature range of 250-800 degrees C indicates that a sharp increase of conductivity is observed when a small amount of Nd2O3 is added into ceria, of which Ce0.85Nd0.15O1.925 (15NDC) shows the highest conductivity. With the addition of a small amount Of MoO3, the grain boundary conductivity of 15NDC at 600 degrees C increases from 2.56 S m(-1) to 5.62 S m(-1).

Ce_(1-x)Ca_xO_(2-x)的溶胶-凝胶法的合成及其性质

用溶胶 -凝胶法合成了 Ce1-x Cax O2 -x(x=0～ 0 .3 5 )系列固体电解质 ,系统地研究了其晶体结构随Ca O含量的变化关系 .XRD测试表明 ,该体系于 1 60℃即形成萤石结构纯相 .高温 XRD表明 ,从室温至80 0℃ ,Ce1-x Cax O2 -x(x=0～ 0 .3 5 )未出现结构相变 .此法合成温度远低于传统的高温固相合成法和水热合成法的温度 .合成物的颗粒小 ,粒度均匀 .在 1 3 0 0℃即可烧结成高致密度样品 .XPS测试表明 ,掺杂 Ca O后吸附氧浓度明显增大 ,氧空位增多 ,电导率和氧离子迁移数增大 ,改善了 Ce O2 基固体电解质的性能 .

Un análisis comparativo de los sistemas curricular, metodológico y de evaluación, en el área de Matemáticas entre España y los países francófonos europeos : implicaciones para el rendimiento académico.

Propuesta de un modelo de enseñanza de las Matemáticas centrado en el desarrollo cognitivo de los alumnos, justificado teóricamente desde las aportaciones de la Pedagogía y la Psicología y defendido desde el marco legal de la reforma del Sistema Educativo. La segunda parte del estudio pretende ofrecer una visión comparada de las propuestas metodológicas españolas y francófonas cuya identificación con el marco teórico del modelo propuesto es importante. Valoración comparada de ambas propuestas, bajo los mismos supuestos y en referencia al desarrollo filogenético del cocnocimiento matemático. Propuestas educativas ofrecidas por las editoriales Anaya y Santillana, para los cursos de primero a sexto de Primaria (6-12 años) y de la editorial Nathan para los cursos CP, CE1, CE2, CM1 y CM2 y la editorial Office Romand des Editions et du Matériel Scolaire, para los cursos de primero a sexto, ésta última, suiza, sólo se comparó en términos generales con las propuestas española y francesa. Marco teórico que justifica el modelo propuesto (tipos de conocimiento, modelos de enseñanza y evaluación). Seguido al marco teórico general se especifican las cuestiones tratadas en él, al campo matemático, realizando una introducción histórica al conocimiento matemático (modelos de enseñanza de las Matemáticas y la evaluación en Matemáticas), para pasar al análisis comparado de los materiales de las editoriales de textos escolares españoles y francófonos (Francia y Suiza). En la sección tercera de la investigación (p. 2355 y ss.), se recogen las conclusiones. 1. Lo más destacable de la propuesta metodológica de las editoriales Anaya y Santillana es: la proximidad entre el campo numérico disponible y su tratamiento operativo, la proximidad entre las operaciones inversas, la incorporación de la aplicación de la noción a la resolución de problemas o situaciones, como un momento más de su proceso de adquisición y la organización de la secuencia de aprendizaje y la concreción de su desarrollo; 2. La característica esencial de la propuesta metodológica de la Editorial Office Romand des Editions et du Matériel Scolaires (Suiza, Neuchatel), consiste en una concepción del aprendizaje basada en el protagonismo del alumno que, en situación colectiva, de equipo o individualmente, se enfrenta a la interpretación de una realidad sobre la que ensayar estrategias, a la comparación y justificación de procesos y resultados y a la búsqueda de formas de ampliación o modificación de dicha realidad; 3. No existe un isomorfismo entre los contenidos de las propuestas españolas y francófonas y que su estructuración es esencialmente diferente, lo que justifica el relativo desfase entre los contenidos que configuran los cursos españoles y franceses. Más próximas están, en ambos aspectos, las propuestas españolas entre sí. Conviene considerar la importancia de las Matemáticas en el desarrollo cognoscitivo del sujeto: el cocnocimiento matemático no es fáctico sino formal, consiste en un todo formado por la representación de los objetos físicos y de la propia acción realizada sobre ellos, es decir, consiste en la interacción del sujeto con la realidad. La continuidad y el desarrollo del conocimiento no serán posibles si el sujeto no dispone de esquemas desde los que interpretar la realidad y en los que integrar la representación alcanzada, bien porque los esquemas sean en sí mismos inadecuados, bien porque los objetos de conocimiento no se adecúen a los esquemas.

Síntese e caracterização de NiO-CGO para anodo e eletrólitos sólidos e base de Céria para SOFC

The direct use of natural gas makes the Solid Oxide Fuel Cell (SOFC) potentially more competitive with the current energy conversions technologies. The Intermediate Temperature SOFC (IT-SOFC) offer several advantages over the High Temperature SOFC (HT-SOFC), which includes better thermal compatibility among components, fast start with lower energy consumption, manufacture and operation cost reduction. The CeO2 based materials are alternatives to the Yttria Stabilized Zirconia (YSZ) to application in SOFC, as they have higher ionic conductivity and less ohmic losses comparing to YSZ, and they can operate at lower temperatures (500-800°C). Ceria has been doped with a variety of cations, although, the Gd3+ has the ionic radius closest to the ideal one to form solid solution. These electrolytes based in ceria require special electrodes with a higher performance and chemical and termomechanical compatibility. In this work compounds of gadolinia-doped ceria, Ce1-xGdxO2-δ (x = 0,1; 0,2 and 0,3), used as electrolytes, were synthesized by polymeric precursors method, Pechini, as well as the composite material NiO - Ce0,9Gd0,1O1,95, used as anode, also attained by oxide mixture method, mixturing the powders of the both phases calcinated already. The materials were characterized by X ray diffraction, dilatometry and scanning electronic microscopy. The refinement of the diffraction data indicated that all the Ce1-xGdxO2-δ powders were crystallized in a unique cubic phase with fluorite structure, and the composite synthesized by Pechini method produced smaller crystallite size in comparison with the same material attained by oxide mixture method. All the produced powders had nanometric characteristics. The composite produced by Pechini method has microstructural characteristics that can increase the triple phase boundaries (TPB) in the anode, improving the cell efficiency, as well as reducing the mass transport mechanism effect that provokes anode degradation

Condutividade elétrica da solução nutritiva e produção de alface em hidroponia

A variação da condutividade elétrica da solução nutritiva altera a absorção de água e nutrientes pelas plantas, interferindo no metabolismo e, consequentemente, na produção das mesmas. Este trabalho, conduzido no período de agosto a outubro de 1999, avaliou o efeito da condutividade elétrica (CE) sobre a produção e desenvolvimento de alface americana de cabeça crespa, cultivar Ryder em hidroponia. As tendências de variação da condutividade elétrica do meio nutritivo, durante o desenvolvimento da alface, foram também avaliadas. Foi utilizado o delineamento inteiramente casualizado com seis repetições e três tratamentos, constituídos pelas condutividade elétricas: CE1= 1,46, CE2= 2,46 e CE3= 4,21 (± 0,24) mS cm-1. O diâmetro e altura da cabeça e peso seco da raiz não foram influenciados pelas condutividades elétricas da solução nutritiva. Os maiores pesos do material fresco e seco foram conseguidos com CE 2,46 (± 0,24) mS cm-1. Todos os tratamentos apresentaram a tendência de diminuição da condutividade elétrica, durante o cultivo da alface verificando-se que a condutividade elétrica teve influência sobre as características de produção da alface americana.

Desenvolvimento de mudas de Tabeluia chrysotricha em função de substratos e de soluções de fertirrigação

The work aimed to study the development of Tabebuia chrysotricha Standl. seedlings injunction of different substrate and different fertilization solutions. To compose the substrate it was used fibrous and granulated coconut fiber obtaining the following treatments: S1- 100% fibrous, S2- 60% fibrous and 40% granulated, S3- 40% fibrous and 60% granulated and S4- 100% granulated. The basis fertilization was the same for all treatments and the solutions of fertilization varied in order to obtain solutions with the following electric conductivities: EC1- 1.06 dS m(-1), EC2- 2.12 dS m(-1), EC3- 3.2 dS m(-1) and EC4- 4.25 dS m(-1). The propagative material was sowed directly in plastic containers (120mL) with the respective substrates. The fertilization was received through sub irrigation once a week, until the seedlings reached 20cm of height approximately. The chemical analyses of the substrate (EC and pH), through aqueous extraction method 1:1.5 (1 substrate: 1.5 deionized water), the analyses of aerial part height, stein diameter and pairs true leaves number, as well as the weight of total dry, matter, were accomplished each 15 days. In almost every analysis, the substrate with granulated coconut fiber, as well as the smallest EC (1.06 e 2.12 dS m(-1)) of fertilization solutions,formed seedlings with higher averages, indicating faster growth. In the conditions of this experiment, the production of T. chrysotricha seedlings was better in granulated coconut fiber substrate and fertilizer solutions with EC of 1.06 dS m(-1), appreciating the estimated characteristics.

Impactos do estresse salino e da cobertura morta nas características químicas do solo e no desenvolvimento do amaranto

Availability of good quality water has been reduced vertiginously, over the last decade, in the world. In some regions, the water resources have high concentration of the dissolved salts, these characteristics of the water make it s use impossible. Water quality can be a limitation for irrigated agriculture, principally in regions of arid or semiarid climate where the water resources are generally saline and are exposed at high evaporation ratio. For that reason, precipitation of the salts occurs near the soil surface and those salts themselves cumulate in the vegetal tissue, reducing the soil fertility and crop production. The adoption of tolerant crop to the water salinity and soil salinity, adaptable to the climatic conditions is other emergent necessity. This work had the goal of studying the effects of four salinity levels of the irrigation water salinity and use of mulch, dried leaves of Forest mangrove (Acacia mangiumWilld), in cultivated soil with amaranth (Amaranthus cruentus, BRS Alegria variety), in greenhouse. It was utilized the transplant of plants to PVC columns, containing 30 kg of silty loam soil, 10 days after emerging, with space of 50 x 50 cm between lines. Treatments were composed by combination of four levels of salinity (0.147; 1.500; 3.000 e 4.500 dS m-1), obtained by addition NaCl (commercial) to irrigation water and soil with and without protection, by mulch. A factorial system 4 x 2 was used with four repetitions, totalizing 32 parcels. The concentrations of nutrients in soil solution have been evaluated, in the dry matter of the vegetal tissue (roots, stem, leaves and raceme residue), at the end of the vegetative cycle. The use of soil protection reduced time for the beginning inflorescence of plants, at the same time, the increase of the salinity delayed this phase of amaranth development. The use of the mulch effectively increased the height, stem diameter, area of the larger leaf, humidity and dry matter content and amaranth grain production. The vegetal species showed salinity tolerance to experimented levels. The adopted treatments did not affect the pH values, exchangeable cation contents, electrical conductivity of soil solution (EC1:5) and saturated extract (ECSE), and Ca+2, Mg+, Fe+2 and Mn+2 contents, in the soil solution. The increase of the salinity concentration in the irrigation water inhibited the mineralization process of the organic matter (OM) and, consequently, the efficiency in the it´s utilization by plants, at the same time, produced increase in the values of the exchangeable sodium percentage (ESP), sodium adsorption ratio (SAR) and potassium adsorption ratio (PAR), in the soil solution. Therefore, the use of the mulch did not affect the first three parameters. The protein and nutrient contents: K+, Ca+2, P, Mg+2 e Cu+2, in amaranth grains, were improved by tillage condition. The raceme residues showed chemical/nutritional composition that makes advantageous its application in animal ration. In this context, it follows that amaranth tolerate the saline stress, of the irrigation water, until 4.500 dS m-1, temperature and relative humidity of the air predominant in the experimental environment

Effect of selective cyclooxygenase-2 inhibition on the development of ligature-induced periodontitis in rats

Background: the purpose of this study was to evaluate the effect of a selective cyclooxygenase-2 inhibitor on the progression of alveolar bone loss in an experimental periodontitis model in rats.Methods: One hundred eighty (180) Wistar rats were separated into 3 experimental groups. Cotton ligatures were placed at the gingival margin level of lower right first molars. The rats were randomly assigned to one of the following groups that received: a daily oral dose of 10 mg/kg body weight of celecoxib (Ce1); 20 mg/kg body weight of celecoxib (Ce2); or 10 ml/kg of saline solution (C). Serum levels of celecoxib and white blood cell count were determined. Standardized digital radiographs were taken after sacrifice at 3, 5, 10, 18, and 30 days to measure the amount of bone loss around the mesial root surface of the first molar tooth in each rat.Results: Two-way analysis of variance (ANOVA) indicated that groups treated with celecoxib had significantly less bone loss compared to controls (P <0.0001) and that there was a significant interaction between treatment with celecoxib and time (P <0.03). Post-hoc comparisons showed that in both groups treated with celecoxib, the bone loss became significant only after 10 days of ligature placement, while in the control group it was already significant after 5 days. However, differences in mean bone loss between control and Ce1 were significant only at 18 days and, between control and Ce2, at 5 and 18 days. There was no significant difference in bone loss among experimental groups at the end of the experimental period.Conclusion: These data provide evidence that systemic therapy with celecoxib can modify the progression of experimentally induced periodontitis in rats.

Efeito do celecoxib sobre o desenvolvimento de doença periodontal induzida em ratos

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Unidades fraseológicas especializadas: colocações e colocações estendidas em contratos sociais e estatutos sociais traduzidos no modo juramentado e não-juramentado

Pós-graduação em Estudos Linguísticos - IBILCE

CuO-CeO2 catalysts synthesized in one-step: Characterization and PROX performance

PEM fuel cells seem to be the most affordable and commercially viable hydrogen-based cells, the biggest challenge being to obtain CO-free H-2 (<100 ppm) as the fuel. In this study, the use of CuO-CeO2 catalysts in preferential oxidation of CO to obtain CO-free H-2 (PROX reaction) was investigated. Ce1-xCuxO2 catalysts, with x (mol%) = 0, 0.01, 0.03, 0.05 and 0.10, were synthesized in one-step by the polymeric precursor method, to obtain a very fine dispersion and strong metal-support interaction, to favor active copper species and a preference for the PROX reaction. The results obtained from catalyzed reactions and characterization of the catalysts by XRD, Rietveld refinement, BET surface area, UV-Vis and TPR, suggest that this one-step synthesis method gives rise to catalysts with copper species selective for the PROX reaction, which reaches a maximum rate on Ce0.97Cu0.03O2 catalyst. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Nitrous oxide emissions from European agriculture - an analysis of variability and drivers of emissions from field experiments

Nitrous oxide emissions from a network of agricultural experiments in Europe were used to explore the relative importance of site and management controls of emissions. At each site, a selection of management interventions were compared within replicated experimental designs in plot-based experiments. Arable experiments were conducted at Beano in Italy, El Encin in Spain, Foulum in Denmark, Logarden in Sweden, Maulde in Belgium CE1, Paulinenaue in Germany, and Tulloch in the UK. Grassland experiments were conducted at Crichton, Nafferton and Peaknaze in the UK, Godollo in Hungary, Rzecin in Poland, Zarnekow in Germany and Theix in France. Nitrous oxide emissions were measured at each site over a period of at least two years using static chambers. Emissions varied widely between sites and as a result of manipulation treatments. Average site emissions (throughout the study period) varied between 0.04 and 21.21 kg N2O-N ha−1yr−1, with the largest fluxes and variability associated with the grassland sites. Total nitrogen addition was found to be the single most important deter- minant of emissions, accounting for 15 % of the variance (using linear regression) in the data from the arable sites (p<0.0001), and 77 % in the grassland sites. The annual emissions from arable sites were significantly greater than those that would be predicted by IPCC default emission fac- tors. Variability of N2O emissions within sites that occurred as a result of manipulation treatments was greater than that resulting from site-to-site and year-to-year variation, highlighting the importance of management interventions in contributing to greenhouse gas mitigation

La activación de conocimientos previos (ACP): Una estrategia de comprensión lectora

El objetivo de este artículo es presentar un estudio sobre la activación de conocimientos previos como una de las estrategias que los docentes utilizan para trabajar la comprensión lectora con alumnos de segundo y tercero de Educación Primaria. Los datos que se analizan han sido recogidos mediante observaciones realizadas, durante dos cursos, en diversas aulas de la geografía española. Como resultado del análisis, se ofrece una panorámica de las maneras de activar conocimientos previos y cómo se distribuyen en función del tipo de texto y de la finalidad de la lectura.

Síntese e caracterização de NiO-CGO para anodo e eletrólitos sólidos e base de Céria para SOFC

The direct use of natural gas makes the Solid Oxide Fuel Cell (SOFC) potentially more competitive with the current energy conversions technologies. The Intermediate Temperature SOFC (IT-SOFC) offer several advantages over the High Temperature SOFC (HT-SOFC), which includes better thermal compatibility among components, fast start with lower energy consumption, manufacture and operation cost reduction. The CeO2 based materials are alternatives to the Yttria Stabilized Zirconia (YSZ) to application in SOFC, as they have higher ionic conductivity and less ohmic losses comparing to YSZ, and they can operate at lower temperatures (500-800°C). Ceria has been doped with a variety of cations, although, the Gd3+ has the ionic radius closest to the ideal one to form solid solution. These electrolytes based in ceria require special electrodes with a higher performance and chemical and termomechanical compatibility. In this work compounds of gadolinia-doped ceria, Ce1-xGdxO2-δ (x = 0,1; 0,2 and 0,3), used as electrolytes, were synthesized by polymeric precursors method, Pechini, as well as the composite material NiO - Ce0,9Gd0,1O1,95, used as anode, also attained by oxide mixture method, mixturing the powders of the both phases calcinated already. The materials were characterized by X ray diffraction, dilatometry and scanning electronic microscopy. The refinement of the diffraction data indicated that all the Ce1-xGdxO2-δ powders were crystallized in a unique cubic phase with fluorite structure, and the composite synthesized by Pechini method produced smaller crystallite size in comparison with the same material attained by oxide mixture method. All the produced powders had nanometric characteristics. The composite produced by Pechini method has microstructural characteristics that can increase the triple phase boundaries (TPB) in the anode, improving the cell efficiency, as well as reducing the mass transport mechanism effect that provokes anode degradation

Qualidade química e física do solo sob vegetação arbórea nativa e pastagens no pantanal Sul-Mato-Grossense.

A busca por aumento de produtividade da pecuária pantaneira tem motivado o desmatamento de áreas florestadas para a implantação de pastagem cultivada, gerando preocupação quanto à sustentabilidade dos recursos naturais. Para estudar alguns aspectos de uso do solo no Pantanal Sul-Mato-Grossense, este trabalho teve por objetivo avaliar as alterações nos atributos químicos e físicos do solo em razão da conversão da vegetação arbórea nativa em pastagem cultivada, bem como da submissão da pastagem nativa ao sistema de pastejo contínuo. Os ambientes de estudo consistiram de três remanescentes de vegetação arbórea nativa, representadas por uma floresta semidecídua (FN) e dois cerradões (CE1 e CE2), três pastagens de Brachiaria decumbens com 27, 26 e 11 anos de formação, implantadas em substituição a FN, CE1 e CE2, respectivamente, e uma pastagem nativa caracterizada pela predominância de Mesosetum chaseae e Axonopus purpusii, submetida a três diferentes sistemas de pastejo (contínuo e sem pastejo por 3 e 19 anos). Amostras de solo, deformadas e indeformadas, foram coletadas em cada ambiente de estudo, nas profundidades de 0?10 e 10?20 cm, com três repetições. A substituição da vegetação arbórea nativa por pastagem cultivada e o sistema de pastejo contínuo da pastagem nativa determinaram redução da qualidade química do solo, evidenciada principalmente por perdas de matéria orgânica do solo, notadamente na profundidade de 0?10 cm. Embora a qualidade física do solo também tenha apresentado tendência à redução nas pastagens cultivada e nativa sob pastejo contínuo, a densidade do solo, porosidade total, macroporosidade, microporosidade, condutividade hidráulica do solo saturado eresistência do solo à penetração não atingiram valores considerados limitantes ao desenvolvimento do sistema radicular.