Effect of Sodium Ascorbate on Tag Formation in Bleached Enamel

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

Spatial and temporal patterns and their influence on fish community at Itupararanga Reservoir, Brazil

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

Effect of precursor solution on the formation of perovskite phase of Pb(Mg-1/Nb-3(2/3))O-3 thin films

Precursor solutions for Pb(Mg1/3Nb2/3)O-3 (PMN) synthesis were obtained by Pechini's method. The influence of the concentration of organic materials on the phase formation has been studied. For this purpose, PMN solutions were prepared with different precursors and were characterized by thermogravimetric and differential thermal analysis. The obtained solutions were deposited onto a Si (100) substrate by dip coating and pre-treated in a hot plate at 300 degreesC for 1 h. The films were annealed at 600, 700, 800 and 900 degreesC for 1 h and characterized by X-ray diffraction. The perovskite phase was formed after annealing at 600 and 700 degreesC when the solution of PMN was prepared with a lower amount of organic material and starting with mobium oxide. By increasing the temperature to 800 or 900 degreesC, only the formation of pyrochlore phase was observed. With the solution prepared from mobium ethoxide, only the presence of pyrochlore phase was observed independently of the annealing temperature. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Addition of sedimentary rock to kaolinitic clays: influence on sintering process

Foram avaliadas, durante o processo de sinterização, as propriedades mecânicas de peças cerâmicas a base de argila com adição de rocha sedimentar. Foram preparados corpos de prova com 0, 20, 40, 60 e 80% em peso de rocha adicionada ao material argiloso. As peças foram sinterizadas nas temperaturas de 500, 800, 900, 1000, 1100 e 1200 °C e, posteriormente, submetidas à análise de difração de raios X e a ensaios tecnológicos Os resultados de difração de raios X mostram que a rocha sedimentar apresenta argilominerais micáceos enquanto o material argiloso possui a caulinita como fase principal. Técnicas de análises térmicas e difração de raios X das diferentes misturas mostram reações que indicam transformação (inversão do quartzo), decomposição (perda de hidróxidos) e formação de fase (mulita) durante o aquecimento das amostras. Os ensaios tecnológicos mostram que a adição da rocha sedimentar melhora algumas propriedades do material sinterizado, auxiliada pela presença de fundentes. Entretanto, a presença de quartzo na rocha dificulta a formação da fase mulita. A formação de novas fases e as transformações ocorridas no aquecimento e resfriamento das amostras ajuda explicar as propriedades tecnológicas dos materiais cerâmicos.

Catalysis and temperature dependence on the formation of ZnO nanoparticles and of zinc acetate derivatives prepared by the sol-gel route

The chemical and structural nature of powders prepared from the zinc acetate-derived precursor using the sol-gel route is discussed. The influence of the synthesis temperature and of the hydrolytic catalyst on the structural features of the powder is focused on the basis of X-ray powder diffraction (XRPD) and extended X-ray absorption fine structure (EXAFS) measurements and complemented with density and thermoanalysis (TG-DTA) results. EXAFS and XRPD results show that no-washed nanoparticulate powders are composed of a mixture of ZnO (wurtzite), zinc acetate, and zinc hydroxyacetate. The latter has a layered structure typical of hydroxy double salts (HDS). The main component of no-washed powders is always unreacted zinc acetate solid but the relative amount of the zinc-based compounds depends on the nature of the hydrolytic catalyst, hydrolysis ratio, and of synthesis temperature. According to the proportion of the three zinc-based compounds, three families of powders could be distinguished. The amount of ZnO nanoparticles (1.6 +/- 0.6 nm) decreases as the synthesis temperature increases, as the hydrolysis ratio decreases, or by changing from basic to acid catalysis. This finding suggests that the formation of zinc compounds is controlled by the equilibrium between hydrolysis-condensation and complexation-reprecipitation reactions.

Hydrogen influence on gallium arsenide thin films prepared by rf-magnetron sputtering technique

We investigate the effect of the hydrogen intentional incorporation on the structural properties of the amorphous gallium arsenide prepared by rf-magnetron sputtering technique. The properties of the non-hydrogenated films are: band gap of 1.4 eV (E-04), Urbach energy of 110 meV, stoichiometric composition ([As]/[Ga] = 0.50), and dark conductivity of about 3.2 x 10(-5) (Omega.cm)(-1). Hydrogen was incorporated in the films by the introduction of an electronically controlled H-2 flux during deposition, keeping constant the other deposition parameters. It was observed that small hydrogen incorporation produces a great change in the structural properties of the films. The main changes result from the formation of GaAs nanocrystals with mean sizes of about 7 nm into the amorphous network.

Effects of environmental colour on growth of Nile tilapia, Oreochromis niloticus (Linnaeus, 1758), maintained individually or in groups

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Relief influence on the spatial distribution of the Atlantic Forest cover on the Ibiúna Plateau, SP

Several studies suggest that, on a large scale, relief conditions influence the Atlantic Forest cover. The aim of this work was to explore these relationships on a local scale, in Caucaia do Alto, on the Ibiúna Plateau. Within an area of about 78 km2, the distribution of forest cover, divided into two successional stages, was associated with relief attribute data (slope, slope orientation and altitude). The mapping of the vegetation was based on the interpretation of stereoscopic pairs of aerial photographs, from April 2000, on a scale of 1:10,000, while the relief attributes were obtained by geoprocessing from digitalized topographic maps on a scale of 1:10,000. Statistical analyses, based on qui-square tests, revealed that there was a more extensive forest cover, irrespective of the successional stage, in steeper areas (>10 degrees) located at higher altitudes (>923 m), but no influence of the slope orientation. There was no sign of direct influence of relief on the forest cover through environmental gradients that might have contributed to the forest regeneration. Likewise, there was no evidence that these results could have been influenced by the distance from roads or urban areas or with respect to permanent preservation areas. Relief seems to influence the forest cover indirectly, since agricultural land use is preferably made in flatter and lower areas. These results suggest a general distribution pattern of the forest remnants, independent of the scale of study, on which relief indirectly has a strong influence, since it determines human occupation.

Evaluation of weather influence on mechanical and viscoelastic properties of polyetherimide/carbon fiber composites

In order to investigate how environmental degradation affects the mechanical and thermal performance of polyetherimide/carbon fiber laminates, in this work different weathering were conducted. Additionally, dynamic mechanical analysis, interlaminar shear strength tests and non-destructive inspections were performed on this composite before and after being submitted to hygrothermal, UV radiation and thermal shock weathering. According to our results, hygrothermally aged samples had their glass transition temperature and elastic and storage moduli reduced by plasticization effect. Photooxidation, due to UV radiation exposure, occurred only on the surface of the laminates. Thermal shock induced a reversible stress on the composite's interface region. The results revealed that the mechanical behavior can vary during weather exposure but since this variation is only subtle, this thermoplastic laminate can be considered for high-performance applications, such as aerospace. © The Author(s) 2013.

Ecosystem services and urban vegetation coverage in Belém: the influence on noise pollution, air pollution and climate regulation

A ligação entre as zonas urbanas e as questões ambientais ficam mais próximas na medida em que cresce a conscientização global de conservar, melhorar e valorizar os serviços ambientais prestados pela natureza para a sustentabilidade da vida, dentro e fora da cidade. Cobertura vegetal (ou cobertura verde) está dentre as principais fontes de tais serviços. Uma vez que o processo de urbanização se mostra irreversível e os problemas ambientais urbanos se alastram em tamanho e extensão, a presença do verde está diretamente relacionada aos indicadores de qualidade de vida urbana. Como reflexo do processo de urbanização, a cidade de Belém perdeu uma grande porcentagem de seus ecossistemas naturais, de modo que este trabalho se concentrou em analisar alguns serviços ecossistêmicos—qualidade do ar, poluição do ar e regulação do clima - fornecidos pela qualidade e pela quantidade de cobertura vegetal local, considerando as alterações na distribuição espaço-temporal, em três distritos administrativos. Um marco teórico foi construído e analisado; a cobertura vegetal foi calculada, utilizando-se NDVI e Cobertura Vegetal Fracional em imagens do LANDSAT 5, ao longo de um período de 23 anos. A partir de uma proposta de escala mais detalhada de NDVI, análises quantitativas e qualitativas da cobertura verde evidenciaram perda significativa de cobertura muito densa, densa, moderada e aumento de áreas de pouca ou nenhuma vegetação. Ademais, lesão das áreas verdes sinalizou tendências de aumento da poluição do ar, da poluição sonora e da temperatura. A carência de dados relacionados ao meio ambiente não deixa dúvida sobre a urgência de investimento nos serviços ambientais provenientes da cobertura vegetal, para a sustentabilidade urbana em Belém, cujos cenários previstos são de drásticas perdas de área verde. Mais pesquisas e iniciativas de instituições públicas e privadas são necessárias para a contribuição aos serviços ambientais em Belém e, consequentemente, ao bem-estar público.

Environmental influences on antibody-enhanced dengue disease outcomes

Because an enriched environment (EE) enhances T-cell activity and T-lymphocytes contribute to immunopathogenesis during heterologous dengue virus (DENV) infections, we hypothesised that an EE increases dengue severity. To compare single serotype (SS) and antibody-enhanced disease (AED) infections regimens, serial intraperitoneal were performed with DENV3 (genotype III) infected brain homogenate or anti-DENV2 hyperimmune serum followed 24 h later by DENV3 (genotype III) infected brain homogenate. Compared AED for which significant differences were detected between the EE and impoverished environmental (IE) groups (Kaplan-Meyer log-rank test, p = 0.0025), no significant differences were detected between the SS experimental groups (Kaplan-Meyer log-rank test, p = 0.089). Survival curves from EE and IE animals infected with the AED regimen were extended after corticoid injection and this effect was greater in the EE than in the IE group (Kaplan-Meyer log-rank test, p = 0.0162). Under the AED regimen the EE group showed more intense clinical signs than the IE group. Dyspnoea, tremor, hunched posture, ruffled fur, immobility, pre-terminal paralysis, shock and death were associated with dominant T-lymphocytic hyperplasia and presence of viral antigens in the liver and lungs. We propose that the increased expansion of these memory T-cells and serotype cross-reactive antibodies facilitates the infection of these cells by DENV and that these events correlate with disease severity in an EE.

Interstitial oxygen's influence on the corrosion behavior of Ti-9Mo alloys

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Environmental effects on viscoelastic behavior of carbon fiber/PEKK thermoplastic composites

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Lead-free BaBi4Ti4O15 ceramics: Effect of synthesis methods on phase formation and electrical properties

The processing of ferroelectric BaBi4Ti4O15 (BBT) ceramics from powders prepared by conventional solid state reaction (SSR) and mechanochemical activation (MA) has been investigated. It was shown that MA synthesis reduces the synthesis temperature of BBT powders, leading to smaller particles with reduced anisotropy and consequently to smaller grain size of ceramics. Dielectric properties were investigated in a wide range of temperatures (20-800 degrees C) and frequencies (1.21 kHz to 1 MHz). The relative dielectric permittivity at Curie temperature was higher for solid state obtained ceramics than for the mechanically treated ones. The conductivity of sintered samples was studied, suggesting decreasing of conductivity of BBT-MA in comparison with BBT-SS ceramics. The influence of the grain and the grain boundaries contribution to the dielectric behavior in both ceramics was analyzed through impedance spectroscopy. A well-defined ferroelectric hysteresis loop was obtained for both samples. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

Differential environmental impacts on small and medium size rivers from center of São Paulo State, Brazil, and regional management perspectives

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)