Formation of colloidal particles of hydrous iron oxide by forced hydrolysis

The mechanism of formation and growth of hydrous iron oxide (FeOOH) during the initial stages of forced hydrolyses of ferric chloride aqueous solution was studied by small angle X-ray scattering (SAXS). The effect of the hydrolysis temperature (60°C, 70°C and 80°C) and of the addition of urea on the formation of colloidal particles under isothermal conditions were investigated. Based on the experimental scattering functions in the Guinier range, we suggest the presence of elongated colloidal particles. The particle diameter and length, and their variation with time, were determined by fitting the form factor of prolate ellipsoids to the experimental scattering functions. We have assumed that our solutions are in a dilute state and that all colloidal particles are approximately of the same size. The colloidal particles have geometrical shapes similar to those of the subcrystals that build up the superstructure of β-FeOOH crystals, indicating that the formation of this hydrous iron oxide is governed by an aggregation process. Otherwise, the addition of urea hinders the growth and yields smaller particles, with a reduction in size greater than 50%. © 2000 Elsevier Science B.V. All rights reserved.

Teachers Formation in Higher Education: Some Aspects under the Light of Education-Work Relations

This text is mainly aimed to address essential aspects of teacher formation in the light of education-work relations in the higher education, from our systematic experience in higher education teaching, particularly teaching and research in the field of Didactics discipline. This formulation is justified considering our concern in seeking to situate this discussion in the context of bringing together knowledge areas and the field of teaching knowledge. Still, our choice to develop such an approach in the light of work-education relationship is due to the belief about the possibilities of seeking to overcome the requirements imposed by capitalism to our educational system, within the possible contradictions of these relationships. In this context the teachers’ formation in higher education gains social and strategic importance, taking on the task of forming individuals of “action-reflection-action” in a society established historically based on the social relations which settle in the light of capital’s multiple determinations. It appears that, in this sense, the major confrontations have been given within the discussions about what to prioritize or combine in the list of criteria and content for teacher’s formation. In Didactic, we seek to emphasize discussions that we consider with a philosophical background, referring to the orientation of teaching practice in knowledge of contemporary ideological struggle; socio-historical, referring to the possibility of formation of disciplines, among them Didactic, and curriculums and references to support its guidance in the process of teacher’s formation. This context of discussion is based on the concrete teaching practice with a view to transformation and to search for new syntheses in terms of knowledge and in terms of historical reality. Then therefore, our methodological approach grounded in the dimensions of the same unit: historical materialism as posture, method and as praxis.

Mechanisms of SnO2 Nanoparticles Formation and Growth in Acid Ethanol Solution Derived from SAXS and Combined Raman-XAS Time-Resolved Studies

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Formation and evolution of TiO2 nanotubes in alkaline synthesis

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

Comparative study of resistance to heat in two species of leaf-cutting ants

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Influence of Cu and Cr on the matrix decomposition of quenched Al-Zn-Mg alloy

The Inoue procedure is used to study the influence of Cr and Cu elements, jointly or individually, on the matrix decomposition of quenched Al-Zn-Mg alloys. The addition of copper and copper with chromium does not significantly change the limits of the temperatures of formation of Guinier-Preston zone and the range of the matrix decomposition. The control of the vacancy concentration in the alloys by different heat treatments and the addition of certain elements such as copper and chromium seems to play an important role in the nucleation rate and the kinetics of phase transformations.

The effects of ovalbumin as a protein source during the in vitro production of bovine embryos

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

DEA and DSC study of cubic silsesquioxane epoxy resin nanocomposites

Non-isothermal dielectric analysis (DEA) and differential scanning calorimetry (DSC) techniques were used to study the epoxy nanocomposites prepared by reacting 1,3,5,7,9,11,13,15-octa[dimethylsiloxypropylglycidylether] pentaciclo [9.5.1.1(3,9).1(5,15).1(7,13)] octasilsesquioxane (ODPG) with methylenedianiline (MDA). Loss factor (epsilon) and activation energy were calculated by DEA. The relationships between the loss factor, the activation energy, the structure of the network, and the mechanical properties were investigated. Activation energies determined by DEA and DSC, heat of polymerization, fracture toughness and tensile modulus show the same profile for mechanical properties with respect to ODPG content.

Differentially expressed genes in giant cell tumor of bone

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

Ultrastructure of spermatogenesis in the white-lined broad-nosed bat, Platyrrhinus lineatus (Chiroptera: Phyllostomidae)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Moisture sorption isotherms of fresh and blanched pumpkin (Cucurbita moschata)

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

Photo-electrochemical investigation of anodic oxide films on cast Ti-Mo alloys I. Anodic behaviour and effect of alloy composition

The anodic behaviour of cast Ti-Mo alloys, having different Mo contents (6-20 wt.%), was investigated in acidic and neutral aerated aqueous solutions. All sample showed a valve-metal behaviour, owing to formation and thickening of barrier-type anodic oxides displaying interference colours Growth kinetics. of passive films is influenced by both anodizing electrolyte and composition of the starting alloy. This last parameter was found to change also the solid-state properties of the films, explored by photoelectrochemical and impedance spectroscopy experiments. Thicker films (U(f) = 8 V/MSE) grown on alloys richer in Mo showed more resistive character and a photocurrent sign inversion under negative bias, that revealed an insulating character, whereas corresponding films grown on alloys with lower Mo content, as well as thinner films, behaved as n-type semiconductors. Results are discussed in terms of formation of a mixed Ti-Mo oxide phase. (C) 2008 Elsevier Ltd. All rights reserved

Iron chelating-mediated antioxidant activity of Plectranthus barbatus extract on mitochondria

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

Enthalpy-entropy compensation based on isotherms of mango

Dados de equilíbrio da umidade da polpa de manga foram determinados utilizando-se o método estático gravimétrico. As isotermas de adsorção e dessorção foram obtidas na faixa de 30-70 ºC e as atividades de água (a w) de 0,02 a 0,97. A utilização do modelo de GAB nos resultados experimentais, através da análise de regressão não linear, proporcionou um bom ajuste entre os dados experimentais e os valores calculados. O calor isostérico de sorção foi estimado a partir dos dados de equilíbrio de sorção, utilizando-se a equação de Clausius-Clayperon. Notou-se que os calores isostéricos de sorção crescem com o aumento da temperatura e pode ser bem ajustado através de uma relação exponencial. A teoria da compensação entalpia-entropia foi aplicada às isotermas de sorção e gráficos deltaH versus deltaS forneceram as temperaturas isocinéticas, indicando um processo de sorção entalpicamente controlado.