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This paper investigates the influence of reaction medium pH on silica-coating of magnetite nanoparticles. Magnetite nanoparticles were prepared by means of a reduction-precipitation method using ferric chloride as a starting material, which was partially reduced to ferrous salts by Na2SO3 before alkalinizing with ammonia. The particles were coated by sol-gel method with either ammonia or HCl aqueous solutions for either base- or acid-catalyzed hydrolysis, respectively. Powder X-ray diffraction, Fourier-transform infrared, and Zeta Potential were used for the characterization of oxides and of the coated magnetic nanoparticles. The observed difference of pH IEP in KCl solution for pure silica (2.0), magnetite (5.0), and silica-coated magnetite (2.3) samples confirms that the coating process was effective since the charge surface properties of coated magnetic nanoparticles are close to that of pure silica, even though the Fourier-transform infrared spectra did not evidence the formation of Fe-O-Si bonds.

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ResumoO presente trabalho tem como objetivo discutir como a inclusão social e produtiva de catadores de materiais recicláveis, antes presente apenas na agenda de políticas públicas locais, alcançou a agenda governamental nacional. Recorre-se à discussão teórica de múltiplos fluxos, de Kingdon (1995), apontando suas limitações para a análise do fenômeno investigado. Os procedimentos metodológicos adotados foram: revisão bibliográfica, observação participante em eventos, levantamento de dados secundários, conversas espontâneas e entrevistas semiestruturadas. Observa-se que, em certa medida, houve a junção dos três fluxos abordados por Kingdon (1995), a saber, um problema que ganhou reconhecimento público, um ambiente político favorável à entrada de questões sociais na agenda e uma alternativa que se apresentou viável para a solução do problema -a inclusão de catadores em programas de coleta seletiva -, mas que não responde completamente as dimensões do problema. Nesse processo, organizações da sociedade civil tiveram um papel fundamental. No entanto, o modelo de múltiplos fluxos não apenas desconsidera um processo de formação de agenda de "baixo para cima", como também deixa de lado a discussão sobre a influência que atores extrainstitucionais, como organizações da sociedade civil, possam exercer nesse processo. Desse modo, o modelo não dá conta de explicar as complexas relações entre Estado e sociedade civil na realidade brasileira. Palavras-chave: AbstractThis article aims to discuss the issue of social and productive inclusion of collectors of recyclable materials, present previously only in local public policy agendas and that has now reached the national governmental agenda. The theoretical discussion is based on Kingdon´s (1995) multiple streams theory, highlighting its limitations in the analysis of the phenomenon under study. The methodological procedures used were: bibliographical review, participative Artigo submetido em 23 de março de 2011 e aceito para publicação em 04 de agosto de 2011.

Nanotechnology is a growing branch of science that deals with the development of structural features bearing at least one dimension in the nano range. More specifically, nanomaterials are defined as objects with dimensions that range from 1 to 100 nm, which give rise to interesting properties. In particular, silver and titanium nanoparticles (AgNPs and TiNPs, respectively) are known for their biological and biomedical properties and are often used in consumer products such as cosmetics, food additives, kitchen utensils, and toys. This situation has increased environmental and occupational exposure to AgNPs and TiNPs, which has placed demand for the risk assessment of NPs. Indeed, the same properties that make nanomaterials so attractive could also prove deleterious to biological systems. Of particular concern is the effect of NPs on mitochondria because these organelles play an essential role in cellular homeostasis. In this scenario, this work aimed to study how AgNPs and TiNPs interact with the mitochondrial respiration chain and to analyze how this interaction interferes in the bioenergetics and oxidative state of the organelles after sub-chronic exposure. Mitochondria were exposed to the NPs by gavage treatment for 21 days to check whether co-exposure of the organelles to the two types of NPs elicited any mitochondrion-NP interaction. More specifically, male Wistar rats were randomly assigned to four groups. Groups I, II, III, and IV received mineral oil, TiNPs (100 μg/kg/day), AgNPs (100 μg/kg/day), and TiNPs + AgNPs (100 μg/kg/day), respectively, by gavage. The liver was immediately removed, and the mitochondria were isolated and used within 3 h. Exposure of mitochondria to TiNPs + AgNPs lowered the respiratory control ratio, causing an uncoupling effect in the oxidative phosphorylation system. Moreover, both types of NPs induced mitochondrial swelling. Extended exposure of mitochondria to the NPs maintained increased ROS levels and depleted the endogenous antioxidant system. The AgNPs and TiNPs acted synergistically-the intensity of the toxic effect on the mitochondrial redox state was more significant in the presence of both types of NPs. These findings imply that the action of the NPs on mitochondria underlie NP toxicity, so future application of NPs requires special attention.

We study orbital dynamics of a compound solar sail, namely, a Simple Solar Photon Thruster and compare its behavior to that of a common version of sailcraft. To perform this analysis, development of a mathematical model for force created by light reflection on all sailcraft elements is essential. We deduce the equations of sailcraft's motion and compare performance of two schemes of solar propulsion for two test time-optimal control problems of trajectory transfer.

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Neste trabalho, procurou-se desvendar as representações sociais elaboradas por trabalhadores em torno da perda do emprego. Para tanto, teceram-se algumas considerações sobre o processo de reestruturação produtiva, particularizando as mudanças ocorridas nas relações de trabalho, nas formas de mediação de conflitos e seus impactos na subjetividade humana. A natureza do fenômeno investigado imprimiu uma escolha teórico-metodológica cunhada nos pressupostos da abordagem interpretativa, optando-se, mais especificamente, por se analisar o significado da perda do emprego para os trabalhadores sob a ótica da teoria das representações sociais. Portanto, trata-se de estudo de natureza qualitativa, realizado em amostra de ex-operários de uma multinacional do setor metalúrgico-automobilístico, após sua reestruturação produtiva. As representações apreendidas acerca do desemprego convalidam a importância dessa questão social no desenvolvimento da subjetividade humana, principalmente como fonte de pressão e ameaça à cidadania.