17 resultados para Cerâmica - Métodos de síntese


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Dissertação de mest., Engenharia Biológica, Faculdade de Engenharia e de Recursos Naturais, Univ. do Algarve, 2008

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Os métodos utilizados na resolução de problemas, nos vários ramos da Engenharia ou ciências aplicadas, baseiam-se, actualmente, em uma de duas categorias: métodos analíticos e métodos numéricos. É preferível a utilização dos métodos analíticos, na resolução de equações ou outros modelos matemáticos, sempre que possível, uma vez que formamões gerais em vez de particularizadas, para além de uma maior informação.

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O Homem tem modificado consideravelmente o meio natural e transformado profundamente as paisagens primitivas. As vias de comunicação e os aglomerados populacionais constituem referências evidentes da sua presença e denotam o percurso do homem no tempo. Neste processo de mudança contínua o papel dos engenheiros foi fundamental pois a sua prática remonta às civilizações anteriores à era Cristã da qual temos o testemunho de Arquimedes (287-212 a.C.) que foi um grande cientista e engenheiro da Antiguidade. O termo engenharia em termos semânticos tem a sua origem da palavra latina ingeniatorum significando “engenhoso na arte de projectar” (Duffell, 1990). De facto a engenharia tem sido definida como uma arte que permite que os principais recursos da natureza sejam transformados, adaptados e aplicados para o uso ou conveniência do homem (The New Caxton Encyclopedia, 1986).

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Tese dout., Engenharia Electrónica e Computação, Universidade do Algarve, 2009

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Dissertação mest., Biologia Marinha, Universidade do Algarve, 2008

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Dissertação mest., Qualidade em Análises, Universidade do Algarve, 2007

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Tese de Doutoramento, Gestão, na especialidade de Marketing, Faculdade de Economia, Universidade do Algarve, 2007

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Tese de dout., Ciências Agrárias (Protecção de Plantas), Unidade de Ciências e Tecnologias Agrárias, Univ. do Algarve, 1994

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Dissertação de mest., Gestão e Conservação da Natureza, Faculdade de Ciências do Mar e do Ambiente, Univ. do Algarve, 2006

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La seguridad y eficacia de las terapias térmicas están ligadas con la determinación exacta de la temperatura, es por ello que la retroalimentacón de la temperatura en los métodos computacionales es de vital importancia.

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Tese de dout., Bioquímica (Biologia Celular e Molecular), Faculdade de Ciências e Tecnologia, Univ. do Algarve, 2010

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Dissertação de mest., Tecnologia de Alimentos, Instituto Superior de Engenharia, Univ. do Algarve, 2012

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Cancer is a multistage process characterized by three stages: initiation, promotion and progression; and is one of the major killers worldwide. Oxidative stress acts as initiator in tumorigenesis; chronic inflammation promotes cancer; and apoptosis inactivation is an issue in cancer progression. In this study, it was investigated the antioxidant, antiinflammatory and antitumor properties of hexane, ether, chloroform, methanol and water extracts of five species of halophytes: A. macrostachyum, P. coronopus, J. acutus, C. edulis and A. halimus. Antioxidant activity was assessed by DPPH• and ABTS•+ methods, and the total phenolics content (TPC) was evaluated by the Folin-Ciocalteau method. The anti-inflammatory activity of the extracts was determined by the Griess method, and by evaluating the inhibition of NO production in LPS-stimulated RAW- 264.7 macrophages. The cytotoxic activity of the extracts against HepG2 and THP1 cell lines was estimated by the MTT assay, and the results obtained were further compared with the S17 non-tumor cell line. The induction of apoptosis of J. acutus ether extract was assessed by DAPI staining. The highest antioxidant activities was observed in C. edulis methanol and the J. acutus ether extracts against the DPPH• radical; and J. acutus ether and A. halimus ether extracts against the ABTS•+ radical. The methanol extracts of C. edulis and P. coronopus, and the ether extract of J. acutus revealed a high TPC. Generally the antioxidant activity had no correlation with the TPC. The A. halimus chloroform and P. coronopus hexane extracts demonstrated ability to reduce NO production in macrophages (> 50%), revealing their anti-inflammatory capacity. The ether extract of J. acutus showed high cytotoxicity against HepG2 cancer cells, with reduced cellular viability even at the lowest concentrations. This outcome was significantly lower than the obtained with the non-tumor cells (S17). This result was complemented by the induction of apoptosis.

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This work describes the synthesis of nanosized metal sulfides and respective SiO2 and/or TiO2 composites in high yield via a straightforward process, under ambient conditions (temperature and pressure), by adding to aqueous metals a nutrient solution containing biologically generated sulfide from sulfate-reducing bacteria (SRB). The nanoparticles‘ (NPs) morphological properties were shown not to be markedly altered by the SRB growth media composition neither by the presence of bacterial cells. We further extended the work carried out, using the effluent of a bioremediation system previously established. The process results in the synthesis of added value products obtained from metal rich effluents, such as Acid Mine Drainage (AMD), when associated with the bioremediation process. Precipitation of metals using sulfide allows for the possibility of selective recovery, as different metal sulfides possess different solubilities. We have evaluated the selective precipitation of CuS, ZnS and FeS as nanosized metal sulfides. Again, we have also tested the precipitation of these metal sulfides in the presence of support structures, such as SiO2. Studies were carried out using both artificial and real solutions in a continuous bioremediation system. We found that this method allowed for a highly selective precipitation of copper and a lower selectivity in the precipitation of zinc and iron, though all metals were efficiently removed (>93% removal). This research has also demonstrated the potential of ZnS-TiO2 nanocomposites as catalysts in the photodegradation of organic pollutants using the cationic dye, Safranin-T, as a model contaminant. The influence of the catalyst amount, initial pH and dye concentration were also evaluated. Finally, the efficiency of the precipitates as catalysts in sunlight mediated photodegradation was investigated, using different volumes of dye-contaminated water (150 mL and 10 L). This work demonstrates that all tested composites have the potential to be used as photocatalysts for the degradation of Safranin-T.

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Dissertação de mestrado, Arqueologia, Faculdade de Ciências Humanas e Sociais, Universidade do Algarve, 2015