974 resultados para Cavalcanti, Mariana
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Inclui bibliografia.
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Inclui notas explicativas, bibliográficas e bibliografia.
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Esta investigação visa o estudo e enquadramento em termos históricos, tipológicos e artísticos das pinturas de Bento Coelho da Silveira (1620-1708), expostas na igreja de S. Bartolomeu da Charneca em Lisboa. Uma vez que sabemos que não foram realizadas especificamente para a igreja de S. Bartolomeu da Charneca em Lisboa onde, na atualidade se encontram, procurar-se-á averiguar qual a origem destas obras; quem foi o seu encomendador e ainda aferir a pertinência e a coerência do programa iconográfico que veiculam. Caracterizar-se-á a pintura deste artista barroco, em concreto as nove telas de temática mariana que se encontram na igreja supracitada. É ainda objeto deste trabalho a comparação com outras obras do pintor, analisando o cânone, os atributos, os adereços e as composições, com particular relevo nas atitudes e nas características expressivas, bem como no estado de alma dos personagens todos eles evidenciando uma atitude melancólica. Pretende-se, finalmente, tecer considerações acerca do seu estado de conservação e, eventualmente, efetuar propostas de conservação e restauro, caso seja necessário.
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The cores, dredges and submarine camera observations described in this report were taken on the KH-71-1 Expedition in January-March, 1971 by the Ocean Research Institute, University of Tokyo from the Hakuho Maru. A total of 24 cores, dredges and camera station sites have been recovered.
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The purpose of this work is to study the mobility and budget of Fe isotopes in the oceanic crust and in particular during low-temperature interaction of seawater with oceanic basalt. We carried out this investigation using samples from Ocean Drilling Program (ODP) Site 801C drilled during Leg 129 and Leg 185 in Jurassic Pacific oceanic crust seaward of the Mariana Trench. The site comprises approximately 450 m of sediment overlying a section of 500 m of basalt, which includes intercalated pelagic and chemical sediments in the upper basaltic units and two low-temperature (10-30°C) ocherous Si-Fe hydrothermal deposits. Fe was chemically separated from 70 selected samples, and 57Fe/54Fe ratios were measured by MC-ICP-MS Isoprobe. The isotopic ratios were measured relative to an internal standard solution and are reported relative to the international Fe-standard IRMM-14. Based on duplicate measurements of natural samples, an external precision of 0.2? (2 sigma) has been obtained. The results indicate that the deep-sea sediment section has a restricted range of d57Fe, which is close to the igneous rock value. In contrast, large variations are observed in the basaltic section with positive d57Fe values (up to 2.05?) for highly altered basalts and negative values (down to ?2.49?) for the associated alteration products and hydrothermal deposits. Secondary Fe-minerals, such as Fe-oxyhydroxides or Fe-bearing clays (celadonite and saponite), have highly variable d57Fe values that have been interpreted as resulting from the partial oxidation of Fe(2+) leached during basalt alteration and precipitated as Fe(3+)-rich minerals. In contrast, altered basalts at Site 801C, which are depleted in Fe (up to 80%), display an increase in d57Fe values relative to fresh values, which suggest a preferential leaching of light iron during alteration. The apparent fractionation factor between dissolved Fe(2+) and Fe remaining in the mineral is from 0.5? to 1.3? and may be consistent with a kinetic isotope fractionation where light Fe is stripped from the minerals. Alternatively, the formation of secondary clays minerals, such as celadonite during basalt alteration may incorporate preferentially the heavy Fe isotopes, resulting in the loss of light Fe isotopes in the fluids. Because microbial processes within the oceanic crust are of potential importance in controlling rates of chemical reactions, Fe redox state and Fe-isotope fractionation, we evaluated the possible effect of this deep biosphere on Fe-isotope signatures. The Fe-isotope systematics presented in this study suggest that, even though iron behavior during seafloor weathering may be mediated by microbes, such as iron-oxidizers, d57Fe variations of more than 4? may also be explained by abiotic processes. Further laboratory experiments are now required to distinguish between various processes of Fe-isotope fractionation during seafloor weathering.
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Mode of access: Internet.
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Mode of access: Internet.
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Mode of access: Internet.
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Mode of access: Internet.