998 resultados para 201-1231E


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Sorption of volatile hydrocarbon gases (VHCs) to marine sediments is a recognized phenomenon that has been investigated in the context of petroleum exploration. However, little is known about the biogeochemistry of sorbed methane and higher VHCs in environments that are not influenced by thermogenic processes. This study evaluated two different extraction protocols for sorbed VHCs, used high pressure equipment to investigate the sorption of methane to pure clay mineral phases, and conducted a geochemical and mineralogical survey of sediment samples from different oceanographic settings and geochemical regimes that are not significantly influenced by thermogenic gas. Extraction of sediments under alkaline conditions yielded higher concentrations of sorbed methane than the established protocol for acidic extraction. Application of alkaline extraction in the environmental survey revealed the presence of substantial amounts of sorbed methane in 374 out of 411 samples (91%). Particularly high amounts, up to 2.1 mmol kg**-1 dry sediment, were recovered from methanogenic sediments. Carbon isotopic compositions of sorbed methane suggested substantial contributions from biogenic sources, both in sulfate-depleted and sulfate-reducing sediments. Carbon isotopic relationships between sorbed and dissolved methane indicate a coupling of the two pools. While our sorption experiments and extraction conditions point to an important role for clay minerals as sorbents, mineralogical analyses of marine sediments suggest that variations in mineral composition are not controlling variations in quantities of sorbed methane. We conclude that the distribution of sorbed methane in sediments is strongly influenced by in situ production.

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Contenido: El aristotelismo y el tomismo frente al egoísmo psicológico / María L. Lukac de Stier – El deseo natural de ver a Dios en la Summa contra Gentiles / Guillermo Jorge Cambiasso – La creación como encuentro del ser y de la nada en la teología del maestro Eckhart de Hochheim O.P. (1260-1327) / Brian J. Farrelly – Malebranche y el libertinage érudit / Francisco Leocata – The problem of person and Jean Mouroux / John M. McDermott ; Glenn J. Comandini – Los fundamentos de la Bioética de H. Tristram Engelhardt / Jorge Martínez Barrera – Cuando las contradictorias son verdaderas / Marisa Villalba de Tablón – Examen del escepticismo moral y del relativismo moral / Camilo Tale – Saint Thomas et le mystère de la création : une réponse aux interrogations de l’homme d’aujourd’hui / Marie-Dominique Philippe – La finalidad de la naturaleza humana : alcance y actualidad de la cuestión / Beatriz Eugenia Reyes Oribe – La providencia y el gobierno del mundo / Alberto Caturelli – Saint Thomas et le problème de la possibilité d’un univers créé éternel / Alain-Marie de Lassus – La causalidad material de los elementos en la generación de los cuerpos mixtos / Mario Enrique Sacchi -- Bibliografía

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Consultoria Legislativa - Área I - Direito Constitucional, Eleitoral, Municipal, Direito Administrativo, Processo Legislativo e Poder Judiciário.