958 resultados para Roosevelt, Franklin D. (Franklin Delano), 1882-1945.
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Signatur des Originals: S 36/F04108
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Signatur des Originals: S 36/F04110
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Signatur des Originals: S 36/F04111
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Signatur des Originals: S 36/F06510
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Signatur des Originals: S 36/F11209
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Melt pond covered sea ice is a ubiquitous feature of the summertime Arctic Ocean when meltwater collects in lower-lying areas of ice surfaces. Horizontal transects were conducted during June 2008 above and below landfast sea ice with melt ponds to characterize surface and bottom topography together with variations in transmitted spectral irradiance. We captured a rapid progression from a highly flooded sea ice surface with lateral drainage toward flaws and seal breathing holes to the formation of distinct melt ponds with steep edges. As the mass of the ice cover decreased due to meltwater drainage and rose upward with respect to the seawater level, the high-scattering properties of ice above the water level (i.e., white ice) were continuously regenerated, while pond waters remained transparent compared to underlying ice. The relatively stable albedos observed throughout the study, even as ice thickness decreased, were directly related to these surface processes. Transmission through the ice cover of incident irradiance in the 400-700 nm wave band ranged from 38% to 67% and from 5% to 16% beneath ponded and white ice, respectively. Our results show that this transmission varied not only as a function of surface type (melt ponds or white ice) areal coverage but also in relation to ice thickness and proximity to other surface types through the influence of horizontal spreading of light. Thus, in contrast to albedo, this implies that regional transmittance estimates need to consider melt pond size and shape distributions and variations in optical properties and thickness of the ice cover.
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Rómulo Betancourt y Juan D. Perón lideraron movimientos políticos considerados génesis de la democracia de masas en sus respectivos países, jalonada por sendos mítines populares del 17 de octubre de 1945 en Caracas y Buenos Aires, cuyo significado fue realzado como causa del proceso político ulterior. Pese a las diferencias, se destacan algunas semejanzas, tales como el contenido popular de ambos movimientos y cierta base de sustentación castrense. Se incluye un marco explicativo del proceso político venezolano precedente pero, en lo sustancial, el análisis se centra en el breve periodo transcurrido entre finales de la Segunda Guerra y el inicio de la Guerra Fría, cuando se produjeron cambios políticos en Argentina y Venezuela con un gran protagonismo de ambos dirigentes en sus respectivos países y en las recíprocas intromisiones que llevaron a cabo, enfatizando la oposición expresa de Betancourt hacia Perón desde el golpe de Estado del 4 de junio de 1943.