960 resultados para Angola Benguela Front
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Diurnal variations and geographic distribution of zooplankton and micronekton are studied in the Angola Dome. The small zooplankton species (Copepodids, Copepods, Amphipods, Ostracods, Chaetognaths, etc.) undertake vertical migrations within a 100 m water layer. Most of the micronekton species are below this layer during the day and move towards the surface during the night. The whole region prospected is rich in zooplankton and micronekton species that are present in the upper 100 m layer during the day. Only the South-West region is poor. On the contrary, this latter region is abundant in species that migrate below this layer during the day. The authors think there are 3 main difficulties in establishing good relationships between micronekton and tunas distribution: 1 - inability of micronekton nets to catch the tunas preys; 2 - the great diversity of tunas food; and 3 - the too large delay between micronekton studies and those of stomach contents of tunas.
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In February-March 1971 the hydrological conditions off Angola did not display the thermal dome mapped by Mazeika's averages (1967). Cold water cells observed are connected at the surface to a sinuous boundary between low-salinity coastal waters and high-salinity tropical oceanic waters. That boundary coincides rather regularly with an area where trades and SW winds alternate; photosynthesis growths rapidly in a thermoclinal layer that rises until 10 m of the surface but never outcrops. Below a poor and permanent homogeneous surface layer, chlorophyll concentrations show a distribution which is typical of divergence areas. Geostrophical and measured currents show off a transient process in horizontal and vertical movements, however the general curvature of the circulation is propitious to upwelling. Oxygen oversaturations of about 110%, suggest a moderate potential primary production which confirms slowness and alternation of movements. Also, the regular range of the various chemical and biological levels and moderate chlorophyll concentrations suggest an ecosystem where nutrients supply rapidly equilibrate phytoplankton consumption and not at all a 'phytoplankton bloom' area as that which exists in coastal upwelling. Values of Richardson's number show that instability becomes visible at the bottom of the euphotic layer. An evaluation of the vertical motion is inferred by the peculiar distribution and diurnal alternance of the winds shows that 'doming' structures may be sustained by local meteorological events.
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A presente tese versa sobre o processo de transição para a democracia em Angola. O período estudado compreende a independência do país em 1975 ao ano de 2012, com a realização das terceiras eleições gerais. Para tal, são realizados três recortes cronológicos, a saber: (1) de 1975 com a independência de Angola e a inauguração da Primeira República, ao ano de 1991 com o advento do multipartidarismo e da Segunda República; (2) da Segunda República em 1991, ao ano de 2010 com a promulgação da chamada Constituição Atípica e a instauração da Terceira República; (3) e da Terceira República em 2010, ao pleito eleitoral de 2012. Cada um destes períodos é estudado a partir da análise das instituições políticas que caracterizam a democracia. São igualmente identificadas e examinadas as razões que levaram a deflagrar a transição (por quê?); a forma pela qual a transição foi desencadeada (como?); os atores envolvidos no processo transicional (quem?); bem como o estágio da democratização em Angola. A tese é desenvolvida tendo em conta a produção bibliográfica existente sobre o tema e os dados empíricos coletados mediante entrevistas em profundidade com atores envolvidos no processo de transição e cidadãos comuns.
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