1000 resultados para 1988-1997
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Pós-graduação em Geociências e Meio Ambiente - IGCE
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Pós-graduação em Linguística e Língua Portuguesa - FCLAR
Topotactic transformation and dehydration of the zeolite gismondine to a novel Ca feldspar structure
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Efforts to understand and model the dynamics of the upper ocean would be significantly advanced given the ability to rapidly determine mixed layer depths (MLDs) over large regions. Remote sensing technologies are an ideal choice for achieving this goal. This study addresses the feasibility of estimating MLDs from optical properties. These properties are strongly influenced by suspended particle concentrations, which generally reach a maximum at pycnoclines. The premise therefore is to use a gradient in beam attenuation at 660 nm (c660) as a proxy for the depth of a particle-scattering layer. Using a global data set collected during World Ocean Circulation Experiment cruises from 1988-1997, six algorithms were employed to compute MLDs from either density or temperature profiles. Given the absence of published optically based MLD algorithms, two new methods were developed that use c660 profiles to estimate the MLD. Intercomparison of the six hydrographically based algorithms revealed some significant disparities among the resulting MLD values. Comparisons between the hydrographical and optical approaches indicated a first-order agreement between the MLDs based on the depths of gradient maxima for density and c660. When comparing various hydrographically based algorithms, other investigators reported that inherent fluctuations of the mixed layer depth limit the accuracy of its determination to 20 m. Using this benchmark, we found a similar to 70% agreement between the best hydrographical-optical algorithm pairings.
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The development of the winter-spring phytoplankton bloom was investigated in the Bay of Calvi (Corsica, Ligurian Sea, northwestern Mediterranean) in 1979, 1986, 1988, 1997 and 1998. A drastic reduction of phytoplankton biomass was evidenced over the last 2 decades, in relation to long-term changes in climatic and environmental conditions. Between 1979 and 1998, the monthly averaged chlorophyll a concentrations at 1 m decreased by about 80% during February, March and April. Simultaneously, major changes to hydrodynamic conditions include warmer water, overall decrease of salinity at 10 m depth, longer periods of bright sunshine and lower wind stress. The changes in environmental conditions were large enough to affect the vertical stability of the water column during the winter-spring period and to reduce nutrient replenishment of the surface layer prior to the usual period of phytoplankton growth. Until 1986, the main factor driving nutrient replenishment was the winter upward mixing of nutrient-rich deep waters, while the progressive reduction of mixing from 1988 induced nutrient limitation of surface waters in the last decade. The following hypotheses on changes in the development of the winter-spring phytoplankton bloom are made: (1) Until 1986, phytoplankton peaks took place in relatively high-nutrient waters and were diatom-dominated. (2) Between 1986 and 1988, decreasing Si availability led to Si limitation which caused a reduction in diatom abundance. This resulted in the disappearance of the diatom-dominated pulses and in lower phytoplankton biomass and was accompanied by a shift toward non-siliceous phytoplankton. (3) In 1988, 1997 and 1998, decreasing nitrate availability led to nitrate limitation, thus explaining the progressive reduction in non-siliceous phytoplankton biomass. Other, associated changes in benthos assemblages and ichthyofauna are documented. The conclusions from the Bay of Calvi are extended to the whole western Corsican coast. This confirms that the Mediterranean reacts rapidly to external perturbations, which are driven by climate change in that particular area.
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Vol. 19-23 (1911-1915) also called nuova serie, v.1-5; v. 24-50 (1916-1942) called also ser. 3-4; v.-<83> (-<1979>) called also ser. 7; v. 92-101, <1988>-1997 called also ser. 8; v. 102- called also ser. 9.
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Originally published: 1870-1931.
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Title from caption.
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Esta investigación analiza las tesis doctorales sobre tutoría defendidas en las universidades españolas en el periodo 1980-2014 a partir de la revisión de tres bases de datos (Teseo, Dialnet y TDR). Tras desarrollar una búsqueda exhaustiva se encontraron un total de 67 tesis doctorales que fueron analizadas considerando, por un lado, parámetros bibliométricos como producción por años, sexo del doctorando, universidades de lectura, directores y miembros de tribunales evaluadores; y, por otro lado, tendencias temáticas de las investigaciones doctorales sobre tutoría desde un análisis de descriptores, etapas educativas y tópicos desarrollados. El estudio concluye con algunas reflexiones en torno a la heterogeneidad de los atributos bibliométricos constatados en las tesis doctorales sobre tutoría, a la vez que se presentan las tendencias temáticas patentes en la construcción científica del campo de la tutoría desde las tesis doctorales.
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Esta guía sirve a los alumnos de Bachillerato como una fuente de información académica sobre los exámenes de que constan las Pruebas de Acceso a la Universidad. La primera parte, y clave de esta guía, es la referente a la elección de asignaturas que tienen que hacer los alumnos en el momento de matricularse para las Pruebas. La segunda parte está estructurada por asignaturas, para cada una de las cuales se detalla el formato de examen, los criterios de calificación y todos los ejercicios propuestos en las convocatorias del año anterior.
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Os autores fazem a análise retrospectiva dos 53 novos casos de Síndrome Nefrótico (S,N.) seguidos na Consulta de Nefrologia, de Novembro de 1988 a Marçoo de 1994, com o objectivo de avaliar alterações do padrão da doença em relação ao estudo feito anteriormente,em 1988. Foram estudados aspectos epidemiológicos, clínicos, terapêuticos e evolutivos. Identificaram-se 44 casos de S,N. primário (83%) - dos quais 61,4% comportaram-se como cortico-sensíveis, 25% como cortico-dependentes e 13,6% como cortico-resistentes. Com S.N. secundário a infecção (8 casos -15%), Lupus Eritematoso Sistémico (L.E.S.) e Amiloidose e 1 caso de S.N, congénito (2%). O elevado numero de cortico-dependemes atribui-se a um maior rigor no diagnóstico da recaida e/ou a alterações do padrão de vida das crianças. Verificou-se também um reduzido número de altas, relacionado com atitudes mais prudentes que se vêm adoptando em relação à evolução da doença.