1000 resultados para history of oceanography


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Fil: Bordagaray, María Eugenia. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación. Instituto de Investigaciones en Humanidades y Ciencias Sociales (UNLP-CONICET); Argentina.

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Professional guidance has developed in Argentina since 1940, influenced by the guidance which in that time came from Spain, France, Belgium and Switzerland. The paper analyzes the first experiences in professional guidance, developed both in the great industrial cities as Buenos Aires and Rosario, and little urban centres as Tucumán or San Luis. The institutional and political context of such experiences is also analyzed, as well as the State's full support of them.

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Este trabajo trata sobre la famosa digresión de Tucídides en el libro sexto de su historia acerca de la caída de la tiranía en Atenas (Tuc. 6.54-59) y su relación con el relato de Heródoto. La digresión de Tucídides (y más específicamente su tono polémico) ha provocado controversia entre los comentadores, que han analizado a fondo las narrativas de los dos historiadores tanto desde una perspectiva histórica como historiográfica. Este estudio tiende a contribuir a esta discusión a través de tres sugerencias: la primera, Tucídides se mete no solo con la pequeña sección sobre los tiranicidas de la Historia de Heródoto (esto es Hdt. 5.55-65), sino, más bien, con toda la narrativa de la Historia de Heródoto sobre la liberación de Atenas de la tiranía que se extiende hasta el discurso de Socles (esto es Hdt. 5.55-5.96.2); segunda, las correcciones de Tucídides al relato de Heródoto son menores, tercera, dado que las divergencias de Tucídides con respecto a Heródoto no son decisivas para la versión correcta de los hechos, el tono polémico de Tucídides en su digresión resulta todavía más difícil de explicar. En este trabajo se sugiere tentativamente que la actitud polémica de Tucídides tiene más sentido si es interpretada en el contexto de la rivalidad del historiador con Heródoto

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Professional guidance has developed in Argentina since 1940, influenced by the guidance which in that time came from Spain, France, Belgium and Switzerland. The paper analyzes the first experiences in professional guidance, developed both in the great industrial cities as Buenos Aires and Rosario, and little urban centres as Tucumán or San Luis. The institutional and political context of such experiences is also analyzed, as well as the State's full support of them.

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Fil: Bordagaray, María Eugenia. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación. Instituto de Investigaciones en Humanidades y Ciencias Sociales (UNLP-CONICET); Argentina.

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Quantitative analysis of the late Cenozoic planktonic foraminiferal record from western Arabian Sea Site 722 revealed long term trends in the history of oceanography and climate. The modern western Arabian Sea surface waters are highly influenced by the monsoonal wind system. Summer upwelling, a result of southwestern winds, occurs along the coast of Somalia which produces distinct foraminiferal assemblages which are dominated by G. bulloides d'Orbigny. Consequently, variations in the distribution record of G. bulloides through time monitor the upwelling history associated with monsoonal activities. G. bulloides was a minor constituent of the foraminiferal fauna from the bottom of the hole (~14.5 Ma) until about 8.6 Ma ago. Then a rapid shift occurred toward higher values, up to 53% at 7.4 Ma. We interpret this rapid increase as a major step in the evolution of the monsoonal history. It is either the establishment of the system or at least a strong intensification of the monsoonal winds. At 5.5 Ma a significant drop of the G. bulloides relative abundance occurred which may indicate less upwelling, or alternatively other biota may have been favored in this period. From 5.0 Ma to Recent the G. bulloides record indicates that upwelling has occurred with minor fluctuations.

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The dataset is based on samples collected in the spring of 2002 in the Western Black Sea in front of Bulgaria coast. The whole dataset is composed of 76 samples (from 27 stations of National Monitoring Grid) with data of mesozooplankton species composition abundance and biomass. Sampling on zooplankton was performed from bottom up to the surface at depths depending on water column stratification and the thermocline depth. Zooplankton samples were collected with vertical closing Juday net,diameter - 36cm, mesh size 150 µm. Tows were performed from surface down to bottom meters depths in discrete layers. Samples were preserved by a 4% formaldehyde sea water buffered solution. Sampling volume was estimated by multiplying the mouth area with the wire length. Mesozooplankton abundance: The collected material was analysed using the method of Domov (1959). Samples were brought to volume of 25-30 ml depending upon zooplankton density and mixed intensively until all organisms were distributed randomly in the sample volume. After that 5 ml of sample was taken and poured in the counting chamber which is a rectangle form for taxomomic identification and count. Large (> 1 mm body length) and not abundant species were calculated in whole sample. Counting of organisms were made in the Dimov chamber under the stereomicroscope to the lowest taxon possible. Taxonomic identification was done at the Institute of Oceanology by Kremena Stefanova using the relevant taxonomic literature (Mordukhay-Boltovskoy, F.D. (Ed.). 1968, 1969,1972). Taxon-specific abundance: The collected material was analysed using the method of Domov (1959). Samples were brought to volume of 25-30 ml depending upon zooplankton density and mixed intensively until all organisms were distributed randomly in the sample volume. After that 5 ml of sample was taken and poured in the counting chamber which is a rectangle form for taxomomic identification and count. Copepods and Cladoceras were identified and enumerated; the other mesozooplankters were identified and enumerated at higher taxonomic level (commonly named as mesozooplankton groups). Large (> 1 mm body length) and not abundant species were calculated in whole sample. Counting and measuring of organisms were made in the Dimov chamber under the stereomicroscope to the lowest taxon possible. Taxonomic identification was done at the Institute of Oceanology by Kremena Stefanova using the relevant taxonomic literature (Mordukhay-Boltovskoy, F.D. (Ed.). 1968, 1969,1972).

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The iterative evolutionary radiation of planktic foraminifers is a well-documented macroevolutionary process. Here we document the accompanying size changes in entire planktic foraminiferal assemblages for the past 70 My and their relationship to paleoenvironmental changes. After the size decrease at the Cretaceous/Paleogene (K/P) boundary, high latitude assemblages remained consistently small. Size evolution in low latitudes can be divided into three major phases: the first is characterized by dwarfs (65-42 Ma), the second shows moderate size fluctuations (42-14 Ma), and in the third phase, planktic foraminifers have grown to the unprecedented sizes observed today. Our analyses of size variability with paleoproxy records indicate that periods of size increase coincided with phases of global cooling (Eocene and Neogene). These periods were characterized by enhanced latitudinal and vertical temperature gradients in the oceans and high diversity (polytaxy). In the Paleocene and during the Oligocene, the observed (minor) size changes of the largely low-diversity (oligotaxic) assemblages seem to correlate with productivity changes. However, polytaxy per se was not responsible for larger test sizes.