Una aproximación al estudio conceptual de los desastres urbanos en América Latina. La importancia de un proceso de gestión integrado para desarrollar estrategias de prevención de riesgos y disminuir la vulnerabilidad social

Pn este trabajo se intenta principalmente realizar una aproximación teórica a los conceptos de desastre urbano, vulnerabilidad social, degradación ambiental y riesgo; desde una perspectiva que tenga en cuenta las siguientes consideraciones. -) Los desastres desencadenados por fenómenos naturales son procesos sociales, económicos y políticos. -) La degradación ambiental en el ámbito urbano. -) La importancia de la percepción y la construcción social en el concepto de riesgo. -) La vulnerabilidad considerada como producto histórico y su relación con los fenómenos naturales. Dentro de este contexto, se destacará la relevancia de un proceso de gestión continuo e integrado, que incluya estrategias que tiendan a disminuir la vulnerabilidad y, en consecuencia el riesgo de generación de desastres que tienen como detonante fenómenos naturales. Por último se agrega un comentario final y bibliografía sobre el tema que esperamos sea de utilidad para trabajos posteriores.

Una aproximación al estudio conceptual de los desastres urbanos en América Latina. La importancia de un proceso de gestión integrado para desarrollar estrategias de prevención de riesgos y disminuir la vulnerabilidad social

Pn este trabajo se intenta principalmente realizar una aproximación teórica a los conceptos de desastre urbano, vulnerabilidad social, degradación ambiental y riesgo; desde una perspectiva que tenga en cuenta las siguientes consideraciones. -) Los desastres desencadenados por fenómenos naturales son procesos sociales, económicos y políticos. -) La degradación ambiental en el ámbito urbano. -) La importancia de la percepción y la construcción social en el concepto de riesgo. -) La vulnerabilidad considerada como producto histórico y su relación con los fenómenos naturales. Dentro de este contexto, se destacará la relevancia de un proceso de gestión continuo e integrado, que incluya estrategias que tiendan a disminuir la vulnerabilidad y, en consecuencia el riesgo de generación de desastres que tienen como detonante fenómenos naturales. Por último se agrega un comentario final y bibliografía sobre el tema que esperamos sea de utilidad para trabajos posteriores.

Una aproximación al estudio conceptual de los desastres urbanos en América Latina. La importancia de un proceso de gestión integrado para desarrollar estrategias de prevención de riesgos y disminuir la vulnerabilidad social

Pn este trabajo se intenta principalmente realizar una aproximación teórica a los conceptos de desastre urbano, vulnerabilidad social, degradación ambiental y riesgo; desde una perspectiva que tenga en cuenta las siguientes consideraciones. -) Los desastres desencadenados por fenómenos naturales son procesos sociales, económicos y políticos. -) La degradación ambiental en el ámbito urbano. -) La importancia de la percepción y la construcción social en el concepto de riesgo. -) La vulnerabilidad considerada como producto histórico y su relación con los fenómenos naturales. Dentro de este contexto, se destacará la relevancia de un proceso de gestión continuo e integrado, que incluya estrategias que tiendan a disminuir la vulnerabilidad y, en consecuencia el riesgo de generación de desastres que tienen como detonante fenómenos naturales. Por último se agrega un comentario final y bibliografía sobre el tema que esperamos sea de utilidad para trabajos posteriores.

Mineralogy and geochemistry of sulfide minerals and bulk rocks from ODP Hole 176-735B

Ocean Drilling Program (ODP) Leg 176 built upon the work of ODP Leg 118 wherein the 500-m section that was sampled represented the most complete recovery of an intact portion of lower oceanic crust ever described. During Leg 176, we deepened Hole 735B to >1500 m below seafloor in an environment where gabbroic rocks have been tectonically exposed at the Southwest Indian Ridge. This new expedition extended the remarkable recovery (>85%) that allowed unprecedented investigations into the nature of the lower oceanic crust as a result of Leg 118. Sulfide mineral and bulk rock compositions were determined from samples in the 1000-m section of oceanic gabbros recovered during Leg 176. The sulfide assemblage of pyrrhotite, chalcopyrite, pentlandite, and troilite is present throughout this section, as it is throughout the 500-m gabbroic section above that was sampled during Leg 118. Troilite is commonly present as lamellae, and the only interval where troilite was not observed is from the uppermost 150 m of the section sampled during Leg 118, which is intensely metamorphosed. The common presence of troilite indicates that much of the sulfide assemblage from Hole 735B precipitated from a magmatic system and subsequently underwent low-temperature reequilibration. Evaluation of geochemical trends in bulk rock and sulfides indicates that the combined effects of olivine accumulation in troctolites and high pentlandite to pyrrhotite ratios account for the sporadic bulk rock compositions high in Ni. Bulk rock and sulfide mineral geochemical indicators that are spatially coincident with structural and physical properties anomalies indicate a heretofore unrecognized lithologic unit boundary in this section. Platinum-group element (PGE) compositions were also determined for 36 samples from throughout the section that were recovered during Leg 176. Whereas most samples had low (<0.4 ppb) PGE concentrations, rare samples had elevated PGE values, but no unique common trend between these samples is evident.

Physicochemical characteristics and protist occurrence at stations sampled in 2007/2008 in the eastern Beaufort Sea

This study documents, for the first time, the abundance and species composition of protist assemblages in Arctic sea ice during the dark winter period. Lack of knowledge of sea-ice assemblages during the dark period has left questions about the retention and survival of protist species that initiate the ice algal bloom. Sea-ice and surface water samples were collected between December 27, 2007 and January 31, 2008 within the Cape Bathurst flaw lead, Canadian Beaufort Sea. Samples were analyzed for protist identification and counts, chlorophyll (chl) a, and total particulate carbon and nitrogen concentrations. Sea-ice chl a concentrations (max. 0.27 µg/l) and total protist abundances (max. 4 x 10**3 cells/l) were very low, indicating minimal retention of protists in the ice during winter. The diversity of winter ice protists (134 taxa) was comparable to spring ice assemblages. Pennate diatoms dominated the winter protist assemblage numerically (averaging 77% of total protist abundances), with Nitzschia frigida being the most abundant species. Only 56 taxa were identified in surface waters, where dinoflagellates were the dominant group. Our results indicate that differences in the timing of ice formation may have a greater impact on the abundance than structure of protist assemblages present in winter sea ice and at the onset of the spring ice algal bloom.

Abundance and biomass of zooplankton collected in 1995 and 1998 in the frontal zone between the Gulf Stream and the Labrador current

Vertical distribution of meso- and macroplankton was studied in the region of the most sharply pronounced climatic frontal zone between the Gulf Stream and the Labrador current. Hauls with a plankton net BR 113/140 and visual counts of macroplankton from the Mir submersible were used. In the frontal zone a contact occurs between arctic-boreal communities and communities of the North Atlantic subtropical gyre. The community of the North Atlantic subtropical gyre is more mature in terms of succession; many macroplanktonic carnivores-scavengers (mainly shrimps Acanthephyra) develop there and form a ''living network'' feeding on those transported from the north rich arctic-boreal mesoplankton. As a result biomass of shrimps appears to be significantly higher than biomass of their preys. Peculiarities of vertical distribution and population structure of shrimps were analyzed. Data on quantitative vertical distribution of total biomass of meso- and macroplankton and its principal groups, including gelatinous animals (ctenophores, medusas, and siphonophores) were obtained. Variations of the role of different plankton groups with depth were considered; these data enable a conclusion that frontal variations of the community structure embrace the depth range from the surface down to 2000 m.