Este estudo apresenta alguns resultados geofisicos obtidos no Mesón San Juan localizado na Cordilheira dos Andes (6.012 m, 33°30'S e 69°49'W), na divisa entre a Argentina e o Chile. Oplatô de permafrost (4.400 m) está situado na base da geleira, limitado por morenas produzidas por fenômenos criogênicos recentes. Os resultados geofisicos mostraram variações laterais nas características dielétricas na subsurperfície devido a diferentes porcentagens de água, permitindo o zoneamento qualitativo da estrutura do permafrost . As permissividades elétricas foram comparadas de um modo semiquantitativo através do procedimento de migração "trial-and-error", tirando proveito do "clutter" do permafrost . Foi possível reconhecer uma zona confinada de baixa velocidade de fase, que indica porosidade e quantidade de água mais elevadas. Essa zona foi interpretada como sendo permafrost degradado, provavelmente resultante do impacto do aquecimento global sobre o ambiente glacial andino, possível canal de descarga de um suprapermafrost a um aqüífero subpermafrost , parte de um sistema raso e descontínuo, não mapeado neste trabalho.

This work presents some geophysical results obtained at Mesón San Juan located in the Central Andes (6,012 m, 33°30' Sand 69°49' W), on the border of Argentina and Chile. The permafrost plateau (4,400 m) situated at the loot of the glacier is limited by recent moraines produced by cryogenic phenomena. The geophysical results revealed lateral differences in the dielectric characteristics of the subsurface due to varying water contents, allowing a zoning of the permafrost structure. We have compared the electrical permittivities in a semi-quantitative way through a trial-and-error migration procedure, taking advantage of the clutter present in the permafrost as seen in the fixed-offset data. In this way we were able to recognize a confined zone of relatively low phase velocity indicating higher porosity and water content. We interpret that zone as degraded permafrost , probably a result of the impact of global warming on the Andean cryolithozone. That zone is likely a discharge channel linking a suprapermafrost to a subpermafrost aquifer, part of a laterally discontinuous near surface system not mapped in this work.

A study was made of the variation of the magnetic properties of cobalt-based alloys using different compositions of CoFeSiB and CoFeSiBCr systems, which were produced by the melt-spinning technique and some of them subjected to a stress annealing treatment. A comparative study of core geometry and supporting material was also performed in order to obtain low noise fluxgate sensor core using amorphous magnetic ribbons of these alloys. The best alloy was a stress annealed Co67.5Fe3.5Si17.4B11.6 sample, which yielded fluxgate sensors with lower noise levels than those of commercial crystalline materials.

The incorporation of micrometer sized silica particles on poly (ethylene-co-vinyl acetate) - EVA - residues from the footwear industry was evaluated. The effects of the processing parameters - temperature and mixing ratio - on the mechanical behavior of molded plates of neat recycled EVA and EVA/silica composites were also investigated. The mechanical properties measured by the tensile test, the fractographic analysis by scanning electron microscopy (SEM), and the 13C Nuclear Magnetic Resonance (NMR) showed a reduced EVA to silica compatibility. Therefore, incorporation of untreated silica to recycled EVA copolymer produced a slight decrease on the mechanical performance of EVA/silica composites in respect to neat EVA copolymer. The NMR analysis also shows that the crosslinking process on recycled EVA may be occurring at the carbonyl group.