979 resultados para Fluvial Abrasion
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Pós-graduação em Medicina Veterinária - FMVZ
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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Este trabalho apresenta as características do meio físico da Bacia do Rio Bacanga, localizada na cidade de São Luís (MA). Dentro da compartimentação geomorfológica regional, a área insere-se no Golfão Maranhense, sendo caracterizada por duas unidades de relevo: colinas dissecadas a partir dos tabuleiros e planícies flúvio-marinhas. Os estudos objetivaram a elaboração de um mapa geológico- geotécnico, fundamentado no método do detalhamento progressivo, sendo integradas as informações geológicas, geomorfológicas e de solos em uma base topográfica na escala de 1:20.000. Para esses estudos foi utilizada como ferramenta principal a fotointerpretação detalhada, associada ao controle de campo e ensaio in situ. No mapa resultante foram caracterizadas seis unidades geológico-geotécnicas: Unidade I – depósitos construídos; Unidade II – áreas planas de fundo de vales; Unidade III – terrenos associados à fácies arenosa da Formação Barreiras; Unidade IV – fácies areno-argilosa da Formação Barreiras; Unidade V – área de domínio da fácies areno-argilosa da Formação Barreiras; Unidade VI – domínio da Formação Itapecuru. Nas unidades foram identificados os processos geológicos e os problemas ambientais que compõem a dinâmica da bacia do Rio Bacanga. O mapa elaborado é uma das ferramentas indispensáveis para subsidiar o planejamento do uso e ocupação do solo. Palavras-chave: mapeamento geológico-geotécnico, relevo de tabuleiro, Rio Bacanga, São Luís (MA).
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Mediante a aplicação de técnicas de análise flúviomorfométricas disponíveis na literatura especializada, tais como estudo dos perfis longitudinais dos cursos d’água e os índices RDE (Relação Declividade vs. Extensão), buscou-se, neste trabalho, executar uma análise de prováveis deformações neotectônicas na região do Pontal do Paranapanema, extremo oeste do Estado de São Paulo. Dessa forma, a análise dos parâmetros flúvio-mofométricos proposta foi aplicada nas bacias hidrográficas menores que drenam tanto para o rio Paranapanema, ao sul, quanto para o rio Paraná, a oeste. As medidas foram efetuadas, inicialmente, nas drenagens com extensão superior a 8 km, tendo como base topográfica as folhas plani-altimétricas em escala 1:50.000, com equidistância de 20 m, editadas pelo IBGE e pelo IGC, totalizando 22 cartas topográficas. Os dados coletados foram lançados em planilhas Excel para a obtenção dos resultados gráficos e definição das anomalias. Utilizou-se de base geológica em escala 1:500.000 editada pelo IPT (1981), para comparação dos dados fluviomorfométricos com o substrato geológico sulcado pelos cursos d’água. Os trabalhos finais envolveram o cotejamento de todas as informações flúvio-morfométricas e geológicas e a interpretação das anomalias delimitadas. Para tanto se fez necessário elaborar uma base morfoestrutural adequada, que se baseou na análise de imagens de satélite do sistema SRTM, da NASA, com o auxilio do aplicativo Global Mapper. Os dados de morfometria fluvial indicaram a presença de um significativo número de anomalias, com destaque para trechos subsidentes de cursos d’água e também para perfis longitudinais retilíneos de drenagem, que se destacam do padrão logarítmico típico dos rios. Tais trechos foram interpretados como tectonicamente desequilibrados, indicando deformações crustais recentes. As anomalias flúviomorfométricas foram comparadas com áreas de solos espessos, interpretadas em imagens SRTM, e com a trama de lineamentos, confirmando que as áreas mais dissecadas correspondem a trechos com movimentação ascencional, que resulta em solos rasos e presença de anomalias de RDE. Os terrenos com solos mais espessos, por outro lado, abrangem áreas em subsidência, que podem incluir depósitos aluviais mais expressivos. Não-raro, estas áreas são demarcadas por limites estruturais (lineamentos) e/ou por trechos de perfis longitudinais anômalos de drenagens. Palavras-chave: Pontal do Paranapanema; morfometria fluvial; neotectônica; geomorfologia fluvial.
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The Pantanal is a Quaternary sedimentary basin located at the left margin of the Upper Paraguay River, west-central Brazil. Basin infilling was mainly by siliciclastic sediments and the stratigraphic succession exhibits an overall finingupward pattern. The depositional system tract is composed by a large meandering fluvial plain and several marginal alluvial fans, being the Taquari megafan the most striking feature. The present landscape is a complex tropical wetland, with geomorphic features derived from the present conditions and other inherited from successive Pleistocene and Holocene climates. During the Pleistocene, the sedimentary environment was dominated by braided alluvial fans, the original geometry of which is preserved as relict forms, permitting remarkable patterns of distributary paleochannels to be easily recognized in satellite images. Eolian processes were active in some abandoned lobes, contemporaneously with sedimentation in active fan lobes. Closed ponds bordered by lunette sand dunes, originally salt pans produced by eolian deflation, are relict eolian landforms in the Pantanal landscape. Eolian processes were probably more effective at the glacial maximum. Landscape has been changing in the Pantanal area since the end of the Pleistocene in adaptation to a more humid and warmer environment prevailing during Holocene. Initiation of the modern wetland has occurred during the Pleistocene / Holocene transition, with the change to a more humid climate and the individualization of lacustrine systems. The modern Pantanal wetland is a vast expanse of poorly drained lowlands that experiences annual flooding from summer to fall months. Although climatic fluctuations have occurred during all the Holocene, the alluvial fans have remained active depositional systems and lobes were formed by progradation and abandonment. Abandoned lobes were subjected... (Complete abstract click electronic address below)
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Pós-graduação em Ciências Biológicas (Botânica) - IBB
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Pós-graduação em Engenharia Civil - FEIS
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Pós-graduação em Reabilitação Oral - FOAR
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Far from the continental margin, drainage basins in Central Amazonia should be in topographic steady state; but they are not. Abandoned remnant fluvial valleys up to hundreds of square kilometers in size are observed throughout Amazonia, and are evidence of significant landscape reorganization. While major Late Miocene drainage shifts occurred due to initiation of the transcontinental Amazon River, local landscape change has remained active until today. Driven either by dynamic topography, tectonism, and/or climatic fluctuations, drainage captures in Amazonia provide a natural experiment for assessing the geomorphic response of low-slope basins to sudden, capture related base-level falls. This paper evaluates the timing of geomorphic change by examining a drainage capture event across the Baependi fault scarp involving the Cuieiras and TarumA-Mirim River basins northwest of the city of Manaus in Brazil. A system of capture-related knickpoints was generated by base-level fall following drainage capture; through numerical modeling of their initiation and propagation, the capture event is inferred to have occurred between the middle and late Pleistocene, consistent with other studies of landscape change in surrounding areas. In low-slope settings like the Amazon River basin, base-level fall can increase erosion rates by more than an order of magnitude, and moderate to large river basins can respond to episodes of base-level fall over timescales of tens to hundreds of thousands of years. Copyright (c) 2013 John Wiley & Sons, Ltd.
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This study compared the effect of physicochemical surface conditioning methods on the adhesion of bis-GMA-based resin cement to particulate filler composite (PFC) used for indirect dental restorations. PFC blocks (N (block)=54, n (block)=9 per group) were polymerized and randomly subjected to one of the following surface conditioning methods: a) No conditioning (Control-C), b) Hydrofluoric acid (HF)etching for 60s (AE60), c) HF for 90s (AE90), d) HF for 120s (AE120), e) HF for 180s (AE180), and f) air-abrasion with 30 mu m silica-coated alumina particles (AB). The conditioned surfaces were silanized with an MPS silane, and an adhesive resin was applied. Resin composite blocks were bonded to PFC using resin cement and photo-polymerized. PFC-cement-resin composite blocks were cut under coolant water to obtain bar specimens (1mmx0.8mm). Microtensile bond strength test (mu TBS)was performed in a universal testing machine (1mm/min). After debonding, failure modes were classified using stereomicroscopy. Surface characterization was performed on a set of separate specimen surfaces using Scanning Electron Microscopy (SEM), X-Ray Dispersive Spectroscopy (XDS), X-Ray Photoelectron Spectroscopy (XPS), and Fourier Transform-Raman Spectroscopy (FT-RS). Mean mu TBS (MPa) of C (35.6 +/- 4.9) was significantly lower than those of other groups (40.2 +/- 5.6-47.4 +/- 6.1) (p<0.05). The highest mu TBS was obtained in Group AB (47.4 +/- 6.1). Prolonged duration of HF etching increased the results (AE180: 41.9 +/- 7), but was not significantly different than that of AB (p>0.05). Failure types were predominantly cohesive in PFC (34 out of 54) followed by cohesive failure in the cement (16 out of 54). Degree of conversion (DC) of the PFC was 63 +/- 10%. SEM analysis showed increased irregularities on PFC surfaces with the increased etching time. Chemical surface analyses with XPS and FT-RS indicated 11-70% silane on the PFC surfaces that contributed to improved bond strength compared to Group C that presented 5% silane, which seemed to be a threshold. Group AB displayed 83% SiO2 and 17% silane on the surfaces.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Purpose: To compare the shear bond strength (SBS) of two cements to two Y-TZP ceramics subjected to different surface treatments.Materials and Methods: Zirconia specimens were made from Lava (n = 36) and IPS e.max ZirCAD (n = 36), and their surfaces were treated as follows: no treatment (control), silica coating with 30-mu m silica-modified alumina (Al2O3) particles (CoJet Sand), or coating with liners Lava Ceram for Lava and Intensive ZirLiner for IPS e.max ZirCAD. Composite resin cylinders were bonded to zirconia with Panavia F or RelyX Unicem resin cements. All specimens were thermocycled (6000 cycles at 5 degrees C/55 degrees C) and subjected to SBS testing. Data were analyzed by post-hoc test Tamhane T2 and Scheffe tests (alpha = 0.05). Failure mode was analyzed by stereomicroscope and SEM.Results: With both zirconia brands, CoJet Sand showed significantly higher SBS values than control groups only when used with RelyX Unicem (p = 0.0001). Surface treatment with liners gave higher SBS than control groups with both ceramic brands and cements (p < 0.001). With both zirconia brands, the highest SBS values were obtained with the CoJet and RelyX Unicem combination (> 13.47 MPa). Panavia F cement showed significantly better results when coupled with liner surface treatment rather than with CoJet (p = 0.0001, SBS > 12.23 MPa). In untreated controls, Panavia F showed higher bond strength than RelyX Unicem; the difference was significant (p = 0.016) in IPS e.max ZirCAD. The nontreated specimens and those treated with CoJet Sand exhibited a high percentage of adhesive and mixed A (primarily adhesive) failures, while the specimens treated with liners presented an increase in mixed A and mixed C (primarily cohesive) failures as well as some cohesive failure in the bulk of Lava Ceram for both cements.Conclusion: CoJet Sand and liner application effectively improved the SBS between zirconia and luting cements. This study suggests that different interactions between surface treatments and luting cements yield different SBS: in clinical practice, these interactions should be considered when combining luting cements with surface treatments in order to obtain the maximum bond strength to zirconia restorations.