23 research outputs found

    Luminescence characteristics of quartz from Brazilian sediments and constraints for OSL dating

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    This study analyzes the optically stimulated luminescence (OSL) characteristics of quartz grains from fluvial, eolian and shallow marine sands of northeastern and southeastern Brazil, with especial focus on the applicability of the single-aliquot regenerative dose (SAR) dating protocol. All analyzed Brazilian sediments presented relatively high OSL sensitivity and good behavior regarding their luminescence characteristics relevant for radiation dose estimation. However, some samples from the Lençóis Maranhenses region in northeastern Brazil showed inadequate OSL sensitivity correction, hampering the implementation of the SAR protocol and their ability to behave as a natural dosimeter. While the shallow marine and eolian samples showed a narrow and reliable dose distribution, the fluvial sample had a wide dose distribution, suggesting incomplete bleaching and natural doses estimates dependent on age models

    The inventory of geological heritage of the state of SĂŁo Paulo, Brazil: Methodological basis, results and perspectives

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    An inventory of geological sites based on solid and clear criteria is a first step for any geoconservation strategy. This paper describes the method used in the geoheritage inventory of the State of SĂŁo Paulo, Brazil, and presents its main results. This inventory developed by the geoscientific community aimed to identify geosites with scientific value in the whole state, using a systematic approach. All 142 geosites representative of 11 geological frameworks were characterised and quantitatively evaluated according to their scientific value and risk of degradation, in order to establish priorities for their future management. An online database of the inventory is under construction, which will be available to be easily consulted and updated by the geoscientific community. All data were made available to the State Geological Institute as the backbone for the implementation of a future state geoconservation strategy.The authors acknowledge the Science Without Borders Programme, Process 075/2012, which supported this study and the SĂŁo Paulo Research Foundation (FAPESP), Process 2011/17261-6. We also thanks C. Mazoca for his help with maps and figures.info:eu-repo/semantics/acceptedVersio

    Gene diversity in grevillea populations introduced in Brazil and its implication on management of genetic resources.

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    A variabilidade isoenzimĂĄtica para seis populaçÔes de Grevillea robusta, oriundas de um teste de procedĂȘncias/progenies, implantado no delineamento em blocos casualizados com 5 plantas por parcela, no Sul do Brasil, Ă© descrita. A estrutura genĂ©tica da população foi analisada utilizando-se marcadores bioquĂ­micos, aos 5 anos de idade, especificamente para os locos MDH-3, PGM-2, DIA-2, PO-1, PO-2, SOD-1, e SKDH-1. As procedĂȘncias do norte de ocorrĂȘncia natural (Rathdowney e Woodenbong) apresentaram divergĂȘncia genĂ©tica superior, em relação Ă  mĂ©dia das progĂȘnies, considerando o nĂșmero de alelos por locus, (Ap), a riqueza alĂ©lica (Rs), a diversidade genĂ©tica de Nei (H), e o coeficiente de endogamia (f). A endogamia foi detectada em diversos graus. A testemunha comercial apresentou o maior coeficiente de endogamia, (f = 0,4448), comparativamente Ă  mĂ©dia das procedĂȘncias (f = 0,2306), possivelmente devido Ă  insuficiente amostragem populacional na regiĂŁo de origem (AustrĂĄlia). Apesar de sua ocorrĂȘncia natural restrita, observou-se correlação positiva entre divergĂȘncia genĂ©tica e distĂąncia geogrĂĄfica entre as populaçÔes originais. A distĂąncia genĂ©tica e anĂĄlise de cluster, baseada no modelo bayesiano, mostrou trĂȘs grupos de procedĂȘncias distintos: 1) Rathdowney- QLD e Woodenbong-QLD; 2) Paddy?s Flat-NSW; e 3) Mann River-NSW, Boyd River-NSW e a testemunha comercial (material utilizado no Brasil). O agrupamento da testemunha com as procedĂȘncias Mann River-NSW e Boyd River-NSW sugere um maior potencial das procedĂȘncias do norte para o melhoramento genĂ©tico visando Ă  produção de madeira no Brasil, devido a sua elevada diversidade genĂ©tica e baixo coeficiente de endogamia

    Major shear zones of southern Brazil and Uruguay: escape tectonics in the eastern border of Rio de La plata and Paranapanema cratons during the Western Gondwana amalgamation

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    Effect of storage in water and thermocycling on hardness and roughness of resin materials for temporary restorations

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    PURPOSE: This study evaluated the effect of storage in water and thermocycling on hardness and roughness of resin materials for temporary restorations. MATERIAL AND METHODS: Three acrylic resins (Dencor-De, Duralay-Du, and Vipi Cor-VC) were selected and one composite resin (Opallis-Op) was used as a parameter for comparison. The materials were prepared according to the manufacturers' instructions and were placed in stainless steel moulds (20 mm in diameter and 5 mm thick). Thirty samples of each resin were made and divided into three groups (n = 10) according to the moment of Vickers hardness (VHN) and roughness (Ra) analyses: C (control group): immediately after specimen preparation; Sw: after storage in distilled water at 37 °C for 24 hours; Tc: after thermocycling (3000 cycles; 5-55 °C, 30 seconds dwell time). Data were submitted to 2-way ANOVA followed by Tukey's test (&#945; = 0.05). RESULTS: Op resin had higher surface hardness values (p < 0.0001; 25.4 ± 3.4) than the other ones (De = 4.5 ± 0.6; Du = 5.5 ± 0.4; VC = 6.1 ± 0.9). There was no statistical difference (p > 0.05) in roughness among materials (De = 0.31 ± 0.07; Du = 0.51 ± 0.20; VC = 0.41 ± 0.15; Op = 0.42 ± 0.18). Storage in water did not change hardness and roughness of the tested materials (p > 0.05). There was a significant increase in roughness after thermocycling (p < 0.05), except for material Du, which showed no significant change in roughness in any evaluated period (p = 0.99). CONCLUSION: Thermocycling increased the roughness in most tested materials without affecting hardness, while storage in water had no significant effect in the evaluated properties
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