TL and OSL properties of KAlSi(3)O(8):Mn, obtained by sol-gel process

Thermoluminescence (TL) and Optically Stimulated Luminescence (OSL) properties of KAlSi(3)O(8):Mn glasses obtained through the sol gel technique were investigated. Samples were obtained with five different molar concentrations of 0.25, 0.5, 1, 2 and 5 mol% of manganese. Transmission Electronic Microscopy (TEM) indicated the occurrence of nanoparticles composed by glass matrix elements with Mn. Best results for TL response were obtained with 0.5 mol% Mn doped sample, which exhibits a TL peak at 180 degrees C. The TL spectrum of this sample presents a broad emission band from 450 to 700 nm with a peak at 575 nm approximately. The emission band fits very well with the characteristic lines of the Mn(2+) emission features. According to this fact, the band at 410 nm can be ascribed to (6)A(1)(S) -> (4)A(1)(G), (4)E(G) transition, while the 545 nm band can be attributed to the superposition of the transitions (6)A(1)(S) -> (4)T(2)(G) and (6)A(1)(S) -> (4)T(1)(G). The dependence of the TL response with the energy of X-rays (27-41 keV) showed a small decrease of the TL intensity in the high energy region. Excitation with blue LEDs showed OSL in the UV region with a fast decay component. (C) 2011 Elsevier Ltd. All rights reserved

Thermo luminescence and optically stimulated luminescence characteristics of Al2O3 doped with Tb

In the present work policrystals of alpha - Al2O3 doped with terbium were synthesized using the solvent evaporation method. the samples were prepared using Al(NO3)(3)center dot 9H(2)O and Tb(NO3)(3).5H(2)O reagents, with Tb concentrations between 1 and 5 mol% and thermally treated at high temperature above similar to 1400 degrees C. X-ray diffraction measurements showed the a-phase formation of samples. TL glow curve presented an intense peak at similar to 190 degrees C and two other with low intensity at 290 and 350 degrees C after gamma irradiation. the best doping concentration which presented high luminescence was the sample doped with 3 mol% of Tb. U spectra and fluorescence measurements showed similar luminescence spectra with lines attribute to Tb3+ ions. A linear behavior to gamma dose between 1 and 20 Gy was observed in TL, using 190 degrees C peak as well as in OSL signal, this last carried out using 532 nm wavelength stimulation. (C) 2014 Elsevier B.V. All rights reserved.Technol Fac São Paulo, São Paulo, BrazilUniversidade Federal de São Paulo, Santos, BrazilUniversidade Federal de São Paulo, Santos, BrazilWeb of Scienc

Pleistocene-Holocene sedimentation of Solimões-Amazon fluvial system between the tributaries Negro and Madeira, Central Amazon

ABSTRACT: In the scope of Solimões-Amazon fluvial system between the Negro and Madeira tributaries, three levels of Quaternary fluvial terraces overlie the Alter do Chão and Novo Remanso formations further than 100 km southward its current main channel. Smooth undulated topography presenting low drainages density formed by sparse secondary plain channels and rounded lakes characterizes these deposits. Internally, they show point bars morphology constituted by intercalated layers of mud (silt and clay) and sand forming an inclined heterolithic stratification. The asymmetric distribution of fluvial terraces allied to the records of old scroll-bars features and paleochannels in many extensions of the Solimões River suggests the predominance of a meander pattern between 240 to 6 kyears. On the other hand, the development of the current anabranching pattern took place in the last six kyears due to the Holocene sea-level rise, besides the action of neotectonics and rainforest establishment related to the increase of humidity in Amazonia

OSL dating of sediments from Negro and Solimoes rivers - Amazon, Brazil

In this work, the OSL dating results of Quaternary fluvial deposits from the confluence of Negro and Solimoes rivers were studied. the equivalent doses (D-e) of sediments were obtained using a Single Aliquot Regeneration (SAR) protocol. Statistic studies were made using frequency histogram, weighted histogram and Radial plot in order to analyze the D-e fluctuations. Ages from 74.5 to 205 thousand of years (Pleistocene) were recorded. the gamma-ray spectroscopy was used to evaluate the natural radioisotopes concentrations of the samples and low concentrations were found with values between 0.64 and 3.71 ppm for U-235 and U-238; 2.01-9.77 ppm for Th-232; already, for K-40, the concentration was negligible. the OSL dating of sediments has contributed to a better understanding of the evolution of Negro and Solimbes rivers, in Amazon, Brazil. (C) 2013 Elsevier B.V. All rights reserved.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fac Tecnol São Paulo FATEC SP, BR-01124060 São Paulo, BrazilUniv Fed Amazonas, Manaus, Amazonas, BrazilUniversidade Federal de São Paulo, BR-11030900 Santos, BrazilUniversidade Federal de São Paulo, BR-11030900 Santos, BrazilFAPESP: 2009/02069-2Web of Scienc