BRUNA CORTEZ
7 resultados
Resultados de Busca
Agora exibindo 1 - 7 de 7
Artigo IPEN-doc 27872 EPR dating of sediments in the region of Iguape - Cananéia, Brazil2021 - CORTEZ, B.; CHUBACI, J.F.D.; GOMES, M.B.; MENDES, L.; ROCCA, R.R.; ARIZACA, E.C.E.; WATANABE, S.Dating of sediments was performed by physics method in this work. Natural radioactivity is present in sediments, and this method is based on the measurement of energy of radiation stored in the solid. Gamma irradiation of sediments create deffects in quartz structure that stores energy by the absorption of radiation. In the present work, Icapara sediment dating was done by Electron Paramagnetic Resonance (EPR) spectroscopy method. The intensity of EPR signal corresponding to the number of lattice defects with an unpaired electron in sediment quartz could be measured to estimate the accumulated dose of natural radiation and to calculate the geologic age. Located in the region of Iguape at southeast coast of São Paulo State, Icapara is a large sand terrace that was formed due to sea level fluctation that occurred more than 130 thousand years ago. Samples were taken from a point about 9 - 10 meters above the current control of the sea. Ages of 38,000 ±12,000 and 46,000 ± 7,000 years were obtained in this study by EPR analysis that are correlated with the Quaternary Period.Artigo IPEN-doc 27423 Study of thermoluminescence of green quartz pellets for low dose dosimetry2020 - CUEVAS-ARIZACA, E.E.; MAXIMO RONDON, R.; ROCCA, R.R.; GOMES, M.B.; CORTEZ, B.; GONZALES-LORENZO, C.D.; TAKARA, J.H.; GUNDU RAO, T.; CANO, N.F.; CHUBACI, J.F.D.; CAMPOS, L.L.; WATANABE, S.Green quartz is usually studied for low dose TL dosimetry of gamma and X radiation. The aim of the present work is the dosimetric characterization of natural green quartz in the dose range of 0.47 mGy up to 1000 mGy of gamma and X radiation. Green quartz pellets were produced by cold pressing green quartz powder. The pellets are very sensitive to gamma and X radiation with main prominent TL peak at 230 °C. The TL sensitivity of MTS-N (LiF:Mg,Ti) and green quartz pellets were also compared. The dose response curve presented linear behavior in the dose range studied. The glow curve was deconvoluted. Kinetic parameters such as trap depth, kinetic order (b) and frequency factor (s) are determined. The TL photon energy dependence was also evaluated.Dissertação IPEN-doc 27290 Datação de sedimentos Pleistocênicos do terraço arenoso da região de Icapara - São Paulo, Brasil2020 - CORTEZ, BRUNAO presente trabalho relata idades obtidas por métodos físicos, que correlacionam ao período Pleistocênico, Sistema Laguna-Barreira II. No estado de São Paulo, na região de Icapara localizado no litoral sudeste, 10 km de distância da costa um grande terraço foi formado. Essa formação pode estar vinculado às flutuações do nível relativo do mar no passado (NRM), que ocorreram há mais de 120 000 anos passados. A determinação da idade das amostras coletadas foram realizadas utilizando os grãos de quartzo através das técnicas de métodos físicos como Termoluminescência (TL) e Ressonância Paramagnética Eletrônica (RPE). A análise da estrutura cristalina do quartzo após tratamentos químicos foram realizadas por Difração de Raios-X, contendo a presença de fases cristalinas devido a cristobalita, feldspato e quartzo. A curva de emissão TL apresenta picos em torno de 110°C e 325°C para todas as amostras. Devido à estabilidade do pico em 325°C foi utilizado para determinar a dose acumulada (Dac) por método aditivo. O espectro RPE dos grãos de quartzo mostra o sinal E'1 na região g= 2,00053. Através de processo de sensibilização com temperatura em 320°C das amostras irradiadas com diferentes doses foi construído o comportamento da intensidade RPE em função da dose regenerativa para determinar a Dac. O teor de U, Th e K nas amostras foram determinados por espectroscopia-gama, e por medida das concentrações destes radionuclídeos obtemos a taxa de dose anual, das amostras coletadas em Icapara. As idades obtidas por amostras técnicas correlacionam ao período Pleistocênico, que correspondem idades entre 35 000 a 48 000 anos passados.Artigo IPEN-doc 27230 EPR dating of shells from Malhada Marsh, Rio de Janeiro, Brazil2020 - GOMES, M.B.; OLIVEIRA, L.M.; CORTEZ, B.; D'OCA, M.C.; TRANCHINA, L.; TOMARCHIO, E.; PARLATO, A.; CHUBACI, J.F.D.; GENNARI, R.; ROCCA, R.R.; D'ERRICO, F.; SOUSA, S.; WATANABE, S.; MARRALE, M.The formation of the coastal plain of the Brazilian sea is mainly due to the fl uctuation of relative sea level in the past. Armação dos Buzios or simply Buzios is a municipality in the microregion of lakes, in the state of Rio de Janeiro. In this region there is a lowland area about two meters above current sea level. This lowland area is also known as coastal plain of Una River. It is expected that during the Holocene period the sea level reached a maximum about 2.5 meters above the current level. During that time billions of mollusks lived and proliferated in the shallow waters around the coastal plain of the Una River. As they died their shells formed a layer in the soil including Malhada Marsh that belongs to the Una River plain. In this study, shells were collected from this region and dated using the techniques of Electronic Paramagnetic Resonance (EPR). Ages from 2480±130 to 4490±270 years were obtained. Radiocarbon dating were performed at the Beta Analytic Lab, USA for comparison with the EPR results. Shells ages obtained are compatible with geological data from the Holocene period relative to past sea level fl uctuations.Artigo IPEN-doc 27229 Electron Spin Resonance and Thermoluminescence dating of shells and sediments from Sambaqui (shell mound) Santa Marta II, Brazil2020 - OLIVEIRA, L.M.; GOMES, M.B.; CORTEZ, B.; D'OCA, M.C.; TRANCHINA, L.; TOMARCHIO, E.; PARLATO, A.; CHUBACI, J.F.D.; GENNARI, R.; ROCCA, R.R.; D'ERRICO, F.; SOUSA, S.; WATANABE, S.; MARRALE, M.In Tupi, the word Sambaqui means “mound of shells”. These archaeological sites are cultural vestiges left by the prehistoric occupation of the Brazilian coast from fi ve to six thousand years ago. Mollusks, fi shes, and other marine edible foods were important for the survival of this population. The remains of foods, mainly shells, were heaped up, giving a mound of different proportions, which became part of the landscape of the Brazilian coastal plain. Due to the large number of Sambaquis in Brazil and considering that Sambaqui Santa Marta II, Laguna, SC, has not yet been dated, Electron Spin Resonance (ESR) measurements were performed in aragonite shells collected from different layers of Sambaqui Santa Marta II, starting from the base to the center of the Sambaqui. Radiocarbon analysis by Accelerator Mass Spectrometry (AMS) at Beta Analytic laboratory were also performed for comparison with ESR results. Before measurements, shells were chemically etched, after drying, were pulverized and sieved. The sediments were separated into small portions which were irradiated with gamma radiation from a 60Co source with doses from 5 up to 120 Gy. Ages around 2,000 to 4,000 years have been obtained. The results obtained are consistent with the dates of others Sambaquis of the region, possibly were built at the same time.Resumo IPEN-doc 26028 Dating sediments from a terrace found in Iguape - Icapara in southeast coast in the state of São Paulo, Brazil2018 - CORTEZ, BRUNA; CHUBACI, JOSE F.D.; GOMES, MONISE B.; OLIVEIRA, LETICIA M.; SATIRO, LUCAS C.; ROCCA, RENE R.; ARIZACA, EDY E.C.; WATANABE, SHIGUEOResumo IPEN-doc 26027 Dating of shells from Pântano da Malhada, Rio de Janeiro2018 - GOMES, MONISE B.; CORTEZ, BRUNA; OLIVEIRA, LETICIA M. de; CARMO, LUCAS S. do; CHUBACI, JOSE F.D.; ROCCA, RENE R.; WATANABE, SHIGUEO