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Dosimetria usando luminecência opticamente estimulada: aplicações, propriedades físicas e caracterização de materiais dosimétricos; Dosimetry using optically stimulated luminescence: applications, physical properties and dosimeter detectors characterization

Nascimento, Luana de Freitas
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 10/08/2007 PT
Relevância na Pesquisa
66.64%
Dosimetria usando Luminescência Opticamente Estimulada (OSL) é uma área em constante crescimento dentro da ciência e com excelentes perspectivas comerciais. O Óxido de Alumínio crescido na presença de uma atmosfera rica em Carbono (Al 2O3:C) tem fornecido bons resultados como detector luminescente. Esse material apresenta alta sensibilidade à radiação ionizante e boa resposta à estímulos ópticos. Estima-se que cerca de dois milhões de pessoas façam uso de dosímetros com detectores de Al 2O3:C em rotinas de dosimetria individual externa, que por apresentar varias vantagens experimentais acredita-se substituirá as outras duas técnicas dosimétricas mais adotadas: dosimetria fotográfica e termoluminescente. A certificação de uma técnica de dosimetria para uso comercial exige uma série de estudos. Neste trabalho apresentamos contribuições que complementam o entendimento e adoção da técnica de OSL em dosimetria pessoal. Nossa primeira contribuição consiste numa serie de testes de desempenho mostrando a eficácia da técnica para justificar nossa proposta de certificação de dosimetria individual externa usando OSL no Brasil. No intuito de relacionar centros paramagnéticos e o processo de luminescência, apresentamos resultados de espectros de EPR em detectores OSL. Detectamos e classificamos sinais de EPR relacionados a impurezas nas amostras...

Caracterização de silicatos e carbonatos de cálcio aplicados à dosimetria de doses altas; Characterization of silicates and calcium carbonates applied to high-dose dosimetry

Vila, Gustavo Barretto
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 12/03/2013 PT
Relevância na Pesquisa
46.26%
A forma isomórfica predominante nos biominerais (casca de ostra, coral, madrepérola e concha) estudados foi a aragonita. Contudo, o surgimento da fase calcita deu-se à temperatura de 500°C a uma taxa de aquecimento de 10°C/s para todas as amostras; e para a amostra de coral, à temperatura de 400°C, independente da taxa de aquecimento. O elemento mais abundante nas amostras de biominerais foi o Ca na forma de CaO e para os silicatos (tremolita, diopsídio e rodonita), o Si na forma de SiO. O elemento traço mais presente nas amostras de biominerais foi o Fe. A análise de ressonância paramagnética eletrônica mostrou as linhas de Mn2+ nas amostras de coral e madrepérola, antes da irradiação. Para amostras irradiadas, os defeitos encontrados foram os radicais CO2-, CO33-, CO3-, SO2-, SO3-, e num intervalo de g entre 2,0010 e 2,0062. Na análise por absorção óptica dos biominerais foram encontradas transições devido à presença de Mn nas amostras. Foi observado um pico termoluminescente (TL) em aproximadamente 140°C para os biominerais e em 180°C para os silicatos, cuja intensidade depende diretamente da dose. Para amostras expostas a diferentes tipos de radiações, o pico TL ocorre em temperaturas mais baixas. Para as curvas dose-resposta obtidas para esses materiais...

Geomorfologia do megaleque do Rio Paraguai, quaternário do pantanal mato-grossense, centro-oeste do Brasil

Silva, Aguinaldo
Fonte: Universidade Estadual Paulista (UNESP) Publicador: Universidade Estadual Paulista (UNESP)
Tipo: Tese de Doutorado Formato: 128 f. : il., tabs.
POR
Relevância na Pesquisa
45.98%
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Pós-graduação em Geociências e Meio Ambiente - IGCE; Fluindo de norte para sul, o Paraguai é o rio-tronco de um trato de sistemas deposicionais composto por inúmeros megaleques fluviais, que caracteriza a paisagem do Pantanal Mato-Grossense. Desde o Pleistoceno, o rio Paraguai vem construindo um megaleque fluvial na borda noroeste do Pantanal, cuja geomorfologia é objeto desta tese. Para desenvolvimento da tese, foram utilizadas imagens de satélites para compartimentação geomorfológica, trabalho de campo para validação dos dados e amostragem de sedimentos com vibrotestemunhador, datação por Luminescência Opticamente Estimulada (LOE) e dados hidrológicos obtidos no campo e de estações fluviométricas. Antes de sua entrada na planície do Pantanal, o rio Paraguai corre num cinturão de meandros com 5 km de largura, de idade holocênica de 1 a 3 ka AP, com padrão de canal meandrante a norte e retilíneo a sul. O cinturão está embutido num vale inciso em depósitos pleistocênicos, que revelaram idades de 10 a 160 ka AP. Datação de depósitos de antigos lobos deposicionais do megaleque do Paraguai...

Recovery of α-Al2O3 from Ionizing Radiation Dosimetric Sensors

Sanches,Edgar Aparecido; Costalonga,Ademir Geraldo Cavallari; Nascimento,Luana de Freitas; Mascarenhas,Yvone Maria; Mascarenhas,Yvonne Primerano
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/02/2015 EN
Relevância na Pesquisa
56.38%
Corundum, sapphire or α-Al2O3 is an important technological material in many optical and electronic applications such as solid-state lasers, optical windows and, more recently, as a radiation detector. Landauer (Glenwood, IL, USA) accumulated large number of archived and stored Luxel™ dosemeters composed of Al2O3:C, which were subjected to a recovery process. Due to the importance of this advanced crystalline material in OSL dosimetry, a recovery process was developed based on the dosemeters calcination and Al2O3:C has been reused in manufacturing of new dosemeters. This paper does not aim to optimize the recovery process, but provides an opportunity to study the involved process parameters and to recover this valuable crystalline material from used dosemeters. To the best of our knowledge no other recovery process involving this dosimetric material was described in scientific literature. Fourier Transform Infrared Spectrometry (FTIR), Thermogravimetry/Differential Thermoanalysis (TG/DTA), Differential Scanning Calorimetry (DSC), X-ray Diffraction (XRD), Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES), Optically Stimulated Luminescence (OSL) and Rietveld Refinement were used to characterize the recovered material and to check for the stability of its structural and dosimetric properties.

Denudation of the continental shelf between Britain and France at the glacial–interglacial timescale

Mellett, Claire L.; Hodgson, David M.; Plater, Andrew J.; Mauz, Barbara; Selby, Ian; Lang, Andreas
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em 01/12/2013 EN
Relevância na Pesquisa
45.98%
The erosional morphology preserved at the sea bed in the eastern English Channel dominantly records denudation of the continental shelf by fluvial processes over multiple glacial–interglacial sea-level cycles rather than by catastrophic flooding through the Straits of Dover during the mid-Quaternary. Here, through the integration of multibeam bathymetry and shallow sub-bottom 2D seismic reflection profiles calibrated with vibrocore records, the first stratigraphic model of erosion and deposition on the eastern English Channel continental shelf is presented. Published Optical Stimulated Luminescence (OSL) and 14C ages were used to chronometrically constrain the stratigraphy and allow correlation of the continental shelf record with major climatic/sea-level periods. Five major erosion surfaces overlain by discrete sediment packages have been identified. The continental shelf in the eastern English Channel preserves a record of processes operating from Marine Isotope Stage (MIS) 6 to MIS 1. Planar and channelised erosion surfaces were formed by fluvial incision during lowstands or relative sea-level fall. The depth and lateral extent of incision was partly conditioned by underlying geology (rock type and tectonic structure), climatic conditions and changes in water and sediment discharge coupled to ice sheet dynamics and the drainage configuration of major rivers in Northwest Europe. Evidence for major erosion during or prior to MIS 6 is preserved. Fluvial sediments of MIS 2 age were identified within the Northern Palaeovalley...

Age and origin of Terra Rossa soils in the Coonawarra area of South Australia

Mee, A.; Bestland, E.; Spooner, N.
Fonte: Elsevier Science BV Publicador: Elsevier Science BV
Tipo: Artigo de Revista Científica
Publicado em //2004 EN
Relevância na Pesquisa
56.15%
The famous Terra Rossa soil in the Coonawarra area, South Australia, is dominated by locally derived aeolian detritus, which probably accumulated over the last 120–130 ka. Four soil profiles and associated limestone and lunette deposits were investigated using the following methods: mass balance geochemistry of bulk soil samples (major and trace elements), quantitative X-ray diffraction (XRD) mineralogy, strontium isotopes (87/86), as well as grain-size analysis and cation exchange capacity. These data show that the Terra Rossa soil from the Coonawarra has a thick, clayey B-horizon which is geochemically homogeneous and dominated by smectite and kaolinite. Mass-balance calculations show unrealistic weathering scenarios when plotted using silicate residuum from the underlying limestone as parent. Realistic weathering scenarios are produced with fine-grained silicate material from local lunette deposits as parent. Strontium isotopes of silicate residuum from Gambier Limestone (0.78) contrast strongly with the clayey B-horizon (0.726). Strontium isotope ratios of silicate material from a local lunette (0.725) are similar to the B-horizon soil values. Strontium isotope ratios from regional geological units indicate that the strontium signature in the lunette and soil B-horizon is dominated by weathering products from the Palaeozoic Kanmantoo shales...

Radiation dosimetry using optically stimulated luminescence in fluoride phosphate optical fibres

Kalnins, C.; Ebendorff-Heidepriem, H.; Spooner, N.; Monro, T.
Fonte: Optical Society of America Publicador: Optical Society of America
Tipo: Artigo de Revista Científica
Publicado em //2012 EN
Relevância na Pesquisa
56.37%
Optically stimulated luminescence has been demonstrated within a fluoride phosphate glass optical fibre. These fibres have been used as the basis of a novel dosimeter architecture whereby the optical fibre acts as both the sensing and light guiding component. Fibres were fabricated from a commercially acquired glass and irradiated using a 90Sr/90Y source. Following optical stimulation with a 532 nm laser, optically stimulated luminescence of 483 ± 18 cnts/g/μJ was detected. In addition to OSL, scintillation of 6155 ± 78 cnts/s was also measured. A linear response between 0.16 - 2 Gy of irradiation was measured, after which the intensity was observed to plateau. These results indicate the potential suitability of fluoride phosphate optical fibres for radiation sensing applications.; Christopher A. G. Kalnins, Heike Ebendorff-Heidepriem, Nigel A. Spooner and Tanya M. Monro

Luminescent properties of fluoride phosphate glass for radiation dosimetry

Kalnins, C.; Spooner, N.; Ebendorff-Heidepriem, H.; Monro, T.
Fonte: Optical Society of America Publicador: Optical Society of America
Tipo: Artigo de Revista Científica
Publicado em //2013 EN
Relevância na Pesquisa
56.35%
Fluoride phosphate glass has the ability to detect ionizing radiation, and thus can be utilized in various forms for the purposes of dosimetry. To further understand the potential of this material, the luminescence properties have been studied using techniques such as thermoluminescence (TL)and optically stimulated luminescence (OSL). Short luminescent lifetimes and shallow electron trap depths were measured. At the main TL peak at 60 ºC, the activation energy was calculated to be 0.5 eV with a frequency factor of 1.9x106 s-1 and lifetime of 2.1x102 s at 293 K. Fast timing results yield an OSL rise-time of 12.2 μs. Results indicate the material studied is well suited for monitoring applications where the time between radiation exposure and OSL read-out is in the order of several minutes.; Christopher A. G. Kalnins, Nigel A. Spooner, Heike Ebendorff-Heidepriem, and Tanya M. Monro

Stratigraphy and optical dating of Pleistocene coastal deposits in the Port Campbell australite strewn field, SW Victoria

Williams, G.; Gostin, V.; Prescott, J.
Fonte: Taylor & Francis Publicador: Taylor & Francis
Tipo: Artigo de Revista Científica
Publicado em //2013 EN
Relevância na Pesquisa
66.44%
Alluvial-channel and overlying eolian deposits exposed in coastal cliffs in the Port Campbell australite (Australian tektite) strewn field, SW Victoria, were studied stratigraphically and dated by optically stimulated luminescence (OSL) for quartz sand grains to illuminate the occurrence of australites in this area. The channel deposits, termed the Dog Trap Bay Sand, yielded OSL ages from 420 ± 40 to 230 ± 15 ka for four sites, and the two eolian units OSL ages of 203 ± 16 and 93 ± 11 ka. The ages support field evidence that, contrary to the conclusions of a previous study by others, the channel deposits are stratigraphically distinct from and much younger than the Pliocene Hanson Plain Sand, which forms a regionally extensive system of marine strandlines to the north and NE of Port Campbell. The OSL ages show some preference for times of negative temperature anomalies marking the last four glacial periods of the Middle and Late Pleistocene as indicated by ice-core data from Antarctica. Eolian and at least some alluvial deposition evidently occurred when sea-level was low and rivers extended across the exposed continental shelf. Others have suggested that the Dog Trap Bay Sand contains rare australite fragments in situ. However...

Testing the TT-OSL single-aliquot protocol for quartz sediment dating.

Moffatt., Jillian Elizabeth
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2014
Relevância na Pesquisa
46.64%
Thermally-transferred optically stimulated luminescence (TT-OSL) is a form of optically stimulated luminescence that saturates at much higher doses than conventional OSL (Wang et al, 2006b). Luminescence sediment dating is a technique whereby the natural radiation dose given to a sample is measured. This is divided by the environmental radiation rate of the sample site to give the sample's age. As TT-OSL is able to measure higher doses than conventional OSL, it has been considered a candidate for long range luminescence sediment dating, beyond one million years. In this thesis, TT-OSL single-aliquot sediment dating protocols were tested on selected samples from the south-east of South Australia (SESA) stranded dune sequence, a sequence of ancient dunes ranging from 0 to 900 thousand years of age that have previously been independently dated using luminescence and non-luminescence dating methods. A young sample with a high natural dose from Baldina Creek, Burra, South Australia was also dated. Measurements of the thermal depletion of the TT-OSL signal were also made. It was found that, for the SESA samples, TT-OSL dating results do not agree with previous independent measurements above 200 ka. The results for the young Baldina Creek sample were within the expected range.; Thesis (M.Phil.) -- University of Adelaide...

Luminescence dating: an Australian perspective

Prescott, J.; Robertson, G.
Fonte: Taylor & Francis Ltd. Publicador: Taylor & Francis Ltd.
Tipo: Artigo de Revista Científica
Publicado em //2008 EN
Relevância na Pesquisa
56.22%
Applications of luminescence dating to Quaternary earth science are reviewed, the examples being from Australia. The methods of thermoluminescence (TL) and optical dating using optically stimulated luminescence (OSL) are briefly described, together with their limitations. Prominent results are: (i) the distribution of ages of Australian desert dunes shows peak activity at about the time of the last glacial maximum; (ii) the lake-full episodes of Lake Eyre are traced back to 140 ka; (iii) the ages of relict beach dunes in South Australia, when compared with independent geological ages based on δ18O records, show that luminescence dating can be used for ages to 500 ka and older; and (iv) the development of interior river systems has been traced. Among less common applications are: (i) the dating of Australia's youngest volcanoes at 5-4 ka (in these cases the luminescence signal was reset by heat); (ii) the determination of age vs depth of a deep-sea core; and (iv) the age of earthquakes (from the age of the infilling of fault scarps). The emphasis is on recent work and is illustrative rather than exhaustive, the object being to show the scope of luminescence dating. There are suggestions where further research might be directed.; J. R. Prescott and G. B. Robertson

TL, OSL and C-14 dating results of the sediments and bricks from mummified nuns' grave

Tudela, Diego R.G.; Tatumi, Sonia H.; Yee, Márcio; Brito, Silvio L.M.; Morais, José L.; Morais, Daisy de; Piedade, Silvia C.; Munita, Casimiro S.P.; Hazenfratz, Roberto
Fonte: Academia Brasileira de Ciências Publicador: Academia Brasileira de Ciências
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
66.24%
This paper presents the results of TL and OSL dating of soil and fragments of bricks from a grave, which was occupied by two mummified nuns, found at "Luz" Monastery, located in the state of São Paulo, Brazil. The TL and OSL ages were compared to C-14 dating ones obtained from bone collagens of the mummies. The majority of the ages is related to the eighteenth century. The gamma-ray spectroscopy was used to evaluate natural radioisotope concentrations in the samples, and by using these concentrations the annual dose rates, from 3.0 to 5.3 Gy/kyr, were obtained. Neutron activation analysis was performed and the radioisotope contents results are in agreement with those obtained by gamma-ray spectroscopy. The contents of U, Th and Ce elements were higher than those found in usual sediments.

TL, OSL and C-14 dating results of the sediments and bricks from mummified nuns' grave

Tudela,Diego R.G.; Tatumi,Sonia H.; Yee,Márcio; Brito,Silvio L.M.; Morais,José L.; Morais,Daisy de; Piedade,Silvia C.; Munita,Casimiro S.P.; Hazenfratz,Roberto
Fonte: Academia Brasileira de Ciências Publicador: Academia Brasileira de Ciências
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2012 EN
Relevância na Pesquisa
66.24%
This paper presents the results of TL and OSL dating of soil and fragments of bricks from a grave, which was occupied by two mummified nuns, found at "Luz" Monastery, located in the state of São Paulo, Brazil. The TL and OSL ages were compared to C-14 dating ones obtained from bone collagens of the mummies. The majority of the ages is related to the eighteenth century. The gamma-ray spectroscopy was used to evaluate natural radioisotope concentrations in the samples, and by using these concentrations the annual dose rates, from 3.0 to 5.3 Gy/kyr, were obtained. Neutron activation analysis was performed and the radioisotope contents results are in agreement with those obtained by gamma-ray spectroscopy. The contents of U, Th and Ce elements were higher than those found in usual sediments.

Dataci??n por fotoluminiscencia de algunas formaciones superficiales del Llano de Ovejas, Cordillera Central, Antioquia

Garc??a Londo??o, Carolina
Fonte: Universidad EAFIT; Maestr??a en Ciencias de la Tierra; Escuela de Ingenier??a. Departamento de Geolog??a Publicador: Universidad EAFIT; Maestr??a en Ciencias de la Tierra; Escuela de Ingenier??a. Departamento de Geolog??a
Tipo: masterThesis; Tesis de Maestr??a; acceptedVersion
SPA
Relevância na Pesquisa
35.98%
El m??todo de dataci??n por fotoluminiscencia permite datar el ??ltimo momento en que un material estuvo expuesto a la luz y tiene un rango de aplicaci??n que en condiciones ??ptimas va de 6 a 800 000 a??os, lo cual le confiere gran importancia para el estudio de formaciones del Cuaternario superior. Con este trabajo se inicia en Colombia la aplicaci??n del m??todo de dataci??n de fotoluminiscencia. Se pretende as?? contribuir con el desarrollo de nuevas t??cnicas de dataci??n aplicadas al Cuaternario, mediante la creaci??n del Laboratorio de Fotoluminiscencia de la Universidad EAFIT en el que se realiz?? la preparaci??n de muestras para su posterior dataci??n por el m??todo de fotoluminiscencia en el laboratorio AGE de la Universidad McMaster en Canad??.; xii, 123., 83 diapositivas.; Photoluminescence method allows the determination of the age of burial of materials with a range from 6 to 800 000 years under optimal conditions; the method is really important for the study of diverse quaternary formations. This work marks the first application of Photoluminescence (OSL- Optical Stimulated Luminescence) in Colombia. The objective is to contribute with the development of new dating techniques applied to Quaternary, and to create the Photoluminescence Laboratory at University EAFIT. At these laboratory samples were prepared and then shipped to Canada for dating at the AGE Laboratory of McMaster University in Canada.; Contenido parcial: Aspectos generales de la zona de estudio -- Estratigraf??a de las formaciones superficiales -- Principios del m??todo de dataci??n: fotoluminiscencia -- Metodolog??as para la toma...

Aeolian activity in northern Amazonia:optical dating of Late Pleistocene and Holocene palaeodunes

Teeuw, Richard; Rhodes, Edward
Fonte: Wiley-VCH Verlag GMBH Publicador: Wiley-VCH Verlag GMBH
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
56.17%
Palaeodunes were examined on the eastern margin of the Rio Branco-Rupununi savanna, northeast Amazonia. Optical dating suggests that the onset of aeolian activity was between 17 000 and 15 000 yr ago, just after the Last Glacial Maximum. Both the palaeodune axes and modern dominant wind directions have northeast to east-northeast directions, implying no significant shift in atmospheric circulation patterns over northeast Amazonia during the Late Pleistocene to Holocene. Major regional climate change events, such as the Younger Dryas, do not appear to have had any effect on the rates of aeolian deposition at the study site. Aeolian activity appears to have continued to the present day, showing a remarkably constant deposition rate of around 0.13 m kyr-1 initially, increasing smoothly to the present. Until more palaeodunes in northern Amazonia are dated, it is impossible to determine if this record of gradual aeolian deposition is a reliable regional palaeoclimate indicator, rather than being the result of local bioclimatic and geomorphological effects.

A study and characterization of the optically stimulated luminescence response of commercial SiO2 optical fiber to gamma radiation

Espinosa,G.
Fonte: Sociedad Mexicana de Física Publicador: Sociedad Mexicana de Física
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/02/2011 EN
Relevância na Pesquisa
66.71%
Everyday, is coming more common the use of optically stimulated luminescence (OSL) as radiation measurement methodology. Although the OSL response characteristics of several chemical compounds such as aluminum oxide, beryllium oxide, potassium chloride and fused quartz have already been studied, research into new OSL materials is of continuing scientific and commercial interest. The thermoluminescence (TL) response characteristics of commercially, Nokia® SiO2 optical fiber have previously been studied. The aim of this work is to characterize the OSL response of the SiO2 optical fiber to gamma radiation. The material preparation, pre-annealing, aliquot preparation, and OSL reading procedures are presented together with preliminary results of the investigation into the OSL response characteristics of the SiO2 optical fiber. The total luminescence was found to be a linear function of gamma radiation dose within the range investigated (15.6 to 93.8 mGy). The experimental method yielded high reproducibility and very low residual effect. The OSL fading curve suggests that the optical fiber can be used for OSL measurements for approximately 150 hours (around 6 days) after exposure to gamma radiation. Taking into account the limits imposed by this fading...