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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Nuclear Structure Study of Cd-110 through Internal Conversion Electrons

Jigmeddorj, Badamsambuu 24 August 2012 (has links)
For many years, Cd-110 has been considered the classic example of a vibrational nucleus within both the Collective Model and the Interacting Boson Model (IBM). As a vibrational nucleus, Cd-110 exhibits multi-phonon states. Recent studies on other cadmium isotopes have shown a breakdown of vibrational motion at the three-phonon level. The latest study on Cd-112 suggests that some of these excitations may instead result from intruder bands. The study through internal conversion electrons is important to investigate intruder structures in Cd-110, using the enhanced E0 transitions between intruder states and spherical phonon states as a signature. The nuclear structure of Cd-110 has been studied with In-110 beta decay through internal conversion electrons performed at TRIUMF using the 8pi spectrometer. The level scheme of Cd-110 through internal conversion electron transitions was constructed using the electron-gamma coincidence matrix. The sub-shell ratios and multipolarities are determined and compared with the evaluated data set. The absolute internal conversion coefficients for some mixed transitions were determined using an internal calibration efficiency for Si(Li) detector and relative efficiency for HPGe detector. The 396 keV and 708 keV E0 transitions have been observed between intruder and spherical phonon states. The E0 transition strength of 0.115(71) was determined for 708.21 keV line.
2

Modificação das posturas dos simuladores antropomórficos voxel de referência Adult Male (AM) e Adult Female (AF) para cálculo de coeficientes de conversão de dose / Posture modification of the reference anthropomorphic voxel phantom Adult Male (AM) and Adult Female (AF) for dose conversion coefficients calculation

Galeano, Diego Castanon 11 October 2016 (has links)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Establish limits to the exposure of the population to various ionizing radiation sources is crucial to prevent occupationally exposed individuals and the public, to their deleterious effects. In computational ambit, it is necessary that different exposure scenarios are simulated in order to obtain the dose coefficients (CCs), which relate physical dosimetric quantities - as absorbed dose, Fluency or Kerma Air - with limiting quantities - as equivalent and / or effective dose. Under certain exposure conditions, the individual's posture is not always the same, and the scenario shall be described as realistic as possible. In this work, the AM (Adult Male) and AF (Adult Female) anthropomorphic reference phantom of ICRP publication n° 110 had their postures modified from supine posture (standing) to sitting posture. The change of posture was performed through of a subroutine written in the Visual Monte Carlo code (VMC) to rotate the thigh region of the phantom and position it between the region of the leg and torso. The ScionImage software was used to reconstruct and smooth the knee and hip contours in a sitting posture phantom, and for 3D visualization of phantom was used VolView software. After this step the MCNPX radiation transport code was used for the calculation of fluence-to-dose conversion coefficients (CCs) to six irradiation geometries: AP, PA, LLAT, RLAT, ROT and ISO, recommended by ICRP. The results were compared between the phantoms in standing and sitting postures, for both sexes, in order to assess differences in scattering and absorption of radiation in different postures. The results show significant differences of up to 100% in the equivalent dose conversion coefficients of organs in the pelvic region, 79 % in organs with distribution in the whole body (such as skin, muscle, lymph nodes, bone marrow and trabecular bone) and a difference of 27% to effective dose conversion coefficients. Moreover in order to conduct a comparative study between two types of simulators, was estimated CCs equivalent and effective dose of adult male hybrid simulators, UFHADM, and female, UFHADF, in a sitting posture, and compared to the AM and AF simulators, also in the sitting posture, where it was observed significant difference in energies below 0.05 MeV. This study demonstrated the feasibility of using anthropomorphic phantoms in the sitting posture to represent more realistic postures and can be used in studies in medical and occupational dosimetry. This study demonstrated the feasibility of using anthropomorphic simulators reference in the seated position to represent more realistic positions can thus be used in studies in medical and occupational dosimetry as well as the importance of developing as realistic simulators as possible to dose estimation as faithful as possible in different irradiation scenarios. / Estabelecer limites à exposição da população a diversas fontes de radiação ionizante é de fundamental importância para prevenir indivíduos, ocupacionalmente expostos e do público, dos seus efeitos deletérios. Em âmbito computacional, é necessário que diferentes cenários de exposição sejam simulados, visando à obtenção dos coeficientes de dose (CCs), que associam grandezas dosimétricas físicas – como dose absorvida, fluência ou kerma no ar – com grandezas limitantes – como equivalente e/ou dose efetiva. Em certas condições de exposição a posição do indivíduo nem sempre é a mesma, e o cenário deve ser descrito da forma mais realística possível. Neste trabalho, os simuladores antropomórficos de referência da publicação nº 110 da ICRP, AM (Adult Male) e AF (Adult Female), tiveram suas posturas modificadas da postura supinada (em pé) para a postura sentada. A mudança de postura foi realizada por meio de uma subrotina escrita no software Visual Monte Carlo (VMC) para rotacionar a região da coxa dos simuladores e posicioná-la entre a região da perna e do tronco. O software ScionImage foi utilizado para reconstruir e suavizar os contornos no joelho e quadril dos simuladores na postura sentada, e com ferramenta auxiliar para visualização 3D dos simuladores foi utilizado o software VolView. Após essa etapa foi utilizado o código de transporte de radiação MCNPX para o cálculo dos coeficientes de conversão (CCs) de dose equivalente e efetiva por fluência de partículas, calculados para seis geometrias de irradiação AP, PA, LLAT, RLAT, ROT e ISO, recomendadas pela ICRP. Os resultados foram comparados entre os simuladores em pé e sentado, para ambos os gêneros, com o objetivo de avaliar as diferenças de espalhamento e absorção da radiação para as diferentes posturas. Os resultados dos CCs mostram diferenças significativas, de até 100 % para dose equivalente dos órgãos situados a região pélvica e 79 % em órgãos com distribuição em todo o corpo como, por exemplo, pele, músculo, nódulos linfáticos medula óssea e trabécula óssea, e uma diferença de 14 % para dose efetiva. Ademais, a fim de realizar um estudo comparativo entre dois tipos de simuladores, foi estimado os CCs de dose equivalente e efetiva dos simuladores híbridos adulto masculino, UFHADM, e feminino, UFHADF, na postura sentada, e comparado com os simuladores AM e AF, também na postura sentada, onde foi observado diferença significativa em energias abaixo de 0,05 MeV. Este estudo demonstrou a viabilidade do uso dos simuladores antropomórficos de referência na postura sentada para representar posturas mais realísticas podendo assim, ser utilizado em estudos na dosimetria médica e ocupacional, bem como a importância de desenvolver simuladores tão realista quanto possíveis para estimativa de dose tão fiéis quanto possíveis em diversos cenários de irradiação.

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