Made available in DSpace on 2014-10-09T12:26:04Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:06:49Z (GMT). No. of bitstreams: 1 12891.pdf: 1261412 bytes, checksum: 22d81b21c8b5536ef9c962a801aed517 (MD5) / Dissertacao (Mestrado) / IEA/D / Instituto de Quimica, Universidade de Sao Paulo - IQ/USP

Made available in DSpace on 2014-10-09T12:54:44Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:09:28Z (GMT). No. of bitstreams: 0 / Neste trabalho foram determinados os elementos As, Br, Co, Cr, Cs, Fe, K, Na, Rb, Se e Zn presentes em cogumelos comestíveis adquiridos em grandes centros de compra (supermercados), mercados municipais da cidade de São Paulo e diretamente de produtores da região de Mogi das Cruzes, Suzano, Juquitiba e Mirandópolis. A técnica analítica empregada para a determinação dos elementos nos cogumelos comestíveis foi a Análise por Ativação com Nêutrons Instrumental (INAA). Foram adquiridas espécies dos gêneros Agaricus, Lentinus e Pleurotus no período de novembro de 2006 a março de 2007. Cerca de 150 a 200 mg das amostras de cogumelo liofilizado foram irradiadas em fluxo de nêutrons térmicos de 1012cm-2s-1 por 8 horas no reator nuclear de pesquisa IEA-R1 do IPEN/CNEN/SP. Para a validação da metodologia com relação à exatidão e à precisão foram analisados quatro materiais de referência: INCT-MPH-2 Mixed Polish Herbs e INCT-TL-1 Tea Leaves, NIST SRM 1577b Bovine Liver e Mushroom da IAEA. Foi verificada uma variação nas concentrações dos elementos determinados entre os diferentes gêneros. Em algumas amostras apresentaram o elemento arsênio, em baixas concentrações, possivelmente de uma contaminação no cultivo pelo uso de pesticidas nos substratos de onde os cogumelos retiram seus nutrientes. Os resultados mostram que as amostras das espécies de cogumelos analisadas podem ser consideradas como boa fonte nutricional, principalmente devido aos baixos teores de Na, sendo também uma boa fonte de K, Fe e Zn. / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energéticas e Nucleares - IPEN/CNEN-SP

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Made available in DSpace on 2014-10-09T12:26:12Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:09:47Z (GMT). No. of bitstreams: 0 / Os estudos sobre as análises de cabelos humanos têm sido assunto de contínuo interesse por se tratar de uma importante ferramenta para a avaliação de níveis de elementos traço no corpo humano. O interesse por este tecido é para o uso na monitoração de exposição ambiental ou ocupacional, para identificação da intoxicação e/ou envenenamento por metais tóxicos, na avaliação do estado nutricional, na diagnose e prevenção de doenças e nas ciências forenses. Há inúmeras vantagens na análise de cabelos quando comparados com as de outros tecidos ou fluidos biológicos, tais como sangue, urina, saliva e órgãos. Entretanto há controvérsias sobre o uso das análises de cabelos em razão da dificuldade em estabelecer os valores confiáveis de referência para as suas concentrações de elementos traço. O objetivo deste estudo foi avaliar os fatores que afetam nas concentrações de elementos em cabelos humanos e determinar os elementos em cabelos de uma população de indivíduos considerados saudáveis e residentes na área metropolitana de São Paulo, utilizando o método de análise por ativação com nêutrons (NAA). As amostras de cabelo coletadas da região occipital da cabeça foram cortadas em pequenos fragmentos, lavadas e secas para análise. As alíquotas de amostras de cabelo, juntamente com padrões sintéticos de elementos foram irradiados por 16 h sob fluxo de nêutrons térmicos de cerca de 5 x 1012 n cm-2 s-1 do reator nuclear IEA-R1 para a determinação de As, Br, Ca, Co. Cr, Cs, Cu, Fe, K, La, Na, Sb, Sc, Se e Zn. As radiações gama das amostras e dos padrões irradiados foram medidas em um espectrômetro de raios gama acoplado a um detector de Ge hiperpuro. Para avaliar a qualidade dos resultados com relação à exatidão e precisão foram analisados os materiais de referência certificados IAEA- 85 Human Hair e INCT-TL-1 Tea Leaves cujos resultados obtidos apresentaram, para a maioria dos elementos, boa concordância com os valores dos certificados (porcentagens de erros relativos inferiores a 10%) e boa precisão (coeficientes de variação inferiores a 13,6% ). As análises de uma amostra de cabelo em réplicas indicaram uma boa reprodutibilidade dos resultados, indicando a homogeneidade da amostra preparada. Os resultados das análises de cabelo com e sem tintura indicaram que a tintura afeta nos teores de elementos no cabelo em virtude da adsorção ou dessorção do elemento. As análises de cabelos de diferentes regiões da cabeça indicaram diferenças significativas para os elementos Fe, Sc, Se e Cr. Análises de cabelos de indivíduos residentes na área metropolitana de São Paulo indicaram que as concentrações de elementos nos cabelos dependem da idade, sexo e cor natural dos cabelos. Os resultados das análises de cabelos desta população mostraram que as médias das concentrações de elementos obtidas estão dentro da faixa de valores da literatura. / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Made available in DSpace on 2014-10-09T12:26:12Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:10:39Z (GMT). No. of bitstreams: 0 / No presente estudo a técnica de analise por ativação com nêutrons foi utilizada para a determinação simultânea da concentração de elementos, de relevância em clínica, em sangue total de Hamster Dourado. O limite de normalidade obtido para Br, Ca Cl, Mg, Na e S considerando 2 (Dois Desvios Padrão), foi de 0,011 - 0,047 gL-1 (Br); 0,11 - 0,35 gL-1 (Ca); 2,11 - 3,75 gL-1 (Cl); 1,35 - 2,79 gL-1 (K), 0,026 0,090 gL-1 (Mg), 1,03 2,51 gL-1 (Na) e 0,97 2,01 gL-1 (S) . O conhecimento desses limites viabiliza o uso de sangue total em investigações clínicas deste modelo animal. A comparação com as estimativas de normalidade em sangue total em seres humanos (Hamster & humano) permitiu verificar as similaridades ou diferenças fisiológicas, dados importantes em experimentos utilizando este modelo animal. / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

<p>Aluminum is present throughout the environment and in many industrial processes and consumer goods. While very useful in everyday lives, it has no inherent biological functions in humans. High quantities in the human body can be toxic, resulting a range of skeletal, neurological, and hematopoietic effects. A system has been developed to analyze aluminum using the neutron activation analysis (NAA) technique in vivo. NAA was performed with a transportable neutron generator as a neutron source and a high purity germanium (HPGe) detector for spectroscopy. The neutron generator and HPGe detector were completely modelled in MCNP6. Measurements were carried out to evaluate the accuracy of the MCNP6 simulations and to determine the detection capabilities of the system for aluminum. Simulations were also conducted to determine the acceptability of radiation dose to subjects undergoing analysis. The detection limit for the system was evaluated using skeletal bone as a long-term aluminum biomarker. The detection limit was determined to be 3.41 x 10¹ μg of Al per g of dry bone for an irradiation time of six minutes. This detection level is below a point at which physiological effects have been observed in humans. A lower detection level was demonstrated to be possible with a longer irradiation time. The radiation absorbed dose was determined to be 7.30 mGy for an irradiation of six minutes. The system can therefore be utilized as a potential screening and monitoring tool for high skeletal burdens of aluminum that may lead to physiological effects.</p> <p>The simulation and calculation techniques developed herein were applied to a set of human subject data that were acquired for a purpose other than evaluating aluminum. The human subject data included both bone Al from NAA and fingernail Al from mass spectrometry measurements. No significant aluminum signals were observed when assessing the in vivo NAA spectra data. Through simulation and calculation, it was demonstrated that the NAA experimental parameters resulted in an elevated detection limit for aluminum that is above Al skeletal loads observed in healthy individuals. The elevated detection limit prevented the in vivo detection of aluminum in a healthy population, thus confirming the NAA results. </p>

<p>Excess sodium (Na) intake is directly related to hypertension and an increased risk of developing many chronic diseases, but there is currently no method to directly quantify Na retained in the body. Because of this, the locations of Na storage and its exchange mechanisms are not well known. This information is critical for understanding the impact of increased Na intake in modern diets. In order to non-invasively quantify Na in bone and soft tissue, a compact deuterium-deuterium (DD) neutron generator-based <i>in vivo</i> neutron activation analysis (IVNAA) system was developed. MCNP was used to design a custom irradiation assembly to maximize Na activation in hand bone while minimizing dose. In order to test the system, live pigs were used. Two 100% efficient high purity germanium (HPGe) detectors collected Na-24 counts over 24 hours post irradiation. From the pig studies, a two-compartment model of exchange was developed to quantify Na in bone and in soft tissue. The right legs of four live pigs, two on a low Na diet and two on a high Na diet, both for 14 days, were irradiated inside the customized irradiation cave for 10 minutes (45 mSv dose to the leg) and then measured with the HPGe detectors. The spectra were analyzed to obtain the net Na counts at different time points. Analysis shows exponential decrease of Na in the leg during the first one hour of measurement, while the change was minimal at the second hour, and the counts were stabilized at the second and third 2 hour measurements, taken 7 and 21 hours post irradiation. Bone Na and soft tissue Na concentrations were calculated using calibration lines created with bone and soft tissue equivalent Na phantoms as well as the parameters obtained from the two-compartment model. The results show that the difference in bone and soft tissue Na between the pigs on high vs low Na diets was significant. With these results, we conclude that DD neutron generator-based IVNAA can be used to accurately quantify Na in bone and soft tissue <i>in vivo </i>and the system is a potential valuable tool for nutrition studies.</p>

<p> Though Neutron Activation Analysis is one of the most sensitive multielement analysis methods, Compton interference in complex sample matrices usually presents a problem when choosing irradiation and decay times for analysis. While various scientists have attempted to solve the problem, the approaches taken to date have the drawbacks of either requiring standard spectra of the sample components or not giving the optimum times automatically and simultaneously. The purpose of this thesis was to find a method to automatically and simultaneously obtain the optimum times for Instrumental Neutron Activation Analysis using the Modified Simplex Method to evaluate the best figure of merit calculated from an advance predicted spectrum of the sample.</p> / Thesis / Master of Science (MSc)

<p> This work was the first study at the beam port # 4 at the McMaster Nuclear Reactor, involving prompt gamma in vivo neutron activation analysis. The project consisted of experimental and computational parts. The computational part was done using MCNP program, which simulates the neutron and photon transport in the medium. The first thing assessed was the energy dependent neutron fluence rate in the collimated neutron beam, at the site. This was done in order to figure out the complete source (sdef) card for further MCNP calculations. This was combined experimental and computational work. For the experimental part, various activation foils were used and computational part was done by using MCNP programming.</p> <p> The second part of the project involved experimental prompt gamma in vivo activation analysis using 7 different phantoms, ranging from 30 mL to 2 L. Three different elements were observed. The prompt gamma in vivo detection of cadmium was the preliminary calibration study and the experiments were done with all seven phantoms. The calibration lines and MDL were assessed for all phantoms, with concentration ranging from 0 to 50 ppm. The prompt gamma in vivo detection of boron and mercury was done using 30 mL phantoms. Calibration lines and MDL for both elements were assessed as well.</p> <p> MCNP experimental simulations for 30 mL water phantoms were done and they were in close agreement with the experimental results. Furthermore, the MCNP gamma and neutron dose survey in the cave was done.</p> <p> The results obtained showed that there are numerous open possibilities for improvement in terms of in vivo prompt gamma analysis at the site. It predominantly includes the improvements in prompt gamma detection techniques and MCNP source definition. Furthermore, it was found that MCNP programming is the ideal tool for assessment and control of the experimental results in this case. It means that in the future research, the MCNP modeling will be the essential part of the in vivo prompt gamma activation analysis at this beam port.</p> / Thesis / Master of Science (MSc)

In this thesis, a theoretical study of certain properties of the diffusion coefficient matrix in a multicomponent system has been carried out. The ratio of the off-diagonal diffusion coefficient to the on-diagonal diffusion coefficient in a dilute ternary substitutional system has been evaluated theoretically. The effect of the second solute gradient on the diffusivity of the first one in a ternary substitutional solid solution has been experimentally determined using the neutron activation analysis technique. / Thesis / Master of Engineering (MEngr)