The developments of nuclear medicine lead to an increasing demand for the production of radioisotopes with suitable nuclear and chemical properties. Furthermore, from the literature it is evident that the production of radioisotopes using charged-particle accelerators instead of nuclear reactors is gaining increasing popularity. The main advantages of producing medical isotopes with accelerators are carrier free radionuclides of short lived isotopes, improved handling, reduction of the radioactive waste, and lower cost of isotope fabrication. Proton-rich isotopes are the result of nuclear interactions between enriched stable isotopes and energetic protons. An interesting observation is that during the production of proton-rich isotopes, fast and intermediately fast neutrons from nuclear reactions such as (p,xn) are also produced as a by-product in the nuclear reactions. This observation suggests that it is perhaps possible to use these neutrons to activate secondary targets for the production of neutron-rich isotopes. The study of secondary radioisotope production with fast neutrons from (p,xn) reactions using a particle accelerator is the main goal of the research in this thesis.

A análise por ativação neutrônica instrumental (INAA) é uma opção para o estudo da composição de alimentos, permitindo determinar simultaneamente diversos elementos. Todavia, a deposição incompleta da energia da radiação gama no detector, devido à interação por espalhamento Compton, dificulta as determinações. O acúmulo de contagens na linha de base do espectro torna-se um problema quando existem na amostra radionuclídeos com emissões gama em energias mais altas do que a de interesse. Nesses casos, os supressores Compton podem aumentar a sensibilidade analítica. Aqui, avalia-se o uso de supressão Compton para o estudo de produtos agrícolas destinados à alimentação humana. Todas as medições foram realizadas com um detector de germânio hiperpuro com 55 % de eficiência relativa (1332 keV, 60Co), circundado por detectores de iodeto de sódio (annulus e plug). Espectros com supressão foram adquiridos a partir da detecção em anti-coincidência. Foram também armazenados os espectros sem supressão. Inicialmente, testou-se a capacidade do equipamento em reduzir a região Compton, empregando fontes de 137Cs. Medindo-se na região entre 358 e 382 keV, o melhor fator de supressão foi 5,97, sendo observada variação no valor de acordo com a região Compton escolhida para a medição. Reduções foram notadas no fator de supressão com o aumento da taxa de contagem e da distância fonte-detector. Em verificações realizadas durante 20 semanas, o sistema supressor mostrou-se estável. Para avaliar o uso de supressão Compton na análise de amostras, foram tomados diversos tipos e marcas comerciais de arroz, batata, feijão, ervilha, grão-de-bico e lentilha. Após secagem e moagem, as amostras foram irradiadas em fluxo de nêutrons térmicos de 1x10E13 cm-2 s-1 por 8 horas, no reator IEA-R1m do IPEN/CNEN (Instituto de Pesquisas Energéticas e Nucleares). A radioatividade foi medida em quatro oportunidades, em aproximadamente 3, 7, 15 e 40 dias após a irradiação. A análise foi conduzida pelo método k0, utilizando o programa Quantu. Quinze elementos foram estudados, entretanto Cd e Hg apresentaram-se abaixo dos limites de detecção, o que também occoreu para As, Cr, La e Se em várias amostras. Foram notados alguns comportamentos próprios de cada tipo de produto analisado. Arroz integral, parboilizado e polido, por exemplo, apresentaram diferentes concentrações de K, Rb e Zn. Dentre os elementos com maior potencial tóxico, a presença de um valor médio de 0,3 mg kg-1 de As em arroz foi a única observação. Houve influência de Br, K e Na sobre os limites de detecção para os elementos medidos entre 3 e 8 dias após a irradiação. A razão entre os limites de detecção sem e com supressão mostrou que a determinação de Br, Co, La, Na, Sc e Se não foi favorecida pelo uso do supressor. Para As, Ca, Cd, Cr, Fe, Hg, K, Rb e Zn, observou-se ganho de sensibilidade fortemente dependente da composição do material e das condições experimentais. Os resultados demonstraram que o desempenho do supressor Compton em INAA deve ser individualmente testado para cada tipo de amostra. / Instrumental neutron activation analysis (INAA) is a good option for studying chemical composition of food, allowing the simultaneous determination of several elements. However, the incomplete deposition of gamma-ray energies in the detector crystal due to Compton scatter can elevate the spectrum baseline making difficult the determination of some elements. The problem is particularly important for samples having high activities of radionuclides emitting gamma-rays with energies higher than those to be measured. For such cases, the use of a Compton suppression system can improve the detection limits. Here, the application of a suppression system for the analysis of foodstuff is evaluated. Measurements were carried out with a hyperpure germanium detector with 55 % relative efficiency for the photopeak 1332 keV of 60Co, working in anti-coincidence with two sodium iodine guard detectors (annulus and plug). Suppressed and unsuppressed spectra were simultaneously acquired. Initially, the overall system performance on the reduction of the Compton region was tested using 137Cs. Measuring between 358 and 382 keV, the higher suppression factor was 5.97, being observed a large variation according to the energy region selected for the determination. Reductions were noticed for the suppression factor resulting from increases on counting rate and source-detector distance. The suppression system showed to be stable during twenty weeks of periodic verifications. To evaluate the system performance on real sample analysis, several types and commercial brands of rice, potatoes, beans, peas, chickpeas and lentil were taken. After drying and grinding, samples were irradiated at a thermal neutron flux of 1x10E13 cm-2 s-1 for 8 hours, in the nuclear research reactor IEA-R1m from IPEN/CNEN (Instituto de Pesquisas Energéticas e Nucleares). Each sample was measured after decay periods of about 3, 7, 15 and 40 days. Analysis was conducted by the k0 method using the software package Quantu. Fifteen elements were assessed, however Cd and Hg were below detection limits, as well as As, Cr, La e Se for several samples. The content of some elements were noticed to vary according to the product analyzed or its particular type. Different results, for instance, were obtained for K, Rb and Zn in integral, parboiled and polish rice. Among the elements with potentially high toxicity for humans, the only observation was a mean As content of 0.3 mg kg-1 in rice. There was a significant influence of Br, K and Na on the detection limits for elements measured from 3 to 8 days after the irradiation. The ratio between the detection limits calculated for unsuppressed and suppressed spectra showed that the determination of Br, Co, La, Na, Sc and Se was not improved by using the Compton suppression system. For As, Ca, Cd, Cr, Fe, Hg, K, Rb and Zn, an enhancement in the analytical sensitivity was noted, which was strongly dependent on sample composition and experimental conditions. The results demonstrated that the suppression system performance for INAA should be individually evaluated for each type of matrix to be analyzed.

O estudo do efeito da colimação nos detectores de radiação sobre a qualidade de imagem do tomógrafo industrial de terceira geração desenvolvido no IPEN/CNEN-SP é descrito neste trabalho. Três conjuntos de colimadores de chumbo foram projetados e confeccionados, sendo um com janelas retangulares de 2 x 5 x 50 mm e outro com 4 x 10 x 50 mm (largura x comprimento x profundidade) e um terceiro com orifício circular de 5 mm de diâmetro x 40 mm de profundidade. Os colimadores foram projetados para poderem ser facilmente substituídos entre si nos detectores de radiação. Paralelamente, foram confeccionados e utilizadas a eletrônica associada, constituída de analisadores de sinais tipo multicanal de 8 bits contendo a unidade de alta tensão e o amplificador. Dentre as vantagens deste sistema destaca-se a sua capacidade de análise multicanal rápida e possuir uma eletrônica mais simples. Valores de resolução energética comparável com a da literatura foram encontrados utilizando a eletrônica desenvolvida acoplada ao detector de radiação de NaI(Tl). Os efeitos dos colimadores foram avaliados pelas medidas tomográficas em um fantom de polimetilmetacrilato contendo componentes multifásicos estáticos (ferro, alumínio e ar). Fontes de radiação com energias de das fontes de 75Se (97 keV, 121 keV, 136 keV, 265 keV, 279 keV e 400 keV), de 137Cs (662 keV) e de 192Ir (317 keV, 468 keV e 602 keV) observou-se que a melhor imagem do fantom foi obtida com os colimadores de janelas retangulares (fendas) de 2 x 5 x 50 mm. Na avaliação dinâmica da formação de bolhas em coluna simuladora de processos industriais, a melhor imagem foi obtida com a fonte de 192Ir. / The study of the effect of collimation in radiation detectors on the image quality of the third-generation industrial CT scanner developed at IPEN / CNEN-SP is described in this work. Three sets of lead collimators were designed and manufactured, one with rectangular windows of 2 x 5 x 50 mm and the other with 4 x 10 x 50 mm (width x length x deep) and a third circular hole of 5 mm diameter x 40 mm deep. The collimators were designed to be easily interchanged in radiation detectors. In parallel, were prepared and used the associated electronics, consisting of multi-channel signal analyzers type of 8 bits containing the high voltage unit and the amplifier. Among the advantages of this system stands out for its ability to fast multichannel analysis and possess a simpler electronics. Values in energy resolution comparable with the literature were found using the developed electronics coupled to the radiation detector of NaI (Tl). The effects of collimators were evaluated by tomographic measurements in a multiphase fantom polymethyl methacrylate containing static components (iron, aluminum and air). Radiation sources with energies of the sources of 75Se (97 keV, 121 keV, 136 keV, 265 keV, 279 keV and 400 keV), 137Cs (662 keV) and 192Ir (317 keV, 468 keV and 602 keV) observed that the best image was obtained fantom collimators with rectangular windows (slits) 2 x 5 x 50 mm. In the dynamic evaluation of formation of bubbles column in a simulated industrial processes the best image at was obtained with the 192Ir source.

Thesis (MTech (Environmental Management))--Cape Peninsula University of Technology, 2018. / The iThemba Laboratory for Accelerator Based Sciences (iThemba LABS or iTL), a facility governed by the National Research Foundation (NRF) based in Cape Town has embarked on a project called the South African Isotope Facility (SAIF). Part of the SAIF will be a project called the Low Energy Radioactive Ion Beam (LERIB) for the production of radioactive beams with the Separated Sector Cyclotron (SSC). The LERIB project is anticipated to generate significant prompt sources of ionising radiation such as neutrons displaced by protons during bombardment of targets. At present, the facility has 3 - 5 m thick concrete walls designed to shield against 200 MeV neutrons. The floor thickness varies from each vault according to the behaviour and characteristics of the produced radiation. The LERIB facility concrete floor is envisioned to be 1 m thick. Insufficient floor shielding might expose the sub-surface strata below the floor with ionising radiation. Some matter in the exposed strata might undergo activation and consequently produce undesirable radioactive isotopes. Exposure to radioactive isotopes can pose potential risks to the general public and the receiving environment. In the sub-surface, the activated isotopes can spread through the soil and groundwater bodies. Groundwater being mobile in nature might act as conduit for activated isotopes to migrate in the subsurface. The half-lives of the formed radionuclides were used to estimate the distance the radionuclides can migrate in the sub-surface before decay. The X-Ray Fluorescence (XRF) and Inductive Coupled Plasma - Mass Spectrometry (ICP-MS) were used to quantify the mass fraction of elements from soil and groundwater samples. The Inductive Coupled Plasma - Optical Emission Spectrometry (ICP-OES) was used to measure dissolved metals of major and minor oxides in groundwater samples. These scientific techniques were applied in order to measure mass fractions of elements present in the sub-surface anticipated to be exposed with neutron radiation. Results revealed that the sub-surface in the study site constitutes Si, Al, Na and Fe in abundance. This suggests that, these elements might have a high probability to undergo activation compared to those occurring at lower concentrations, such as minor and trace elements. However the neutron capture cross-section for these elements varies and hence some elements such as Si and Al were not activated. To investigate elements measured from the ICP-MS, ICP-OES and XRF which might undergo activation, soil and water samples were irradiated for an hour with neutrons from a Beryllium target from a range of 0 – 66 MeV energy. The results revealed that activating the sub-surface with neutron radiation will result to the formation of short and long-lived unstable isotopes. However, isotopes with long half-lives such as 22Na, 52Mn, 54Mn and 46Sc only occurred in soil samples and none measured from the water samples except a short-lived isotope 24Na. These results agrees with the reviewed literature that, water being a product of two hydrogens and one oxygen, with 1H from H2O considered to be a good neutron moderator should have absorbed the neutrons so as to reduce neutron capture cross-sections.

O estudo do efeito da colimação nos detectores de radiação sobre a qualidade de imagem do tomógrafo industrial de terceira geração desenvolvido no IPEN/CNEN-SP é descrito neste trabalho. Três conjuntos de colimadores de chumbo foram projetados e confeccionados, sendo um com janelas retangulares de 2 x 5 x 50 mm e outro com 4 x 10 x 50 mm (largura x comprimento x profundidade) e um terceiro com orifício circular de 5 mm de diâmetro x 40 mm de profundidade. Os colimadores foram projetados para poderem ser facilmente substituídos entre si nos detectores de radiação. Paralelamente, foram confeccionados e utilizadas a eletrônica associada, constituída de analisadores de sinais tipo multicanal de 8 bits contendo a unidade de alta tensão e o amplificador. Dentre as vantagens deste sistema destaca-se a sua capacidade de análise multicanal rápida e possuir uma eletrônica mais simples. Valores de resolução energética comparável com a da literatura foram encontrados utilizando a eletrônica desenvolvida acoplada ao detector de radiação de NaI(Tl). Os efeitos dos colimadores foram avaliados pelas medidas tomográficas em um fantom de polimetilmetacrilato contendo componentes multifásicos estáticos (ferro, alumínio e ar). Fontes de radiação com energias de das fontes de 75Se (97 keV, 121 keV, 136 keV, 265 keV, 279 keV e 400 keV), de 137Cs (662 keV) e de 192Ir (317 keV, 468 keV e 602 keV) observou-se que a melhor imagem do fantom foi obtida com os colimadores de janelas retangulares (fendas) de 2 x 5 x 50 mm. Na avaliação dinâmica da formação de bolhas em coluna simuladora de processos industriais, a melhor imagem foi obtida com a fonte de 192Ir. / The study of the effect of collimation in radiation detectors on the image quality of the third-generation industrial CT scanner developed at IPEN / CNEN-SP is described in this work. Three sets of lead collimators were designed and manufactured, one with rectangular windows of 2 x 5 x 50 mm and the other with 4 x 10 x 50 mm (width x length x deep) and a third circular hole of 5 mm diameter x 40 mm deep. The collimators were designed to be easily interchanged in radiation detectors. In parallel, were prepared and used the associated electronics, consisting of multi-channel signal analyzers type of 8 bits containing the high voltage unit and the amplifier. Among the advantages of this system stands out for its ability to fast multichannel analysis and possess a simpler electronics. Values in energy resolution comparable with the literature were found using the developed electronics coupled to the radiation detector of NaI (Tl). The effects of collimators were evaluated by tomographic measurements in a multiphase fantom polymethyl methacrylate containing static components (iron, aluminum and air). Radiation sources with energies of the sources of 75Se (97 keV, 121 keV, 136 keV, 265 keV, 279 keV and 400 keV), 137Cs (662 keV) and 192Ir (317 keV, 468 keV and 602 keV) observed that the best image was obtained fantom collimators with rectangular windows (slits) 2 x 5 x 50 mm. In the dynamic evaluation of formation of bubbles column in a simulated industrial processes the best image at was obtained with the 192Ir source.

INTRODUÇÃO: Braquiterapia de alta taxa de dose (BATD) para o câncer de próstata pode ser uma boa opção para escalonamento de dose, como um reforço de dose, associada à radioterapia externa, principalmente se não há disponibilidade de radioterapia tridimensional conformada ou tecnologia mais avançada. OBJETIVOS: Neste trabalho, analisaram-se os resultados e as toxicidades de um reforço de dose com BATD prévio à radioterapia externa convencional ou tridimensional conformada em pacientes portadores de câncer localizado da próstata. Fatores prognósticos relacionados à sobrevida livre de doença, além de toxicidade do tratamento também foram estudados. MÉTODOS: Estudo retrospectivo de 403 pacientes com adenocarcinoma localizado da próstata tratados entre dezembro de 2000 e março de 2004, que receberam 3 esquemas de fracionamento distintos de BATD de acordo com o seu grupo de risco: três frações de 5,5 a 6 Gy, 6 a 6,5 Gy ou 6,5 a 7 Gy, para baixo, médio ou alto risco, respectivamente, em um único implante, no decorrer de 24h de internação. A radioterapia externa convencional ou conformada compreendeu dose de 45 Gy na próstata e vesículas seminais. Foram realizadas análises uni e multivariada para avaliação dos fatores prognósticos relacionados à sobrevida livre de falha bioquímica e toxicidades. RESULTADOS: A idade mediana dos pacientes foi de 68 anos, com PSA médio de 9g/ml, peso prostático médio de 35 cc. Grau histológico de Gleason igual a 6 ocorreu em 43% dos casos, estádio menor do que T2c em 97%, presença de nódulo prostático em 49%; 11% dos pacientes apresentaram história de ressecção transuretral e 16% obstrução urinária prévias. No grupo de baixo risco foram classificados 36.1% dos pacientes, 42.8% no grupo de risco intermediário e 21.1% foram considerados de alto risco. Hormonioterapia neoadjuvante por até 6 meses foi utilizada em 64% dos casos e teleterapia conformada em 19%. O seguimento médio foi de 50 meses (mediano de 48,4 meses), variando de 24 a 113 meses. Nove (2,2%) pacientes não responderam ao tratamento e 4,5% evoluíram a óbito por neoplasia prostática em um tempo médio de 22 meses. Falha bioquímica, tanto pelo critério ASTRO, quanto PHOENIX ocorreu em 9,6% dos pacientes. Entretanto, o tempo médio para falha foi de 13 meses pelo critério ASTRO e 26 meses pelo PHOENIX. O único fator preditivo de falha bioquímica pela análise multivariada por ambos os critérios ASTRO e PHOENIX foi a presença de nódulos prostáticos, mas pacientes com menos de 60 anos apresentaram maior chance de falha apenas pela definição de PHOENIX. Toxicidades urinárias agudas como retenção e hematúria ocorreram em 2,8% e 1,3% dos casos, respectivamente; sendo 23,7% grau 1, 15,1% grau 2 e 2% grau 3. Estenose uretral tardia foi observada em 8,5% dos pacientes e as toxicidades urinárias tardias foram grau 1 em 8,8%, grau 2 em 3,9%, grau 3, em 7,7% e grau 4, em 0,3% dos casos. Toxicidade urinária aguda foi relacionada a obstrução urinária prévia e maior dose de braquiterapia na uretra. Estenose uretral tardia também foi relacionada à maior dose uretral pela braquiterapia e com maior idade. Toxicidade retal precoce ocorreu como grau 1 em 14,8% dos pacientes; como grau 2, em 10,5%; e como grau 3, em 1,3%. Toxicidade retal tardia ocorreu como grau 1 em 3,4% dos pacientes; como grau 2, em 1,5%; como grau 3, em 0,3%; e como grau 4, em 0,3%. O risco para toxicidades retais agudas e tardias foi maior quando teleterapia conformada foi utilizada. Foi observada dor na glande em 4,9% dos pacientes e 71% apresentaram disfunção erétil tardiamente. O uso de Sildenafil foi eficiente em 59%. Pacientes mais velhos, ou com uma ou mais comorbidades, comprometimento prévio da ereção, ou que receberam radioterapia externa conformada apresentaram maior incidência de disfunção erétil. CONCLUSÕES: a associação de BATD como um reforço de dose para teleterapia mostrou ser um método viável e seguro apresentando boa eficácia e toxicidade aceitável. Os fatores relacionados à sobrevida e toxicidade podem colaborar na melhor seleção e tratamento de pacientes com câncer de próstata localizado. / INTRODUCTION: high dose-rate brachytherapy (HDR) for prostate cancer may be a nice treatment option for dose escalation as a boost, when associated to external beam irradiation, mainly if 3D conformal or more advanced technology is not available. PURPOSE: this study analyzes the results and toxicities of HDR brachytherapy boost prior to external beam radiotherapy with 2D or 3D conformal irradiation in patients with localized prostate cancer. Prognostic factors associated to overall and disease-free survival, as well as to treatment related toxicity were also studied. METHODS: A retrospective study of 403 patients with localized prostate adenocarcinoma treated between December 2000 and March 2004 was performed. According to the risk group, three fractions of HDR brachytherapy were delivered in the course of 24 hours, with a single implant: 5.5 to 6 Gy per fraction for low risk, 6 to 6.5 Gy per fraction for intermediate risk, and 6.5 to 7 Gy per fraction for high risk patients. The interval between fractions was of at least 6 hours. Conventional 2D or 3D conformal external beam irradiation was delivered to the prostate and seminal vesicles with 25 fractions of 1.8Gy (45Gy), about 2 weeks after brachytherapy. Multivariate analysis was done to evaluate unfavorable prognostic factors for biochemical failure free survival (BFFS). RESULTS: Patients presented a median age of 68 years, mean PSA of 9g/ml, and average prostate weight of 35 cc. Gleason score was equal to 6 in 43% of the cases, and 97% of the cases were at a stage lower than T2c. Prostate nodules were present in 49% of the patients; prior history of transurethral resection or urinary obstruction was present in 11% and 16% of the patients, respectively. There were 36.1% patients in the low risk group, 42.8% in the intermediate, and 21.1% in the high risk groups, respectively. Up to six months of neoadjuvant hormone therapy was used in 64% of the cases. External beam radiation was delivered with 3D conformal radiation in 19% of patients. The mean follow-up was 50 months ranging from 24 to 113 months (median 48,4 months). Nine patients (2.2%) did not respond to treatment. Death from prostate cancer occurred in 4.5% of the cases in a mean period of 22 months. Biochemical failure occurred in 9.6% according to both ASTRO and Phoenix consensus criteria. However, the mean time to relapse was 13 months using the ASTRO criteria and 26 months with the Phoenix definition. The five-year BFFS using the ASTRO criteria was 94.3%, 86.9% and 86.6% for the low, intermediate and high risk groups, respectively. Using the Phoenix criteria, 92.4%, 88.0% and 85.3% for the low, intermediate and high risk groups, respectively (p = 0.109). The only feature predicting biochemical failure (BF) in the multivariate analysis by both ASTRO and Phoenix criteria was the presence of prostate nodules, but patients younger than 60 years presented higher chance of BF using Phoenix criteria only. Acute urinary toxicities as urinary retention and hematúria occurred respectively in 2.8% and 1.3% of the patients. They presented as grade 1 in 23.7%, grade 2 in 15.1% and grade 3 in 2%. Late urethral stenosis was observed in 8.5% and late urinary toxicity was grade 1 in 8.8% of the patients, grade 2 in 3.9%, grade 3 in 7.7% and grade 4 in 0.3%. Acute urinary toxicity was related to previous urinary obstruction and higher brachytherapy dose to the urethra. Late urethral stenosis was related to older age and higher brachytherapy dose. Grade 1 early rectal toxicity occurred in 14.8% of the patients, grade 2 in 10.5% and grade 3 in 1.3%. Late rectal toxicity occurred as grade 1 in 3.4% of patients, as grade 2 in 1.5%, grade 3 in 0.3% and grade 4 in 0.3%. The risk of acute and late rectal toxicity was higher when 3D conformal irradiation was used. Glans pain was observed in 4.9% of the patients. Late sexual impotence occurred in 71% of cases. Sildenafil was effective in 59%. Sexual impotence presented a higher incidence in older patients with one or two co-morbidities, previous sexual impairment, or 3D conformal irradiation. CONCLUSIONS: the association of HDR brachytherapy as a boost for external beam irradiation seems to be a feasible and safe procedure, with good efficacy and acceptable toxicity. Factors related to survival and toxicity can help to better select and manage patients with localized prostate carcinoma.

Para avaliar o efeito de diferentes linhagens de leveduras, Saccharomyces cerevisiae, vivas, na redução de aflatoxicoses e, contribuir para o entendimento do modo de ação destas leveduras sobre aflatoxina B1 marcada com trítio (AFB13H), foram conduzidos três experimentos. No primeiro experimento, foram utilizados ratos Wistar para investigar o efeito de duas linhagens de S. cerevisiae (Y1026 e Y904), e da suplementação com aminoácidos na redução de aflatoxicoses. O bioensaio, em delineamento inteiramente casualizado, foi conduzido por 28 dias para avaliar sete tratamentos (dietas), sendo um livre de aflatoxinas e seis contendo 400g kg-1 de aflatoxinas; destes, cinco com leveduras, a saber: Y1026 (níveis de 0,5; 1,0 e 5,0%) e Y904 (níveis de 1% e 1%+1000ppm de metionina + 1000 ppm de cisteína). Não foram observadas diferenças estatistiticamente significativas no consumo de alimentos, ganho de peso, conversão alimentar e função hepática entre os animais submetidos aos diferentes tratamentos. No entanto, o exame histopatológico revelou que os animais que receberam aflatoxinas sem leveduras sofreram danos mais severos em relação aos que receberam aflatoxinas juntamente com leveduras, os quais apresentaram poucos danos celulares. Conclui-se que, as duas linhagens de leveduras em todas as situações estudadas apresentaram capacidade de reduzir as aflatoxicoses. O segundo ensaio foi conduzido com o objetivo de investigar o efeito de diferentes doses da levedura Y1026 no controle de aflatoxicoses em ratos. Neste bioensaio, os animais foram distribuídos em gaiolas individuais ao acaso, e foram submetidos a 7 tratamentos (dietas) por 60 dias, sendo uma sem aflatoxinas e seis contaminadas com 550 g kg-1 de aflatoxinas, das quais cinco contendo a levedura Y1026 (doses: 0,2; 0,5; 1,0; 2,0 e 5,0%). Foram realizadas análises sobre o aproveitamento do alimento, funções hepáticas e tecido hepático. O consumo de alimentos pelos animais alimentados com dieta livre de aflatoxinas foi maior do que pelos animais que receberam dietas contaminadas com a toxina, os demais parâmetros para julgamento do aproveitamento dos alimentos não diferiram estatisticamente entre os animais que foram submetidos a ambos os tratamentos. A atividade de enzimas hepáticas foi maior nos animais que não receberam a toxina do que nos demais. O exame histopatológico revelou que os animais que receberam aflatoxinas e aflatoxinas mais 0,2 ou 0,5% da levedura apresentaram sinais claros de hepatotoxidez e que os demais animais que ingeriram os níveis mais altos da levedura sofreram poucos danos celulares. Conclui-se que, a dose de levedura Y1026 aplicada foi determinante na redução das aflatoxicoses em ratos Wistar. No último bioensaio, trinta ratos foram alimentados por 28 dias seguindo-se quatro tratamentos (dietas): uma dieta livre de aflatoxinas e as outras três contaminadas com 500 g kg 1 de aflatoxina, sendo uma o controle com aflatoxinas e as outras duas na presença de 1% de levedura Y1026 ou Y904. No 18º dia, seis animais de cada um dos tratamentos que recebiam aflatoxinas foram transferidos para gaiolas metabólicas, onde permaneceram por cinco dias em adaptação e, no 23º dia, estes receberam, por via oral, uma dose simples de 2Ci/animal de AFB13H. Os animais restantes (três ratos em cada um dos tratamentos) foram utilizados nos exames histopatológicos. A radioatividade foi determinada 12, 24, 48, 72, 96 e 120 horas após a introdução do material radioativo nos animais. Os animais que receberam dietas contendo as leveduras apresentaram a absorção, a distribuição e a excreção da radioatividade mais lenta do que aqueles que não receberam os probióticos. O exame histopatológico revelou que os animais que ingeriram leveduras sofreram poucos danos celulares e que aqueles que não receberam levedura foram muito afetados. As leveduras apresentaram habilidade de reduzir aflatoxicoses e modificaram a absorção, a distribuição e a excreção da radioatividade de AFB13H em ratos Wistar. / The capacity of Saccharomyces cerevisiae, from two Strain, to reduce aflatoxicosis and the effect of yeast cells on tritium-labeled B1 aflatoxin (AFB13H) were investigated in three distinct studies. The effects of S. cerevisiae Y1026 and Y904 strains and diets amended with amino acids on the reduction of aflatoxicosis in Wistar rats were evaluated in the first study. A completely randomized block-designed bioassay with Wistar rats was conducted to evaluate seven formulations (Treatments), which consisted of an aflatoxin-free formulation and six formulations with 400 g kg-1 of aflatoxins. Of these, three formulations had the yeast strain Y1026 (at 0.5, 1.0 and 5.0%) and two had the strain Y904 (at 1% and 1%+1000ppm of methionine + 1000 ppm of cysteine). No statistical differences were observed for the food consumption, weights of the body organs, feed conversion and liver function between the animals fed the different treatments. Histopathological analysis revealed that animals fed aflatoxins diet without yeast cells had liver damage caused by the toxins and those that were fed aflatoxin-diet amended with yeast cells had less liver tissue damage. Therefore, the results obtained suggested that the presence of either yeast strain in the formulations caused a reduction in aflatoxicosis. The second study was conducted to investigate the effect of different dosages of the yeast strain Y1026 on the control of aflatoxicosis in rats. The bioassay was conducted with rats randomly placed in individual cages and fed seven different diets (7 treatments) for 60 days. These were an aflatoxin-free formulation and six others containing aflatoxins at 550 g kg-1, of which five had the yeast strain Y1026 (concentrations at 0.2; 0.5; 1.0; 2.0 and 5%). Feed conversion, liver functions indexes and liver tissue parameters were evaluated. The activity of the liver enzymes was greater in animals that fed the toxin-free diet when compared to other animals. Histopathological analysis showed that animals fed aflatoxin containing diets with and without 0.2 or 0.5% yeast cells showed clear signs of hepatotoxicity, while animals that were fed diets with higher concentrations of yeast cells had less liver tissue damage. The concentration of the yeast cells (Y1026) used in the formulations was correlated with the reduction of aflatoxicosis in Wistar rats. The third study fed Wistar rats an aflatoxin-free diet and diets with aflatoxins (at 500 g kg 1) and aflatoxin amended with a 1% concentration of the yeast strains Y1026 or Y904. In this study, six animals from each group fed the aflatoxin-diets were transferred to metabolic cages and received a single oral dose of AFB13H at 2Ci/animal. Three animals of each treatment were kept at the initial conditions and their liver tissues were used for histopathological analysis. Radiation levels in the animals were monitored at 12, 24, 48, 72, 96 and 120 h after receiving the labeled aflatoxin. Animals fed diets with active yeast cells had absorption, distribution and excretion levels of the labeled toxin different than those that did not receive the probiotic. Histopathological analysis showed that animals fed diets with yeast cells had less liver tissue damage while those fed the aflatoxin-diet had significantly higher liver damage. Therefore, these results indicate that active yeast cells have the ability to reduce aflatoxicosis and modify the absorption, distribution and excretion of radioactivity from AFB13H in Wistar rats.

This thesis reports an investigation into methods of determining the long term deposition field for atmospheric aerosols in areas of complex topography using the soil inventories of atmospherically derived radionuclides. Measurements of the radionuclides ²¹⁰Pb, ¹³⁷Cs, ¹³⁴Cs and ⁷Be in vegetation and soil have been made at five mountain locations in northern Britain. A description of the field sampling procedure, sample processing and y-ray analysis is given. Loss-on-ignition experiments to determine the organic fraction of sampled soils were also conducted on selected samples. The presence of frequent low level cloud shrouding mountain tops in the uplands of northern and western Britain leads to enhanced precipitation and also deposition of the major acidic ions, eg SO₃²⁻ and N0₃, due to the washout of the low level cloud by falling rain ('seeder-feeder scavenging') and also the direct deposition of cloud droplets ('occult deposition'). It is important to quantify the inputs of acidic deposition in these acid sensitive regions and direct measurements present many logistical problems. The radionuclide ²¹⁰Pb is attached to the same sub-micron aerosol size range in the atmosphere as the major acidic ions and following deposition attaches very strongly to organic matter in soils. In this study the soil inventory of atmospherically derived ²¹⁰Pb is used as a tracer of the deposition of acidic ions. As the half-life of ²¹⁰Pb is 22.3 years the soil inventory of ²¹⁰Pb(atmos), at a site undisturbed for - 100 years, represents deposition integrated over several decades. Initial sampling took place at the Merrick, an isolated mountain close to the coast in southwest Scotland, to test and develop the technique. Measurements showed the ²¹⁰Pb(atmos) inventory to increase with altitude at a greater rate than precipitation. Sampling at Great Dun Fell in Cumbria enabled the measured radionuclide inventories to be compared with detailed measurements of the variation of the wet deposition pattern with altitude, and also with a model of sulphate deposition. Close correspondence was found between the ²¹⁰Pb deposition profile and the deposition pattern, with altitude, for the major acidic ions. The three mountains Ben Cruachan, Beinn Dorain and Ben Lawers lie along an 80 km transect running roughly west to east from the western coast into the central Highlands. Sampling at these three mountains has yielded information on the change in the wet deposition field with distance inland. The measurements suggest that deposition of ²¹⁰Pb decreases, with distance from the western coast, at a greater rate than does precipitation. The soil inventory of ²¹⁰Pb(atmos) increases with altitude at a greater rate than rainfall at 4 of the 5 mountains. The results show that, around summits, on average, the concentration of ²¹⁰Pb in low level cloud is a factor of - 2 greater than in the frontal ('seeder') rain falling from higher altitude. This finding is in good agreement with detailed wet deposition measurements. The ²¹⁰Pb measurements are important in themselves as they help define the global and UK ²¹⁰Pb budget. From measurements made at 65 individual sites the mean ²¹⁰Pb(atmos) inventory is 0.44 ± 0.03 Bq cm⁻², with the mean of the average annual rainfall being 2,060 ± 70 mm yr⁻¹. These figures correspond to a mean concentration of ²¹⁰Pb in rainfall of 66 mBql⁻¹. The ¹³⁷Cs inventory has been separated into the fraction originating from nuclear weapons testing, ¹³⁷Cs(bomb), and the fraction due to the Chernobyl accident, ¹³⁷Cs(Chern). The measured ¹³⁷Cs(bomb) inventory ranges from a mean of 3,300 Bq m⁻² at Ben Lawers to 5,200 Bq m⁻² at Beinn Dorain. The ¹³⁷Cs(Chern) inventory is highly variable between locations ranging from a mean of 440 Bq m⁻² at Great Dun Fell to 14,900 Bqm⁻² at Ben Lawers reflecting the patchy nature of deposition, due largely to convective storms, during the passage of the radioactive plume. The radionuclide ¹³⁷Cs is shown to be relatively mobile in the organic soils which characterise the study areas. The cosmogenic radionuclide ⁷Be was measured in samples collected from the Merrick on 26th Oct 1988. The mean inventory was 0.039 Bq cm⁻², being associated with vegetation and the top few cm of the soil profile.

Shallow land burial in vadose zone sediment at the Hanford Site in Washington is being considered for the disposal of Category 3 low-level waste. A series of column experiments were conducted to evaluate and model the performance of the soil surrounding the trench encasement material for iodine-129 and technetium-99 by evaluating the mobility of these nuclides through the surrounding Trench 8 soil. These experiments were designed to determine effective diffusion coefficients for ¹²⁷I and ⁹⁹Tc through the following system: from contaminated soil into uncontaminated soil. The tests were performed at two different soil moisture contents to evaluate the effects of soil moisture content on diffusion. This thesis describes the experimental methods and presents the diffusion results for this media type. It was found that as the moisture content increased the diffusion increased by an order of magnitude (iodine 4% and 7% moisture content soil effective diffusion coefficients were 8.90E-08 and 1.84E-07 cm²/s respectively, and technetium 4% and 7% moisture content soil diffusion coefficients were 7.61E-08 and 1.45E-07 cm²/s respectively). These results, in combination with other diffusion systems results, will allow the development of release models and contaminant migration models that can be used to estimate the long-term fate of dose-controlling radionuclides that are or will be buried in solid waste burial trenches. / Graduation date: 2004

Chitosan is a biopolymer resulting from the deacetylation of chitin, the second most abundant biopolymer in nature. Chitosan has been successfully used in systems to remove metal ions and other pollutants from wastewater. Chitosan has shown promise as a sorbent for radionuclides in some aqueous waste streams. The sorption of these radionuclides by chitosan is studied to determine if chitosan could be used as a sorbent for aqueous waste streams containing these metals. The effect of various experimental conditions including sorbent particle size, agitation rate, hydration, temperature, pH, metal concentration and sorbent concentration are examined in this study. Results showed that sorption depends on the availability of access sites, controlled by the specific surface area of the sorbent. Sorption was observed to decrease with increasing temperature. The sorption isotherms and kinetics for Co(II), Eu(III) and U(VI) sorption onto chitosan were determined experimentally by batch sorption. Isotherms were fitted using the Langmuir and Freundlich models. Kinetics were modeled using the pseudo- first order, pseudo-second order, Elovich, and intraparticle diffusion models in order to determine possible rate-limiting steps. Most data were well described by the pseudo- second order and Elovich models. Multi-linearity was observed in the intraparticle diffusion model. The sorption capacity of the metals on chitosan was found to follow the order Co < Eu < U. / Graduation date: 2013