Antimicrobials are commonly used to treat mycoplasmosis in animals. In spite of this and the fact that antimicrobial resistance has been recorded for this group of bacteria there are no universally accepted in vitro means of testing for this resistance, nor is resistance testing for mycoplasmas a routine in most veterinary laboratories. So prior to testing for resistance to a number of mycoplasmas isolated from animals in South Africa it was necessary to compare different tests including broth and agar microdilution tests to find out which one would perform best. Using the field strains M. bovis, M. crocodyli, M. felis, M. gallisepticum and M. synoviae, and the reference strains M. gallisepticum 56USDA, M. gallisepticum VaxSafe MG vaccine strain, M. mycoides T1/44 vaccine strain, and M. mycoides Ygoat (11706) broth- and agar-microdilution minimum inhibitory concentration (MIC)tests were performed using either modified Hayflicks or Mycoplasma synoviae media. Two different metabolism indicator systems were compared in the broth microdilution test (BrMIC) namely sugar fermentation (glucose or pyruvate) with phenol red (SFS) and evidence of reduction with resazurin (AlamurBlue®). It was also tested whether amoxicillin and clavulanic acid (ACA) could be used in the tests to reduce problems associated with contamination. Statistical analyses of the tests (repeatability and linear association) indicated that the BrMIC with SFS was the most reproducible method (pooled standard deviation = 0.14). The antimicrobial ACA was found to not to affect the MIC values (R2= 0.976 to 0.996). Furthermore one hundred forty two field strains including 93 M. bovis, 5 M. synoviae, 21 M. gallisepticum, 13 M. bovirhinis, 8 M. crocodyli and 6 M. felis were tested using the BrMIC+SFS with ACA method. Generally the mycoplasmas originating from poultry were resistant to commonly used antimicrobials and had higher MIC50 and MIC90 values than isolates originating from cattle, crocodiles and cats. It was found that most of the mycoplasmas were susceptible to doxycycline (tetracycline) and enrofloxacin with the exception of M. gallisepticum where 17.9% of strains were resistant to both. Resistance to tiamulin (100%) and tylosin (20 to 64%) was high for the poultry mycoplasmas. Most field isolates tested were resistant to erythromycin, nalidixic acid, florfenicol, norfloxacin, neomycin, sulphamethoxazole, trimethoprim and sulphamethoxazole/ trimethoprim combination, mostly resistant to norfloxacin and florfenicol. It is concluded that BrMIC+SFS with ACA method is a reproducible method that reduces any problems with bacterial contamination. As observed with the poultry strains, it is quite clear that antimicrobial resistance is developing to commonly used antimicrobials such as tylosin, the related pleuromutilins, fluoroquinolones and tetracyclines. In species where antimicrobial therapy is applied routinely such as poultry and possibly feedlot cattle, it is recommended that MIC testing is done prior to any therapeutic interventions. / Dissertation (MSc)--University of Pretoria, 2010. / Veterinary Tropical Diseases / unrestricted

In this work magnetic properties of copper(II) complexes on N-(hydroxyalkyl) pyrrole-2-aldimines were investigated by various techniques, one of which was magnetic susceptibility. Magnetic moments are not directly determined experimentally, but magnetic susceptibilities are.

A presente tese aborda a temática da vulnerabilidade da população frente às situações de ameaça e risco. A pesquisa realizou-se junto ao perímetro urbano da cidade de Santa Maria na região central do Rio Grande do Sul. A vulnerabilidade foi avaliada com relação aos fenômenos desencadeados pelas dinâmicas fluvial e de encosta, mais especificamente, movimentos de massa, inundações e erosão de margens. O objetivo principal do trabalho consiste na análise de variáveis determinantes para os graus de vulnerabilidade da população que reside em áreas sob ameaça de desastres naturais. A metodologia resume-se na análise de imagens DigitalGlobe obtidas via Google Earth Pro (2012) para a determinação das áreas urbanas ocupadas e susceptíveis aos fenômenos causadores de desastre junto às encostas e à rede de drenagem; para a obtenção dos graus de vulnerabilidade foi utilizada a base de informações referente aos Setores Censitários (IBGE, 2010): rendimento mensal, taxa de idosos e crianças, taxa de analfabetismo, à esses dados foram acrescidos o número de residências e o padrão urbano construtivo das moradias por área sob ameaça. A correlação das variáveis determinou quatro graus de vulnerabilidade: Grau I (Baixo), Grau II (Médio), Grau III (Alto) e Grau IV (Muito Alto). Verifica-se áreas sob ameaça nos patamares mais elevados das encostas, no entanto, existem situações perigosas em patamares com memores inclinações, devido, principalmente, às alterações realizadas nos taludes para a edificação das moradias. Quanto aos processos de dinâmica fluvial, a ameaça refere-se às inundações e à erosão de margens. A ocupação expandiu-se ao longo das planícies de inundação de inúmeros cursos fluviais ao longo do perímetro urbano, sendo, portanto, praticamente inevitáveis os episódios desta natureza. A erosão das margens fluviais são sentidas quase que exclusivamente pelos moradores que edificaram suas residências junto aos terrenos marginais, com distância aproximada de 5 metros do leito. A população mais vulnerável é aquela que apresenta situação socioeconômica menos favorecida, com idade superior à 65 e inferior à 15 anos de idade, com taxa elevada de analfabetismo e ausência de serviços urbanos básicos. Apesar da existência de leis e projetos relacionados à problemática dos desastres, o gerenciamento das áreas sob ameaça é ineficiente, favorecendo o surgimento de inúmeras situações perigosas. / This paper is about the risk ok the population in some kind of situations. The research was conduct in the urban perimeter of Santa Maria town, central part of Rio Grande do Sul state. The topic was the analysis of the vulnerability caused by the mass movements and floods in the river and also the deterioration on the banks. The main objective is the analyses of the level of risk areas of natural disasters that population face. To active this objective the study uses Google Earth Pro (2012) Digital Globes pictures to see where was the urban areas near at river banks with higher risk of disasters. To obtain the risk levels was used some parts of Census (IBGE 2010) more specific the how much money the families makes in one mouth also the number of young's and elderly and also the number and material used in construction of houses. Was stabilized four levels of risk in crescent order we have level one (Low risk), level two (Medium risk), level three (High risk) and level four (Very High Risk). Was possible the discover some areas in the higher level of risk in more elevate terrains and also some danger places in lower fields however the highest risk is in areas more flats but changed by manmade activities in special house constructions. The main danger caused by river stream is the floods and erosion of banks. The population occupied flat terrains near the rivers that were naturally flooded and because that is almost impossible to avoid this kind of disaster. The erosion on bank happens in land where houses was built near of 5 meters of rivers. The populations in higher danger is the more lower financial classes with ages up to 65 years and under 15 and high rates of analphabets and no basic state services. Even with laws and projects to prevent disasters situations the management of risk areas is inefficient and cooperate to more possible disasters.

A presente tese aborda a temática da vulnerabilidade da população frente às situações de ameaça e risco. A pesquisa realizou-se junto ao perímetro urbano da cidade de Santa Maria na região central do Rio Grande do Sul. A vulnerabilidade foi avaliada com relação aos fenômenos desencadeados pelas dinâmicas fluvial e de encosta, mais especificamente, movimentos de massa, inundações e erosão de margens. O objetivo principal do trabalho consiste na análise de variáveis determinantes para os graus de vulnerabilidade da população que reside em áreas sob ameaça de desastres naturais. A metodologia resume-se na análise de imagens DigitalGlobe obtidas via Google Earth Pro (2012) para a determinação das áreas urbanas ocupadas e susceptíveis aos fenômenos causadores de desastre junto às encostas e à rede de drenagem; para a obtenção dos graus de vulnerabilidade foi utilizada a base de informações referente aos Setores Censitários (IBGE, 2010): rendimento mensal, taxa de idosos e crianças, taxa de analfabetismo, à esses dados foram acrescidos o número de residências e o padrão urbano construtivo das moradias por área sob ameaça. A correlação das variáveis determinou quatro graus de vulnerabilidade: Grau I (Baixo), Grau II (Médio), Grau III (Alto) e Grau IV (Muito Alto). Verifica-se áreas sob ameaça nos patamares mais elevados das encostas, no entanto, existem situações perigosas em patamares com memores inclinações, devido, principalmente, às alterações realizadas nos taludes para a edificação das moradias. Quanto aos processos de dinâmica fluvial, a ameaça refere-se às inundações e à erosão de margens. A ocupação expandiu-se ao longo das planícies de inundação de inúmeros cursos fluviais ao longo do perímetro urbano, sendo, portanto, praticamente inevitáveis os episódios desta natureza. A erosão das margens fluviais são sentidas quase que exclusivamente pelos moradores que edificaram suas residências junto aos terrenos marginais, com distância aproximada de 5 metros do leito. A população mais vulnerável é aquela que apresenta situação socioeconômica menos favorecida, com idade superior à 65 e inferior à 15 anos de idade, com taxa elevada de analfabetismo e ausência de serviços urbanos básicos. Apesar da existência de leis e projetos relacionados à problemática dos desastres, o gerenciamento das áreas sob ameaça é ineficiente, favorecendo o surgimento de inúmeras situações perigosas. / This paper is about the risk ok the population in some kind of situations. The research was conduct in the urban perimeter of Santa Maria town, central part of Rio Grande do Sul state. The topic was the analysis of the vulnerability caused by the mass movements and floods in the river and also the deterioration on the banks. The main objective is the analyses of the level of risk areas of natural disasters that population face. To active this objective the study uses Google Earth Pro (2012) Digital Globes pictures to see where was the urban areas near at river banks with higher risk of disasters. To obtain the risk levels was used some parts of Census (IBGE 2010) more specific the how much money the families makes in one mouth also the number of young's and elderly and also the number and material used in construction of houses. Was stabilized four levels of risk in crescent order we have level one (Low risk), level two (Medium risk), level three (High risk) and level four (Very High Risk). Was possible the discover some areas in the higher level of risk in more elevate terrains and also some danger places in lower fields however the highest risk is in areas more flats but changed by manmade activities in special house constructions. The main danger caused by river stream is the floods and erosion of banks. The population occupied flat terrains near the rivers that were naturally flooded and because that is almost impossible to avoid this kind of disaster. The erosion on bank happens in land where houses was built near of 5 meters of rivers. The populations in higher danger is the more lower financial classes with ages up to 65 years and under 15 and high rates of analphabets and no basic state services. Even with laws and projects to prevent disasters situations the management of risk areas is inefficient and cooperate to more possible disasters.

A presente tese aborda a temática da vulnerabilidade da população frente às situações de ameaça e risco. A pesquisa realizou-se junto ao perímetro urbano da cidade de Santa Maria na região central do Rio Grande do Sul. A vulnerabilidade foi avaliada com relação aos fenômenos desencadeados pelas dinâmicas fluvial e de encosta, mais especificamente, movimentos de massa, inundações e erosão de margens. O objetivo principal do trabalho consiste na análise de variáveis determinantes para os graus de vulnerabilidade da população que reside em áreas sob ameaça de desastres naturais. A metodologia resume-se na análise de imagens DigitalGlobe obtidas via Google Earth Pro (2012) para a determinação das áreas urbanas ocupadas e susceptíveis aos fenômenos causadores de desastre junto às encostas e à rede de drenagem; para a obtenção dos graus de vulnerabilidade foi utilizada a base de informações referente aos Setores Censitários (IBGE, 2010): rendimento mensal, taxa de idosos e crianças, taxa de analfabetismo, à esses dados foram acrescidos o número de residências e o padrão urbano construtivo das moradias por área sob ameaça. A correlação das variáveis determinou quatro graus de vulnerabilidade: Grau I (Baixo), Grau II (Médio), Grau III (Alto) e Grau IV (Muito Alto). Verifica-se áreas sob ameaça nos patamares mais elevados das encostas, no entanto, existem situações perigosas em patamares com memores inclinações, devido, principalmente, às alterações realizadas nos taludes para a edificação das moradias. Quanto aos processos de dinâmica fluvial, a ameaça refere-se às inundações e à erosão de margens. A ocupação expandiu-se ao longo das planícies de inundação de inúmeros cursos fluviais ao longo do perímetro urbano, sendo, portanto, praticamente inevitáveis os episódios desta natureza. A erosão das margens fluviais são sentidas quase que exclusivamente pelos moradores que edificaram suas residências junto aos terrenos marginais, com distância aproximada de 5 metros do leito. A população mais vulnerável é aquela que apresenta situação socioeconômica menos favorecida, com idade superior à 65 e inferior à 15 anos de idade, com taxa elevada de analfabetismo e ausência de serviços urbanos básicos. Apesar da existência de leis e projetos relacionados à problemática dos desastres, o gerenciamento das áreas sob ameaça é ineficiente, favorecendo o surgimento de inúmeras situações perigosas. / This paper is about the risk ok the population in some kind of situations. The research was conduct in the urban perimeter of Santa Maria town, central part of Rio Grande do Sul state. The topic was the analysis of the vulnerability caused by the mass movements and floods in the river and also the deterioration on the banks. The main objective is the analyses of the level of risk areas of natural disasters that population face. To active this objective the study uses Google Earth Pro (2012) Digital Globes pictures to see where was the urban areas near at river banks with higher risk of disasters. To obtain the risk levels was used some parts of Census (IBGE 2010) more specific the how much money the families makes in one mouth also the number of young's and elderly and also the number and material used in construction of houses. Was stabilized four levels of risk in crescent order we have level one (Low risk), level two (Medium risk), level three (High risk) and level four (Very High Risk). Was possible the discover some areas in the higher level of risk in more elevate terrains and also some danger places in lower fields however the highest risk is in areas more flats but changed by manmade activities in special house constructions. The main danger caused by river stream is the floods and erosion of banks. The population occupied flat terrains near the rivers that were naturally flooded and because that is almost impossible to avoid this kind of disaster. The erosion on bank happens in land where houses was built near of 5 meters of rivers. The populations in higher danger is the more lower financial classes with ages up to 65 years and under 15 and high rates of analphabets and no basic state services. Even with laws and projects to prevent disasters situations the management of risk areas is inefficient and cooperate to more possible disasters.

Propriedades ópticas, magnéticas e elásticas de duas liomesofases nemáticas tipo I (decilsulfato de sódio/água/ n-decanol e laurato de potássio/água/cloreto de potássio) e urna tipo II (decilsulfato de sódio/água/n-decanol /sulfato de sódio) são estudadas. Nas investigações de tais propriedades as medidas realizadas e instrumentação/meios utilizados foram os seguintes: medidas de sinais ópticos, texturas e temperaturas de transições de fases foram obtidas com auxilio de um microscópio petrográfico com temperatura controlada na platina; medidas de índices de refração e birrefringências obtiveram- se com adaptações do refratômetro de Pulfrich; medidas de susceptibilidades diamagnéticas direcionais foram realizadas com adaptações ao magnetômetro de amostra vibrante; medidas de constantes elásticas foram obtidas com auxilio de uma montagem especial. São realizados cálculos para as susceptibilidades diamagnéticas direcionais e respectivas anisotropias moleculares para alcanos, álcoois e anfifilicos de interesse em liornesofases . Da comparação entre as anisotropias moleculares calculadas e as medidas em liomesofases correspondentes, infere-se que o ordenamento molecular de anfifilicos, nas mesofases, deve ser alto. O método de Kirkwood, que permite correlacionar polarizabilidade elétrica com a susceptibilidade diamagnética molecular média em substâncias puras, é estendido e adaptado a misturas complexas, criando assim urna promissora perspectiva de correlação entre as medidas ópticas e magnéticas em liomesofases. Evidências experimentais diretas, da aplicabilidade da teoria do continuo para termo trópicos às liomesofases, são apresentadas. / The optical, magnetic and elastic properties of three nematic lyomesophases are studied. Two are type I (Na decyl sulfate/ water/n- decanol and K laurate/water/K chloride) and one type II (Na decyl sulfate/water/n- decano l/Na sulfate). To measure these properties we used the following equipment : texture and optical sign were observed by optical microscopy with temperature controlled, hot and cold, stages; refractive indices were measured in an adapted Pulfrich refratometer; the individual elements of the diamagnetic susceptibility tensor were measured with a vibrating sample magnetometer; the elastic constants were measured using the Frederikzs transition in a special experimental set-up. Starting from the concept of localized magnetic susceptibilities, molecular anisotropies were calculated for saturated hydrocarbons , alcohols and amphiphilic compounds, which are of interest for lyomesophases. Comparing these results with the experimentally measured anisotropies of the lyomesophases it is possible to conclude that a high degree of molecular order is present in the nematic amphiphilic systems. The Kirkwood method is extended and adapted for complex mixtures. The use of this method opens new perspectives for exploring the correlation between the molecular polarizability and the mean diamagnetic susceptibility.

Propriedades ópticas, magnéticas e elásticas de duas liomesofases nemáticas tipo I (decilsulfato de sódio/água/ n-decanol e laurato de potássio/água/cloreto de potássio) e urna tipo II (decilsulfato de sódio/água/n-decanol /sulfato de sódio) são estudadas. Nas investigações de tais propriedades as medidas realizadas e instrumentação/meios utilizados foram os seguintes: medidas de sinais ópticos, texturas e temperaturas de transições de fases foram obtidas com auxilio de um microscópio petrográfico com temperatura controlada na platina; medidas de índices de refração e birrefringências obtiveram- se com adaptações do refratômetro de Pulfrich; medidas de susceptibilidades diamagnéticas direcionais foram realizadas com adaptações ao magnetômetro de amostra vibrante; medidas de constantes elásticas foram obtidas com auxilio de uma montagem especial. São realizados cálculos para as susceptibilidades diamagnéticas direcionais e respectivas anisotropias moleculares para alcanos, álcoois e anfifilicos de interesse em liornesofases . Da comparação entre as anisotropias moleculares calculadas e as medidas em liomesofases correspondentes, infere-se que o ordenamento molecular de anfifilicos, nas mesofases, deve ser alto. O método de Kirkwood, que permite correlacionar polarizabilidade elétrica com a susceptibilidade diamagnética molecular média em substâncias puras, é estendido e adaptado a misturas complexas, criando assim urna promissora perspectiva de correlação entre as medidas ópticas e magnéticas em liomesofases. Evidências experimentais diretas, da aplicabilidade da teoria do continuo para termo trópicos às liomesofases, são apresentadas. / The optical, magnetic and elastic properties of three nematic lyomesophases are studied. Two are type I (Na decyl sulfate/ water/n- decanol and K laurate/water/K chloride) and one type II (Na decyl sulfate/water/n- decano l/Na sulfate). To measure these properties we used the following equipment : texture and optical sign were observed by optical microscopy with temperature controlled, hot and cold, stages; refractive indices were measured in an adapted Pulfrich refratometer; the individual elements of the diamagnetic susceptibility tensor were measured with a vibrating sample magnetometer; the elastic constants were measured using the Frederikzs transition in a special experimental set-up. Starting from the concept of localized magnetic susceptibilities, molecular anisotropies were calculated for saturated hydrocarbons , alcohols and amphiphilic compounds, which are of interest for lyomesophases. Comparing these results with the experimentally measured anisotropies of the lyomesophases it is possible to conclude that a high degree of molecular order is present in the nematic amphiphilic systems. The Kirkwood method is extended and adapted for complex mixtures. The use of this method opens new perspectives for exploring the correlation between the molecular polarizability and the mean diamagnetic susceptibility.

The aim of this thesis was to investigate some methods for quantitative analysis of bone structure, particularly techniques which might ultimately be applied post-operatively following orthopaedic reconstruction operations. Initially it was decided to explore the efficacy of MRI in quantifying the bone structure at high resolution by comparing high resolution MRI against 'gold standards' such as Scanning Electron Microscopy (SEM) and optical histology. This basic study provided a measure of the distortions in the morphological bone parameters derived from MR images due to susceptibility artefacts and partial volume effects. The study of bone architecture was then extended to a model of advanced renal osteodystrophy in a growing rat. For this study, high-resolution micro computed tomography (microCT) was used and as a result of the high resolution images obtained, three new bone morphological parameters were introduced to characterise the bone structure. The desire to study bone architecture post-operatively in hip replacements led to a preliminary study on ex-vivo sheep acetabulae following total hip replacement, to determine the extent that the bone architecture could be investigated around the acetabulum. The motivation for studying the acetabulum was based on the high occurrence of debonding at the bone / prosthesis interface. This study demonstrated the superior nature of 3D MRI over conventional x-ray radiographs in early quantitation of fibrous membranes located between the host bone and the non-metallic implant and/or the bone cement. The presence of such fibrous membranes is strongly indicative of failure of the prosthesis. When using clinical MRI to image post-operative hip replacement, the image quality is severely affected by the presence of the metallic implant. The head of the prosthesis is shaped like a metal sphere and is located in the acetabular cup. This problem was investigated by performing simulations of MR images in the presence of the field perturbation induced by the presence of a metal sphere, with the effects of slice excitation and frequency encoding incorporated into the simulations. The simulations were compared with experimental data obtained by imaging a phantom comprising a stainless steel ball bearing immersed in agarose gel. The simulations were used to predict the effects of changing imaging parameters that influence artefact size and also to show how current metal artefact reduction techniques such as view angle tilting (VAT) work and to identify their limitations. It was shown that 2D SE and VAT imaging techniques should not be used when metallic prosthesis are present due to extreme slice distortion, whereas 3D MRI provided a method that has no slice distortion, although the effects of using a frequency encoding gradient still remain.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The present work has as general objective to carry out geoenvironmental zoning applied in the study of potentialities and susceptibilities and of use and occupation in the municipality of Rosário do Sul. The choice for the study area is justified because there are already several studies in the west section of Rio Grande do Sul, mainly in the Ibicuí River Basin. In addition, it should be noted that this work is part of the LAGEOLAM (Environmental Geology Laboratory) which has a line of research directed to the Municipal Geoenvironmental Atlas, and considering this, in the future the municipality of Rosário do Sul may also fit in this proposal. The bibliographic review of the present work presented questions related to the Systemic Approach and the Geosystems, Methodologies for Relief Mapping, Geoenvironmental Studies and Geoenvironmental Zoning, besides the use of Geographic Information Systems for Geoenvironmental Studies. The method adopted for the present study used the method of investigation of the systemic approach and was divided into three major steps: Data Collection and Production, Correlation of Information and the Geoenvironmental Zoning of the municipality of Rosário do Sul. As a result of this research, it presents first an analysis of the physical elements of the landscape, contemplating hydrography, relief, lithology and soils. After that, it was made the morpho-lithological compartmentalization of the study area, using as a basis the lithological characteristics and the partitioning of the relief of the municipality of Rosário do Sul. Subsequently, a temporal analysis of land use and occupation was carried out, with the aim of identifying the transformations that occurred during the last 20 years in the landscape that configure the study area. Finally, the geoenvironmental zoning of the municipality of Rosário do Sul was presented, dividing the study area into five systems and nine geoenvironmental units: Caverá System including Altitudes Hills, Association of Hillock and Earthmounds and Hillock and Isolated Earthmounds; Recent Deposits System composed of Ibirapuitã and Santa Maria units; Ibicuí da Armada System; Santa Maria system subdivided by the Botucatu, Guará, Piramboia and Sanga do Cabral units and finally the Urban System. The Geoenvironmental systems and units were characterized in terms of potentialities and susceptibilities related to use and occupation, with Santa Maria and Urban systems being the most susceptible in the study area. / O presente trabalho tem como objetivo geral realizar um zoneamento geoambiental aplicado ao estudo das potencialidades e suscetibilidades ambientais e de uso e ocupação no município de Rosário do Sul. A escolha pela área de estudo justifica-se em razão de já existirem diversos estudos realizados na porção oeste do Rio Grande do Sul, principalmente na Bacia Hidrográfica do Rio Ibicuí. Além disso, destaca-se que esse trabalho integra a proposta do Laboratório de Geologia Ambiental que possui uma linha de pesquisa direcionada aos Atlas Geoambientais Municipais, e diante disso, futuramente o município de Rosário do Sul também poderá se enquadrar dentro dessa proposta. A revisão bibliográfica do presente trabalho apresentou questões relacionadas a Abordagem Sistêmica e os Geossistemas, Metodologias para o Mapeamento do Relevo, Estudos Geoambientais e o Zoneamento Geoambiental, além da Utilização dos Sistemas de Informações Geográficas para os Estudos Geoambientais. A metodologia adotada para o presente trabalho empregou o método de investigação da abordagem sistêmica e foi dividida em três grandes etapas: Levantamento e Produção de Dados, Correlação das Informações e o Zoneamento Geoambiental do município de Rosário do Sul. Como resultados dessa pesquisa, apresenta-se primeiramente uma análise dos elementos físicos da paisagem, contemplando a hidrografia, o relevo, a litologia e os solos. Após isso, foi realizada a compartimentação morfolitológica da área de estudo, utilizando como base as características litológicas e a compartimentação do relevo do município de Rosário do Sul. Posteriormente, foi realizada uma análise temporal do uso e ocupação da terra, com o objetivo de identificar as transformações ocorridas ao longos dos últimos 20 anos na paisagem que configura a área de estudo. Por fim, apresentou-se o zoneamento geoambiental do município de Rosário do Sul, dividindo a área de estudo em cinco sistemas e nove unidades geoambientais: Sistema Caverá englobando as unidades das Colinas de Altitudes, Associação de Morros e Morrotes e os Morros e Morrotes Isolados; Sistema Depósitos Recentes composto pelas unidades Ibirapuitã e Santa Maria; Sistema Ibicuí da Armada; Sistema Santa Maria subdividido pelas unidades Botucatu, Guará, Piramboia e Sanga do Cabral; e por último o Sistema Urbano. Os sistemas e as unidades geoambientais foram caracterizados frente as potencialidades e as suscetibilidades com relação ao uso e a ocupação, sendo os sistemas Santa e Urbano os mais suscetíveis da área de estudo.

Magnetic resonance imaging (MRI) utilizes the magnetic properties of tissues to generate image-forming signals. MRI has exquisite soft-tissue contrast and since tumors are mainly soft-tissues, it offers improved delineation of the target volume and nearby organs at risk. The proposed Magnetic Resonance-only Radiotherapy (MR-only RT) work flow allows for the use of MRI as the sole imaging modality in the radiotherapy (RT) treatment planning of cancer. There are, however, issues with geometric distortions inherent with MR image acquisition processes. These distortions result from imperfections in the main magnetic field, nonlinear gradients, as well as field disturbances introduced by the imaged object. In this thesis, we quantified the effect of system related and patient-induced susceptibility geometric distortions on dose distributions for prostate as well as head and neck cancers. Methods to mitigate these distortions were also studied. In Study I, mean worst system related residual distortions of 3.19, 2.52 and 2.08 mm at bandwidths (BW) of 122, 244 and 488 Hz/pixel up to a radial distance of 25 cm from a 3T PET/MR scanner was measured with a large field of view (FoV) phantom. Subsequently, we estimated maximum shifts of 5.8, 2.9 and 1.5 mm due to patient-induced susceptibility distortions. VMAT-optimized treatment plans initially performed on distorted CT (dCT) images and recalculated on real CT datasets resulted in a dose difference of less than 0.5%.  The magnetic susceptibility differences at tissue-metallic,-air and -bone interfaces result in local B0 magnetic field inhomogeneities. The distortion shifts caused by these field inhomogeneities can be reduced by shimming.  Study II aimed to investigate the use of shimming to improve the homogeneity of local  B0 magnetic field which will be beneficial for radiotherapy applications. A shimming simulation based on spherical harmonics modeling was developed. The spinal cord, an organ at risk is surrounded by bone and in close proximity to the lungs may have high susceptibility differences. In this region, mean pixel shifts caused by local B0 field inhomogeneities were reduced from 3.47±1.22 mm to 1.35±0.44 mm and 0.99±0.30 mm using first and second order shimming respectively. This was for a bandwidth of 122 Hz/pixel and an in-plane voxel size of 1×1 mm2.  Also examined in Study II as in Study I was the dosimetric effect of geometric distortions on 21 Head and Neck cancer treatment plans. The dose difference in D50 at the PTV between distorted CT and real CT plans was less than 1.0%. In conclusion, the effect of MR geometric distortions on dose plans was small. Generally, we found patient-induced susceptibility distortions were larger compared with residual system distortions at all delineated structures except the external contour. This information will be relevant when setting margins for treatment volumes and organs at risk.   The current practice of characterizing MR geometric distortions utilizing spatial accuracy phantoms alone may not be enough for an MR-only radiotherapy workflow. Therefore, measures to mitigate patient-induced susceptibility effects in clinical practice such as patient-specific correction algorithms are needed to complement existing distortion reduction methods such as high acquisition bandwidth and shimming.