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NMR spectroscopy is a powerful technique that allows the study of short-range electronic effects and local structure. The aim of the work has been to separate and manipulate the many different interactions so that they can be individually measured. For this we have used multinuclear techniques and probes. We have measured a range of spectra for different organotin, iminophosphorane and lithium compounds. We have obtained a selection of spectra including (^19(F {(^1)H} and doubly-decoupled (^119)Sn {(^1)H, (^19)F} for the organotin fluorides (^n)Bu(_3)SnF, Mes(_3)SnF, SnF(_2), Me(_2)SnF(_2), and (^n)Bu(_2)SnF(_2). These have been used to calculate the effective shielding anisotropies, asymmetries, effective dipolar coupling (D'), and the anisotropy in the indirect coupling (∆J), using analyses of the spinning-sideband manifolds. Simulation programs have been written to simultaneously fit multiple sets of data, which reduce the fitting errors and give the relative orientations of the tensor interactions. The (^19)F chemical shifts, indirect coupling (^1)j(SnF) and (^1)∆J(SnF) data have been summarised. For (^n)Bu(_2)SnF(_2), a structure has been proposed based on comparisons with the NMR results from the other compounds. For the iminophosphoranes, the dipolar tensor and its orientation can be measured from the (^31)P static spectrum, whilst in the MAS spectrum residual dipolar coupling lineshapes are visible. These give information about the electric dipole nature of the P-N bond and the nature of its bonding. For the lithium nuclei, the quadrupolar interaction is small, but can be directly studied. With the two NMR-active isotopes both tire shielding and quadrupolar interactions can be measured. Ab initio calculations have been used to calculate certain NMR parameters such as the shielding, quadrupolar and indirect coupling tensors from the molecular structure. Experimental data have been compared against tlie calculations to verify the accuracy of the model. At present, there is good agreement between experimental and calculated results for (^6,7)Li, (^13)C, (^14,15)N and (^31)P, though (^119)Sn remains a challenge.

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Evidence that recoilless emission and absorption exist may be shown by an experiment in which the source gamma rays are allowed to pass through a suitable absorber to a detector.

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<p> This thesis represents a detailed assessment of the McMaster KN Accelerator site for the performance of a nuclear resonance absorption and fluorescence phenomenon in the 28Si nucleus. The main focus of this work is the 27Al(p, γ)^28 Si reaction, although other nuclear reactions are explored, such as: 27Al(p, p'γ)^27Al and 27Al(p, αγ)^24Mg. The gamma yield experiments from all these reactions suggest a repeatable and steady results, as well as very good agreement with the present literature. This is seen in chapter 2. Chapter 3 represents concrete nuclear resonance experiments with a direct ground state transition of the 12.33 MeV gamma energy from the 27Al(p, γ)^28Si reaction. These experiments are reproducible and repeatable with either HPGe or NaI(T1) (NaI elsewhere in text) detectors. Also, they are in close agreement with the literature.</p> <p> However, the main part of this work is described in chapter 4, where the first excited level of Si at 1.78 MeV is studied thoroughly. This is a pilot work that has never been attempted before. A thorough empirical approach is undertaken and described in section 4.1. This approach describes rationale for attempting nuclear resonance experiments with the first excited state of Si. The calculations suggest very close agreement between 12.33 MeV and 1.78 MeV experiments. Based on that, 7 different experimental sets, with several subsets ( within some of the sets) are performed. Very interesting results are obtained. However, so far, it cannot be concluded whether NRA/NRF experiments can be performed using the first excited state of Si. Most likely, hight current proton accelerators should be used and the experiments with 1.78 MeV lines should be repeated. These accelerators are described in chapter 5 and have the proton current output close to 1000 times higher than the McMaster KN accelerator. At the end, the dosimetry measurements suggest a negligible radiation dose from KN accelerator, as well as from these powerful accelerators.</p> / Thesis / Doctor of Philosophy (PhD)

Made available in DSpace on 2014-06-11T19:28:58Z (GMT). No. of bitstreams: 0 Previous issue date: 2005Bitstream added on 2014-06-13T19:37:35Z : No. of bitstreams: 1 venturelli_fas_me_araca.pdf: 528049 bytes, checksum: 64c9032185129f4901338d4e136d8aaa (MD5) / Universidade Estadual Paulista (UNESP) / Muito se discute sobre a posição ideal que o côndilo deve ocupar dentro da fossa mandibular. Apesar da Relação Central ser usada como uma posição de referência no campo da Odontologia, alguns autores não concordam que esta posição seja considerada fisiológica. Sendo assim, este estudo procurou avaliar a posição do côndilo dentro da fossa mandibular em um grupo de indivíduos assintomáticos, quando os dentes estão em máxima intercuspidação (MI), com placa miorrelaxante e com o Guia de Lucia interposto entre os dentes: a) por meio da ressonância nuclear magnética; b) da radiografia transcraniana; c) e pela análise do eixo horizontal de rotação, a partir de modelos montados em articulador. Os resultados mostraram que, apesar de os pacientes possuírem deslizes mandibulares entre as posições de RC, MI e com a placa- confirmados através da análise do eixo horizontal de rotação-, por meio de articulador semi-ajustável, as imagens por Ressonância Nuclear Magnética e Radiografia Transcraniana mostrou não haver diferenças estatisticamente significantes na posição condilar em relação às três posições estudadas e pode-se concluir também, que a Radiografia Transcraniana parece ser um método confiável para análise do posicionamento condilar. / Too much is discussed about the ideal position that the mandibular condyle should occupy inside of the mandibular fossa. In spite of the Centric Relation (CR) have been used as a reference position in dentistry, some authors don't agree that this position is considered physiologic. Then, this study evaluated the position of the condyle inside of the mandibular fossa in a group of asymptomatic individuals when the teeth are in a intercuspal position (IP), with stabilizing splint and with Lúcia's Jig interposed among the teeth: a) through the magnetic nuclear resonance; b) the transcranial radiographic; c) and by the analysis of the horizontal axis of rotation starting from mounted models in semiadjustable articulator. The results showed that in spite of the patients possess mandibular sliding ong the positions of CR, IP and with the splint, confirmed through the analysis of the rizontal axis of rotation, through semi-adjustable articulator, the images by Magnetic Nuclear sonance and Transcranial Radiogrraphic showed no statistically significant differences in the condylar position in relation to the three studied positions and that the Transcranial Radiographic seems to be a reliable method for analysis of the condylar positioning.

Made available in DSpace on 2014-06-11T19:35:08Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-04-28Bitstream added on 2014-06-13T19:45:05Z : No. of bitstreams: 1 santagneli_sh_dr_araiq.pdf: 2689918 bytes, checksum: 784026047bbf26adf41736474ff9bdcd (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Neste trabalho descreve-se o estudo estrutural do sistema binário As2S3-P2S5, e o efeito da incorporação do Ga2S3 na composição vítrea 50As2S3-50P2S5. Para o sistema As2S3-P2S5 foram obtidos vidros com concentrações até 70% P2S5. As temperaturas características dos vidros foram determinadas através de análise térmica diferencial. A investigação estrutural foi realizada utilizando-se as técnicas espectroscópicas de infravermelho, Raman e Ressonância Magnética Nuclear do 31P. A distribuição dos átomos de fósforo na estrutura vítrea foi avaliada através da intensidade da interação dipolar magnética entre núcleos de 31P, obtendo-se valores experimentais do segundo momento M2, utilizando a técnica de spin eco de Hahn. Foram realizadas simulações numéricas de M2 para o sistema As-P-S, considerando três modelos estruturais diferentes de distribuição dos 31P nos vidros: distribuição homogênea, distribuição randômica em uma rede do tipo ZnS e a formação de arranjos moleculares como As2P2S8, P4S9 e P4S10. Através dos experimentos de 31P-MAS, Raman e Infravermelho e dos resultados experimentais e numéricos de M2 obtidos, conclui- se que os vidros são constituídos por unidades S=PS3/2 tetraédricas, encontrando-se principalmente nos arranjos As2P2S8 até 50% de P2S5, acima dessa concentração é evidenciado a presença de unidades moleculares de P4S9 e/ou P4 S10. Para o sistema Ga-As-P-S evidenciou-se através das técnicas espectroscópicas de infravermelho e Raman a diminuição do caráter p da ligação P=S, indicando uma interação com o Ga2S3, resultando na formação de arranjos GaPS4 sobre os arranjos As2P2S8. Esta suposição também foi evidenciada através da diminuição da interação dipolar do 31P-31P. Para aplicação desses vidros, os fenômenos fotoinduzidos foram avaliados nas composições vítreas As2S3 e 80As2S3-20P2S5... / A structural study of the binary system As2S3-P2S5, and the effect of the incorporation of Ga2S3 in 50As2S3-50P2S5 glass are presented in this thesis. Starting from the As2S3 composition glasses, were obtained in the As2S3-P2S5 system for compositions up to 70 mol% P2S5. The characteristic temperatures of the glasses were obtained using differential thermal analysis. Infrared spectroscopy, Raman scattering and 31P Nuclear Magnetic Resonance were used in the structural study. The distribution of P atoms over the glass structure was investigated using a Hahn spin-echo sequence to evaluate the 31P-31P dipolar interactions through the measurement of the second moment M2. Numerical simulations of M2 were carried out assuming three different structural models for the glass: 1-P homogeneously dispersed on the As-S network, 2-P randomly distributed on the As-S network and 3-pseudomolecular As-P-S arrangements (as for example As2P2S8, P4S9 or P4S10). The spectroscopic results lead to the conclusion that the glasses are constituted by tetrahedral (S=PS3/2) units, mainly in As2P2S8 arrangements up to 50% of P2S5. Above this concentration the presence of molecular units of P4S9 and/or P4S10 is evidenced. For the Ga-As-P-S system the reduction of the double bond character (P=S) was deduced from Raman scattering and infrared absorption. The formation of GaPS4 groups on the base As2P2S8 groups was suggested. This assumption also is evidenced from the reduction of the dipole interaction of the 31P-31P. Photoinduced phenomena were evaluated for the As2S3 and 80As2S3-20P2S5 glass compositions. The samples were irradiated by different wavelengths (351, 488 e 514 nm) using a continuous Argon laser (CW), varying the power of irradiation and exposure time. A depression area was observed in the illuminated sample at 351 nm that could be due to either to etching either to vaporization...(Complete abstract click electronic access below)

Apresentam-se os resultados dos primeiros experimentos com o novo acelerador de elétrons do Laboratório do Acelerador Linear (LAL) do Instituto de Física da USP, cuja primeira fase de montagem encontra-se concluída. Adicionou-se uma linha de irradiação ao projeto original do Microtron, que permite usar o feixe de elétrons com 1,9 MeV de energia do injetor. Espectros de bremsstrahlung de elétrons em alvos finos de Ag e Au, observados a 30o e 60o em relação ao feixe, foram medidos com um detector coaxial de HPGe, cujas dimensões, inclusive do orifício interno e da camada morta do cristal, foram determinadas por medidas experimentais e simulações de Monte Carlo com o código MCNPX, a fim de estimar a resposta do detector para a deconvolução dos espectros. As secções de choque de produção de bremsstrahlung foram medidas tanto para todo o espectro observado (100 1910 keV) quanto para a região próxima ao tip (1700 1910 keV). Os resultados na região do tip concordam com as previsões dos códigos MCNPX e PENELOPE. As causas das discrepâncias observadas para energias menores que 1800 keV são discutidas. Apresenta-se também o projeto de um sistema de medidas de Ressonância Fluorescente Nuclear (NRF) para o estudo de excitações dipolares dos núcleos com fótons de bremsstrahlung, que se pretende usar assim que a energia dos elétrons do Microtron alcance 10 MeV. O projeto desse sistema leva em conta as particularidades da instalação do acelerador e da sala de irradiação e busca minimizar a radiação devida aos fótons espalhados nas paredes e aos nêutrons produzidos em reações fotonucleares. O comportamento dos elementos que conformam o sistema de NRF: radiador, colimador, blindagem dos detectores e coletor do feixe de fótons foram estudados por simulação em função das suas características dimensões, formas, materiais com o código MCNPX. Com o projeto final do arranjo experimental, avaliaram-se as intensidades de NRF que serão observadas pelos detectores de fótons com um alvo de 27Al, típico nesse tipo de medições, que indica a viabilidade desse tipo de experimento com o Microtron. / The results of the first experiments carried out in the new electron accelerator of the Linear Accelerator Laboratory (LAL) of the Physics Institute of Universidade de São Paulo are reported here. A 1.9 MeV beam line, which allows the use of the injector beam for experimental physics, was added to the original accelerator design. Electron bremsstrahlung spectra for Ag and Au thin targets observed at 30o and 60o with respect to the beam direction were collected in a HPGe coaxial detector, whose dimensions, including crystal inner hole dimensions and dead layer thickness, were estimated by means of combined experimental measurements and Monte Carlo simulations with the MCNP code, to evaluate the detector response function to perform the deconvolution of the spectrum. Cross sections for bremsstrahlung yield were determined for the entire measured energy range (100 1910 keV) and for the tip region (1700 1970 keV). The results in the tip region are in agreement with MCNPX and PENELOPE predictions. The possible causes for the disagreement at energies lower than 1800 keV are discussed. The design of a Nuclear Resonance Fluorescence (NRF) setup, aiming the study of dipolar excitations in nuclei with bremsstrahlung photons when the Microtron electron energy reaches 10 MeV, is also shown. The setup was designed with the characteristics of the Microtron building and facilities in mind, and searches to minimize the radiation caused by scattered photons and neutrons from photonuclear reactions. The behavior of the NRF setup elements: converter, collimator, detector shielding and photon beam dump, were studied by simulation as functions of their characteristics dimensions, shapes, materials using the MCNPX code. The spectral intensity to be observed by the photon detector in the designed NRF setup with a 27Al reference target, typical for NRF measurements, was assessed by simulation and shows the feasibility of this sort of experiment with the Microtron.