Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2014-07-31T14:59:03Z No. of bitstreams: 2 license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Dissertacao Adriano da Silva.pdf: 424521 bytes, checksum: 34a2cdf44500a8e6bdf0f05b3a673f5f (MD5) / Made available in DSpace on 2014-07-31T14:59:03Z (GMT). No. of bitstreams: 2 license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Dissertacao Adriano da Silva.pdf: 424521 bytes, checksum: 34a2cdf44500a8e6bdf0f05b3a673f5f (MD5) Previous issue date: 2009 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / In this work we report results for the polarizability, and first and second hyperpolariz- abilities of the methanol molecule including vibrational corrections and electron correlation effects. The Vibrational corrections were computed using the perturbation theoretic approach of Bishop and Kirtman and the electron correlation effects were taken into account through the CCSD(T) method implemented in the GAUSSIAN 03 program. The electronic contributions to the electric properties were calculated using the finite-field scheme. Comparisons of our CCSD(T) values with previous TDHF result show that the electron correlation effects, are in general, important. An analysis of the importance of the vibrational corrections shows that the zpva correction is not negligible, specially for the hyperpolarizabilities. The pv correction is, in general, important and the double-harmonic approximation is suitable to the calculation of this correction for most of the nonlinear optical processes studied. / Neste trabalho apresentamos resultados para a polarizabilidade e para a primeira e segunda hiperpolarizabilidades da mol ́ecula de metanol incluindo correçõoes vibracionais e efeitos de correlação eletrônica. As correções vibracionais foram calculadas usando a aproximação de perturbação teórica de Bishop e Kirtman e os efeitos de correlação eletrônica foram tomados em consideraçã através do método de CCSD(T) implementado no programa GAUSSIAN 03. As contribuições eletrônicas para as propriedades elétricas foram calculadas utilizando o esquema de campo finito. Comparações entre nossos valores CCSD(T) e os valores TDHF publicados anteriormente mostram que os efeitos de correla ̧c ̃ao eletrˆonica s ̃ao importantes. Uma an ́alise da importância das correções vibracionais mostra que a contribuição zpva não é desprezível, especialmente para as hiperpolarizabilidades. A correção ( pv) em geral é importante e a aproximação duplo-harmônico é adequada para o cálculo desta correção para a maioria dos processos óptica não-linear estudados aqui.

Um estudo do decaimento β- do 127Te, via espectroscopia gama, foi realizado utilizando um detector de HPGe de alta resolução. As medidas foram realizadas na região de energia de 30 keV a 1,0 MeV, com o objetivo de obter uma melhor compreensão de sua estrutura nuclear. As fontes radioativas de 127Te foram obtidas a partir da reação nuclear 126Te(n,γ)127Te, produzidas no reator IEA-R1 do IPEN/CNEN-SP. Cinco transições anteriormente atribuídas a este decaimento foram confirmadas com melhor precisão. Foi realizada também a medida da meia-vida do 127Te com incerteza significativamente menor. Utilizando um conjunto dos dados experimentais, selecionados da medida de espectroscopia gama, foi elaborada e aplicada uma proposta didática para alunos do Ensino Médio utilizando o programa Excel. / A study of the 127Te β- decay was carried out by means of gamma spectroscopy measurements using high resolution HPGe detector, in the region from 30 keV to 1.0 MeV, aiming to get a better understanding of the 127Te nuclear structure. The radioactive sources of 127Te were obtained from the 126Te(n,γ)127Te nuclear reaction produced in the IEA- R1 nuclear reactor at IPEN/CNEN-SP. Five gamma transitions previously attributed to this decay were confirmed with a better precision than previously. The half-life of 127Te was also studied resulting in data with lower uncertainty. Using a set of data selected from gamma spectroscopy measurements was developed and applied a didactic proposal for high school students using the Excel software.

Ao longo dos últimos anos é notável, de forma cada vez mais evidente, a necessidade de uma nova fonte de energia para humanidade. Uma promissora opção é através de Fusão Nuclear, onde o plasma produzido no reator pode ter energia convertida em elétrica. Portanto, conhecer características desse plasma é de suma importância para controlá-lo e entendê-lo de forma desejável. Uma das opções de diagnósticos é o chamado Espalhamento Thomson. Este é considerado o método mais confiável na determinação de importantes parâmetros do plasma, como temperatura e densidade eletrônica, podendo ainda ajudar no estudo e explicação de vários mecanismos internos. A grande vantagem reside no fato de se consistir numa medição direta e não perturbativa. Porém trata-se de um diagnóstico cuja instalação e execução é reconhecidamente complexa, limitando-o apenas a poucos laboratórios da área de fusão pelo mundo. Entre as principais dificuldades, pode-se destacar o fato de que o sinal espalhado é muito pequeno, necessitando assim de um grande aumento da potência incidente. Além disso, as condições físicas externas podem ocasionar vibrações mecânicas que, eliminá-las ou minimizá-las ao máximo, constitui um grande desafio, levando em conta a óptica muito sensível e micrometricamente precisa envolvida no sistema. O presente trabalho descreve todo processo de instalação e operação do diagnóstico de Espalhamento Thomson no tokamak TCABR e, através deste diagnóstico, trabalhamos na obtenção de resultados da temperatura eletrônica, para finalmente ser possível calcular a densidade eletrônica do plasma. / Over the last few years is remarkable, so increasingly evident the need for a new source of energy for mankind. One promising option is through nuclear fusion, where the plasma produced in the reactor can be converted into electrical energy. Therefore, knowing the characteristics of this plasma is very important to control it and understand it so desirable. One of the diagnostic options is called Thomson scattering . This is considered the most reliable method for the determination of important plasma parameters such as temperature and electron density, and may also help in the study and explanation of various internal mechanisms . The great advantage lies in the fact that they consist of a direct measurement and nonperturbative . But it is a diagnosis whose installation and execution is admittedly complex, limiting it only a few laboratories in the field of fusion for the world. Among the main difficulties, we can highlight the fact that the scattered signal is very small, thus requiring a large increase of the incident power. Moreover, the external physical conditions can cause mechanical vibrations that eliminate or minimize them as much as possible, is a great challenge, considering the optical micrometrically very sensitive and needs involved in the system. This work describes the entire process of installation and operation of Thomson scattering diagnostic in tokamak TCABR and through this diagnosis, we work on results of electron temperature, to finally be able to calculate the electron density of the plasma.

Uma técnica de projeção é usada para tratar o problema de condição inicial na teoria quântica de campos. Nesse formalismo, equações de movimento do tipo cinético são deduzidas para um conjunto restrito de variáveis dinâmicas. Estas equações podem ser submetidas a uma expansão de campo médio da qual algumas ordens são tratáveis numericamente. A ordem mais baixa corresponde à aproximação de campo médio e as ordens seguintes levam em conta as correlações dinâmicas. Este procedimento é ilustrado no contexto da teoria fi POT. 4 em 1 + 1 dimensões, incluindo a solução numérica para o caso espacialmente uniforme. / A time-dependent projection technique is used to treat the initial value problem in quantum field theory. On the basis of the general dynamics of the field, we derive equations of kinetic type for a restricted set of dynamical variables. A mean-field expansion can be written for these equations which is numerically tractable in the few lower orders. The lowest order corresponds to the mean-field approximation and higher orders add dynamic correlation effects. This procedure is applied to fi POT. 4 theory in 1 + 1 dimensions, including numerical solution for the case of a spatially uniform system.

Foi desenvolvida e testada metodologia de extração seletiva diferencial de material particulado do aerossol atmosférico, coletado em filtros de fibras de vidro, para análise elementar pelo método PIXE. Desenvolveu-se um procedimento para a correção absoluta de efeitos de autoabsorção de raios x em alvos pipetados. Amostras de material particulado foram coletadas com amestradores HiVol em São Paulo e no Rio de Janeiro. Foi determinada a composição elementar das frações do material particulado total solúveis em diclorometano, água e uma mistura de ácidos nítrico e clorídrico,1N. Os limites de detecção alcançados pela técnica de extração, pipetagem e análise PIXE foram de 5 a 30 vezes inferiores aos dos filtros Nuclepore. Foram quantificados de 10 a 14 elementos traço em compostos apolares, em concentrações tão baixas quanto 10pg/\'m POT. 3\' e 24 elementos em cada uma das frações solúvel em água e ácido. Não se pode desprezar efeitos de autoabsorção de raios x em alvos pipetados. Mesmo em alvos tão finos quanto 100\'mü\'g/c\'m POT. 2\', a concentração de elementos com Z<20 pode ser seriamente subestimada. Sugere-se sempre determinar as espessuras e coeficientes de absorção de Massa dos a l vos pelo método dos dois alvos pipetados com soluções com concentrações diferentes desenvolvido neste trabalho. Historicamente o método PIXE tem sido divulgado como permitindo a análise direta de amostras sem nenhum tratamento prévio. É hora de rever esta afirmação e aumentar a quantidade e qualidade de informação na análise elementar de uma amostra, aliando a informação química à da composição elementar. / PIXE analysis of particulated matter in glass fibre filters was done on pippeted targets, prepared with solutions of differential and selective extracts from the filters. An x ray autoabsorption correction method, based on the analysis of targets pipetted with solutions of different concentrations, was developed. São Paulo and Rio de Janeiro aerosol samples were collected on normal glass fibre filters by HiVol samplers. The elementary composition of aerosol particulated matter soluble in dichloromethane, water and a mixture of nitric and hidrochloricacid, 1N, was determinated. PIXE analysis detection limits, of the measured concentrations, where 5 to 30 times lower than the achieved by samples on Nuclepore filters. There has been quantified 10 to 14 elements in the dichloromethane fraction, and 24 in each, water and acid soluble fractions. X ray autoabsorption effects cannot be neglected, even on targets as thin as 100\'mü\'g/c\'m POT. 2\'. It is suggested to apply the developed two concentration pippeted target method, to measure target thickness and to correct data for autoabsorption. It is claimed for long time that PIXE analysis of aerosol samples is a quick and straightforward analytical method where it is not necessary to prepare samples. Reviewing this use will provide the addition of chemical information to elementary PIXE results.

A interação forte a baixas energias pode ser abordada por meio de lagrangianas efetivas. Nesse contexto, o modelo de Skyrme representa uma forma de descrever bárions, que emergem como sólitons topológicos de uma lagrangiana mesônica quiral. A interação nucleon-nucleon (NN) é comumente tratada neste modelo de maneira aproximada, através do chamado Ansatz Produto (AP), cujo problema mais sério é não reproduzir a atração de alcance intermediário no canal escalar-isoescalar do potencial NN. O objetivo deste trabalho é construir um novo ansatz para o cálculo da interação NN no modelo de Skyrme. Para isso, analisamos o AP, investigando as causas deste problema fenomenológico, e concluímos que deve-se à componente azimutal de seu campo piônico. A partir disto, construímos o Ansatz Novo (AN), com o qual calculamos o novo potencial. Comparando os resultados com outros potenciais existentes, mostramos que o AN constitui uma solução plausível para o problema. / Strong interactions at low energies can be treated by means of effective lagrangians. In this context, the Skyrme model is regarded as a way to describe baryons as topological solitons from a chiral mesonic lagrangian. In the framework of this model, nucleon-nucleon (NN) interaction is usually derived in the sudden approximation, by means of the so called Product Ansatz (PA). Its most serious problem is the absence of the intermediate range attraction in the scalar-isoscalar channel of the NN potential. We construct a new ansatz to derive the NN interaction in the Skyrme model. At first, we analise the PA and investigate the causes of its phenomenological problem. We conclude it is due to the azimuthal component of its pionic field. With this result we build the New Ansatz (NA) and calculate the new potential. Comparisons of the results with other existent potentials show that NA constitutes a plausible solution to the problem.

Publicación a texto completo no autorizada por el autor / Los suelos estudiados se encuentran en la meseta del Bombón de la Reserva Nacional de Junín, en los Andes centrales del Perú, que es una zona afectada por las actividades mineras durante varios siglos. Las técnicas analíticas utilizadas para la caracterización mineralógica son la energía dispersiva de fluorescencia de rayos X (EDXRF), difractometría de rayos X (XRD) y espectroscopia Mössbauer (MS). Con tecnicas químicas complementarias se miden el pH y la capacidad de intercambio de cationes de estos suelos; también se mide su contenido de materia orgánica. El contenido del plomo se mide por EDXRF usando un espectrómetro Amptek portátil. De acuerdo a las medidas a temperatura de ambiente los espectros Mössbauer indican que el hierro está presente en estado paramagnético y se aprecia una distribución de sitios, debido a diferentes tamaños de partículas, en la muestra M2. Las mediciones de XRD indican la presencia de minerales de silicato de aluminio tales como andesina e hidróxidos de Fe como la goethita. Por EDXRF se calcula por el porcentaje de plomo en muestras y se calcula que el plomo está presente en el rango de 0,2 a 1,4%. / Tesis

The nuclear many-body problem is nowadays being increasingly approached on the basis of a relativistic formalism. Microscopic Dirac-Brueckner-Hartree-Fock (DBHF) calculations starting from a realistic nucleon-nucleon interaction seem to be very promising. In the theory of quantum hadrodynamics, nucleons interact through the exchange of virtual mesons and the dynamics is specified by Lorentz covariant Lagrangian densities. In the simplest version, only a vector field (associated with the w meson) accounting for short-range repulsion and a scalar field ("sygma" meson) responsible for attraction are needed to describe saturation in nuclear matter. Calculations in mean field Hartree approximation, neglecting exchange terms and without including any contribution from antiparticles, give an accurate description of many of the features of nuclear systems.The success of semi-classical models in non-relativistic nuclear physics provides a very strong motivation for investigating similar methods in the relativistic context, where only the pure Thomas-Fermi approximation had been studied. In this thesis we set up the semi-classical expansion in relativistic nuclear mean field theory, including gradient corrections of order h(2) to the Thomas-Fermi model, and investigate several applications to nuclear systems.On the basis of Wigner transform techniques, a. recursive scheme to obtain the semi-classical h(2) expansion of the propagator associated with a time-independent single-particle Hamiltonian with matrix structure is presented. We focus our attention on the application of the method to a Dirac Hamiltonian related to relativistic nuclear mean field theory, i.e., including a position-dependent effective mass and the time-like component of a. four-vector field. Compared with the non-relativistic case, the procedure is considerably more complicated owing to the matrix structure of the Hamiltonian. For this reason the "h", expansion is pushed to order h(2) only. A detailed derivation is given of the h(2)-order Wigner-Kirkwood expansion of the relativistic density matrix, in terms of the gradients of the vector and the scalar field, as well as of the expansion of the particle and energy densities. The idempotency of the semi-classical density matrix to second order in "h" is proven. The Wigner-Kirkwood expressions, as they stand, are not suitable to be employed in a self-consistent problem. Therefore, we obtain the corresponding density functional results. In this case the energy densities are expressed as a functional of the local density, the effective mass and their gradients.The accuracy of the Wigner-Kirkwood series is tested on a. relativistic harmonic oscillator and perfect agreement with the Strutinsky averaged observables is found even in the highly relativistic regime. The density functional version is shown to be slightly less accurate, a feature already known in the non-relativistic case. It turns out that the semi-classical expressions represent the different quantities on average, that is, quantum fluctuations are averaged out. This model study shows that, for positive energy states, the derived semi-classical expansions contain all the relativistic ingredients, the difference with quantal results being due mainly to shell effects.Extended Thomas-Fermi calculations, which· include h(2)-order gradient corrections, are performed for relativistic non-linear "sigma"- "omega" models using two kinds of Lagrangians which differ in the form of the scalar coupling for the isoscalar sigma meson. Comparing the semi-classical results of order h(2) (TFh(2)) with the Hartree results, we find that the TFh(2) approximation yields some underbinding when the effective mass (mº) of the model is small, and some overbinding when mº is large. For a value around mº/m = 0.65, both TFh(2) and Hartree would roughly yield the same binding energy. However, since semi-classical and quantal results must differ in the so-called shell energy, this indicates that it is not properly estimated by the TFh(2) approximation.When the h(2)-order gradient corrections are taken into account (TFh(2), we have found a numerical instability in the solution of the semi-classical Klein-Gordon equation obeyed by the scalar field in the case of parameterizations which have mº/m </= 0.60, which can be eliminated if the q-meson mass mº is reduced (with the ratio g(2-0)/m(2-0) unaltered).Second-order corrections in "h" to the TFh(0) approximation improve the agreement with Hartree solutions in a sensitive way, always yielding more bound nuclei than within the Hartree approach. The sign of the h(2) corrections depends on mº, and they are found to vanish around mº/m = 0.75 for the models of the type considered here. In several respects, the semi-classical relativistic phenomenology quite resembles the one met in the non-relativistic regime using Skyrme forces, in spite of the different origin of mº in both situations. Extending the so-called expectation value method to the relativistic problem, and using the TFh(2) semi-classical mean field as a starting point, perturbative quantal solutions are found which are in good agreement with the Hartree results.The semi-classical TFh(0) and TFh(2) density distributions do not present oscillations due to the absence of shell effects, but they average the Hartree results. In the interior of the nucleus the TFh(0) and TF1i2 densities are very similar. However, in the surface and the outer region the TF1i2 densities come appreciably closer than TFh(0) to the Hartree results, due to the gradient corrections incorporated by the TF1i2 functionals, and show an exponential drop off.Liquid drop model coefficients are calculated for some parameter sets of the "sygma-omega" model. We have found reasonable results for the surface thickness and for the surface and curvature energies, which are within the range of the values obtained in non-relativistic calculations using density-dependent Skyrme forces. Therefore, the relativistic effects do not seem to avoid the disagreement of the calculated value of the curvature energy with the empirical value.In this work we also study the effects of the density-dependent Dirac spinor for the nucleons, as is determined microscopically in the DBHF approach, on various properties of the structure and scattering of finite nuclei. To enable this, we construct a relativistic energy density functional that contains the semi-classical kinetic energy density of order h(2). The effective mass and the volume term in the potential energy arise from a DBHF calculation of nuclear matter. This volume term is supplemented by some conventional correction terms and the few free parameters are suitably adjusted. It turns out that the radii of nuclei calculated with the present approach agree better with the experimental value than those obtained in similar studies using a potential energy derived from a non-relativistic G-matrix. This demonstrates that the Dirac effects improve the calculation of ground-state properties of finite nuclei also in our relativistic extended Thomas-Fermi (RETF) approximation.However, this study of ground-state properties is not the main goal of our investigation.The capabilities of our RETF functional are actually appraised in situations in which a full microscopic relativistic calculation, or even a phenomenological one, cannot be easily made, such as nuclear fission of rotating nuclei and heavy ion scattering. In these situations, the method constitutes a reliable tool. For the nuclear fission barriers, the present calculations are the first ones carried out with a relativistic model. We have shown that the model yields results comparable to the non-relativistic ones, with the conceptual-advantage of being relativistic and thus automatically incorporating the spin-orbit force. For the calculations of heavy ion elastic scattering cross sections, we have been able to improve previous results due to achieving a better description of the nuclear, densities.Let us summarize the two apparent merits which the TFh(2) approximation has over the simple TFh(0) one. On the one hand, it provides fully variational densities that go exponential to zero. On the other hand, it takes into account non-local spin-orbit and effective mass contributions up to order h(2), yielding a more reliable average value. / Se establece el desarrollo semi-clásico hasta orden h(2) en la teoría nuclear relativista de campo medio. Así, se obtienen las densidades semi-clásicas relativistas de partículas y de energía para un conjunto de fermiones sometidos a un campo escalar y a un campo vector, en las teorías de campo medio de Wigner-Kirkwood y de Thomas-Fermi, incluyendo correcciones en gradientes hasta orden h(2). El método semi-clásico se aplica a un oscilador armónico relativista. Después se utiliza en modelos T-W no lineales, para los cuales se resuelven las ecuaciones variacionales en núcleos finitos y en materia nuclear semi-infinita. Los resultados semi-clásicos son comparados con los correspondientes resultados cuánticos Hartree.Para estudiar los efectos de los espinores de Dirac para los nucleones sobre diversas propiedades de la estructura y de la dispersión de núcleos finitos, se construye un funcional de la densidad de energía relativista. El funcional contiene la densidad de energía cinética relativista de orden h(2). La masa efectiva y la parte potencial se obtienen a partir de cálculos Dirac-Brueckner de materia nuclear. Se presta especial atención al cálculo de barreras de fisión de núcleos en rotación y del potencial óptico para la dispersión de iones pesados a energías intermedias.

In single A hypernuclei, a A hyperon can occupy any orbital in the hypernucleus since it is free from the Pauli exclusion principle due to its additional quantum number strangeness. Due to the Pauli blocking effect, which suppresses the mesonic decay mode A ->N(pi) in the nuclear medium, hypernuclei larger than (5/A)He decay mainly through the nonmesonic channel, AN-> NN, where the A mass excess of 176 MeV is converted into kinetic energy of a final state of nucleons emerging above the Fermi see. This nonmesonic decay mode is assumed to proceed via the exchange of virtual mesons, and the large momentum transfer involved in the reaction leads to a mechanism that is sensitive to the short-distance behaviour of the amplitude and thus raises the possibility that the exchange of mesons heavier than the pion may play an important role. The fairly large momentum transfer also raises the hope that this reaction turns out to be insensitive to nuclear structure details and thus creates a suitable channel to investigate the weak decay mechanism.

Se presenta el desarrollo del Software WIMCIT; el cual ha sido producido tomando como base el CPC[16] (Código para Cálculo de Reactores), que realiza la simulación, automatiza las entradas numéricas y genera el modelamiento matemático en formato estándar, para el código de cálculo neutrónico CITATION [11] del reactor nuclear peruano RP-10 en 2 y 3 dimensiones para varios grupos de energía. Dicho código se encarga de hallar la solución numérica de la ecuación de transporte en su aproximación de difusión, mediante el método de diferencias finitas y muestra sus salidas para un análisis posterior con el Software WIMCIT. Finalmente se han añadido al programa desarrollado; capacidades gráficas y comunicación con el sistema operativo, los cuales permitirán un manejo robusto del proceso, una fácil interacción usuario-software, y mejoras sustanciales en la visualización de los resultados.