Através de um hamiltoniano efetivo baseado no tratamento de NAMBU POT.90 para o BCS, no qual incluímos além do emparelhamento monopolar o emparelhamento quadrupolar, discutimos a relação entre esse modelo e o modelo de bósons interagentes. Uma aplicação e feita a cadeia o (6) do IBM, que corresponde ao limite GAMA-instável do modelo de bohr. As dificuldades encontradas e uma possível generalização para o modelo são discutidas. / The nambu mechanism for BCS theory is extended with inclusion of quadrupole pairing in adition to the usual monopole pairing. An effective Hamiltonian is constructed and its relation to the IBM is discussed. We discussed the faced difficulties and a possible generalization of the model.

La compréhension usuelle de l'appariement proton-neutron, dont les traces sont actuellement étudiées en noyaux N = Z, s'appuie sur le mécanisme de paires de Cooper et modèles BCS type. Dans cette thèse, nous présentons une approche alternative qui, contrairement aux modèles BCS, conserve exactement le nombre de particules et l'isospin. Dans cette approche, l'état fondamental de noyaux N = Z est décrit comme un condensé de quartets alpha-similaires faits de deux neutrons et deux protons couplés à l'isospin total T = 0 et de spin J total = 0. La comparaison avec des calculs exacts du modèle en couches montre que le modèle de condensation quartet (QCM) donne une description très précise de l'appariement des corrélations à noyaux N = Z, bien mieux que les modèles BCS. Il est également montré que l'appariement proton-neutron et alpha de type condensation sont importantes non seulement pour les noyaux N = Z, mais aussi pour les noyaux avec des neutrons excédentaires. Dans ce dernier cas, le condensat de quartets d'alpha coexiste avec le condensat des paires de neutrons en excès par rapport au isotopes N = Z. En utilisant le cadre de QCM, nous avons également étudié la compétition entre l’appariement proton-neutron isovectoriel et isoscalaire dans les noyaux N = Z. Nos résultats indiquent que la contribution de l'appariement isoscalaire aux corrélations d'appariement du fondamental est très faible par rapport à l'appariement isovectoriel. / The common understanding of proton-neutron pairing, whose fingerprints are currently investigated in N = Z nuclei, relies on Cooper pair mechanism and BCS-type models. In the present thesis we present an alternative approach which, contrary to BCS models, conserves exactly the particle number and the isospin. In this approach the ground state of N=Z nuclei is described as a condensate of alpha-like quartets built by two neutrons and two protons coupled to the total isospin T=0 and total spin J=0. The comparison with exact shell model calculations shows that the quartet condensation model (QCM) gives a very accurate description of pairing correlations in N=Z nuclei, much better than the BCS models. It is also shown that proton-neutron pairing and alpha-type condensation are important not only for N=Z nuclei but also for nuclei with excess neutrons. In the latter case the condensate of alpha-like quartets coexist with the condensate of the neutron pairs in excess relative to the N=Z isotope. Using the framework of QCM we have also studied the competition between the isovector and the isoscalar proton-neutron pairing in nuclei with N=Z. Our results indicate that the contribution of isoscalar pairing to the ground state pairing correlations is very small compared to the isovector pairing.

Através de um hamiltoniano efetivo baseado no tratamento de NAMBU POT.90 para o BCS, no qual incluímos além do emparelhamento monopolar o emparelhamento quadrupolar, discutimos a relação entre esse modelo e o modelo de bósons interagentes. Uma aplicação e feita a cadeia o (6) do IBM, que corresponde ao limite GAMA-instável do modelo de bohr. As dificuldades encontradas e uma possível generalização para o modelo são discutidas. / The nambu mechanism for BCS theory is extended with inclusion of quadrupole pairing in adition to the usual monopole pairing. An effective Hamiltonian is constructed and its relation to the IBM is discussed. We discussed the faced difficulties and a possible generalization of the model.

Universiẗat, Diss., 2004--München.

The superconducting order parameter and the mass renormalization function can be solved either at discrete frequencies along the imaginary axis, or as a function of continuous real frequencies. The latter is done with a method called analytic continuation. The analytic continuation can conveniently be done by approximating a power series to the functions, the Padè approximation. Studied in this project is the difference between the Padè approximation, and a formally exact analytic continuation of the functions. As it turns out, the Padè approximant is applicable to calculate the superconducting order parameter at temperatures sufficiently below the critical temperature. However close to the critical temperature the approximation fails, while the solution presented in this report remains reliable.

Tierärztl. Hochsch., Diss., 2004--Hannover.

Made available in DSpace on 2014-06-12T17:35:06Z (GMT). No. of bitstreams: 2 arquivo2618_1.pdf: 1509487 bytes, checksum: 98b5eb9a92e118589440106f31669bed (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2011 / Esta dissertação apresenta uma aplicação do estudo da confiabilidade em dados de tempo de vida de poços produtores de óleo de completação seca equipados com bombeio centrífugo submerso. A variável resposta do estudo é o tempo de funcionamento do poço dentro de sua normalidade até apresentar a primeira falha relacionada ao equipamento de subsuperfície, que cause uma parada total no funcionamento do poço. O principal objetivo do estudo foi, com base em um conjunto de dados reais fornecidos pela companhia petrolífera, mensurar e verificar a viabilidade técnica e econômica de um sistema de manutenção programado baseado na política de substituição por idade. Também foi realizada estratificação dos dados visando a verificar a correlação de alguns fatores como localização do campo, razão água-óleo (RAO), faixa de vazão e motivo da falha no tempo de operações dos poços. Neste trabalho, foi feito um estudo retrospectivo com uma amostra composta por 330 eventos de poços-colunas que estavam em funcionamento no período de 1992 a 2010. A modelagem probabilística dos dados foi feita através do ajuste do modelo de regressão Weibull. Os resultados encontrados na aplicação do modelo foram considerados satisfatórios, gerando economias em relação ao regime antigo entre 8% e 13% e em valores monetários anuais bastante significativos para o campo de petróleo estudado

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第20913号 / 理博第4365号 / 新制||理||1626(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 永江 知文, 教授 鶴 剛, 教授 中家 剛 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

Clostridium beijerinckii is a spore-forming, obligate anaerobe that is capable of producing butanol, acetone and isopropanol. These industrial chemicals are traditionally known as solvents. The regulation of solventogenic fermentation is linked to the onset of sporulation, so that by the time the organism begins to produce solvents, it is also entering into spore formation and metabolic slowdown. The goal of this research project was to study the effect of placing the solvent-production genes from C. beijerinckii under the control of constitutive promoters from other genes, in an attempt to allow an earlier start of butanol production during the growth phase than is the case with the wild-type cells. The aldehyde dehydrogenase from C. beijerinckii NRRL B593 (ald) and alcohol dehydrogenase from C. beijerinckii NRRL B592 (adhA) were placed under the control of the promoter from the acid-producing operon (the BCS operon) in one vector, and under the control of the promoter from the ferredoxin gene in another. In both cases, aldehyde dehydrogenase activity was produced earlier in the growth phase in transformed cells, but alcohol dehydrogenase activity was not. The adhA gene from C. beijerinckii NRRL B592 was paired with the adhB gene from the same organism in a third vector, both under the control of the promoter from the BCS operon. In cells transformed with this vector, alcohol dehydrogenase activity was observed earlier in the growth phase than it was in wild-type NRRL B592 cells. / Ph. D.

This thesis focuses on the analysis of Bardeen-Cooper-Schrieffer (BCS) to Bose-Einstein condensation (BEC) evolution in ultracold superfluid Fermi gases when the interaction between atoms is varied. The tuning of attractive interactions permits the ground state of the system to evolve from a weak fermion attraction BCS limit of loosely bound and largely overlapping Cooper pairs to a strong fermion attraction limit of tightly bound small bosonic molecules which undergo BEC. This evolution is accompanied by anomalous behavior of many superfluid properties, and reveals several quantum phase transitions. This thesis has two parts: In the first part, I analyze zero and nonzero orbital angular momentum pairing effects, and show that a quantum phase transition occurs for nonzero angular momentum pairing, unlike the $s$-wave case where the BCS to BEC evolution is just a crossover. In the second part, I analyze two-species fermion mixtures with mass and population imbalance in continuum, trap and lattice models. In contrast with the crossover physics found in the mass and population balanced mixtures, I demonstrate the existence of phase transitions between normal and superfluid phases, as well as phase separation between superfluid (paired) and normal (excess) fermions in imbalanced mixtures as a function of scattering parameter and mass and population imbalance.