Thesis (Ph.D.) - University of Queensland, 2005. / Includes bibliography.

Thesis (Ph.D.)--University of Nebraska-Lincoln, 2007. / Title from title screen (site viewed July 9, 2007). PDF text: xiii, 164 p. : ill. UMI publication number: AAT 3252443. Includes bibliographical references. Also available in microfilm and microfiche formats.

Orientador: João Manuel Marques Cordeiro / Banca: Rafael Zadorosny / Banca: Haroldo Naoyuki Nagashima / Banca: Kaline Rabelo Coutinho / Banca: Maria Elena Martín Navarro / Resumo: Trabalhos experimentais e teóricos desenvolvidos nos últimos anos evidenciaram a capacidade de alcoóis e polialcoóis em mudar características energéticas em proteínas. No entanto, o mecanismo responsável por esse efeito não está totalmente elucidado. Tomando como exemplo o dipeptídeo de alanina, foram realizadas simulações QM/MM em água, etanol e mistura 60-40% em volume de água-etanol. A molécula de dipeptídeo foi descrita em nível de cálculo quântico MP2/aug-cc-pVDZ. Em solução, apenas confórmeros aR e PPII foram encontrados na população de equilíbrio. A diferença de energia livre em solução aR ? PPII é determinada pelo balanço entre energia interna do soluto e energia de interação. Para o dipeptídeo de alanina, qualquer fator que aumente a energia de interação soluto- solvente favorece o aumento da população de aR. Por outro lado fatores que diminuam esse valor, como a adição de etanol, aumentam a população de PPII. Os resultados indicam solvatação preferencial para o sistema, evidenciado pela formação majoritária da primeira camada de solvatação por moléculas de água (na mistura), embora seja possível encontrar moléculas de etanol em pequenas quantidades ao redor do grupo carboxílico da extremidade N-terminal e, cadeias metílicas laterais. Todavia, o comportamento parece não afetar a diferença na estabilidade de equilíbrio conformacional / Abstract: Recent papers, both experimental and theoretical, have highlighted the capacity of alcohols and polyalcohol in modifying the energy landscape in proteins. However, the mechanism underlying this effect is not fully elucidated. Taking as a model-system the alanine dipeptide, QM/MM calculations were performed in water, ethanol and solution 60-40% (volume) water-ethanol. The dipeptide molecule was described by MP2/aug-cc-pVDZ level. In solution, only aR and PPII conformers were found in the conformational equilibrium population. The free energy difference in solution aR ? PPII is determined by the interplay between internal energy and the interaction energy. It has been found that, for alanine dipeptide, any factor that increases the solute-solvent interaction energy also promotes an increasing on aR stability, moreover factors that decreases this value, such as the addition of ethanol molecules, increases the PPII stability. The results points to a preferential solvation behavior for the system, as evidenced by the composition of the first solvation shell in the mixture mainly populated by water molecules, although it is possible to find small concentration of ethanol molecules around the carboxyl group of the N-terminal end and around methylic side chains. However, this behavior does not seem to affect the differential conformational stability / Doutor

We undertake a study of the classical regime in which Planck's constant and Newton's gravitational constant are negligible, but not their ratio, the Planck mass, in hopes that this could possibly lead to testable quantum gravity (QG) effects in a classical regime. In this quest for QG phenomenology we consider modifications of the standard dispersion relation of a free particle known as deformed special relativity (DSR). We try to geometrize DSR to find the geometric origin of the spacetime and momentum space. In particular, we adopt the framework of Hamilton geometry which is set up on phase space, as the cotangent bundle of configuration space in order to derive a purely phase space formulation of DSR. This is necessary when one wants to understand potential links of DSR with modifications of quantum mechanics such as Generalised Uncertainty Principles. It is subsequently observed that space-time and momentum space emerge naturally as curved and intertwined spaces. In conclusion we mention examples and applications of this framework as well as potential future developments.

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In studying the diamagnetism of free electrons in a uniform magnetic field it was found that reducing the field to zero in the wavefunction did not yield the experimentally indicated free particle plane wave wavefunction. However, solving the Schroedinger Equation resulting from setting the field equal to zero in the original equation did yield a plane wave wavefunction. This paradox was not found to be peculiar to the case of a charged particle in a uniform magnetic field but was found to occur in a number of other systems. In order to gain an understanding of this unexpected behavior, the following systems were analyzed: the one-dimensional square well potential; a charged, spinless particle in a Coulomb field and in a uniform electric field; a one-dimensional harmonic oscillator; and a charged, spinless particle in a uniform magnetic field. From these studies the following were obtained: conditions for determining the result of reducing the potential in a wavefunction; the condition under which the potential of a system may be switched off while maintaining the energy of the system constant; the relationship between the result of physically switching off a potential, the result of reducing it in the wavefunction, and the solution of the Schroedinger Equation obtained by decreasing the potential to zero in the original wave equation; and a general property of any wavefunction with respect to reducing any parameter within this wavefunction. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Orientador: Aguinaldo Robinson Souza / Banca: Marcelo Giordan Santos / Banca: Wilson Massashiro Yonezawa / Banca: Marcelo Maia Cirino / Banca: Sandra Regina Teodoro Gatti / Resumo: Os conceitos referentes à mecânica quântica são de suma importância para o estudo da estrutura do átomo, possuindo grande relevância para a Química, que tem por base o estudo da matéria e de seus constituintes. A investigação desses conceitos e de como eles são estruturados pelo estudante de Química têm adquirido relevância nas pesquisas de ensino de Química, sobretudo pelas dificuldades de aprendizagem dos entes submicroscópicos em relação aos macroscópicos concernentes à mecânica clássica. Esta pesquisa buscou analisar como ocorreu a produção de significados dos estudantes de Química no estudo dos conceitos derivados do modelo atômico atual, em especial os números quânticos, formas dos orbitais e transições eletrônicas, observando os níveis de domínio e apropriação destes. A investigação foi realizada durante uma sequência didática organizada por uma entrevista efetuada com o professor responsável pela disciplina de Química Geral II da Universidade Federal do Maranhão, onde a pesquisa ocorreu. Para a coleta de dados, utilizou-se a captura de tela, imagem e áudio dos alunos, por meio do software Camtasia®, além de gravações de áudios, entrevistas semiestruturadas, exercícios e os registros de conversas de um grupo criado na rede social WhatsApp®.A estruturação dos dados teve por base o modelo topológico de ensino, que permitiu orientar as análises. A análise ocorreu a partir da interação dos alunos e o modo como produziram os significados dos conceitos, sendo dividida em trê... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The concepts related to Quantum Mechanics are important for the study of atomic structure, having great relevance to Chemistry, which is based on the study of matter and its constituents. The investigation of how students learned these concepts has gained importance in the scientific literature, and many studies are directed about the difficulties related to the obstacle concerning the submicroscopic world and Classical Mechanics. This research aimed to analyze how production of meanings of Chemistry students in the study of concepts derived from current atomic model, especially the quantum numbers, shapes of orbitals and electronic transitions, observing levels of mastery and appropriation of it. The study was carried out during a teaching sequence organized on an interview conducted with the teacher of General Chemistry II of the Federal University of Maranhão, where the research took place. For data collection, screen capture, image and voice of the students through the Camtasia® software, and audio recordings, semi-structured interviews, exercises and conversations recorded in a group created on WhatsApp®, a social network . Data organization was based on the topological model of teaching that guided the process. The analysis occurred by the interaction of students and how they produced the meanings of concepts, being divided into three stages: classes map, categories map and microanalysis. We identified concepts produced by free associations of the previous classes and f... (Complete abstract click electronic access below) / Doutor

The Standard Model (SM) of particle physics offers the most complete quantum description of the known universe to date, however is unable to address some still unanswered questions. Supersymmetry (SUSY) is a theory which proposes partner particles for all SM particles and offers explanations for many of these questions. Many SUSY searches performed rely on signatures of high missing transverse energy due to a heavy SUSY particle escaping the detector, however these searches have not yet yielded positive results and therefore new search strategies must be employed. In this analysis, a search for new physics is performed at the CERN LHC which targets signatures of SUSY. Specifically, a search for Stealth SUSY is performed, based on a sample of proton-proton collisions at √s = 8 TeV corresponding to 19.7 fb⁻¹ of integrated luminosity collected with the CMS detector in 2012. Stealth SUSY is a unique brand of SUSY which conserves R-Parity and naturally produces a low amount of missing transverse energy. The search strategy utilized is sen- sitive to a wide variety of new physics models including compressed spectra and long decay chains. The Stealth SUSY final state topology considered in this analysis consists of two photons, many jets and low missing transverse energy. The results of this data-driven search for new physics are reported, and good agreement is observed with the background expectation. The data are thus used to determine limits on squark/gaugino masses in the Stealth SUSY framework. / A Dissertation submitted to the Department of Physics in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Spring Semester, 2015. / April 3, 2015. / CMS, High Energy Physics, LHC, Particles, Stealth SUSY, Supersymmetry / Includes bibliographical references. / Andrew Askew, Professor Directing Thesis; P. Bryant Chase, University Representative; Todd Adams, Committee Member; Joseph Owens, Committee Member; Vladimir Dobrosavljevic, Committee Member.

In this dissertation, covariant density functional theory has been applied to a variety of nuclear phenomena in the ground and excited states of rotating and non-rotating nuclei. It has been applied for the interpretation of excited superdeformed bands in 154Dy using the effective alignmentmethods. The properties of the predicted hyperdeformed nuclei at high spin in the Z = 40−58 region were investigated and the spins at which such configuration become yrast were defined. The moments of inertia, the role of single-particle energies and necking degree of freedom have also been studied. It also predicted that 107Cd is the best nucleus for its observation. The impact of time-odd mean fields (nuclear magnetism NM) in both non-rotating and rotating frame works, on physical observables has been studied. It is shown that nuclear magnetism always provide additional binding to the binding energies of odd-mass nuclei. Time-odd mean fields affect odd-even mass differences. However, the modifications of the strength of pairing correlations required to compensate for their effects are modest. In contrast, time-odd mean fields have a profound effect on the properties of odd-proton nuclei in the vicinity of the proton drip line. Their presence can modify the half-lives of proton emitters and considerably affect the possibilities of their experimental observation. They also have a profound effect on the dynamic and kinematic moments of inertia, particle number, configuration, and rotational frequency dependencies of their impact on the moments of inertia. The effect of NM on the binding energy and moments of inertia weakly depend on the choice of the RMF parametrization. Fission barriers are studied systematically with the allowence for triaxial deformations, in the actinide and superheavy regions. It is shown that covariant density functional theory is able to describe fission barriers, in actinides, on a level of accuracy comparable with nonrelativistic calculations. Triaxiality in the region of the first saddle plays a crucial role in achieving that. However, in the Z = 112 - 120 superheavy nuclei, the inner fission barriers are not affected by triaxiality. General trends of the evolution of inner fission heights are discussed.