Baddeleyite (monoclinic-ZrO2) is an exceptionally common accessory phase in many of the mafic and ultra-mafic rocks prevalent throughout the Solar System. This study presents the first ground-truthing efforts in the development of this robust mineral into a diagnostic indicator, discrete barometer, and precise U-Pb geochronometer of shock metamorphism by combining electron backscatter diffraction and atom probe tomography to generate unique chemical and structural datasets. Microstructural analysis of variably shocked baddeleyite grains around the Sudbury impact structure (Ontario, Canada) highlights a series of crystallographic structures that can be correlated with discrete variations in formative pressure-temperature conditions. Decompression at high temperatures generates a series of interlocking reversion twinned structures, while quenching forms a quasi-amorphous matrix. These features are comparable to those observed in extra-terrestrial samples, where they can be directly linked with the severity and extent of lead loss and age resetting. This finding facilitates the application of baddeleyite as a shock indicator, barometer (>5 GPa) and chronometer in a wide range of planetary materials. This structural variability is also observable on the nanometre scale. Analysis of the most highly shocked Sudbury baddeleyite using atom probe tomography reveals planar and curvi-planar fractures, trace element enriched subgrain boundaries, and solid-state diffusion clusters. These micrometre and nanometre scale features encourage localised diffusion of lead, with whole-microtip U-Pb analyses yielding complex partially reset ages. The application of atom probe tomography allows these features to be spatially resolved on the nanometre scale, yielding highly accurate ages for protolith crystallization and impact metamorphism within a single grain. These results have significant implications for the isotopic analysis of baddeleyite-bearing planetary materials, where the mechanisms of U-Pb age resetting have until now been poorly understood.

We present here the hypothesis of a possible relationship between metal atom clusters and the formation of organic molecules in the interstellar medium and on small bodies as a possible pathway to the origin of such molecules. Two distinct stages are díscussed: a) the possible formation and presence of atom clusters in space and on the primitive Earth, and b) the synthesis of interstellar and terrestrial prebiotic organic molecules, a process in which metalclusters could be the active catalysts. The confirmatíon of these suggestions might be very important in arder to explain the presence of extra-terrestrial organic molecules in the interstellar medium, small bodies and planetary systems, and therefore would have great relevance in cosmochemistry and in the current theories about the origins of life.

O principal objetivo deste trabalho é, adotado uma abordagem centrada na simulação numérica, entender a desaceleração a laser de um feixe atômico por meio da conhecida técnica de ajuste Zeeman. Nossos cálculos numéricos são capazes de reproduzir as características fundamentais dos resultados experimentais já obtidos. Também apresentamos um modelo analítico simples incorporando as idéias básicas contidas nas hipóteses utilizadas nas simulações e mostrando que estas idéias são consistentes com as conclusões numéricas e experimentais. Isto demonstra que os aspectos essenciais do processo desacelerador são bem compreendidos. / The main purpose of this work is, adopting a numerical simulation approach, to understand the laser deceleration of an atomic beam by means 0f the kown Zeeman tuning technique. Our numerical calculations are able to reproduce the fundamental features of the experimental results already obtained. We also present a simple analytical model incorporating the basic ideas contained in the hypotheses used in the simulations, and show that these ideas are consistent with the numerical and experimental conclusions. This demonstrates that the essential aspects 0f the deceleration process are well comprehended.

Neste trabalho resultados experimentais inéditos da taxas de perdas para o sistema Cs-K em função da intensidade do laser de aprisionamento foram obtidos. A análise dos resultados foi auxiliada pelo modelo tipo Gallagher-Pritchard que demonstrou possuir uma dependência muito forte com a velocidade de escape. Um estudo complementar ajudou na determinação dos mecanismos causadores de perdas, a catálise óptica, onde o principal resultado foi a obtenção de um resultado teórico que corresponde a observação experimental para o sistema Na-Rb, onde as perdas foram associadas a atuação do estado duplamente excitado. Compreender os mecanismos causadores de perdas pode ajudar na construção de armadilhas magneto-ópticas de grande eficiência, importantes em experimentos de medidas de propriedades atômicas. / We have investigated trap loss rate as a function of trap laser intensity for the Cs-K system. A model based on Gallagher-Pritchard type considerations, allow understand the obtained results. To correctly interpret the data, we have proposed new mechanisms, which can be proven with recent experiment in Na-Rb system.

Orientador: Antonio Vidiella Barranco / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-10T14:52:42Z (GMT). No. of bitstreams: 1 Lourenco_FelipedeCampos_M.pdf: 1075719 bytes, checksum: 3053a24a405a3d715e3f7faf6455b424 (MD5) Previous issue date: 2008 / Resumo: O principal propósito dessa dissertação é estudar um novo modelo de interação entre um átomo e um modo do campo eletromagnético quantizado, assim como a sua aplicação no problema de transferência de emaranhamento entre qubits e sistemas de variáveis contínuas. Inicialmente, apresentamos uma revisão do principal modelo de interação átomo campo quantizado, conhecido como modelo de Jaynes Cummings, e também uma introdução ao emaranhamento, com o objetivo de estabelecer as medidas que serão utilizadas no restante do trabalho. Após essa parte introdutória, baseados no já conhecido modelo Raman degenerado, propomos o modelo Raman Quase degenerado com intuito de descrever a interação de um átomo de três níveis na configuração L e um modo do campo quantizado. Admitimos que o campo, no limite dispersivo, acopla os dois níveis atômicos inferiores ao estado de maior energia e este é eliminado por uma transformação unitária, ou por eliminação adiabática. Dessa forma, ele passa a desempenhar o papel de um nível virtual que possibilita a transição efetiva entre os dois estados de menor energia do átomo. Para chegarmos à forma final do Hamiltoniano efetivo, ainda supomos que a diferença de energia entre os dois níveis inferiores é muito pequena se comparada à dessintonia do nível excitado em relação à freqüência do campo interagente. A partir das equações que descrevem a dinâmica do átomo interagindo com um campo coerente, investigamos a transferência de emaranhamento de um par de átomos maximamente emaranhados para um par de cavidades preparadas inicialmente no estado puro e separável de campo coerente. Naturalmente, também consideramos a transferência no sentido contrário, campo átomo. Os resultados obtidos mostram que é possível a transferência completa nas duas situações. O último assunto abordado nessa dissertação foram os estados coerentes emaranhados do tipo cluster. Propomos um esquema para a geração desse tipo de estado entre quatro cavidades separadas espacialmente utilizando apenas um átomo e duas zonas de Ramsey e também estudamos a influência da dissipação de energia / Abstract: The main purpose of this dissertation is to study a new model to describe the interaction between an atom and a mode of the quantized electromagnetic field and also its application to the entanglement reciprocation problem between qubits and continuous variable systems. Firstly, we review the main model used to describe the atom field interaction,known as the Jaynes Cummings model, and also make an introduction to entanglement, aiming to establish the measures that will be used latter.After this introductory part and based on the known degenerate Raman model, we propose the Quasi degenerate Raman model with the intention to describe the interaction between a three level atom in the L configuration and a mode of the quantized field. We admit that the field, in the dispersive limit, couples the two lower atomic levels to the highest energy state, which is then eliminated by a unitary transformation, or by an adiabatic elimination.In this way, it plays the role of a virtual level which enables the effective transition between the other two lower energy levels. To get to the final form of the effective Hamiltonian we still assume that the energy difference between these two lower energy levels is too small when compared to the detuning of the excited level. From the equations that describe the dynamics of an atom interacting with a coherent field, we investigate the entanglement transfer from two maximally entangled atoms to two cavities initially prepared in a pure separable coherent state. Naturally, we also consider the transfer on the opposite way, field -- atom. Our results show that the complete entanglement reciprocation is possible. The last subject of this dissertation is the cluster type entangled coherent states. We propose a new scheme for the generation of this kind of state among four spatially separated cavities using only one atom and two Ramsey zones and also study the energy dissipation influence / Mestrado / Física Atômica e Molecular / Mestre em Física

Orientador: Jose de Alencar Simoni / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-06T22:12:09Z (GMT). No. of bitstreams: 1 Tasca_RodolfoAureo_M.pdf: 4202527 bytes, checksum: f02b236aebdd658311fcaa4801e2793f (MD5) Previous issue date: 2006 / Resumo: O estudo da Estrutura da Matéria e Tabela Periódica foi aplicado na antiga oitava série do ensino fundamental, hoje nona série. Este trabalho almeja que a introdução desses conceitos seja de maneira natural, sem criar expectativas ou hostilidades sobre o assunto. Sabe-se que a abstração é um fator fundamental no estudo da estrutura da matéria, e o uso de modelos adequados faz com que a introdução desses conceitos seja mais palatável. Durante os primeiros 4 meses do ano letivo de 2002, duas salas de 35 alunos, da Escola Municipal de Ensino Fundamental Maria Pavanatti Fávaro, situada no município de Campinas, foi o local escolhido para a aplicação do trabalho. As atividades aplicadas envolveram trabalhos com modelos mecânicos, interpretação e criação de modelos para o átomo, familiarização com a Tabela Periódica e jogos educativos que auxiliaram a memorização de algumas ferramentas fundamentais no ensino de química. As atividades serviram como instrumentos para a introdução dos fundamentos no estudo da estrutura da matéria e tabela periódica. Sem aprofundar nos conceitos, deu-se ênfase aos aspectos mais importantes que serão estudados no Ensino Médio, como: conhecimento sobre o átomo e suas partículas fundamentais (prótons, nêutrons e elétrons), simbologia e representação (linguagem química), formação e formulação de alguns compostos (ex: água, amônia, metano, gás carbônico, etc.), leitura e utilização da Tabela Periódica em seus aspectos mais simples. As atividades mostraram que é possível tornar o ensino da estrutura da matéria mais palatável e sem traumas, sendo o livro didático, apenas um dos instrumentos para o aluno e para o professor. Experimentos simples; usando-se argila, feijões, grãos de bico, bolinhas de gude, jogos de bingo e de cartas, mostraram-se facilitadores para o entendimento dos conceitos, de modo que, ao mesmo tempo em que o estudante está "brincando", ele também está fortalecendo seu aprendizado / Abstract: The study of the Structure of Matter and the Periodic Table which was applied at the old eighth series of basic education, presently the ninth series. The aim of this project is to introduce these concepts as naturally as possible, without creating expectations or hostilities on the subject. One knows that abstraction is a basic factor in the study of the structure of matter and the use of adjusted models, make them introduction of these concepts is compensable. During the first 4 months of the school year of 2002, two classrooms of 35 students each, at the Municipal School of Basic Education Maria Pavanatti Fávaro, situated in the city of Campinas, was the chosen place to apply this task. The applied activities had involved work such as mechanical models, interpretation and educative creation of models of the atom, familiarization with the Periodic Table and games that had assisted the memorization of some basic tools in chemistry education. The activities had served as instruments for the introduction of the beddings in the study of the structure of substances and the periodic table. Without profound elaboration of the concepts, the most important aspects for the Average high-school education were emphasized, such as: knowledge of the basic atom and its particles (protons, neutrons and electrons), symbols and representation (chemical language), formation and formularization of some composites (former: water, ammonia, methane, carbonic gas, etc.), reading and use of the Periodic Table in its simpler aspects. The activities showed that it is possible to make the education of the structure of the matter more compensable and without that he is traumatic, being the text book, but one of the instruments for the pupil and the professor. Simple experiments; using clay, beans, grains of peak, marbles, bingo games and letters, have revealed to be facilitators of understanding of the concepts, so that, while the student is "playing", he is also strengthening his learning processes / Mestrado / Físico-Química / Mestre em Química

Optoelectronic devices fabricated from nitride semiconductors include blue and green light emitting diodes (LEDs) and laser diodes (LDs). To design efficient devices, the structure and composition of the constituent materials must be well-characterised. Traditional microscopy techniques used to examine nitride semiconductors include transmission electron microscopy (TEM), and atomic force microscopy (AFM). This thesis describes the study of nitride semiconductor materials using these traditional methods, as well as atom probe tomography (APT), a technique more usually applied to metals that provides three-dimensional (3D) compositional information at the atomic scale. By using both APT and correlative microscopy techniques, a more complete understanding of the material can be gained, which can potentially lead to higher-efficiency, longer-lasting devices. Defects, such as threading dislocations (TDs), can harm device performance. An AFM-based technique was used to show that TDs affect the local electrical properties of nitride materials. To investigate any compositional changes around the TD, APT studies of TDs were attempted, and evidence for oxygen enrichment near the TD was observed. The dopant level in nitride devices also affects their optoelectronic properties, and the combination of APT and TEM was used to show that Mg dopants were preferentially incorporated into pyramidal inversion domains, with a Mg content two orders of magnitude above the background level. Much debate has been focused on the microstructural origin of charge carrier localisation in InGaN. Alloy inhomogeneities have often been suggested to provide this localisation, yet APT has revealed InGaN quantum wells to be a statistically random alloy. Electron beam irradiation in the TEM caused damage to the InGaN, however, and a statistically significant deviation from a random alloy distribution was then observed by APT. The alloy homogeneity of InAlN was also studied, and this alloy system provided a unique opportunity to study gallium implantation damage to the APT sample caused during sample preparation by the focused ion beam (FIB). The combination of APT with traditional microscopy techniques made it possible to achieve a thorough understanding of a wide variety of nitride semiconductor materials.

The transportation industries are constantly striving to achieve minimum weight to cut fuel consumption and improve overall performance. Different innovative design strategies have been placed and directed toward weight saving combined with good mechanical behavior. Among different materials, aluminum-based alloys play a key role in modern engineering and are widely used in construction components because of their light weight and superior mechanical properties. Introduction of different nano-structure features can improve the service and the physical properties of such alloys. For intelligent microstructure design in the complex Al-based alloy, it is important to gain a deep physical understanding of the correlation between the microstructure and macroscopic properties, and thus atom probe tomography with its exceptional capabilities of spatially resolution and quantitative chemical analyses is presented as a sophisticated analytical tool to elucidate the underlying process of precipitation phenomena in aluminum alloys. A complete study examining the influence of common industrial heat treatment on the precipitation kinetics and phase transformations of complex aluminum alloy is performed. The qualitative evaluation results of the precipitation kinetics and phase transformation as functions of the heat treatment conditions are translated to engineer a complex aluminum alloy. The study demonstrates the ability to construct a robust microstructure with an excellent hardness behavior by applying a low-energy-consumption, cost-effective method. The proposed strategy to engineer complex aluminum alloys is based on both mechanical strategy and intelligent microstructural design. An intelligent microstructural design requires an investigation of the different strengthen phases, such as T1 (Al2CuLi), θ′(Al2Cu), β′(Al3Zr) and δ′(Al3Li). Therefore, the early stage of phase decomposition is examined in different binary Al-Li and Al-Cu alloys together with different ternary Al-Li-Cu alloys. Atom probe tomography and statistical testing are combined to investigate the fine scale segregation effects of dilute solutes in aluminum alloys. The optimum application of atom probe tomography in a wide range of materials is enabled by the integration of a laser pulse mode in the atom probe analysis. However, the nature of the laser mechanism used during atom probe tomography analyses is still debated. Systematic investigation of the microstructural change of δ′(Al3Li) precipitates influenced by different pulsed laser energies are used to describe the important phenome associated with the laser pulse mode. In this study, atom probe tomography presented a series of snapshots during in-situ reversion of δ′(Al3Li) precipitates, initiated by laser irradiation, using different laser energies for the first time. An estimation method to investigate real sample temperatures during laser-APT analyses using an interface reaction itself as a probe has been proposed. Finally, the considerable potential of aluminum liquid is demonstrated as a powerful synthesis solvent of important intermetallic phases such as: Mg2Si, Al2Mg and CaMgSi. The atom probe tomography technique is utilized to characterize the intermediate reaction steps of the flux-grown intermetallic phases. The study proposed a direct approach to investigate the involved reactions during the formation of the synthesized intermetallic phase.

After a detailed discussion of the variation theorem for upper bound calculation of eigenvalues, many standard procedures for determining lower bounds to eigenvalues are presented with chemical applications in mind. A new lower bound method, arbitrary choice without trunctation is presented and tested on the helium atom. This method is attractive because it does not require knowledge of the eigenvalues or eigenvectors of the base problem. In application, however, it is shown that the method is disappointing for two reasons: 1) the method does not guarantee improved bounds as calculational effort is increased; and 2) the method requires some a priori information which, in general, may not be available. A possible direction for future work is pointed out in the end. An extension of a lower bound method by Calogero and Marchioro has been developed and is presented in appendix G along with comments on the effective field method in appendix H for Virginia Tech access only. / Ph. D. / To avoid copyright infringements, access to these three appendices (G, H, and I) has been permanently limited to the Virginia Tech campus. In the case that Virginia Tech places these appendices freely on the internet, Virginia Tech is solely responsible for copyright violations.

The adrenal medulla is the inner part of adrenal glands located above each kidney, that produces catecholamines. Neuroblastoma and pheochromocytoma are the most prevalent malignancies of the adrenal medulla. Quantitative diagnosis of urinary catecholamines using HPLC-coupled Mass detectors is the current method for the diagnosis of neuroblastoma and pheochromocytoma. There are two major problems with this approach, (i) Because the catecholamines concentrations have short half-life (10-100 s), a series of urine tests must be performed throughout 24hr, detecting each catecholamine separately, is inconvenient and time-consuming; (ii) mass detectors are expensive, bulky, and require highly skilled personal. Vanillylmandelic (VMA), and homavanillic acid (HVA) are the by-products of catecholamines and are emerging alternative biomarker for catecholamines due to their high stability. Here, we developed a rapid, sensitive, miniaturized, and cheaper sensing platform for simultaneous quantifications of dopamine (DA), VMA, and HVA, with the aid of iron single-atom catalysts (Fe-SACs), based electrochemical sensor. SACs are atomically distributed metal atoms that have a maximum atomic utility rate of nearly 100%, compared to 30% for traditional metal nanoparticles. MXene sheets are employed to stabilize Fe-SACs, where, the exposed lone pairs of MXene serve as sites covalently linking high-energy single Fe atoms. MXene/Fe-SACs were synthesized by treating Ti3C2TxMXene with Iron chloride via freeze-drying followed by annealing. The successful formation of the material was verified by state-of-the-art characterizations. The MXene/Fe-SACs show superior electrocatalytic performance to the commonly used Fe- nanomaterials. Then, it was coated on the electrode surface and used to analyze DA, VMA, and HVA simultaneously via cyclic voltammetry (CV) and square-wave voltammetry (SWV). Under optimized conditions, the MXene/Fe-SACs electrochemical sensor showed detection limits as low as 1 nM and a linear range between 1 nM-100 μM for DA, LOD of 5 nM & linear range of 10 nM-100 μM VMA, and LOD of 10 nM & linear range of 20 nM-100 μM HAV. The method proved successful in detecting biomarkers in (spiked) synthetic urine and human serum. Furthermore, the method was successfully demonstrated in the determination of DA release from PC12 live cells, suggesting the wide practical use of SACs in sensing catecholamines-related metabolites.