Nesta dissertação são estudados Condensados de Bose-Einstein de átomos com pseudo-spin 1/2 cuja dinâmica orbital está acoplada a estes dois níveis de energia internos. A geração de tal sistema é possível induzindo transições entre os subníveis m_f = -1 e m_f = 0 do estado hiperfino atômico f = 1 usando um arranjo de lasers, os quais também introduzem junto uma dependência espacial dada por suas fases, as quais estão relacionadas a posição do átomo no campo, levando assim à interação acoplando spin e órbita. É considerado então um sistema unidimensional efetivo na mesma direção do acoplamento dos lasers, onde são estudado diferentes observáveis do estado fundamental, para uma varredura dos parâmetros presentes na equação, dando origem a três fases diferenciadas pela distribuição do momento. Foram determinadas estas fases do estado fundamental para interação atrativa, sendo elas modulada(striped), onda plana e de momento nulo, mostrando a localização onde cada uma ocorre no domínio de parâmetros da equação, através de diagramas de fase. São também mostrados, separadamente, observáveis relevantes como momento e desbalanço entre os estados internos nestas transições, os quais apresentaram variações bruscas, ditando valores críticos nos parâmetros, onde ocorrem. Posteriormente é estudado a dinâmica através de soluções do tipo sóliton, as quais não se propagam linearmente e são ditadas por oscilações do centro de massa e das populações, explorando diferentes situações iniciais. / In the present dissertation it has been studied Bose-Einstein Condensation of atoms with 1/2 pseudo-spin whose the orbital dynamics is coupled to these two internal energy levels. The generation of such a system is done by inducing transitions between the sub-levels m_f = -1 and m_f = 0 from the hyperfine atomic state f = 1 using an arrangement of lasers, that also introduce a spacial dependence due to their phases, that changes accordingly the atom\'s position in the light field, conducting in this way to a interaction that couples orbital motion with spin. It is then considered an effective one dimensional system in the same direction of the laser coupling, where it has been studied different ground state observables, making a sweeping in the equation parameters, showing three typical phases based on momentum distribution. So far, it was determined these phases for attractive interactions, named striped, plane wave and zero momentum, determining as well the location where each one occurs in the equation\'s parameters through a phase diagram. It is also reported, separately, a few relevant observables as individual momentum of each population and the unbalance between the internal spin states, in the transition among these phases, whose the values present abrupt variations, dictating critical values for the parameters, where it occurs. Lately is presented a dynamical study with soliton like solutions, that do not linearly propagate and instead, shows a center of mass and unbalance oscillation, probing different initial conditions.

Signalverarbeitung im Nervensystem hängt sowohl von der Netzwerkstruktur, als auch den zellulären Eigenschaften der Nervenzellen ab. In dieser Abhandlung werden zwei zelluläre Eigenschaften im Hinblick auf ihre funktionellen Anpassungsmöglichkeiten untersucht: Es wird gezeigt, dass neuronale Morphologie die Signalweiterleitung unter Berücksichtigung energetischer Beschränkungen verstärken kann, und dass selbst kleine Änderungen in biophysikalischen Parametern die Aktivierungsbifurkation in Nervenzellen, und damit deren Informationskodierung, wechseln können. Im ersten Teil dieser Abhandlung wird, unter Verwendung von mathematischen Modellen und Daten, die Hypothese aufgestellt, dass Energie-effiziente Signalweiterleitung als starker Evolutionsdruck für unterschiedliche Zellkörperlagen bei Nervenzellen wirkt. Um Energie zu sparen, kann die Signalweiterleitung vom Dendrit zum Axon verstärkt werden, indem relativ kleine Zellkörper zwischen Dendrit und Axon eingebaut werden, während relativ große Zellkörper besser ausgelagert werden. Im zweiten Teil wird gezeigt, dass biophysikalische Parameter, wie Temperatur, Membranwiderstand oder Kapazität, den Feuermechanismus des Neurons ändern, und damit gleichfalls Aktionspotential-basierte Informationsverarbeitung. Diese Arbeit identifiziert die sogenannte "saddle-node-loop" (Sattel-Knoten-Schlaufe) Bifurkation als den Übergang, der besonders drastische funktionale Auswirkungen hat. Neben der Änderung neuronaler Filtereigenschaften sowie der Ankopplung an Stimuli, führt die "saddle-node-loop" Bifurkation zu einer Erhöhung der Netzwerk-Synchronisation, was möglicherweise für das Auslösen von Anfällen durch Temperatur, wie bei Fieberkrämpfen, interessant sein könnte. / Signal processing in nervous systems is shaped by the connectome as well as the cellular properties of nerve cells. In this thesis, two cellular properties are investigated with respect to the functional adaptations they provide: It is shown that neuronal morphology can improve signal transmission under energetic constraints, and that even small changes in biophysical parameters can switch spike generation, and thus information encoding. In the first project of the thesis, mathematical modeling and data are deployed to suggest energy-efficient signaling as a major evolutionary pressure behind morphological adaptations of cell body location: In order to save energy, the electrical signal transmission from dendrite to axon can be enhanced if a relatively small cell body is located between dendrite and axon, while a relatively large cell body should be externalized. In the second project, it is shown that biophysical parameters, such as temperature, membrane leak or capacitance, can transform neuronal excitability (i.e., the spike onset bifurcation) and, with that, spike-based information processing. This thesis identifies the so-called saddle-node-loop bifurcation as the transition with particularly drastic functional implications. Besides altering neuronal filters and stimulus locking, the saddle-node-loop bifurcation leads to an increase in network synchronization, which may potentially be relevant for the initiation of seizures in response to increased temperature, such as during fever cramps.

Nesta dissertação são estudados Condensados de Bose-Einstein de átomos com pseudo-spin 1/2 cuja dinâmica orbital está acoplada a estes dois níveis de energia internos. A geração de tal sistema é possível induzindo transições entre os subníveis m_f = -1 e m_f = 0 do estado hiperfino atômico f = 1 usando um arranjo de lasers, os quais também introduzem junto uma dependência espacial dada por suas fases, as quais estão relacionadas a posição do átomo no campo, levando assim à interação acoplando spin e órbita. É considerado então um sistema unidimensional efetivo na mesma direção do acoplamento dos lasers, onde são estudado diferentes observáveis do estado fundamental, para uma varredura dos parâmetros presentes na equação, dando origem a três fases diferenciadas pela distribuição do momento. Foram determinadas estas fases do estado fundamental para interação atrativa, sendo elas modulada(striped), onda plana e de momento nulo, mostrando a localização onde cada uma ocorre no domínio de parâmetros da equação, através de diagramas de fase. São também mostrados, separadamente, observáveis relevantes como momento e desbalanço entre os estados internos nestas transições, os quais apresentaram variações bruscas, ditando valores críticos nos parâmetros, onde ocorrem. Posteriormente é estudado a dinâmica através de soluções do tipo sóliton, as quais não se propagam linearmente e são ditadas por oscilações do centro de massa e das populações, explorando diferentes situações iniciais. / In the present dissertation it has been studied Bose-Einstein Condensation of atoms with 1/2 pseudo-spin whose the orbital dynamics is coupled to these two internal energy levels. The generation of such a system is done by inducing transitions between the sub-levels m_f = -1 and m_f = 0 from the hyperfine atomic state f = 1 using an arrangement of lasers, that also introduce a spacial dependence due to their phases, that changes accordingly the atom\'s position in the light field, conducting in this way to a interaction that couples orbital motion with spin. It is then considered an effective one dimensional system in the same direction of the laser coupling, where it has been studied different ground state observables, making a sweeping in the equation parameters, showing three typical phases based on momentum distribution. So far, it was determined these phases for attractive interactions, named striped, plane wave and zero momentum, determining as well the location where each one occurs in the equation\'s parameters through a phase diagram. It is also reported, separately, a few relevant observables as individual momentum of each population and the unbalance between the internal spin states, in the transition among these phases, whose the values present abrupt variations, dictating critical values for the parameters, where it occurs. Lately is presented a dynamical study with soliton like solutions, that do not linearly propagate and instead, shows a center of mass and unbalance oscillation, probing different initial conditions.

Retrusão do terço médio da face é característica das disostoses sindrômicas. Falta de projeção e deficiência estrutural podem ser responsáveis pelo fenômeno, mas estes nunca foram avaliados adequadamente tridimensionalmente. O objetivo deste estudo é analisar a interface entre a base do crânio e a face, o volume dos ossos do terço médio da face e o volume e estrutura dos componentes da órbita, para fornecer uma compreensão da etiopatogenia da deficiência do terço médio da face e da dismorfologia ocular. Crianças com tomografia computadorizada, na ausência de qualquer intervenção cirúrgica, foram incluídas. As informações demográficas foram obtidas para três grupos (Apert, Crouzon, Controle). As tomografias computadorizadas foram digitalizadas e analisadas usando o software Materialise (Surgicase CMF (TM)). Dados craniométricas relativos ao terço médio da face, esfenóide e da órbita foram recolhido. Avaliação volumétrica do terço médio da face e órbita foi tabulada. A análise estatística foi realizada utilizando T-teste. Para a análise da retrusão do terço médio da face, trinta e seis tomografias foram incluídas (Controle n = 17, Crouzon / Apert n = 19). Todas as crianças estavam no período de dentição mista. A fossa anterior craniana é mais curta e mais larga em Crouzon/Apert versus Controles. Os ângulos da base do crânio medidos não foram estatisticamente diferentes entre os grupos. Crouzon/Apert mostrou ângulos mais obtusos entre as maiores asas do esfenóide, e mais obtusos entre as placas pterigóides. O ângulo formado pelo nasion-sela-fissura pterigomaxilar foi mais obtuso no grupo Crouzon e Apert comparado aos Controles. Não houve diferença volumétrica da maxila, zigoma e esfenóide comparando Crouzon/Apert aos Controles. Para a análise da dismorfologia orbital, trinta e uma tomografias computadorizadas foram incluídas (Controle n = 12, n = 9 Crouzon, Apert n = 10). A média de idade do grupo Apert foi de 5,31 ± 5 anos, Crouzon foi 5,77 ± 2,7 anos e Controle foi de 6,4 ± 3,6 anos (p = 0,6). O grupo de Crouzon era composto por 5 meninos e 4 meninas, o grupo de Apert continha 4 meninos e 6 meninas e o grupo Controle tinha 6 meninos e 6 meninas (p > 0,7). O comprimento da órbita óssea é 12% menor em Apert (p = 0,004) e 17% menor no grupo Crouzon quando comparado ao grupo Controle (p < 0,0001). A altura da órbita é 14% maior no grupo de Apert (p <0,0001) e 7% maior no grupo Crouzon quando comparados com os Controles (p = 0,03). A largura da órbita não é estatisticamente diferente no Crouzon ou grupo Apert quando comparados aos Controles (p = 0,1). O volume da órbita óssea é 21% menor nas crianças Apert (p = 0,0006) e 23% menor em Crouzon quando comparados aos Controles (p = 0,003). A projeção do globo é 99% maior em Apert e 119% maior em Crouzon quando comparados aos Controles (ambos p < 0,0001). Volume projetado fora da órbita é 179% maior em ambos Crouzon e Apert grupo quando comparados aos Controles (ambos p < 0,0001). O volume do globo ocular é 15% maior em Apert (p = 0,008) e 36% maior no grupo Crouzon quando comparado com o grupo Controle (p < 0,0001). O volume da porção do globo ocular dentro da órbita é 27% menor em Apert (p = 0,03). O grupo Crouzon não apresentou diferença estatística em relação ao grupo Controle para essa variável(p = 0,47). O volume da periórbita é 18% menor em Apert (p = 0,027) e 27% menor em Crouzon (p = 0,039), quando comparado com o grupo Controle (p = 0,001). O volume total dos tecidos moles (globo mais periórbita) em ambos os grupos Apert e Crouzon não foi estatisticamente diferente de Controles. Em suma, retrusão do terço médio da face em pacientes com Crouzon e Apert é associado com deformidade do esfenóide, que consiste na retrusão das placas pterigóides, causando alargamento e deformidade maxilar amplo, sugerindo crescimento diminuição inferior e anteriormente. Não há deficiência volumétrica dos ossos do terço médio da face nos grupos Crouzon e Apert comparado com Controles. Além disso, a dismorfologia ocular está relacionada com um encurtamento da órbita óssea associado com diminuição do volume orbital, aumento do volume do globo e diminuição do volume de periórbita. Apesar desses pacientes apresentarem volume normal do conteúdo da orbita, os conteúdos são alteradas, e da órbita óssea é mais curta e tem menos volume, o que não se encaixa na descrição clássica de exoftalmia ou exorbitismo / Midface retrusion is the hallmark of the syndromic dysotoses. Lack of forward projection and structural deficiency could be responsible, but neither has been adequately 3-dimensionally assessed. The purpose of this study is to examine cranial base interface and midface volume to provide understanding of the etiopathogenesis of midface deficiency. Children with CT scans in the absence of any surgical intervention were included. Demographic information was recorded for three groups (Apert, Crouzon, Control). CTs were digitized and manipulated using Materialise software (Surgicase CMF(TM)). Craniometric data relating to the midface, sphenoid and orbit was collected. Volumetric assessment of the midface and orbit were tabulated. Statistical analysis was performed using T-test. For the midface retrusion analysis, thirty-six CT scans were included (Control n=17, Crouzon/Apert n=19). All children were in the early mixed dentition. The anterior cranial fossa proved to be shorter and wider in Crouzon/Apert versus controls. The cranial base angles measured were not statistically different across the groups. Crouzon/Apert group showed angles more obtuse between the greater wings of the sphenoid, and more obtuse between the pterygoid plates. Nasion-sella-pterygomaxillary fissure angle was more obtuse in Crouzon/Apert. There was no volumetric difference in the maxilla, zygoma, and sphenoid comparing Crouzon/Apert to controls. For the orbital dysmorphology analysis, thirty-one CT scans were included (Control n=12, Crouzon n=9, Apert n=10). The mean age of the Apert group was 5.31 ± 5 years, Crouzon was 5.77 ± 2.7 years and Control was 6.4 ± 3.6 years (p=0.6). The Crouzon group consisted of 5 boys and 4 girls, the Apert group had 4 boys and 6 girls and the Control group had 6 boys and 6 girls (p > 0.7). The bony orbit length was 12% shorter in Apert (p=0.004) and 17% shorter in the Crouzon group when compared to controls (p < 0.0001). Orbital height was 14% higher in the Apert group (p < 0.0001) and 7% higher in the Crouzon group when compared to controls (p=0.03). Orbital width was not statistically different in either Crouzon or Apert group when compared to controls (p=0.1). The bony orbital volume was 21% smaller in the Apert children (p=0.0006) and 23% smaller in Crouzon when compared to controls (p=0.003). The globe projection was 99% larger in Apert and 119% larger in Crouzon groups when compared to controls (both p < 0.0001). Volume projected outside the orbit was increased over 179% in both Crouzon and Apert group when compared to Controls (both p < 0.0001). Globe volume was 15% larger in Apert (p=0.008) and 36% larger in Crouzon group when compared to Controls (p < 0.0001). Globe volume inside the orbit was 27% smaller in Apert (p=0.03) and the Crouzon group presented no statistical difference when compared to Controls (p=0.47). Periorbita volume was 18% less in Apert (p=0.027) and 27% less in Crouzon (p=0.039) group when compared to Controls (p=0.001). Total soft tissue volume (globe plus periorbita) in both Apert and Crouzon groups was not statistically different from Controls. In summary, midface retrusion in Crouzon and Apert is associated with altered sphenoid morphology consisting of widened and retruded pterygoid plates, with a flatter and wider maxilla, suggesting diminished growth inferiorly and anteriorly. There is no volumetric deficiency in Crouzon/Apert versus controls. Orbital dysmorphology is associated with altered sphenoid morphology, shortened bony orbit with diminished orbital volume, increased globe volume and decreased volume of periorbita. Despite normal volume of the overall orbital contents, the contents are altered, and the bony orbit is shorter and holds less volume, which does not fit the classic description of either exophthalmos or exorbitism

Orientador: Luiz Carlos Vulcano / Resumo: Este estudo teve por objetivo descrever a anatomia das estruturas intracranianas em capivaras (Hydrochoerus hydrochaeris) in vivo por meio da ressonância magnética, propiciando informações mais detalhadas da anatomia encefálica e ocular desta espécie. Foram utilizados oito animais e duas peças anatômicas encefálicas para o estudo descritivo comparando-os com animais domésticos e outros roedores, sendo observado redução dos sulcos e giros cerebrais, bulbos olfatórios e hipófise proeminentes e evidenciação do ventrículo olfatório. Além das estruturas do encéfalo, foram avaliados também o bulbo ocular e a órbita desses animais obtendo a média (+ DP) do comprimento axial do bulbo ocular de 24,1 + 1,8 mm, profundidade da câmara anterior de 2,8 + 1,8 mm, espessura da lente de 8,5 + 0,7 mm e espessura do nervo óptico de 2,9 + 0,6 mm e 2,6 + 0,6 mm para o terço proximal e distal, respectivamente. Com esses estudos, foi possível concluir que capivaras apresentaram sulcos e giros em maior proporção do que outros roedores e a hipófise e bulbo olfatório dessa espécie foram mais amplos quando comparado aos animais domésticos. Além disso, as estruturas da órbita apresentaram melhor detalhamento da sequência T1 de ressonância magnética e que as medidas, apesar de serem utilizadas na rotina ultrassonográfica, podem ser utilizadas como complemento para o estudo da órbita de capivara por meio da ressonância magnética. / Abstract: The aim of this study was to describe the anatomy of intracranial structures in living capybara (Hydrochoerus hydrochaeris) by means of magnetic resonance imaging (MRI) providing more detailed information of brain, eye and orbit anatomy of this species. Eight capybaras and two anatomic encephalic specimens were used for the descriptive study comparing them with domestic animals and other rodents, observing reduction of the sulcus and gyrus, prominent olfactory bulb and pituitary, and presence of the olfactory ventricle. In addition, ocular bulb and orbit of these animals were also evaluated, obtaining the (+ SD) of the axial length of the eye bulb of 24.1 + 1.8 mm, anterior chamber depth of 2.8 + 0.6 mm, lens thickness of 8.5 + 0.7 mm, and optic nerve thickness of 2.6 + 0.6 and 2.9 + 0.6 mm from proximal to distal portion, respectively. In conclusion, capybaras had sulcus and gyrus in a greater proportion than other rodents and the hypophysis and olfactory bulb were more extensive when compared to domestic animals. In addition, the orbital structures presented better detail on T1 MR images and that measurements used in the ultrasound routine can be used as a complement for the study of the orbit of capybaras by means of MRI exams. / Doutor

Le projet de thèse est divisé en deux parties. D’une part, la génération directionnelle et singulière de plasmons de surface (SPPs) par des ouvertures nanométriques a été réalisé et optimisé par le biais de microscopie de fuites radiatives (LRM). Nous démontrons expéri- mentalement qu’une structure plasmonique composée de nano-ouvertures en forme de T et Λ permet de contrôler le couplage unidirectionnel et radialdes SPPs grâce au spin de la lumière incidente. Pour confirmer nos résultats expérimentaux, nous développons un modèle analytique qui décrit les coupleurs plasmoniques constitués de nano-ouvertures par représentation multidipolaire, permettant ainsi une explication théorique de la directionalité et de la formation de vortex plasmonique. L’optimisation des paramètres géométriques tels que l’angle au sommet des ouvertures en forme de Λ montre la possibilité de maximiser la directivité et le taux d’extinction à la fois pour le couplage directionnel et la génération des vortex dans le champ lointain. Parailleurs, notre méthode basée sur la détection LRM, permet une analyse quantitative et est avérée être une technique de caractérisation sophistiquée pour cartographier le champ plasmonique. Il fournit également plusieurs nouvelles possibilités pour la focalisation de SPP contrôlée en polarisation.D’autre part,le couplage spin-orbite de la lumière dans un guide et son effet réciproque sont réalisées et confirmées expérimentalement et théoriquement. Les coupleurs et découpleurs réseaux sur le guide d’ondes sont d’abord développés et étudiés. La sortie parfaite de la lumière confinée par le découpleur nous offre la possibilité de détecter les ondes guidées. La fluorescence des nanocristaux déposés sur la surface de l’échantillon montre une autre possibilité de visualiser directement la propagation de la lumière dans le guide d’onde. Le couplage directionnel contrôlé par spin est réalisé par des antennes en forme de Λ et est confirmé par des images en champ sombre avec des découpleurs et des images de fluorescence. En outre, l’effet réciproque est observé avec une imperfection de polarisation de sortie qui est expliqué théoriquement par le fait que les ordres de diffraction par les antennes en forme de Λ influent sur les états de polarisation finaux. Ainsi, l’effet réciproque est parfaitement réalisé par la sélection d’une région spécifique de diffraction dans le plan de Fourier. La caractérisation quantitative des interactions spin-orbite nous permet d’envisager le développement de nouveaux coupleurs directionnels dans le domaine de la nanophotonique tels que le traitement quantique de l’information. / In this project, two contributions are reported. Firstly, the directional and singular generation of Surface Plasmon Polaritons (SPPs) in the nanoapertures is investigated using the Leakage Radiation Microscopy (LRM). We demonstrate experimentally spin-driven directional coupling as well as singularity (inward) and vortex (outward radial coupling) of SPPs by nanostructures built with T-shaped and Λ-shaped apertures.To support our experimental findings, we develop an analytical model based on a multidipolar representation of Λ- andT-shaped aperture plasmonic couplers, allowing a theoretical explanation of both directionality and singular SPP formation. The optimal apex angle of Λ-shaped apertures shows the possibility to maximize the directiviy and extinction ratio for both directional coupling and singular SPP generation in the far field. Besides, our method based on LRM detection, allows quantitative analysis and is proven to be a sophisticated characterization technique for mapping the SPP vortex field.It also provides several new possibilities for polarization-controlled SPP sub-wavelength focusing.Secondly, the spin-orbit coupling of light into a photonic waveguide and its reciprocal effect are realized and confirmed both experimentally and theoretically. Coupler and decoupler gratings on the waveguide are firstly developed and investigated. The radiation of the confined light from the decoupler provides us a possibility to detect the guided waves. The fluorescence of nanocrystals deposited on the sample surface shows another possibility to directly visualize the light propagation in the waveguide. The spin-driven directional coupling is achieved by Λ-shaped antennas and is certified by the dark field images with decouplers and the fluorescence images. Furthermore, the reverse effect is observed with an imperfection of output polarization which is explained that the diffraction orders by the Λ-shaped apertures influence the final polarization states based on an analytical model. Thus, the reciprocal effect is realized by selecting the specific diffraction region on the Fourier plane. We believe that the quantitative characterization of spin-orbit interactions will pave the way for developing new directional couplers in the field of nanophotonics such as quantum information processing and so forth.

The layered iridates such as Sr2IrO4 and Sr3Ir2O7, have attracted substantial attention due to their novel electronic states originating from strong spin-orbit coupling and electron-correlation. Recent studies have revealed the possibilities of novel phases such as topological insulators, Weyl semimetals, and even a potential high-Tc superconducting state with a d-wave gap. However, there are still controversial issues regarding the fundamental electronic structure of these systems: the origin of the insulating gap is disputed as arising either from an antiferromagnetic ordering, i.e. Slater scheme or electron-correlation, i.e. Mott scheme. Moreover, it is a formidable task to unveil the physics of layered iridates due to the limited number of available materials for experimental characterizations. One way to overcome this limit and extend our investigation of the layered iridates is using metastable materials. These materials which are far from their equilibrium state, often have mechanical, electronic, and magnetic properties that different from their thermodynamically stable phases. However, these materials cannot be synthesized using thermodynamic equilibrium processes. One way to synthesize these materials is by using pulsed laser deposition (PLD). PLD is able to generate nonequilibrium material phases through the use of substrate strain and deposition conditions. Using this method, we have synthesized several thermodynamically metastable iridate thin-films and have investigated their electronic and optical properties. Synthesizing and investigating metastable iridates opens a path to expand the tunability further than the ability of the bulk methods. This thesis consists of four studies on metastable layered iridate thin film systems. In the first study, three-dimensional Mott variable-range hopping transport with decreased characteristic temperatures under lattice strain or isovalent doping has been observed in Sr2IrO4 thin films. Application of lattice strain or isovalent doping exerts metastable chemical pressure in the compounds, which changes both the bandwidth and electronic hopping. The variation of the characteristic temperature under lattice strain or isovalent doping implies that the density of states near the Fermi energy is reconstructed. The increased density of states in the Sr2IrO4 thin films with strain and isovalent doping could facilitate a condition to induce unprecedented electronic properties, opening a way for electronic device applications. In the second study, the effects of tuning the bandwidth via chemical pressure (i.e., Ca and Ba doping) on the optical properties of Sr2IrO4 epitaxial thin films has been investigated. Substitution of Sr by Ca and Ba ions exerts metastable chemical pressure in the system, which changes both the bandwidth and electronic hopping. The optical conductivity results of these thin films suggest that the two-peak-like optical conductivity spectra of the layered iridates originates from the overlap between the optically-forbidden spin-orbit exciton and the inter-site optical transitions within the Jeff = ½ band, which is consistent with the results obtained from a multi-orbital Hubbard model calculation. In the third study, thermodynamically metastable Ca2IrO4 thin- films have been synthesized. Since the perovskite structure of Ca2IrO4 is not thermodynamically stable, its bulk crystals do not exist in nature. We have synthesized the layered perovskite phase Ca2IrO4 thin- films from a polycrystalline hexagonal bulk crystal using an epitaxial stabilization technique. The smaller A-site in this compound compared to Sr2IrO4 and Ba2IrO4, increases the octahedral rotation and tilting, which enhance electron-correlation. The enhanced electron-correlation is consistent with the observation of increased gap energy in this compound. This study suggest that the epitaxial stabilization of metastable-phase thin-films can be used effectively for investigating complex-oxide systems. Finally, structural, transport, and optical properties of tensile strained (Sr1-xLax)3Ir2O7 (x = 0, 0.025, 0.05) thin-films have been investigated. While high-Tc superconductivity is predicted in the system, all of the samples are insulating. The insulating behavior of the La-doped Sr3Ir2O7 thin-films is presumably due to disorder-induced localization and ineffective electron-doping of La, which brings to light the intriguing difference between epitaxial thin films and bulk single crystals of the iridates. These studies thoroughly investigate a wide array of novel electronic and optical phenomena via tuning the relative strengths of electron correlation, electronic bandwidth, and spin-orbit coupling using perturbations such as chemical doping, and the stabilization of metastable phases in the layered iridates.

Rotordynamic and thermal analyses of compliant flexure pivot tilting pad gas bearings were performed. First, compliant flexure pivot tilting pad gas bearings with pad radial compliance (CFTPBs) were introduced and designed for high-speed oil-free micro turbomachinery. The pad radial compliance was for accommodation of large rotor growth at high speeds. Parametric studies on pivot offset, preload, and tilting stiffness were performed using non-linear orbit simulations and coast-down simulations for an optimum design. Second, coast-down tests for imbalance response and stability of typical rotor-bearing system with a rigid rotor and two CFTPBs designed from the above design studies were conducted over operating speeds up to 55 krpm. Prediction of synchronous rotordynamic responses was made in terms of critical speed for various imbalance modes by using a rotordynamic analysis software (XLTRC), combined with dynamic force coefficients from the perturbation analysis. For stability analyses, a generalized orbit simulation program was developed considering both the translational and angular rotor motions with two different bearings. Linear stability analyses for the conical vibration mode were also performed by using XLTRC and the perturbation analysis based on the Lund method. Predictions of whirl speed showed good agreement to the tests, but the estimated onset speed of instability appeared lower than the measured instability. Finally, a new thermo-hydrodynamic analysis model of a typical rotor-bearing system with CFTPBs was presented, accompanying linear perturbation analyses to investigate thermal effects on the rotordynamic performance. A numerical procedure was established for solving the generalized Reynolds equation, the 3-D energy equation, and the associated boundary conditions at the pad inlet flow and solid walls (rotor and pad) simultaneously. Parametric studies were conducted on nominal clearance and external load. Nominal clearance showed significant influence on temperature fields, and external load had uneven thermal effects among pads. Case studies with heat flux and temperature boundary conditions on the rotor end surface were performed to simulate various working conditions of the bearing. Large rotor thermal growth due to the high rotor temperature showed noticeable influence on rotordynamic performance by increasing direct stiffness and damping coefficients.

<b>Résumé:</b> Dans le but de décrire la rotation résonante rigide de Mercure, différents modèles de rotation résonante de type 3 : 2 à deux et trois dimensions, moyennisés sur les courtes périodes et exprimés en formalisme hamiltonien sont proposés. Dans le premier modèle, l'axe de rotation de Mercure est confondu avec son plus petit axe d'inertie et la planète n'est soumise à l'action d'aucune force autre que celle de la gravitation. Le couplage de ces 2 degrés de liberté est mis en évidence. Un modèle à 3 degrés de liberté tenant compte de la dissociation de l'axe du moment angulaire et de l'axe de figure est ensuite présenté. Dans ces deux modèles, le développement du potentiel est limité à l'ordre 2 en excentricité. Afin d'estimer l'erreur commise par ce choix de troncature, les Hamiltoniens sont développés à des ordres plus élevés; les nouveaux termes ainsi obtenus sont considérés comme des perturbations et traités à l'aide de la théorie de Lie. L'influence des autres planètes du Système Solaire est enfin étudiée en incluant, dans un premier temps, une précession constante du noeud ascendant et du péricentre dans notre modèle de base et, dans un second temps, en considérant que l'inclinaison et l'excentricité sont des fonctions lentes du temps permettant l'utilisation de la théorie de l'invariant adiabatique étendue à 2 degrés de liberté. Une étude des équilibres et des périodes propres de chaque modèle est réalisée.// <b>Abstract:</b> In the aim to describe the Mercury's rigid resonant rotation, different 3: 2 spin-orbit resonant rotation models with two and three dimensions , averaged on the short periods and expressed in Hamiltonian formalism is proposed. In the first model, Mercury's rotation axis and its smallest axis of inertia aren't distinct and no force except the gravitation one acts on the planet. The coupling between these 2 degrees of freedom is underlined. A 3 degrees of freedom model taking into account the dissociation of the angular momentum axis from the figure axis is aftewards presented. In these two models, the potential devellopment is limited to the second order in eccentricity. In order to estimate the error due to this troncature choice, the Hamiltonians are devellopped up to higher orders; the new terms so obtained are considered as perturbations et treated thanks to Lie theory. The influence of the other planets of the Solar System is finally studied by including, in a first time, a constant precession of the ascending node and of the pericenter in our basis model and, in a second time, by considering that the inclination and the excentricity are slow functions of time allowing the use of the adiabatique invariant extended to 2 degrees of freedom. A study of the equilibria and of the proper periods of each model is realized.

The underlying theory of “Spin” of an electron and its associated inter-actions causing internal fields and spectral shift to bulk-magnetism iswell established now. Our understanding of spin properties is significant andmore useful than ever before. In recent years there seems to be an enormousinterest towards application oriented materials that harness those spin prop-erties. Theoretical simulations remain in a position to “assist or pilot” theexperimental discovery of new materials.In this work, we have outlined available methodologies for spin coupling inmulti-reference and DFT techniques. We have benchmarked multi-referencespin-Hamiltonian computation in isoelectronic diradicals - Trimethylenemethane(TMM) and Oxyallyl. Also with DFT, parameters are predicted with anewly discovered TMM-like stable diradicals, reported to have large positiveexchange interactions. Excellent agreement were obtained and our findingsemphasize that the dipole-dipole interactions alone can predict the splittingof triplet states and that DFT spin procedures hold well in organic species.We have extended our spin-studies to a highly application oriented ma-terial - nanographene. Using our novel spin-parameter arguments we haveexplained the magnetism of graphene. Our studies highlight a few signifi-cant aspects - first there seems to be a size dependency with respect to thespin-Hamiltonian; second, there is a negligible contribution of spin-orbit cou-pling in these systems; third, we give a theoretical account of spin restrictedand unrestricted schemes for the DFT method and their consequences forthe spin and spatial symmetry of the molecules; and, finally, we highlightthe importance of impurities and defects for magnetism in graphene. Wepredict triplet-singlet transitions through linear response TDDFT for thetris(8-hydroxyquinoline) aluminium complex, an organic molecule shown tohave spintronics applications in recent experiments. Our spin studies werein line with those observations and could help to understand the role of thespin-coupling phenomena. / QC 20120531