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"We cannot afford the luxury any longer of ignoring the nature of the bonding in these interesting compounds .... " P.E.D. Morgan, (1974). An understanding of bonding is paramount to furthering our understanding of materials (Morgan, 1974). The properties of materials are governed by the interactions between atoms. These interactions are governed by the nature of the bonds. In this study, two methods are explored which provide insight into chemical interactions. First, promolecule radii, calculated for nitride, oxide, and sulfide coordinated polyhedra with bond lengths fixed at the sums of effective ionic and crystal radii, are analyzed. Radii calculated for transition and non-transition cations for the first four rows of the periodic table are highly correlated with crystal radii derived for oxide and sulfide crystals and with ionic radii derived for nitride crystals. Promolecule radii calculated for the coordination polyhedra match experimentally determined bonded radii to within ~0.02Å, on average. Calculated radii anions tend to match ionic radii when bonded to highly electropositive cations and atomic radii when bonded to highly electronegative cations. In the second study, molecular orbital calculations were completed on a series of small molecules containing the nitride anion. Bond type can be characterized by studying the systematics of parameters derived from the bond critical point properties of the electron density distributions. A set of criteria is established to suggest how covalent or ionic a bond is. This criteria is based on bond critical point properties such as the Laplacian of the electron density distribution evaluated at the bond critical point, the electron density distribution at the critical point, the local energy density at the critical point, the relative electronegativity of the cation, the curvatures of the electron density distribution, and the distance from the nucleus of the nitride anion to the bond critical point, (the bonded radius of the nitrogen atom). Parameters computed for promolecule data indicate that these easily obtained results offer a method of calculating bond critical properties which are close in value to the more extensive results derived from molecular orbital calculations. / Ph. D.

La connaissance des propriétés critiques des mélanges binaires est importante pour la conception et le développement des procédés des industries chimiques, mais également, pour l'amélioration et l'extension des modèles thermodynamiques prédictifs. Cependant, des données expérimentales critiques liquide - vapeur de mélanges binaires sont relativement rare dans la littérature. C'est la raison pour laquelle, nous avons acquis un nouvel appareil permettant de mesurer les points critiques de corps purs et de mélanges. Dans une première étape, nous avons mis au point et validé le protocole expérimental, en comparant les résultats de nos mesures aux données de la littérature. Dans une deuxième étape, nous montrons l'intérêt que la mesure de points critiques de mélanges binaires peut présenter pour le développement de deux types de procédés : i) la production de biodiesel par voie supercritique et ii) l'étude de comportement de phases de nouveaux réfrigérants. Les résultats expérimentaux obtenus ont été également utilisés pour déterminer les paramètres d'interactions entre groupes du modèle PPR78 / Knowledge of mixture critical data is not only important for the design and the improvement of chemical processes but also to extend the range of applicability of predictive equations of state. However, mixture critical data comprise only a small percentage of the fluid phase equilibria data available in the open literature. This is the reason why it was decided to acquire a new synthetic-dynamic apparatus capable of determining the critical points of pure substances and multi-component mixtures. In a first step, the validation of the experimental procedure for critical point measurements was performed by comparing the experimental results obtained in this work with literature data. In a second step, the application of mixture critical data to the development of two types of process: i) biodiesel production via supercritical process and ii) phase behaviour of new refrigerants is presented. The experimental critical points measured in this work were also used for determining new group interaction parameters of the PPR78 model

Nas últimas décadas, o fenômeno urbano na cidade de Juazeiro do Norte, localizado no interior do Ceará, no nordeste brasileiro, reproduziu-se de forma tão acelerada em direção as cidades limítrofes, Barbalha e Crato, subordinando-as, de tal modo que atingiu no fim do século passado seu ponto crítico em face de uma metamorfose urbana que se processa impactando as formas, funções e estrutura do espaço urbano. Em razão disso, o espaço tornou-se uma das novas raridades, ora subsumido como valor de troca pelo mercado imobiliário como também pelos empreendimentos comerciais, ora sendo reivindicado como valor de uso pelos sujeitos subalternizados. Essa encruzilha inaugura um novo momento em que a vida cotidiana é atravessada por novos referenciais, sendo colonizada por uma ordem distante, que ganha materialidade nos espaços economicamente mais dinâmicos da cidade. Nesse sentido, o bairro, enquanto lugar cotidianamente vivido, não só reflete as transformações decorrentes dessa metamorfose urbana como dialeticamente a condiciona, seja como um resíduo, seja porque se torna potencialmente alvo dos interesses dos agentes hegemônicos que regem a produção do espaço urbano nesse momento atual. Para compreender essas transformações e conflitos que se desencadeiam no seio do cotidiano, emergentes nesse momento atual da cidade, elege-se o bairro João Cabral, um espaço popular originalmente periférico cuja formação se deu no último quartel do século passado. Esse recorte espacial específico está relacionado a dois aspectos pelos os quais esse bairro em questão revela-se um fio condutor da metamorfose urbana da cidade, analisada sob a ótica da vida cotidiana: a) sua localização atual privilegiada, contígua aos espaços que se configuraram como áreas que exercem centralidade ou são subcentros, concorrendo com o centro principal; b) a emergência de uma nova condição espacial cujo conteúdo pode ser apreendido por meio das práticas socioespacias dos moradores. Assim, esse estudo busca dar cabo da seguinte questão: Quais contradições e conflitos têm se manifestado no bairro João Cabral no contexto contemporâneo em que se processa uma metamorfose urbana na cidade de Juazeiro do Norte, considerando o plano do cotidiano? Para tanto, recorremos à teoria urbana crítica, bem como ao método progressivo-regressivo lefebvriano. / In the last decades, the urban phenomenon in the city of Juazeiro do Norte, located in the interior of Ceará, in northeastern Brazil, reproduced itself so fast towards the neighboring cities, Barbalha and Crato, subordinating them, in such a way that it reached at the end of the last century its critical point in the face of an urban metamorphosis that takes place impacting the forms, functions and structure of the urban space. Because of this, space has become one of the new rarities, now subsumed as exchange value by the real estate market as well as commercial ventures, now being claimed as use value by subalternized individuals. This crossroads inaugurates a new moment in which daily life is crossed by new references, being colonized by a distant order that gains materiality in the most economically dynamic spaces of the city. In this sense, the neighborhood, as a place lived daily, not only reflects the transformations arising from this urban metamorphosis, as a conditional condition, either as a residue, or because it becomes potentially a target of the interests of the hegemonic agents that govern the production of urban space at that moment current. In order to understand these transformations and conflicts that are unleashed within the daily life, emerging at this current moment of the city, the neighborhood is chosen João Cabral, an originally peripheral popular space whose formation occurred in the last quarter of the last century. This specific spatial clipping is related to two aspects by which this neighborhood in question proves to be a guiding thread of the urban metamorphosis of the city, analyzed from the point of view of everyday life: a) its present privileged location, contiguous to the spaces that have been configured as areas that exercise centrality or are subcenters, competing with the main center; b) the emergence of a new spatial condition whose content can be apprehended through the socio-spatial practices of the residents. Thus, this study seeks to answer the following question: What contradictions and conflicts have been manifested in the neighborhood of João Cabral in the contemporary context in which an urban metamorphosis in the city of Juazeiro do Norte takes place, considering the daily plan? For this, we resort to critical urban theory, as well as Lefebvre\'s progressive-regressive method.

In this thesis we use the holographic gauge/gravity duality to study two different aspects of strongly coupled non-Abelian plasmas. In the first topic we study the effects of strong (Abelian) magnetic fields on the transport coefficients of a strongly coupled non-Abelian plasma. Due to the spatial anisotropy created by the magnetic field, the most general viscosity tensor of a magnetized plasma has 5 shear viscosity coefficients and 2 bulk viscosities. We use the holographic correspondence for a strongly coupled N=4 Supersymmetric Yang-Mills (SYM) plasma to evaluate the shear viscosity perpendicular to the magnetic field and the shear viscosity parallel to the field. In the presence of a magnetic field, the shear viscosity perpendicular to the field saturates the Kovtun-Son-Starinets viscosity bound while in the direction parallel to the field the bound is violated. The second topic investigated in this thesis is motivated by the study of the near equilibrium behavior of strongly interacting non-Abelian plasmas that display a critical point in their phase diagram. We focus on the spectra of non-hydrodynamic quasinormal modes of a strongly coupled N=4 SYM plasma in the presence of a chemical potential, which displays a critical point in equilibrium. Except close to the critical point, we observe that by increasing the chemical potential one generally increases the damping rate of the quasinormal modes, which leads to a reduction of the characteristic equilibration times in the dual strongly coupled plasma. However, as one approaches the critical point the typical equilibration time increases though its derivative with respect to the chemical potential diverges with an exponent equal to -1/2. We also find a purely imaginary non-hydrodynamical mode in the vector diffusion channel at nonzero chemical potential which dictates the equilibration time in this channel near the critical point. / Nessa tese usamos a dualidade holográfica calibre/gravidade para estudar dois aspectos diferentes de plasmas não-Abelianos fortemente acoplados. No primeiro tópico estudamos os efeitos de campos magnéticos (Abelianos) intensos sobre o coeficientes de transporte de um plasma não-Abeliano fortemente acoplado. Devido à anisotropia espacial criada pelo campo magnético, o tensor de viscosidade mais geral de um plasma magnetizado deve possuir 5 coeficientes de viscosidade de cisalhamento e 2 de viscosidade volumétrica. Usamos a correspondência holográfica para um plasma N=4 Supersimétrico de Yang-Mills (SYM) fortemente acoplado para calcular a viscosidade de cisalhamento perpendicular ao campo magnético e a viscosidade de cisalhamento paralela ao campo. Na presença do campo magnético, a viscosidade de cisalhamento perpendicular ao campo satura o limite viscoso de Kovtun-Son-Starinets enquanto que na direção paralela ao campo o limite é violado. O segundo tópico investigado nessa tese é motivado pelo estudo do comportamento próximo ao equilíbrio de plasmas não-Abelianos fortemente interagentes que exibem um ponto crítico em seus diagramas de fase. Focamos no espectro dos modos quasinormais não-hidrodinâmicos de um plasma N=4 SYM fortemente acoplado na presença de um potencial químico, que exibe um ponto crítico no equilíbrio. Exceto próximo ao ponto crítico, observamos que ao aumentar o potencial químico geralmente se intensifica a taxa de amortecimento dos modos quasinormais, que levam à redução dos tempos de equilibração característicos do plasma dual fortemente acoplado. Entretanto, aproximando-se do ponto crítico o tempo de equilibração típico aumenta embora sua derivada em relação ao potencial químico diverge com um expoente igual à -1/2. Encontramos também um modo não-hidrodinâmico puramente imaginário no canal de difusão vetorial com potencial químico não-nulo que dita o tempo de equilibração neste canal próximo do ponto crítico.

A second-order Lagrangian system is a generalization of a classical mechanical system for which the Lagrangian action depends on the second derivative of the state variable. Recent work has shown that the dynamics of such systems c:an be substantially richer than for classical Lagrangian systems. In particular, topological properties of the planar curves obtained by projection onto the lower-order derivatives play a key role in forcing certain types of dynamics. However, the application of these techniques requires an analytic restriction on the Lagrangian that it satisfy a twist property. In this dissertation we approach this problem from the point of view of curve shortening in an effort to remove the twist condition. In classical curve shortening a family of curves evolves with a velocity which is normal to the curve and proportional to its curvature. The evolution of curves with decreasing action is more general, and in the first part of this dissertation we develop some results for curve shortening flows which shorten lengths with respect to a Finsler metric rather than a Riemannian metric. The second part of this dissertation focuses on analytic methods to accommodate the fact that the Finsler metric for second-order Lagrangian system has singularities. We prove the existence of simple periodic solutions for a general class of systems without requiring the twist condition. Further; our results provide a frame work in which to try to further extend the topological forcing theorems to systems without the twist condition. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2014. / FAU Electronic Theses and Dissertations Collection

by Chu Lap-foo. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1994. / Includes bibliographical references (leaves 68-69). / Introduction --- p.iii / Chapter 1 --- Basic Properties of Singular Solutions --- p.1 / Chapter 1.1 --- An Asymptotic Radial Result --- p.2 / Chapter 1.2 --- Local Uniqueness of Radial Solutions --- p.8 / Chapter 2 --- Dirichlet Problem : Existence Theory I --- p.11 / Chapter 2.1 --- Formulation --- p.12 / Chapter 2.2 --- Explicit Solutions on Balls --- p.14 / Chapter 2.3 --- The Moser Inequality --- p.19 / Chapter 2.4 --- Existence of Solutions in General Domains --- p.24 / Chapter 2.5 --- Spectrum of the Problem --- p.26 / Chapter 3 --- Dirichlet Problem : Existence Theory II --- p.29 / Chapter 3.1 --- Mountain Pass Lemma --- p.29 / Chapter 3.2 --- Existence of Second Solution --- p.31 / Chapter 4 --- Dirichlet Problem : Non-Existence Theory --- p.36 / Chapter 4.1 --- Upper Bound of λ* in Star-Shaped Domains --- p.36 / Chapter 4.2 --- Numerical Values --- p.41 / Chapter 5 --- The Neumann Problem --- p.42 / Chapter 5.1 --- Existence Theory I --- p.43 / Chapter 5.2 --- Existence Theory II --- p.47 / Chapter 6 --- The Schwarz Symmetrization --- p.49 / Chapter 6.1 --- Definitions and Basic Properties --- p.49 / Chapter 6.2 --- Inequalities Related to Symmetrization --- p.58 / Chapter 6.3 --- An Application to P.D.E --- p.63 / Bibliography --- p.68

Thesis: Ph. D., Massachusetts Institute of Technology. Department of Materials Science and Engineering, 1975. / Vita. / Includes bibliographical references. / The discrepancy between two recent phase diagram determinations of the Fe-Al system is resolved experimentally. Both diagrams are correct, but-one is a metastable coherent phase diagram. The iron-aluminum system possesses a tricritical point where a line of [lambda]- transitions ends at a miscibility gap at about 23 atom percent aluminum and 615°C. Rules of general applicability governing phase separation within the miscibility gap are developed. Application of the rules to the iron-aluminum system results in detailed predictions about the mechanisms of decomposition and their sequences in this system. Electron microscopy is used to study the reactions experimentally and the results are in agreement with theoretical predictions. / by Samuel Miller Allen. / Ph. D.

Traditional excess Gibbs energy models in terms of temperature, pressure, and concentration become progressively less effective in describing the thermodynamics of aqueous solutions at temperatures above 300 ¢ªC, and are totally inadequate in the critical region of water. This deficiency is due to the strong ion association and the large property fluctuations (such as density) with small variations in pressure, temperature, and solute concentration around the critical point of water. In this work, a speciation-based model has been developed to describe the thermodynamic properties of aqueous sodium chloride solutions in the critical region of water. The anomalous fluctuation problem is avoided by adopting a residual Helmholtz energy approach in terms of temperature, density, and solute concentration. Partial ion dissociation is accounted for by including an isochoric equilibrium constant equation and a mean spherical approximation in the present model. The present model includes such classical interactions or effects as hard-sphere interactions, dipole-dipole interactions, ion dissociation effects, long-range ion-ion interactions, and a non-classical perturbation term. The related parameters that account for these effects were regressed to fit the measured values in the critical region of water. Densities, compressibility factors, apparent molar volumes, heats of dilution, and apparent isobaric molar heat capacities were used to test the validity of the model. The predicted values in this work agree well with the literature data over a wide range of temperatures (350 to 400 ¢ªC), pressures (17.5 to 40 MPa), and sodium chloride concentrations (0 to 5 mol/kg). Comparisons with other models are also included in this work. This model can be used to predict speciation, solute dissociation reaction, and many other comprehensive properties in aqueous sodium chloride solutions at near-critical conditions.