<p>U disertacije je sprovedeno teorijsko istraživanje mikroskopskih i makroskopskih (termodinamičkih) osobina tankoslojnih i niskodimenzionih kristalnih struktura u okviru modela fonona akustičkog tipa. Upoređivanjem fononskih spektara i termodinamičkih svojstava u neograničenim i posmatranim nanostrukturama ustanovljeno je da se oni znatno razlikuju usled postojanja granica kod niskodimenzionih sistema. Takođe je primećeno da u fononskim spektrima niskodimenzionih struktura postoji energijski procep, &scaron;to znači da je energija pobuđivanja fonona u niskodimenzionim kristalnim strukturama veća od one u balku. Ovo uzrokuje da toplotna kapacitivnost u niskotemperaturskoj oblasti ima i znatno niže vrednosti u ograničenim strukturama nego u masovnim uzorcima.</p> / <p>In ths work, a theoretical study of microscopic and thermodynamic properties of thin-layered and low-dimensional crystalline structures &nbsp;of the model type of acoustic phonons was carried out. Comparison of the phonon spectra and &nbsp;thermodynamic properties of the infinite with the observed &nbsp;nanostructures revealed that they differ greatly because of the existence of borders in the low-dimensional systems. It is also noted that in the phonon spectra of nanostructures an energy gap exists, which means that the energy od excitation of phonons in the nanostructured crystal systems is higher than those of the bulk. This indicates that the heat capacitance in the low-temperature range ha a significantly lower values in bounded structures than in massive samples.</p>

Blendas poliméricas de biopolímeros, além de apresentarem uma melhora das propriedades do material, ainda possuem as vantagens de serem biocompatíveis, biodegradáveis e apresentar baixa toxicicidade, como no caso de blendas de alginato de sódio e fibroína de seda. Membranas confeccionadas a partir desta mistura apresentam grande potencial no desenvolvimento de curativos de alto desempenho, proporcionando condições ótimas de cicatrização. Entretanto, o processo de mistura destes biopolímeros é bastante complexo e resulta na separação de fases, processo que ainda não foi muito explorado. Este trabalho buscou explorar experimentalmente o comportamento do equilíbrio de fases dos sistemas aquosos contendo fibroína de seda e alginato de sódio em diversos valores de pH. Soluções aquosas de fibroína foram previamente preparadas por meio de processo de diálise, e soluções de alginato, por meio de dissolução direta em água. Ambas as soluções eram misturadas em concentrações em que se desejava avaliar o comportamento de fases. Após a separação de fases, a fase líquida sobrenadante era coletada, a fibroína quantificada via espectrofotometria e o alginato, via calcinação. Observou-se que a região monofásica do diagrama de fases é pequena, e a separação de uma segunda fase ocorre em concentrações baixas dos dois biopolímeros. A separação de fases pôde ser descrita como a precipitação da fibroína pela adição de alginato, e a solubilidade da fibroína pôde ser descrita por meio da equação de Cohn. As curvas de solubilidade obtidas não apresentaram diferenças significativas em função do pH. Medidas do potencial Zeta de soluções de alginato e fibroína em diversas faixas de pH não mostraram diferenças significativas quanto à carga superficial das moléculas, o que é compatível com a ausência de influência do pH no equilíbrio de fases. / Polymer blends formed by biopolymers may show an improvement of material properties (compared to the pure biopolymers), and present advantages such as biocompatibility, biodegradability and low toxicity. An interesting biopolymer blend is that formed by sodium alginate and silk fibroin. Membranes prepared with this mixture show great potential in the development of high-performance wound dressing, since it provides optimum healing conditions. However, the mixing process of these two biopolymers is complex and has not been extensively explored. In this work the phase equilibrium behavior of aqueous systems containing silk fibroin and sodium alginate was experimentally studied at different pH values. Fibroin aqueous solutions were previously prepared through dialysis, and alginate solutions were prepared by direct dissolution in water. Both solutions were mixed at the concentration range in which the phase behavior of the system was to be assessed. After phase separation, the supernatant liquid phase was separated, the fibroin was quantified through spectrophotometry. and the alginate was quantified through calcination. The single-phase region of the phase diagram is small, and the separation of a second phase occurs at low concentrations of both biopolymers. The phase separation could be described as the precipitation of fibroin due to the addition of alginate, and the solubility of fibroin was described by the Cohn equation. The solubility was not significantly affected by the pH. The Zeta potential of either alginate or fibroin, measured in solutions of different pH values, did not present any significant difference concerning the surface charges of these macromolecules. This finding agrees with the absence of pH influence upon the phase equilibrium.

This thesis examines various reductive case studies in thermal physics. In particular, I argue that according to my account of reduction-as-construction, there are two suc- cessful examples of reduction. Thermodynamics reduces to statistical mechanics, and statistical mechanics reduces to the underlying microdynamics - be they quantum or classical. The reduction of a given theory alters that theory's scope, that is: its domain of applicability. The scope of thermodynamics will be central to this thesis - and I will argue for a narrower scope than some authors. This thesis consists of four Chapters, together with an introduction and a conclusion. In Chapter 1, I discuss how different levels of description relate to one another. I argue that a higher-level of description is reduced to the lower level, if the higher-level quantities and their behaviour can be constructed or captured by the lower-level theory. I claim that 'functionalism' can be helpful in securing reductions. In this Chapter I also argue that the aim of reduction is to vindicate, not eliminate, the higher-level theory. In Chapter 2, I tackle the reduction of thermodynamics to statistical mechanics. I articulate the functional, or nomological, role of various thermodynamic quantities that are implicitly defined by the zeroth, first and second laws of thermodynamics: temperature, energy and entropy respectively. I then argue that there are quantities in statistical mechanics that realise these roles: though finding them sometimes requires us to focus on quantum, rather than classical, statistical mechanics. In Chapter 3, I consider the reductive relationship between statistical mechanics and the underlying microdynamics. I demonstrate how the irreversible equations of statistical mechanics can be constructed from the underlying microdynamics using what I label the 'Zwanzig-Zeh-Wallace' framework. Yet this framework uses a procedure called 'coarse-graining' which has been heavily criticised in the literature; so in this Chapter I offer a justification of coarse-graining. One upshot is that the time-asymmetry in statistical mechanics is weakly emergent. In Chapter 4, I consider a question about the domain of applicability of thermal physics. Namely: does it apply to self-gravitating systems, such as elliptical galaxies? Much controversy surrounds this question: some argue yes, others argue no. I deflate the dispute by claiming that thermodynamics does not apply, but statistical mechanics does. Thus, my delineation of thermodynamics and statistical mechanics earlier in this thesis not only makes headway with the question of reduction, but also sheds light on this dispute. I argue that this situation - statistical mechanics, but without thermodynamics - can be understood in terms of a central notion in thermal physics: the thermodynamic limit. But as I also discuss: justifying this idealisation has been philosophically controversial.

Fundando-se em argumentos de equilíbrio e estabilidade termodinâmica, a solubilidade de soluto em um solvente é definida pelo limiar de existência da mistura como sistema homogêneo. De fato, entende-se tal grandeza sobre a coexistência de fases. A noção de solubilidade apresentada é desenvolvida através de modelos simples, que incluem resultados na rede bem como a extensão do modelo de van der Waals ao caso de duas componentes. Desta extrai-se uma condição genérica à observação de mínimos na solubilidade incidente sobre a topologia de seu diagrama de fases e de evidente correspondência física. / Concerning the equilibrium and stability in thermodynamics, the solubility of solute in a solvent is defined as the threshold of the mixture existing as a homogeneous system. Indeed, such quantity meets its meaning when understood on the coexistence surface. The idea of solubility presented is developed following the discussion of simple models, including results on the lattice as well as the van der Waals model extended to include two components. From these results we extract a general condition which connects the occurence of a minimum in solubility to the topological structure of the phase diagram.

Les phénomènes thermoélectriques sont un moyen de convertir directement l’énergie thermique en énergie électrique ; ils sont à ce titre au cœur de nombreuses recherches dans le domaine de l’énergétique. Au-delà de l’optimisation des matériaux constituants les générateurs thermoélectriques, il est également nécessaire de mener une réflexion sur la manière dont ces générateurs sont utilisés. La contribution des contacts thermiques entre le générateur et les réservoirs thermiques est un facteur qui va modifier les conditions de fonctionnement optimales du générateur. En utilisant la notion de courant thermique convectif, développée par Thomson il y a plus de 150 ans, nous généralisons les expressions classiques du fonctionnement à puissance maximum pour le générateur pour ce cas de figure. Nous constatons toutefois que ces conditions se réduisent à une adaptation d’impédance, à la fois thermique et électrique Outre son intérêt pratique, le générateur thermoélectrique est également un système modèle de choix pour étudier la théorie du transport couplé et des phénomènes irréversibles. En utilisant la description donnée par Ioffe de ce système, nous montrons que l’efficacité à maximum de puissance, un coefficient de performance au cœur de la thermodynamique à temps fini, s’exprime comme une fonction relativement simple des paramètres du système. La nouveauté de ce travail repose sur une prise en compte appropriée des dissipations internes associées au processus de conversion d’énergie. Les résultats sont généralisés enfin aux cas d’autres machines thermiques telle que la roue à rochet de Feynman. / Thermoelectric phenomena are a way to directly convert thermal energy into electrical energy; they thus are at the heart of several researches in the field of energy conversion. The optimization of the thermoelectric generators includes materials improvement but a reflection on their working conditions is also mandatory. The contribution of the thermal contacts between the generator and the heat reservoirs is a factor that will change the optimum operating conditions of the generator. Using the concept of convective heat flow, developed by Thomson more than 150 years ago, we generalize the classical expression of maximum power conditions. Moreover, we note that these conditions may be reduced to impedance matching conditions, both thermal and electrical. In addition to its practical interest, the thermoelectric generator is also an ideal model system to study the theory of coupled transport and of irreversible phenomena. Using the description of this system given by Ioffe, we show that the maximum power efficiency, a coefficient of performance at the heart of finite time thermodynamics, expressed as a simple function of the system parameters. The novelty of this work is based on a proper consideration of internal dissipation associated with the energy conversion process. The results are then generalized to other thermal engines such as the Feynman ratchet.

Two applications of Category Theory are considered. The link between them is applications to Physics and more specifically to Entropy. The first research chapter is broader in scope and not explicitly about Physics, although connections to Statistical Mechanics are made towards the end of the chapter. Matroids are abstract structures that describe dependence, and strong maps are certain structure-preserving functions between them with desirable properties. We examine properties of various categories of matroids and strong maps: we compute limits and colimits; we find free and cofree constructions of various subcategories; we examine factorisation structures, including a translation principle from geometric lattices; we find functors with convenient properties to/from vector spaces, multisets of vectors, geometric lattices, and graphs; we determine which widely used operations on matroids are functorial (these include deletion, contraction, series and parallel connection, and a simplification monad); lastly, we find a categorical characterisation of the greedy algorithm. In conclusion, this project determines which aspects of Matroid Theory are most and least conducive to categorical treatment. The purpose of the second research chapter is to provide a categorical framework for generalising and unifying notions of Entropy in various settings, exploiting the fact that Entropy is a monotone subadditive function. A categorical characterisation of Entropy through a category of thermodynamical systems and adiabatic processes is found. A modelling perspective (adiabatic categories) that directly generalises an existing model is compared to an axiomatisation through topological and linear structures (topological weak semimodules), where the latter is based on a categorification of semimodules. Properties of each class of categories are examined; most notably a cancellation property of adiabatic categories generalising an existing result, and an adjunction between the categories of weak semimodules and symmetric monoidal categories. An adjunction between categories of adiabatic categories and topological weak semimodules is found. We examine in which cases each of these classes of categories constitutes a traced monoidal category. Lastly, examples of physical applications are provided. In conclusion, this project uncovers a way of, and makes progress towards, retrieving the statistical formulation of Entropy from simple axioms.

Le lien entre les éléments volatils CO₂-H₂O et la fusion mantellique a depuis maintenant longtemps été illuminé par l’expérimentation. Une large base de données expérimentales existe et souligne l’effet primordial de ces éléments sur l’abaissement des températures de fusion de la péridotite ainsi que sur la composition des liquides magmatiques produits comme une fonction des conditions P – T – fo₂ – composition du système. Néanmoins, la diversité et la complexité de cette base de données peuvent compliquer sa compréhension globale. Dans cette étude, une analyse détaillée de la composition des liquides magmatiques riches en CO₂ et H₂O est réalisée, soulignant notamment une transition non-linéaire et plus ou moins abrupte entre des liquides carbonatitiques et des liquides silicatés. Un modèle thermodynamique est élaboré afin de calculer l’activité de SiO₂ dans les liquides magmatiques riches en CO₂-H₂O (aSiO₂(l)) et coexistant avec un assemblage péridotitique, depuis des termes carbonatitiques jusqu’à des termes basaltiques. L’application de ce modèle dans des conditions de ride océanique prédit la stabilisation des liquides carbonatitiques au démarrage de la fusion redox (liée à la transition graphite/diamant- carbonates) jusqu’à environ 100 km de profondeur, avant d’évoluer plus ou moins abruptement vers des liquides silicatés riche en CO₂. Au niveau des cratons, les kimberlites de Groupe I sont stabilisés en base de lithosphère (~250 km de profondeur), et peuvent être formés à partir d’un plume mantellique. L’épaisseur de cette lithosphère empêche la remontée du plume et la formation des OIB. Afin de décrire plus pleinement les propriétés thermodynamiques du liquide magmatique, un modèle plus complexe (système CMAS-CO₂) est en construction, dont la méthodologie est modifiée par rapport au précédent modèle calculant aSiO₂(l) ; un effort tout particulier est ici mené afin de mieux considérer les incertitudes expérimentales et thermodynamiques. / The link between volatiles (CO₂-H₂O) and mantle melting has so far been illuminated by experiments. A large experimental database exists and emphasizes the importance of volatiles on lowering solidus temperatures of peridotite and modifying the melt composition as a function of P – T – fo₂ – bulk composition. Nevertheless, the diversity and the complexity of this experimental database may complicate its global understanding. In this study, an analysis of CO₂-H₂O-rich melt composition is done, emphasizing the non-linear and more or less abrupt character of the transition between carbonate-rich melts and silicate-rich melts. A thermodynamic model is accomplished to calculate the silica activity in CO₂-H₂O-rich melts coexisting with peridotite assemblage and covering carbonatitic to basaltic terms. Along an oceanic ridge adiabat, the model predicts that carbonatitic melts can be stabilized at the onset of “redox melting” (transition between graphite/diamond-carbonates) to about 100 km depth, before abruptly evolving towards carbonated silicate melts. In cratons, Group I kimberlites are stabilized at the base of the lithosphere (about 250 km depth), and can originate from a mantle plume. The thickness of the lithosphere prevents the plume ascent and the production of OIB. In the aim of describing the melt thermodynamic properties more precisely, a more complex model (system CMAS-CO₂) is under construction, with a modified methodology relative to the previous model of silica activity; a specific effort is here conducted in order to better consider experimental and thermodynamic uncertainties.

Este trabalho procura responder a questão: \"quais as barreiras conceituais que impedem a compreensão da segunda lei da Termodinâmica pelos estudantes? A partir de três questões apresentadas a estudantes do terceiro ano do ensino médio e do primeiro ano do curso superior de licenciatura em física, foram coletadas as respostas produzidas; posteriormente analisadas, permitiram a explicitação de concepções que, confrontadas com as idéias da Termodinâmica clássica, revelaram um raciocínio inadequado. A idéia de sistema centrado no objeto, parece constituir uma barreira conceitual difícil de transpor; assim também ocorre com os conceitos de processo e transformação exibidos pelo senso comum. Tais conceitos são fundamentais para o estabelecimento da Termodinâmica e devem ser pensados no trabalho em sala de aula capaz de produzir conflitos cognitivos com meta a uma mudança conceitual. Por outro lado, numa perspectiva histórica, foi possível identificar alguma ressonância entre as idéias dos estudantes e o desenvolvimento da concepção de calor; focalizamos especialmente as idéias de Carnot e de Clausius ao longo da elaboração das leis da Termodinâmica. O trabalho também identificou lacunas decorrentes da forma como os conteúdos científicos são apresentados na sala de aula e nos livros didáticos o que pode explicar as dificuldades encontradas. Finalmente, o trabalho apresenta subsídios de relevância pedagógica que podem contribuir para a melhoria do ensino da Termodinâmica no nível médio, com atividades especiais que tocam nos pontos conflitantes entre as concepções dos estudantes e o conhecimento científico. / This work aims to answering the following question: what are the conceptual barriers that prevent students from understanding the second law of Thermodynamics ? Starting from three questions that were proposed to third year secondary school and to first year physics teaching university students, the collected answers were analysed and led to an explicitation of conceptions that disclose inadequate reasoning when confronted with the ideas of classical Thermodynamics. The idea of a system centered on the object seems to be a conceptual barrier that is difficult to overcome and the same happens with the concepts of process and change that are usual in commonsense. But these concepts are essential for the fundamentals of Thermodynamics and should be used in class work to create cognitive conflicts aiming to a conceptual change. On the other hand, from a historical perspective, it was possible to identify some of the students ideas in the development of the concept of heat particularly in the development of the ideas of Carnot and Clausius in the elaboration of the laws of thermodynamics. The work has also identified gaps resulting from the way scientific contents are presented in the classroom and in textbooks that could explain the students difficulties. At last, the work presents pedagogically relevant contributions that may be helpful in teaching thermodynamics in secondary schools with special activities that touch points that are conflicting between students conceptions and scientific knowledge.

Submitted by Jean Medeiros (jeanletras@uepb.edu.br) on 2016-04-05T14:22:52Z No. of bitstreams: 1 PDF - João Bosco Abrantes Júnior.pdf: 1978510 bytes, checksum: dec0624e2853975f721a663b9f203b6a (MD5) / Approved for entry into archive by Secta BC (secta.csu.bc@uepb.edu.br) on 2016-04-12T22:53:14Z (GMT) No. of bitstreams: 1 PDF - João Bosco Abrantes Júnior.pdf: 1978510 bytes, checksum: dec0624e2853975f721a663b9f203b6a (MD5) / Made available in DSpace on 2016-04-12T22:53:51Z (GMT). No. of bitstreams: 1 PDF - João Bosco Abrantes Júnior.pdf: 1978510 bytes, checksum: dec0624e2853975f721a663b9f203b6a (MD5) Previous issue date: 2015-09-25 / The insertion of computational tools to assist in the teaching of physics is something increasingly required due to the new company's profile, school and student. Computing resources can promote the teaching and learning of physics, new ways of teaching, learning and thinking considering the various features it can offer. As an example, the virtual labs available on the internet that allow the development of virtual experiences promoting easy viewing of the phenomena studied. In this work, we aimed, from the production of didactic material with animated images, called Virtual Interactive Animations, of Thermodynamics content and, through experiences in the classroom, test and investigate the scope and limits. As methodological approach we have adopted the qualitative approach and the developments of the investigation, were used the following forms: exploratory, descriptive and case study. As for the case study, this research is shrouded the process of assessing the validity of a teaching tool that is the application of simple virtual interactive objects, ie, the Virtual Interactive Animations on thermodynamics content. The choice of Thermodynamics content took place in this part of the menu of the course and / or curriculum component in which the author is a teacher, learning disability presented by the students, noted for low income, verified by the notes below average, and by having some abstract concepts in laws and phenomena. Virtual Interactive Animations, even with its limitations, allowed a change in the way of teaching and learning by creating a favorable environment for teaching and learning. / A inserção de ferramentas computacionais para auxiliar no ensino da Física é algo cada vez mais exigido devido ao novo perfil de sociedade, escola e estudante. Os recursos computacionais podem promover no processo de ensino e aprendizagem da Física, novas formas de ensinar, aprender e pensar tendo em vista os mais variados recursos que ela pode oferecer. Como exemplo, podemos citar os laboratórios virtuais disponíveis na internet que permitem o desenvolvimento de experiências virtuais promovendo uma fácil visualização dos fenômenos estudados. Neste trabalho, tivemos como objetivo, a partir da produção de um material didático com imagens animadas, denominadas Animações Virtuais Interativas, de conteúdos da Termodinâmica e, através de experiências na sala de aula, testar e investigar o alcance e seus limites. Como percurso metodológico adotamos a abordagem qualitativa e para os desdobramentos da investigação, foram usadas as seguintes formas: exploratória, descritiva e estudo de caso. Quanto ao estudo de caso, nesta pesquisa, está envolto ao processo de avaliação da validade de um instrumento pedagógico que é a aplicação dos objetos interativos virtuais simples, ou seja, as Animações Virtuais Interativas no conteúdo de termodinâmica. A escolha do conteúdo da Termodinâmica deu-se por este fazer parte da ementa do curso e/ou componente curricular em que o autor é professor, pela dificuldade de aprendizagem apresentada pelos estudantes, notado pelo baixo rendimento, verificado pelas notas abaixo da média, e por possuir alguns conceitos abstratos nas leis e fenômenos. As Animações Virtuais Interativas, mesmo com suas limitações, permitiram uma mudança na forma de ensinar e aprender criando um ambiente favorável para o processo de ensino e aprendizagem.

Neste trabalho, realizou-se o estudo que permitiu a otimização termodinâmica das seções binárias pertencentes ao diagrama de fase ternário do sistema LiF-GdF3-LuF3, para tanto o programa FactSage foi empregado na simulação computacional. Assim, o comportamento de fusão das misturas destes compostos foi elucidado, o que representa uma contribuição inovadora para o conhecimento das propriedades físicas e químicas destes materiais. Em particular, determinou-se a faixa de composições nas quais as soluções sólidas de LiGdxLu1-xF4 e GdxLu1-xF3 podem ser obtidas diretamente da fase líquida. Neste trabalho as três secções binárias, LiF-GdF3, LiF-LuF3 e GdF3-LuF3 foram reavaliadas experimentalmente utilizando a calorimetria exploratória diferencial para a obtenção de dados mais precisos de temperatura versus composição, uma vez que foi possível minimizar a contaminação das amostras com compostos de oxigênio. A capacidade calorífica e outros dados calorimétricos foram também determinados experimentalmente e comparados com os existentes na literatura. Os termos da energia livre de Gibbs de excesso para as fases representadas como soluções, os quais descrevem os efeitos de interação não ideal entre os dois fluoretos nestas fases, foram expressos com sucesso pela modelo polinomial Redlich-Kister. Finalmente, o caminho de solidificação no diagrama de fase ternário LiF-GdF3-LuF3 pôde ser extrapolado de acordo com o formalismo de Kohler-Toop. Assim, pela primeira vez, a interação ternária entre os compostos LiF, GdF3 e LuF3 foi determinada. / In this work, it was carried out the study that allowed the thermodynamic optimization of the binary sections belonging to the ternary phase diagram of the LiF-GdF3-LuF3 system, for this purpose the FactSage software was used in the computational simulation. Thus, the melting behavior of the mixture of these compounds has been elucidated, which represents an innovative contribution to the knowledge of the physical and chemical properties of these materials. In particular, it was determined the composition ranges in which the solid solutions of LiGdxLu1-xF4 and GdxLu1-xF3 can be obtained directly from the liquid phase. In this work the three binary sections, LiF-GdF3, LiF-LuF3 and GdF3-LuF3, were evaluated using differential scanning calorimetry to obtain more accurate data of temperature versus composition, since it was possible to minimize the contamination of the samples due to oxygen compounds. The heat capacity and other calorimetric data were experimentally determined and compared with those cited in the literature. The terms of the Gibbs free excess energy for the solution phases, which describe the non ideal interaction effects between the two fluorides at these phases, were expressed by the Redlich-Kister polynomial model. Finally, the solidification path in the ternary phase diagram LiF-GdF3-LuF3 could be extrapolated according to the Kohler-Toop formalism. Thus, for the first time, the interaction between the ternary compounds LiF, GdF3 and LuF3 was determined.