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Não recebi financiamento The Lusternik-Schnirelmann category associates a positive integer to each topological space. This number is an important invariant in algebraic topology, critical point theory and symplectic geometry. In this dissertation we present the theory of Lusternik-Schnirelmann category, compute the category of several topological spaces and provide some reformulations of the category. In addition, we show two applications of Lusternik-Schnirelmann category to other areas of mathematics. The first one is a geometric application proving that a convex body in Euclidean space of dimension n admits at least n binormal chords. The second application relates the category to topological complexity in the motion planning problem. A categoria de Lusternik-Schnirelmann associa a cada espaço topológico um número inteiro positivo, sendo este número um invariante importante na topologia algébrica, teoria dos pontos críticos e geometria simplética. Nesta dissertação, apresentamos a teoria da categoria de Lusternik-Schnirelmann, computamos a categoria de vários espaços topológicos e fornecemos algumas reformulações da categoria. Além disso, exibimos duas aplicações da categoria de Lusternik-Schnirelmann em outras áreas da matemática. A primeira, é uma aplicação geométrica, que consiste na demonstração que um corpo convexo no espaço euclidiano de dimensão n, admite pelo menos n cordas binormais. A segunda aplicação, relaciona a categoria à complexidade topológica no problema de planejamento de movimentos.

This article focus on analysing the traffic safety at a BR-020 segment, located in Distrito Federal. To achieve this goal, the highway, accident types and causes were characterized. Using the accidents data provided by the Federal Highway Police Department, it was possible to georeference them. Three methods that identify critical segments were applied to the highway: DNIT methodology, Ministry of Transportation methodology and Meneses’ methodology. After comparing the results from each methodology, flaws were found within each method, being the Meneses technique the most complete. Upon studying the critical highway segments, defective points were identified and improvements were suggested. Este artículo tiene como objetivo analizar el tramo de la carretera BR-020, inserto en el Distrito Federal, bajo el aspecto de seguridad vial. Para lograr este objetivo, se realizó una caracterización de la carretera, los tipos y causas de accidentes, así como su georreferenciación a partir de los datos de accidentes proporcionados por la Policía Federal de Carreteras (DPRF). Se aplicaron a la carretera BR-020 tres métodos de identificación de sitios concentradores de accidentes (metodologías del DNIT, Ministerio de Transportes y Meneses) para la ubicación de tramos críticos en la misma. De la comparación de los resultados obtenidos por cada método, se encontraron deficiencias en las metodologías adoptadas, en las que la metodología propuesta por Meneses fue considerada la más completa entre las tres. Y, mediante la identificación de los tramos críticos comunes a los tres métodos, se realizó un análisis de seguridad para detectar las deficiencias presentes en la vía, así como la propuesta de mejoras con el fin de mejorar la seguridad vial, la calidad de vida y la economía. del Distrito Federal. O presente artigo tem como objetivo analisar o trecho da rodovia BR – 020, inserida no Distrito Federal, sob o aspecto de segurança viária. A fim de atingir esse objetivo realizou-se uma caracterização da rodovia, os tipos e as causas dos acidentes assim como seus georreferenciamentos a partir dos dados de acidentes fornecidos pelo Departamento da Polícia Rodoviária Federal (DPRF). Três métodos de identificação de locais concentradores de acidentes (metodologias do DNIT, do Ministério dos Transportes e de Meneses) foram aplicados à rodovia BR-020 para a localização dos trechos críticos nesta. A partir da comparação dos resultados obtidos por cada método, constataram-se deficiências nas metodologias adotadas, em que a metodologia proposta por Meneses foi considerada a mais completa dentre as três. E, através da identificação dos segmentos críticos comuns aos três métodos, realizou-se a análise de segurança ao detectar as deficiências presentes na via, assim como a proposição de melhorias a fim de aperfeiçoar a segurança viária, qualidade de vida e economia do Distrito Federal.

CNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico Neste trabalho, trataremos sobre curvas que possuem curvatura geodésica constante em variedades bidimensionais. Assim, através do artigo em [13]; "A note on constant geodesic curvature curves on surfaces" publicado em 2009 no jornal: Annales de l’Institut Henri Poincaré C, Analyse Non Linéaire, falaremos com mais detalhes sobre a curvatura geodsiéca e de curvas especiais que possuem essas curvaturas respectivamente. O teorema principal dessa dissertação mostra que se existe uma sequência de círculos geodésicos que convergem para um dado ponto p ∈ M então esse p é um ponto singular da aplicação de Gauss. In this work, we will deal with curves that have constant geodetic curvature in two-dimensional varieties. Thus, through the article in [13], "A note on constant geodesic curvature curves on surfaces" published in 2009 in the newspaper: Annales de l’Institut Henri Poincaré C, Analyze Non Linéaire, we will talk in more detail about geodesic curvature and special curves that have these curvatures respectively. The main theorem of this dissertation shows that if there is a sequence of geodesic circles that converge for a given point, this is a singular point in the Gaussian application.

In this work, we study some results that guarantee uniqueness of critical points for a differential Fr´echet functional defined in a normed space and we do an application to a elliptic quasilinear problem that appears in physics. The main tools used in the application are variational methods, namely, minimization arguments, regularity theory and Maximum Principle. We accentuate that the abstract results we present can be applied to a greater number of problems arising from Mathematical Physics. Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES Neste trabalho, estudamos alguns resultados que garantem a unicidade de pontos críticos para um funcional Fréchet diferenciável definido num espaço normado e fazemos uma aplicação a um problema elíptico quase linear que surge na Física. As principais ferramentas usadas na aplicação são métodos variacionais, a saber, argumentos de minimização, teoria de regularidade e Princípio de Máximo. Salientamos que os resultados abstratos que apresentamos podem ser aplicados em número maior de problemas advindos da Física Matemática.

Resumo Embora a criação de abelhas sem ferrão (meliponicultura) no Semiárido brasileiro tenha se apresentado como uma ferramenta aliada do desenvolvimento sustentável, a avaliação da sustentabilidade dessa atividade nesse espaço geográfico ainda precisa ser realizada como contribuições para torná-la uma prática mais atrativa e promissora. Diante dessa questão, o objetivo deste artigo é identificar pontos críticos de agroecossistemas melíponas no Semiárido norte-rio-grandense do Brasil. Para isso, aplicaram-se os dois primeiros passos da ferramenta Marco para a Avaliação de Sistemas de Manejo de Recursos Naturais Incorporando Indicadores de Sustentabilidade (MESMIS) em 15 unidades de análise. Os dados foram coletados entre junho e setembro de 2014 e sistematizados a partir de fontes bibliográficas, aplicação de entrevistas semiestruturadas com os meliponicultores, mensuração do uso e ocupação do solo de cada agroecossistema e observação direta dos pesquisadores. Os resultados evidenciam sete pontos críticos (vegetação, água, clima, organização, capacitação, diversidade e manejo). Com isso, este estudo revela aspectos positivos e negativos da criação de abelhas sem ferrão, sendo um dos pioneiros retratos na busca pela avaliação da sustentabilidade da meliponicultura no Semiárido brasileiro. Abstract Although the creation of stingless bees in the brazilian Semiarid has presented like a sustainable activity for development this region, its evaluation of sustainability in this geographical area still needs of best contributions to make it a practice more and more attractive and promising. Based on above writing, the objective of this article is to identify critical points of meliponas agroecosystems in the Semiarid of Rio Grande do Norte state of Brazil. To achieve this goal, was applied the first two steps of tool Marco for the Evaluation of Natural Resource Management Systems Incorporating Sustainability Indicators (MESMIS) in 15 analysis units. The data were collected between June and September of 2014 and systematized from literature sources, application of semi-structured interviews with beekeepers, measurement of land use and occupation of each agroecosystem and direct observation of the researchers. The results show seven critical points (vegetation, water, climate, diversity, management, organization and training). With this support, this study reveals positive and negative aspects of the creation of stingless bees, being one of the portraits pioneers in the quest for sustainability assessment of beekeeping in brazilian Semiarid.

We investigate the occurrence of multicritical points under pressure and magnetic field in a model that describes two 5 f bands (of either α or β characters), which hybridize with a single itinerant conduction band. The 5 f electrons interact through Coulomb and exchange terms. The antiferromagnetic (AF) order parameter is a Néel vector, which is assumed to be fixed by an Ising anisotropy. The applied magnetic field is transverse to the anisotropy axis. Without field, our results for the temperature-pressure phase diagram show that at low temperatures a first-order phase transition occurs between two distinct antiferromagnetic phases, AF1 and AF2, as the pressure is increased. The two phases are characterized by the gaps of bands α and β given by α and β , respectively. The AF1 phase occurs when β > α > 0, while in the AF2 phase the gaps satisfy α > β > 0. The application of a magnetic field produces a drastic change in the phase diagram. The AF1 and AF2 phases separate, with the latter acquiring a dome shape that is eventually suppressed for large values of the applied field. The evolution of the phase diagram under pressure, without and with magnetic field, shows the presence of multicritical points. Our results show that the evolution of these multicritical points by the simultaneous application of pressure and magnetic field is also drastic, with the suppression of some multicritical points and the emergence of others. We believe that these results may have relevance for the growing field of multicritical points (classical and quantum) in the physics of uranium compounds.

Water, the substance of life, is known for its myriad of anomalous properties, whose origins are still the subject of intense debates. In order to provide a different insight into this problem, we show how its density anomaly can be reproduced using a quantum simulator. In particular, we demonstrate that the Bose-Hubbard model, a paradigm system in quantum mechanics, exhibits an increase in density with temperature at fixed pressure in the regular fluid regime and in the superfluid phase. We propose that the mechanism underlying the anomalies is related to zero-point entropies and ground-state phase transitions. A connection with the typical experimental scales and setups including confinement effects is also addressed. In this scenario, such finding opens a pathway for theoretical and experimental studies of waterlike anomalies in the area of ultracold quantum gases.

Even though the Hubbard model is one of the most fundamental models of highly correlated electrons, analytical and numerical data describing its thermodynamics at nonzero magnetization are relatively scarce. We present a detailed investigation of the thermodynamic properties for the one dimensional repulsive Hubbard model in the presence of an arbitrary magnetic field for all values of the filling fraction and temperatures as low as $T \sim 0.005\, t.$ Our analysis is based on the system of integral equations derived in the quantum transfer matrix framework. We determine the critical exponents of the quantum phase transitions and also provide analytical derivations for some of the universal functions characterizing the thermodynamics in the vicinities of the quantum critical points. Extensive numerical data for the specific heat, susceptibility, compressibility, and entropy are reported. The experimentally relevant double occupancy presents an interesting doubly nonmonotonic temperature dependence at intermediate values of the interaction strength and also at large repulsion and magnetic fields close to the critical value. The susceptibility in zero magnetic field has a logarithmic singularity at low temperatures for all filling factors similar to the behavior of the same quantity in the XXX spin chain. We determine the density profiles for a harmonically trapped system and show that while the total density profile seems to depend mainly on the value of chemical potential at the center of the trap the distribution of phases in the inhomogeneous system changes dramatically as we increase the magnetic field., Comment: 26 pages, 23 figures, RevTeX 4.1

Dissertação de mestrado em Medicina Veterinária apresentada à Universidade de Trás-os-Montes e Alto Douro

RESUMO Objetivou-se com a presente revisão, reunir aporte teórico, acerca da legislação e ferramentas de gestão no controle de qualidade da matéria-prima na fabricação de ração para animais de produção, descrevendo a regulamentação e fiscalização nos processos envolvidos, ressaltando a importância que tais procedimentos exercem no resultado final do produto. Assim, evidencia-se que o controle de qualidade da matéria-prima é essencial a fim de assegurar a garantia da inocuidade de um produto final de confiança, que atenda às exigências do mercado e consequentemente dos animais, que se aproxime ao máximo das especificações ou padrões estabelecidos para o qual fora criado e que atenda à legislação vigente e às inspeções dos órgãos federais ligados ao setor. Fazendo-se imprescindível o uso de tais ferramentas de gestão na qualidade e segurança dos alimentos oferecidos aos animais de produção. Em que, as Boas Práticas de Fabricação e o Procedimento Operacional Padrão são pré-requisitos essenciais à implantação da Análise de Perigo e Pontos Críticos de Controle. ABSTRACT The objective of this review was to gather theoretical knowledge about legislation and management tools in the quality control of raw material in the production of feed for production animals, describing the regulation and inspection in the processes involved, highlighting the importance that such procedures in the final product result. Thus, it is evident that the quality control of the raw material is essential in order to guarantee the safety of a reliable final product, which meets the market and consequently the animal requirements, which is close to the specifications or standards established for which it was created and that complies with current legislation and inspections of federal agencies related to the sector. It is essential to use such management tools in the quality and safety of food offered to production animals. In which, Good Manufacturing Practices and Standard Operating Procedures are essential prerequisites for the implementation of Hazard Analysis and Critical Control Points. RESUMEN La presente revisión tuvo como objetivo, reunir el aporte teórico, acerca de la legislación y herramientas de gestión en el control de calidad de la materia prima en la fabricación de raciones para animales de producción, describiendo la reglamentación y fiscalización en los procesos involucrados, resaltando la importancia que tales procedimientos ejercen en el resultado final del producto. Así, se evidencia que el control de calidad de la materia prima es esencial para asegurar la inocuidad de un producto final de confianza, que atienda a las exigencias del mercado y consecuentemente de los animales, que se aproxime al máximo de las especificaciones o patrones establecidos para el cual fue creado y que atienda a la legislación vigente y a las inspecciones de los órganos federales ligados al sector. Se hace imprescindible el uso de tales herramientas de gestión en la calidad y seguridad de los alimentos ofrecidos a los animales de producción. En que, las Buenas Prácticas de Fabricación y el Procedimiento Operativo Estándar son prerrequisitos esenciales para la implantación del Análisis de Peligros y Puntos Críticos de Control.

Submitted by Luiz Cesar Maranho (lc-maranho@bol.com.br) on 2018-10-11T20:16:50Z No. of bitstreams: 1 Dissertação Final.pdf: 1883342 bytes, checksum: 85a25606a3113b39d6d4354dcaa161d8 (MD5) Approved for entry into archive by Elza Mitiko Sato null (elzasato@ibilce.unesp.br) on 2018-10-15T12:39:20Z (GMT) No. of bitstreams: 1 maranho_lc_me_sjrp.pdf: 5069791 bytes, checksum: 2501e6acc67bdd7103eb807f326a4c0b (MD5) Made available in DSpace on 2018-10-15T12:39:20Z (GMT). No. of bitstreams: 1 maranho_lc_me_sjrp.pdf: 5069791 bytes, checksum: 2501e6acc67bdd7103eb807f326a4c0b (MD5) Previous issue date: 2018-08-20 O mosquito Aedes aegypti é o principal vetor responsável por diversas arboviroses como a dengue, a febre amarela, o vírus zika e a febre chikungunya. Devido a sua resistência, adaptabilidade e proximidade ao homem, o Aedes aegypti é atualmente um dos maiores problemas de saúde pública no Brasil e nas Américas. Mesmo com os avanços e investimentos em pesquisas com vacinas, monitoramento, campanhas educativas e diversos tipos de controle deste vetor, ainda não existe um método eficaz para controlar e erradicar o mosquito. Portanto, esse trabalho destina-se ao auxílio na criação de estratégias para controlar esse agente transmissor, mediante a análise do espaço de estados e a estabilidade assintótica de uma dinâmica não linear para controle populacional do Aedes aegypti via a técnica de linearização de Lyapunov, além de apresentação de formas de prevenção e combate aos criadouros do mosquito. A dinâmica não linear proposta é uma dinâmica simplificada obtida de um modelo não linear existente na literatura, proposto por Esteva e Yang em 2005 e se baseia no ciclo de vida do mosquito, que é dividido em duas fases: fase imatura ou aquática (ovos, larvas e pupas) e fase alada (mosquitos adultos). Na fase adulta, os mosquitos são divididos em machos, fêmeas imaturas e fêmeas fertilizadas, sendo que a dinâmica proposta nesta dissertação de mestrado é baseada nos estudos efetuados por Reis desde 2016, obtendo um modelo simplificado no qual a soma das densidades das populações de fêmeas imaturas e fêmeas fertilizadas serão consideradas como fêmeas adultas. The mosquito Aedes aegypti is the main vector responsible for several arboviruses such as dengue fever, yellow fever, zika virus and chikungunya fever. Due to its resistance, adaptability and proximity to humans, Aedes aegypti is currently one of the major public health problems in Brazil and the Americas. Even with the advances and investments in research with vaccines, monitoring, educational campaigns and various types of control of this vector, there is still no effective method to control and eradicate the mosquito. Therefore, this work is intended to aid in the creation of strategies to control this transmitting agent by analyzing the state space and the asymptotic stability of a nonlinear dynamics for population control of Aedes aegypti via the Lyapunov linearization technique to present ways of preventing and combating mosquito breeding sites. The proposed nonlinear dynamics is a simplified dynamics obtained from a nonlinear model existing in the literature, proposed by Esteva and Yang in 2005 and based on the life cycle of the mosquito, which is divided into two phases: immature or aquatic phase (eggs, larvae and pupae) and winged phase (adult mosquitoes). In the adult phase, mosquitoes are divided into males, immature females and fertilized females, and the dynamics proposed in this dissertation is based on studies carried out by Reis since 2016, obtaining a simplified model in which the sum of the densities of the populations of females immature and fertilized females will be considered as adult females.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Given the current economic situation in Brazil, an efficient financial management, is more easily achieved if they are identified as priorities of future investments. In this context, the classification of the regional road network according to accidentality is fundamental in the definition of intervention priorities. Thus, this paper, in general, proposes to perform an analysis of the evolution of the accidentality of the road network of the central region of the state of São Paulo (DR-4 DER-SP), between the periods of 2010 to 2014. From the object of study, the data on road accidents were collected; These data were analyzed and treated in order to produce the road network in GIS platform. Then, the appropriate methodologies were defined to obtain the blackspots of the DR-4 road network. With the results obtained, the blackspots of the central road network of the State of São Paulo were identified through two methods, the accident rate and the severity rate, to compare the methods used. Thus, with the identification of these blackspots and with the series of the evolution of accidentality, it is possible to intervene on the highways to reduce the number of accidents in the region. Tendo em conta a atual conjuntura econômica do país, uma gestão financeira eficiente poderá ser mais facilmente alcançada se forem identificadas as prioridades de futuros investimentos. Neste contexto, a classificação da rede viária regional em função da acidentalidade é fundamental na definição de prioridades de intervenção. Assim este trabalho, de modo geral, tem como objetivo principal realizar uma análise da evolução da acidentalidade da malha rodoviária da região central do Estado de São Paulo (DR-4 DER-SP), compreendido entre os períodos de 2010 a 2014. A partir do objeto de estudo foram levantados os dados sobre acidentalidade viária; esses dados foram analisados e tratados para assim se produzir a malha viária em plataforma SIG. Em seguida, foram definidas as metodologias adequadas para a obtenção dos pontos críticos da malha rodoviária do DR-4. Com os resultados obtidos identificaram-se os pontos críticos da malha central do Estado de São Paulo através de dois métodos, a taxa de acidentes e a taxa de severidade, para comparação dos métodos utilizados. Assim, com a identificação desses pontos e com a série da evolução da acidentalidade é possível fazer uma intervenção nas rodovias para a redução dos números de acidentes na região.

We investigate the universal thermodynamics of the two-component one-dimensional Bose gas with contact interactions in the vicinity of the quantum critical point separating the vacuum and the ferromagnetic liquid regime. We find that the quantum critical region belongs to the universality class of the spin-degenerate impenetrable particle gas which, surprisingly, is very different from the single-component case and identify its boundaries with the peaks of the specific heat. In addition, we show that the compressibility Wilson ratio, which quantifies the relative strength of thermal and quantum fluctuations, serves as a good discriminator of the quantum regimes near the quantum critical point. Remarkably, in the Tonks-Girardeau regime the universal contact develops a pronounced minimum, reflected in a counterintuitive narrowing of the momentum distribution as we increase the temperature. This momentum reconstruction, also present at low and intermediate momenta, signals the transition from the ferromagnetic to the spin-incoherent Luttinger liquid phase and can be detected in current experiments with ultracold atomic gases in optical lattices., Comment: 5+2 pages, RevTeX 4.1

RESUMO Neste trabalho descreve-se de maneira detalhada, tanto analíticamente quanto numericamente, a detecção e a classificação de pontos críticos na trajetória primária de equilíbrio de sistemas estruturais. Utiliza-se a Formulação Lagrangiana Total para descrever a cinemática de um elemento de barra bi-articulado 3D. Através desta formulação obtém-se o vetor de forças internas e a matriz de rigidez tangente que levam em conta os efeitos da não linearidade geométrica. Assume-se um modelo constitutivo linear elástico para o estado uniaxial de tensão-deformação, usando a deformação de Green-Lagrange e a tensão axial do segundo tensor de Piola-Kirchhoff que são energéticamente conjugados. Como estudo de caso apresenta-se um sistema físico simples com três graus de liberdades composto por duas barras bi-articuladas 3D e uma mola linear. Por fim, determinam-se as condições geométricas e físicas para a coalescência entre os pontos limites e de bifurcação. ABSTRACT Using both analytical and numerical approaches, this paper describes in detail the detection and classification of critical points in the primary equilibrium path of structural systems. The Total Lagrangian formulation is employed to describe the kinematics of a biarticulated prismatic 3D bar element. With this formulation, the internal force vector and the tangent stiffness matrix including the geometric nonlinearity effects are obtained. An elastic linear constitutive model is assumed for the uniaxial stress-strain state. Such model uses the Green-Lagrange strain tensor and the second Piola-Kirchhoff axial stress tensor which are energetically conjugate tensors. As a study case, the article presents a simple structural system with three degrees of freedom made up of two bi-articulated prismatic 3D bars and a linear spring. Finally, the geometrical and physical conditions for the coalescence between limit and bifurcation points are determined.

We investigate the short-time universal behavior of the two-dimensional Ashkin-Teller model at the Baxter line by performing time-dependent Monte Carlo simulations. First, as preparatory results, we obtain the critical parameters by searching the optimal power-law decay of the magnetization. Thus, the dynamic critical exponents θm and θp, related to the magnetic and electric order parameters, as well as the persistence exponent θg, are estimated using heat-bath Monte Carlo simulations. In addition, we estimate the dynamic exponent z and the static critical exponents β and ν for both order parameters. We propose a refined method to estimate the static exponents that considers two different averages: one that combines an internal average using several seeds with another, which is taken over temporal variations in the power laws.Moreover, we also performed the bootstrapping method for a complementary analysis. Our results show that the ratio β/ν exhibits universal behavior along the critical line corroborating the conjecture for both magnetization and polarization.

In this work we first study some interesting generalizations of the famous inequality Sobolev to limited domains. Then, we will study the existence of positive solution for a nonlinear elliptic equation on a certain condition Neumann, by imposing certain restricitive condition in the nonlinearity. To we consider more general hypotheses we will assume conditions on the boundary of domain. Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES Neste trabalho, estudaremos primeiramente algumas generaliza¸c˜oes interessantes da famosa desigualdade de Sobolev para dom´ınios limitados. Em seguida, iremos estudar a existˆencia de solu¸c˜oes positivas para uma equa¸c˜ao el´ıptica n˜ao linear, sob uma certa condi¸c˜ao de Neumann e impondo algumas condi¸c˜oes restritivas sobre a n˜ao linearidade. Para considerarmos hip´oteses mais gerais, assumiremos condi¸c˜oes na fronteira do dom˜Anio.

Investigamos transições de fase quânticas em condensados de Bose-Einstein unidimensionais em rede, descritos pelo modelo de Bose-Hubbard e generalizações. Nosso foco principal é na transição de localização induzida tanto por desordem aleatória (modelo de Anderson) quanto por potenciais incomensuráveis (modelo de Aubry-André). Por meio de diagonalização exata do Hamiltoniano, calculamos fração de superfluído (parâmetro apropriado para sinalizar localização), emaranhamento, gap de energia, compressibilidade, e fidelidade do estado fundamental. Complementando-se mutuamente, essas quantidades dão claras indicações da ocorrência de transições de fases quânticas, mesmo em redes pequenas. Analisamos em detalhe efeitos de tamanho finito, obtendo expoentes críticos para a transição de localização de Anderson, tanto no limite não interagente quanto com interação fraca. Também estudamos a transição entre as fases isolante de Mott e vidro de Bose para interação forte, que pode ser tratada com um limite de baixa mobilidade (pequena amplitude de hopping). Adicionalmente, estudamos propriedades topológicas de um modelo de Aubry-André unidimensional generalizado, e sua inter-relação com a “desordem”, com especial atenção para a estabilidade de certos estados topológicos frente a uma perturbação periódica incomensurável. We investigate quantum phase transitions in one-dimensional Bose-Einstein condensates on a lattice, described by the Bose-Hubbard model and generalizations. Our main focus is on the localization transition induced by either random disorder (the Anderson model) or incommensurate potentials (the Aubry-Andr´e model). By means of exact diagonalization of the Hamiltonian, we calculate superfluid fraction (an appropriate parameter to signal localization), entanglement, energy gap, compressibility, and ground-sate fidelity. Complementing each other, these quantities provide clear signatures of quantum phase transitions, even for small lattices. We analyze finite-size effects in detail, obtaining critical exponents for the Anderson-localization transition, both in the non-interacting limit and with weak interaction. We also study the transition between the Mott-insulator and Bose-glass phases for strong interactions, which can be treated as a low-mobility (small-hopping) limit. In addition, we study topological properties of a generalized one-dimensional Aubry-André model, and their interplay with “disorder”, focusing on the robustness of certain topological states against a periodic incommensurate perturbation.

CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior Neste trabalho estudamos a existência de soluções para a seguinte classe de problemas: FÓRMULA DISPONÍVEL NO TEXTO COMPLETO a qual é um modelo matemático surgido da teoria de crescimento epitaxial. A procura de soluções depende das condições de fronteira impostas e a classe de domínio a considerar. In this work we will study the existence of solutions for the following class of problems: FÓRMULA DISPONÍVEL NO TEXTO COMPLETO which is a mathematical model arisen in the theory of epitaxial growth. Finding solutions depends on the imposed boundary conditions and the class of the domain to be considered.

A dissertação para conclusão do curso de Engenharia Química e Bioquímica e obtenção do grau de mestre foi realizada no complexo industrial Sapec Agro Portugal, S.A., mais concretamente na instalação piloto de síntese, no período entre dia 9 de Setembro de 2013 e dia 14 de Março de 2014. O tema proposto pela empresa, Síntese orgânica à escala piloto – parâmetros relevantes e implicação no processo, pretende que se realize uma reacção de epimerização e purificação de deltametrina crude em deltametrina técnica, em condições GMP, utilizando equipamentos presentes na instalação piloto de síntese. Este trabalho pretende ainda determinar os pontos críticos do processo e validação do mesmo, realizando três ensaios industriais de validação na instalação piloto de síntese. Com a aposta da empresa em medicamentos veterinários torna-se necessário o tratamento e purificação de matérias activas, permitindo um fornecimento de produtos em conformidade com a legislação farmacêutica em vigor. A determinação da conformidade do produto é realizada com recurso ao método de análise por cromatografia gasosa (GC), quantificando a percentagem de isómero R e deltametrina presentes em amostras retiradas ao longo do processo. A análise dos resultados obtidos permite concluir que o processo de epimerização e purificação de deltametrina crude em deltametrina técnica é um processo viável e garante as condições necessárias à utilização de deltametrina técnica como matéria-prima em formulações veterinárias. Foram ainda realizadas algumas optimizações ao processo de fabrico existente e proposto trabalho futuro a realizar na instalação piloto de síntese

We have investigated the dynamic critical behavior of the two-dimensional Z(5)-symmetric spin model by using short-time Monte Carlo (MC) simulations. We have obtained estimates of some critical points in its rich phase diagram and included, among the usual critical lines the study of first-order (weak) transition by looking into the order-disorder phase transition. In addition, we also investigated the soft-disorder phase transition by considering empiric methods. A study of the behavior of β/νz along the self-dual critical line has been performed and special attention has been devoted to the critical bifurcation point, or Fateev-Zamolodchikov (FZ) point. First, by using a refinement method and taking into account simulations out of equilibrium, we were able to localize parameters of this point. In a second part of our study, we turned our attention to the behavior of the model at the early stage of its time evolution in order to find the dynamic critical exponent z as well as the static critical exponents β and ν of the FZ point on square lattices. The values of the static critical exponents and parameters are in good agreement with the exact results, and the dynamic critical exponent z ≈ 2.28 very close to the four-state Potts model (z ≈ 2.29).

We show that in order to describe the isotropic-nematic transition in stripe forming systems with isotropic competing interactions of the Brazovskii class it is necessary to consider the next to leading order in a 1/N approximation for the effective Hamiltonian. This can be conveniently accomplished within the self-consistent screening approximation. We solve the relevant equations and show that the self-energy in this approximation is able to generate the essential wave vector dependence to account for the anisotropic character of two-point correlation function characteristic of a nematic phase., 8 pages, 4 figures

The relation between liquid-liquid phase transitions andwaterlike density anomalies in core-softened potentials of fluids was investigated in an exactly solvable one-dimensional lattice model and in a three-dimensional fluid with a Fermi-like potential, the latter by molecular dynamics. Both systems were shown to present three liquid phases, two liquid-liquid phase transitions closely connected to two distinct regions of anomalous density increase. We propose that an oscillatory behavior observed on the thermal expansion coefficient as a function of pressure can be used as a signature of the connection between the liquid-liquid phase transition and density anomaly.

We calculate the Wilson ratio of the one-dimensional Fermi gas with spin imbalance. The Wilson ratio of attractively interacting fermions is solely determined by the density stiffness and sound velocity of pairs and of excess fermions for the two-component Tomonaga-Luttinger liquid phase. The ratio exhibits anomalous enhancement at the two critical points due to the sudden change in the density of states. Despite a breakdown of the quasiparticle description in one dimension, two important features of the Fermi liquid are retained; namely, the specific heat is linearly proportional to temperature, whereas the susceptibility is independent of temperature. In contrast to the phenomenological Tomonaga-Luttinger liquid parameter, the Wilson ratio provides a powerful parameter for testing universal quantum liquids of interacting fermions in one, two, and three dimensions.

In this work, we study the critical behavior of second-order points, specifically the Lifshitz point (LP) of a three-dimensional Ising model with axial competing interactions [the axial-next-nearest-neighbor Ising (ANNNI) model], using time-dependent Monte Carlo simulations. We use a recently developed technique that helps us localize the critical temperature corresponding to the best power law for magnetization decay over time: (M)m0=1 ∼ t −β/νz, which is expected of simulations starting from initially ordered states. We obtain original results for the dynamic critical exponent z, evaluated from the behavior of the ratio F2(t ) = (M2) m0=0/ (M)2 m0=1 ∼ t 3/z, along the critical line up to the LP. We explore all the critical exponents of the LP in detail, including the dynamic critical exponent θ that characterizes the initial slip of magnetization and the global persistence exponent θg associated with the probability P(t) that magnetization keeps its signal up to time t. Our estimates for the dynamic critical exponents at the Lifshitz point are z = 2.34(2) and θg = 0.336(4), values that are very different from those of the three-dimensional Ising model (the ANNNI model without the next-nearest-neighbor interactions at the z axis, i.e., J2 = 0), i.e., z ≈ 2.07 and θg ≈ 0.38. We also present estimates for the static critical exponents β and ν, obtained from extended time-dependent scaling relations. Our results for static exponents are in good agreement with previous works.

A presença de Salmonella é uma das mais importantes barreiras sanitárias à exportação de alimentos. A ração contaminada representa potencial fonte de introdução de Salmonella nos rebanhos suínos, além do risco indireto de infecção ao consumidor. Um estudo transversal conduzido em quatro fábricas de ração teve como objetivos avaliar a frequência de isolamento de Salmonella e coliformes totais nestas unidades, verificar a presença desses agentes nas diversas etapas do processo de produção, correlacionar grupos clonais de Salmonella sp. obtidos pela análise de macrorestrição associada à eletroforese em campo pulsado (PFGE), além de avaliar a concordância entre o escore obtido na aplicação de roteiro de inspeção da Instrução Normativa (IN) 4 do Ministério da Agricultura e Abastecimento e os níveis de coliformes totais encontrados. De 1.269 amostras analisadas, sessenta e três (4,96%) apresentaram Salmonella sp. e 38,53% (n=489) apresentaram presença de enterobactérias. As freqüências de contaminação por Salmonella nas quatro fábricas avaliadas (A, B, C e D) foram, respectivamente, 3,5% (n=11/317), 1,7% (n=5/289), 7,1% (n=23/308) e 7% (n=25/355). Já para coliformes totais foram, respectivamente, 40,7% (129/317), 30,1% (87/289), 52,6% (162/308) e 31,3% (111/355). Nas fábricas A e D, Salmonella foi detectada em amostras de produto final. Estirpes apresentando genótipos semelhantes foram identificadas nos sorovares Orion, Montevideo, Worthington e Agona. Foi possível verificar que o sorovar Montevideo obteve o maior número de grupos clonais, apresentando pulsotipos distribuídos entre ingredientes, poeira, equipamentos e ração. O isolamento de Salmonella foi significativamente mais frequente (p =0,002) em amostras com a presença (36/489; 7,36%) do que com ausência de coliformes totais (27/780; 3,46%). As contagens logarítmicas médias encontradas de coliformes totais, considerando todas as amostras analisadas por fábrica, foram: A: 0,97 (IC 95%: 0,81-1,13); B: 0,78 (IC 95%: 0,61-0,94); C: 1,32 (IC 95%: 1,16-1,49) e D: 0,91 (IC 95%: 0,75-1,06). Constatou-se elevada variabilidade no número de coliformes totais em todos os pontos amostrados nas quatro fábricas, e não houve diferenças significativas entre os pontos amostrados e entre as fábricas (p=0,174). A regressão logística tendo como variável resposta a presença de coliformes totais apontou maiores razão de chance (OR) de isolamento no transportador (OR=3,67; IC 95%: 2,28-5,89), dosagem (OR=9,51, IC 95%: 4,43-20,41), moagem (OR=7,1; IC 95%: 3,27-15,40), mistura (OR=4,08; IC 95%: 2,04-8,17), poeira (OR=3,50; IC 95%:2,10-5,84), resíduos (OR=6,22; IC 95%: 3,88-9,95) e fábrica C (OR=2,43; IC 95%: 1,68-3,53). Da mesma forma, o transportador (OR= 4,43; IC95%: 2,43-8,09) foi o local com maior probabilidade de isolamento de Salmonella, seguidos da poeira coletada nas dependências da fábrica (OR=2,88; IC95%: 1,41-5,88). Comparadas à fábrica B, as unidades C e D apresentaram, respectivamente, 2,74 e 2,83 mais chances de isolamento de Salmonella. Ao analisar os 128 itens necessários no Roteiro de Inspeção da IN4, a fábrica B obteve o menor número de não conformidades. Nas demais fábricas, as maiores inconformidades foram encontradas quanto à estrutura da área interna e externa das fábricas. As fábricas A e D foram as que apresentaram o maior número de itens não conformes relacionados à limpeza e higienização de equipamentos. Entre os 29 itens imprescindíveis na Avaliação de Estabelecimento e Procedimentos Operacionais Padrão, oito não foram cumpridos em pelo menos uma das fábricas. A fábrica B apresentou todos os itens em conformidade, ao passo que as fábricas A e D não cumpriram os oito itens. A fábrica C apresentou três itens não conformes, relacionados à limpeza de piso e parede, recepção e armazenamento de matérias-primas. Não houve concordância entre os escores obtidos no roteiro de avaliação e a média de coliformes totais encontrada nas fábricas, demonstrando que apenas a adequação à legislação pode não garantir a inocuidade do alimento produzido. A partir disso, conclui-se que é necessário implantar programas de monitoramento e controle microbiológico ao longo da linha de produção, independente da situação da fábrica em relação à legislação vigente. A elaboração e produção de equipamentos de fácil limpeza e com mínimo acúmulo de poeira e resíduos deve ser incluída nos programas de controle de Salmonella concomitante às demais medidas de controle preconizadas. The presence of Salmonella is one of the most important sanitary barriers to food exports. The contaminated feed is a potential source of introduction of Salmonella in pig herds, and may also represent a risk to the consumer. A cross-sectional study conducted in four feed mills was carried out to evaluate the frequency of isolation of enterobacteria and Salmonella at various stages of feed production, to identify clonal groups of Salmonella sp. Obtained by macrorestriction analysis associated with pulsed field gel electrophoresis (PFGE), and to verify the association between the score obtained by feed mills after the application of the checklist of the Normative 4 (IN4) of the Ministry of Agriculture and Food Supply and the mean of total coliforms found in the unit. Among 1,269 samples analysed, sixty-three (4.96%) showed the presence of Salmonella. The four feeds mills evaluated (A, B, C and D) presented, respectively, 3,5% (n=11/317), 1.7% (n=5/289), 7,1% (n=23/308), and 7% (n=25/355) of positive samples. Total coliforms were isolated from 40.7% (129/317), 30.1% (87/289), 52.6% (162/308) e 31.3% (111/355) samples taken at unit A, B, C and D, respectively. In the units A and D, Salmonella was detected in samples of feed. Strains showing similar genotypes have been identified as Serovar Orion, Montevideo, Worthington and Agona. Serovar Montevideo presented the highest number of clonal groups, with common pulsotypes distributed among ingredients, dust, equipment and feed. The isolation of Salmonella was significantly higher (p=0,002) in samples with the presence of total coliforms (36/489; 7.36%) than in the negative ones (27/780; 3.46%). The mean logarithmic counts of total coliforms considering all samples were determined for each plant: A: 0.97 (95% CI: 0.81 to 1.13), B: 0.78 (95% CI: 0.61 to 0.94), C: 1.32 (95% CI: 1.16 to 1.49) and D: 0.91 (95% CI: 0.75 to 1.06). A high variability on the number of total coliforms in all the sampled points was found in all feed mills, and there was no statistical diference between the sampling sites and units (p=0.174). The logistic regression, with isolation of total coliforms as the response variable, showed a high odds ratio (OR) of isolation from conveyors (OR = 3.67, 95% CI: 2.28 to 5.89), dosing (OR = 9.51, 95% CI: 4.43 to 20.41), grinding (OR = 7.10, 95% CI = 3.27 to 15.40), mixing (OR = 4.08, 95 % CI: 2.04 to 8.17), dust (OR = 3.50, 95% CI: 2.10 to 5.84), crusts (OR = 6.22, 95% CI: 3.88 to 9.95) and unit C (OR = 2.43, 95% CI: 1.68 to 3.53). The conveyors (OR = 4.43, 95% CI: 2.43-8.09) were the most likely sites of isolation of Salmonella, followed by the dust collected on the premises of the plant (OR = 2.88, 95% CI: 1.41-5.88). Feed mills C and D showed, respectively, 2.74 and 2.83 higher odds for Salmonella isolation than feed mill B. The verification of the 128 items addressed on the Guidelines for Inspection of Normative 4 (IN 4) of the Brazilian Ministry of Agriculture and Food Supply pointed out that factory B had the lowest number of nonconformities. The other three feed mills, presented most faults related to the physical structure of the facilities. Feed mills A and D presented the largest number of nonconformities related to cleaning and sanitizing of equipment. Among the 29 mandatory items in IN4, eight were not met in at least one of the factories. Feed mill B presented all items accordingly, while plants A and D did not meet any of the eight items. Feed mill C had three non-compliant items related to the floor and wall cleaning, reception and storage of raw materials. There was no association between the score obtained on the inspection checklist and the level of total coliforms found in the sampled units, demonstrating that only the compliance to the legislation cannot guarantee the safety of feed produced. It was concluded that programs for monitoring and control microbial contamination throughout the production line are needed, regardless of the status of the plant in the relation to the current legislation.The design of equipment that allow easy cleaning and with minimal accumulation of dust and debris should be added to other measures in Salmonella control programs.

We provide extended evidence that mode-coupling theory (MCT) of supercooled liquids for the F12 schematic model admits a microscopic realization based on facilitated spin models with tunable facilitation. Depending on the facilitation strength, one observes two distinct dynamical glass transition lines—continuous and discontinuous—merging at a dynamical tricritical-like point with critical decay exponents consistently related by MCT predictions. The mechanisms of dynamical arrest can be naturally interpreted in geometrical terms: the discontinuous and continuous transitions correspond to bootstrap and standard percolation processes, in which the incipient spanning cluster of frozen spins forms either a compact or a fractal structure, respectively. Our cooperative dynamical facilitation picture of glassy behavior is complementary to the one based on disordered systems and can account for higher-order singularity scenarios in the absence of a finite temperature thermodynamic glass transition. We briefly comment on the relevance of our results to finite spatial dimensions and to the F13 schematic model.

Using the thermodynamic Bethe ansatz equations we study the quantum phase diagram, thermodynamics, and criticality of one-dimensional (1D) spin-1 bosons with strongly repulsive density-density and antiferromagnetic spin-exchange interactions. We analytically derive a high-precision equation of state from which the Tomonaga- Luttinger-liquid physics and quantum critical behavior of the system are computed. We obtain explicit forms for the scaling functions near the critical points yielding the dynamical exponent z = 2 and correlation length exponent ν = 1/2 for the quantum phase transitions driven by either the chemical potential or the magnetic field. Consequently, we further demonstrate that quantum criticality of the system can be mapped out from the finite temperature density and magnetization profiles of the 1D trapped gas. Our results provide the physical origin of quantum criticality in a 1D many-body system beyond the Tomonaga-Luttinger-liquid description.

We address the investigation of the solvation properties of the minimal orientational model for water originally proposed by [Bell and Lavis, J. Phys. A 3, 568 (1970)]. The model presents two liquid phases separated by a critical line. The difference between the two phases is the presence of structure in the liquid of lower density, described through the orientational order of particles. We have considered the effect of a small concentration of inert solute on the solvent thermodynamic phases. Solute stabilizes the structure of solvent by the organization of solvent particles around solute particles at low temperatures. Thus, even at very high densities, the solution presents clusters of structured water particles surrounding solute inert particles, in a region in which pure solvent would be free of structure. Solute intercalates with solvent, a feature which has been suggested by experimental and atomistic simulation data. Examination of solute solubility has yielded a minimum in that property, which may be associated with theminimum found for noble gases.We have obtained a line of minimum solubility (TmS) across the phase diagram, accompanying the line of maximum density. This coincidence is easily explained for noninteracting solute and it is in agreement with earlier results in the literature.We give a simple argument which suggests that interacting solute would dislocate TmS to higher temperatures.

Molecular dynamics simulations are used to examine the relationship between water-like anomalies and the liquid-liquid critical point in a family of model fluids with multi-Gaussian, core-softened pair interactions. The core-softened pair interactions have two length scales, such that the longer length scale associated with a shallow, attractive well is kept constant while the shorter length scale associated with the repulsive shoulder is varied from an inflection point to a minimum of progressively increasing depth. The maximum depth of the shoulder well is chosen so that the resulting potential reproduces the oxygen-oxygen radial distribution function of the ST4 model of water. As the shoulder well depth increases, the pressure required to form the high density liquid decreases and the temperature up to which the high-density liquid is stable increases, resulting in the shift of the liquid-liquid critical point to much lower pressures and higher temperatures. To understand the entropic effects associated with the changes in the interaction potential, the pair correlation entropy is computed to show that the excess entropy anomaly diminishes when the shoulder well depth increases. Excess entropy scaling of diffusivity in this class of fluids is demonstrated, showing that decreasing strength of the excess entropy anomaly with increasing shoulder depth results in the progressive loss of water-like thermodynamic, structural and transport anomalies. Instantaneous normal mode analysis was used to index the overall curvature distribution of the fluid and the fraction of imaginary frequency modes was shown to correlate well with the anomalous behavior of the diffusivity and the pair correlation entropy. The results suggest in the case of core-softened potentials, in addition to the presence of two length scales, energetic, and entropic effects associated with local minima and curvatures of the pair interaction play an important role in determining the presence of water-like anomalies and the liquid-liquid phase transition.

Tese de mestrado em Estatística, apresentada à Universidade de Lisboa, através da Faculdade de Ciências, 2011 Submitted by Teresa Boa (tdboa@fc.ul.pt) on 2013-09-13T13:30:22Z No. of bitstreams: 1 ulfc104671_tm_Paulo_dos_Santos.pdf: 1703988 bytes, checksum: c9e73f3099770a581fc4c5994a2fadf2 (MD5) Made available in DSpace on 2013-09-13T13:30:31Z (GMT). No. of bitstreams: 1 ulfc104671_tm_Paulo_dos_Santos.pdf: 1703988 bytes, checksum: c9e73f3099770a581fc4c5994a2fadf2 (MD5) Previous issue date: 2011

We investigate the nature of the superfluid-insulator quantum phase transition driven by disorder for non-interacting ultracold atoms on one-dimensional lattices. We consider two different cases: Anderson-type disorder, with local energies randomly distributed, and pseudo-disorder due to a potential incommensurate with the lattice, which is usually called the Aubry-Andr\'e model. A scaling analysis of numerical data for the superfluid fraction for different lattice sizes allows us to determine quantum critical exponents characterizing the disorder-driven superfluid-insulator transition. We also briefly discuss the effect of interactions close to the non-interacting quantum critical point of the Aubry-Andr\'e model., Comment: 5 pages, 4 figures

We report on the lattice evolution of BiFeO3 as function of temperature using far infrared emissivity, reflectivity, and X-ray absorption local structure. A power law fit to the lowest frequency soft phonon in the magnetic ordered phase yields an exponent {\beta}=0.25 as for a tricritical point. At about 200 K below TN~640 K it ceases softening as consequence of BiFeO3 metastability. We identified this temperature as corresponding to a crossover transition to an order-disorder regime. Above ~700 K strong band overlapping, merging, and smearing of modes are consequence of thermal fluctuations and chemical disorder. Vibrational modes show band splits in the ferroelectric phase as emerging from triple degenerated species as from a paraelectric cubic phase above TC~1090 K. Temperature dependent X-ray absorption near edge structure (XANES) at the Fe K-edge shows that lower temperature Fe3+ turns into Fe2+. While this matches the FeO w\"ustite XANES profile, the Bi LIII-edge downshift suggests a high temperature very complex bond configuration at the distorted A perovskite site. Overall, our local structural measurements reveal high temperature defect-induced irreversible lattice changes, below, and above the ferroelectric transition, in an environment lacking of long-range coherence. We did not find an insulator to metal transition prior to melting., Comment: Accepted for publication

O investimento efectuado na últimas décadas, em Portugal, nas infra-estruturas de transporte de longa duração, permitiu o desenvolvimento da rede rodoviária, quer em extensão quer em qualidade, enquanto pelo contrário, a Rede Ferroviária Nacional (RFN), entrou num processo contínuo de degradação, percebido pela redução das velocidades máximas permitidas e pelo elevado número e dispersão de limitações (reduções) de velocidades impostas na via-férrea. Actualmente, um comboio ao circular na RFN, fica sujeito a variadíssimas reduções de velocidade, recorrendo obrigatoriamente à utilização do freio, com impacto na eficiência energética e na redução das velocidades comerciais. Estes factores, associados às baixas performances do material, nomeadamente o reduzido esforço acelerador, em particular no diesel, resulta no aumento dos tempos de percurso e na redução do conforto, factores que constituem sem dúvida, as principais causas de perda de competitividade do sector ferroviário, tendo culminado na perda de 30% dos passageiros transportados, para o modo rodoviário, nas últimas décadas. Constituiu o objectivo deste trabalho, criar um modelo dinâmico, que permita identificar os pontos críticos da RFN, medindo o impacto das reduções de velocidade nas circulações ferroviárias, em tempo perdido, em termos energéticos, ambientais e financeiros. Os indicadores obtidos através da aplicação do modelo, são produzidos com auxílio do computador, identificando os pontos críticos da infra-estrutura e ordenando-os em função do impacto financeiro na oferta comercial da CP regional. Este relatório, será efectuado com uma periodicidade concertada com a REFER e permitirá ao gestor da infra-estrutura, programar de forma objectiva as intervenções na RFN, eliminando os pontos críticos. Contibui-se assim, para a melhoria da qualidade do serviço, para o aumento da competitividade e da sustentabilidade do sector ferroviário em Portugal.

We study the domain geometry during spinodal decomposition of a 50:50 binary mixture in two dimensions. Extending arguments developed to treat non-conserved coarsening, we obtain approximate analytic results for the distribution of domain areas and perimeters during the dynamics. The main approximation is to regard the interfaces separating domains as moving independently. While this is true in the non-conserved case, it is not in the conserved one. Our results can therefore be considered as a first-order approximation for the distributions. In contrast to the celebrated Lifshitz-Slyozov-Wagner distribution of structures of the minority phase in the limit of very small concentration, the distribution of domain areas in the 50:50 case does not have a cut-off. Large structures (areas or perimeters) retain the morphology of a percolative or critical initial condition, for quenches from high temperatures or the critical point respectively. The corresponding distributions are described by a $c A^{-\tau}$ tail, where $c$ and $\tau$ are exactly known. With increasing time, small structures tend to have a spherical shape with a smooth surface before evaporating by diffusion. In this regime the number density of domains with area $A$ scales as $A^{1/2}$, as in the Lifshitz-Slyozov-Wagner theory. The threshold between the small and large regimes is determined by the characteristic area, ${\rm A} \sim [\lambda(T) t]^{2/3}$. Finally, we study the relation between perimeters and areas and the distribution of boundary lengths, finding results that are consistent with the ones summarized above. We test our predictions with Monte Carlo simulations of the 2d Ising Model., Comment: 10 pages, 8 figures

Using Monte Carlo simulations we investigate some new aspects of the phase diagram and the behavior of the diffusion coefficient in an associating lattice gas (ALG) model on different regions of the phase diagram. The ALG model combines a two dimensional lattice gas where particles interact through a soft core potential and orientational degrees of freedom. The competition between soft core potential and directional attractive forces results in a high density liquid phase, a low density liquid phase, and a gas phase. Besides anomalies in the behavior of the density with the temperature at constant pressure and of the diffusion coefficient with density at constant temperature are also found. The two liquid phases are separated by a coexistence line that ends in a bicritical point. The low density liquid phase is separated from the gas phase by a coexistence line that ends in tricritical point. The bicritical and tricritical points are linked by a critical λ-line. The high density liquid phase and the fluid phases are separated by a second critical τ-line. We then investigate how the diffusion coefficient behaves on different regions of the chemical potential-temperature phase diagram. We find that diffusivity undergoes two types of dynamic transitions: a fragile-to-strong transition when the critical λ-line is crossed by decreasing the temperature at a constant chemical potential; and a strong-to-strong transition when the critical τ-line is crossed by decreasing the temperature at a constant chemical potential.

Submitted by Emanuel Varela Cardoso (emanuel.varela@ufcg.edu.br) on 2019-01-08T10:45:43Z No. of bitstreams: 1 LEOPOLDO MAURÍCIO TAVARES BARBOSA – DISSERTAÇÃO (PPGMat) 2007.pdf: 904912 bytes, checksum: b6471dc193ebfb7b898e0fabb3e7f1fa (MD5) Made available in DSpace on 2019-01-08T10:45:43Z (GMT). No. of bitstreams: 1 LEOPOLDO MAURÍCIO TAVARES BARBOSA – DISSERTAÇÃO (PPGMat) 2007.pdf: 904912 bytes, checksum: b6471dc193ebfb7b898e0fabb3e7f1fa (MD5) Previous issue date: 2007-10 Capes Neste trabalho usamos métodos variacionais para mostrar a existência de solução fraca para dois tipos de problema. O primeiro trata-se de uma Equação Diferencial Ordinária do tipo u 00 (t) + G 0 (u(t)) = f(t). O segundo é referente ao sistema Hamiltoniano u 0 (t) = JrH(t, u(t)). In this work we use variational methods to show the existence of weak solutions for two types problems. The first, is related with a following Ordinary Differential Equations of the form u 00 (t) + G 0 (u(t)) = f(t). The second is relating at the Hamiltonian Systems u 0 (t) = JrH(t, u(t)).

We show results from Monte Carlo simulations of a two dimensional Heisenberg model for ultrathin films with perpendicular anisotropy. A complete phase diagram is obtained as a function of anisotropy and temperature, spanning a wide range of behavior. We discuss our results in relation with experimental findings in different ultrathin films. We observe and characterize a line of Spin Reorientation Transitions . This transition from out of plane stripe order to in plane ferromagnetic order presents a paramagnetic gap in between in a finite region in parameter space, as reported in experiments. For large anisotropies direct transitions from a low temperature stripe phase to a paramagnetic or tetragonal phase with dominant perpendicular magnetization is observed, also in agreement with experiments. We also show the phase diagram for a system without exchange, i.e. with pure dipolar and anisotropy interactions. It shows a similar behavior to the ferromagnetic case with antiferromagnetic instead of stripe phases at low temperatures. A Spin Reorientation Transition is also found in this case., Comment: 9 pages, 13 figures

The authors investigate the phase diagram of a three-dimensional associating lattice gas (ALG) model. This model combines orientational icelike interactions and “van der Waals” that might be repulsive, representing, in this case, a penalty for distortion of hydrogen bonds. These interactions can be interpreted as two competing distances, making the connection between this model and continuous isotropic soft-core potentials. The authors present Monte Carlo studies of the ALG model showing the presence of two liquid phases, two critical points, and density anomaly.

Made available in DSpace on 2017-07-10T19:25:14Z (GMT). No. of bitstreams: 1 Moacir Kessler.pdf: 322336 bytes, checksum: 4b48bc8db4ae1af200ec7e3f622ff383 (MD5) Previous issue date: 2006-07-27 This work had as objective to identify the critical points of insect control in structures of grain storage. The study was realized in the period of reception of the soy and maize harvest of 2006 in seven typical storing units of Western Paran? State. The presented data had been object of inspecting in the respective storing units during the reception of the harvest and aimed to identify the points inspected in the units; the presence of adult insects, the accumulation of residues, the difficulty of access to the place for cleanness, the lack of planning of the structure for the cleanness of the place and the lack of planning or of the project of the equipment aiming at its cleanness. The study proves that the inappropriateness of the installations and of the equipment is the cause of focus of infestation for insects, compromising the quality of the stored product beyond generating incidental costs to the storekeeper. The work objectified not only to present the critical points of insect control plague in the storage structures; as mainly to consider techniques of cleanness of the installations, of the equipment, to consider adjustments in the equipment and the installations being aimed at improvement in the cleanness and reduction or elimination of the deposited residues and consequent elimination of the focus of infestation, still considers changes in the projects of new storing units and equipment so that the same ones have a new concept in the conception of the projects and construction aiming the non deposition of residues, critical points of development of insects. Este trabalho teve o objetivo de identificar os pontos críticos no controle de insetos em equipamentos e estruturas de armazenagem de grãos. O estudo foi realizado durante a recepção das safras de soja e milho de 2006, em sete unidades armazenadoras típicas da região oeste do Estado do Paraná. Os dados apresentados foram objeto de vistorias nas unidades armazenadoras no decorrer da recepção da safra e visou identificar nos pontos vistoriados nas unidades a presença de insetos adultos; o acúmulo de resíduos; a dificuldade de acesso ao local para limpeza; a falta de planejamento da estrutura para a limpeza do local e a falha de planejamento ou de projeto dos equipamentos ou da estrutura visando a sua limpeza. O estudo comprovou que a inadequação tanto das instalações como dos equipamentos é causa de foco de infestação por insetos, comprometendo a qualidade do produto armazenado além de gerar custos adicionais ao armazenador. O trabalho objetivou também sugerir a adoção de técnicas de limpeza das instalações, dos equipamentos, propor ajustes nos equipamentos e nas instalações, visando melhoria na limpeza e a eliminação dos resíduos depositados e conseqüente redução dos focos de infestação; propõe ainda alteração nos projetos de novas unidades armazenadoras e equipamentos a fim de que os mesmos tenham um novo conceito na concepção dos projetos e construção, visando a não deposição de resíduos, pontos críticos de desenvolvimento de insetos. Nos resultados das inspeções realizadas nas instalações das unidades armazenadoras foram constatados diversos pontos críticos de controle de pragas em suas instalações e equipamentos. Ficou demonstrando também que as condições das unidades armazenadoras pesquisadas e atualmente destinadas ao beneficiamento de cereais, carecem de uma série de providências para não permitir a deposição de resíduos e a conseqüente proliferação de insetos; sendo que as novas instalações dever ter seus projetos melhor elaborados a fim de que não se permita pontos críticos de deposição de resíduos para o desenvolvimento de pragas.

We analyze the infinite range Ising spin glass in a transverse-field below the critical temperature by a one step replica symmetry breaking theory. The set of n replicas is divided in r blocks of m replicas each. We present results for different values of the block-size parameter m. The spin operators are represented by bilinear combinations of fermionic fields and we compare the results of two models: In the four-states 4-S model the diagonal Si z operator has two unphysical vanishing eigenvalues, that are suppressed by a restraint in the two-states 2-S model. In the static approximation we obtain qualitatively similar results for both models. They both exhibit a critical temperature Tc that decreases when increases, until it reaches a quantum critical point at the same value of c and they are both unstable under replica symmetry breaking in the whole spin glass phase. Below the critical temperature we present results for the order parameters and free energy.

We employ a topological approach to investigate the nature of quasistationary states of the mean-field XY Hamiltonian model. We focus on the quasistationary states reached when the system is initially prepared in a fully magnetized configuration. By means of numerical simulations and analytical considerations, we show that, along the quasistationary trajectories, the system evolves in a manifold of critical points of the potential energy function. Although these critical points are maxima, the large number of directions with marginal stability may be responsible for the slow relaxation dynamics and the trapping of the system in such trajectories.

We introduce a renormalized Jellium model to calculate the equation of state for charged colloidal suspensions. An almost perfect agreement with Monte Carlo simulations is found. Our self-consistent approach naturally allows to define the effective charge of particles {\em at finite colloidal density}. Although this quantity may differ significantly from its counterpart obtained from the standard Poisson-Boltzmann cell approach, the osmotic pressures for both models are in good agreement. We argue that by construction, the effective charge obtained using the Jellium approximation is more appropriate to the study of colloidal interactions. We also discuss a possibility of a fluid-fluid critical point and show how the new equation of state can be used to shed light on the surprising results found in recent sedimentation experiments., Comment: 4 pages, 3 figures

The Kondo–spin glass competition is studied in a theoretical model of a Kondo lattice with an intrasite Kondo-type exchange interaction treated within the mean-field approximation, an intersite quantum Ising exchange interaction with random couplings among localized spins, and an additional transverse field Γ in the x direction, which represents a simple quantum mechanism of spin flipping, in order to have a better description of the spin glass state and in particular of the quantum critical point (QCP). Taking here a parametrization Γ=αJ²K (where JK is the antiferromagnetic Kondo coupling), we obtain two second order transition lines from the spin glass state to the paramagnetic one and then to the Kondo state. For a reasonable set of the different parameters, the two second order transition lines do not intersect and end in two distinct QCPs. The existence of a QCP in the spin glass–Kondo competition allows one to give a better description of the phase diagrams of some cerium and uranium disordered alloys.