With its long cycle life and scalable design, the vanadium redox flow battery (VRB) is a promising technology for grid energy storage. However, high materials costs have impeded its commercialization. An essential but costly component of the VRB is the ion-exchange membrane. The ideal VRB membrane provides a highly conductive path for protons, prevents crossover of reactive species, and is tolerant of the acidic and oxidizing chemical environment of the cell. In order to study membrane performance and optimize cell design, mathematical models of the separator membrane have been developed. Where previous VRB membrane models considered minimal details of membrane transport, generally focusing on conductivity or self-discharge at zero current, the model presented here considers coupled interactions between each of the major species by way of rigorous material balances and concentrated solution theory. The model describes uptake and transport of sulfuric acid, water, and vanadium ions in Nafion membranes, focusing on operation at high current density. Governing equations for membrane transport are solved in finite difference form using the Newton-Raphson method. Model capabilities were explored, leading to predictions of Ohmic losses, vanadium crossover, and electro-osmotic drag. Experimental methods were presented for validating the model and for further improving estimates of uptake parameters and transport coefficients. / text

Eye movements are a powerful tool to examine cognitive processes. However, in most paradigms little is known about the dynamics present in sequences of saccades and fixations. In particular, the control of fixation durations has been widely neglected in most tasks. As a notable exception, both spatial and temporal aspects of eye-movement control have been thoroughly investigated during reading. There, the scientific discourse was dominated by three controversies, (i), the role of oculomotor vs. cognitive processing on eye-movement control, (ii) the serial vs. parallel processing of words, and, (iii), the control of fixation durations. The main purpose of this thesis was to investigate eye movements in tasks that require sequences of fixations and saccades. While reading phenomena served as a starting point, we examined eye guidance in non-reading tasks with the aim to identify general principles of eye-movement control. In addition, the investigation of eye movements in non-reading tasks helped refine our knowledge about eye-movement control during reading. Our approach included the investigation of eye movements in non-reading experiments as well as the evaluation and development of computational models. I present three main results : First, oculomotor phenomena during reading can also be observed in non-reading tasks (Chapter 2 & 4). Oculomotor processes determine the fixation position within an object. The fixation position, in turn, modulates both the next saccade target and the current fixation duration. Second, predicitions of eye-movement models based on sequential attention shifts were falsified (Chapter 3). In fact, our results suggest that distributed processing of multiple objects forms the basis of eye-movement control. Third, fixation durations are under asymmetric control (Chapter 4). While increasing processing demands immediately prolong fixation durations, decreasing processing demands reduce fixation durations only with a temporal delay. We propose a computational model ICAT to account for asymmetric control. In this model, an autonomous timer initiates saccades after random time intervals independent of ongoing processing. However, processing demands that are higher than expected inhibit the execution of the next saccade and, thereby, prolong the current fixation. On the other hand, lower processing demands will not affect the duration before the next saccade is executed. Since the autonomous timer adjusts to expected processing demands from fixation to fixation, a decrease in processing demands may lead to a temporally delayed reduction of fixation durations. In an extended version of ICAT, we evaluated its performance while simulating both temporal and spatial aspects of eye-movement control. The eye-movement phenomena investigated in this thesis have now been observed in a number of different tasks, which suggests that they represent general principles of eye guidance. I propose that distributed processing of the visual input forms the basis of eye-movement control, while fixation durations are controlled by the principles outlined in ICAT. In addition, oculomotor control contributes considerably to the variability observed in eye movements. Interpretations for the relation between eye movements and cognition strongly benefit from a precise understanding of this interplay. / Blickbewegungen stellen ein wichtiges Instrument dar, um kognitive Prozesse zu untersuchen. In den meisten Paradigmen ist allerdings wenig über die Entstehung von Sakkaden und Fixationen bekannt. Insbesondere die Kontrolle der Fixationsdauern wurde häufig außer acht gelassen. Eine wesentliche Ausnahme stellt die Leseforschung dar, in der sowohl zeitlichliche als auch räumliche Aspekte der Blickbewegungssteuerung im Detail betrachtet wurden. Dabei war der wissenschaftliche Diskurs durch drei Kontroversen gekennzeichnet, die untersuchten, (i), welchen Einfluss okulomotorische bzw. kognitive Prozesse auf die Blicksteuerung haben, (ii), ob Worte seriell oder parallel verarbeitet werden und, (iii), wie Fixationsdauern kontrolliert werden. Die vorliegende Arbeit zielt im wesentlichen darauf ab, die Dynamik von Fixationssequenzen zu erforschen. Ausgehend von den Erkenntnissen beim Lesen untersuchten wir Blickbewegungen in Nichtlese-Aufgaben, mit dem Ziel allgemeine Prinzipien der Blicksteuerung zu identifizieren. Zusätzlich versuchten wir mit Hilfe dieser Aufgaben, Erkenntnisse über Prozesse beim Lesen zu vertiefen. Unser Vorgehen war sowohl von der Durchführung von Experimenten als auch der Entwicklung und Evaluation computationaler Modelle geprägt. Die Hauptbefunde zeigten: Erstens, okulomotorische Phänomene des Lesens lassen sich in Suchaufgaben ohne Wortmaterial replizieren (Kapitel 2 & 4). Dabei bestimmen okulomotorische Prozesse die Fixationsposition innerhalb eines Objektes. Diese wiederum beeinflusst das nächste Sakkadenziel sowie die Fixationsdauer. Zweitens, wesentliche Vorhersagen von Modellen, in denen Blickbewegungen von seriellen Aufmerksamkeitsverschiebungen abhängen, konnten falsifiziert werden (Kapitel 3). Stattdessen legen unsere Erkenntnisse nahe, dass die Blicksteuerung von der parallelen Verarbeitung mehrerer Objekte abhängt. Drittens, Fixationsdauern werden asymmetrisch kontrolliert (Kapitel 4). Während hohe Verarbeitungsanforderungen Fixationsdauern unmittelbar verlängern können, führen niedrige Verarbeitungsanforderungen nur zeitlich verzögert zu einer Reduktion. Wir schlagen ein computationales Modell ICAT vor, um asymmetrische Kontrolle zu erklären. Grundlage des Modells ist ein autonomer Zeitgeber, der unabhängig von der momentanen Verarbeitung nach zufälligen Zeitintervallen Sakkaden initiiert. Unerwartet hohe Verarbeitungsanforderungen können die Initiierung der nächsten Sakkade hinauszögern, während unerwartet niedrige Verarbeitungsanforderungen den Beginn der nächsten Sakkade nicht verändern. Der Zeitgeber passt sich allerdings von Fixation zu Fixation neuen Verarbeitungsanforderungen an, so dass es zu einer zeitlich verzögerten Reduktion der Fixationsdauern kommen kann. In einer erweiterten Version des Modells überprüfen wir die Kompatibilität ICATs mit einer realistischen räumlichen Blicksteuerung. Die Ähnlichkeit von Blickbewegungsphänomenen über Aufgaben hinweg legt nahe, dass sie auf allgemeinen Prinzipien basieren. Grundlage der Blicksteuerung ist die verteilte Verarbeitung des visuellen Inputs, während die Kontrolle der Fixationsdauer auf den Prinzipien von ICAT beruht. Darüber hinaus tragen okulomotorische Phänomene wesentlich zur Variabilität der Blicksteuerung bei. Ein Verständnis dieses Zusammenspiels hilft entscheidend den Zusammenhang von Blickbewegungen und Kognitionen besser zu verstehen.

Uma potencial alternativa para o transplante de tecidos é a engenharia de tecidos. Células-tronco mesenquimais e scaffolds eletrofiados são comumente utilizados nesta área devido à capacidade multipotente de diferenciação destas células e à rede de poros interconectados destas estruturas fibrosas. Além disso, bioreatores de perfusão podem ser utilizados para melhorar o transporte de nutrientes e reduzir o acúmulo de metabolitos tóxicos. Neste contexto, uma maneira de estudar e otimizar o sistema de cultivo é utilizar técnicas de modelagem para descrever interações ou processos individuais envolvidos no crescimento celular. Deste modo, o objetivo geral deste estudo é realizar o cultivo de células-tronco mesenquimais da polpa de dente decíduo (DPSCs) utilizando scaffolds tridimensionais eletrofiados de policaprolactona (PCL), biorreatores e técnicas de modelagem. Inicialmente foram testadas diferentes misturas de solventes (clorofórmio e metanol), a fim de produzir scaffolds com poros adequados ao cultivo tridimensional. Os diâmetros de fibra e de poro foram determinados por microscopia eletrônica de varredura (MEV). O crescimento e o metabolismo das células foram avaliados através da determinação da atividade metabólica e das concentrações de glicose e lactato do meio de cultivo, e a infiltração celular foi observada com a marcação do núcleo celular. Depois de estabelecidos os parâmetros de eletrofiação, o efeito da perfusão direta no desprendimento de DPSCs de scaffolds eletrofiados de PCL foi estudado. A atividade metabólica das células foi determinada para diferentes tempos de adesão, vazões e densidades de semeadura, e a tensão de cisalhamento na parede do poro foi calculada para cada vazão. A morfologia das células foi avaliada através de imagens de microscopia confocal e MEV. Paralelamente, foram realizadas simulações utilizando o software OpenFOAM para estudar como os parâmetros e variáveis de entrada (concentração inicial de glicose, porosidade e espessura do scaffold) afetam as saídas (fração volumétrica de células e concentração de substrato) de um modelo de proliferação celular que considera a difusão e o consumo de glicose. As contribuições do teor de oxigêno na cinética de crescimento de Contois e da variação da porosidade com o tempo devido à degradação do polímero também foram avaliadas. Inicialmente, foi observado que apenas um tamanho de poro maior que o diâmetro da célula permitiu a infiltração das células no scaffold. Então, observou-se que o aumento do tempo de adesão acarretou em maior espalhamento das células e, assim como a diminuição da densidade de semeadura e da tensão de cisalhamento, resultou em uma redução do desprendimento das células sob perfusão. Quanto ao modelo fenomenológico, observou-se maior sensibilidade à concentração inicial de glicose e à porosidade do scaffold, e aos parâmetros adimensionais relacionados à proliferação e morte celular e ao consumo de nutrientes. Além disso, o número inicial de células apresentou maior impacto no transporte de massa do que no crescimento celular. Neste estudo, foi possível obter scaffolds eletrofiados e conduções de cultivo dinâmico adequadas ao cultivo tridimensional de DPSCs, e elucidar os efeitos da limitação do transporte de massa e do oxigênio no crescimento celular, e da degradação do polímero no transporte de massa. / A potential alternative to tissue transplant is tissue engineering. Mesenchymal stem cells and electrospun scaffolds are commonly used in this field due to the multipotent differentiation capacity of these cells and the interconnected pore network of these fibrous structures. In addition, perfusion bioreactors can be used to enhance nutrient transport and reduce the accumulation of toxic metabolites. In this context, one way to study and optimize the culture system is to use modeling techniques to describe interactions or individual processes involved in cell growth. Thus, the objective of this study is to perform the three-dimensional culture of mesenchymal stem cells of dental pulp (DPSCs) using electrospun polycaprolactone (PCL) scaffolds, bioreactors and modeling techniques. Initially, different solvent mixtures (chloroform and methanol) were tested to produce scaffolds with pores suitable to three-dimensional culture. Fiber and pore diameter was determined using a scanning electron microscope. Cell growth and metabolism were evaluated through the metabolic activity and the culture medium concentration of glucose and lactate, and the cell infiltration was observed with cell nuclei staining. After the establishment of the elesctrospinning parameters, the effect of direct perfusion on DPSCs detachment from PCL electrospun scaffolds was investigated. The metabolic activity of the cells was determined for different adhesion times, flow rates and seeding densities and the pore wall shear stress was calculated for each flow rate. The cell morphology was evaluated through scanning electron and confocal microscopy imaging. In parallel, simulations with the software OpenFOAM were performed to study how parameters and inputs (initial glucose concentration, porosity and thickness of the scaffold) affect the outputs (cell volume fraction and substrate concentration) of a model of cell proliferation and glucose diffusion and consumption. The contribution of the oxygen in the Contois growth kinetics and the porosity variation with time due to polymer degradation was also evaluated. Initially, it was observed that only a pore size higher than the cell diameter allowed the infiltration of the cells through the scaffold. Then, it was observed that a higher adhesion time leaded to higher cell spreading in static conditions and, similar to smaller seeding densities and shear stresses, reduced cell detachment under perfusion. Regarding the phenomenological model, it was observed that the model is more responsive to the initial glucose concentration and scaffold porosity, and to the dimensionless parameters related to cell proliferation, death and nutrient uptake. Furthermore, the initial cell number had a more significant impact on mass transport than on cell growth. In this study, it was possible to obtain an electrospun scaffold and dynamic culture conditions suitable for the three-dimensional culture of DPSCs, and to elucidate the effects of transport limitations and of oxygen on cell growth, and of polymer degradation on mass transport were elucidated.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Diversos pesquisadores têm estudado o comportamento e o emprego de lajes nervuradas de concreto armado em sistemas estruturais na engenharia civil que demonstrem viabilidade sob o ponto de vista técnico e econômico. Por esta razão, inúmeros trabalhos têm sido publicados nos últimos anos respaldados por testes experimentais e análises numéricas. Neste contexto, diversos tipos de sistemas estruturais de lajes nervuradas têm sido desenvolvidos. Assim sendo, o objetivo desta investigação é o de contribuir, no que tange ao estudo do comportamento estrutural estático e dinâmico de lajes nervuradas de concreto armado, tendo em mente o emprego destas em sistemas estruturais na engenharia civil. Este trabalho de pesquisa objetiva também o estudo da resposta dinâmica de lajes nervuradas de concreto armado, sob o ponto de vista de conforto humano, especialmente quando essas estruturas encontram-se submetidas a atividades humanas rítmicas. A definição das ações dinâmicas atuantes sobre os modelos estruturais foi feita com base em resultados experimentais, que consideram grupos de indivíduos desenvolvendo atividades rítmicas correspondentes à ginástica aeróbica (atividade sincronizada). São empregadas técnicas usuais de discretização, via método dos elementos finitos (MEF), por meio do programa de elementos finitos ANSYS. No presente modelo computacional, as vigas de bordo, nervuras e a laje de concreto armado são simuladas por elementos finitos de casca. Os resultados obtidos ao longo do estudo, em termos das acelerações de pico, são confrontados e comparados com os limites propostos por normas de projeto, sob o ponto de vista do conforto humano. Com base na análise dinâmica das lajes nervuradas investigadas foi possível verificar que as atividades humanas rítmicas podem vir a gerar valores de acelerações de pico elevados e que violam os critérios de conforto humano. Deste modo, foi observado que, as acelerações nos modelos estudados, podem atingir níveis elevados de vibração que comprometem o conforto dos usuários. / Several researchers have studied the use of reinforced concrete ribbed slabs in civil engineering structural systems that can be viable when the technical and economical point of view is considered. For this reason, a lot of papers were published in the last years based on the experimental and numerical analysis of this slab type. In this context, several slab systems were developed and the reinforced concrete ribbed slabs is present among them. This way, this dissertation investigated the static and dynamic structural behaviour of reinforced concrete ribbed slabs used in civil engineering structures. This research work investigated the dynamic response of reinforced concrete ribbed slabs when subjected to the human rhythmic activities, focusing human comfort criteria. The dynamic loads were obtained through experimental tests with individuals carrying out rhythmic activities corresponding to aerobics (stimulated activities). The computational models are developed based on usual mesh refinement techniques present in finite element method simulations (FEM), implemented in the ANSYS program. In this computational model the reinforced concrete ribbed slabs and beams are represented by shell elements. The numerical results, in terms of peak accelerations, are compared with recommended limits proposed by design codes, under the point of view of human comfort. The reinforced concrete ribbed slabs dynamic analysis indicated that the actions produced by human rhythmic activities could generate peak accelerations that surpass design criteria limits developed for ensuring human comfort. Hence it was observed that the acceleration in the models studied, can achieve high levels of vibration that compromise the comfort of users.

Blister-Based Laser-Induced Forward-Transfer (BB LIFT) is a new method of particle transfer, capable of projecting complex and fragile particles into the gas phase. The technique uses a laser pulse to deform a metal or polymer film on a transparent substrate. The deformation of the film creates a blister which can mechanically desorb particles adhered to the surface. This thesis covers the study of the underlying mechanisms of blister formation in relation to laser pulse duration and film properties, whilst also advancing upon the technique by developing new methods for particle transfer of 0-dimensional point particles, 1-dimensional nanotubes, and 2-dimensional crystals. Study of the blister formation was carried out on uncoated 200-400 nm Titanium films, using 120 fs and 7 ns laser pulses. The blisters were studied by Atomic Force Microscopy and optical analysis. Furthermore a theoretical model for the blister formation using ns laser pulses was developed using a linear heat transfer model, showing a good agreement between experiment and theory. From this model mechanisms for blister formation under both of these pulse durations were developed. It was concluded that ns laser pulses heat the thin film causing it to undergo thermal expansion where the temperature and thermal expansion properties of the film define the blister. Femtosecond pulses form blisters due to confined ablation of the film at the interface of the transparent substrate and the film. The expanding gas forces the metal to stretch, where the deformation is dictated by the Young’s modulus of the material with the major factor being the thickness of the titanium film. The velocity distribution of the desorbed material was studied by means of mass spectroscopy. An ionising laser pulse was focused a known distance from the donor film. The ejected particles crossed the laser beam, and with a controlled delay of the time between the blister pulse and ionisation pulse the velocities could be determined for fullerenes (C60) and gold coated silicon nanoparticles (Auroshells). Utilising C60 as the desorbed material we could identify that for ns BB-LIFT the C60 was emitted at a velocity mostly dependent upon the heat expansion coefficient for the titanium film, resulting in a velocity approximating 100 ms-1 with a secondary emission of fullerenes due to evaporation from the hot surface. However, for fs BB-LIFT this evaporated emission was not present and the velocities could be adjusted from 7-70 ms-1 by varying the Ti film thickness from 360 nm to 210 nm respectively. These results are consistent with the mechanisms proposed earlier. The spread of the desorbed particle beam was also studied for nanosecond and femtosecond laser-induced blisters utilising auroshells and C60. This was accomplished by placing a receiver platform at a known distance in front of the donor film in order to collect the desorbed particles. The radial spread was then analysed indicating a flat deposit approximately the size of the initial blister with a 5 degree spread from that point. This indicates that the desorbed beam is highly directional. From this it could be ascertained that the blisters do not form from a single point position on the film but expand uniformly with the area of laser irradiation defining the growth point of the blister. A problem with many molecular beam techniques is that large fragile molecules or nanoparticles cannot be introduced to the gas phase without causing damage to the particles. Studies into the desorption of Auroshells (150 nm diameter), C60 (1 nm), PCBM (a fragile exohedral fullerene), carbon nanotubes (1x1000 nm), and 2D films (1x10000x10000 nm) showed that these materials were successfully transferred from the donor film to a receiver plate without causing damage to the particles. This was determined via Raman, NMR, AFM, and SEM measurements. Lastly a technique that allowed the growth of carbon nanotubes directly on the donor film utilising a a multi-layered substrate was developed, enabling the removal and deposition of the nanotubes, without exposing them to any chemical treatment.

Simbiose é a associação permanente entre dois ou mais organismos de espécies distintas, pelo menos durante uma parte do ciclo de vida. Existe uma grande diversidade de casos de simbiose, os quais são frequentemente classificados de acordo com os benefícios ou deficits no valor adaptativo do hospedeiro, i.e., mutualismo, comensalismo ou parasitismo. Outras características importantes são a localização, a dependência e o modo de transmissão dos simbiontes. O conjunto de organismos selecionado para este trabalho consiste de 58 bactérias que foram agrupadas segundo características das associações simbióticas que elas estabelecem. A análise comparativa das redes metabólicas foi realizada de forma sistêmica, analisando toda a rede sem fazer a partição em vias metabólicas selecionadas a priori. Duas maneiras de comparação foram utilizadas: (i) análise dos conjuntos de compostos e de reações, e (ii) análise da topologia das redes metabólicas modeladas como grafos de compostos. Como fruto dessas análises foi possível observar o contraste entre a conservação de um núcleo metabólico nas bactérias extracelulares, de vida livre e associadas à célula, e a ausência de partes comuns da rede metabólica nas intracelulares estritas. Nota-se que o grupo das mutualistas (MIV) foi o que especialmente contribuiu para os valores baixos de interseção para os conjuntos de compostos e de reações. Esses endocitobiontes apresentam uma proporção maior dos seus genomas dedicada ao metabolismo. Além disso, partes distintas do metabolismo foram conservadas em diferentes subconjuntos dessas bactérias intracelulares mutualistas. / Symbiosis is the permanent association between two or more organisms that are distinct, at least during a part of the life cycle. Cases of symbiosis are widely diverse and are often classified based on the benefits or the deficits on the host fitness, e.g., mutualism, commensalism or parasitism. Location, type of dependency and transmission of the symbionts are also important features. The data set is composed of 58 bacteria which were grouped according to the features of the symbiotic associations established by them. The metabolic network comparison was carried out in a systematic way, taking into account the whole network without previously selecting metabolic pathways. The comparison was performed by analysing: (i) the sets of compounds and reactions, and (ii) the topology of the metabolic networks modelled as compound graphs. A conserved metabolic core inside the groups of extracellular, free-living and cell-associated bacteria was observed, contrasting with the absence of common parts in the metabolic networks of the obligate intracellular bacteria. The group of mutualists (MIV) specially contributed to the low values of the intersections of sets of compounds and reactions. The portion of the genome dedicated to metabolism is higher in these endocytobionts and distinct parts of the metabolism were conserved in different subsets of the intracellular mutualist bacteria.

Made available in DSpace on 2015-03-26T13:28:05Z (GMT). No. of bitstreams: 1 texto completo.pdf: 4631651 bytes, checksum: 95ccdcc5c995d09a079445300b08fe3d (MD5) Previous issue date: 2010-11-12 / Fundação de Amparo a Pesquisa do Estado de Minas Gerais / Aiming at protecting the environment in its natural form from the actions, permanent preservation areas were created in order to outline unsuitable areas for land use, in order to maintain or preserve the original vegetation found at these locations. Although the Brazilian environmental law is considered to be quite satisfactory, some issues have contributed to make it somewhat slow-moving. Among such issues one may mention the deficiency on the means and materials to energetically investigate the belligerence against the environment, especially the ones related to the river basins. The functionality and effectiveness of the procedures integrated with the information generated by geoprocessing technologies may yield diagnoses and provide subsides able to to identify identify and measure areas of permanent preservation, strengthening the environmental monitoring actions as a way to support the legal instruments for controlling and monitoring these environments. Among the advantages of adopting automated processes, we highlight the reliability and repeatability of results which can then be organized and easily accessed from the digital databases. Therefore, although there are some methods which are able to automatically outline the permanent preservation areas, such methodologies are not available to the scientific community, as they are under patent processes or even for already having owners, or for the necessity of highly qualified personnel to perform a series of complex procedures. In our study, we developed a methodology for automatic outlining permanent preservation areas based on the conditions established by Resolution 303 of CONAMA (Conselho Nacional do Meio Ambiente - National Council for the Environment, public domain, with friendly interfaces and more intuitive procedures for the analyst. The advantages of automation compared to manual procedures are the increased efficiency of the procedures, fast achievement of results, and the possibility of storing and sharing digital data with the scientific community. It is also worth mentioning that for carrying out this project, the ArcGIS software was used as the basis for implementing the methodological procedures. The software was coupled with the altimetry data, for generating the Digital Elevation Model Watershed Conditioning, hydrographic data, and the map land use, regarding the area of study, which contains an area of 5510 ha. With this methodology adopting the geoprocessing technology, 2154.09 ha of APP were automatically outlined, around 39.09% of the area of study, being the the APP of the upper third of the basin along the ridge lines the category with the highest representation in the study area, totaling about 52.53% of protected areas. Conversely, the areas with slopes greater than the 45º had the lowest share among the categories surveyed, only 0.04% of total APPs. Upon completion of this research, a feasible methodology that can be easily adapted to new situations and basins, having a friendly interface, which does not require a long training operation by users, was achieved. Besides using a simple platform, this methodology will allow interface with other existing databases which will be into the public domain, being able to be customized to meet specific needs of public institutions such as the IEF (Instituto Estadual de Florestas - State Forestry Institute) of the State of Minas Gerais, among others. / Para proteger o meio ambiente das agressões humanas, foram criadas áreas de preservação permanente para delimitar áreas impróprias para o uso da terra, a fim de se manter ou preservar a cobertura vegetal original nestes locais. Embora a legislação ambiental brasileira seja considerada ampla, alguns fatores têm contribuído para torná-la pouco ágil. Dentre esses, destaca-se a deficiência em meios e materiais para apurar com vigor as agressões ao meio ambiente, ligadas principalmente às bacias hidrográficas. A funcionalidade e eficácia de procedimentos integrada às informações produzidas por tecnologias do geoprocessamento podem produzir diagnósticos e fornecer subsídios capazes de identificar e mensurar áreas de preservação permanente, fortalecendo as ações ambientais de monitoramento como suporte para os instrumentos jurídicos de controle e fiscalização desses ambientes. Dentre as vantagens de se adotarem processos automáticos, destacam-se a confiabilidade e a replicabilidade dos resultados, que podem então ser organizados e facilmente acessados sob a forma de bases de dados digitais. Desta forma, apesar de já existirem algumas metodologias capazes de realizar as delimitações das áreas de preservação permanente de forma automática, essas metodologias não se encontram disponíveis para a comunidade científica, ou por estarem em processo de patente, ou mesmo por serem proprietários, ou ainda por necessitar de pessoal altamente qualificado para executar uma série de rotinas complexas. Nesta pesquisa desenvolveu-se uma metodologia para delimitação automática de áreas de preservação permanente, com base nos condicionantes estabelecidos pela Resolução nº 303 do CONAMA, de domínio público, com interfaces amigáveis e rotinas mais intuitivas para o analista. As vantagens na automação em relação aos procedimentos manuais são o aumento da eficiência dos processos, a obtenção de resultados rápidos e a possibilidade de armazenamento e compartilhamento dos dados digitais com a comunidade científica. Assim, é oportuno mencionar que utilizou-se o software ArcGIS como base para implementação dos procedimentos metodológicos, aliado aos dados de altimetria para geração do Modelo Digital de Elevação Hidrograficamente Condicionado, além dos dados da hidrografia, correspondentes à área de estudo de 5.510 ha. Com esta metodologia adotando a tecnologia do geoprocessamento foram delimitados de forma automática 2.154,09 ha de APP cerca de (39,09 %) da área total de estudo, sendo as APPs de terço superior da bacia ao longo das linhas de cumeada a categoria com maior representação na área de estudo, somando aproximadamente (52,53 %), enquanto que as áreas com declividades superiores a 45o apresentaram a menor participação dentre as categorias mapeadas, apenas 0,04 % do total de APPs. Ao término desta pesquisa, obteve-se uma metodologia viável, que facilmente pode ser adaptada para novas situações e bacias, a qual não requer um longo treinamento de operação por parte dos usuários. A metodologia desenvolvida, além de utilizar uma plataforma simples, possibilita interface com outras bases de dados existentes e de domínio público e pode ser utilizada, de forma personalizada para atender às necessidades específicas de instituições públicas, como por exemplo, do Instituto Estadual de Florestas (IEF), em Minas Gerais, entre outras.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Diversos pesquisadores têm estudado o comportamento e o emprego de lajes nervuradas de concreto armado em sistemas estruturais na engenharia civil que demonstrem viabilidade sob o ponto de vista técnico e econômico. Por esta razão, inúmeros trabalhos têm sido publicados nos últimos anos respaldados por testes experimentais e análises numéricas. Neste contexto, diversos tipos de sistemas estruturais de lajes nervuradas têm sido desenvolvidos. Assim sendo, o objetivo desta investigação é o de contribuir, no que tange ao estudo do comportamento estrutural estático e dinâmico de lajes nervuradas de concreto armado, tendo em mente o emprego destas em sistemas estruturais na engenharia civil. Este trabalho de pesquisa objetiva também o estudo da resposta dinâmica de lajes nervuradas de concreto armado, sob o ponto de vista de conforto humano, especialmente quando essas estruturas encontram-se submetidas a atividades humanas rítmicas. A definição das ações dinâmicas atuantes sobre os modelos estruturais foi feita com base em resultados experimentais, que consideram grupos de indivíduos desenvolvendo atividades rítmicas correspondentes à ginástica aeróbica (atividade sincronizada). São empregadas técnicas usuais de discretização, via método dos elementos finitos (MEF), por meio do programa de elementos finitos ANSYS. No presente modelo computacional, as vigas de bordo, nervuras e a laje de concreto armado são simuladas por elementos finitos de casca. Os resultados obtidos ao longo do estudo, em termos das acelerações de pico, são confrontados e comparados com os limites propostos por normas de projeto, sob o ponto de vista do conforto humano. Com base na análise dinâmica das lajes nervuradas investigadas foi possível verificar que as atividades humanas rítmicas podem vir a gerar valores de acelerações de pico elevados e que violam os critérios de conforto humano. Deste modo, foi observado que, as acelerações nos modelos estudados, podem atingir níveis elevados de vibração que comprometem o conforto dos usuários. / Several researchers have studied the use of reinforced concrete ribbed slabs in civil engineering structural systems that can be viable when the technical and economical point of view is considered. For this reason, a lot of papers were published in the last years based on the experimental and numerical analysis of this slab type. In this context, several slab systems were developed and the reinforced concrete ribbed slabs is present among them. This way, this dissertation investigated the static and dynamic structural behaviour of reinforced concrete ribbed slabs used in civil engineering structures. This research work investigated the dynamic response of reinforced concrete ribbed slabs when subjected to the human rhythmic activities, focusing human comfort criteria. The dynamic loads were obtained through experimental tests with individuals carrying out rhythmic activities corresponding to aerobics (stimulated activities). The computational models are developed based on usual mesh refinement techniques present in finite element method simulations (FEM), implemented in the ANSYS program. In this computational model the reinforced concrete ribbed slabs and beams are represented by shell elements. The numerical results, in terms of peak accelerations, are compared with recommended limits proposed by design codes, under the point of view of human comfort. The reinforced concrete ribbed slabs dynamic analysis indicated that the actions produced by human rhythmic activities could generate peak accelerations that surpass design criteria limits developed for ensuring human comfort. Hence it was observed that the acceleration in the models studied, can achieve high levels of vibration that compromise the comfort of users.

Uma potencial alternativa para o transplante de tecidos é a engenharia de tecidos. Células-tronco mesenquimais e scaffolds eletrofiados são comumente utilizados nesta área devido à capacidade multipotente de diferenciação destas células e à rede de poros interconectados destas estruturas fibrosas. Além disso, bioreatores de perfusão podem ser utilizados para melhorar o transporte de nutrientes e reduzir o acúmulo de metabolitos tóxicos. Neste contexto, uma maneira de estudar e otimizar o sistema de cultivo é utilizar técnicas de modelagem para descrever interações ou processos individuais envolvidos no crescimento celular. Deste modo, o objetivo geral deste estudo é realizar o cultivo de células-tronco mesenquimais da polpa de dente decíduo (DPSCs) utilizando scaffolds tridimensionais eletrofiados de policaprolactona (PCL), biorreatores e técnicas de modelagem. Inicialmente foram testadas diferentes misturas de solventes (clorofórmio e metanol), a fim de produzir scaffolds com poros adequados ao cultivo tridimensional. Os diâmetros de fibra e de poro foram determinados por microscopia eletrônica de varredura (MEV). O crescimento e o metabolismo das células foram avaliados através da determinação da atividade metabólica e das concentrações de glicose e lactato do meio de cultivo, e a infiltração celular foi observada com a marcação do núcleo celular. Depois de estabelecidos os parâmetros de eletrofiação, o efeito da perfusão direta no desprendimento de DPSCs de scaffolds eletrofiados de PCL foi estudado. A atividade metabólica das células foi determinada para diferentes tempos de adesão, vazões e densidades de semeadura, e a tensão de cisalhamento na parede do poro foi calculada para cada vazão. A morfologia das células foi avaliada através de imagens de microscopia confocal e MEV. Paralelamente, foram realizadas simulações utilizando o software OpenFOAM para estudar como os parâmetros e variáveis de entrada (concentração inicial de glicose, porosidade e espessura do scaffold) afetam as saídas (fração volumétrica de células e concentração de substrato) de um modelo de proliferação celular que considera a difusão e o consumo de glicose. As contribuições do teor de oxigêno na cinética de crescimento de Contois e da variação da porosidade com o tempo devido à degradação do polímero também foram avaliadas. Inicialmente, foi observado que apenas um tamanho de poro maior que o diâmetro da célula permitiu a infiltração das células no scaffold. Então, observou-se que o aumento do tempo de adesão acarretou em maior espalhamento das células e, assim como a diminuição da densidade de semeadura e da tensão de cisalhamento, resultou em uma redução do desprendimento das células sob perfusão. Quanto ao modelo fenomenológico, observou-se maior sensibilidade à concentração inicial de glicose e à porosidade do scaffold, e aos parâmetros adimensionais relacionados à proliferação e morte celular e ao consumo de nutrientes. Além disso, o número inicial de células apresentou maior impacto no transporte de massa do que no crescimento celular. Neste estudo, foi possível obter scaffolds eletrofiados e conduções de cultivo dinâmico adequadas ao cultivo tridimensional de DPSCs, e elucidar os efeitos da limitação do transporte de massa e do oxigênio no crescimento celular, e da degradação do polímero no transporte de massa. / A potential alternative to tissue transplant is tissue engineering. Mesenchymal stem cells and electrospun scaffolds are commonly used in this field due to the multipotent differentiation capacity of these cells and the interconnected pore network of these fibrous structures. In addition, perfusion bioreactors can be used to enhance nutrient transport and reduce the accumulation of toxic metabolites. In this context, one way to study and optimize the culture system is to use modeling techniques to describe interactions or individual processes involved in cell growth. Thus, the objective of this study is to perform the three-dimensional culture of mesenchymal stem cells of dental pulp (DPSCs) using electrospun polycaprolactone (PCL) scaffolds, bioreactors and modeling techniques. Initially, different solvent mixtures (chloroform and methanol) were tested to produce scaffolds with pores suitable to three-dimensional culture. Fiber and pore diameter was determined using a scanning electron microscope. Cell growth and metabolism were evaluated through the metabolic activity and the culture medium concentration of glucose and lactate, and the cell infiltration was observed with cell nuclei staining. After the establishment of the elesctrospinning parameters, the effect of direct perfusion on DPSCs detachment from PCL electrospun scaffolds was investigated. The metabolic activity of the cells was determined for different adhesion times, flow rates and seeding densities and the pore wall shear stress was calculated for each flow rate. The cell morphology was evaluated through scanning electron and confocal microscopy imaging. In parallel, simulations with the software OpenFOAM were performed to study how parameters and inputs (initial glucose concentration, porosity and thickness of the scaffold) affect the outputs (cell volume fraction and substrate concentration) of a model of cell proliferation and glucose diffusion and consumption. The contribution of the oxygen in the Contois growth kinetics and the porosity variation with time due to polymer degradation was also evaluated. Initially, it was observed that only a pore size higher than the cell diameter allowed the infiltration of the cells through the scaffold. Then, it was observed that a higher adhesion time leaded to higher cell spreading in static conditions and, similar to smaller seeding densities and shear stresses, reduced cell detachment under perfusion. Regarding the phenomenological model, it was observed that the model is more responsive to the initial glucose concentration and scaffold porosity, and to the dimensionless parameters related to cell proliferation, death and nutrient uptake. Furthermore, the initial cell number had a more significant impact on mass transport than on cell growth. In this study, it was possible to obtain an electrospun scaffold and dynamic culture conditions suitable for the three-dimensional culture of DPSCs, and to elucidate the effects of transport limitations and of oxygen on cell growth, and of polymer degradation on mass transport were elucidated.

A Ressonância Magnética Nuclear (RMN) é uma importante técnica empregada nas principais áreas de conhecimento, tais como, Física, Química e Medicina. Importantes trabalhos da RMN aplicada ao estudo da dinâmica de moléculas em fluidos presentes em meios porosos permitiram que esta técnica ganhasse também notoriedade na indústria do petróleo. O presente projeto é fundamentado em alguns destes trabalhos seminais, reproduzindo, através de modelos físico-computacionais, os principais efeitos físicos da difusão e a consequente relaxação dos spins dos núcleos atômicos presentes nas moléculas dos fluidos imersos nos meios porosos. Os métodos teóricos utilizados para a interpretação dos parâmetros de relaxação transversal (T2) e longitudinal (T1), levam em consideração as propriedades macroscópicas da dinâmica de um ensemble de spins nucleares. Para a compreensão da difusão e relaxação nuclear em meios porosos, é de fundamental importância o emprego de métodos físico-computacionais que levam em consideração tanto a microestrutura quanto a difusão translacional dos spins nucleares através desses meios. Dentro dos modelos propostos nesta dissertação, foram utilizados conceitos básicos de mecânica estatística e de relaxação nuclear, resultando em programas envolvendo consideráveis recursos computacionais. Para a realização das simulações numéricas, foi necessária a construção da microestrutura digital dos meios porosos, usando como base do processo as imagens obtidas por microtomografia de raios-X 3D. Tendo disponível a microestrutura digital, o processo de difusão através do meio poroso e a consequente relaxação dos spins nucleares foram simulados através de modelos Random Walk, um exemplo clássico de Método de Monte Carlo. As simulações numéricas dos experimentos clássicos de RMN, empregados para a determinação de distribuições de tempos de relaxação transversal (conhecidas pela sigla CPMG), e mais avançados, para a determinação de taxas de troca entre diferentes sítios dos meios porosos (experimentos de troca ou Exchange), produziram importantes resultados para a compreensão da dinâmica de fluidos em meios porosos através de difusão translacional. / Nuclear Magnetic Resonance (NMR) is a versatile technique applied in many different areas of science such as Physics, Chemistry and Medicine. Several important NMR works applied in the study of the molecular dynamics of fluids inside porous media allowed this technique to become popular in the oil industry. This project is based on some of these seminal works. Using computational physics models, the main physical effects of diffusion and relaxation for the nuclear spins in an ensemble of molecules in a fluid permeating the porous media are reproduced. The theoretical methods used to interpret the transverse (T2) and longitudinal (T1) relaxation parameters take into consideration the macroscopic dynamical properties of an ensemble of nuclear spins. In order to comprehend the diffusion and relaxation in porous media, the use of computational physics methods that take into account the translational diffusion of the nuclear spins inside the media as well as its microstructure is essential. In the proposed models by this dissertation, basic statistical mechanics and nuclear relaxation concepts were used, resulting in programs that demand considerable computational resources. For the numerical simulations it was necessary to digitally construct the microstructure of the porous media and that was achieved with the use of X-ray 3D microtomography. On this digital microstructure, the diffusion process and the resulting relaxation of the nuclear spins were simulated with random walk models, an example of the Monte Carlo Method. The numerical simulation of classic NMR experiments, such as the one used to determine the distribution of relaxation times (known as CPMG), and more advanced ones, such as the one used to determine exchange rates between different sites (2D exchange experiments), produced fundamental results to the understanding of the fluid dynamics in porous media.