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In this work, a MFC fabrication procedure including two non-conventional techniques (partial baking and cap-sealing) were employed for the development of an up-scaled microfluidic fuel cell (MFC). Novel carbon-based electrode materials were employed, including carbon foam, fibre, and cloth, the results from which were compared with traditionally-employed carbon paper. The utilization of carbon cloth led to 15% of the maximum power that resulted from carbon paper; however, carbon fibre led to a 24.6% higher power density than carbon paper (normalized by electrode volume). When normalized by projected electrode area, the utilization of carbon foams resulted in power densities up to 42.5% higher than that from carbon paper. The impact of catalyst loading on MFC performance was also investigated, with an increase from 10.9 to 48.3 mgPt cm-2 resulting in a 195% increase in power density.

In this work, a MFC fabrication procedure including two non-conventional techniques (partial baking and cap-sealing) were employed for the development of an up-scaled microfluidic fuel cell (MFC). Novel carbon-based electrode materials were employed, including carbon foam, fibre, and cloth, the results from which were compared with traditionally-employed carbon paper. The utilization of carbon cloth led to 15% of the maximum power that resulted from carbon paper; however, carbon fibre led to a 24.6% higher power density than carbon paper (normalized by electrode volume). When normalized by projected electrode area, the utilization of carbon foams resulted in power densities up to 42.5% higher than that from carbon paper. The impact of catalyst loading on MFC performance was also investigated, with an increase from 10.9 to 48.3 mgPt cm-2 resulting in a 195% increase in power density.

Orientador: José Luz Silveira / Banca: Celso Eduardo Tuna / Banca: Diovana Aparecida dos Santos Napoleão / Resumo: Após as crises do petróleo de 1973 e de 1979, notou-se um efeito nocivo dos elevados custos e contínuo aumento dos preços do petróleo, razão pela qual aumentou o interesse pelas fontes de energias renováveis, amplamente disponíveis nos países em desenvolvimento. Em todo o mundo, tornaram-se objetivos prioritários de se economizar energia e buscar tecnologias racionais, levando-se sempre em consideração os efeitos relacionados ao meio ambiente. Por outro lado, a escassez iminente dos combustíveis fósseis tem exigido da humanidade o uso racional de energia primária e como conseqüência, novas plantas em versões tecnológicas mais desenvolvidas têm sido concebidas visando sempre o aumento da eficiência energética. Neste contexto, destacam-se as tecnologias de gaseificação de madeira, que consistem em técnicas de conversão da biomassa em gás combustível. O objetivo principal deste trabalho é o desenvolvimento e a demonstração de uma metodologia de dimensionamento de um gaseificador de leito fixo tipo Downdraft para uma alimentação de 100 kg/h de biomassa lignocelulósica. Avalia-se e escolhe-se os diversos equipamentos e acessórios necessários para a limpeza e acondicionamento do gás combustível para a alimentação de um motor de combustão interna. A análise técnica inclui além dos parâmetros construtivos específicos do gaseificador, o balanço de massa, de energia, e a determinação das eficiências, tanto para a eficiência a frio como para a eficiência a quente do gaseificador. A análise econômica inclui uma avaliação e obtenção dos custos tanto do gaseificador como do Motor de Combustão Interna acoplado, os custos dos equipamentos e acessórios da zona de gaseificação, os custos operacionais e os custos da instalação e amortização do projeto. / Abstract: After the oil crisis of 1973 and 1979, an effect of the increase costs and continuously increment of the oil prices was noted. For this reason, the interest for renewable energies sources widely available in developing countries was increased. The governments have formulated main objectives for energy savings and search for friendly technologies, taking into account the effects related with the environment. The new plants with improved technology have been conceived always taking into account energy savings and efficiency improvement. In this context, biomass gasification technologies are important, since they consist in techniques of parallel production of electricity and heat from just one fuel. The main objective of this work is to develop and to demonstrate a scale up methodology for the construction of a bed fix downdraft gasifier with a 100 kg/h supply using as raw material lignocelulosic biomass. It will be evaluated and analytically chosen the necessary accessories and equipments for the cleaning and preparation of the biomass fuel gas, then this gas will be used in a internal combustion engine. The technical analysis includes in addition to the constructive specifics parameters, the balance of mass, balance of energy and determination of the efficiencies for thermal generation and power generation (hot efficiencies or cold efficiencies, respectively. The economic analysis includes cost evaluation of the gasifier, internal combustion engine, equipment and accessories of the gasification zone, operational and installation and amortization of the project. / Mestre

It has long been established that the physical properties of the cell’s surrounding microenvironment has the ability to impose its influence on a range of cell processes. Morphology, differentiation, and proliferation have all been shown to be sensitive to the mechanical cues inherent within the extracellular matrix. Although significant advancements in microfabrication and cell mechanics have been made, questions regarding how physical interactions guide biological systems in three dimensions remain unanswered. By utilizing cocultured systems and microfabricated channeled topographies, we reveal that the three dimensional nature of the environment is capable of driving cell patterning. Contact guidance is the phenomenon by which cells will orient themselves along the geometric patterns of a substrate. Much of its research has focused on the nano/micro scale of two dimensional topographies, affecting alignment along grooves. We have revealed that contact guidance has the ability to impose far more complex cellular behaviour in three dimensional systems. Furthermore, by modulating the elements of confinement surrounding cells, we directed the balance of binding forces between cells and substrate leading to significantly different cell type dependent morphologies. By then altering the geometry of the topography, we revealed the ability to induce cell type separation in cocultured systems. These concepts led to the subsequent discovery that confinement induces three dimensional spheroidal growth of embryonic stem cells. These results reveal that the element of confinement not only influences patterning in three dimensions but guides the fundamental early stages processes essential to all life.

The work of this thesis consists of a systematic study of low-lying, proton single-particle states in Z = 51 isotopes. States in 113−125Sb were populated via (α,t) and (3He,d) single-proton adding reactions, performed on stable even tin isotopes. The Yale tandem accelerator delivered beams of 37.5-MeV α particles and 25-MeV 3He nuclei for the reactions. Outgoing tritons and deuterons were momentum analysed using an Enge split-pole spectrometer. To obtain absolute cross sections, the product of target thickness and spectrometer aperture size was calibrated for each target, using sub-Coulomb α- particle elastic scattering. States were observed up to ∼4 MeV excitation energy. Angular momentum transfer assignments were made through comparison of angular distributions and ratios of cross sections between different reactions. Relative spectroscopic factors ex- tracted through a DWBA analysis allowed energy centroids of the observed single-particle strength to be reconstructed.These measurements build upon the results of a previous (α,t) study, which was per- formed on the same targets. The previous measurements estimated that ∼ 90% of the πg7/2 and πh11/2 strength was held in the lowest-lying 7/2+ and 11/2− states, respectively. The difference in energy of these states increased with increasing neutron excess, and al- though they were in agreement with theoretical calculations that included contributions of the tensor interaction, poor statistics limited the information obtained regarding the weak fragments of high-j single-particle strength. Careful examination of these fragments, with the use of greater statistics, has been performed in this work. The (3He,d) measurements aid in making l transfer assignments and provide complementary information regarding the low-j states.Binding energies of the πg7/2 and πh11/2 orbitals measured in this work were compared to the energies of the lowest-lying 7/2+ and 11/2− states and theoretical calculations that include the tensor interaction. Though shifted higher in energy due to the fragmentation, trends in the centroids appear to be consistent with the lowest-lying states. The trend of the πg7/2–πh11/2 energy difference is in quantitative agreement with the predicted effects of the tensor interaction, with increasing neutron excess.

L’Europe et, en particulier, la France ont engagé une politique de transition énergétique, consistant à diminuer de 20 % les émissions de gaz à effet de serre, réduire de 20 % la consommation d'énergie et à atteindre 20 % d'énergies renouvelables dans le bouquet énergétique d'ici à 2020. Afin d’atteindre ces objectifs, plusieurs pistes doivent être déployées afin de promouvoir les énergies renouvelables qui sont de nature intermittente. Dans le cadre de ce projet de thèse on propose trois pistes pour contribuer au développement de ces énergies : la première consiste à déterminer la combinaison efficace des sources intermittentes et de sources fiables telle que les combustibles, ainsi que le montant optimal à investir dans les technologies renouvelables intermittentes sachant leur productivité imprévisible et variable. La deuxième piste de recherche consiste à déterminer, à l’aide d’un modèle dynamique, dans quelles circonstances on stocke de l’électricité et dans quelles circonstances on la délivre. Dans ce cadre, on essayera de déterminer un seuil optimal de stockage. La troisième piste consiste à déterminer comment on organise le secteur de l’effacement électrique. on appliquera le même principe que pour les parties précédentes : on a le modèle de base qui est l’intermittence modélisée par la variable aléatoire à laquelle on rajoutera l’effacement électrique. Dans le cadre de la thèse on espère publier trois articles complémentaires, un article sur chaque piste. Le lien entre ces trois pistes sera l’analyse et à la modélisation des différents instruments politiques, qui sont en ce moment en discussion au niveau français. L’objectif de cette analyse sera de faire un classement en fonction de leur capacité à atteindre un état optimal (ou à s’en approcher) sur chaque piste. / L’Europe et, en particulier, la France ont engagé une politique de transition énergétique, consistant à diminuer de 20 % les émissions de gaz à effet de serre, réduire de 20 % la consommation d'énergie et à atteindre 20 % d'énergies renouvelables dans le bouquet énergétique d'ici à 2020. Afin d’atteindre ces objectifs, plusieurs pistes doivent être déployées afin de promouvoir les énergies renouvelables qui sont de nature intermittente. Dans le cadre de ce projet de thèse on propose trois pistes pour contribuer au développement de ces énergies : la première consiste à déterminer la combinaison efficace des sources intermittentes et de sources fiables telle que les combustibles, ainsi que le montant optimal à investir dans les technologies renouvelables intermittentes sachant leur productivité imprévisible et variable. La deuxième piste de recherche consiste à déterminer, à l’aide d’un modèle dynamique, dans quelles circonstances on stocke de l’électricité et dans quelles circonstances on la délivre. Dans ce cadre, on essayera de déterminer un seuil optimal de stockage. La troisième piste consiste à déterminer comment on organise le secteur de l’effacement électrique. on appliquera le même principe que pour les parties précédentes : on a le modèle de base qui est l’intermittence modélisée par la variable aléatoire à laquelle on rajoutera l’effacement électrique. Dans le cadre de la thèse on espère publier trois articles complémentaires, un article sur chaque piste. Le lien entre ces trois pistes sera l’analyse et à la modélisation des différents instruments politiques, qui sont en ce moment en discussion au niveau français. L’objectif de cette analyse sera de faire un classement en fonction de leur capacité à atteindre un état optimal (ou à s’en approcher) sur chaque piste.

We approximate the vibrational energies of the symmetric and asymmetric stretches of the hydrogen bonds of the molecules H_3O_2^- and H_5O_2^+ by applying an improvement to the standard time-independent Born-Oppenheimer approximation. These two molecules are symmetric around a central hydrogen which participates in hydrogen bonding. Unlike the standard Born-Oppenheimer approximation, this approximation appropriately scales the hydrogen nuclei differently than the heavier oxygen nuclei. This results in significantly more accurate approximations for the stretching vibrational energies, which we compare to experimental measurements. / Master of Science

<p> A measurement of the cross section for the interaction of electromagnetic radiation with matter has been undertaken. Total cross sections for 29 photon energies from 121 keV to 10.8 MeV in 9 target elements from carbon to uranium have been realized and pair production cross sections, for energies above 2 MeV, deduced from the results. A direct measurement of the partial pair cross section for photons with energies from 1120 to 2754 keV in 6 target elements from titanium to lead has also been included.</p> / Thesis / Doctor of Philosophy (PhD)

<p> The hydrogenolysis reactions of a series of small paraffinic hydrocarbons (propane, n-butane, isobutane, isopentane, and neopentane) were examined using a continuous stirred-tank catalytic reactor. The catalyst was 0.5 weight percent ruthenium scipported on γ-alumina.</p> <p> The reaction orders with respect to hydrocarbon and hydrogen and the activation energies were determined for the reaction of each hydrocarbon. The order of reactivity was also examined.</p> <p> The product distributions from each hydrocarbon were measured over a wide range of conversion (5 to 80%) and several temperatures. Reaction networks proposing reversible adsorption-desorption of the hydrocarbons and irreversible rupture of the carbon-carbon bonds in the surface species were applied to these data.</p> <p> Some conclusions were made concerning the mechanism of hydrogenolysis and the rate-limiting step.</p> / Thesis / Doctor of Philosophy (PhD)