Thesis (M.S.)--University of Michigan, 2005. / Includes bibliographical references.

Thesis (M.S.)--University of Louisville, 1995. / Typescript (Xerox copy). School of Dentistry, Department of Biological and Biophysical Sciences. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves [84]-97).

Thesis (M.S.)--University of Louisville, 1995. / Typescript (Xerox copy). School of Dentistry, Department of Biological and Biophysical Sciences. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves [84]-97).

No description available.

While photovoltaic (PV) manufacturing is on track to provide a substantial portion of world electricity generation, the growth of the industry is likely to be lower than desired to meet targets designed to mitigate climate change. Many different PV technologies have been developed, but PV modules based on Si are the dominant technology due to its low cost and relatively high energy conversion efficiencies. PV modules based on III-V materials are primarily used for aerospace applications due to their high cost and record-setting efficiencies. Traditional manufacturing techniques for III-V PV require expensive precursors, and have high capital costs and low throughput. Close-spaced vapor transport (CSVT) is an alternative technique for deposition of III-V materials that was invented in the 1960s but has not been fully developed for the production of PV devices. This work describes progress towards high efficiency solid-state GaAs solar cells produced by CSVT. Previous results have demonstrated good electronic quality of CSVT GaAs using photoelectrochemical cells, but such devices have not been demonstrated to be commercially practical. This work investigates the potential of CSVT to produce high-efficiency III-V PV by fabricating and characterizing GaAs films and simple homojunction solar cells. Chapter I describes the motivation and state of III-V PV research, and establishes basic device physics background. Chapter II gives details of film growth and device design and fabrication. Chapter III gives an overview of the film and device characterization methods employed. Chapter IV explores the primary limitations in the efficiency of the homojunction solar cells fabricated for this study and discusses some practical concerns in translating the technique to a manufacturing environment. Chapter V explores the electronically-active defects in both $n$-type films and in $p$-type absorbers of solar cells, which would be likely to limit the efficiency of devices optimized considering the results presented in Chapter IV. Chapter VI discusses some of the possible future directions for applying CSVT to more advanced device structures which are more commercially relevant, including the growth on alternative substrates and growth of ternary materials for passivating layers or multijunction cells. This dissertation includes previously published and unpublished co-authored material.

No description available.

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Resumo: O objetivo dessa tese foi avaliar os efeitos da intrusão ortodôntica no processo de reparação de lesão de furca grau III em cães, e da presença de fator de necrose tumoral alfa (TNFα) e/ou interleucina-1 beta (IL-1ß) na mecanoresposta de células com característica de osteócitos e osteoblastos in vitro. No estudo in vivo, lesões de furca grau III foram criadas em pré-molares inferiores de sete cães. Após 75 dias, as lesões foram aleatoriamente tratadas com cirurgia a retalho (OFD) associada ou não à regeneração tecidual guiada (GTR) e enxerto ósseo autógeno (BA). Após um mês, iniciou-se a intrusão ortodôntica (I) em parte dos dentes tratados pelas duas diferentes abordagens (grupos teste), por meio de ancoragem em miniimplantes. Os cães foram sacrificados após três meses de movimentação e um mês de contenção. Todas as lesões de furca grau III foram reduzidas para grau II ou I nos grupos teste. O mesmo foi observado em 50% das lesões nos grupos controle (sem movimentação). O nível de inserção clínico foi reduzido nos grupos teste, no final da contenção (p<0.01). O grupo OFD+I apresentou maior preenchimento ósseo que os demais grupos (p<0.05), demonstrando superioridade desta associação, no tratamento de lesões de furca grau III, em cães. Esses resultados levantaram a hipótese de que o processo de degradação da membrana e/ou enxerto ósseo interagiria negativamente sobre o processo de reparo quando associado a forças ortodônticas, pois a presença de mediadores inflamatórios estaria intensificada. É conhecido que a alteração tecidual proveniente da movimentação ortodôntica é resultado da ação de mediadores químicos sobre as células dos tecidos periodontais. Portanto, buscamos avaliar in vitro a ação de duas citocinas pró-inflamatórias, TNFα e IL-1ß, sobre células ósseas em presença e ausência de carga mecânica. / Abstract: The aim was to assess the effects of orthodontic intrusion on the healing of class III furcation lesions in dogs, and of the presence of tumor necrosis factor alpha (TNFα) and/or interleukin-1 beta (IL-1ß) on the mechanoresponse of osteocyte and osteoblast-like cells in vitro. In the in vivo study, class III furcation lesions were created in lower pre-molars of seven mongrel dogs. After 75 days, teeth were randomly treated with open flap debridment (OFD) associated or not to guided tissue regeneration (GTR) and bone autograft (BA). After one month, teeth were randomly assigned to orthodontic intrusion using mini-implants anchorage or no movement. Dogs were sacrificed after three months of movement and one month contention. All class III furcations were closed or reduced to class II or I lesions in the intrusion groups while 50% of the class III lesions in non-moved teeth remained unchanged. Clinical attachment level was reduced in the intrusion groups by the end of contention (p<0.01). OFD + I presented smaller soft tissues area and larger bone tissue area than other groups (p<0.05). Orthodontic intrusion with mini-implants anchorage improved healing of class III furcation defects after OFD in dogs. Based on these results we hypothesized that degradation of membrane and/or bone autograft can negatively interfere on repair when associated to orthodontic movement because inflammatory mediators are intensified. It's known that cytokines are present during orthodontic movement which are acting on periodontal cells. Therefore we evaluated in vitro the effects of two pro-inflammatory cytokines, TNFα and IL-1ß, on bone cells in presence or absence of mechanical loading. / Orientador: Joni Augusto Cirelli / Coorientador: Rosemary Adriana Chiérici Marcantonio / Banca: Ana Cláudia Moreira Melo / Banca: Enilson Antonio Sallum / Banca: Ary dos Santos Pinto / Banca: Silvana Regina Perez Orrico / Doutor

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Photovoltaics is an exciting area of research with the potential to completely change the world's energy landscape. Silicon still dominates the photovoltaics market and shows no sign of being overtaken by other materials systems for large scale manufacture. Huge strides have been made in recent years to reduce the cost of solar modules, mainly through the introduction of mass production solar panel plants. However producing very pure single crystalline silicon is still a relatively expensive, energy intensive process. If cheaper less pure silicon could be cast into multi-crystalline ingots, without significant losses to the conversion efficiency this could be a game changer in the photovoltaics industry. For this to happen we need to have greater knowledge and understanding of the role of metallic impurities in solar silicon. If we can find ways to passivate or getter these impurities in cost effective processes that lend themselves to mass production then this would be the key to cost effective solar energy. In the work in this thesis I have investigated some of the most common and most harmful metallic impurities in silicon solar cells using a combination of Deep Level Transient Spectroscopy (DLTS), Capacitance Voltage (CV) measurements, Secondary Ion Mass Spectroscopy and Tunnelling Electron Microscopy (TEM). The specific transition metals I studied were iron, as it is one of the most common impurities and also titanium and molybdenum, because they are very harmful, have slow diffusivities and hard to get rid of with traditional gettering techniques. I have then looked at using hydrogen to electrically passivate these defects, and show evidence that hydrogen passivation is possible for interstitially incorporated titanium in silicon, but is unlikely to happen for interstitially incorporated iron. Another important part of this thesis was the observation and characterisation of molybdenum nano-precipitates in silicon. We have observed the nano-precipitates both electrically in DLTS, and physically in TEM. The precipitates have very interesting electrical properties, and appear to be very strong minority carrier recombination centres, which would have a very negative effect on solar cell performance. It is possible that these nano-precipitates could form from any of the slow diffusing transition metals, and could be a key reason to explain the efficiency gap between low purity cast silicon and high purity single crystal silicon.