Thesis (Ph. D.)--Ohio State University, 2008. / Title from first page of PDF file. Includes bibliographical references (p. 115-119).

Thesis (M.S.)--Missouri State University, 2008. / "August 2008." Includes bibliographical references (leaves 45-51). Also available online.

Thesis (Ph. D.)--University of North Carolina at Chapel Hill, 1996. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (M. Phil.)--University of Hong Kong, 2000. / Includes bibliographical references (leaves 120-134).

Thesis (Ph. D.)--University of Hong Kong, 2005.

Thesis (Ph. D.)--University of North Carolina at Chapel Hill, 1996. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--Ohio State University, 2006. / Title from first page of PDF file. Includes bibliographical references (p. 153-159).

Thesis (Ph. D.)--University of Hong Kong, 2005. / Title proper from title frame. Also available in printed format.

Orientador: José Buratini Junior / Resumo: A comunicação entre o oócito e células somáticas adjacentes é essencial para a diferenciação do complexo cumulus-oócito (COC). Essa comunicação é proporcionada por processos citoplasmáticos trans-zonais (TZP) que penetram através da zona pelúcida e atingem a membrana do oócito, onde junções do tipo gap permitem transporte bidirecional de sinais elétricos e moléculas reguladoras. A maturação oócitária in vivo é controlada por gonadotrofinas e peptídeos intra-ovarianos e desencadeada pelo pico de LH. Este, induz a expressão dos fatores EGF-like que desencadeiam uma série de fatores que levam a fosforilação das conexinas, e com isso o fechamento de junções gap e consequentemente perda dos efeitos inibitórios do monofosfato cíclico de adenosina (AMPc) e monofosfato cíclico de guanosina (GMPc), proporcionando assim a retomada da meiose. O objetivo deste trabalho é avaliar os efeitos da inclusão de uma fase de pré maturação seguida da maturação in vitro sobre a progressão da meiose, funcionalidade das junções gap e produção embrionária. A pré maturação foi empregada utilizando componentes de ordem fisiológica encontradas no ambiente folicular, e esta, foi capaz de retardar a quebra da vesícula germinativa (VGBD), enquanto favoreceu a comunicação entre oócito e células do cumulus, o que acreditamos ser beneficial para o desenvolvimento oocitário in vitro. No entanto, quando seguida da maturação in vitro também utilizando componentes fisiológicos, foi capaz de prod... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The maturation of the cumulus oocyte complex (COC) is triggered by the ovulatory LH surge in vivo, and precociously induced when the COC is removed from the follicle. Natriuretic peptide type C (NPPC) plays a central role in maintaining meiotic arrest in vivo and delays GVBD while increasing oocytecumulus communication during IVM in cattle. In this study we first tested the hypothesis that follicular steroids (estradiol, progesterone and androstenedione) combined with FSH at approximately physiological levels cooperate with NPPC to delay GVBD and to maintain oocyte-cumulus communication. Then, we assessed the effects of follicular steroids, NPPC and the combination of both in a pre-IVM culture followed by IVM induced with AREG on embryo production. Follicular steroids combined with NPPC was most effective in increasing the proportion of GV oocytes in Bos indicus, although follicular steroids did not significantly enhance the effect of NPPC in Bos Taurus. . Moreover, follicular steroids enhanced the ability of NPPC to increase the proportion of COCs with opened GAP junctions. The addition of follicular steroids and/or NPPC to a pre- IVM culture did not alter blastocyst production after IVF. In conclusion, the combination of follicular steroids with NPPC can alter GVBD dynamics and cell communication favorably to oocyte developmental competence, but when used in a pre-IVM culture followed by induction of COC maturation with AREG and IVF, it did not increase e... (Complete abstract click electronic access below) / Mestre

The work described in this thesis investigates the effects of bandstructure modifications, brought about by Landau confinement, hydrostatic pressure and uniaxial stress, on recombination processes in narrow-gap materials and laser diodes. The effects of Landau confinement on the characteristics of InSb-based emission devices operating at a wavelength of ~5mum at 77K were studied. The change in performance due to the magnetic field applied along both the cavity and the growth direction and thereby simulating quasi-quantum wire and quasi-quantum dot structures clearly demonstrated the benefits, such as reduced threshold and temperature sensitivity, gained by the reduced dimensionality. On the other hand, suppression of LO-phonon emission due to the discrete nature of the density of states was observed, for the first time, in an interband laser device. Interband recombination dynamics were studied in In1-xGaxSb and PbSe over a range of excited carrier densities and temperatures down to 30K. Detailed analysis of the results found that the Auger-1 mechanism is reduced in In1-xGaxSb as a function of Ga-fraction due to the increased bandgap energy, in good agreement with theoretical predictions. In PbSe, the Auger-1 rate was observed to dominate at low excited carrier concentrations in spite of near-mirror bands, and was found to be approximately constant between 300K and 70K and was seen to be quenched in the low temperature regime. Stimulated emission was seen to be the most efficient recombination mechanism at high excited carrier densities at low temperatures. The Auger coefficient in PbSe was found to be one to two orders of magnitude lower than for materials with a Kane band structure (Hg1-xCdxTe) with comparable bandgap. An experimental technique was developed which enables measurements at high hydrostatic pressures and high magnetic fields at low temperatures. Hydrostatic pressures were applied to a 1.5mum laser diode at different temperatures revealing the effects of pressure on the band structure and hence the laser characteristics. A visible laser diode was measured under the simultaneous application of hydrostatic pressure and uniaxial stress. The change in performance was satisfactorily explained in terms of leakage of carriers into the X-minimum in the cladding region, the process that has been suspected of being one of the major loss mechanisms in visible laser diodes. This copy of the thesis has been supplied on the condition that anyone who consults it is understood to recognise that the copyright rests with its author and that no quotation from the thesis and no information derived from it may be published without the prior written consent of the author or the University (as may be appropriate).