Reproduction de : Thèse de doctorat : Sciences Naturelles : Faculté des sciences de Paris : 1879. / Titre provenant de la page de titre du document numérisé.

Thesis (M.P.H.)--University of Hong Kong, 2009. / Includes bibliographical references (p. 36-39).

Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references. Available also from UMI/Dissertation Abstracts International.

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Several investigators have suggested that "upper" neural tube defects (NTD's)--anencephaly, encephalocele, and thoracic spina bifida--are etiologically different from "lower" NTD's (lumbo-sacral spina bifida). This hypothesis was primarily based on the observations that the two types have different sex ratios and recurrence rates and that the NTD cases within one sibship are concordant for NTD type. In order to test this, the above figures were calculated in a sample of NTD probands from Montreal and Newfoundland. The findings were not consistent with the hypothesis. However, a previously unreported finding was observed: the frequency of twinning was significantly higher in the near relatives of upper NTD probands than in those of lower NTD probands or of controls. This curious association between upper NTD's and twinning may be explained by a familial factor predisposing to a delay early in development. This delay could also explain any differences observed in upper and lower NTD groups.

The purpose of this research program was to measure the efficiency of evacuated tube solar collectors under various operating conditions including: the angle of inclination towards the incident solar radiation, heat transfer fluid flow rate, glazing installation, and number of evacuated tubes. The operating conditions and configurations were chosen to represent realistic or probable installation scenarios and environmental conditions. Furthermore, the research aimed to identify the suitability of evacuated tube solar collectors to each of the scenarios. The scope of the research project was limited to the efficiency of a single tube, and various configurations of a 32-tube panel, not the entire solar domestic hot water or space heating system. Thus, factors such as heat loss in the tubing, solar storage tank, and heat exchanger efficiency were not investigated. The findings indicated that efficiency varied by approximately 5% in general between the different collector configurations.

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