Zugl.: Berlin, Techn. Univ., Diss., 2004

Thesis (Ph. D.)--University of Wisconsin--Madison, 1982. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 204-217).

Thesis--Wisconsin. / Vita. Includes bibliographical references (leaves 225-238).

A research report submitted to the Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Medicine in the branch of Internal Medicine Johannesburg, 2014 / Background: Hypovitaminosis D is endemic worldwide. With the discovery of extra skeletal receptors for 1,25-dihydroxyvitamin D, the influence of vitamin D (25(OH)D3) deficiency has been investigated in metabolic diseases. In South Africa, little is known about 25(OH)D3 status. Aim: To investigate the 25(OH)D3 status in patients in Johannesburg, and to assess for any correlation between 25(OH)D3 , metabolic diseases and patient demographics and seasonal variation. Methods: A retrospective study of 1000 patients attending a northern suburb practice in Johannesburg was performed. Serum 25(OH)D3 levels, demographics and metabolic data were collected. Results: The mean 25(OH)D3 level was 24.45ng/ml and 74.3% were vitamin D deficient. There was no difference in mean 25(OH)D3 levels between age or gender groups. The lowest mean 25(OH)D3 was in the Indian race (p=0.001), HOMA-IR >2 (p=0.001), fasting glucose >7 (p=0.016) and highest was measured during the summer (p=0.001). There was a significant correlation between 25(OH)D3 level and cholesterol (p=0.001), however no correlation was found with hypertension or diabetes. Conclusion: This study reports a high incidence of hypovitaminosis D especially among Indians. In this study there was no correlation between hypovitaminosis D and metabolic factors except for a negative correlation with the cholesterol level.

A dissertation submitted to the Faculty of Medicine, University of the Witwatersrand, Johannesburg for the Degree of Masters of Science. December 1992. / Rouesettus aegyptiacus, the fruit bat is a crepuscular frugivore with no obvious access to either exogenous or endogenous sources of vitamin D. Therefore this animal's vitamin D status and endocrine system was investigated. Both captive and wild populations of fruit bats appear to be naturally in a vitamin D impoverished state. The serum concentration of the principle circulatory, metabolite [25(OH)D] is undetectable (< 4 ng/ml), Fruit bats possess the full compliment of enzymes associated with the vitamin D endocrine system. This was shown when labelled more polar metabolites were produced after the administration of 3H vitamin D3 and 3H 2S(OH)D3' Furthermore, a specific vitamin D binding protein (DBP) is present. After partial purification, it was revealed that this molecule is slightly larger in molecular mass than that of humans and baboons. The intraperitoneal administration of 25(OH)D3 revealed enhanced 1a-hydroxylase activity such that 1.7 times more 1,25(OH)2Ds was produced than 24,25(OH)2D3' The ratio of these di-hydroxylated metabolites conform with the ratio of these 2 metabolites in states of vitamin D deficiency and thus confirm the impoverished vitamin D status. Undetectable serum concentrations of 25(OH)D3 might therefore be explained by a limited exogenous vitamin D substrate (rotting fruit peels and fungi). Given the elevated 1a hydroxylase activity 1 the small amount'S of 25(OH)D produced would be rapidly converted to the active metabolite. The low concentration of active hormone appear adequate for the maintenance of mineral homeostasis as indicated by tightly controlled serum calcium (2.26 ± 0.17 mrnol/l), magnesium 01.16 + 0.24 mmol/l) and inorganic phosphorus (2.93 ± 1.01 mmol/I). Both vitamin D2 and vitamin D3 metabolites were detected in bat serum albeit in very small amounts, suggesting that fruit bats exploit both exogenous plant sources (skins of fruit - vitamin 1)2; fungi - vitamin D:3)and might indeed receive some U. V. light during their crepuscular forays to endogenously produce small amounts of vitamin D3 In conclusion, fruit bats appear to belong to a small group of animals that naturally have limited access to Vitamin D, yet the vitamin D endocrine system in these animals is no different to that of other mammals. These animals have adapted their vitamin D endocrine system to function well at the low hormone concentrations and they exhibit no pathological problems associated with relative vitamin D depletion. / AC2017

Abstract A 10-bit 1MSample/sec successive approximation A/D converter is described in this thesis. First, by a comparator designed with high input impedance is used for the load of the modified wide-swing R-2R D/A converter. The modified wide-swing R-2R D/A converter possesses a high impedance load thus the op-amp is used in the D/A converter can be neglected. Therefore, the usable swing range and the convertible speed are improved and the power consumption is reduced. Secondary, the modified wide-swing R-2R D/A converter that contains modified switch-circuit and matched-component is used to obtain the good voltage division thereby improving the accuracy. Finally, the modified timing skew-insensitive double-sampling S/H circuit is used to sample a high precision signal to the comparator. This modified timing skew-insensitive double-sampling S/H circuit consists of high-gain high-swing op-amp, CMOS dummy switches, and timing skew-insensitive technique for upgrading the precision and swing range. By using these improved circuits the overall speed, accuracy and swing range are improved. The proposed successive approximation A/D converter is designed by TSMC 1P4M 0.35£gm CMOS process, and it operates at 3.3V power supply voltage with 0.8 to 2.9V reference voltage. The simulation results show that DNL is 0.5LSB, INL is 1LSB, and the power consumption is 8mW.

Thesis--M. Med. Sc., University of Hong Kong, 1984. / Cover title.

Typescript (photocopy) / 2 v. : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physics, 1982

Thesis (Ph.D.)--Tufts University, 2005. / Adviser: Richard J. Wood. Submitted to the School of Nutrition Science and Policy. Includes bibliographical references. Access restricted to members of the Tufts University community. Also available via the World Wide Web;

Thesis (Ph.D.)--University of Adelaide, Dept. of Physics, 1982. / Typescript (photocopy).