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This thesis reports structure-function assessments made using site-directed mutagenesis of the human enzyme 5alpha-reductase (5AR), an enzyme crucial for normal masculine development. These assessments utilised the differences between the two forms of the enzyme in affinity for testosterone and sensitivity to the competitive inhibitor Finasteride.Although first described in the 1950s, the enzyme has never been isolated and biochemical studies generated conflicting data. In some reports the enzyme was said to operate at a pH of 5.5 whereas others considered the pH optimum was more alkaline than this. Similarly, the affinity for testosterone was reported as being around 3muM and around 0.5muM and different sensitivities to the competitive inhibitor Finasteride also were reported. These differences were resolved in the period 1989 1991 by isolation of cDNAs coding for two forms of 5AR. These were termed 5AR1 and 5AR2. It is now known that 5AR1 operates at the more alkaline pH, has the lower affinity for testosterone and is the more resistant to Finasteride. 5AR1 is present to a greater extent in the periphery with 5AR2 predominating in the prostate.Isolation of the cDNAs coding for 5AR1 and 5AR2 and the differing characteristics of the two enzymes, have provided the means to investigate structure-function relationships using site-directed mutagenesis. This approach enables identification of residues important for the binding of substrate and inhibitor by the two forms of human 5AR.At the commencement of these studies the residues -AVFA- had been identified as comprising part of the substrate/inhibitor binding site of human 5AR1. As the analogous residues, -VSIV- of rat 5AR1 also had been shown to contribute to this binding, it had been suggested that the analogous residues -GALA- in human 5AR2 may form its substrate/inhibitor binding domain. There was however no ++ / experimental evidence to support this suggestion. Similarly the roles of particular residues identified as being involved in substrate/inhibitor binding by 5AR had not been subjected to significant study. Accordingly the experiments conducted were designed to address several unanswered questions. The most significant of these questions was are the residues -GALA- involved in substrate/inhibitor binding by human 5AR2 and if not what residues are in fact involved in this binding.Rat 5AR1 exhibits a different mechanism of Finasteride inhibition than does rat 5AR2and both of the human enzymes. This difference had been attributed to expression of a cysteine at position 146 in rat 5AR1 rather than the arginine expressed at the analogous position in rat 5AR2 and the human enzymes. The studies reported here for the mutation of the relevant arginine to cysteine do not substantiate the suggestion that cysteine 146 is responsible for the unique mechanism of inhibition by Finasteride shown by rat 5AR1.Although residues G34 and H231 in human 5AR2 had been shown important for substrate binding by this enzyme, the roles of these residues in inhibitor binding had not been examined nor had the roles of the analogous residues in human 5ARI (G39 and H236). Experiments designed to determine these factors demonstrated a requirement of both G34 and H231 for substrate and inhibitor binding by human 5AR2. The analogous residues in 5AR1 were however only required for the binding of inhibitor.The tetrapeptide -AVFA- had been shown to be involved in substrate/inhibitor binding by human 5AR1 but no assessment had been made of the relative roles of the individual amino acids comprising this tetrapeptide. Replacing residues in human 5AR1 with the corresponding residues from rat 5AR1 demonstrated a requirement in human 5AR1 of A26 and V27 for inhibitor but not substrate binding, possibly as a ++ / result of their conformational and electrostatic effects respectively. The branched chain residue V27 was found to be required for both substrate and inhibitor binding and the terminal alanine (A29) did not appear to play a significant role in the binding of either substrate or inhibitor. These studies also permitted an indirect assessment of the contribution of all four residues of the tetrapeptide -VSIV- to substrate binding by rat 5AR1 and showed that while the tripeptide -SIV- is important for inhibitor binding, the initial valine is not.As mentioned above the main impetus of these studies was to determine if residues -GALA- were involved in substrate/inhibitor binding by human 5AR2. Characterisation of mutants in which -GALA- in human 5AR2 was substituted with -AVFA- from 5AR1 and vice versa, showed these residues do not comprise the substrate/inhibitor binding site of human 5AR2.From studies of a chimeric constructs of human 5AR1 and 5AR2 residues involved in substrate/inhibitor binding by human 5AR2 were mapped to the first 40 amino acid residues. Mutations of 6 residue clusters showed the hexapeptide -ATLVAL(r15-20) in 5AR2 to contribute significantly to substrate/inhibitor binding. Further studies of this hexapeptide showed that residues -ATL- but not -VAL- form part of the substrate/inhibitor binding domain of human 5AR2.

La détonabilité d'un mélange réactif peut être évaluée par la mesure du diamètre critique de diffraction dc de la détonation d'un tube l'espace libre. dc est relié la largeur de la cellule de détonation (a) par dc = kca, ou kc = 13 pour les mélanges combustible-O2. dans le but d'expliquer l'augmentation de kc avec la dilution du mélange par un gaz inerte, une étude expérimentale et numérique a été menée sur la diffraction de la détonation du mélange C2H2+2,5O2+z Ar (0 inf ou égal à z inf ou égal à 15) dans des cônes d'ouverture comprise entre 10 et 180. L'utilisation d'un schéma détaillé de cinétique chimique a montré que diluer un mélange réactif avec un inerte contribue à retarder la libération d'une partie de l'énergie chimique. Un modèle de cinétique réduit en 2 étapes a été développé et utilisé dans des simulations2D. L'accord entre les résultats expérimentaux et numériques révèle le rôle fondamental de la loi de libération de l'énergie chimique dans les processus stationnaire et transitoire des détonations.

Microbial community interactions within many ecosystems are still relatively unknown. Investigating links between environmental dynamics and shifting pelagic bacterial community structures on the Texas-Louisiana shelf, Eubacterial community profiles of Operational Taxonomic Units (OTUs) were generated using Automated Ribosomal Intergenic Spacer Analysis (ARISA) of the 16S rDNA and 23S rDNA intergenic spacer region. This ITS region is highly variable in both length and sequence. Community diversity was assessed by the comparison of ARISA-generated community fingerprints of samples collected from four distinct regions along the Texas-Louisiana shelf in a cross-shelf pattern on 10m, 20m, and 40m isobaths. Incubations of samples with a thymidine analog, 5-Bromodeoxyuridine (BrdU), allowed for the isolation and analysis of the actively growing subset within the total bacterial population. Community composition was determined through the construction of clone libraries for sequencing and putative phyla affiliation of community 16 rRNA genes. Hydrographic data were also collected for analysis of shifts in microbial community diversity correlated with a variety of influential environmental factors. ARISA profiles of Eubacterial species richness suggest strong distinction between the two communities found within Zones A and C along the Texas-Louisiana Shelf. Further analysis of salinity gradients originating from the two main fluvial sources, the Mississippi and the Atchafalaya Rivers, identified possible sources of variation between the individual communities. Whereas composition of these communities remains discrete between regions, the active subset of the population becomes more similar across the shelf through the summer. Possibly due to undersampling of hypoxic sites, no relationship could be determined between hypoxia formation and the Eubacterial community dynamics. Several OTUs within the communities were identifiable as α - and β - Proteobacteria, Actinobacteria, Synechococcus, Prochlorococcus, and Cytophaga/Flavobacterium/Bacteroides. Through validation studies of 5-Bromodeoxyuridine field sampling, this study indicates the power of BrdU incorporation and ARISA analysis to study a dynamic environmental system and explore the factors that determine the structure of the pelagic community on the Texas-Louisiana Shelf.

Firms that face seasonal demand account for an important fraction of the U.S. economy. However, there is surprisingly little evidence on these firms' financing decisions. Yet, studying these decisions provides a natural setting to shed light on the types of capital (i.e. cash or debt) that firms use to manage short-term financing needs. Using seasonal firms as a setting to examine this issue, I show that seasonal financing needs are met with debt with low exposure to information asymmetry, such as short-term debt and trade credit. I further show that cash reserves, which have high carrying costs and can at time lead to agency problems, are not used for seasonal financing needs. Further, as financial flexibility theory would predict, I document that seasonal firms maintain more conservative financial policies to increase the ability to use debt for short-term financing needs. Specifically, seasonal firms are less levered and have long-term debt with a longer average maturity. Further, seasonal firms adjust toward leverage targets slower during fiscal quarters when debt is used for short-term financing. Overall, my findings indicate that firms minimize costs associated with short-term financing needs by using debt with low issuance costs and the use of this debt impacts the overall capital structure of the firm.

Thesis (Ph. D.)--Auburn University. / Abstract. Vita. Includes bibliographical references (p. 184-188).

京都大学 / 0048 / 新制・課程博士 / 博士(人間・環境学) / 甲第19072号 / 人博第725号 / 新制||人||174(附属図書館) / 26||人博||725(吉田南総合図書館) / 32023 / 京都大学大学院人間・環境学研究科相関環境学専攻 / (主査)教授 内本 喜晴, 教授 加藤 立久, 教授 吉田 寿雄 / 学位規則第4条第1項該当 / Doctor of Human and Environmental Studies / Kyoto University / DGAM

<p>The purpose of this dissertation is to determine the influence of spatial and industrial structure on the volume and composition of trade among Canadian and American regions. In so doing, it is intended to provide a better understanding of the causes and effects of trade on regions, the potential\ for further economic integration and the policy implications thereof.</p> <p>Both empirical and analytical modelling methods are used to analyze regional trade. Empirically, it is found that Canada-U.S. trade is heavily influenced by the spatial configuration of regions as well as their i1dustrial composition. It is also established that after controlling for distance and the industrial composition, there is a strong potential for further economic integration among Canadian and American regions. However, this potential is less than other studies have suggested.</p> <p>Using an analytical model, it is demonstrates that the welfare implications of i economic integration depends on the relative size of the trading regions, their I respective national markets and the tradeability of intermediate goods.</p> <p>Finally, the analysis shows that the potential for public policy to influence the I degree of integration and what form those policies might take depends crucially on the characteristics (geographic and industrial) of the trading regions.</p> / Doctor of Philosophy (PhD)

Durant la nuit, le radical nitrate (NO3) est le principal oxydant troposphérique des composés organiques. La compréhension de l'implication des composés organiques dans les processus de chimie troposphérique exige donc une connaissance des constantes cinétiques de leurs réactions avec le radical NO3. Toutefois, au regard du nombre considérable de composés organiques émis ou formés dans la troposphère, il est difficilement envisageable d'appréhender la réactivité de chaque composé en nous reposant exclusivement sur des études de laboratoire. Celles-ci se doivent d'être complétées par l'usage de méthodes prédictives. Nous avons donc, au cours de ce travail, développé une relation de type structure-réactivité (SAR) qui permet le calcul des constantes de vitesse des réactions des composés organiques avec le radical nitrate. Cette méthode prédictive empirique permet d'estimer la réactivité d'un composé à partir de sa structure moléculaire et a été élaborée à partir de constantes cinétiques expérimentales publiées dans la littérature. De plus, conjointement au développement de cette SAR, les constantes cinétiques des réactions d'aldéhydes et d'éthers insaturés avec le radical nitrate ont été mesurées au laboratoire. Ces études expérimentales ont ainsi contribué à étoffer la base de données cinétiques sur laquelle repose cette SAR afin de permettre son parachèvement. Cette SAR reproduit, à un facteur deux près, plus de 90% des constantes cinétiques des alcènes et des composés aliphatiques oxygénés saturés et insaturés / The nitrate radical (NO3) is the main oxidant of organic compounds in the night-time troposphere. Thus, comprehension of organic compounds involvement in tropospheric chemical processes requires the knowledge of the rate coefficients for their reactions with the nitrate radical. Nevertheless, considering the wide range of organic compounds emitted or formed in the atmosphere, it is difficult to determine the reactivity of each compound only with laboratory studies. Thereby, these experimental studies have to be completed by predictive methods. In this study, a group-additivity method is therefore used to develop a new Structure-Activity Relationship (SAR) which allows prediction of the rate constants for reactions of organic compounds with the NO3 radical. This empirical method is based on the prediction of a rate constant leaning only on the molecular structure of the organic compound. It relies on experimental rate constants available in the literature. Moreover, the rate constants of unsaturated aldehydes and ethers with the nitrate radical have been measured. Thereby, these experimental studies contribute to expend the kinetic database used for the SAR development and allow its improvement. For saturated and unsaturated oxygenated compounds, more than 90% of the rate constants are reproduced within a factor of two

in English The submitted thesis adresses the processing of material culture from the archaeological excavation in Velké Přílepy (district of Prague-west), where the settlement of Funnel Beaker culture was uncovered. The study is a sequel to my bacheolor's thesis (defended in 2010) which evaluated only one part of the excavated settlement and significantly improves its corpus of finds. Therefore there is now a complete analysis of the whole widespread settlement area in an open position without any fortification. Close to sixty structures were documented and dated (based on ceramic analysis) to the Siřem and Salzmündphase of Funnel Beaker culture on this researched area. Thanks to the excavation, an exceptionally rich collection of ceramic production from the Early Eneolithic period (10 105 pieces altogether) exists. Other settlements belonging to the Funnel Beaker culture in the vicinity of Velké Přílepy are also considered in this thesis. Together with this settlement, they create a unique area of settlements of the aforementioned culture.