Due to their ability to simultaneously reduce fuel consumption and NOx emissions, Controlled Auto Ignition (CAI) and HCCI combustion processes have been extensively researched over the last decade and adopted on prototype gasoline engines. These combustion processes were initially achieved on conventional two-stroke ported gasoline engines, but there have been significantly fewer studies carried out on the CAI combustion in two-stroke engines. This is primarily due to the inherent problems associated with conventional two-stroke engine intake and exhaust ports. Meanwhile, engine downsizing has been actively researched and developed as an effective means to improve the vehicle’s fuel economy. This is achieved by operating the engine at higher load regions of lower fuel consumption and by reducing the number of cylinders. However, aggressive downsizing of the current 4-stroke gasoline engine is limited by the knocking combustion and high peak cylinder pressure. As an alternative approach to engine downsizing, boosted two-stroke operation is being researched. In this thesis, it has been shown that the CAI combustion in the two-stroke cycle could be readily achieved at part-load conditions with significant reductions in CO and uHC emissions when compared to typical SI combustion in a single cylinder gasoline direct injection camless engine. In addition, extensive engine experiments have been performed to determine the optimum boosting for minimum fuel consumption during the two-stroke operation. In order to minimise the air short-circuiting rate, the intake and exhaust valve timings were varied and optimised. It is shown that the lean operation under boosted condition can extend the range of CAI combustion and increase combustion and thermal efficiencies as well as producing much lower CO and HC emissions. By means of the cycle-resolved in-cylinder measurements and heat release analysis, the improvement in combustion and thermal efficiencies were attributed to the improved in-cylinder mixture, optimised autoignition, and combustion phases. Finally, in view of the increased use of ethanol in gasoline engines, E15 and E85 were used and their effect on engine performance, fuel economy and exhaust emissions were investigated.

Mediation is used to separate direct and indirect effects of an exposure variable on anoutcome variable. In this thesis, a mediation model is extended to account for censoredmediator and outcome variable. The two-part framework is used to account for thecensoring. The counterfactual based causal effects of this model are derived. A MonteCarlo study is performed to evaluate the behaviour of the causal effects accounting forcensoring, together with a comparison with methods for estimating the causal effectswithout accounting for censoring. The results of the Monte Carlo study show that theeffects accounting for censoring have substantially smaller bias when censoring is present.The proposed effects also seem to have a low cost with unbiased estimates for samplesizes as small as 100 for the two-part mediator model. In the case of limited mediatorand outcome, sample sizes larger than 300 is required for reliable improvements. A smallsensitivity analysis stresses the need of further development of the two-part models.

published_or_final_version / Asian Studies / Master / Master of Arts

Dans le thyrocyte normal, la TSH active une voie dépendante de l’adénylyl cyclase/AMPc, qui représente l’une des trois voies mitogéniques de la thyroïde. La cascade de signalisation de la TSH diffère des deux autres voies dans sa capacité à induire à la fois la prolifération et la différenciation, comprenant la synthèse et la sécrétion des hormones thyroïdiennes. Identifier les acteurs de cette cascade de signalisation, ainsi que les interactions entre effecteurs, est donc très important pour la compréhension de la fonction de la cellule thyroïdienne. C’est dans ce cadre que s’insère notre travail au cours duquel nous nous sommes intéressés au récepteur de la TSH ainsi qu’à une protéine récemment identifiée dans le laboratoire et dont l’expression est modulée en réponse à la TSH dans la thyroïde : C3VS. C3VS est une protéine qui présente six motifs ankyrine et une tirette à leucine et dont la fonction était inconnue à l'époque. Dans un premier temps, nous avons contribué à l’obtention de la séquence codante complète du C3VS de chien, puis, l'identification des partenaires d'une protéine pouvant aider à caractériser sa fonction, nous nous sommes proposé de rechercher les partenaires potentiels de la région N-terminale de C3VS par la méthode double-hybride. Nous avons étudié la distribution tissulaire et la régulation par la TSH de différents partenaires isolés. Parmi eux, SUG1, une ATPase du protéasome 26S, a été étudiée plus avant mais l’interaction n’a pas pu être confirmée par "GST-pulldown assay". Simultanément, une remise en question de la position de la méthionine initiale de C3VS, couplée à une impossibilité d’exprimer la protéine en cellules COS par transfection mettait en péril le travail. En l’absence de plus d’arguments fonctionnels permettant d’orienter l’étude des positifs, cette partie du travail a été suspendue au profit de notre étude sur le récepteur de la TSH. L'activation de cascades différentes dans le thyrocyte humain et canin pouvant être due à l'action de protéines intracellulaires, nous avons tenté de rechercher par double-hybride des partenaires protéiques autres que les protéines G pour le récepteur de la TSH. Nous avons ainsi identifié PRA1 mais nous n’avons pas pu confirmer l'interaction entre les deux protéines par "GST-pulldown assay". Pour tenter de comprendre le rôle de cette interaction, nous avons réalisé des essais fonctionnels en transfectant des cellules pour évaluer l'implication de PRA1 sur la synthèse d’AMPc. Ces expériences ne nous ont pas permis de montrer un rôle pour PRA1 au niveau de la cascade, mais en revanche, nous avons mis en évidence le fait que la co-transfection de deux ADNc codant pour des protéines membranaires sature la machinerie de traduction et diminue l'expression du RTSH. Dans une deuxième partie de notre travail, nous avons étudié la 5-phosphatase SHIP2, dont l’implication dans la cascade de réponse à l’insuline était suggérée, entre autres, par le travail d’Isabelle Vandenbroere qui avait montré l’interaction de cette protéine avec CAP et c-Cbl. Nous avons développé au laboratoire la culture de la lignée pré-adipocytaire 3T3-L1 et étudié la localisation de SHIP2 au niveau des rafts de ces cellules. Nous avons montré que SHIP2 n’y est pas recrutée. CAP et c-Cbl ne semblent pas non plus y être recrutées, tandis que nous y avons détecté le récepteur de l'insuline. La localisation de différentes protéines impliquées dans la cascade de l'insuline dans les rafts est une question controversée à l’heure actuelle et notre étude montre que l’implication fonctionnelle de SHIP2 dans la cascade de l'insuline n'est probablement pas dépendante des rafts.

No description available.

No description available.

Electrophoresis of solutes was studied in aqueous two-phase systems, concentrating on the special behavior in the interfacial region. Moving boundary electrophoresis was examined in a free fluid U-tube apparatus. Zone electrophoresis was investigated in two-phase systems which were gelled by the addition of acrylamide, which was subsequently polymerized. The size and nature (concentration or dilution) of polarizations which were found to occur was found to depend on the magnitude of the equilibrium partition coefficient of the solute in the two-phase system, as well as the direction of migration across the interface. These polarizations are in addition to those commonly known to occur near regions where electrophoretic flux changes radically, such as near interfaces. They can be a direct result of the requirement for equilibrium across the interface, as demonstrated by our experiments. Models were constructed to numerically simulate this behavior, which accounted for unsteady state electrophoresis and diffusion of multiple proteins or other amphoteric solutes. Two cases were explored, one requiring instantaneous solute equilibration across the interface, the other allowing for a resistance to mass transfer here. All models demonstrated a characteristic noted in experimental studies, concentration at interfaces when electrophoresis is from equilibrium preferred phase towards non-preferred phase. Furthermore, the equilibrium model correctly predicted the complex relationship between partition coefficient, direction of migration, and moving boundary or zone electrophoresis, which causes differences in the polarizations observed in these various systems. The simulation could also quantitatively estimate the width of the polarized region to within an order of magnitude, in comparison with experimental results, while hampered by a lack of mobility data for solutes in solutions containing polymers.

This dissertation performs a comprehensive analysis of the effect of different environmental, demographic and vehicle variables on the severity of two-vehicle crashes. The limitations associated with previous studies have been addressed by using a large crash database, properly defining the independent variables, using appropriate statistical models, and by considering the effect of factors normally unaccounted for such as crash type, impact speed, and weight or height incompatibilities between the two vehicles.The use of multinomial logit models at the individual occupant and crash levels provides the flexibility to evaluate variables that have opposing effects at different injury levels (such as airbags). Alternative formulations with interaction terms and with instrumental variables are included. An analysis of marginal probabilities and costs is also provided, which is particularly useful when discussing potential safety treatments with transportation officials, politicians and other decision makers.The findings from the different models are consistent and suggest that the type of crash has a great impact on severity. Age is the most significant demographic variable, with children and older occupants being least and most likely to be injured, respectively. Behavior also seems to be critical, as the use of seatbelts greatly decreases occupant injuries. Heavier vehicles increase the safety of its occupants but decrease the safety of occupants of the other vehicle. The effect of vehicle type is not as significant as weight, with the exception of pickups, which are both more crashworthy and more aggressive than passenger cars. Further research is needed on the effects of airbags and impaired driving, as the analyses conducted have been inconclusive.

No description available.

No description available.