Dans les Topiques, Aristote soutient que son traité, et par extension la dialectique, sert à la saisie des principes et des conclusions des différentes disciplines philosophiques. Mais cela surprend, puisque le raisonnement dialectique tire sa matière d'opinions admises, tient sa forme des lieux et dépend d'un répondeur et d'un demandeur, d'agents dialogiques. Or, l'opinion semble par nature trop déficiente pour mener à la vérité, le lieu, trop lâche pour respecter les règles du syllogisme valide et le dialogue tourne visiblement le plus souvent à la dispute. Cela a conduit de nombreux commentateurs à déconsidérer grandement le rôle de la dialectique chez Aristote : celle-ci, loin de constituer l'activité à laquelle se livrerait naturellement la raison aux prises avec un problème, s'assimilerait plutôt à un simple jeu, dont les règles auraient été déterminées arbitrairement. À l'encontre de ces différents commentateurs, ce mémoire entend montrer que, malgré leurs fragilités, la matière, la forme et les agents du raisonnement dialectique possèdent les puissances nécessaires pour préparer le travail du philosophe. Plus encore : la dialectique est le seul chemin pour progresser vers la philosophie. Qui rejette les opinions d'autrui, n'accepte que les démonstrations et refuse de dialoguer se condamne à errer d'idée en idée, incapable de trouver le point de départ de sa recherche et de résoudre les problèmes qui occupent son esprit. Celui qui vit en dehors de toute société, affirme Aristote dans les Politiques, n'est pas un homme, mais une bête. De même en va-t-il pour celui qui se prive de dialectique, car elle est en quelque sorte la cité de notre intelligence.

Lorsque le lymphocyte B entre en contact avec son antigène, plusieurs interactions sont essentielles. Parmi celles-ci, l'engagement de son récepteur CD40 avec le ligand CD154 d'un lymphocyte T activé est primordial. Des études réalisées in vitro ont démontré que l'intensité et la durée de l'interaction CD40-CD154 entraînent différentiellement l'évolution des lymphocytes B matures naïfs et à mémoire. En conséquence, une source de CD 154 soluble pour stimuler les lymphocytes B a été utilisée dans le but de vérifier comment la modulation de l'interaction modifiait les caractéristiques des populations de lymphocytes B par la transmission intracellulaire du signal, de CD40 au noyau. Les résultats obtenus lors de cette étude suggèrent que certaines voies de signalisation, principalement de la famille des MAPK soit, ERK.1/2 et p38, pourraient être empruntées différemment lors de la liaison de CD40 avec CD154. L'activation modulée des voies de signalisation pourrait participer à la régulation de la réponse immunitaire.

Montréal Trigonix inc. 2018

Le modèle de culture in vitro de l'équipe du Dr. Néron permet l'expansion à long terme des lymphocytes B à mémoire en présence d'une forte interaction entre CD40 et CD154 et d'un mélange d'IL-2, d'IL-4 et d'IL-10. Cette première phase dite d'expansion est suivie d'une phase de différenciation. Ce projet visait l'amélioration des conditions de différenciation, basée sur une faible interaction entre CD40 et CD154 et consistait en l'essai d'une vingtaine de combinaisons de facteurs solubles. Deux mélanges de cytokines soit, IL-6 et IL-10 ainsi que IL-2, IL-4 et IL-10 ont été identifiés et permettaient de diminuer la prolifération, d'augmenter la sécrétion d'IgG et de maintenir la viabilité. Le rendement de ces deux mélanges a été confirmé lors d'essais de transition progressive entre les deux phases. Nos travaux indiquent qu'il est possible d'induire la différenciation des lymphocytes B à mémoire suite à une longue période d'expansion dans le système CD40-CD154.

Security is a key aspect in information systems (IS) development. One cannot build a bank IS without security in mind. In medical IS, security is one of the most important features of the software. Access control is one of many security aspects of an IS. It defines permitted or forbidden execution of system's actions by an user. Between the conception of an access control policy and its effective deployment on an IS, several steps can introduce unacceptable errors. Using formal methods may be an answer to reduce errors during the modeling of access control policies. Using the process algebra EB[superscript 3], one can formally model IS. Its extension, EB[superscript 3]SEC, was created in order to model access control policies. The ASTD notation combines Harel's Statecharts and EB[superscript 3] operators into a graphical and formal notation that can be used in order to model IS. However, both methods lack tools allowing a designer to prove or verify security properties in order to validate an access control policy. Furthermore, the implementation of an access control policy must correspond to its abstract specification. This thesis defines translation rules from EB[superscript 3] to ASTD, from ASTD to Event-B and from ASTD to B. It also introduces a formal architecture expressed using the B notation in order to enforce a policy over an IS. This modeling of access control policies in B can be used in order to prove properties, thanks to the B prover, but also to verify properties using ProB, a model checker for B. Finally, a refinement strategy for the access control policy into an implementation is proposed. B refinements are proved, this ensures that the implementation corresponds to the initial model of the access control policy.

This thesis is concerned with the 19th century politico-religious and intellectual aspects of the Dyula of Bondoukou and the career of al-Ḥājj Ṣāliḥ b. Muḥammad b. Uthmān of Jinini (d. 1932). Among the points of discussion are the establishment of the Gyaman Abron kingdom in northern Ivory Coast, the founding of a Dyula imamate and trading community within its frontiers, the impact of the Samorian and French subjugation of the territory, the intellectual activity of the Dyula, and the influence of al-Ḥājj Ṣāliḥ in Bondoukou, Jinini and Wenchi. Selected Dyula Arabic writings are included to give the reader an idea of the level of Dyula familiarity with the language and Islamic learning; this is not intended to be an exhaustive study of Dyula scholarship. To the degree which the sources permit, the focus of this study is upon the life of a little known scholar in the West, al-Ḥājj Ṣāliḥ.

Thesis (MScEng (Process Engineering))--University of Stellenbosch, 2005. / The development of non-replicating vaccines is an emerging option for safe, effective vaccines, several of which contain virus-like particles (VLPs). Many recombinant expression systems have been evaluated as hosts for VLP production for the prevention of infectious diseases. The filamentous fungi Aspergillus niger has emerged as a potential alternative expression system for cost effective VLP vaccine production. Hepatitis B surface antigen (HBsAg) was used as a model VLP product to benchmark A. niger’s production capacity with those of Saccharomyces cerevisiae, Pichia pastoris and Hansenula polymorpha. Bioprocessing strategies were used to optimise VLP production by recombinant A. niger in batch culture. In particular, the effect of the parameters culture temperature, inoculum concentration, agitation intensity, dissolved oxygen (dO2) concentration and culture pH on biomass formation, morphology and VLP (HBsAg) production concentration was quantified. At an optimum agitation of 100 rpm and optimum dO2 concentration of 50 %, HBsAg production levels were increased 9-fold compared to yields obtained in shakeflask cultivation. Highest HBsAg production levels of 3.6 mg.ℓculture -1 and 350 μg.gDW -1 were recorded, at a biomass concentration of 10.5 gDW.ℓculture -1. These production levels compare favourable with those obtained by other production systems under similar conditions. HBsAg VLPs mostly accumulated intracellularly, although under optimum bioreactor conditions significant HBsAg accumulation in the cytoplasm and culture supernatant was also observed. The impact of these process parameters on VLP production and cell morphology was attributed to environmental stress conditions. Volumetric biomass and HBsAg production levels were maximised under conditions of lowest environmental stress, resulting in the most optimal small-pelleted morphology. These results indicate a substantial potential for further engineering of the A. niger production system for the high level of intracellular and extracellular VLP production.

Nanotubes (inner diameter of 8nm and outer diameter of 10nm with a length of up to several hundred nm) and nanowires (diameter 20 – 50nm and up to several μm in length) of TiO₂-B have been synthesised and characterised for the first time. These exhibit excellent properties as a host for lithium intercalation and are able to accommodate lithium up to a composition of Li₀.₉₈TiO₂-B for the nanotubes and Li₀.₈₉TiO₂-B for the nanowires. Following some irreversible capacity on the first cycle, which could be reduced to 4% for the nanowires, capacity retention for the nanowires is 99.9% and for the nanotubes is 99.5% per cycle. In both cases, the cycling occurs at ~1.6V versus lithium. The cycling performance was compared with other forms of bulk and nano-TiO₂, all of which were able to intercalate less lithium. Nanowires of VO₂-B (50 – 100nm in diameter and up to several μm in length) were synthesised by a hydrothermal reaction and characterised. By reducing the pressure inside the hydrothermal bomb, narrower VO₂-B nanowires with a diameter of 2 – 5nm and length of up to several hundred nm were created - some of the narrowest nanowires ever made by a hydrothermal reaction. These materials are isostructural with TiO₂-B and were also found to perform well in rechargeable lithium ion batteries, being able to intercalate 0.84Li for the ultra-thin nanowires and 0.57Li for the standard nanowires. The standard VO₂-B nanowires have a capacity retention of 99.8% and the ultra-thin nanowires have 98.4% per cycle after some irreversible capacity on the first cycle. This was found to improve markedly when different electrolytes were used. Macroporous Co₃O₄ (pore size 400nm with a surface area of 208m²/g) was prepared and cycled in rechargeable lithium cells with capacities of 1500mAh/g being achieved. The structure was found to break down on the first cycle and after this the material behaved in the manner of Co₃O₄ nanoparticles. Finally a new candidate for next generation rechargeable lithium batteries was examined; Li/O₂ cells. The cathode is composed of porous carbon in which Li⁺, e⁻ and O₂ meet to form Li₂O₂ on discharge. The reaction is reversible on charge. Capacities of 2800mAh/g can be achieved when 5%mole of αMnO₂ nanowires catalyst is used. Fade is high at 3.4% per cycle meaning that there is much work to do to develop these into a commercial prospect.

published_or_final_version / Pathology / Doctoral / Doctor of Philosophy

published_or_final_version / Dentistry / Master / Master of Dental Surgery