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Thèse (M.Sc.)--Université Laval, 2007. / Bibliogr.: f. [97]-98. Publié aussi en version électronique dans la Collection Mémoires et thèses électroniques.

Thesis (M.S.) -- Middle East Technical University, 2004. / Keywords: Peer-to-peer (P2P), JXTA, web services, BPEL, WSDL, SOAP, J2ME, MIDP, CLDC, mobile applications.

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O texto descreve a definição e formalização da técnica de forcing, através de uma abordagem direta, sem a conversão para modelos transitivos. Também usa esta abordagem para provar um certo número de teoremas de consistência no âmbito da aritmética de cardinais e afins. / The text describes the definition and formalization of the forcing technique, via a direct approach, without the transition to ground models. It also uses this approach to prove a number of consistency theorems on cardinal arithmetic and related subjects.

The aim of this research is to investigate techniques or methodologies that will allow networked applications to adapt to network conditions between end nodes in order to maintain a reasonable Quality of Service and to design, develop and test techniques for achieving such adaptability through the use of a novel content scheduling and delivery scheme. In order to achieve this adaptation, information regarding network conditions, both static and dynamic, has to be first gathered. Since various parties have already conducted substantial research in this area, the task was to review those network measurement techniques and adopt a suitable one for use in the subsequent research. Hence the research is concerned more on how to realize these techniques in practical terms and make those network parameters accessible to applications that are going to adapt based on them. A network measurement service utilizing a standard measurement tool was proposed, developed, tested and subsequently used throughout the project. In this way the research project implementation has help in trying to understand the impact of network measurement on the overall performance of the system and what network metrics are essential in order to help the application make better adaptation decision. The project proceeded further to develop and show case an adaptable network application using a novel scheme in which content was restructured and its delivery rescheduled taking account of the available bandwidth, the content structure, size and order of importance and user specified deadlines, which made use of the network measurement service. In so doing, the project sought to show how and when adaptation can be applied and its potential benefits or otherwise as compared to conventional applications based on best effort systems. The project has proved that by adapting according to the abovementioned scheme in the event of poor network performance, user specified deadlines can be satisfied by reducing the load with contents of high importance being delivered first while contents of less importance being delivered during idle time or user's reading time or ignored if the deadline could not be met. In most cases content of high importance are delivered faster in the adaptable system as compared to the conventional best effort system.

M.Sc. (Geology) / The purpose of this investigation is to produce a' general survey of palygorskite deposits in South Africa with reference to their probable extent, mineralogical composition and the most important chemical and physical properties of the clay. Furthermore it is an attempt to provide a suitable beneficiation process so as to make beneficiated local palygorskite comparable with or superior to imported palygorskite. It is also an attempt to determine whether South African beneficiated palygorskite could replace imported material in e$tablished industrial applications. To these ends pa1ygorskites from seven geographical areas in South Africa were investigated. The characterization of the pa1ygorskites involved the following tests: Identification and semi-quantitative analysis of mineral phases in each sample by means of X-ray diffraction. Chemical analyses, differential thermal analyses, oil absorption measurements, surface area determinations, pH measurements, bulk density measurements and viscosity determinations. Electron microscopy of two end products of the beneficiation pro~ess was also carried out to determine the physical difference between magnetic and non-magnetic palygorskite.

Magister Scientiae - MSc / The nitrilases are an important class of industrial enzymes that are found in all phyla. These enzymes are expressed widely in prokaryotes and eukaryotes. Nitrilases convert nitriles to corresponding acids and ammonia. They are used in industry as biocatalysts because of their specificity and enantioselectivity. These enzymes belong to the nitrilase superfamily in which members share a common αββα structural fold and a unique cys, glu,lys catalytic triad with divergent N- and C-terminals.There are four atomic structures of distant homologues in the superfamily, namely 1ems, 1erz, 1f89 and 1j31. All structures have two-fold symmetry which conserves the αββα-αββα fold across the dimer interface known as the A surface. The construction of a 3D model based on the solved structures revealed the enzyme has two significant insertions in its sequence relative to the solved structures, which possibly correspond to the C surface. In addition there are intermolecular interactions in a region of a conserved helix, called the D surface. These surfaces contribute additional interactions responsible for spiral formation and are absent in the atomic resolution homologues.The recombinant enzyme from R.rhodochrous J1 was expressed in E. coli BL21 cells and eluted by gel filtration chromatography as an active 480 kDa oligomer and an inactive 80 kDa dimer in the absence of benzonitrile. This contradicts previous observations, which reported the native enzyme exists as an inactive dimer and elutes as a decamer in the presence benzonitrile. Reducing SDS-PAGE showed a subunit atomic mass of ~40 kDa. EM and image analysis revealed single particles of various shapes and sizes, including c-shaped particles, which could not form spirals due to steric hindrances in its C terminal.Chromatographic re-elution of an active fraction of 1-month old J1 nitrilase enabled us to identify an active form with a mass greater than 1.5 MDa. Reducing SDS-PAGE, N-terminal sequencing and mass spectroscopy showed the molecular weight was ~36.5 kDa as result of specific proteolysis in its C terminal. EM revealed the enzyme forms regular long fibres. Micrographs (109) were recorded on film using a JEOL 1200EXII operating at 120 kV at 50K magnification. Two independent 3D reconstructions were generated using the IHRSR algorithm executed in SPIDER. These converged to the same structure and the resolution using the FSC 0.5 criterion was 1.7 nm. The helix structure has a diameter of 13nm with ~5 dimers per turn in a pitch of 77.23 Å. Homology modeling and subsequent fitting into the EM map has revealed the helix is built primarily from dimers, which interact via the C and D surfaces. The residues, which potentially interact across the D surface, have been identified and these confer stability to the helix. The conservation of the insertions and the possibility of salt bridge formation on the D surface suggest that spiral formation is common among microbial nitrilases. Furthermore, the presence of the C terminal domain in J1 nitrilase creates a steric hindrance that prevents spiral formation. When this is lost – either by specific proteolysis or autolysis - an active helix is formed. / South Africa

Comprendre les performances d'une application multi-thread est difficile. Les threads interfèrent quand ils accèdent à la même ressource, ce qui ralentit leur exécution. Malheureusement, les outils de profiling existants se focalisent sur l'identification des causes de l'interférence, et non pas sur ses effets.Le développeur ne peut donc pas conclure si l'optimisation d'une interférence identifiée par un outil de profiling peut mener à une meilleure performance. Dans cette thèse, on propose de compléter les outils existants par un outil orienté-effet capable de quantifier l'impact de l'interférence sur la performance, indépendamment de la cause de l'interférence. Avec une évaluation de 27 applications, on montre que notre outil réussit à identifier 12 bottlenecks causés par 6 types d'interférence différents / Understanding the performance of a multi-threaded application is difficult. The threads interfere when they access the same resource, which slows their execution down. Unfortunately, current profiling tools focus on identifying the interference causes, not their effects.The developer can thus not know if optimizing the interference reported by a profiling tool can lead to better performance. In this thesis, we propose to complete the profiling toolbox with an effect-oriented profiling tool able to indicate how much interference impacts performance, regardless of the interference cause. With an evaluation of 27 applications, we show that our tool successfully identifies 12 performance bottlenecks caused by 6 different kinds of interference