Dans les trois domaines du vivant, que constituent les bactéries, les eucaryotes et les archées, une molécule a la capacité souveraine de gouverner la vie, la mère à l’origine de tous les mécanismes biologiques, l’ADN. S’il est évident de dire que le maintien de l’intégrité des génomes est essentiel à la vie, il existe deux systèmes qui le permettent, la réplication et la réparation de l’ADN. La fidélité de ces derniers est finement influencée par la disponibilité (ratio et balance) des précurseurs nucléotidiques désoxyribonucléotides (dNTPs) et ribonucléotides (rNTPs) au cours du cycle cellulaire. Même si la concentration intracellulaire en nucléotides est largement documentée chez les eucaryotes et les bactéries, ça n’est malheureusement pas le cas chez les archées. En ce qui concerne l’étude de la maintenance génomique, un groupe d’archées a intéressé les chercheurs de par leurs capacités à survivre dans des milieux dits extrêmes. Pyrococcus abyssi est l’une d’entre elles qui depuis de nombreuses années sert de modèle biologique pour répondre aux questions de la stabilité de l’ADN à haute température. Cette étude est centrée sur cette thématique et particulièrement sur les caractéristiques fonctionnelles des ADN polymérases: PolD, PolB et le complexe p41/p46. Initialement, le contenu en nucléotides a été évalué dans des cellules en phase exponentielle de croissance par la technique de chromatographie couplée à une double détection en spectrométrie de masse (zicHILIC-MS-MS). Les résultats montrent que le contenu en rNTPs est de 20 fois supérieur à celui en dNTPs. Pour cette raison, la discrimination sélective des dNTPs par les ADN polymérases est mise à l’épreuve. Même si, des mécanismes permettent d’exclure les rNMPs durant la synthèse de l’ADN, de récentes études ont montrées que des rNMPs étaient incorporés par des ADN pols. Ainsi, le ratio en nucléotides obtenu a été utilisé pour l’analyse de son effet sur la synthèse d’ADN par les ADN Pols et les extraits cellulaires de P. abyssi. Les résultats démontrent clairement que les rNMPs sont incorporés par l’ADN polymérase PolD. Puis, les conséquences de la présence des rNMPs dans l’ADN sur la réplication ont été étudiées et ont mis en évidence que les extraits cellulaires, tout comme les ADN Pols de P. abyssi étaient capables de « passer » un rNMP présent dans l’ADN. Pour finir, une étude de l’incorporation préférentielle de chaque dNMP et rNMP a été menée démontrant que la complémentarité des bases était respectée même lors de l’incorporation de rNMPs. Enfin, la caractérisation de la petite sous-unité, DP1, de PolD a permis de montrer sa capacité à retirer des rNMPs grâce à son activité de relecture, suggérant un premier rempart à la présence de rNMPs dans l’ADN. Pour conclure, ces résultats montrent que la présence de rNMPs dans l’ADN est un phénomène conservé dans les trois domaines du vivant. / In the three domains of life that include Bacteria, Eukarya and Archaea, one molecule has the sovereign ability to govern life, and not the least one, the mother of all biological mechanisms, DNA. Maintaining the integrity of genomes is obviously essential for life, and faithful DNA replication and repair are the guarantees. The fidelity of these two processes may vary depending on the availability and levels (balance and ratio) of deoxyribonucleotides (dNTPs) and ribonucleotides (rNTPs) during the cell-cycle. Even if intracellular concentration of nucleotides is largely documented in Eukarya and Bacteria, it remains limited in Archaea. From many years one group of Archaea is of great interest for studying genomic maintenance, because of its ability to survive in extremes environments. Pyrococcus abyssi is one of them that is used as biological model for deciphering the stability of DNA at elevated temperature in LM2E. The present work focuses on genomic integrity and particularly on the functional characterization of the three DNA polymerases: PolD, PolB and the p41/p46 complex. Initially, the nucleotide pool has been evaluated in exponentially growing cells using the highly sensitive method that combined chromatography and mass spectrometry (zicHILIC-MS-MS). The results show that rNTPs content is 20-fold higher than dNTPs. For that reason, fidelities of DNA polymerases are challenged to select the correct dNTP over the most abundant rNTP during DNA synthesis. Despite the fact that some mechanisms allow the exclusion of rNTPs from entry to the Pol active site, recent findings indicate that ribonucleotides are incorporated by different DNA Pols with surprisingly high frequency. In this work, the obtained intracellular balance and ratio of rNTPs and dNTP have been used to analyze their effect on DNA synthesis by P. abyssi DNA Pols and cell-free extracts. Our results clearly demonstrate that rNTP incorporation is detectable with distinct efficiencies among DNA pols. Secondly, the consequences of the presence of rNMPs in a DNA template on DNA polymerisation has been examined and highlights that cell-free extracts are able to bypass a single rNMP as well as replicative DNA polymerases. To strengthen that study, single nucleotide incorporation opposite rNMP or dNMP has been carried out and the results demonstrate that replicative Pyrococcus abyssi DNA Pols can basepair the complementary rNTPs opposite dNMPs, and vice-versa, the complementary dNTPs opposite rNMPs.Furthermore, the preliminary results obtained about the nucleolysis activities of the PolD small subunit, DP1, show that the DNA polymerase D is able to remove rNMPs from a DNA strand, suggesting a first level of protection against ribonucleotide contamination of DNA. Definitely, these data indicate that the presence of transient embedded rNMPs in genomic DNA represents a universally conserved phenomenon across Archaea, Bacteria and Eukarya.

No description available.

L'éthanol est converti, à 350°C sous 30 bar et sur des zéolithes protoniques, en un mélange de paraffines légères et d'aromatiques ; produits incorporables dans le pool essence. Cependant, la transformation de EtOH sur zéolithes acides conduit à la formation du coke. Des techniques physiques avancées, en particulier les techniques MALDI et LDI-TOF MS, couplées à la méthode d'analyse qui consiste à récupérer dans un solvant les molécules carbonées après dissolution de la zéolithe dans HF, contribuent à caractériser finement le coke. Sa composition dépend du catalyseur : sur HBEA(11), zéolithe à larges pores, 17 familles ont été détectées contre 4 sur HZSM-5(40) de taille de pore intermédiaire. Sur cette dernière, le coke, composé de polyalkybenzènes / naphtalènes / phénalènes et pyrènes, est localisé à l'intersection des canaux et a une toxicité vis-à-vis des sites acides de Brønsted de 1. En dépit d'un empoisonnement total, cette zéolithe est toujours capable de convertir EtOH, comme MeOH, en hydrocarbures et qui plus est avec les mêmes sélectivités en produits. La transformation de ces deux alcools ne s'explique pas par un mécanisme classique de catalyse acide, mais par un mécanisme concerté radicalaire-acide. La présence d'un inhibiteur de radicaux dans la charge réactionnelle, l'hydroquinone, provoque une désactivation immédiate et une diminution de la concentration des radicaux. La transformation de EtOH et MeOH passe par un intermédiaire réactionnel commun, le carbène :CH2, dont l'oligomérisation radicalaire conduit à la formation d'oléfines. Ces oléfines légères (n-O3-n-O5) sont très réactives et se transforment par catalyse acide (oligomérisation / cyclisation / t / Ethanol is converted into light paraffins and aromatics mixture at 350°C under 30 bar over protonic zeolites. These products can be incorporated in the gasoline pool. Nevertheless, EtOH transformation over acid zeolites leads to the formation of the coke. Advanced physical techniques, in particular MALDI and LDI-TOF MS, were coupled to the coke analysis method. This method consists of the recovery of the carbonaceous molecules in a solvent after zeolite dissolution in hydrofluoric acid solution. This coupling allows characterizing the coke through an extensive way. The coke composition depends on the catalyst morphology: over HBEA(11) zeolite of large pores, 17 families were detected while 4 over HZSM-5(40) of intermediate pore size. Over this latter, the coke, composed of polyalkylbenzenes/naphtalenes/phenalenes and pyrenes, is located in the channels intersections and has toxicity of 1 towards Brønsted acid sites. In spite of a total poisoning, HZSM-5 zeolite is always able to convert EtOH, like MeOH, into hydrocarbons with the same products selectivity. The transformation of the two alcohols cannot be explained by a classical mechanism of acid catalysis, but by a cooperative radical-acid mechanism. The presence of a radical inhibitor in the feed, the hydroquinone, causes an immediate deactivation and a decrease in the concentration of radicals. The transformation of EtOH and MeOH passed by the common reaction intermediate, the :CH2 carbene, which its radical oligomerization leads to the formation of olefins. Olefins (n-O3-n-O5) are very active and can be transformed through acid catalysis (oligomerization/cyclisation/Hydrogen transfer) into aromatics or undergo isomer

No description available.

Subject: Optimal Parameters for Barrier-free Indoor Swimming Pools Focusing on the Needs of People with Limited Motion and Orientation Abilities. Objectives of the thesis: The aim of the thesis is to evaluate the optimal parameters of barier - free indoor swimming pools taking into account the requirements of persons with reduced mobility and orientation; based on the needs of these persons and the current legal standards to list the parameters for the construction and evaluation of swimming facilities in the Czech Republic. Furthermore, to find out views on this topic in the students of the faculties of building. Methods: A questionnaire survey of selected population will be carried out. Furthermore, the methods of a semistandardized interview will be used and a field research in the monitored objects will be implemented. Results: The results will confirm or disprove the predetermined hypotheses and will contribute to understanding the issues. A basis for creating an optimal barrier-free project will be made. Keywords: barrier-free environment, swimming pool, visual impairment, physical handicap 3

Magister Philosophiae - MPhil / Increasing energy needs globally have recently led to an interest in effectively bringing energy services in the trading system. Energy services were part of the Uruguay Round of negotiations, whose main achievement was the General Agreement on Trade in Services (GATS). The objective of the GATS is to achieve progressive liberalisation and reduction or elimination of trade barriers of all services sectors, including energy services. The GATS has made commendable progress in liberalising many service sectors, however it has not made meaningful progress with energy services. Furthermore though the SADC region engages in energy services trade through bilateral and regional agreements, a variety of barriers inhibit major successes from being achieved. Effective energy services trade and liberalisation has therefore proved problematic both at the multilateral, regional and bilateral level. This study, seeks to investigate why energy services liberalisation and trade at the multilateral, regional and bilateral level is problematic, with a particular focus on the SADC region. / South Africa

Magister Philosophiae - MPhil / Increasing energy needs globally have recently led to an interest in effectively bringing energy services in the trading system. Energy services were part of the Uruguay Round of negotiations, whose main achievement was the General Agreement on Trade in Services(GATS). The objective of the GATS is to achieve progressive liberalisation and reduction or elimination of trade barriers of all services sectors, including energy services. The GATS has made commendable progress in liberalising many service sectors, however it has not made meaningful progress with energy services. Furthermore though the SADC region engages in energy services trade through bilateral and regional agreements, a variety of barriers inhibit major successes from being achieved. Effective energy services trade and liberalisation has therefore proved problematic both at the multilateral, regional and bilateral level. This study,seeks to investigate why energy services liberalisation and trade at the multilateral, regional and bilateral level is problematic, with a particular focus on the SADC region.

The thesis focuses on a mixed integer linear programming (MILP) formulation for a bi-level mathematical program with equilibrium constraints (MPEC) considering chance constraints. The particular MPEC problem relates to a power producer’s bidding strategy: maximize its total benefit through determining bidding price and bidding power output while considering an electricity pool’s operation and guessing the rival producer’s bidding price. The entire decision-making process can be described by a bi-level optimization problem. The contribution of our thesis is the MILP formulation of this problem considering the use of chance constrained mathematical program for handling the uncertainties. First, the lower-level poor operation problem is replaced by Karush-Kuhn-Tucker (KKT) optimality condition, which is further converted to an MILP formulation except a bilinear item in the objective function. Secondly, duality theory is implemented to replace the bilinear item by linear items. Finally, two types of chance constraints are examined and modeled in MILP formulation. With the MILP formulation, the entire MPEC problem considering randomness in price guessing can be solved using off-shelf MIP solvers, e.g., Gurobi. A few examples and a case study are given to illustrate the formulation and show the case study results.

Afin de proposer un outil permettant d'étudier les phénomènes hydrodynamiques dans le bain de fusion et le capillaire de vapeur lors du soudage laser, un modèle thermohydraulique prenant en compte les trois phases en présence (vapeur métallique, bain liquide et solide) a été développé à l'aide du code de calcul Comsol Multiphysics. Pour suivre l'évolution de ces trois phases, les équations couplées de la chaleur et de Navier-Stokes sont résolues et le suivi de l'interface liquide-vapeur est traité à l'aide de la méthode level set. Les réflexions multiples du laser sont calculées avec une nouvelle méthode consistant à décrire le laser sous sa forme ondulatoire. Le modèle est d’abord appliqué à un cas de tir laser statique, cas pouvant être résolu en 2D axisymétrique permettant de réaliser les développements et une première validation. L'influence de certains paramètres, comme la puissance laser est étudiée et les mécanismes conduisant à l'apparition de porosité résiduelle sont mis en évidence. Ensuite, ces mêmes équations sont utilisées en 3D pour décrire de la façon la plus complète possible une ligne de fusion. Toute la phase de création du capillaire est analysée puis les températures et les vitesses calculées sont comparées à des mesures expérimentales. Les températures en phase solide sont obtenues grâce à des thermocouples de 25µm, les températures en surface du bain liquide par pyrométrie et enfin, les vitesses à la surface du bain son obtenues grâce à une caméra rapide. Ces comparaisons permettent de montrer la cohérence du modèle, son comportement physique à décrire les écoulements, les formes de zones fondues et la dynamique du capillaire de vapeur. / To provide a tool able to study hydrodynamics phenomena in the melt pool and the vapor capillary during laser welding of tailored blanks, a heat and fluid flow model taking into account the three phases present is proposed. The metal vapor, the liquid phase and the solid base are modeled using the code Comsol Multiphysics. In order to study the evolution of these three phases, coupled equations of heat transfer and Navier-Stokes equations are solved and the liquid-vapor interface is tracked using the level set method. Multiple reflections of the laser are calculated with a new method by describing the laser in its wave form by solving Maxwell's equations. This manuscript presents the results of the model, first, in a case of a static laser shot solved in axisymmetric 2D to achieve the development and initial validation. The influence of parameters such as laser power is studied and the mechanisms leading to the appearance of residual porosities is highlighted. Then, these equations are used in three dimensions to describe the most complete as possible, a fusion line with an opened vapor capillary. All the creation phase of the capillary is analyzed. Calculated temperatures and velocities are compared to experimental measurements. Temperatures in the solid phase are obtained with thermocouples of 25µm, the surface temperature of the melt pool are obtained by pyrometry and finally velocities at the surface of the melt pool are obtained with a high speed camera. These comparisons show the consistency of the model to describe the physical flows, the molten zones shapes and the complete behavior of the vapor capillary.

The occurrence of organic contaminants in the drinking water value chain (from source to tap) is a growing concern for the Drinking Water industry and its consumers given the high risk these contaminants can cause to the general public. These adverse health effects include such as endocrine disruption, toxicity teratogenicity, mutagenicity and carcinogenicity. Some of these organic contaminants are included in national and international drinking water quality guidelines or standards. However, although there are similarities in the list of organic contaminants used by each organization or country, the organic contaminants are never the same given the local conditions. There are also noticeable differences in the concentration limits set as targets or criteria for organic contaminants for public health protection via the use of drinking water. A further question requiring the response from drinking water regulators was whether the standards listed in the international literature would be applicable in other countries like South Africa. Complicating this decision is the fact that the South African National Drinking Water Standard (SANS 241) does not adequately address this component of drinking water quality management. The current standard only provides for dissolved organic carbon (DOC), total trihalomethanes (TTHMs) and phenols. However, the standard contains a statement which specifies that if there is a known organic contaminant, that may pose a health threat, it should be included in the monitoring programme and evaluated against World Health Organization (WHO) guidelines. To safeguard Drinking Water industry customers, it was deemed necessary to investigate this matter and establish a tool to assist with the identification of a list of organic contaminants to be monitored in the drinking water value chain. To achieve this a specific procedure/protocol needed to be developed, hence the aim of this study which was to develop a generic protocol for the selection and prioritization of organic contaminants for monitoring in the drinking water value chain (from source to tap). To achieve this, a critical evaluation and synthesis of the available literature on the approaches for the selection and prioritization of organic variables of priority to the drinking water industry was undertaken as a first step. From the literature review it was evident that there are currently many selection and prioritization approaches which are characterized mainly by the purpose for which the exercise has been conducted for. Approaches that prioritize chemicals according to their importance as environmental contaminants have been developed by government agencies and private industries such as the Health Canada’s Canadian Environmental Protection Agency (CEPA), the United Kingdom’s Institute for Environmental Health (IEH), the European Community’s Oslo and Paris (OSPAR) convention exercise for the protection of the Northeast Atlantic marine environment and the European Union (EU)’s combined monitoring based and modelling based priority setting scheme (EU-COMMPs). A few approaches such as ones published by the United States Environmental Protection Agency (USEPA), address the needs of the Drinking Water industry and there is no generic approach to the selection, prioritization and monitoring of organic contaminants in the drinking water value chain. From the review of selection and prioritization approaches, a generic model was developed. The model consists of three main steps, the compilation of a “pool of organic contaminants, the selection of relevant parameters and criteria to screen organic contaminants and finally the application of criteria to select priority organic contaminants. It was however realized that these steps were not enough if the protocol to be develop will serve its purpose. Selection and prioritization approaches are typically intended to be fairly simple and quick methods for determining the health and environmental hazards posed by the use and release of chemical substances into different environmental systems. This was taken into account during the development of the current protocol. Understanding that a protocol is a predefined written procedural method in the design and implementation of tasks and that these protocols are written whenever it is desirable to standardize a method or procedure to ensure successful reproducibility in a similar set up, a generic protocol was developed based on the model. The protocol developed in this study, operates as a multidisciplinary contaminants management and proactive protocol, thus exchanges toxicological, water quality, agricultural, chemical and public health information. The protocol uses previous or readily available information as a point of departure. It seeks to address the challenge facing the water industry in managing the current and emerging organic contaminants that are relevant to public health protection via the use of drinking water. Once the protocol was developed, it was validated in a prototype drinking water value chain. The exercise comprised of testing each step of the protocol from the selection of the “pool of organic contaminants (Step I) to recommending the final priority list of organic contaminants (Step VII). The implementation was successfully conducted in the Rand Water drinking water value chain. Emphasis of expert judgment was made as each step was validated and the opinion of key stakeholders used to shape the process. During Step III of the protocol, an intensive literature review was conducted to determine organic contaminants that have been identified in ground and surface water systems across the world. As a result of this review, major groups of organic contaminants that have been found to occur in source water resources across the world were identified. The identified groups of organic contaminants include, pesticides, polynuclear aromatic hydrocarbons, per and polyfluoroorganic compounds, polycyclic aromatic hydrocarbons, alkanes and alkenes, C10-C13 Chloroalkanes, pharmaceuticals and personal care products [PPCPs], surfactants, benzotriazoles, cyanotoxins and Carbon-based engineered nanoparticles. The risk profile of the identified organic contaminants was established using the persistence, bio-accumulation and toxicity criteria and the development of water quality monographs as an information dissemination tool. A conceptual framework for the implementation of the protocol by water utilities and relevant institutions has been developed from the experiences learnt during the validation exercise and a priority list of organic contaminants for the monitoring in the drinking water value chain to be used by Rand Water and other water utilities was identified. Some of the organic contaminants on this are currently being analyzed for in The Rand Water’s routine organic monitoring programme. During the validation exercise, the following were noted, <ul> <li>During the identification of the “pool of organic contaminants” from the consulted information sources such as the WHO guidelines for drinking water quality, Health Canada drinking water quality guidelines, the USEPA drinking water quality standards, the New Zealand drinking water quality standards, USEPA IRIS database, the PAN-UK list of registered pesticides for South Africa, the IARC list for recognized carcinogens and the Department of Agriculture pesticides manuals duplications were observed. </li> <li>The time allocated could not allow for the development of water quality monographs for all organic contaminants of concern but for a few selected contaminants whose information was inadequate to allow for decision-making. </li> <li>The determination of concentration levels of organic contaminants in fish, sediment and water samples could have been limited by the failure of current analytical instruments to go down to lower levels at which they occur in the drinking water value chain. <l/i> <li>Only two events could be planned, during the wet season (high flow) and dry season (low flow) based on time and budget constraints. </li> <li>Although various experts were consulted and invited to attend workshops in order to validate the process, the attendance could not be extended to all nine provinces given the time and budget constraints. <br></li></ul> Based on the above, recommendations were made for the dissemination and use of the products emanating from this study. For example, it is recommended that the current protocol be made available to water utilities and the process of revising the current priority list be repeated every 5 years. Further research should be conducted to obtain full coverage of organic contaminants impacting on source water quality in all ground water and surface water systems used as sources for drinking water production. Another major recommendation is the investigation of potential analytical methods that current chromatographic methods with high resolution mass spectrometry to ensure that organic contaminants can be detected at the ng/l to pg/l using a single enrichment method in order to make sure that those organic contaminants that occur at very low concentration in environmental samples can be detected. For example, the realisation that compounds such as synthetic organic polymer residues, emerging disinfectant by-products, detergent metabolites, chlorinated benzenes, alkyl phenol, polyethoxylates, their metabolites and cyanotoxins are continuously discharged into the environment via wastewater and industrial effluent discharges which increases their concentration in aquatic environment and concomitantly their potential to exert adverse health effects in water used as source for the production of drinking water necessitates that each of these groups be added to the current monitoring programme. The current water quality monographs can be used for the benefit of the Drinking Water industry. It is also recommended that a training manual on the production and use of water quality monographs is produced to facilitate their dissemination. CD-ROMs on the water quality monographs can be produced and distributed with the manual. / Thesis (PhD)--University of Pretoria, 2010. / School of Health Systems and Public Health (SHSPH) / PhD / Unrestricted