Le fonctionnement écologique des écosystèmes côtiers est soumis à l’action synergique des changements climatiques et des pressions anthropiques. Au sein du Bassin d’Arcachon, l’huître Crassostrea gigas, montre depuis quelques années une modification du cycle reproductif (i.e. faible formation des gamètes, retard de ponte), qui semble lié aux modifications globales des conditions thermiques et trophiques du milieu. L’objectif de ce travail consiste à réaliser un état des lieux de la variabilité spatio-temporelle de l’état reproductif des huîtres dans le Bassin d’Arcachon, en lien avec l’origine, la quantité et la qualité de la ressource trophique. Les résultats obtenus ont permis de révéler d’importants gradients spatiaux de variabilité du développement gonadique et du signal trophique chez C. gigas, entre les parties internes sous influences des rivières (sud-est et nord-est), et la partie externe sous influences océaniques. Deux facteurs clés se sont révélés en partie explicatifs de cette variabilité, le temps d’immersion et le temps de renouvellement océanique. Un comparatif de la gamétogenèse et du pool nutritif entre les parties sud-est et nord-est du bassin a permis de démontrer une variabilité temporelle de la composition phytoplanctonique associée à une variabilité des apports en acides gras essentiels à la formation et la maturité des gamètes. La dynamique de la mise en réserves ainsi que le déclenchement des pontes chez C. gigas se sont révélés synchrones à la variabilité saisonnière de la quantité et la qualité du pool nutritif. Ces résultats représentent une première étape vers le développement d’un modèle prédictif des besoins énergétiques de l’espèce sous l’effet des changements globaux des conditions environnementales. / The ecological functioning of coastal ecosystems is subjected to the synergistic action of climate change and anthropogenic pressures. In Arcachon Bay, the reproductive cycle of the oyster Crassostrea gigas has changed in recent years (e.g. weak gametogenesis, spawning delay). This pattern seems to be associated with global changes in thermal and trophic conditions. The aim of this work was to characterize the spatio-temporal variability in the reproductive investment of oysters in Arcachon Bay. This variability has been investigated in relation to the origin, quantity and quality of the trophic resources. The results revealed important spatial gradients of variability in gonadal development and trophic signal in C. gigas, between inner parts of the bay influenced by river inputs (south-east and north-east) and the external part of the bay, which is influenced by oceanic inputs. Two hydrodynamic factors explained most of the observed variability: immersion time and oceanic water renewal. A comparison of C. gigas gametogenesis and the nutritional value of available food sources between the south-eastern and north-eastern parts of the bay revealed temporal variability in the composition of phytoplankton. This variability was associated with variability in the amounts of essential fatty acids, necessary for gametogenesis. Changes in energy reserves and gamete release cycle were synchronized with the seasonal nutrient variability. These results constitute a first approach in the development of a model predicting the evolution of the energetic needs of C. gigas under the global change in environmental conditions.

La désinfection de l’eau de piscine est essentielle pour prévenir la propagation de maladies infectieuses. Cependant, les désinfectants réagissent avec les composés organiques présents dans l’eau y compris ceux introduits par les baigneurs, tels que les fluides corporels et les crèmes solaires, conduisant à la formation de sous-produits de désinfection (SPD) associés à des effets néfastes sur la santé. Le devenir des filtres UV organiques, présents dans les crèmes solaires et les produits de soins personnels, dans les piscines d'eau de mer chlorées est peu connu. Les objectifs de la présente étude étaient d'étudier la réactivité des filtres UV organiques dans l'eau de mer chlorée, d’identifier les SPD générées par les filtres UV, d'analyser l’occurrence des SPD dans les piscines d'eau de mer, et d'examiner leur génotoxicité. Des expériences de chloration ont été menées dans l'eau de mer reconstituée sur cinq filtres UV couramment utilisés : l’oxybenzone (OXY), le dioxybenzone (DIOXY), l’avobenzone (AVO), l’octyl méthoxycinnamate (OMC), et l’octocrylène (OC). Tous les composés étudiés sauf l’OC ont été dégradés conduisant à la formation de SPD bromés pour lesquels des schémas réactionnels ont été proposés. L'occurrence de ces SPD a été étudiée dans les piscines d'eau de mer où des SPD bromés ont été quantifiés. La génotoxicité de l’hydrate de bromal (BH), l’un des SPD généré par OXY et DIOXY et détecté dans les piscines d'eau de mer, a été évaluée. BH a induit une activité génotoxique dans le test d'Ames et l'essai de comète. Cette étude montre que les filtres UV peuvent agir comme précurseurs pour la formation de SPD génotoxiques dans l’eau de mer chlorée. / Disinfection of swimming pool water is critical to prevent outbreaks of infectious diseases. However, disinfectants react with organic compounds present in water, including anthropogenic inputs (e.g. body fluids, sunscreens), leading to the formation of disinfection byproducts (DBPs) that have been linked to adverse health effects. Little is known about the fate of organic UV filters, present in sunscreens and personal care products, when introduced into chlorinated seawater swimming pools. The aims of the present study were to investigate the reactivity of five commonly used organic UV filters in chlorinated seawater, identify DBPs generated from the UV filters, analyze the occurrence of these DBPs in seawater swimming pools, and examine their genotoxicity. Chlorination experiments were conducted to analyze the reactivity of the UV filters oxybenzone (OXY), dioxybenzone (DIOXY), avobenzone (AVO), octyl methoxycinnamate (OMC), and octocrylene (OC) in reconstituted seawater. All the studied UV filters except OC were degraded in chlorinated seawater resulting in the formation of brominated DBPs. Based on the identified byproducts, transformation pathways were proposed. The occurrence of the identified DBPs was investigated in seawater pools. Several brominated DBPs were identified in seawater pool samples. The genotoxicity of bromal hydrate (BH), which was generated by the benzophenone UV filters OXY and DIOXY and detected in the investigated seawater pools, was assessed. BH induced genotoxic activity in the Ames test and in the comet assay. Overall, this study shows that UV filters can act as precursors for the formation of genotoxic DBPs in chlorinated seawater pools.

Life history traits affect the timing and pattern of maturation, reproduction, and survival during an organism’s lifecycle and are the major components influencing Darwinian fitness. Co-evolved patterns of these traits are known as life history strategies (LHS) and variation occurs between individuals, populations, and species. The polymorphisms underlying LHS are important targets of natural selection, yet the underlying genes and physiological mechanisms remain largely unknown. Mapping the genetic basis of a LHS and subsequently unraveling the associated physiological mechanisms is a challenging task, as complex phenotypes are often polygenic. However, in several systems discrete LHS are maintained within the population and are inherited as a single locus with pleiotropic effects. These systems provide a promising starting point for investigation into LHS mechanisms and this thesis focuses on one such strategy - the Alba polymorphism in Colias butterflies. Alba is inherited as a single autosomal locus, expressed only in females, and simultaneously affects development rate, reproductive potential, and wing color. Alba females are white, while the alternative morph is yellow/orange. About 28 of 90 species exhibit polymorphic females, though whether the Alba mechanism and associated tradeoffs are conserved across the genus remains to be determined. In this thesis I primarily focus on the species Colias croceus and integrate results from lipidomics, transcriptomics, microscopy, and genomics to gain insights to the proximate mechanisms underlying Alba and Alba’s evolution within the genus. Lipidomics confirm that, consistent with findings in New World species, C. croceus Alba females have larger abdominal lipid stores than orange, an advantage which is temperature dependent and arises primarily due to mobilized lipids. Gene expression data suggests differences in resource allocation, with Alba females investing in reproduction rather than wing color, consistent with previous findings in other Colias species. Additionally, I identify a morphological basis for Alba’s white wing color. Alba females from C. croceus, an Old World species, and Colias eurytheme, a New World species both exhibit a significant reduction in pigment granules, the structures within the wing scale that contain pigment. This is a trait that seems to be unique to Colias as other white Pierid butterflies have an abundance of pigment granules, similar to orange females. I also map the genetic basis of Alba to a single genomic region containing an Alba specific, Jockey-like transposable element insertion. Interestingly this transposable element​ is located downstream of BarH-1, a gene known to affect pigment granule formation in Drosophila. Finally, I construct a phylogeny using a global distribution of 20 Colias species to facilitate investigations of Alba’s evolution within the genus. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 3: Manuscript. Paper 4: Manuscript.</p>

Ces travaux présentent une recherche sur la physique du soudage hybride. La revue littéraire décrit les principaux processus physiques se produisant au cours de la combinaison Laser-arc, les principales réalisations et les problèmes rencontrés lors de l'analyse de ces processus. Les processus ont été étudiés pendant l'assemblage de matériaux de fortes épaisseurs. Deux configurations ont été utilisées. La première est le soudage d’un acier Superduplex en un seul passage, par Laser et arc distanciés. La seconde configuration est le soudage multipasse de l'acier 18MND5, où le faisceau Laser défocalisé intercepte le plasma d'arc électrique. Avec l'aide de la planification d'expérience, l'imagerie vidéo rapide, l'enregistrement des signaux électriques, la détermination de la température et des distorsions de l’assemblage ont permis d’expliquer le rôle de chaque source thermique et l'influence de leur combinaison sur la création du bain fondu, l'identification du mode de transfert métallique et la répartition de la chaleur dans la plaque soudée. Les relations entre les signaux électriques et la géométrie de l'arc, les dimensions du bain et la distribution de chaleur sont analysées à différentes échelles de temps. L'analyse thermique présentée montre que l'hypothèse de stationnarité, qui est largement utilisé par les simulateurs, est vraie seulement sur une courte période et pour une longueur donnée de soudure. L’analyse macrographique montre, quant à elle, l'effet de la variation des paramètres d'entrée sur la structure et la géométrie de la soudure. / An investigation on hybrid welding physics is presented in the current work. A literature review describes main physical processes occurring during Laser-arc combination and shows main achievements and problematics met during process analysis. Physical processes were studied during joining of very thick materials. Two configurations were used. The first configuration is welding of Superduplex steel in one pass by Laser and arc that are far apart. The second configuration is multipass welding of 18MND5 steel, where defocused Laser beam intercepts arc plasma. With a help of experiment’s design, fast video imaging, electric signals recording, determination of temperature and workpiece distortion, were explained the role of each thermal source and influence of their combination on arc behaviour, molten pool creation, metallic drop transfer evaluation and heat distribution into welded plates. The relationships between electric signals and arc geometry, bath dimensions and heat distribution have been analyzed at various time scales. Thermal analysis, presented in this work, shows that hypothesis of stationarity, which is commonly used in numerical modelling, is true only during a short welding period and for a given weld length. Macrographic analysis shows effect of input parameters variation on weld’s structure and geometry.

Ephemeral wetlands provide numerous ecosystem services, but are disappearing due to urbanisation and habitat fragmentation. Knowledge is required to conserve these systems, but ephemeral wetland research in South Africa is lacking. As primary producers, microalgae provide a key link between the biotic and abiotic components of aquatic ecosystems. Despite their importance, there is a paucity in information concerning microalgal dynamics in ephemeral wetlands. The aim of this study was to understand the spatial and temporal dynamics of microalgae in ephemeral wetlands of the Nelson Mandela Bay Metropole. The research followed a funnel-based approach that assessed 35 wetlands at a regional level, followed by a temporal assessment of six wetlands, monitored biweekly, monthly or quarterly. Thereafter, a case study at local scale was carried out to address wetland connectivity and Hydrogeomorphic unit trends. The research culminated in a benthic flux chamber experiment, addressing the influence of microalgal-mediated processes on wetland development for a month post inundation. Phytoplankton biomass showed strong regional associations with rainfall zone, with Chl a concentrations of 17; 4.6; and 25 µg.L-1 in the high, intermediate and low rainfall zones, respectively. The MPB communities in Seeps, Depressions and Wetland flats, comprised between 45 and 60 % diatoms, whilst other microalgal groups were dominant in the water columns (> 90 %). Phytoplankton and MPB interactions facilitated significant night-time NH4+ and SRP effluxes, (1.5 and 0.4 mg.m-2.h-1, respectively) four days post inundation. High Silica uptake in the latter stages, was attributed to an increase in diatom abundance. Within the chambers, MPB growth was continuous whilst phytoplankton exhibited cyclical growth as the system approached dynamic equilibrium. This study demonstrated the importance of nutrient cycling in structuring aquatic food webs, and indicated the sensitivity of ephemeral wetlands to environmental perturbations.

Grâce à la qualité des cordons de soudure produits, le soudage TIG est l’un des procédés de soudage à l’arc les plus répandus dans l’industrie nucléaire. Au cours des travaux de cette thèse, nous proposons un modèle physique pour la simulation numérique du bain de fusion en soudage TIG d’aciers inoxydables austénitiques avec des teneurs en éléments tensioactifs différentes. L’objectif du modèle développé est de prédire la morphologie et les dimensions du cordon de soudure ainsi que les contraintes thermiques résultantes dans les pièces soudées en fonction des paramètres opératoires du procédé mais aussi en fonction des teneurs en éléments tensioactifs des métaux assemblés. Pour ce faire, les équations de la thermohydraulique sont couplées à celles de l’électromagnétisme et sont résolues en se basant sur le module « électrique » de Code_Saturne. Ce modèle a été vérifié dans un premier temps sur des configurations de soudage de matériaux homogènes avant d’être confronté à la simulation du soudage de matériaux de teneurs en éléments tensioactifs différentes. Des simulations des essais expérimentaux correspondants ont été réalisées et comparées aux mesures. La démarche adoptée a consisté à étudier les effets thermo-capillaires de manière découplée des effets électromagnétiques à partir d’essais de soudage laser en mode conduction. Les résultats de la confrontation des résultats numériques aux mesures expérimentaux démontrent que le modèle reproduit globalement bien la physique du procédé. Les limitations de notre modèle et les phénomènes qu’elle a permis de mettre en évidence ont été discutés et ont permis de proposer des pistes d’amélioration pour la modélisation. / The high quality of the weld bead makes GTA welding one of the most used welding processes in the nuclear industry. During this work, a physical model is proposed to simulate the weld pool during the GTA welding of stainless steels with different concentrations of surface active elements. This model aims to predict the weld bead shape, its geometrical characteristics and the thermal field induced by the process according to the operating parameters but also as a function of the surface active elements concentrations of welded metals.Based on the “electric” module of Code_Saturne®, the set of solved equations includes both fluid dynamics equations and electromagnetic ones. Before applying the model to the simulation of welding of stainless steels with different concentrations of surface active elements, this model has been studied through configurations of homogenous materials welding. Experiments are carried out and are compared to the corresponding simulations. In the approach used in this study, the thermo-capillary effects are studied separately from electromagnetic ones using conduction mode laser beam welding. The agreement obtained from comparative analysis between experimental results and numerical ones shows good reproduction of the process physics by the model developed. The modeling limitations and the phenomena identified by this study are discussed and orientations for future development are defined.

The doctrine of intellectual property is based on the assumption that the exclusivity to commercialize a novel product granted to an inventor creates incentives to conduct research. In some areas, however, intellectual property can constitute a barrier to development of social welfare. In the area of access to medicines in developing countries, the intellectual property-related problem can take two forms. When needed products are not being developed and thus do not exist, lack of availability occurs. Lack of accessibility, on the other hand, arises when necessary medicines do exist, but their prices are prohibitive for people from resource-poor countries. Based on a detailed analysis of the patent and trade environment in the pharmaceutical sector, the thesis examines the potential of patent pooling as a joint intellectual property management strategy to increase access to medicines within the existing international intellectual property system. Particularly, it analyzes the effects of an existing pharmaceutical pool, the Medicines Patent Pool, on accessibility of antiretroviral medicines in low and middle income countries.

The current shortage of crude oil from conventional sources has increased interest in developing unconventional resources such as oil sands. Heavy crudes and bitumen are found in Northern Alberta and their exploration, processing, and transport to market pose challenges in the use of these resources. Part of the solution to these challenges involves the reactive thermal processing of heavy crudes and bitumen. This thesis focused on mild thermal cracking reactions, and two studies regarding these reactions were presented. The first was an experimental study performed in a pilot-scale semi-batch reactor. The three crude oils were heated to 350, 400, 425, and 450°C at 1240 kPa. A five-lump reaction model combined with a process simulator with VLE calculations was fitted with the experimental data obtained. The goodness of fit between the model predicted values and experimental values for the Hardisty (MBL), Albian Heavy Synthetic (AHS), and Christina Lake Dilute Bitumen (CDB) were determined to be 0.99, 0.99, and 0.98, respectively. Moreover, 80, 85, and 89% of the optimized model’s predicted values had less than 10% error for MBL, AHS, and CDB, respectively. The second study described the implementation of a mild thermal cracking reaction model to the development of a train car fire-model for the assessment of safety aspects in the design of train cars used to transport crude oil. Case studies were conducted using the UniSim® depressuring utility and a previously developed mild thermal cracking reaction model to demonstrate the effect of compositional change. Three crude oils with varying properties and representative of the types of crudes transported by rail in Canada were used here: MBL, AHS, and CDB. The case studies conducted showed the performance of a train car fire-model to be dependent on the crude oil characteristics: up to -57% and -99% difference in model predicted variables for AHS and CDB, respectively, when compared to MBL. Furthermore, the model’s performance was also shown to be affected by the compositional change of a given crude oil due to mild thermal cracking reactions: up to 42% difference in model predicted variables when compared to the base case.

Laser welding is commonly used in the automotive-, steel- and aerospace industry. It is a highly non-linear and coupled process where the weld geometry is strongly affected by the flow pattern in the melt pool. Experimental observations are challenging since the melt pool and melt flow below the surface are not yet accessible during welding. Improved process control would allow maintaining, or improving, product quality with less material and contribute further to sustainability by reducing production errors. Numerical modelling with Computational Fluid Dynamics, CFD, provides complementary understanding with access to process properties that are not yet reachable with experimental observation. However, the existing numerical models lack predictability when considering the weld shape. The work presented here is the development of a model for conduction laser welding. The solver upon which the model is based is first described in detail. Then different validation cases are applied in order to test specific parts of the physics implemented. Two cases focus on thermocapillary convection in two-phase and three-phase flows with surface deformation. Finally, a third case considers the melt pool flow during conduction mode welding.It is concluded that the convection of fusion enthalpy, which was neglected in former studies, should be included in the model. The implementation of the thermo capillary force is recommended to be consistent with the other surface forces to avoid unphysical solution. Free surface oscillations, known from experimental observations, are also computed numerically. However, further investigation is needed to check that these oscillations are not disturbed b ynumerical oscillations.

Additive manufacturing (AM) – and laser powder bed fusion (LPBF) specifically – constructs geometry that would not be possible using standard manufacturing techniques. This geometric versatility allows integration of multiple components into a single part. While this practice can reduce weight and part count, there are also serious drawbacks. One is that the LPBF process can only build parts with a single material. This limitation generally results in over-designing some areas of the part to compensate for the compromise in material choice. Over-designing can lead to decreased functional efficiency, increased weight, etc. in LPBF parts. Methods to control the material composition spatially throughout a build would allow designers to experience the full benefits of functionality integration. Spatial composition control has been performed successfully in other AM processes – like directed energy deposition and material jetting – however, these processes are limited compared to LPBF in terms of material properties and can have inferior spatial resolution. This capability applied to the LPBF process would extend manufacturing abilities beyond what any of these AM processes can currently produce. A novel concept for spatial composition control – currently under development at Brigham Young University – utilizes liquid or liquid-encased dopants to selectively alter the composition of the powder bed, which is then fused with the substrate to form a solid part. This work is focused on evaluating the feasibility and usefulness of this novel composition control process. To do this, the present work evaluates two deposition methods that could be used; explores and maps the laser parameter process space for zirconia-doped SS 316L; and investigates the incorporation of zirconia dopant into SS 316L melt pools. In evaluating deposition methods, inkjet printing is recommended to be implemented as it performs better than direct write material extrusion in every assessed category. For the process space, the range of input parameters over which balling occurred expanded dramatically with the addition of zirconia dopant and shifted with changes in dopant input quantities. This suggests the need for composition-dependent adjustments to processing parameters in order to obtain desired properties in fused parts. Substantial amounts of dopant material were confirmed to be incorporated into the laser-fused melt tracks. Individual inclusions of 100 $nm$ particles distributed throughout the melt pool in SEM images. Howewver, EDX data shows that the majority of the incorporated dopant material is located around the edges of the melt pools. Variations of dopant deposition, drying, and laser scanning parameters should be studied to improve the resulting dopant incorporation and dispersion in single-track line scans. Area scans and multi-layer builds should also be performed to evaluate their effect on dopant content and dispersion in the fused region.