Les précédentes estimations des températures profondes en France mettent en évidence trois anomalies thermiques positives principales dont une est centrée entre Marseille et Montpellier. Ce travail de thèse présente l'étude du régime thermique du Bassin du Sud-Est à partir d'une réévaluation des températures profondes corrigées des effets thermiques transitoires générés lors des mesures en forage pétrolier. 203 données BHT corrigées et 10 DST (mesures stables) issues de 103 forages ont ainsi été obtenues. Le gradient thermique moyen du Bassin (31,3°C/km) est proche de la moyenne française (32,5°C/km) mais les gradients locaux varient d'environ 20 à 45°C/km. Une analyse géostatistique nous a permis de construire un modèle thermique de représentation 3D de la surface à 6km de profondeur duquel nous avons extrait des coupes et cartes thermiques à différentes profondeurs. De nouvelles anomalies thermiques de plus petite échelle ont ainsi pu être identifiées, certaines étant positives (du côté de Montpellier, Lodève, Gap et La Drôme) et d'autres négatives (dans les Cévennes et la région d'Aix-en-Provence). Une compilation de données géophysiques nous a permis de discuter ces anomalies en termes de géologie locale et de phénomènes à grande échelle (variations de profondeur du Moho, épaisseur des sédiments), mais il semble que des circulations de fluides puissent mieux expliquer la localisation, l'amplitude et les longueurs d'ondes des signaux thermiques qui suivent la direction des failles majeures en surface. Le rôle de la circulation de fluides dans la mise en place et l'évolution des anomalies thermiques au sein des zones de faille est illustré par des modèles numériques en régime stationnaire et transitoire. Ces modèles permettent de reproduire des anomalies de plusieurs dizaines de degrés. Ce phénomène est amplifié lorsqu'une anisotropie de perméabilité est prise en compte. De plus, la dépendance de la perméabilité avec la profondeur permet d'obtenir des superpositions d'anomalies positives et négatives sur un même profil vertical comme nous l'observons sur les coupes thermiques issues des mesures. Loin des zones perméables, les anomalies peuvent s'expliquer par des processus conductifs au sein d'objets dans lesquels les contrastes de conductivité thermique peuvent être importants. L'anisotropie de conductivité dans les formations argileuses peut être responsable du développement d'anomalies proches de celles observées entre les zones perméables. Enfin, les circulations hydrothermales dans les zones de faille associées à des sédiments anisotropes pourraient expliquer la forme, l'évolution en profondeur et l'intensité des anomalies thermiques identifiées.

The major objectives of this study were to investigate the antioxidant properties of flaxseed lignans secoisolariciresinol (SECO 2) and secoisolariciresinol diglycoside (SDG 1) and their major oxidative compounds using 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH 47) in an in vitro model of lipid peroxidation. This investigation was facilitated by the structural elucidation of the major oxidative compounds and the ability of flaxseed lignans to delay the onset of oxidation in two model systems. <p>This study showed that SECO 2 oxidation occurs at the aromatic (4-OH) and aliphatic (9-OH) hydroxyl groups. Conversely for SDG 1, only compounds derived from the oxidation of aromatic hydroxyl groups were obtained because the 9-OH position is glucosylated. <p>SECO 2 oxidation with AAPH 47 showed that the intermediate 2a is most likely involved in the generation of early-forming (48 and 52) and 2c for the formation of late-forming (49, 50 and 51) oxidation compounds. Compound 48 is formed from dimerization of 2a that is converted to 52 and then to 51. Compound 50 was formed by the addition of a carbon-centre free radical of AAPH (AP radical) to 2c. Compounds 50 and 51 trap carbon-centered AP radicals supporting SECO 2 as a chain-breaking antioxidant and AAPH 47 as a proper model for study of SECO 2 oxidation in vitro. <p>SDG 1 oxidation with AAPH 47 indicated that intermediates 1b and 1c are most likely involved for the formation of early forming compounds (55 and 58) and 1a leads to the late forming compounds (56 and 57). Compound 55 is a result of dimerization. Compound 56 may be directly formed via intermediate radical 1a by adding AP free radicals. Compound 56 was a stable non-radical compound that could trap AP free radicals, thereby supporting SDG 1 as a chain-breaking antioxidant. Hydrogen abstraction from 4-hydroxyl yielded the radical 1a and hydroxyl radical addition to 1a yielded 57. Compound 58 formed from the addition of OH or H2O to 1c. <p>This study demonstrated that AAPH 47 produces carbon-centred AP radicals upon thermal decomposition and mimics the formation of lipid peroxyl radicals. Interaction of carbon-centred AP radicals with SECO 2 and SDG 1 provides a good model to study the antioxidant reactions of SECO 2 in vitro. p*The relative antioxidant capacity of the flaxseed lignans versus BHT 17, in two model systems, was determined. The stoichiometric ratio for SECO 2 and SDG 1 were 1.5 and 1.1-1.2, respectively, compared to BHT 17 (2.0). The induction time by Rancimat analyzer measured inhibition of autoxidation mediated by flaxseed lignans SECO, SDG and SDG polymer in comparison with BHT 17. The induction time data demonstrated that SECO 2 protected canola oil better than either SDG 1 or SDG polymer 3. <p>These results are important for better understanding about the chemistry behind flaxseed lignan antioxidant activities. This study provided useful evidence that flaxseed lignans can be used as natural antioxidants.

The major objectives of this study were to investigate the antioxidant properties of flaxseed lignans secoisolariciresinol (SECO 2) and secoisolariciresinol diglycoside (SDG 1) and their major oxidative compounds using 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH 47) in an in vitro model of lipid peroxidation. This investigation was facilitated by the structural elucidation of the major oxidative compounds and the ability of flaxseed lignans to delay the onset of oxidation in two model systems. <p>This study showed that SECO 2 oxidation occurs at the aromatic (4-OH) and aliphatic (9-OH) hydroxyl groups. Conversely for SDG 1, only compounds derived from the oxidation of aromatic hydroxyl groups were obtained because the 9-OH position is glucosylated. <p>SECO 2 oxidation with AAPH 47 showed that the intermediate 2a is most likely involved in the generation of early-forming (48 and 52) and 2c for the formation of late-forming (49, 50 and 51) oxidation compounds. Compound 48 is formed from dimerization of 2a that is converted to 52 and then to 51. Compound 50 was formed by the addition of a carbon-centre free radical of AAPH (AP radical) to 2c. Compounds 50 and 51 trap carbon-centered AP radicals supporting SECO 2 as a chain-breaking antioxidant and AAPH 47 as a proper model for study of SECO 2 oxidation in vitro. <p>SDG 1 oxidation with AAPH 47 indicated that intermediates 1b and 1c are most likely involved for the formation of early forming compounds (55 and 58) and 1a leads to the late forming compounds (56 and 57). Compound 55 is a result of dimerization. Compound 56 may be directly formed via intermediate radical 1a by adding AP free radicals. Compound 56 was a stable non-radical compound that could trap AP free radicals, thereby supporting SDG 1 as a chain-breaking antioxidant. Hydrogen abstraction from 4-hydroxyl yielded the radical 1a and hydroxyl radical addition to 1a yielded 57. Compound 58 formed from the addition of OH or H2O to 1c. <p>This study demonstrated that AAPH 47 produces carbon-centred AP radicals upon thermal decomposition and mimics the formation of lipid peroxyl radicals. Interaction of carbon-centred AP radicals with SECO 2 and SDG 1 provides a good model to study the antioxidant reactions of SECO 2 in vitro. p*The relative antioxidant capacity of the flaxseed lignans versus BHT 17, in two model systems, was determined. The stoichiometric ratio for SECO 2 and SDG 1 were 1.5 and 1.1-1.2, respectively, compared to BHT 17 (2.0). The induction time by Rancimat analyzer measured inhibition of autoxidation mediated by flaxseed lignans SECO, SDG and SDG polymer in comparison with BHT 17. The induction time data demonstrated that SECO 2 protected canola oil better than either SDG 1 or SDG polymer 3. <p>These results are important for better understanding about the chemistry behind flaxseed lignan antioxidant activities. This study provided useful evidence that flaxseed lignans can be used as natural antioxidants.

Butylated Hydroxyanisole, BHA, and Butylated Hydroxytoluene, BHT, are commonly used as preservatives for our food as well as additives in many products such as cosmetics, petroleum, and medicine. Although their use has been approved by the Food and Drug Administration (FDA), there have been controversies and debates on whether these phenol derivatives or antioxidants are safe to use. Their accumulative toxicology and side effects need to be thoroughly investigated as we continue to consume them on a daily basis. Data obtained by genomic analysis in Tang lab suggested the involvement of DNA damage checkpoint/repair pathways in the response network to these phenol stress factors. The aims of this thesis are to examine the morphological changes and potential DNA damage induced by exposing cells to BHA and BHT using fission yeast Schizosaccharomyces pombe as a model organism. Fluorescence microscopy was used to assess DNA double-strain breaks (DSBs) by monitoring the nuclear foci formation of Rad22, a DNA repair protein, in the presence of BHA and BHT. Changes in cell morphology were also studied under microscope. Preliminary data showed that cells treated with BHA and BHT exhibited morphological changes. In addition, for the first time in S. pombe cells, Rad22 foci in the nucleus of BHA and BHT treated cells were observed. Further investigation is needed to optimal the experimental condition to continue the study. These results will not only help us to better understand the effect of these phenol derivatives in the cells, but can also establish an experimental system for future studies on the interaction of the cells with stress factors and therapeutic drugs for human-related diseases such as cancer.

Le système d’injection Diesel doit résister à des conditions opératoires (pression, température) de plus en plus sévères, et être compatible avec les évolutions du carburant diesel, telles que l’introduction des Esters Méthyliques d’Acide Gras (EMAG) et l’utilisation de différents additifs, qui peuvent affecter la durabilité des véhicules, suite à la formation de dépôts. L’objectif des travaux de cette thèse est la compréhension des mécanismes de formation des dépôts issus de l’oxydation des carburants et la détermination des paramètres majeurs participant aux interactions dépôts-substrats (état de surface, matériaux, géométrie, thermique…). Deux études ont été abordées dans cette thèse. La première étude porte sur l’oxydation accélérée des carburants Diesel, des EMAG et des mélanges Diesel/EMAG en phase liquide en utilisant le moyen d’essai PetroOxy, la cinétique d’oxydation a été déterminée pour les différents carburants et la caractérisation des produits d’oxydation a été effectuée utilisant les moyens d’analyse (FTIR-ATR, ATG/DTG et GC/MS). La seconde étude est dédiée à la reproduction du dépôt sur les substrats en (aluminium, acier inoxydable, PEEK, revêtement or sur aluminium, revêtement silcoklean sur acier inoxydable) en utilisant le moyen d’essai Micro Cokage et la caractérisation du dépôt obtenu dans chaque cas en utilisant les moyens d’analyse (FTIR-ATR, ATG/DTG, FEG et XPS). Les résultats de ces travaux ont permis de déterminer l’impact de la nature et du taux d’EMAG ajouté au Diesel sur la stabilité à l’oxydation des carburants ; de mettre en place une hypothèse de formation de dépôt à partir de l’oxydation des carburants en phase liquide jusqu’à la formation de nanoparticules de dépôt sphériques ; et déterminer l’impact du substrat sur la formation et l’adhésion du dépôt à la surface du matériau. / Diesel injection system must withstand more severe operating conditions (pressure, temperature), and be compatible with the evolution of diesel fuel, such as the introduction of Fatty Acid Methyl Esters (FAME) and use of different additives, which may affect the durability of the vehicle, following the formation of deposits. The objective of this work is to understand the mechanisms of deposit formation from fuel oxidation and determine the major parameters involved in deposit-substrate interactions (surface condition, materials, geometry, temperature...). Two studies were discussed. The first study focuses on the liquid phase accelerated oxidation of Diesel fuel, FAME and mixtures (Diesel / FAME) using PetroOxy device, the oxidation kinetic was determined for the different fuels and characterization of oxidation products was carried out using the (FTIR-ATR, ATG / DTG and GC / MS). The second study was dedicated to the reproduction of deposit on different substrates (aluminum, stainless steel, PEEK, aluminum coating on gold, silcoklean coating on stainless steel) using the Micro Coking device, and characterization of the deposit obtained in each case using (FTIR-ATR, ATG / DTG, XPS and FEG). The results of this work permit to determine the impact of FAME nature and FAME concentration on fuel oxidation stability; an hypothesis was proposed to explain deposit formation.