Evaluation de l'exposition des organismes aux hydrocarbures aromatiques polycycliques (HAP) dansle milieu marin par le dosage des métabolites de HAP

Afin d'étudier la santé d'un écosystème marin et le potentiel toxique d'une contamination telle que celle liée à la présence d'hydrocarbures aromatiques polycycliques (HAP), il est nécessaire, outre de connaître les niveaux de contamination du milieu, de pouvoir accéder à la fraction à laquelle les organismes aquatiques ont été exposés et de connaître les effets toxiques des contaminants incriminés (effets toxiques qui peuvent être reliés aux phénomènes de biotransformation des contaminants). L'exposition et la contamination des organismes aquatiques aux HAP ont généralement été évaluées par le dosage des HAP bioaccumulés dans les tissus. Or, cette approche est critiquable si l'on tient compte des capacités de biotransformation des organismes, notamment des vertébrés, et des propriétés toxiques des produits de transformation formés. Dans ce contexte, l'objectif de cette thèse est d'évaluer le potentiel des métabolites de HAP dans le but d'étudier l'exposition et la contamination des organismes aux HAP dans l'environnement marin. Une méthode de dosage des métabolites de HAP dans les matrices biologiques a tout d'abord été mise au point. Ensuite, cet outil analytique a été appliqué lors d'expositions de poissons à des HAP individuels et à différents produits pétroliers en milieu contrôlé qui ont permis de mieux appréhender les phénomènes de biotransformation des HAP. Enfin, des études de terrain ont été réalisées, notamment dans le cadre du suivi de la marée noire Erika et de l'étude de la contamination de la baie de Seine, montrant l'applicabilité du dosage des métabolites de HAP afin d'évaluer l'exposition et la contamination des organismes aux HAP en milieu naturel dans des contextes de pollution de nature différente.In order to study the health of a marine ecosystem and the toxic potential of a contamination such as the one related to the presence of polycyclic aromatic hydrocarbons (PAHs), it is necessary, in addition to the determination of environmental contamination levels, to have access to the fraction aquatic organisms have been exposed to and to identify the toxic effects of the contaminants (toxic effects which can be related to biotransformation phenomena of contaminants). The exposure and contamination of aquatic organisms to PAHs have generally been evaluated by the quantification of bioaccumulated PAHs in tissues. However, this approach is open to criticism when taking into account the biotransformation capabilities of organisms such as vertebrates and the toxic properties of biotransformation products. In this way, the aim of this study is to evaluate the potential of PAH metabolites in order to study the exposure and contamination of organisms to PAHs in the marine environment. An analytical technique to quantify PAH metabolites in biological matrices has first been set up. Then, this analytical tool has been applied to the study of fish exposures to individual PAHs and to different petroleum products in controlled conditions which has allowed to get a better understanding of PAH biotransformation phenomena. Finally, field studies have been led, notably to study the Erika oil spill and the contamination of the Seine bay, demonstrating the applicability of the quantification of PAH metabolites to evaluate the exposure and the contamination of organisms to PAHs in natural environment and for pollution events of different nature

Highlighting the effects of co‐eluting interferences on compound specific stable isotope analysis of polycyclic aromatic hydrocarbons using comprehensive two‐dimensional gas chromatography

Accuracy is the most important issue when carrying out compound specific stable isotope analysis of polycyclic aromatic hydrocarbons extracted from complex samples. It depends on two main factors: the possible isotopic fractionation of the compounds during extraction and the potential co‐elution with interfering compounds with different isotopic signatures. We present here a simplified pressurised liquid extraction method for compound specific stable isotope analysis of polycyclic aromatic hydrocarbons (PAHs) in non‐aqueous phase liquids of coal tar. Samples extracted using the new method and using fractionation on silica gel column were analysed using comprehensive twodimensional gas chromatography. We were able to evaluate the effect of coelution on carbon and hydrogen stable isotope signatures of the 16 US EPA priority PAHs in the coal tars with various proportions of aromatic and aliphatic content. Even in samples that presented a good baseline resolution, the PAHs of interest co‐eluted with other aromatic compounds with a notable effect on their stable isotope values; it demonstrated the necessity to check the quality of all extraction and clean‐up methods (either the simplified pressurized liquid extraction or more traditional labour‐intensive methods) for the more complex samples prior to data interpretation. Additionally, comprehensive twodimensional gas chromatography enabled visualisation of the suspected coelutions for the first time

The Role of Oxidation Compounds in Biofilm Growth on Polyethylene Geomembrane Barriers Used in Landfill

In a model study, polyethylene was preoxidized and incubated for a period of 7 months at 40°C in two different municipal solid waste leachates. During the postexperimental analyses, specific attention was paid to the carbonyl species and carboxylic acid depletion during the environmental exposure because it is well known that carboxylic acids are believed to be a potential substrate for the development of microorganisms. The results showed that the carbonyl as well as the carboxylic acid depletion observed follows first-order kinetics. The biofilm formation was characterized using a suite of analytical techniques, and its formation was compared with the carboxylic acid and carbonyl depletion profil

Optical pump-rejection filter based on silicon sub-wavelength engineered photonic structures

The high index contrast of the silicon-on-insulator (SOI) platform allows the realization of ultra-compact photonic circuits. However, this high contrast hinders the implementation of narrow-band Bragg filters. These typically require corrugations widths of a few nanometers or double-etch geometries, hampering device fabrication. Here we report, for the first time, on the realization of SOI Bragg filters based on sub-wavelength index engineering in a differential corrugation width configuration. The proposed double periodicity structure allows narrow-band rejection with a single etch step and relaxed width constraints. Based on this concept, we experimentally demonstrate a single-etch, $\mathbf{220\,nm}$ thick, Si Bragg filter featuring a corrugation width of $\mathbf{150\,nm}$, a rejection bandwidth of $\mathbf{1.1\,nm}$ and an extinction ratio exceeding $\mathbf{40\,dB}$. This represents a ten-fold width increase compared to conventional single-periodicity, single-etch counterparts with similar bandwidths

Recent evolution of the coral reefs of Guadeloupe and Saint-Barthelemy Islands

The Guadeloupe Archipelago (with Guadeloupe, La Désirade, Marie-Galante, Les Saintes and Petite-Terre Islands), St. Barthélemy and St. Martin are located in the Lesser Antilles between 15°50’and 18°00’ N. Guadeloupe possesses a barrier reef on its northern part, fringing reefs on the windward coast and highly diversified non-reef building coral communities on the leeward coast. The other islands shelter fringing reefs and non-reef building coral communities. The coral reefs of the French West Indies are faced with a common set of threats : high rate of sedimentation, due to deforestation and bad land management, and algal proliferation due to an overload of nutrients in the coastal waters coming from excessive use of fertilizers and poor waste waters treatment. Their coral communities have exhibited a low progressive decline since the beginning of the eighties. Long-term monitoring sites have been implemented in Guadeloupe and St. Barthélemy since 2001. Results indicated the existence of a signifi cant tendency of the coral community to degrade over the study period. Moreover, a severe bleaching event appeared in 2005, when the sea temperature overshoot 29°C from mid May to mid November, with maximum values reaching 31°C. In 2006, in spite of normal seawater temperature conditions, an important delayed mortality affected the corals previously weakened by bleaching. As a final result of the 2005 bleaching event, coral coverage on the reefs of Guadeloupe and St. Barthélemy dropped from 30 to 50 % according to the sites. Fish communities did not exhibit immediate impact of the bleaching eventL'Archipel guadeloupéen (les îles de la Guadeloupe, la Désirade, Marie-Galante, les Saintes et Petite-Terre), ainsi que Saint-Barthélemy et Saint-Martin sont situés dans les Petites Antilles entre 15° 50'N et 18°00' N. La Guadeloupe abrite un récif barrière sur sa côte nord, des récifs frangeants sur les côtes au vent et des formations coralliennes non-bioconstructrices, riches et diversifiées, sur les côtes sous-le-vent. Les autres îles possèdent des récifs frangeants et des formations coralliennes non-bioconstructrices. Les récifs coralliens des Antilles françaises subissent principalement deux types de perturbation: 1) une hypersédimentation liée à la déforestation des îles et à des aménagements côtiers mal réfléchis ; 2) un enrichissement excessif des eaux côtières en nutriments, provenant d'un mauvais traitement des eaux usées et de fertilisants agricoles, qui favorisent le développement exubérant d'algues sur les récifs. Les récifs de ces îles ont montré des signes de dégradation depuis le début des années 80. Depuis 2001, un réseau de stations de suivi de l'état de santé des communautés récifales a été mis en place sur des récifs de Guadeloupe et de Saint-Barthélemy. Les résultats de cette étude mettent en évidence une tendance significative décroissante de l'état de santé des communautés coralliennes. Par ailleurs, en 2005, la température des eaux côtières dans les Antilles a dépassé 29°C de la mimai à la mi-novembre, avec des maxima atteignant 31 °C. Cet événement a provoqué le phénomène de blanchissement des coraux le plus important observé à ce jour dans ces îles. Apparue dès octobre 2005, la mortalité des coraux s'est particulièrement développée en 2006, où elle a constitué, malgré des conditions de température normales, un phénomène retardé. Cet épisode de blanchissement s'est traduit par une diminution de 30 à 50 % du taux de recouvrement des fonds par les coraux en fonction des récifs. Les peuplements de poissons récifaux n'ont pas été affectés de façon immédiate par le blanchissement

ImPro: Immersive Prototyping in Virtual Environments for Industrial Designers

Computer-Aided Design (CAD) constitutes an important tool for industrial designers. Similarly, Virtual Reality (VR) has the capability to revolutionize how designers work with its increased sense of scale and perspective. However, existing VR CAD applications are limited in terms of functionality and intuitive control. Based on a comparison of VR CAD applications, ImPro, a new application for immersive prototyping for industrial designers was developed. The user evaluations and comparisons show that ImPro offers increased usability, functionality, and suitability for industrial designers.TUMCREATE Phase 2, funded by the National Research Foundation (NRF) Singapore under its Campus for Research Excellence and Technological Enterprise (CREATE) programm

Ligament Healing After Anterior Cruciate Ligament Rupture: An Important New Patient Pathway?

Recent studies have shown satisfactory functional results after spontaneous healing of a ruptured anterior cruciate ligament (ACL). However, current literature on this topic may exclude important parting selection, outcome measures, and long-term results. Rehabilitation protocols applied in those studies, as well as objective assessments appear far from the usual gold standard after ACL reconstruction. Ideally, outcomes measures should be based on the same testing procedures that are recommended to clear an athlete to return to sport following ACL reconstruction. There is still a lot to understand in how an injured ACL may heal, and therefore ACL injury management should be individualized to each patient and carefully discussed