ED Mathématiques et Informatique
Development of an algebraic multigrid solver for the indefinite Helmholtz equation
by Clément RICHEFORT (LaBRI - Laboratoire Bordelais de Recherche en Informatique)
The defense will take place at 14h00 - Salle Ada Lovelace de l'INRIA 200 Avenue de la Vieille Tour 33405 Talence
in front of the jury composed of
- Pierre RAMET - Professeur - Université de Bordeaux - Directeur de these
- Edmond CHOW - Professor - Georgia Institute of Technology - Rapporteur
- Stéphanie CHAILLAT-LOSEILLE - Directrice de recherche - ENSTA-UMA - Rapporteur
- Ulrich RÜDE - Professor - Friedrich-Alexander-Universität - Examinateur
- Vandana DWARKA - Docteur - TU Delft - Examinateur
The numerical simulation of complex physical phenomenon generally requires to solve systems of linear equations. The solver should benefit from modern computing machines and scale on highly parallel architectures. In particular, multigrid methods are scalable methods that enable the resolution of a wide range of problems where the discretization matrix is symmetric positive definite. This thesis aims at extending multigrid methods to the oscillatory and indefinite Helmholtz equation. While traditional multigrid methods assume positive matrices, our multigrid operators should be adapted to eventually negative eigenvalues and an oscillatory near-kernel space. In particular, the smoother should capture large eigenvalues independently on the sign. Moreover, the near-kernel space is not characterized by a slowly varying shape. Therefore, the interpolation operators should now propagate an oscillatory space that is unknown at the set-up phase of multigrid. Last, since the indefinite matrix does not generate a norm, the coarse correction should be adapted to not amplify the error but to contract it along the iterations of the method. As we target a method that converges in a constant number of iterations independently on the size of the problem, various numerical experiments are presented along this thesis with respect to the indefiniteness and the size of the problem.
ED Sciences Chimiques
Tip-enhanced Raman spectroscopy for the characterization of biological systems: From nanoscale chemical and structural imaging in air to its development in liquid media
by Gary COONEY (Institut des Sciences Moléculaires)
The defense will take place at 10h00 - Salle de Conférence (3ème Est) Institut des Sciences Moléculaires, Bâtiment A12, Université de Bordeaux, 351 Cours de la Libération, 33400 Talence
in front of the jury composed of
- SEBASTIEN BONHOMMEAU - Maître de conférences - Institute of Molecular Sciences - University of Bordeaux - Directeur de these
- Isabel ALVES - Directrice de recherche - Institute of Chemistry & Biology of Membranes & Nano-objects (CBMN) - Examinateur
- Dai ZHANG - Associate Professor - The Institute of Physical and Theoretical Chemistry, University of Tübingen - Rapporteur
- Olivier PIOT - Professeur - BioSpectroscopie Translationnelle, Université de Reims Champagne-Ardenne - Rapporteur
The aims of this thesis are the development of tip-enhanced Raman spectroscopy (TERS) for applications in liquid media, specifically for the study of lipid membranes and amyloid proteins which are implicated in neurodegenerative diseases like Alzheimer's. TERS overcomes the diffraction limit of conventional Raman spectroscopy by combining the high spatial resolution of scanning probe microscopy with the chemical specificity of surface-enhanced Raman spectroscopy (SERS). By employing a metal-coated nano-tapered scanning probe microscopy probe tip, TERS generates a localised enhancement of the Raman signal at the tip apex. This enables the study of optically non-resonant biomolecules at the nanoscale in a label-free and non-destructive manner. The key challenges that are addressed in this work include the fabrication of TERS-active tips, the optimisation of our novel total-internal reflection (TIR)-TERS system for use in liquid environments, and the handling of the complex data obtained from hyperspectral TERS imaging. Amyloid proteins in the form of Tau fibrils were studied using this TIR-TERS setup with heparin-induced Tau fibrils being a benchmark for evaluating the performance of the system. TERS studies of RNA-induced Tau fibrils provided insight into the underlying formation mechanisms of amyloid fibrils. In addition, these data were used to explore the use of chemometric methods, such as Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA), for their fine analysis. These methods were evaluated in the context of more traditional peak-picking methods. This thesis also details the development of a liquid-compatible TIR-TERS system and its application to the study of supported lipid bilayers in aqueous media. This advancement enables the nanoscale investigation of lipid membranes in biologically relevant media, which is more representative compared to TERS in air. With the outlook of future works investigating protein-lipid interactions, these innovations are crucial for understanding amyloid fibril formation and their deleterious effects on neuronal cells. To conclude, this thesis enhances TERS as a tool for studying biomolecular structures in the context of neurodegenerative diseases at the nanoscale, and the optimised TIR-TERS system provides a platform for future research in biological and biomedical applications.
Development of UO2 fuel doped with a niobium oxide redox buffer
by Shalane GOBERT (ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux)
The defense will take place at 14h00 - Amphithéâtre IRFM CEA Cadarache 13108, Saint-Paul-lez-Durance
in front of the jury composed of
- Jean-Marc HEINTZ - Professeur des universités - Bordeaux INP, ENSMAC - Directeur de these
- Fabienne AUDUBERT - Directeur de recherche - CEA - Directeur de these
- Nicolas CLAVIER - Directeur de recherche - Université de Montpellier - Rapporteur
- Damien BREGIROUX - Maître de conférences - Sorbonne Université - Rapporteur
- Laurence CROGUENNEC - Directeur de recherche - CNRS ICMCB - Examinateur
- Jérôme ROGER - Maître de conférences - Université de Bordeaux - Examinateur
- Anne-Charlotte ROBISSON - Ingénieure de recherche - CEA - Examinateur
- Fabrice ROSSIGNOL - Directeur de recherche - Université de Limogaes - Examinateur
An innovative nuclear fuel doped with a redox buffer has been developed to control the partial oxygen pressure within the fuel inside the reactor, within an oxygen potential range that would limit stress corrosion cracking of the cladding. The selected redox buffer couple is Nb2O5/NbO2. The densification behavior of doped UO2 fuel has been stidied: the effect of dopant concentration and particle size was evaluated by monitoring the linear shrinkage and oxygen release from the pellet during the sintering process of doped UO2 under a reducing atmosphere. This method revealed a reduction of niobium oxides during sintering, leading to oxygen release, which appears to influence both the densification behavior and the microstructure of the doped fuel. Heat treatments at higher oxygen potentials indicated a reactivity between niobium oxides and UO2, forming ternary compounds such as UNb2O7 or UNb3O10. This study complements and challenges existing thermodynamic data on the U-Nb-O system. Additionally, the effect of the redox buffer on UO2 behavior has been confirmed: the electrochemical monitoring of niobium-doped fuel, subjected to various thermodynamic conditions (T and pO2), demonstrated a regulation of the oxygen activity in UO2 fuel and revealed the existence of an activation temperature for the buffer couple, which has been estimated.
ED Sociétés, Politique, Santé Publique
Mega sporting events and international relations: The organization of the Rabat 2019 African Games.
by Hajar AJOUGHLAL (Laboratoire Cultures, Education, Sociétés)
The defense will take place at 9h00 - Salle du conseil Faculté des STAPS, Deuxième étage du bâtiment Rougier, 12 avenue Camille Jullian 33600 PESSAC
in front of the jury composed of
- André SUCHET - Maître de conférences - Université de Bordeaux - Directeur de these
- Jean-francois LOUDCHER - Professeur des universités - Université de Bordeaux - Examinateur
- Nicolas CHANAVAT - Professeure des universités - Université Jean Monnet - Examinateur
- Mahfoud AMARA - Associate Professor - Qatar University - Rapporteur
- Charles MERCIER - Professeur des universités - Université de Bordeaux - CoDirecteur de these
- Anne-Marie MAMONTOFF - Professeur des universités - Université de Perpignan - Rapporteur
The aim of this thesis is to question the underlying stakes behind the organization of the 2019 African Games, through a study of the motivations and perceptions of the event's stakeholders, hypothesizing the instrumentalization of these regional sports games as a soft power tool. In a geopolitical context marked by Morocco's readmission to the African Union after more than three decades of absence, beyond the sporting stakes and internal dynamics of the organization, sport emerges through this case study as the showcase for a new relational framework between Morocco and other African countries. This new vision is based on the principles of South-South cooperation, which differs from the historically associated North-South or South-North visions linked to the colonial past. To study and explain the use of this third-order sporting mega-event for geopolitical purposes, we mobilized the figurational approach to geopolitics and sport inspired by the figurational sociology of Norbert Elias. Our work is based on participant observations during our work as a volunteer at the Games, and on semi-structured interviews we conducted with people involved at various levels of the organization. Then, in order to capture the discourse produced on the event, we chose to analyze the archives of the national, regional and international print and audiovisual media, to which we added an analysis of the archives of the organizing committee.