ED Sciences de la Vie et de la Santé
Identification and characterization by diffusion MRI of new macroscopic cardiac structures
by Pierre CABANIS (Centre de Résonnance Magnétique des Systèmes Biologiques)
The defense will take place at h00 - amphithéâtre IHU Liryc, Av. du Haut Lévêque, 33600 Pessac
in front of the jury composed of
- Soumaya SRIDI CHENITI - Praticienne hospitalière - CHU de Bordeaux - Examinateur
- Stanislas RAPACCHI - Chargé de recherche - CHUV Lausanne - CNRS - Examinateur
- Magalie VIALLON - Directrice de recherche - CREATIS - Rapporteur
- Maxime SERMESANT - Directeur de recherche - Inria Epione, Université Côte d'Azur - Rapporteur
The complex architecture of cardiomyocytes is essential to the contractile function of the heart. Abnormalities in this organization can be at the root of serious cardiac pathologies. This thesis focuses on the in-depth analysis of discontinuities between myocardial cells using high-field diffusion magnetic reso- nance imaging. By exploiting the enhanced capabilities of this technology at 9.4 T, we have been able to identify and precisely characterize interruptions in the orien- tation of cardiac cells and cardiac laminae, which are often associated with areas of mechanical and electrical vulnerability in the myocardium. The aim of this research is not only to provide a detailed map of the three- dimensional structure of the myocardium, but also to highlight discontinuities that could play a key role in the development of disorders such as cardiac arrhythmias or myocardial fibrosis. Thanks to this innovative approach, it is possible to envisage new diagnostic and therapeutic strategies for heart disease by identifying previously inaccessible structural markers. This thesis focuses first on the analysis of the ventricular insertion point at the basal level, by comparing the structure of human and ovine hearts. The insertion point at the inferior ventricular septum shows a unique arrangement of cardiomyocyte aggre- gates. An abrupt change in cardiomyocyte orientation was observed in the middle of the myocardium, delineating a triangular-shaped region present in both sheep and human hearts. The second part of the thesis focuses on the structural organization of the inter- ventricular septum. The appearance of fibrosis in the septum is a consequence of mutation of the LMNA gene. The study focuses on : • the location of an abrupt change in cardiomyocyte orientation in the septum ; • the position of focal fibrosis visible with clinical examinations such as late gadolinium enhancement. The position of fibrosis appears to be associated with the position of the abrupt change in cardiomyocyte orientation. This in-depth analysis of explanted hearts with and without LMNA gene mutation opens up new perspectives on the relation- ship between genetic alterations and structural disorders of the heart. Finally, an advanced diffusion model was used to characterize intravoxel in ovine hearts with atrial fibrillation. This innovative model was validated against a high-resolution imaging technique, demonstrating its robustness. Our results on this model show that it is possible to obtain a better description of myocardial organization.
ED Sciences Physiques et de l'Ingénieur
Study of the reliability of quantum dot-based photodiodes for near-IR imaging applications
by Ismail HAMMAD (Laboratoire de l'Intégration du Matériau au Système)
The defense will take place at 9h30 - Basilique du Sacré-Cœur – Room 4 4 rue Emile Gueymard , Grenoble
in front of the jury composed of
- Guillaume WANTZ - Professeur des universités - Bordeaux INP - Directeur de these
- Cristell MANEUX - Professeur des universités - Université de Bordeaux - Examinateur
- Jérôme VAILLANT - Directeur de recherche - CEA Leti - Examinateur
- Yvan BONNASSIEUX - Professeur des universités - Ecole Polytechnique - Rapporteur
- Alain BRAVAIX - Professeur des universités - ISEN - Rapporteur
Quantum Dot (QD)-based light sensors hold significant potential for various imaging applications due to their high quantum efficiency, low cost, and wide absorption spectral range. These sensors can selectively absorb specific wavelengths of light, making them ideal for next-generation imaging systems for face recognition. This study focuses on a QD-based camera system operating in the near-infrared (NIR) region. By emitting light at a wavelength of 940 nm towards the face, the sensor captures high-quality images from the reflected light without interference from ambient light, as sunlight at this wavelength is absorbed by atmospheric water vapor. Despite these advantages, the relatively lower reliability of QD-based sensors compared to silicon-based technologies limits their commercial viability. Therefore, this research aims to optimize the sensor manufacturing process and conduct a comprehensive study of reliability failure modes and physical mechanisms under stress factors such as electrical biasing and light intensity. The process optimization of the QD-based sensor involves three main approaches: enhancing the molybdenum oxide (MoOx) layer at the top electrode, refining the aluminum oxide (Al2O3) buffer layer at the top electrode, and improving surface passivation in the Quantum Film (QF). The bi-layer process consists of two layers: an oxygen-rich layer and an oxygen-deficient layer of MoOx. The inclusion of the oxygen-deficient layer is crucial for enhancing reliability by limiting oxygen diffusion into the QF. Additionally, it has been determined that a 14-cycle Al2O3 buffer layer offers the best balance of device performance, both initially and after stress, in terms of quantum efficiency, dark current, and operating bias. Furthermore, improving the QD surface passivator significantly reduces deep trap density and increases charge carrier mobility, thereby maintaining a low level of quantum efficiency degradation over time under stress. It has been demonstrated that the degradation of the QD-based photodiodes under continuous (DC) light and bias stress is primarily due to the accumulation of non-extracted holes at the top electrode, which increases extraction barriers and reduces photocurrent. The extent of this degradation is directly proportional to the irradiance level and is aggravated by high bias within the I(V) plateau. Conversely, low bias operation significantly reduces output photocurrent due to strong recombination current. The study reveals that the QF can be recovered from photocurrent degradation through alternating bias and/or irradiance conditions. Utilizing recombination current under alternating bias conditions can reduce photocurrent degradation by over 94% at a 60-fps operating frequency. Alternating irradiance conditions result in a 38% reduction, while combining both methods achieves over 97% reduction compared to direct stress conditions.
Developing a Circular Decision-Aid Tool Based on Technical and Consumer Behaviour Perspectives: Application to the Sports Industry
by Nicole Sofia ROHSIG LOPEZ (ESTIA Recherche)
The defense will take place at 14h30 - Amphi 300 ESTIA Berri, 90 All. Faust d'Elhuyard, 64210 Bidart
in front of the jury composed of
- Jérémy LEGARDEUR - Professeur - École supérieure des technologies industrielles avancées (ESTIA) - Université de Bordeaux - Directeur de these
- Tatiana REYES - Professeur - École nationale supérieure d'Arts et Métiers (ENSAM) - Rapporteur
- Jenny FAUCHEU - Professeur - Mines Saint-Etienne, LGF UMR5307 - Examinateur
- Flore VALLET - Enseignante-chercheuse HDR - Pôle Universitaire Léonard de Vinci - DVRC - Rapporteur
- Damien SAUMUREAU - Réprésentant de l'entreprise CIFRE - Decathlon - Examinateur
- Daniela Cristina ANTELMI PIGOSSO - Full professor - Technical University of Denmark - Examinateur
This CIFRE thesis was done in partnership with Decathlon, particularly in the Watersports Center in Hendaye, where they develop gear for aquatic sports. This thesis aims to explore the transition of the company to the circular economy, an industrial system that replaces the linear logic of “extract- produce-use-throw away”. This system proposes closing the material loops to extract their maximum embedded value, resulting in the elimination of waste through the superior design of materials, products, systems, and business models (Ellen MacArthur Foundation, 2013). In a press release from March 2024, Decathlon positioned the development of Circular Business Models at the core of its strategy to achieve a 20 % reduction in absolute CO2 emissions by 2026 and a 42 % reduction in absolute CO2 emissions by 2030 and net zero by 2050. Circular Business Models (CBM) involve cycling, extending, intensifying, and/or dematerialising material and energy loops to reduce resource inputs, waste, and emission leakage (Geissdoerfer et al. , 2017). In this context, the question that guided the beginning of our research emerges: How can we help develop circular business models in the sports industry, given its diverse nature of products? After mapping 154 internal CBM projects, project leaders mentioned challenges such lack of strong governance and a structured circular network to facilitate the progression of circular projects, besides the difficulty of engaging consumers to adopt circular solutions. This motivated us to explore what factors could influence consumer behaviour towards CBMs, whether internal or external. We interviewed 60 aquatic sports practitioners to identify internal factors (e.g., economic, environmental, time and effort, aesthetics) and external factors (e.g. access to circular solutions, prices, product condition). Following this step, we launched a survey with 1735 respondents to measure the consumer interest in different CBMs (repair, second-hand, short-term rental, subscription, end-of-life alternatives) regarding specific product natures (protective equipment, first-layer textile, second-layer textile, budget and premium shoes, accessories, and bulky equipment) for certain sports (swimming, soccer, cycling, hiking, fitness, and running). Building on these results and the literature findings, we created a tool to help sports design teams identify suitable CBM for their products and get recommendations on how to improve circularity, considering product characteristics and customer behaviour. The tool was tested and approved by product managers, especially for beginners, regarding circular economy adoption. Our contribution relies on in the creation of an interactive decision-aid tool that is easy to use, enabling a better understanding of how to apply circular economy considering both technical and behavioural aspects. Future works could explore the adaptation of the tool for other industries, as well as the understanding of the acceptance of circularity by consumers from other cultures outside France.
Description and modeling of the damage to a ceramic matrix composite under thermomechanical stresses
by Anthony VASSALIÉ (Laboratoire des Composites ThermoStructuraux)
The defense will take place at 14h00 - Amphithéâtre Laboratoire des Composites Thermostructuraux 3 allée de la Boétie, 33600 Pessac
in front of the jury composed of
- Guillaume COUEGNAT - Ingénieur de recherche - Université de Bordeaux - Directeur de these
- Christophe BOUVET - Professeur des universités - ISAE-SUPAERO - Rapporteur
- Frédéric LAURIN - Ingénieur de recherche - ONERA - Rapporteur
- Emmanuel BARANGER - Directeur de recherche - ENS Paris-Saclay - Examinateur
- Delphine BRANCHERIE - Professeure - Université de technologie de Compiègne - Examinateur
- Anita CATAPANO-MONTEMURRO - Professeure - Bordeaux INP - Examinateur
- Sébastien DENNEULIN - Ingénieur - Safran Ceramics - Examinateur
Ceramic matrix composites (CMCs) are materials of interest in the field of aeronautic because of their exceptional mechanical properties at elevated temperatures, making them promising candidates to replace metal alloys in high-temperature components of aircraft engines. Nevertheless, these materials also exhibit a complex behavior, especially because they are multi-scale, architectured and heterogeneous. In this context, this work tends to improve the understanding of the mechanical behavior under tension of CMCs composed of fibers and matrix made of silicon carbide, with a Melt Infiltration process (named SiC/SiC MI). To better understand the effects of microscopic phases on the macroscopic behavior until the final failure of the material, two distinct but complementary axis are explored : the mechanical characterizing of the damage of these CMCs and their modelling with a finite element method. Firstly, multi-instrumented tensile tests are carried out (acoustic emissions, digital image correlation, microscope, etc.), to obtain a better description of the phenomenon at micro-scale and their effects on upper scales. Post-mortem characterization are also performed in order to quantify the properties of the microscopic phases, which are of great interest to develop the numerical model. Thus, a damage scenario until the final failure is proposed for SiC/SiC MI materials. In a second part, a genuine finite element model approach, with embedded fiber, is proposed to simulate the mechanical behavior of these materials. Based on experimental observations, mechanisms of interest at micro-scale are selected and implemented in the model directly at upper scales. The developed approach demonstrates the ability to capture both the main damage phenomenon at micro-scale and the meso-scale behavior of CMCs, in good agreement with experimental results, offering a valuable tool for understanding and predicting their mechanical behavior until the final failure, and paving the way for further developments.
ED Sciences et environnements
Personal ornaments analysis to explore the cultural and social diversity in Europe during the Gravettian
by Jack BAKER (De la Préhistoire à l'Actuel : Culture, Environnement, Anthropologie)
The defense will take place at 14h00 - Amphithéâtre 1 Université de Bordeaux Bâtiment A9 33400 TALENCE
in front of the jury composed of
- Francesco D'ERRICO - Directeur de recherche - Université de Bordeaux - Directeur de these
- Solange RIGAUD - Directeur de recherche - Université de Bordeaux - CoDirecteur de these
- Nicholas CONARD - Professeur - University of Tübingen - Rapporteur
- Paul PETTITT - Professeur - University of Durham - Rapporteur
- Sibylle WOLF - Docteur - University of Tübingen - Examinateur
- Jacques JAUBERT - Professeur - Université de Bordeaux - Examinateur
The Gravettian (34–24 ka) is widely considered as the final Pan-European technocomplex before the regional fragmentation of the population following the Last Glacial Maxima. Personal ornaments have been shown to be powerful indicators of social status and cultural affiliation. Hitherto, the ubiquitous personal ornaments found in occupation and burial sites characterising the Gravettian have yet to be the subject of a comprehensive study. The primary aim of the PhD was to document the variability in bead-type associations and identify the mechanisms driving this diversity at both regional and European scales during the Gravettian period. Achieving this paved the way for the second aim: investigating the cultural geography of Gravettian communities. We first provide an in-depth analysis of the numerous personal ornaments coming from a key Gravettian funerary site, Cro-Magnon (Dordogne, France). Subsequently, we created a representative georeferenced bead database of Gravettian personal ornaments encompassing 164 types coming from over 130 sites across Europe and analyse it using multivariate and spatial statistical methods, such as principal coordinates analysis (PCoA), Neighbour-joining, Neighbour-net, seriation and Mantel correlations and correlograms. We then proceeded to compare and contrast the Gravettian personal ornaments with those coming from the preceding Aurignacian using similar analyses in addition to k-means clustering, perMANOVA and Archaeological Similarity Networks to investigate whether continuity existed between these two technocomplexes. Analysis of the personal ornaments found at Cro-Magnon revealed the existence of extensive exchange networks across the continent. Despite sharing similarities with ornaments from other nearby groups in Dordogne, the Cro-Magnon ornaments exhibit a distinctiveness, i.e., a small, rather than large, number of decorated ivory pendants and a large, rather than small, number of shell ornaments, that highlights this people's desire to assert their unique identity within a broader symbolic context. The recalibration of the only available radiocarbon date for this site suggests that a more extensive dating campaign is necessary to chronologically attribute this iconic site accurately. The analysis of the European-scale Gravettian database reveals that this technocomplex was split into nine groups who wore different bead-type associations which were organized in an east-west cline across Europe. Whereas Gravettian groups from the east of Europe wore personal ornaments predominantly fashioned from ivory, stone and mammal carnivore teeth, groups from the west tended to wear beads made from marine shells and mammal herbivore teeth. The observed differences in bead-type associations were shown to not be solely due to Isolation-by-Distance. From this we concluded that a sense of cultural belonging dictated the personal ornament types different groups of Gravettian people wore. Burial and occupation sites were characterised by distinct patterns of personal ornament associations. The observed difference between burial groups was higher than the difference between occupation groups. The comparison of the Gravettian and Aurignacian databases unveiled stark similarities in terms of personal ornament choices between the two technocomplexes. The Gravettian was characterised by regions of similar personal ornament associations which had over ten times the surface area and which were more interconnected than those of the Aurignacian. Personal ornaments types fully carved out of osseous and lithic material better marked the cultural divide between these two technocomplexes than those produced from minimally modified natural forms.