ED Sciences Chimiques
Rational Design of Pyrazine-Based Magnetic Materials via a Molecular Building Block Approach
by Katia DUJARRIC (Centre de Recherche Paul Pascal)
The defense will take place at 10h00 - Amphithéâtre Centre de Recherche Paul Pascal UMR 5031 / CNRS-Université de Bordeaux, 115 avenue du Dr Albert Schweitzer, 33600 Pessac, France.
in front of the jury composed of
- Corine MATHONIERE - Professeure des universités - Université de Bordeaux, Centre de Recherche Paul Pascal - Directeur de these
- Dominique LUNEAU - Professeur - Laboratoire des Multimatériaux et Interfaces (UMR 5615), Université Claude Bernard Lyon 1 - Rapporteur
- Leoni BARRIOS MORENO - Professor - Laboratory of Molecular Design (LabMolDesign), University of Barcelona - Examinateur
- Céline PICHON - Chargée de recherche - Laboratoire de Chimie de Coordination (LCC) - UPR 8241 - Rapporteur
- Cécile ZAKRI - Professeure des universités - Université de Bordeaux, Centre de Recherche Paul Pascal - Examinateur
This thesis is devoted to the exploration of different synthetic approaches to rationally prepare systems of different dimensionalities based on the redox-active pyrazine ligand. In particular, a building block approach employing solution chemistry is discussed. Chapter I presents the theoretical definitions of magnetism, electrical conductivity, and X-ray absorption spectroscopy, which are crucial for understanding the experimental results. After that, state-of-the-art molecule-based materials composed of organic radical ligands, which feature high critical temperatures and, for some, conducting properties, are introduced. Additionally, the building block approach and emblematic molecule-based magnetic materials obtained through this synthetic route, ranging from cornerstone systems to modern molecular magnetism systems, are discussed. Chapter II focuses on exploring a building approach that utilizes mononuclear systems as precursors to synthesize and enhance the physical properties of previously reported square Cr-pyrazine two-dimensional networks. Moreover, it examines how this approach can be applied to other metal ions to create new magnetic two-dimensional networks and investigates the effects of these modifications on the resulting physical properties. Chapter III illustrates the use of solution coordination chemistry in the obtention of two new Cr-pyrazine two-dimensional magnetic systems. It highlights the crucial role of the synthetic choice in the design and physical properties of the final compounds. As well, it discusses how the peripheral ligands affect the electronic distribution of the pyrazines within the 2D networks. Finally, Chapter IV explores the use of a mononuclear precursor, introduced in Chapter II, to synthesise four new Cr one-dimensional materials featuring either neutral pyrazines or radical pyrazines. It discusses in particular, the impact of the different peripheral ligands on the redox process of such compounds.
ED Sciences de la Vie et de la Santé
Study of the role of G1/S transition on selection of a simple multicellular form in Saccharomyces cerevisiae.
by Tom DUCROCQ (Institut de Biochimie et Génétique Cellulaires)
The defense will take place at 14h00 - Salle de conférence de l'IBGC Institut de Biochimie et Génétique Cellulaires (IBGC) - UMR 5095 - 1 rue Camille Saint Saëns, CS61390 - 33077 Bordeaux cedex, France
in front of the jury composed of
- Thierry NOëL - Professeur - Université de Bordeaux, Laboratoire de Microbiologie Fondamentale et Pathogénicité - Examinateur
- Cécile FAIRHEAD - Professeure - Université Paris-Saclay; GQE-Le Moulon, IDEEV - Rapporteur
- Hélène MARTIN-YKEN - Chargée de recherche - Toulouse Biotechnology Institute, INSA Toulouse, Université de Toulouse - Rapporteur
- Fridolin GROSS - Maître de conférences - Université de Bordeaux, ImmunoConcept - Examinateur
Multicellularity is present throughout the entire tree of life. It has appeared and has been fixed in the tree of life at least 25 times independently in evolution history. The formation of multicellular entities can be explained by simple mechanisms, either by clonal development or by aggregation of cells. However, it is not fully understood how these simple multicellular forms could be maintained or even selected. Multiple phenomena have been assumed to drive the selection of simple forms of multicellularity, but few experimental work has already tested those hypotheses. The Snowflake is a multicellular phenotype of Saccharomyces cerevisiae, genetically controllable in the laboratory by disrupting the ACE2 gene. This gene encodes a transcription factor that activates the enzymes that degrade a part of the cell wall known as the parietal septum at the end of mitosis, ensuring the physical separation of mother and daughter cells. This Snowflake phenotype associated with the ace2 mutation can be used in the laboratory to test the potential selective drivers of multicellularity, notably by carrying out competition experiments in co-culture with single-cell strains ACE2. My thesis work investigated the potential role of the genetic context of the G1/S cell cycle transition on the selection of the multicellular Snowflake form, focusing on the importance of the CLN3 and WHI5 genes. My results show that deletion of the CLN3 gene or overexpression of the WHI5 gene allows the selection of Snowflake ace2, at both phenotypic and genotypic levels. I have also shown that this selection is explained by a faster exit from stationary phase in the ace2 Snowflake context, and that this is not dependent on the multicellular phenotype, but rather on the ace2 genotype itself. Furthermore, my results show that this selective advantage in the cln3 context depends on the KSS1 gene, another target of the Ace2 transcription factor. Altogether, my results support the hypothesis that in some cases multicellularity could be selected not by conferring a selective advantage specific to the multicellularity itself, but rather as a passenger phenotype.
ED Sciences Physiques et de l'Ingénieur
Behavioral analysis of clayey subgrade soils under drought conditions
by Mohamed Amine ES-SOUFI (I2M - Institut de Mécanique et d'Ingénierie de Bordeaux)
The defense will take place at 14h00 - Amphi3 351 Cr de la Libération, Bâtiment A9, 33400, Talence
in front of the jury composed of
- Nadia SAIYOURI - Professeure des universités - Université de Bordeaux - Directeur de these
- Said TAIBI - Professeur des universités - Université Le Havre Normandie - Rapporteur
- Pierre BREUL - Professeur des universités - Université Clermont Auvergne - Rapporteur
- Mahdia HATTAB - Professeure des universités - Université de Lorraine - Examinateur
- Lamine IGHIL AMEUR - Docteur - GéoCoD - Cerema Normandie-Centre - Examinateur
- Lamis MAKKI - Docteure - Université Gustave Eiffel - Examinateur
The swelling–shrinkage behavior of clayey soils represents a major challenge for the durability of road infrastructures, particularly in France where nearly half of the territory is exposed to this geotechnical risk. These soils, which are highly sensitive to moisture variations, undergo cycles of drying and rewetting that induce shrinkage, swelling, and cracking, thereby weakening pavements and generating high maintenance costs. This thesis aims to experimentally and multi-scalely analyze the hydro-mechanical behavior of different clayey soils subjected to these cycles, and to evaluate the effectiveness of an innovative stabilization technique implemented via nano-silica injection. The study focused on two natural soils sampled beneath road pavements (Sarlat and Esnandes), representative of in situ clays, as well as two reference model clays: Bentonite, which is highly swelling, and Kaolinite, which is non-swelling. The choice of these model clays is supported by abundant literature, enabling comparison of our results with existing data and facilitating interpretation of the observed mechanisms. It also allowed positioning the behavior of the natural soils relative to these extreme materials, providing a comparative basis to assess their sensitivity to moisture cycles. The experimental program included characterizing the physico-chemical properties of the soils (water content, plasticity, particle size distribution), quantifying their shrinkage and swelling under drying and wetting cycles, observing the initiation and evolution of surface cracks via Digital Image Correlation (DIC), analyzing their microstructural, mineralogical, and pore characteristics (SEM, XRD, mercury intrusion porosimetry, X-ray tomography), studying the effects of nano-silica on microstructural reinforcement, void filling, and deformation limitation, and finally assessing the environmental stability of this treatment through leaching tests. Results show that shrinkage deformations are strongly correlated with soil mineralogy, with higher linear shrinkage observed in Bentonite and Esnandes. These swelling soils also exhibited slower drying kinetics due to their high water retention capacity linked to montmorillonite content. Crack monitoring via DIC revealed the appearance of cracks before complete desaturation of the samples. Bentonite and Esnandes, both rich in montmorillonite, showed higher crack density and wider cracks, indicating their strong susceptibility to moisture variations. In contrast, Sarlat and Kaolinite exhibited limited cracking, consistent with their lower plasticity and kaolinite-dominated mineralogy. Under drying–wetting cycles, Bentonite and Esnandes showed greater shrinkage–swelling deformations than Kaolinite and Sarlat, although deformation amplitudes progressively stabilized after two cycles, reflecting structural adaptation and cumulative compaction for the natural soils. Nano-silica treatment (LEVASIL CS30-324 P) had a significant effect: SEM observations showed partial void filling and the formation of flocculated aggregates with 10% nano-silica, indicating microstructural rearrangement and improved cohesion. Shrinkage–swelling tests revealed that adding 20% nano-silica reduced shrinkage and swelling deformations by up to 45–55% during the first cycle, with the stabilizing effect gradually decreasing over subsequent cycles due to natural soil compaction. Interestingly, effectiveness was sometimes greater with 4% than with 10%, likely due to dispersion efficiency and partial saturation of adsorption sites.
ED Sciences et environnements
Fate and effects of microplastics, nanoplastics and additives resulting from the degradation of fishing gear during their life cycle. Study in the Bay of Biscay
by Edgar DUSACRE (Environnements et Paléoenvironnements Océaniques et Continentaux)
The defense will take place at 14h00 - Amphitéâtre IECB IECB, 2 Rue Robert Escarpit, 33600 Pessac
in front of the jury composed of
- Magalie BAUDRIMONT - Professeure des universités - Université de Bordeaux - Examinateur
- Ika PAUL-PONT - Directrice de recherche - European University Institute of the Sea/Université de Bretagne Occidentale - Examinateur
- Juan Antonio MARIGOMEZ ALLENDE - Professeur des universités - Universidad del Pais Vasco/Euskal Herriko Unibertsitatea - Examinateur
- Mohamed BANNI - Professeur des universités - University of Sousse - Rapporteur
- Lúcia Maria DAS CANDEIAS GUILHERMINO - Professeure des universités - University of Porto - Rapporteur
Fishing activities account for 17% of human consumption of animal proteins and approximately 550 million individuals globally rely for their livelihoods. On the other hand, this sector, could also play a role in marine pollution due to the use of plastic fishing gear (FG). However, scientific studies on how plastic FG contribute to the global oceanic pollution of microplastics (MPs), nanoplastics (NPs) and plastic chemicals were scarce. In this context, operated and lost fishing nets (FNs) in the Southeastern Bay of Biscay were estimated and beached abandoned lost or otherwise discarded fishing gear (ALDFG) were quantified. Then 6 oil-based FNs (1 made of polyethylene-polypropylene (PE-PP) and 5 made of polyamide (PA)) and 2 partially biobased/biodegradable FNs (polybutylene succinate-polybutyrate adipate terephthalate (PBS-PBAT)) were selected to investigate their degradation and toxicity. The degradation of FNs was analyzed through artificial aging in order to quantify the production of MPs, NPs, and plastic chemicals. Then, the effects of leachates were investigated through acute, and subchronic toxicity assays with lethal and sub-lethal endpoints on A. fischeri, T. lutea, A. tonsa and O. latipes. In addition, a comparative study of the toxicity of organic extracts from new FNs and end-of-life (EOL) ones on A. fischeri, the RTL-W1 cell line, and O. latipes was conducted. It was estimated through models that the fishing fleet of the Southeastern Bay of Biscay operated 211 tons of FG in 2023 and lost 6 tons of them. In the same period, it was also estimated that 3 tons of ALDFG were beached. Most of the FG beached were mending pieces coming from trawl and bottom seine repairs (89.8% of the FG in items). The artificial aging (AA) of FNs revealed FN-dependent production of MPs and plastic chemicals. Production of these degradation products tended to increase with AA, although not linearly. Three of the seven FNs studied produced a significant number of fragment MPs after 25 days of AA (1.1x105 MP/g of FN to 6.8x105 MP/g of FN) with a median size of 21.25 µm (min-max: 5 – 430 µm). NPs (< 1 µm) were also identified in the leachates of all FNs. Significant amounts of six heavy metals (Cu, Fe, Pb, Zn, Ni, Ag) were quantified in the leachates. Furthermore, we identified 27 organic compounds. Concerning the comparative toxicity of DMSO extracts of new and EOL FNs, the three species studied were affected by most of the leached products from the FNs. The Bioluminescence inhibition of A. fischery was linked to trace metals. Each of the 4 species exposed to leachates of artificially aged FNs experienced varying degrees of effects. The bioluminescence inhibition of A. fischeri was significantly impacted by most FNs, but more especially by the PBS-PBAT ones. This bioluminescence inhibition was mainly related to the release of trace metals. The density of microalgae cells (T. lutea) was not significantly affected after 72 h of exposure. Most tested FNs significantly disrupted the heart rate and behavior of Japanese Medaka larvae. Alterations in behavior generally increased with FN aging time and was mainly related to the release of organic chemicals. The survival of adult and juvenile copepods was significantly decreased by most of the FNs. The lowest LC50 estimated was caused by one PA FN (1.32±1.14 g/L) and one PBS-PBAT FN (1.55±0.82 g/L). Subchronic exposure of copepods caused significant effects on egg production and hatching success. Globally, these results highlighted that FNs contribute to MP (1.48 ± 1.34 MP/m3 to 2.2 ± 4.76 MPs/m3), NP and plastic chemical pollution of the oceans. Biobased/biodegradable FNs could offer a solution to better manage EOL FG and to reduce ghost fishing when lost, but their current composition needs to be improved to reduce their toxicity.