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Développées depuis la nuit des temps, les mathématiques façonnent notre vie quotidienne et développent des outils pour le futur. Au cœur des sciences dures, telles que la physique, la chimie ou la biologie, les mathématiques jouent un rôle primordial dans un grand nombre de problèmes appliqués, que ce soit en informatique et en télécommunication, à travers les mathématiques discrètes et l’algorithmique, en météorologie et dans le domaine spatial, à travers la théorie de systèmes dynamiques, ou en finance et dans l’actuariat, à travers les probabilités et les processus stochastiques. 

Apprenez à répondre aux défis sociaux et environnementaux de notre société pour acquérir une démarche scientifique tournée vers l’avenir et vers la résolution d’enjeux de société !

Depuis la découverte du feu durant la Préhistoire l’être humain n’a cessé de s’intéresser à la matière, à ses propriétés et à ses changements naturels ou induits par ses soins. Aujourd’hui nommés « chimistes », les spécialistes de la réactivité de la matière poursuivent l’art des expériences et des découvertes. Les produits de leurs connaissances essentielles s’appliquent dans les domaines de la nutrition, la santé, l’hygiène, les transports, le sport, la construction et la protection de l’environnement. 

Résumé Head and neck squamous cell carcinoma (HNSCC) is a heterogeneous malignancy in which human papillomavirus (HPV) status strongly influences therapeutic response. HPV+ tumors generally show greater sensitivity to treatment, whereas HPV- tumors are associated with poorer prognosis and increased resistance. This thesis investigated how HPV status shapes cellular adaptation to therapeutic stress, with a particular focus on therapy-induced senescence (TIS), autophagy and MMS19.HPV- HNSCC cells developed a senescence-like phenotype following cisplatin or x-ray irradiation, whereas HPV+ cells showed limited induction. Silencing of the viral oncogenes E6 and E7 in HPV+ cells increased this phenotype, indicating that HPV actively modulates treatment-induced cellular responses. Proteomic analyses further identified autophagy- and lysosome-related pathways as major features distinguishing HPV- from HPV+ cells. Autophagy inhibition predominantly impaired proliferation and clonogenic survival in HPV- cells, supporting an HPV-dependent autophagy–senescence axis involved in treatment adaptation.The second part of this thesis identified MMS19, a component of the cytosolic iron–sulfur cluster assembly machinery, as a potential determinant of HPV- HNSCC resistance. MMS19 was associated with poorer clinical outcome, while its silencing impaired proliferation and clonogenic survival, particularly in HPV- cells.Together, these findings identify autophagy-dependent remodeling and MMS19-associated genome maintenance as potential vulnerabilities contributing to therapeutic resistance in HPV- HNSCC. Jury Prof. Anne-Catherine HEUSKIN (UNamur), PrésidenteProf. Carine MICHIELS (UNamur), SecrétaireProf. Francis RODIER (UMontreal)Prof. Yves POUMAY (UNamur)Prof. Anabelle DECOTTIGNIES (UCLouvain)Prof. Marc THERRIEN (UMontreal)Prof. Sue YOM (UCSF)

La biologie est la science du vivant.  De la cellule à l’écosystème, elle étudie toutes les formes de vie. Elle est essentielle pour comprendre les questions sociétales complexes qui touchent à l’environnement, à la santé et au développement durable. 

La physique, une aventure de l’intelligence. De l’infiniment petit à l’infiniment grand, des particules élémentaires aux galaxies, vous avez soif de comprendre le pourquoi et le comment des phénomènes naturels que vous observez ?  Pourquoi le ciel est-il bleu ? Comment décolle un avion ? Comment soigner par radiations ?  Quels sont les effets du réchauffement climatique ? Comment les nanotechnologies peuvent-elles révolutionner les télécommunications ? Comment produire de l’énergie sans épuiser la planète ?La physique répond à toutes vos questions. 

RésuméIn this work, I aimed at simulating accurately the Raman optical activity (ROA) signatures of flexible solute molecules in their environment. Indeed, these systems are quite challenging due to potentially huge number of conformers, i.e. local minimum on the potential energy surface (PES). Moreover, the environment can drastically change the PES which can be observed on the experimental ROA spectra that vary quite a lot with the conformation of the molecule and its surroundings. In order to tackle this issue, we have designed a hierarchy of methodology named M1, M2, M3. In M1 and M2, the so-called static approach is used: one or more conformers are found, their geometry are reoptimized at the Density Functional Theory (DFT) level, and their vibrational signatures are simulated, usually at the harmonic approximation. The initial list of conformers was obtained by using the CREST algorithm. In M1, the solvent is considered implicitly while in M2, explicit solvent molecules are added around the solute molecule. In M3, we perform an ab-initio molecular dynamics of the solute molecule surrounded by explicit solvent molecules. The spectrum is obtained by evaluation time-correlation functions along the trajectory. Our first systems of interest were cryptophane derivatives. They are flexible cage-like systems made of two hemispheres connected by three -O-(CH2)n-O- (denoted Cr–nnn) linkers that exhibit chiroptical properties. For Cr–111, the smallest cryptophane possible, M1 methodology gave a good agreement with respect to experiment, especially in the fingerprint region. However, we have demonstrated that the relative ratio between the different conformers was strongly impacted by the choice of the exchange-correlation (XC) functional in our DFT calculations demonstrating the sensibility of the description of the PES. Cr–222 molecules have shown to be more flexible, as demonstrated by a greater number of significant conformers. The overall agreement with experiment was also satisfactory. Finally, to test our different approaches (M1-M3), I have performed new ROA measurements of amino acids in water at the University of Bordeaux in the lab of Dr. Daugey. When compared to our simulations, we have clearly seen an improvement on the ROA signatures when explicit water molecules are added in our simulations (M2 vs M1). Unfortunately, M3 method did not perform as expected and further investigations are needed. Overall, I have shown that the PES as described by our various methodologies is very sensitive to various parameters of the simulation such as the XC functional, the number and position of explicit solvent molecules, … and that all these impact strongly the simulated ROA signatures.JuryProf. Francesca CECCHET (UNamur), PrésidenteProf. Vincent LIÉGEOIS (UNamur), SecrétaireProf. Benoît CHAMPAGNE (UNamur)Prof. Carine CLAVAGUÉRA (Université Paris-Saclay)Dr Nicolas DAUGEY (Université de Bordeaux)

RésuméEnvironmental change rarely arrives as a single, isolated event; organisms and communities typically experience one stressor against the backdrop of another already passed. Arunima Sikder's doctoral thesis asks whether an organism's past environment shapes its response to the environment that follows, and whether that influence propagates upward to affect the stability of the communities these organisms belong to.The thesis addresses this question in Synechococcus sp., a globally significant marine primary producer, using thermal and chemical stressors as its two environmental drivers. Working across three levels of biological organisation, the work accounts for how past environments shape responses to subsequent ones arriving in sequence, in fluctuation, or in combination — with functional traits as the common currency for measuring these responses.The results show three things. First, sensitivity to a stressor depends on the sequence of exposure, not on the stressor alone. Second, response diversity predicts community stability only when measured under the community's actual acclimation history, rather than under sustained conditions as convention assumes. Third, an apparent contradiction of biodiversity–ecosystem-function theory — a negative relationship between functional diversity and performance.Together, these findings argue that sensitivity, response diversity, and functional diversity should be treated as state-dependent quantities rather than fixed properties, with consequences for how the performance of biological systems is measured and modelled under increasingly variable environmental regimes.JuryProf. Alice DENNIS (UNamur), PrésidenteProf. Frederik DE LAENDER (UNamur), SecrétaireProf. Maren STRIEBEL (Carl-von-Ossietzky University Oldenburg)Prof. Giulia GHEDINI (Monash University)Prof. Eli THORÉ (UNamur)

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