Résultats de recherche

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)

Les membres du Jury sont :Prof. Elisabeth LEIJNSE (Présidente), UNamurProf. Lieven VANDELANOTTE (Promoteur, Secrétaire), UNamurProf. Dirk DELABASTITA (Co-promoteur), UNamurProf. Ton HOENSELAARS (Co-promoteur), Universiteit UtrechtProf. Raphaël INGELBIEN, KU LeuvenProf. Guido LATRÉ, UCLouvainVous êtes cordialement invités à assister à cette soutenance.La proclamation sera suivie d’un drink à la Salle académique.

Coordonné par deux professeurs de l'UNamur, un ouvrage collectif rassemble les travaux de 18 chercheurs autour d'une cinquantaine d'ouvrages rares, sélectionnés parmi les plus de 900 éditions de Christophe Plantin conservées à l'Université. Soutenu par la Fondation d'utilité publique Institut Moretus Plantin, ce projet marque une première étape avant le lancement, dès septembre, d'une nouvelle recherche sur le multilinguisme et les pratiques de traduction dans les éditions de l'imprimeur anversois. 

L’Université de Stanford a publié un classement prestigieux qui met en lumière les chercheurs les plus influents dans un large éventail de domaines scientifiques. Cette liste, établie sur base de critères bibliographiques, vise à fournir un moyen normalisé d'identifier les leaders scientifiques mondiaux. Il s’agit d’un critère parmi d’autres permettant d’évaluer la qualité de la recherche scientifique. Douze chercheurs de l’Université de Namur en font partie !

Une délégation de l’Université de Namur a participé à une mission exploratoire à l’Université Cheikh Anta Diop (UCAD) de Dakar, au Sénégal. L’objectif : découvrir les recherches menées sur le terrain, rencontrer les chercheurs de l’UCAD et initier de futures collaborations entre les deux institutions. 

Contacter l'Institut ILEE PrésidentJohan YansVice-présidentFrédéric Silvestre Scientific managerCarolin MayerTel : +32 (0)81 724 373Email: ilee@unamur.be   S'affilier Si vous souhaitez vous affilier ou si vous souhaitez modifier votre affiliation, rendez-vous sur la page "affiliation aux instituts de recherche".

Contact Pour toute question : info.naltt@unamur.be Membres du comité scientifique Denis Saint-Amand (président)Hadrien Cousin (partim)Emma JoveneauVictoire Legrelle (partim)Laurence MeurantEmma-Louise SilvaLieven Vandelanotte S'affilier Si vous souhaitez vous affilier ou si vous souhaitez modifier votre affiliation, rendez-vous sur la page "affiliation aux instituts de recherche". Organisation Découvrir les membres