Résultats de recherche

ECOBAT est un projet EOS (FNRS/FWO) qui réunit quatre universités : l’UCLouvain, la KULeuven, l’Université de Bonn (Allemagne), ainsi que l’Université de Namur.  Ce consortium mobilise actuellement une vingtaine de chercheurs de tous niveaux (master, doctorants, post-doctorants, promoteurs), dont le docteur Pierre Beaujean, sous la supervision du Professeur Benoît Champagne.

À l'occasion de la 30e édition du Festival International Nature de Namur (FINN), l'Université de Namur, partenaire de cet événement, réaffirme son engagement pour la sensibilisation environnementale en associant sciences et art. Avec son stand immersif au village nature implanté à la citadelle et la participation de ses experts aux débats écologiques du Focus Environnement, l'Université de Namur offre un regard novateur sur la nature à travers l’enseignement. Par ailleurs, un jury d'étudiants du master en cultures et pensées cinématographiques a remis le Prix de l’Environnement lors du Gala des films professionnels.

Jury Prof. Catherine MICHAUX (UNamur), PrésidenteProf. Yoann OLIVIER (UNamur), secrétaireProf. Piotr DE SILVA (Technical University of Denmark)Prof. Daniel ESCUDERO MASA (KULeuven)Prof. Benoît CHAMPAGNE (UNamur)Prof. Luc HENRARD (UNamur) Abstract Organic Light Emitting Diodes (OLEDs) are now a well-established technology in modern electronic devices, from flexible TV screens to lighting applications. Each time we use our smartphone, billions of tiny molecules are electrically stimulated to emit the colorful light reaching our eyes. The ability of these molecules to convert electricity into light is the core principle of an OLED, and understanding the mechanisms behind this process can help improve their performance.Recently, two new families of triangular-shaped organic molecular systems, known as Multi-Resonant (MR) and Inverted Singlet-Triplet (INVEST) compounds, have shown promising features for OLED applications.In my PhD research, I used computational chemistry to explore the quantum mechanical effects that define the peculiar features of these systems.The first part of my thesis focused on identifying the correct computational protocol to properly describe the energy and nature of the singlet and triplet excited states of the INVEST compounds, highlighting the importance of methods including double excitations.  With this information in our hands, we combined quantum chemistry and group theory to design new light-emitting INVEST compounds. Finally, we applied both static and dynamic approaches to describe the spin conversion processes in MR and INVEST systems, providing a comprehensive picture of their electronic and photophysical properties for next generation OLED applications.

Jury Prof. Xavier DE BOLLE (UNamur), présidentProf. Jean-Yves MATROULE (UNamur) secrétaireDr Karrera DJOKO (Durham University)Dr Soufian OUCHANE (Paris-Saclay University)Dr Rob VAN HOUDT (SCK-CEN) Abstract The copper tolerance of the free-living bacteria Caulobacter crescentus depends on its dimorphic cell cycle. The sessile stalked cell detoxifies and effluxes copper through the multicopper oxidase PcoA and the Cu transporter PcoB respectively, while the swarmer cell senses and swims away from Cu sources. The transcriptional landscape of both morphotypes upon copper excess further confirms this. Among the few genes upregulated in both stalked and swarmer cells under copper excess, the CCNA_00027-00028 operon encodes a TonB-dependent receptor (TbcT) and a 2-oxoglutarate/Fe2+-dependent oxygenase (OxcT), respectively. The deletion of these two genes specifically increases the sensitivity towards Cu in C. crescentus. Interestingly, using a bioinformatics approach, we observed that the tbcT and oxcT genes co-occur in at least 67 % of bacteria containing a tbcT gene, and 88 % of bacteria containing an oxcT gene. The TbcT-OxcT system is not involved in the transport of copper nor the detoxification of copper-induced oxidative stress. Previous studies in C. crescentus and for homologous proteins showed that TbcT seems to be involved in iron import via siderophores, even though C. crescentus does not appear to synthesize siderophores. The overexpression of the tbcT gene appears to enhance the import of iron. OxcT activity is important for copper tolerance, although its specific activity has not yet been deciphered. Based on our results, we demonstrated that proper iron import is crucial for complete Cu tolerance, with the intracellular iron preventing copper accumulation. Taken together, our results argue for a tight coupling between iron and copper homeostasis in the context of copper tolerance. 

Lors du 12ème congrès international des matériaux mésostructurés (IMMA) qui a eu lieu du 8 au 12 juillet à Montpellier, le Prof. Bao-Lian Su a été réélu président de l'Association internationale des matériaux mésostructurés (IMMA). 

Programme 8:50 | Welcome, registration, and poster setup9:20 | Welcome speechFirst morning session 9:30 | Vladimir N. Uversky - University of South Florida, USA - "Dancing protein clouds: strange biology and chaotic physics of intrinsically disordered proteins" 10:15 | Marie Skepö - Lunds Universitet, Sweden - "Structural and conformation properties of IDPs: computer simulations in combination with experiments"       11:00 | Coffee breakSecond morning session11:30 | Peter Tompa - Vrije Universiteit Brussel, Belgium - "Fuzzy interactions of IDPs driving biomolecular condensation"12:15 | Sonia Longhi - Aix-Marseille Université, France - "Intrinsic disorder, phase transitions, and fibril formation by the Henipavirus V and W proteins"   13:00 | Lunch and poster sessionAfternoon session14:30 | Sigrid Milles - Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Germany - "Intrinsically disordered proteins in endocytosis: an NMR and single molecule fluorescence perspective"     15:15 | Jean-François Collet - Université Catholique de Louvain, Belgium - "How disorder controls the transport of lipoproteins in the cell envelope of Gram-negative bacteria"    16:00 | Closing speech16:10 | Networking Beer Time at "Le Chapitre"VenueUniversity of Namur, auditorium Pedro Arrupe (PA02), rue de Bruxelles, 65-67 - 5000 Namur (#21 on the campus map) Download the programme (PDF) Download the campus map Registration guidelines Registration feeStudents (PhD students included): 25 €Seniors: 40 €Payment - Bank transferPayable before 6 December on the account:Name: Université de Namur – ASBLIBAN: BE10 2500 0740 2704BIC: GEBABEBB Please mention your name/CPO4136330 /e-mail in the payment communication. Abstract guidelines Send us your abstract before 6 December by email: pdid.meeting@unamur.be Format: Word document, maximum 1 page A4, Times New Roman  Registration All deadlines (registration, payment, abstracts) : 6 December 2024

JuryProf. Francesca CECCHET (UNamur), présidenteProf. Luc HENRARD (UNamur), promoteur et secrétaireProf. Gian-Marco RIGNANESE (UCLouvain), co-promoteur Prof. Vincent LIEGEOIS (UNamur)Prof. Xavier GONZE (UCLouvain) Prof. Humbert BERNARD (Université de Nantes)AbstractSensing technologies are critical across scientific, industrial, and medical domains, enabling the detection and analysis of various (bio)chemicals. Vibrational spectroscopies, such as Raman spectroscopy and infrared absorption spectroscopy, offer powerful and non-destructive means to characterize these molecular structures and their interactions. However, their application is often limited by inherently small cross-sections, curbing the analysis of low concentration. Surface-enhanced vibrational spectroscopies (SEVS), including surface-enhanced Raman scattering (SERS) and surface-enhanced infrared absorption (SEIRA), address these limitations by using electromagnetic field enhancements associated with localized surface plasmon resonances (LSPR) in nanostructured metal substrates. The resonant coupling between plasmons and molecular vibrations significantly enhances spectroscopic signals, facilitating trace molecule detection and real-time chemical reaction monitoring.Despite experimental success, the theoretical understanding of SEVS remains incomplete, presenting a challenge in simulating plasmonic responses and molecular vibrational modes within a unified framework. This thesis aims to bridge this gap using a combination of Discrete Dipole Approximation (DDA) and Self-Consistent Field Hartree-Fock (SCF-HF) methods, focusing on SEIRA to complement existing SERS studies.Our work begins with isolated gold particles analysed via DDA, benchmarked against Mie theory. We then explore coupled disk systems, revealing hot spots and polarization-dependent extinction cross-sections. The study of nanorods with infrared plasmonic resonances demonstrates that the observed SEIRA effect is driven by the strong coupling between plasmon excitations and molecular vibrations, rather than by the local field response of molecules. This insight shifts the focus towards designing plasmonic systems sensitive to environmental changes rather than merely enhancing the local field.RésuméLes technologies de détection sont cruciales dans les domaines scientifique, industriel et médical, permettant la détection et l'analyse de divers produits chimiques. Les spectroscopies vibrationnelles, telles que la spectroscopie Raman et l'absorption infrarouge, offrent des moyens puissants de caractériser les structures et les interactions moléculaires. Cependant, leur application est souvent limitée par des sections efficaces intrinsèquement petites, en particulier pour les molécules à faible concentration ou dans des environnements complexes. Les spectroscopies vibrationnelles exaltées en surface (SEVS), incluant la spectroscopie Raman exaltée en surface (SERS) et l'absorption infrarouge exaltée en surface (SEIRA), répondent à ces limitations en utilisant les renforcements du champ électromagnétique associés aux résonances plasmoniques de surface localisées (LSPR) dans les substrats métalliques nanostructurés. Le couplage résonant entre les plasmons et les vibrations moléculaires améliore considérablement les signaux spectroscopiques, facilitant la détection de molécules à l'état de trace et la surveillance en temps réel des réactions chimiques.Malgré leur nombreuse preuve expérimentale, la compréhension théorique des SEVS reste incomplète, posant un défi pour la simulation des réponses plasmoniques et des modes vibratoires moléculaires dans un cadre unifié. Cette thèse vise à combler cette lacune en utilisant une combinaison de l'Approximation des Dipôles Discrets (DDA) et de la méthode deHartree-Fock (SCF-HF), en se concentrant sur le SEIRA pour compléter les études existantes sur le SERS.Notre travail commence par l'analyse de particules d'or isolées via DDA, comparées à la théorie de Mie. Nous explorons ensuite des systèmes de disques couplés, révélant des hot spots et des sections efficaces d'extinction dépendant de la polarisation. L'étude de nanorods avec des résonances plasmoniques infrarouges démontre que l'effet SEIRA observé est dû à un fort couplage entre les excitations plasmoniques et les vibrations moléculaires, plutôt qu'à la réponse au champ local des molécules. Cette découverte suggère d’orienter la conception de systèmes plasmoniques vers une sensibilité aux changements environnementaux plutôt que vers le simple renforcement du champ local. 

JuryProf. Yoann OLIVIER (UNamur), PresidentProf. Luc HENRARD (UNamur), SecretaryProf. Ken HAENEN (UHasselt)Prof. Danny VANPOUCKE (UHasselt)Prof. Paulius POBEDINSKAS (UHasselt)Prof. Rozita ROUZBAHANI (UHasselt)Prof. Audrey VALENTIN (Université Sorbonne Paris-Nord)Prof. Anke KRÜGER (Universität Stuttgart)Dr Michael SLUYDTS (ePotentia)RésuméRadical attack and recombination are thought to play an important role in the atomic-scale mechanisms driving the growth of diamond. Unfortunately, accurate ab-initio calculations of the growth mechanisms are scarce. This work presents an analysis of growth-related reactions, including the ones involving hydrogen and methyl radicals, on (100), (111) and (113) H-passivated diamond surface. The reactions investigated here include the migrations of different species. The reactions between the intermediate growth steps of the nucleation (including some etching mechanisms) are characterised through their reaction rate coefficients.The (climbing) nudged elastic band method is used to identify the minimum energy path of the reactions, which reveals either a tight or a loose transition state depending on the presence or absence of an energy barrier.  Following the determination of the energy profile a given reaction, the vibrational spectra of its reactants, products and transition state is computed to derive its reaction rate coefficient by means of (variational) transition state theory calculations. These temperature- and pressure-dependent reaction rate coefficient have great potential: using multi-scale methods (e.g. kinetic Monte-Carlo), they provide insights into the best conditions to grow single crystal diamond. Temperature, pressure and radical densities in the reactor influence both the rate and quality of the growth, and the versatility of the results presented herein allows to account for these factors. The approach used in this work can be generalised to any crystallographic orientation of diamond, and even to other semiconductor surfaces.

JuryProf. Thierry ARNOULD (UNamur), présidentProf. Benoît MUYLKENS (UNamur), secrétaireProf. Sébastien PFEFFER (Université de Strasbourg)Prof. René REZSOHAZY (UCLouvain)Prof. Catherine SADZOT (ULiège)Prof. Dr Benedikt KAUFER (Freie Universität Berlin)Prof. Carine VAN LINT (ULB)Dr Damien COUPEAU (UNamur),RésuméLes ARN existent sous diverses formes dans la cellule : les ARN messagers (ARNm), les ARN de transfert (ARNt) et ribosomaux (ARNr) et les petits ARN régulateurs (ARNsn, miARN, snoARN). Les ARN circulaires (ARNcirc) jouent également un rôle clé en servant de matrice pour la traduction, en inhibant des ARN régulateurs par interaction de séquence, ou en recrutant des protéines pour moduler leur activité.L’herpèsvirus des gallinacés, plus connu sous le nom de virus de la maladie de Marek (MDV), provoque un lymphome agressif chez le poulet, entrainant sa mort dans un délai de quelques semaines. Ceci est dû aux nombreux facteurs de virulence qu’il produit. Notamment, MDV produit un facteur de transcription, Meq, qui induit la transformation des cellules dans lesquelles le gène est exprimé. Ce projet de thèse s’intéresse à un ARNcirc dérivé de ce gène.Cette étude a d'abord identifié de nombreux ARNcirc encodés par MDV, notamment lors de la lymphomagenèse, à partir de quatre principaux locus viraux : l'OriLyt, vTR, LAT et Meq. Le développement du programme vCircTrappist a montré que des virus apparentés encodent également des ARNcirc similaires, reliant la circularisation des transcrits viraux à un mécanisme inconnu.Focalisée sur circMeq, l'étude a révélé que cet ARNcirc atténue la virulence de MDV, en contraste avec le rôle précédemment attribué à Meq. Cette conclusion repose sur l'inhibition sélective de circMeq ou de linMeq via des mutations dans le génome viral.Cette thèse a révélé des propriétés insoupçonnées du gène Meq, ouvrant la voie à des recherches futures, notamment des expériences in vivo pour explorer le rôle de circMeq dans la transmission de MDV. 

JuryProf. Alexandre MAUROY (UNamur), présidentProf. Timoteo CARLETTI (UNamur), promoteur et secrétaireProf. Malbor ASLLANI (Florida State University)Prof. Renaud LAMBIOTTE (Oxford Mathematical Institute)Prof. Filippo COLOMO (Università degli studi di Firenze)Prof. Christian WALMSLEY HAGENDORF (UCLouvain)RésuméFlocks of birds, people clapping in unison or the World Wide Web are some instances of complex systems in which a large number of entities interact with each other and produce some emergent phenomena. In this thesis, we pay special attention to two such complex systems, namely crowded random walks on networks, and domino tilings and vertex models. In recent years, networks and generalizations thereof have emerged as an efficient tool to model the pattern of interactions among a set of entities. Examples include social networks, transportation networks and ecological networks. A cornerstone of network science is the interplay between network structure and dynamics on networks. Among those dynamical processes, random walks play a central role. In the first part of this thesis, we study the dynamics of multiple random walkers moving across the nodes of the network, assuming the latter to be endowed with limited available space. We characterize, both analytically and numerically, the stationary states, and we subsequently apply the latter framework to a real ecological network. In the second part of the thesis, we move on to the study of the arctic curve phenomenon arising in domino tilings of double Aztec rectangles and configurations of the six-vertex model with partial domain wall boundary conditions. The latter two models manifest in the scaling limit a spatial phase separation between ordered regions and a central disordered region. We compute the arctic curve of the aforementioned models using the tangent method.