Résultats de recherche

Jury Prof. Nathalie BURNAY (UNamur), présidenteProf. Sabine HENRY (UNamur), secrétaireDr. Florence DE LONGUEVILLE (UNamur)Prof. Nathalie MONDAIN (Université d’Ottawa)Prof. Etienne PIGUET (Université de Neuchâtel)Prof. Sane TIDIANE (Université Assane Seck/Ziguinchor) Abstract Recent attention to environmental change has highlighted its impact on rural communities, particularly in Africa, where household-level adaptations play a crucial role in larger societal responses. Current research often overlooks these small-scale, everyday adaptations and how they evolve over time, limiting our understanding of rural communities' dynamic responses to environmental changes. This study focused on households living in rural West Africa, more specifically in the region of Saint-Louis in Senegal. To capture the complexity of the household adaptation journeys, the structured timeline mapping methodology was developed, which consists of completing timelines during interviews. Timelines were collected from 39 individuals in 17 households to explore how families perceive and adapt to environmental shifts. In addition, this research reflected on the added value and necessity of interviewing multiple household members to capture diverse lived experiences and ensure a comprehensive household-level perspective.Analysis of the data categorized the adaptation journeys into four typological groups reflecting different sensitivities and adaptive capacities: (1) diversified adjusters, (2) system maintainers, (3) environmental independence strivers, and (4) opportunity-driven adapters. All groups have differentiated responses to similar environmental changes, with differences in the temporality of the response, differences in the types of adaptations, and differences in the amount and diversity of adaptations. These differences result in resilience that evolves unevenly over time. Understanding these varied adaptation pathways lead to formulate policy recommendations aimed at improving adaptive capacity, resilience, and sustainable livelihoods.

Jury Prof. André FÜZFA (UNamur), présidentProf. Alexandre MAUROY (UNamur), secrétaireProf. Joseph WINKIN (UNamur)Prof. Raphaël JUNGERS (UCLouvain)Dr Milan KORDA (LAAS-CNRS, Toulouse)Prof. Igor MEZIC (University of California Santa Barbara) Abstract Switched systems became more and more interesting since they are conceptually closed to the description of real complex dynamics in which the state is not necessarily fixed in time but can abruptly change with the environment. In this context, not only a finite number of subsystems (said modes) are given to describe the possible state of the system, but also a switching (or commutation) law is assigned to indicate the active mode at each time.The stability theory of such systems is not intuitive since it is influenced by the commutation law, which plays a capital role.This dissertation investigates the uniform stability (i.e. stability under any commutation laws) and the switching stabilization (design of a stabilizing commutation law) problems of switched nonlinear systems.In the last decades, these problems have mainly been studied for switched linear systems and partially solved for the nonlinear case.The strategy exploited here is based on a successful tool today: the Koopman operator. This is a linear operator acting on an infinite-dimensional space of functions valued on the nonlinear system's state space. Roughly speaking, it allows one to transform a nonlinear finite-dimensional dynamics into a linear infinite-dimensional dynamics, from which one can deduce results for the original nonlinear system. More precisely, we utilize the Koopman operator framework to address switched nonlinear systems' uniform stability and stabilization problems.For the first problem, by using a Lie-algebraic solvability condition, we show that individual globally asymptotically stable nonlinear vector fields which admit a common Koopman finite-dimensional invariant subspace generate a uniformly globally asymptotically stable switched nonlinear system. In a broader context, we develop a general framework for studying the (uniform) stability of (switched) nonlinear systems on the polydisk or the hypercube. This systematic approach allows us to construct a common Lyapunov function that guarantee global uniform  asymptotic stability on the polydisk or the hypercube. We then apply this framework to derive systematic criteria for the global stability of nonlinear systems defined on the polydisk or the hypercube. Finally, for the second problem, we utilize the previously developed results to provide a  state-dependent switching stabilization strategy from  a systematic Lyapunov function of a convex combination of nonlinear vector fields.

Jury Prof. Benoît CHAMPAGNE (UNamur), présidentProf. Carmela APRILE (UNamur), secrétaireProf. Eric GAIGNEAUX (UCLouvain)Prof. Sonia FIORILLI (Politecnico di Torino)Prof. Wouter MARCHAL (UHasselt) Abstract Heterogeneous acid catalysts became over the years essential to our modern industrial world. Among the possible forms of solid materials with acidic properties, porous silica-based structures embedding active single-sites showed highly promising catalytic activity for various reactions. The insertion of heteroelements inside the SiO2 network is known to introduce a combination of Brønsted and Lewis acid sites which depends on the nature of the element and influences the catalytic properties of the solid. The present thesis investigates the link between the Brønsted/Lewis acid balance introduced by different elements (Al, Ga, In, Ti, Zr, Hf) inserted or finely dispersed in/onto the structure of extra-small silica nanospheres and the catalytic performances of the solids for two distinct biomass derivatives valorization reactions (i.e. conversion of glycerol to solketal and of ethyl levulinate to γ-valerolactone).The optimizations of the syntheses were particularly focusing on the insertion of the element inside the SiO2 matrix to maximize the number of acid sites. In-depth characterizations were conducted on the different substituted nanospheres to probe their morphological, structural, and textural features. A special attention was dedicated to the characterization of the surface acidity. These results were put into perspective with the catalytic performances of the materials. At the end of the investigations, we were able to explain the difference in terms of catalytic activity between the different studied solids and identify the optimal acid properties for the targeted reactions. The stability and recyclability of the best working solids were also assessed, an acute tuning of reaction conditions enabled to reach significatively high conversions, and their performances were tested in challenging conditions (i.e. close to crude feedstock).The knowledge unveiled through these investigations will give precious insight to design new silica-based catalysts with the appropriate acidity for a wide variety of acid-catalyzed reactions.

Au programme pour tous 09h30 | Cérémonie d'accueil à l'amphithéâtre Vauban.11h00 | Célébration de la rentrée à la Cathédrale Saint-Aubain suivie de l'accueil des étudiants par les Cercles. En savoir plus

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. 

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.

JuryProf. Guillaume BERIONNI (UNamur), présidentProf. Zineb MEKHALIF (UNamur), secrétaireProf. Catherine MICHAUX (UNamur)Prof. Noureddine NASRALLAH (Université des Sciences et Technologies - Houari Boumediene)Prof. Nacira NAAR (Université des Sciences et Technologies - Houari Boumediene)RésuméThe increasing in global energy demand and environmental concerns related to traditional energy sources necessitate the exploration of sustainable alternatives. This thesis investigates the potential of thermoelectric (TE) energy conversion using conducting polymer-based composites. Traditional TE materials, while efficient, face challenges such as toxicity and limited availability. Conducting polymers offer a promising solution due to their flexibility, processability, and tunable properties. By forming composites with materials like carbon nanotubes (CNTs) and graphene, their TE performance can be significantly enhanced. Surface treatment and functionalization are crucial for optimizing these composites and improving their efficiency.The thesis reviews the principles of thermoelectricity, including the Seebeck and Peltier effects, and the limitations of traditional TE materials, setting the stage for investigating conducting polymers as alternatives.The research methodology involves synthesizing and characterizing conducting polymer-based composites, focusing on surface treatment and functionalization techniques to enhance TE performance. Various composites incorporating graphene, CNTs, and metal oxide nanoparticles (bismuth oxide or nickel oxide) are synthesized and evaluated for their TE properties. The influence of surface modifications on composite morphology, charge transport, and TE parameters is systematically studied.The findings reveal significant improvements in TE efficiency through surface treatment and composite formation. Functionalization of graphene and CNTs enhances their compatibility with polymer matrices, improving dispersion and interfacial bonding, leading to higher electrical conductivity, reduced thermal conductivity, and ultimately, greater TE efficiency. Incorporating metal oxide nanoparticles further enhances the power factor, demonstrating the potential of hybrid composites in TE applications.Bienvenue à tous et toutes !