Résultats de recherche

High-Sensitivity Birefringence Mapping Using Near-Circularly Polarized Light I will describe several techniques for mapping a two-dimensional birefringence distribution, which can be classified according to the optical schemes and principles of work:Illumination geometry (transmitted light/reflected light)Image acquisition (sequential acquisition/simultaneous acquisition)Polarization control (electrically controlled variable retardance/mechanical rotation).This classification facilitates a comparative analysis of the capabilities and limitations in these methods for birefringence characterization. Polychromatic polarizing microscopy (PPM) provides unique capabilities to alternative methods. It leverages vector interference to generate vivid, full-spectrum colors at extremely low retardances, down to < 10 nm. PPM is a significant departure from conventional polarizing microscopes that rely on Newton interference, which requires retardances above 400 nm for color formation. Furthermore, PPM's color output directly reflects the orientation of the birefringent material, a feature absent in conventional microscopy where color is solely determined by retardance.Joint seminar of ILEE & NISM!Le séminaire est accessible à des personnes externes également, pas besoin de s'inscrire. Plus d'infos

Conférence de Chimie donnée par le Dr. Thomas Boltje de l'Université de Radboud de Nimègue.Bienvenue à tous.

Jury Prof. Gaëlle PONTAROTTI (Université de Namur), présidenteProf. Claire DIEDERICH (Université de Namur), secrétaireProf. Christel MOONS (Université de Gand)Prof. Karin HANNES (KULeuven)Prof. Franck MEIJBOOM (Universiteit Utrecht)Prof. Saskia ARNDT (Universiteir Utrecht)Dr Claudia HIRTENFELDER (Independent Researcher)Dr Trudy SHARP (Department of Regional NSW, Australia) Résumé Le rapport 2018 des Nations Unies World Urbanization Prospects prévoit que d’ici 2050, 68 % de la population humaine vivra en zone urbaine, ce qui causera une augmentation des interactions entre les humains et les animaux non humains. Jusqu’à présent, la recherche sur le bien-être des animaux s’est principalement concentrée sur les environnements contrôlés tels que les laboratoires, la production animale industrielle et les zoos. Cependant, dans les milieux urbains, la complexité des écosystèmes et les effets des interactions homme-animal doivent être pris en compte. L’argumentation de cette thèse est que la science du bien-être animal devrait être élargie pour inclure et répondre aux défis spécifiques des contextes urbains. En effet, la biopolitique urbaine actuelle privilégie principalement les intérêts humains et ignore souvent les perspectives et les besoins des animaux domestiques et commensaux.La thèse présente cinq publications, qui examinent le développement, la mise en oeuvre et la perception publique de la gestion gouvernementale qui influence le bien-être des animaux urbains. Deux questions de recherche sont élaborées sur la base des lacunes identifiées afin d’étudier les aspects éthiques, scientifiques et politiques du bien-être des animaux urbains en Belgique. D’une part, comment la politique gouvernementale et sa mise en oeuvre influencent-elles le bien-être des animaux urbain (domestiques et commensaux), avec une attention particulière pour les chats, chiens, pigeons, renards, souris et rats ? D’autre part, quelles stratégies peuvent améliorer la coexistence harmonieuse urbaine de ces animaux avec les humains du point de vue du bien-être animal ? Les réponses à ces questions seront fournies lors de la défense publique. Abstract The 2018 UN World Urbanization Prospects report predicts that by 2050, 68% of the human population will live in urban areas, which will lead to an increase in interactions between humans and non-human animals. Animal welfare research has hitherto mainly focused on controlled environments such as laboratories, animal industry and zoos. In urban environments, on the other hand, the complexity of ecosystems and the effects of human-animal interactions must be taken into account. The thesis in this dissertation is that animal welfare science should be further developed to tackle the specific challenges of urban contexts. In addition, current urban biopolitics gives priority to human interests and often ignores the perspectives and welfare needs of both domestic and commensal animals.The dissertation presents five publications, looking at the development, implementation and public perception of governmental policy and management that influences the welfare of urban animals. Two research questions are developed based on the identified research gaps in order to study the ethical, scientific and policy-related aspects of urban animal welfare in Belgium. On the one hand, how do governmental policy and its implementation influence the welfare of urban animals (domestic and commensal), with particular attention to cats, dogs, pigeons, foxes, mice and rats? On the other hand, what strategies can enhance the harmonious urban coexistence of these animals and humans from the point of view of animal welfare? Answers to these questions will be provided during the public defense.

JuryProf. DE BOLLE Xavier (UNamur), PresidentProf. VINCENT Stéphane (UNamur), SecretaryProf. BOLTJE Thomas (Radboud University)Prof. GUIANVARC’H Dominique (Paris-Saclay University)Prof. WOUTERS Johan (UNamur)AbstractMannose is a carbohydrate that we can naturally find in some bacterial cell envelope, more precisely in lipopolysaccharide core. To explore the metabolic route of this natural sugar: Metabolic Gylcoengineering (MGE) has been employed for studying biomolecules in living systems. We aim to chemically modify the cell surfaces to install unnatural monosaccharides that are metabolically transformed and incorporated by microorganisms. The metabolic incorporation into glycans pathway can be visualized by biorthogonal click reactions with fluorescent reporters that can bind to unnatural carbohydrates. In this project, the strategy is to synthesize several mannose derivatives to target the metabolic route of D-mannose and explore the glycosylation pathway in Gram-negative bacteria.On top of that, another application is to apply this clickable mannose as an interesting building block to synthesize nucleotide sugar for antibodies (Ab) functionalization. Indeed, antibody-drug conjugates (ADC) constitute a new emerging class of highly potent pharmaceutical drugs, especially in cancer therapy. The aim is to perform regioselective modification in antibody’s subunit containing glycan chains from GDP-mannose derivative. This latter must be synthesized and tested as unnatural mannose donors for glycosyltransferase that catalyzes the transfer of sugar moiety to mannose acceptor in specific site of the antibody. 

Au programme 13h30 | Exposés des lauréats13h30 | Luca Dorio (UMons)14h05 | Guillaume Gégo (UMons)14h40 | Manon Lenoir (UCLouvain)15h15 | Madeleine Martinussen (UCLouvain)16h00 | Camille Ponsard (UNamur)16h35 | Baptiste Vincent (UCLouvain)17h10 | Délibération du jury18h00 | Attribution des deux prix suivie d'une réception à l'espace Bauchau

Cet événement est ouvert à tous, jeunes et seniors, partenaires académiques et industriels, avec une priorité aux doctorants pour les conférences. Nous souhaitons encourager les directeurs de thèse à faire de cet événement un succès en invitant tous leurs étudiants à y participer. La langue de la réunion sera l'anglais.   Trois orateurs principaux sont prévus :Vincent Rodriguez (Université de Bordeaux, France) | Utilisation de la lumière polarisée linéairement pour sonder l'activité chiroptique non linéaire des molécules et des foldamères d'oligoamides aromatiquesProf. Tatjana N. Parac-Vogt (KU Leuven) | Enzymes artificielles basées sur des grappes d'oxydes métalliques : des espèces discrètes aux matériaux étendusChristophe Copéret (ETH Zürich, Suisse) | Contenu préliminaire « Moitié catalyse et moitié RMN ». Différents créneaux pour 10 short talks (15 mins de présentation + 5 mins de Q/A) ainsi que 10 flashs posters (2 mins) seront disponibles pour les doctorants. Les doctorants et les chercheurs post-doctorants auront également la possibilité de présenter leurs travaux lors de sessions de posters. Les meilleures présentations orales et affichées seront récompensées.La participation est gratuite mais l'inscription est obligatoire via ce formulaire... 

Au programme 16h00 | Accueil des participants dans le hall de la Faculté de médecine16h30 | Séance anniversaire et inaugurale17h30 | Drink et visite (en groupe) des laboratoiresParticipation externe sur invitation. Une question ?  Contacter Jean-François Colomer : jean-francois.colomer@unamur.be 

Abstract The distribution of malaria in Sub-Saharan Africa is becoming increasingly heterogeneous, with emerging hotspots and a growing urban burden rather than following traditional vector suitability gradients. This pattern has been observed in Senegal, where malaria transmission ranges from very low to high. In this context, disease risk maps can help to identify hotspots and improve the targeting of interventions. However, previous studies have often relied on freely available, low-resolution remote sensing data and focused primarily on environmental factors related to vector presence—the hazard—while overlooking population vulnerability (e.g. influenced by access to healthcare). This thesis presents an open-source malaria risk mapping framework incorporating high-resolution, open-access data on both hazard and vulnerability, and identifies the key factors sustaining transmission in Senegal.Interpolated surfaces of vulnerability indicators were integrated with Sentinel-based hazard variables to model survey-based malaria prevalence, used as an indicator of risk. The framework was then extended to model malaria incidence from routine health facility data, using dasymetric disaggregation to create fine-scale incidence maps. The findings reveal that vulnerability is a key determinant of malaria and that both hazard and vulnerability risk factors vary with urbanisation level, transmission intensity, seasonality and spatial scale. Discrepancies emerged between malaria prevalence and incidence, such as low incidence but high prevalence in remote areas, suggesting potential underdiagnosis. This thesis also offers a comparative overview of various modelling approaches, ranging from machine learning to Bayesian geostatistics, with implementation code and guidance for future malaria research. Anticipated improvements in malaria epidemiological data will further enable elimination strategies to leverage the full potential of geospatial methods for fine-scale risk mapping. Composition du Jury Prof. Sabine HENRY (UNamur), PrésidenteProf. Catherine LINARD (UNamur), SecrétaireDr Ibrahima DIA (Institut Pasteur de Dakar)Dr Annelise TRAN (CIRAD, Montpellier)Prof. Christel FAES (Université de Hasselt)

Abstract Primarily described as an alarmone, secondary messenger (p)ppGpp, when accumulated, binds to many targets involved in DNA replication, translation, and transcription. In the asymmetrically-dividing a-proteobacterium Caulobacter crescentus, (p)ppGpp has been shown to strongly impact cell cycle progression and differentiation, promoting the non-replicating G1/swarmer phase. Mutations in the major subunits of transcriptional complex, b or b’ subunits, were able to display the (p)ppGpp-related phenotypes even in the absence of the alarmone. We identified that the transcriptional holo-enzyme, RNA polymerase (RNAP) is a primary target of (p)ppGpp in C. crescentus. Furthermore, mutations that inactivate (p)ppGpp binding to RNAP annihilated the (p)ppGpp-related phenotypes and phenocopied a (p)ppGpp0 strain. Our RNAseq analysis further elucidated the changes in the transcriptional landscape of C. crescentus cells displaying different (p)ppGpp levels and expressing RNAP mutants. Since the DNA replication initiation protein DnaA is required to exit the G1 phase, we observed that it was significantly less abundant in cells accumulating (p)ppGpp. We further explored its proteolysis under the influence of (p)ppGpp. Our work suggests that (p)ppGpp regulates cell cycle and differentiation in C. crescentus by reprogramming transcription and triggering proteolytic degradation of key cell cycle regulators by yet unknown mechanisms. In Part II, we identified two σ factors belonging to the ECF family that might be involved in this (p)ppGpp-accompanied phenotypes. In Part III, we propose an overlapping role of the ω subunit, RpoZ, and the heat shock subunit, RpoH, in carbon metabolism.JuryProf. Gipsi LIMA MENDEZ (UNamur), PresidentProf Régis HALLEZ (UNamur), SecretaryDr Emanuele BIONDI (CNRS-Université Paris-Saclay)Prof. Justine COLLIER (University of Lausanne)Dr Marie DELABY (Université de Montréal)

Abstract Estrogens originating from human and animal excretion, as well as from anthropogenic sources such as cosmetics, plastics, pesticides, detergents, and pharmaceuticals, are among the most concerning endocrine-disrupting compounds in aquatic environments due to their potent estrogenic activity. While their effects on fish reproduction are well documented, their impact on development, particularly metamorphosis, remains poorly studied. This hormonal transition, mainly controlled by the thyroid axis, is essential for the shift from the larval to the juvenile stage in teleosts.The effects of two contraceptive estrogens on zebrafish (Danio rerio) metamorphosis were evaluated: 17α-ethinylestradiol (EE2), a synthetic reference estrogen, and estetrol (E4), a natural estrogen recently introduced in a new combined oral contraceptive formulation. Continuous exposure from fertilization to the end of metamorphosis allowed the assessment of morphological changes, disruptions of the thyroid axis, and modifications of additional molecular pathways potentially involved in metamorphic regulation.EE2 induced significant delays and disturbances in metamorphosis, affecting both internal and external morphological traits, confirming its role as an endocrine disruptor of concern. In contrast, E4 did not cause any detectable morphological alterations even at concentrations far exceeding those expected in the environment, indicating a limited ecotoxicological risk. Molecular analyses showed that EE2 strongly affected thyroid signaling and energy metabolism during metamorphosis, whereas E4 induced only minor transcriptional and proteomic changes.This study provides the first evidence that EE2 can disrupt zebrafish metamorphosis and highlights the importance of including this developmental stage in ecotoxicological assessments. The results also suggest a larger environmental safety margin for E4, although further research is needed to clarify the mechanisms linking estrogen exposure to metamorphic regulation.JuryProf. Frederik DE LAENDER (UNamur), PrésidentProf. Patrick KESTEMONT (UNamur), SecrétaireDr Sébastien BAEKELANDT (UNamur)Dr Valérie CORNET (UNamur)Prof. Jean-Baptiste FINI (Muséum National d’Histoire Naturelle de Paris)Dr Marc MULLER (ULiège)Prof. Veerle DARRAS (KULeuven) 

AbstractThe Simbu serogroup, part of the Peribunyaviridae family, includes arboviruses associated with febrile disease and fetal congenital malformations due to viral neurotropism. These viruses possess a tripartite, negative-sense RNA genome that lacks the poly(A) tail. Notably, the 3' non-translated region of the small (S) genomic segment contains conserved RNA elements, including a stem loop (SL) structure and a sequence-based motif (GC signal) flanking the termination site for messenger RNA (mRNA) synthesis. Although their functions remain unclear, their conservation and specific positions suggest a potential role in mRNA transcription termination and translation initiation. A reverse genetics system for Schmallenberg virus (SBV), a ruminant pathogen, was used to generate a viral recombinant library bearing deliberate mutations. The replication kinetics, S segment transcription termination profile, and nucleoprotein (N) abundance were evaluated in mammalian and insect cell lines. At the same time, the virulence was assessed in an immunocompetent mouse model. Characterization of the mutant viruses indicated that the SL structure is essential for viral production, with the stem length being a key feature; at least five complementary base pairs are necessary between the stem arms. A shorter stem length impaired replicative fitness, N protein abundance, and altered the mRNA to complementary RNA ratio. Point mutations in the GC signal disrupted proper mRNA termination, thereby limiting viral N protein synthesis and, thus, virion assembly. In vivo, attenuated viruses resulted in lower viral loads, reduced neuroinvasion, and improved survival rates compared to the wild type SBV. The GC signal mutants exhibited strong attenuation while still maintaining active transcription. Overall, these findings indicate that the SL and GC signal serve as cis-regulatory elements and are indirect determinants of SBV virulence, regulating viral replication and neuropathogenesis.JuryProf. Patsy RENARD (UNamur), PrésidenteDr Damien COUPEAU (UNamur) SecrétaireProf. Damien VITOUR (Ecole Vétérinaire de Maisons-Alfort)Prof. Ludovic MARTINELLE (ULiège)Prof. Lionel TAFFOREAU (UMons)Prof. Charles NICAISE (UNamur)Prof. Benoît MUYLKENS (UNamur)

RésuméAlors qu'un courant de recherches s'efforçait de reformuler la mécanique quantique en abrogeant les opérateurs et en leur substituant des fonctions, Wigner et Szilard proposèrent en 1932 une quasi-distribution de probabilités définie sur l'espace de phase grâce à des fonctions d'onde. Ils n'expliquèrent pas quelle en avait été la genèse.La première partie de notre thèse propose une genèse de cette quasi-distribution, fondée sur les conditions naturelles qu'elles doit remplir. Elle se penche brièvement sur une pathologie dont elle est affectée : présenter dans certains sous-domaines de l'espace de phase des valeurs négatives (d'où le « quasi »), pathologie qui ne porte aucun préjudice au calcul des valeurs moyennes. Elle montre ensuite comment, si on tient compte du spin, les fonctions d'onde cédant la place aux spineurs, on est amené, grâce au calcul des valeurs moyennes d'observables, à une généralisation de cette quasi-distribution sous la forme d'une matrice hermitique. Cette démarche est étendue à la transformée croisée de Wigner, c'est-à-dire aux valeurs faibles.Un important théorème, qui a fait l'objet d'une publication, est démontré dans la deuxième partie de notre thèse. Utilisant l’analyse harmonique, ce résultat exprime les valeurs faibles en terme d’une intégrale sur un groupe Lie agissant sur l’espace de Hilbert considéré. Nous donnons deux exemples particuliers : SU(2) et SO(3). Le cas d'un groupe quotient est brièvement évoqué.Dans une troisième partie, nous rappelons le lien bien connu entre les algèbres de Clifford et deux équations importantes de la physique quantique : celle de Klein-Gordon et celle de Dirac, et sa généralisation aux espace-temps riemanniens.Nous introduisons enfin dans une quatrième partie les groupes de spin, et utilisons le groupe de spin Spin(3,2) dans le contexte de la transformée croisée de Wigner traitée dans la première partie.JuryProf. André FÜZFA (UNamur), PrésidentProf. Yves CAUDANO (UNamur), secrétaireDr Thomas DURT (Institut Fresnel et Ecole Centrale Marseille, Marseille, France)Prof. Romain MURENZI (Worcester Polytecnic Institute)Prof. Dominique LAMBERT (UNamur)Prof. Bertrand HESPEL (UNamur)Prof. André HARDY (UNamur)