ED Sciences Chimiques
ELECTROCHEMILUMINESCENCE: FROM NEW LUMINOPHORES TO LIGHT-EMITTING DEVICES
by Miaoxia LIU (Institut des Sciences Moléculaires)
The defense will take place at 14h00 - Amphi 2 Groupe NanoSystèmes Analytiques Institut des Sciences Moléculaires - UMR 5255 CNRS ENSMAC/Bordeaux INP, Université de Bordeaux 16, Avenue Pey-Berland 33607 PESSAC Cedex FRANCE, Site ENSMAC, 33607 Pessac, France
in front of the jury composed of
- Neso SOJIC - Professeur des universités - Bordeaux INP - Directeur de these
- Aurélie BOUCHET-SPINELLI - Maîtresse de conférences - Université Grenoble-Alpes - Rapporteur
- Arnaud CHOVIN - Maître de conférences - Université Paris Cité - Rapporteur
- Francisco JAVIER DEL CAMPO - Professeur - Basque Center for Materials - Examinateur
- Estelle LEBEGUE-LEVACHE - Maîtresse de conférences - Université de Nantes - Examinateur
- Laurent BOUFFIER - Directeur de recherche - CNRS, Université de Bordeaux - Examinateur
Electrochemiluminescence (ECL) is a light-emitting process triggered at the electrode surface, where a series of redox reactions generate excited-state luminophores that emit light when they relax to the ground state. ECL offers exceptional advantages by integrating electrochemical input with optical output, such as high sensitivity, ultralow background signal, precise spatiotemporal control, and the absence of photobleaching and phototoxicity. These features have established ECL as a powerful transduction technology in bioassays, chemical analysis, and imaging. Meanwhile, multimodal imaging that integrates two or more optical modalities within a single device has gained considerable attention due to its potential application in the simultaneous acquisition of multiple biological or chemical information, providing a powerful tool for studying complex systems. In particular, light-emitting approaches based on ECL or light emitting diodes (LEDs), are interesting alternatives to develop novel imaging systems. In this context, my thesis aims to develop new ECL-active dyes emitting in the near-infrared (NIR) region to extend the potentialities of ECL technology and develop multimodal light-emitting devices and multicolor light-emitting arrays based on the coupling of ECL and LEDs. First, we investigated intense ECL emission from the redox switching of a series of heterobimetallic systems consisting of lanthanide complexes emitting in the NIR range (Yb3+ and Nd3+) associated with a redox-active carbon-rich ruthenium bipyridyl antenna chelate. The electrochemical reactions between the Ru antenna and the sacrificial ECL co-reactant not only allow for the efficient low-potential ECL generation but also modulate the NIR-ECL of Yb3+ (980 nm) and Nd3+ (875-1063 nm) via intramolecular energy transfer. This strategy offers interesting new insights into NIR ECL systems based on inorganic complexes. Additionally, we developed several wireless multimodal light-emitting chemical systems by coupling two light sources based on different physical principles: ECL occurring at the electrode interface and an LED switched on by an electrochemically triggered electron flow. Both endogenous (thermodynamically spontaneous redox process) and exogenous (requiring an external power source) bipolar electrochemistry were employed as driving forces to trigger both light emissions at different wavelengths. Building upon these concepts, we further develop a multicolor light-emitting array based on the electrochemically switch-on of LEDs with different intrinsic threshold voltages. The endogenous bipolar electrochemistry, as a driving force through the coupling of thermodynamically favorable oxidation of magnesium and the kinetically favorable proton reduction on platinum to power LEDs of various colors. Moreover, this platform also enables triggering an additional light emission based on the interfacial reductive-oxidation ECL mechanism of the Ru(bpy)32+/S2O82- system. The approaches presented here interconnect optical imaging and electrochemical reactions, providing a novel and so far unexplored alternative to design autonomous hybrid systems with multimodal and multicolor optical readouts for complex bio-chemical systems.
ED Sciences de la Vie et de la Santé
Improving the acceptability to enhance the efficiency of stroke rehabilitation procedures based on brain-computer interfaces
by Elise GREVET (Institut de neurosciences cognitives et intégratives d'Aquitaine)
The defense will take place at 10h00 - Amphithéâtre BBS Bâtiment Bordeaux Biologie Santé 2 Rue Dr Hoffmann Martinot 33000 Bordeaux
in front of the jury composed of
- Camille JEUNET-KELWAY - Docteure - Université de Bordeaux - Directeur de these
- François CABESTAING - Professeur des universités - Université de Lille - Rapporteur
- Andrea KÜBLER - Professeure des universités - Julius-Maximilians-Universität Würzburg - Rapporteur
- Julie LEMARIé - Professeure des universités - Université de Toulouse - Examinateur
- Ricardo CHAVARRIAGA - Chargé de recherche - Centre for Artificial Intelligence, School of Engineering, Zurich University of Applied Sciences ZHAW - Rapporteur
- Athanasios VOURVOPOULOS - Assistant professor - Instituto Superior Técnico (IST), Universidade de Lisboa - Examinateur
Over the past thirty years, the global incidence of stroke has risen by 70%, making post-stroke motor rehabilitation a pressing public health priority. In this context, motor imagery (MI), the mental simulation of movement, combined with sensory feedback (e.g., limb mobilisation) is frequently employed in rehabilitation to “close the sensorimotor loop.” Its therapeutic value lies in the activation of neural circuits that closely overlap with those involved in actual movement execution, thereby fostering neuroplasticity and promoting functional recovery. However, a major limitation of current approaches is the lack of synchronisation between the MI generated by the patient and the physical mobilisation delivered by the therapist. Brain-computer interfaces (BCIs), which analyse brain activity in real time to detect MI, allow for precise temporal coupling with sensory feedback. As such, they represent a promising technology to address this limitation. Yet despite their recognised potential, BCIs remain marginal in clinical use, largely due to limited ergonomic development. Even a technically optimal BCI is of little value if patients and clinicians are unable or unwilling to use it, in other words, if it is not accepted. We hypothesise, first, that personalising BCI protocols based on individual acceptability factors could reduce patient anxiety, enhance engagement, facilitate learning, and ultimately improve motor recovery. Second, the patient's social environment, including the attitudes, perceptions, and behaviours of relatives and health professionals, may also influence acceptability, and by extension, the clinical efficacy of BCIs. To test these hypotheses, our research is structured around three main objectives: I. To model the determinants of BCI acceptability across patients, health professionals, and the general public; II. To personalise BCI rehabilitation protocols for patients, and to evaluate this personalisation in terms of (i) acceptability and (ii) motor recovery outcomes; III. To develop awareness-raising initiatives aimed at improving BCI acceptability among the general public and health professionals, and by extension, among all stakeholders likely to encounter these technologies. Under Objective 1, we developed the first theoretical model of BCI acceptability in post-stroke rehabilitation, along with an associated questionnaire, both made publicly available (https://bci-acceptability-tool.cnrs.fr/). The questionnaire was administered to the general public (N = 753) and to post-stroke patients (N = 140). In parallel, semi-structured interviews were conducted with 12 patients and 12 health professionals. These data informed: (i) the levers for personalising BCI protocols (Objective 2); and (ii) the priority content areas for communication materials (Objective 3). Clustering methods combined with regression analyses were used to identify distinct patient profiles based on acceptability factors (Objective 2). These findings led to the development of automatised personalisation strategies, embedded in a “Plug & Play” software solution designed for ease of clinical deployment. This system enabled the launch of a multicentre randomised controlled trial, currently underway, involving 52 subacute patients (across the Toulouse, Bordeaux, and Montauban university hospitals), each undergoing 15 training sessions. The aim is to compare the efficacy and acceptability of personalised versus standard BCI protocols. Finally, in support of objective 3, a digital exhibition is being developed in partnership with the “Science with and for Society” programme at the University of Bordeaux. This initiative seeks to demystify BCIs and foster their acceptability among the general public, patients, their families, and healthcare providers.
Learning to decide: a neurocognitive perspective in rats
by Hadrien PLAT (Institut de neurosciences cognitives et intégratives d'Aquitaine)
The defense will take place at 14h00 - Amphithéâtre BBS 2 rue du Dr Hoffmann Martinot, 33076, Bordeaux Bâtiment BBS, Campus Carreire
in front of the jury composed of
- Etienne COUTUREAU - Directeur de recherche - Université de Bordeaux - Directeur de these
- Muriel KOEHL - Directrice de recherche - Université de Bordeaux - Examinateur
- Emmanuel PROCYK - Directeur de recherche - Université de Lyon - Examinateur
- Benoit GIRARD - Directeur de recherche - Université de la Sorbonne - Rapporteur
- Valérie DOYERE - Directrice de recherche - Université Paris-Saclay - Rapporteur
Everyday we make decisions based on our current needs and desires, which rely on previously learned associations. In an ever-changing environment, we must continually track and update our representations of these relevant associations to adjust our behavior appropriately. Moreover, effective decision-making in uncertain and volatile settings requires a delicate balance: when observations no longer align with expectations, individuals must decide whether these deviations signal real change or just random noise. The objective of this Ph.D. project was to investigate the complementary roles of the prefrontal cortex (PFC) and the locus coeruleus (LC) in mediating behavioral flexibility. The first chapter examines the role of the medial prefrontal cortex (mPFC) and its noradrenergic inputs from the LC in updating Pavlovian stimulus–outcome associations. Using a contingency degradation paradigm, we assessed the ability of rats to adapt their conditioned responses when a cue no longer predicted reward better than its absence. Chemogenetic inhibition of the mPFC impaired this adaptive responding, and similar deficits followed inhibition of LC→mPFC projections. In contrast, neither the OFC nor LC→OFC were required. These results highlight a specific role for the LC–mPFC circuit in flexible Pavlovian learning. The second chapter explores noradrenergic signaling in the orbitofrontal cortex (OFC) during reversal learning. Using fiber photometry, we found that noradrenaline (NA) release in the OFC increased after unexpected rewards during contingency reversals. The magnitude of these signals correlated with individual performances on the subsequent days. Using chemogenetic and optogenetic inhibition of LC→OFC projections, we found that disrupting NA transmission at reversal, or specifically during reward, impaired behavioral adaptation. These findings demonstrate that OFC-NA activity serves as an early, predictive signal that facilitates flexible behavioral adaptation in changing environments. The third chapter investigates how NA signaling in the OFC contributes to decision-making under uncertainty and volatility using a probabilistic reversal learning task. We developed a new reinforcement learning model that tracks expected uncertainty and volatility using reward prediction errors and action–outcome incompatibility. First, we found that this model better fit behavior than fixed-learning-rate models. Moreover, chemogenetic OFC inhibition impaired post-reversal adaptation and OFC NA fiber photometry recordings revealed post-reversal increases resembling estimated volatility signals. Finally, LC→OFC inhibition reduced post-reversal performance, and model simulations showed this effect could be reproduced by reducing volatility's impact on learning rates. These findings reveal how OFC–NA circuits facilitate behavioral adaptation in changing environments. Taken together, this thesis provides converging evidence for a complementary role of the prefrontal cortex and the locus coeruleus–noradrenaline system in supporting behavioral flexibility. Across Pavlovian and instrumental learning paradigms, we show that distinct prefrontal subregions (mPFC and OFC) interact with noradrenergic inputs from the LC to detect and respond to changes in environmental contingencies. Using chemogenetics, optogenetics, photometry, and computational modeling, we show how these circuits enable generalizable behavioral flexibility under unpredictable and changing conditions.
ED Sciences Physiques et de l'Ingénieur
Study of the 238U(d,d′) and 238U(d,p) surrogate reactions in inverse kinematics at the ESR heavy-ion storage ring.
by Camille BERTHELOT (Laboratoire de Physique des 2 Infinis de Bordeaux)
The defense will take place at 9h30 - Salle Marie Curie LP2i Bordeaux Site du Haut Vigneau, 19 chemin du Solarium 33170 GRADIGNAN
in front of the jury composed of
- Beatriz JURADO APRUZZESE - Directrice de recherche - LP2i Bordeaux - Directeur de these
- Antoine LEMASSON - Chargé de recherche - Grand Accélérateur National d'Ions Lourds - Rapporteur
- Faïrouz HAMMACHE - Directrice de recherche - Laboratoire de Physique des 2 infinis Irène Joliot-Curie – IJCLab - Rapporteur
- Jan GLORIUS - Chargé de recherche - GSI Helmholtzzentrum für Schwerionenforschung GmbH - Examinateur
- Chloë HEBBORN - Chargée de recherche - Laboratoire de Physique des 2 infinis Irène Joliot-Curie – IJCLab - Examinateur
- Manfred GRIESER - Directeur de recherche émérite - Max-Planck-Institut für Kernphysik - Examinateur
- Christine MARQUET - Directrice de recherche - LP2i Bordeaux - Examinateur
Neutron-induced reaction cross sections of short-lived nuclei are essential for applications in nuclear technology, medicine and astrophysics. However, these cross sections are very difficult or impossible to measure due to the difficulty to produce and handle the necessary radioactive targets. This thesis work, conducted in the frame of the NECTAR (Nuclear rEaCTions At storage Rings) project, uses the surrogate-reaction method in inverse kinematics at a heavy-ion storage ring. This method enables the measurement of the de-excitation probabilities as a function of the excitation energy of the nuclei formed through the surrogate-reaction with unrivaled precision and indirectly determine the aforementioned cross sections. This work describes the preparation and the analysis of the measurement that took place at the Experimental storage ring (ESR) of the GSI/FAIR facility (Darmstadt, Germany) in June 2024, where the inelastic scattering 238U(d,d′) and the transfer 238U(d,p) reactions were used as surrogate reactions for the neutron-capture reaction of 237U and 238U, respectively. For the first time, the fission, γ-ray- and one-neutron emission probabilities were measured simultaneously for these uranium nuclei, in addition to the two-neutron and three-neutron emission probabilities for the 239U. The results are compared to neutron-induced theoretical calculations, as well as to experimental probabilities from other works.