ED Sciences Chimiques
Toward methodological rigor in life cycle assessment of emerging materials: Structure, reproducibility and transparency
by Ahmad Kamal KAMALI (Institut des Sciences Moléculaires)
The defense will take place at 14h00 - Salle de conférence (3ème etage) Bâtiment A12 Université de Bordeaux 351 Cr de la Libération 33405 Talence
in front of the jury composed of
- Guido SONNEMANN - Full professor - Université de Bordeaux - Directeur de these
- Jeroen GUINEE - Full professor - Leiden University - Rapporteur
- Peggy ZWOLINSKI - Full professor - Grenoble INP - Rapporteur
- Bertrand LARATTE - Professeur agrégé - Université Laval - CoDirecteur de these
- Magdalena SVANSTRöM - Directrice de recherche - Chalmers University of Technology - Examinateur
- Cyril AYMONIER - Directeur de recherche - Centre national de la recherche scientifique - Examinateur
Life cycle assessment (LCA) is a widely used method in industrial ecology whose applications extend beyond standardized practice to support exploratory assessments of emerging technologies. These technologies are characterized by novelty and high uncertainty compared with incumbent technologies, thus allowing cost-effective design modifications. However, their assessments raise three main challenges: comparability, data availability, and uncertainty management. Current responses include harmonization approaches, data estimation techniques, and sensitivity analyses. Focusing on materials engineering, this thesis identifies challenges in LCA practice through two remodeling projects of published research on carbon fibers and perovskite solar cells. It argues for a structured LCA approach privileging multiple heterogeneous models to reflect the high design freedom during research and development. These models investigate the influence of variations in modelling assumptions and contextual conditions on environmental impacts estimates. Accordingly, drawing on 22 case studies in the field of materials engineering, a non-exhaustive set of research questions is defined in relation to specific technology readiness levels, and for each question an appropriate model is proposed by providing recommendations on how modelling choices in the goal and scope definition stage should be set. Implementing this approach requires researchers to build systematically on prior work. LCAs must therefore be both reproducible and transparent. To support reproducibility, a reporting framework is developed that enables reproduction of both results and models and is informed by three complementary reviews covering LCA guidance documents, case studies, and methodological papers. A transparency threshold is then defined through a checklist that not only reports decisions but also justifies the choices made throughout the LCA. Together, these contributions aim to enable systematic estimation of environmental impacts to identify and implement environmentally sustainable technology development pathways.
ED Sciences de la Vie et de la Santé
Study of the respective role of glucose and lactate on excitability and basal synaptic transmission in adult rat somatosensory system
by Juan GARCIA-RUIZ (Neurocentre Magendie)
The defense will take place at 14h30 - Amphi Centre Broca 146 Rue Léo Saignat, 33000 Bordeaux, Francia
in front of the jury composed of
- Aude PANATIER - Directrice de recherche - Neurocentre Magendie - Directeur de these
- Pierre-Yves PLAÇAIS - Directeur de recherche - École supérieure de physique et de chimie industrielles de la ville de Paris - Rapporteur
- Jerome BAUFRETON - Directeur de recherche - Institut de Maladies Neurodégénératives - Examinateur
- Armelle RANCILLAC - Chargée de recherche - Centre interdisciplinaire de recherche en biologie - Rapporteur
The brain represents 2% of body weight but consumes 20% of the body's glucose: approximately 80% is used by neurons and 20% by astrocytes and other glial cells. While neurons were long thought to rely exclusively on glucose via GLUT3-dependent uptake, growing evidence highlighted an important role for astrocyte-derived lactate as an energy source. Astrocytes, positioned between blood vessels and synapses, take up glucose and convert it into lactate. Lactate is then released via MCT1/MCT4 transporters and taken up by neurons through MCT2 to generate ATP. Understanding when and how neurons switch between glucose and lactate remains a fundamental question in brain energetics. Neuronal activity spans a spectrum of energy demands. Action potentials represent a comparatively moderate energy load, whereas synaptic transmission is highly energy demanding and accounts for approximately 70% of the total signaling energy budget, largely due to the maintenance and restoration of ion gradients dissipated during neuronal communication. Our aim is to determine whether the choice of energy substrate depends on neuronal energy demand. In addition to its role in ATP production, we also investigated whether glucose may support neuronal function through alternative metabolic pathways, such as the pentose phosphate pathway (PPP), which contributes to redox homeostasis and biosynthetic processes. To address these questions, we used a viral approach to downregulate either the neuronal glucose transporter GLUT3, the neuronal lactate transporter MCT2, or the astrocytic lactate transporters MCT1/MCT4 in the rat somatosensory cortex. During whole-cell patch-clamp recordings, neuronal excitability was assessed by firing frequency, while basal synaptic transmission was evaluated through miniature excitatory postsynaptic events. Neuronal excitability appears to depend specifically on glucose, showing a gatekeeper role involving non-energetic metabolic functions through the PPP rather than ATP production itself. On the other hand, both glucose and lactate are involved in supporting basal synaptic transmission. These findings reveal distinct and complementary roles of glucose and lactate in neuronal function.
ED Sciences Physiques et de l'Ingénieur
DUST DYNAMICS IN PROTOPLANETARY DISKS: OBSERVATIONAL CONSTRAINTS OF PLANET-DISK INTERACTIONS AND INTERPLAY OF GRAIN GROWTH INSTABILITIES
by Thomas COLLIN-DUFRESNE (Laboratoire d'Astrophysique de Bordeaux)
The defense will take place at 14h00 - Salle Univers Laboratoire d'Astrophysique de Bordeaux Université de Bordeaux Bat. B18N Allee Geoffroy Saint Hilaire CS 50023
in front of the jury composed of
- Emmanuel DI FOLCO - Astronome adjoint - Laboratoire d'Astrophysique de Bordeaux - Directeur de these
- Sean RAYMOND - Directeur de recherche - Laboratoire d'Astrophysique de Bordeaux - Examinateur
- Héloïse MÉHEUT - Directrice de recherche - Observatoire de la Côte d'Azur - Rapporteur
- Sébastien FROMANG - Directeur de recherche - Laboratoire des Sciences du Climat et de l'Environnement - Rapporteur
- Audrey COUTENS - Astronome adjoint - INSTITUT DE RECHERCHE EN ASTROPHYSIQUE ET PLANÉTOLOGIE - Examinateur
- Clément BARUTEAU - Chargé de recherche - INSTITUT DE RECHERCHE EN ASTROPHYSIQUE ET PLANÉTOLOGIE - Examinateur
Protoplanetary discs orbiting young stars (1-10 million years old) are the cradle of planetary systems. However, directly observing forming planets is challenging due to the large optical depth of the discs. From a theoretical point of view, understanding the planet formation mechanisms is also limited by physical barriers that prevent the growth of millimeter/centimeter-sized grains. Recent observational advances have revealed a wide variety of structures in these discs that could betray dynamic interactions with nascent planets. The high concentrations of dust observed in these structures would make them particularly favorable sites for grain growth to occur. The present work focuses on the evolution of large crescent-shaped asymmetries, similar to those detected by the ALMA interferometer in a dozen discs. I conducted 2D multi-fluid hydrodynamic simulations of interactions between a disc and an embedded massive planet using the FARGO3D code. Additional synthetic observations were produced through radiative transfer calculations with the RADMC3D code. My study is based on the example of the young star AB Aurigae. Its disc includes a large cavity hosting protoplanet candidates and a crescent-shaped dust ring that is azimuthally very extended. I investigated the evolution of the vortex produced by the planet-induced Rossby instability, and that of the dust trap located at the pressure maximum, until complete vortex dissipation. I examined how the morphological characteristics of the dust ring could constrain the physical parameters of the planet orbiting in the cavity, and I found a degeneracy related to the planet's orbital eccentricity. Besides, I revisited the hypothesis that such a crescent may be the result of grains' gradual decoupling during the vortex dissipation phase. In my simulations, I explored the effect of multiple grain sizes and different opacities for the observability and lifetime of the crescent-shape structure. My work suggests a strong impact of the grains' back-reaction onto the gas for the dynamical evolution of the dust trap and for the multi-frequency observations in the millimeter domain. Lastly, I considered an alternative scenario in which accounting for the planet's slow growth naturally generates an elongated dust trap long before vortex dissipation. In a second part, I studied the development of the streaming instability (SI), a process believed to be active within dust traps where local dust concentration is promoted. To date, this is the leading mechanism for overcoming dust bouncing and fragmentation barriers. I considered a simplified version of the grain coagulation equation to perform a linear stability analysis in the presence of coagulation, and implemented it in a hydrodynamical code to carry out local 2D hydrodynamic simulations. In particular, I studied the effect of the coagulation instability (CI), recently discovered by Tominaga et al. (2021), which has the advantage of triggering at very low dust-to-gas ratios. I demonstrated that it produces initial concentrations of grains in the form of vertical filaments, within which SI can be triggered and lead to a 30-40-fold enrichment in dust compared to the case without coagulation. The subsequent evolution generates isotropic turbulence that spreads these filaments and, for Stokes numbers approaching unity, SI quickly dominates the effects of CI. My work suggests that coagulation instability can help trigger SI within the filaments, and that the interplay of the two instabilities leads to a significant source of turbulence in protoplanetary discs.