ED Sciences Chimiques
CO2-Switchable hydrophilicity Solvents : applications in microfluidics for chemical processes.
by Margaux ZOLLO (Laboratoire du Futur)
The defense will take place at 14h00 - Amphiteatre du CRPP Centre de recherche Paul Pascal (CRPP) 115 Avenue du Dr Albert Schweitzer, 33600 Pessac
in front of the jury composed of
- Yaocihuatl MEDINA-GONZALEZ - Chargée de recherche - Université de Bordeaux, Laboratoire du Futur (LOF), CNRS UMR 5258 - Directeur de these
- Karine LOUBIèRE - Directeur de recherche - Université de Toulouse, LGC - Laboratoire de Génie Chimique, CNRS UMR 5503 - Rapporteur
- Florent MALLOGGI - Chargé de recherche - Université Paris-Saclay, CEA, NIMBE/ LIONS, CNRS UMR 3685 - Rapporteur
- Thierry TASSAING - Directeur de recherche - Université de Bordeaux, ISM (Institut des Sciences Moléculaires), Groupe de spectroscopie moléculaire, CNRS UMR 5255 - Examinateur
- Samuel MARRE - Directeur de recherche - Université de Bordeaux, Institut de Chimie de la Matière Condensée de Bordeaux (ICMCB), UMR 5026 - Examinateur
One of the current challenges in developing greener chemical processes is finding low-volatility solvents that are easily separable, energy-efficient, and recyclable. Reversible CO2-responsive Switchable Hydrophilicity Solvents (SHS) offer a promising solution, providing an energy-efficient alternative to volatile solvents with fixed solvation properties. These solvents can transition from hydrophobic to hydrophilic in response to the presence of CO2 in water. Since their discovery in 2010, SHSs have shown potential in green solvent recovery for various applications, including liquid-liquid extraction and chemical synthesis. This thesis aims to propose a novel approach for investigating SHS performance using 2-2-Dibutylaminoethanol (DBAE), a known CO2-SHS, within a continuous microfluidic device made of poly(dimethylsiloxane) (PDMS). This method offers an adaptable and faster alternative to traditional batch reactors and millifluidic platforms. When exposed to water and CO2, DBAE undergoes a reversible transition from a tertiary amine (hydrophobic) to a bicarbonate salt (hydrophilic) at room temperature. Since previous literature lacks comprehensive information on the reactive mechanisms of switchable solvents, the first objective was to characterize the system using spectroscopic techniques. ATR-IR spectroscopy was employed to investigate DBAE's CO2 absorption capabilities. These experiments revealed that DBAE could produce a hydrophilic compound even without water, suggesting that the switch can occur in dry conditions, broadening applications of DBAE beyond water-based systems. Next, Raman spectroscopy was used to analyze the hydrophilicity switch in presence of water. This allowed the characterization of the species involved in the phase-change mechanism and the measurements of a Raman spectra library for DBAE/water/CO2 mixtures. Successively, the time required for DBAE's hydrophilicity switch was investigated at the microliter scale using a millifluidic tube-in-tube flow reactor equipped with a gas-permeable Teflon AF2400 tubular membrane. This ensured that the time measurements in the designed assembly were consistent with previous literature results. The assembly was also tested for continuous liquid-liquid extraction and separation using DBAE for decamethylcyclopentasiloxane (D5). Finally, the scale was reduced by implementing the hydrophilicity switch of DBAE in microfluidic chips made of PDMS (channel height 10-50 µm, channel width 200-400 µm). PDMS was chosen for its versatility, ease of microfabrication, and gas permeability. Two-level microfluidic chips were developed by layering a larger channel on top of the main microfluidic channel, leading to a membrane with thickness ~60-200 µm. This configuration allowed to impose either a CO2 or a N2 atmosphere over the microfluidic channel containing DBAE and water. Due to the gas permeability of PDMS, the gas passed through the membrane in the microfluidic channel to promote the phase change reaction of the SHS and modulate its solubility in water. Although the configuration faced intrinsic limitations—such as pervaporation, SHS solubility and diffusion within the PDMS matrix, and the weaknesses of plasma bonding in our multilayer PDMS chip—results demonstrated the feasibility of the switch within the PDMS-based microfluidic platform. The small dimensions of the setup significantly reduced the timescale of the phenomenon compared to previous studies. The PDMS microfluidic device was also successfully validated for the liquid-liquid extraction of soybean oil from a soybean oil/DBAE mixture. This accomplishment paves the way for a comprehensive examination of mass transport dynamics during liquid-liquid extraction and holds promise for continuous microfluidic extraction processes.
ED Sciences de la Vie et de la Santé
The role of Rho GTPase activation at the plasma membrane on cell cycle progression in Saccharomyces cerevisiae
by Landry PEYRAN (Institut de Biochimie et Génétique Cellulaires)
The defense will take place at h00 - Salle de conférence IBGC UMR 5095, Institut de Biochimie et Génétique Cellulaires 146 rue Léo Saignat 33000 Bordeaux
in front of the jury composed of
- Derek MCCUSKER - Directeur de recherche - Université de Bordeaux - Directeur de these
- Simonetta PIATTI - Directrice de recherche - Université de Montpellier - Rapporteur
- Yannick GACHET - Directeur de recherche - Université Paul Sabatier - Rapporteur
- Martine BASSILANA - Directrice de recherche - Université Côte d'Azur - Examinateur
- Lionel PINTARD - Directeur de recherche - Université Paris Cité - Examinateur
Healthy cell proliferation requires the correct ordering of cell cycle events and the monitoring of these events via checkpoints that delay cell cycle progression when problems arise. However, cells can bypass persistent checkpoint activation, continuing the cell cycle despite defects in chromosome number or DNA damage. It is therefore critical to understand how cells control the ordering of cell cycle events, how checkpoints monitor these events and how cells respond to sustained checkpoint activation. By combining molecular genetics and live cell imaging, we have discovered that the establishment of a polarity axis is a key event controlling the correct ordering of the cell cycle in Saccharomyces cerevisiae. As in many eukaryotes, polarity axis establishment in budding yeast requires activation of the Rho GTPase Cdc42. Defects in polarity trigger a Swe1 kinase-dependent cell cycle checkpoint that delays mitotic events via inhibitory phosphorylation of Cdk1. Using specific mutations that perturb the recruitment of Cdc42 activators to the plasma membrane, and thus Cdc42 nanoclustering, we observe multiple polarity defects resulting in catastrophic cell cycle problems. In contrast to WT cells in which successive waves of Cdk1 activity associated with different cyclins impart temporal order on cell cycle events, the polarity mutant is characterized by considerable G1, S and M cyclin overlap. The biological consequences of this misregulation include cell cycle misordering and the accumulation of multinucleate cells due to inappropriate whole genome duplication. These dramatic cell cycle defects accumulate despite robust Swe1-dependent inhibitory phosphorylation of Cdk1. In searching for signals upstream of Swe1 that may link the polarity machinery to the cell cycle, we found that the activation of this checkpoint involves a novel signal emanating from G1 cyclins. This signal appears to contribute to full Swe1 activity and the protective effect of this checkpoint when polarity defects are encountered. Indeed, perturbations of this signal resulted in a higher proportion of multinucleate cells. Since G1 cyclins are essential for Cdc42 activation and polarity axis establishment, they are well positioned to relay problems in polarity establishment back to the cell cycle machinery in order to activate Swe1 until sufficient active Cdc42 is generated. Collectively, our study illustrates an unexpected mechanism through which cell cycle ordering is controlled to ensure healthy cell proliferation and safeguard cells from unscheduled whole genome duplication.
ED Sciences Physiques et de l'Ingénieur
UNDERSTANDING THE CLIMATE AND STORMS ON URANUS AND NEPTUNE
by Noé CLEMENT (Laboratoire d'Astrophysique de Bordeaux)
The defense will take place at 14h00 - Salle Univers Laboratoire d'Astrophysique de Bordeaux Université de Bordeaux – Bât. B18N Allée Geoffroy Saint-Hilaire CS 50023 33615 PESSAC CEDEX
in front of the jury composed of
- Tristan GUILLOT - Directeur de recherche - Observatoire de la Côte d'Azur - Rapporteur
- Muriel GARGAUD - Directrice de recherche émérite - Université de Bordeaux - Examinateur
- Sandrine VINATIER - Chargée de recherche - Observatoire de Paris-Meudon - Examinateur
- Aymeric SPIGA - Professeur des universités - Sorbonne Université - CoDirecteur de these
- Ricardo HUESO - Associate Professor - University of the Basque Country - Rapporteur
- Franck SELSIS - Directeur de recherche - Laboratoire d'Astrophysique de Bordeaux - Directeur de these
Uranus and Neptune are the two most distant planets in our Solar System and thus receive little insolation, in addition to having long radiative timescales. However, they exhibit an intense meteorological activity: strong winds, large clouds, storms... What are the phenomena responsible for this activity? To answer this question, we study an interesting property of their atmospheres dominated by molecular hydrogen and helium. In the upper troposphere, methane is the third main molecule and condenses, yielding a vertical gradient in CH4. This condensable species being heavier than H2 and He, the resulting change in mean molecular weight due to condensation comes as a factor countering convection, traditionally considered as ruled by temperature only. It makes both dry and moist convection more difficult to start. During this PhD, I developed and used a 3D non-hydrostatic cloud-resolving model to simulate convection and moist convective storms on these planets. I looked particularly at the impact of methane abundance and methane latitudinal variations exhibited by observations. My thesis work shed light on the processes that trigger or inhibit these storms and characterized their intensity and frequency at different latitudes on ice giants.
ED Sciences et environnements
Physico-chemical processes and environmental impact of CO2 associated with CH4 leakage during geological storage in carbonatic near-surface aquifers. Experimental and in situ approach
by David SEGURA GONZALEZ (Environnements et Paléoenvironnements Océaniques et Continentaux)
The defense will take place at 14h00 - Amphi F 1 avenue du Dr Albert Schweitzer B.P. 99 33402 Talence Cedex
in front of the jury composed of
- Adrian CEREPI - Professeur des universités - Université de Bordeaux - Directeur de these
- Guillaume GALLIERO - Professeur des universités - Univ. de Pau et des Pays de l'Adour - Rapporteur
- Isabelle MARTINEZ - Professeure des universités - Université Paris Cité et IPGP - Rapporteur
- Bruno GARCIA - Cadre scientifique des EPIC - IFP Énergies Nouvelles - Examinateur
- Kévins RHINO - Cadre scientifique des EPIC - BRGM - Bureau de Recherches Géologiques et Minières - Examinateur
- Pascale BENEZETH - Directrice de recherche - CNRS Toulouse - Examinateur
- Corinne LOISY - Professeure des universités - Université de Bordeaux - CoDirecteur de these
The awareness of the international community and the convergence of scientific data around global warming confirm the urgency of deploying technologies to reduce greenhouse gas emissions. However, these gases can escape from deep geological storage and migrate to the overlying aquifers and the surface. It is therefore necessary to set up monitoring systems for geological CO2 storage to detect these possible leaks and assess their importance and impact on the water quality of the aquifers. In the event of a leak in the context of depleted tanks used for CO2 storage, the residual CH4 from the storage tank will likely be entrained with CO2. However, only a few studies have addressed the implications of the presence of CH4, and none have studied its potential as a monitoring parameter in the context of geological storage. Studying the physicochemical processes and impacts of CO2 leakage associated with CH4 in the event of a leak on a near-surface carbonate aquifer requires better characterization of multi-scale processes such as dissolution at the scale of the porous network or the transport of plumes at the macroscopic scale. Experimental and modeling methods used individually give responses to questions on particular processes, but these methods have limitations if used individually. Therefore, a hybrid, multi-scale approach is necessary. The experimental site of Saint Émilion, with eight wells already in place at the level of the Upper Oligocene aquifer, and past experiments on leakage in this aquifer, provides an excellent opportunity for a comprehensive multi-scale experimental and modeling study. In this thesis, the impact of leakage was studied at the scale of the carbonate core in the laboratory, focusing on understanding how dissolution processes change according to facies, groundwater velocity, salinity, and CO2 concentration. At the macroscopic scale, a CO2-CH4-rich water injection experiment was conducted at the Saint-Émilion site to understand better the physicochemical behavior of CO2 and CH4 in the carbonate aquifer. Finally, the experimental results were used for the 3D simulation of the reactive transport during a leak event, with the aim of verifying the experimental results and studying the leakage processes at the macroscopic scale under various conditions. The dissolution kinetics for each combination of CO2 concentration, injection rate, and salinity on carbonate cores were determined. Links between the evolution of porosity, permeability, and the type of sedimentary facies were established. The injection experiment revealed that some parameters can distinguish the leak from a natural event, that CO2 has a delay relative to CH4 in the farthest monitoring well, and that the correlation between electrical conductivity and CO2 concentration can detect a leak. Moreover, the modeling approach has allowed us to study how the parameters of the leak can modify the propagation of CO2 and CH4 plumes in three dimensions in the porous media. Modeling also enabled to establish the influence of surface interactions on CO2 and CH4 transport. These findings directly affect the development of effective monitoring and mitigation strategies for CO2 and CH4 leaks in geological storage sites.