ED Sciences Chimiques
Microfluidic approaches for the sorting and morpho-mechanical caracterisation of cellular aggregates
by Léon REMBOTTE (Centre de Recherche Paul Pascal)
The defense will take place at 10h00 - Amphithéâtre Centre de Recherche Paul Pascal 115 avenue du Docteur Albert Schweitzer Pessac 33600
in front of the jury composed of
- Jean-Christophe BARET - Professeur - Centre de Recherche Paul Pascal - CoDirecteur de these
- Charles BAROUD - Professeur - Ecole polytechnique - Rapporteur
- Pierre NASSOY - Directeur de recherche - Laboratoire Photonique, Numérique et Nanosciences - CoDirecteur de these
- Jean-François JOANNY - Professeur - Collège de France - Examinateur
- Claire WILHELM - Directrice de recherche - Institut Curie - Rapporteur
- Pierre JOSEPH - Directeur de recherche - LAAS-CNRS - Examinateur
- Diego BARESCH - Chargé de recherche - Institut de Mécanique et d'Ingénierie - Examinateur
- Cécile ZAKRI - Professeure - Centre de Recherche Paul Pascal - Examinateur
Cell aggregates, such as spheroids and organoids, are increasingly used in laboratories to replicate biological tissues. Typically comprising a few thousand cells, they exhibit an intermediate level of complexity between conventional cell cultures and animal models, and offer promising perspectives for both fundamental and applied research, particularly in the field of personalised medicine. However, their use remains limited by high experimental variability and by the lack of standardised analysis methods. In this context, this doctoral work aimed to develop automated approaches for the characterisation of large populations of cell aggregates. First, I adapted the principles of flow cytometry to the sorting of cell aggregates, based on real-time image analysis and encapsulation in millimetric droplets manipulated by acoustic radiation force. The cytometer thus designed is capable of measuring morphological and phenotypic properties within populations of several hundred aggregates, and of isolating subpopulations with homogeneous properties. This approach paves the way for more reproducible and statistically robust characterisation protocols for the study of spheroids and organoids. I then investigated the mechanisms of self-organisation of hiPSC cysts. These aggregates consist of a spherical epithelial cell monolayer enclosing a central cavity called a lumen, and are considered as models of embryos at the epiblast stage. Since these fragile samples cannot be imaged over long periods, I developed an on-chip cytometry method using automated confocal imaging, which enabled the analysis of hundreds of cysts at different stages of growth, from lumen formation to epithelial stratification. This revealed scaling laws of the self-organisation of hiPSC cysts and highlighted the key stages of their development, interpreted from a geometric and mechanical perspective. Finally, I characterised the mechanical properties of cysts through micropipette aspiration experiments, a technique historically dedicated to single cells and more recently adapted to multicellular aggregates. In particular, I studied cyst rupture under extreme deformations and explored the possibility of extending these analyses towards high-throughput deformability cytometry, in order to generalise the measurement of their mechanical properties. In this thesis, I thus introduced new methods for the manipulation and characterisation of multicellular aggregates, contributing to the standardisation of their large-scale study.
Development of multi-material fibers using Stack-and-Draw for applications as gas sensors
by Mathieu BONNARDEL (ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux)
The defense will take place at h00 - Amphitéatre 87 Avenue du Dr Albert Schweitzer, 33600 Pessac
in front of the jury composed of
- Angéline POULON - Maîtresse de conférences - Université de Bordeaux - Directeur de these
- Bruno BUREAU - Professeur des universités - Institut des Sciences Chimiques de Rennes - Rapporteur
- Frédéric SMEKTALA - Professeur des universités - Laboratoire Interdisciplinaire Carnot de Bourgogne - Rapporteur
- Thierry CARDINAL - Directeur de recherche - Institut Chimique de la Matière Condensée de Bordeaux - CoDirecteur de these
- Marcelo NALIN - Professeur des universités - Universidade Estadual Paulista (UNESP) - Examinateur
- Cyril AYMONIER - Professeur des universités - Institut Chimique de la Matière Condensée de Bordeaux - Examinateur
This thesis aims to design a multi-material fiber that can generate a microplasma in the air for use in gas analysis. The originality of the thesis lies in the integration of two metal electrodes within a ribbon-shaped glass sheath. The fiber is manufactured using the Stack-and-Draw (S&D) technique. This two-step process enables precise control over the architecture of the preform and the fiber after drawing.. Understanding the relationships between the process and microstructure, and between microstructure and electrical properties, is central to this work. The aim of this research is to improve our understanding of the thermal drawing mechanisms of soda-lime silicate glasses and aluminum alloys in the case of single-electrode and then dual-electrode fibers. Studying the relationship between drawing parameters (temperature, feed and drawing speeds) and the final architecture of ribbon glass fibers has revealed two fiber formation mechanisms directly related to the drawing speed. Analytical equations specific to each mechanism can be used to predict the final dimensions of both the fiber and the metal electrode can be predicted based on the selected drawing parameters. Using a 2xxx aluminum alloy as the electrode material reduces the likelihood of discontinuities occurring and enables multi-material fiber lengths much greater than those achieved with pure aluminum to be obtained. The electrical properties of metal electrodes are directly affected by the microstructure and the redissolution of the added elements. The S&D process and thermal drawing parameters also enable the precise control of the coplanar positioning of the two sheathed electrodes within the glass matrix. The value of the spacing between the electrodes determines the lifetime of the multi-material fiber during discharge. This work shows that the tip of each electrode is protected in situ during discharge by the formation of a dielectric layer that acts as a protective barrier. The formation of this layer significantly increases the emission duration of the microplasma. Initial tests carried out with hydrocarbon species (CN and CH) resulting from the combustion of hydrocarbons have validated the use of the multi-material fiber. The microplasma was analyzed by optical emission spectroscopy in order to identify the species present.
ED Sciences et environnements
Investigating spatial synchrony in European eel population dynamics and providing new tools to support the management of the species
by Mathilde BENEZECH (EABX - Écosystèmes aquatiques et changements globaux)
The defense will take place at 14h00 - Amphithéâtre INRAE, 50 Avenue de Verdun, 33610 Cestas
in front of the jury composed of
- Hilaire DROUINEAU - Ingénieur de recherche - Université de Bordeaux - Directeur de these
- Stéphanie MAHEVAS - Directrice de recherche - IFREMER - Rapporteur
- Estibaliz DIAZ - Chercheuse senior - AZTI - Examinateur
- Clara ULRICH - Directrice de recherche - IFREMER - Rapporteur
- Jean-Christophe POGGIALE - Professeur - Université Aix-Marseille - Examinateur
The European eel (Anguilla anguilla) is a catadromous fish that spawns in the Sargasso Sea and grows in the continental waters of Europe and North Africa. This species has been in decline since the 1980s, and no signs of recovery have been observed to date, despite the implementation of management measures. The assessment and management of this species face various challenges, such as (i) its wide distribution area involving a multitude of stakeholders, (ii) its complex life cycle, which is disurpted by various components of global change, and (iii) the spatial variability of its life history traits. The aim of this work is to improve understanding of the spatial dynamics of the European eel population in Europe during its continental phase in order to strengthen scientific expertise on the stock, on which its management and conservation are based. More specifically, we seek to study the spatio-temporal variations in the abundance and life history traits of the species, looking for potential spatial synchrony that could shed light on the causes of these variations. Changes in recruitment distribution and biomass in Europe are studied using time series analysis methods. Correlation analyses are conducted between biological data (spatial distribution, biomass) and environmental or anthropogenic data. An increase in the proportion of recruits arriving in the British Isles has been identified in recent years. For yellow and silver eels, differences are observed between the southernmost and northernmost regions. These results suggest that changes in ocean currents could alter the drift of larvae in the short term, while variations in ocean conditions could affect their long-term survival. For yellow and silver eels, correlations between biomass and temperature or climate indices suggest the influence of environmental conditions. In a context of global change, where the climate is likely to be disrupted, this highlights the challenges that eel conservation will face. This exploratory analysis is followed by the introduction of mechanistic links between the different continental stages (glass, yellow and silver eels, escapement) through the development of a spatial population dynamics model at the scale of species management units in France, Spain, and Portugal. The specific features of this model are (i) the integration of all continental stages through a homogeneous mechanistic approach, and (ii) its broad spatial coverage (international) while maintaining the spatial scale used in management, allowing for the spatial variability of life history traits and anthropogenic pressures to be taken into account. This model is a preliminary tool for integrating the spatial dimension into the study of population dynamics in a consistent manner and improving scientific advice on the stock. At the French level, the development of short-term recruitment forecasting models and their comparison using a multicriteria approach are proposed in order to provide a specific tool for estimating glass eel catch possibilities. The work carried out demonstrates the need to continue the efforts already underway to improve and standardize data collection. The contributions of this study are based both on the development of new statistical tools for studying the population dynamics of the species and on the information provided by the use of these tools. This work presents a homogeneous tool for large-scale spatial integration and constitutes preliminary work with the aim of achieving a spatial assessment of the population status.
ED Sociétés, Politique, Santé Publique
Coining Change. Production and Uses of Local Currencies in the Basque Country and Bristol
by Mathilde FOIS DUCLERC (Centre Emile Durkheim)
The defense will take place at 9h00 - Salle Copernic Sciences Po Bordeaux 11, Allée Ausone 33600 Pessac
in front of the jury composed of
- Andy SMITH - Directeur de Recherche - Université de Bordeaux - Directeur de these
- Sylvie OLLITRAULT - Directrice de recherche - Université de Nanterre - Rapporteur
- Ève CHIAPELLO - Directrice d'études - École des hautes études en sciences sociales (EHESS) - Rapporteur
- Matthieu MONTALBAN - Maître de conférences - Université de Bordeaux - CoDirecteur de these
- Xabier ITÇAINA - Directeur de recherche - CNRS - Sciences Po Bordeaux - Examinateur
- Jérôme BLANC - Professeur des universités - Sciences Po Lyon - Examinateur
‘Local currencies' are a type of alternative currency that combines advocacy with a market instrument. They are hybrid mechanisms that fall under both collective action and monetary instruments, raising a key question: when the organisation that claims to coin money has neither the status of a public authority nor the expertise of a payment services company, where does its moneyness come from, i.e. its quality as a medium of exchange and the recognition of its value within a territory or social group? This question amounts to examining the conditions for the institutionalisation of these currencies in specific contexts and analysing their integration into a broader monetary order. The empirical approach is based on a long-term ethnography (2019-2023) in the Basque Country, among those who strive to ‘circulate' the currency and who use it. A comparative perspective is provided by a second field study in England, which enabled more than twenty interviews to be conducted with Bristol Pound managers and members. The thesis reports on the work involved in building the local currencies studied – designing infrastructure, militant recruitment efforts, political work to legitimise them – and the appropriations – their uses and meanings – to which they are subject. The first part consists of a methodological chapter, a theoretical chapter and a historical chapter, which together defend the relevance of a political sociology of local currencies. The second part focuses on the production of local currencies: defining their political meaning, mobilising members, designing the technical infrastructure, and legitimising them. After studying production, the third part then analyses the appropriations to which local currencies are subject. Because they carry multiple social and political meanings, the uses of local currencies are an interesting case study for understanding both the politicisation of economic behaviour and the social differentiation of money. This part combines the study of the trajectories of actors and the tools of the economic sociology of money to paint a portrait of these currencies, as close as possible to actual practices. By linking ‘making money' in the sense of collective action to construct an alternative monetary instrument and mobilise around its use, and ‘making money' in the sense of the most interactive level of the practice of exchanging a banknote for an equivalent value in small notes or coins, we are able to link a political sociology of collective action with an economic sociology of the uses of money. The study of the production and uses of these currencies thus shows that moneyness is the product of institutionalisation processes that occur at several levels: at the most macro level, in terms of integration into a monetary order and legal recognition; at the meso level, in terms of organisational configurations and more or less fluid power relations structuring alliances and boundaries between movements, social groups and public administrations; at the micro level, in terms of incorporation into the uses of money.