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Accueil > Recherche > Séminaires & Conférences > Séminaires au Laboratoire

Soutenances de Thèse/HDR

publié le , mis à jour le

Ci-dessous, la liste des soutenances de thèse se déroulant au LIPhy.

Les soutenances se déroulent (sauf mention contraire) dans la salle de conférence au deuxième étage. Les félicitations au jeune docteur se font en général dans la salle de lecture mitoyenne.

Les manuscrits des thèses soutenues peuvent être consultés/téléchargés en ligne.


Agenda

  • Lundi 8 novembre 2021 14:00-17:30 -

    PhD. C. Arauz

    Résumé : Titre : Bubble growth in a confined polymer under temperature changes
    Résumé : We investigate the dissolution or growth of bubbles in polymeric systems driven by means of temperature variations. In this regard, laminated safety glass serves as an inspiration. The latter is a multi-layered assembly, which includes a thin, hygroscopic, polymeric film (typically, polyvinyl butyral-PVB) positioned in between two layers of glass. The assembly, guarantees that, if broken, sharp glass shards remain bonded to the polymeric interlayer. However, it is common to observe bubbles in laminated glass. These bubbles, which are anathema to the beautiful appearance of glass, can occur during production, quality testing at high temperatures or during normal operation and are typically associated with air oversaturation.
    During the thesis, an experimental transparent setup was developed to reproduce one of the main steps involved in the production of safety glass at the laboratory scale, i.e., autoclaving at high temperatures (140°C). The setup allows tracking the dissolution or growth of interfacial gases (gas pockets) or bubbles in glass/PVB/glass samples (or in otherwise transparent samples) when subjected to variations in temperature. We identify that air and water vapour follow distinct thermodynamic paths in terms of solubility with increasing temperature. As a result, water vapor leads to bubble growth while air favours dissolution. The observed kinetic behaviour of gas pockets/bubbles is highly non-monotonous and is strongly influenced by the rheology of the interlayer. A non-isothermal kinetic bubble model is thus proposed addressing the nature of the two gases, the finiteness of the system, as well as the complex viscoelastic behaviour of the polymeric interlayer that was characterized in depth.
    Jury :

    • Monsieur Matteo Ciccotti - Professeur ESPCI
    • Monsieur Christophe Raufaste - Maitre de conférence
    • Monsieur Rafael Estevez - Professeur des universités
    • Monsieur Christian Carrot - Professeur des universités
    • Monsieur Eric Dufresne - Professeur, ETH Zurich
    • Monsieur Constantin Coussios - Professeur Oxford University
    • Monsieur Keyvan Piroird - chef de plateforme R&D, Saint-Gobain Recherche


  • Jeudi 9 décembre 2021 13:00-18:30 -

    PhD. Aline Cisse

    Résumé : Titre : L’étude de la lipoprotéine à basse-densité par microscopie électronique et diffusion neutronique.
    Studies of low-density lipoproteins by cryo-electron microscopy and neutron scattering
    Résumé :
    Les lipoprotéines à basse densité (LDL) jouent un rôle crucial dans le métabolisme du cholestérol. Responsables de son transport du foie vers les organes, leur accumulation dans les artères est à l’origine de maladies cardiovasculaires, telles que l’athérosclérose. Constituées d’un cœur composé de cholestérol, dans sa forme libre ou estérifié, ainsi que de triglycérides, les LDL sont entourées d’une membrane de phospholipides, ainsi que d’une protéine immense : l’apolipoprotéine B-100 (apo B-100). Sur la LDL, la protéine contient des parties exposées en surface, et d’autres partiellement incorporées dans la membrane. Apo B-100 est impliquée dans de nombreuses fonctionnalités de la LDL, comme la réception des LDL par les organes, ou la conversion des VLDL (lipoprotéines à très basse densité) en LDL.
    Dans ce contexte, ce travail de thèse s’est concentré sur plusieurs questions fondamentales, qui sont encore peu étudiées : Quelle est la structure d’une LDL et où se trouve la protéine apo B-100 ? Quelle est la dynamique moléculaire d’apo B-100 ? Pour répondre à ces questions, nous avons utilisé deux techniques ; la cryo-microscopie électronique (cryo-EM) pour explorer des échelles de l’Angstrom au nanomètre, la diffusion incohérente élastique et quasi-élastique de neutrons (EINS, QENS) qui permet d’accéder à des échelles de temps de la picoseconde à la nanoseconde.
    À partir de la reconstruction 3D de cryo-EM, nous proposons une vision révisée des LDL, dans laquelle apo B-100 s’avère particulièrement flexible à la surface de la LDL, une propriété qui ne faisait pas consensus dans la communauté jusqu’à présent. En parallèle, l’application des techniques EINS et QENS à un échantillon d’apo B-100 solubilisé par détergent, dans lequel le détergent est toujours présent, rendait nécessaire l’introduction d’une méthodologie pour traiter de tels échantillons. Pour séparer analytiquement les contributions, et ainsi résoudre un problème qui ne se trouve pas seulement dans le cas d’apo B-100, mais plus généralement pour les protéines membranaires, nous présentons une nouvelle approche pour analyser les données QENS.
    Low-density lipoproteins (LDL) play a crucial role in the metabolism of cholesterol in the blood. Responsible for its transport from the liver to the organs, their accumulation in the arteries is the cause of cardiovascular diseases, such as atherosclerosis. Consisting of a core composed of cholesterol, in its free or esterified form, as well as triglycerides, LDL is surrounded by a membrane of phospholipids, as well as a huge protein : apolipoprotein B-100 (apo B-100). On LDL, the protein contains surface-exposed parts, and others partially incorporated into the membrane. Apo B-100 is involved in many functionalities of LDL, such as the reception of LDL by organs, or the conversion of VLDL (very low density lipoproteins) into LDL.
    In this context, this thesis work focused on several fundamental questions, which are still scarcely studied : What is the structure of LDL and where is the apo B-100 protein located ? What are the molecular dynamics of apo B-100 ? To answer these questions, two techniques were applied ; cryo-electron microscopy (cryo-EM) to explore the Angstrom to nanometer scale, elastic and quasi-elastic incoherent neutron scattering (EINS, QENS) which can probe time scales from picosecond to nanosecond.
    From the cryo-EM 3D reconstruction, we propose a revised view of LDL, with a huge flexibility of apo B-100 on LDL, a property that was not a consensus in the LDL community until now. In parallel, application of EINS and QENS to the detergent-solubilized apo B-100, in which detergent is still present, called for a new methodology to tackle such samples. To analytically separate the contributions, and to solve a problem that is not only found in the case of apo B-100, but more generally for membrane proteins, we present a novel approach to analyze the QENS data.

    Jury :

    • Judth Peters, Université Grenoble Alpes, Directrice de thèse
    • Pr. Elisabeth CHARLAIX, Université Grenoble Alpes, Examinatrice
    • Assoc. Pr. Ruth PRASSL, Medical University of Graz, Examinatrice
    • Pr. Giovanna FRAGNETO, ILL, Examinatrice
    • Pr. Marc JAMIN, Université Grenoble-Alpes, Examinateur
    • Dr. Aurélie BERTIN, CNRS, Rapporteure
    • Pr. Jörg PIEPER, University of Tartu, Rapporteur
    • Dr. Ambroise DESFOSSES, CNRS, Invité


  • Mardi 14 décembre 2021 14:00-17:30 -

    HDR. Karin John

  • Lundi 31 janvier 08:00-14:00 -

    Phd. Maxime Bonnefoy

    Résumé : Titre : Étude exploratoire et transdisciplinaire par analogie des mouvements de cellules et d’humains au sein d’architectures équivalentes


  • Mercredi 9 mars 13:30-17:30 -

    Phd Georges Chabouh

    Résumé : Titre : Ultrasound contrast agents : from spherical oscillations and buckling dynamics to swimming
    Résumé :
    Cleverly engineered microswimmers have been of increasing scientific interest, as they show great promise in various biomedical applications.
    In this study, we propose a novel mechanism of propulsion in fluids at the microscale, using a buckling mechanism activated by pressure waves. We considered an in vivo-friendly hollow elastic shell of micrometric size composed of a lipidic membrane enclosing a gas bubble. Such microshells are approved for clinical use as diagnostic ultrasound contrast agents (UCAs).
    We experimentally investigate the buckling dynamics of microshells upon an increase of the external pressure. The effect of the driving frequency is studied as well as that of the size and mechanical properties of the microshells. We confront the results to existing theories on buckling dynamics that consider shells made out of an isotropic and incompressible material.
    In parallel, we highlight that such hypothesis are too restrictive to account accurately for the dynamics of such UCAs with lipidic shells. Considering these shortcomings, we observe the spherical oscillations of these shells. In this simpler configuration, we derive a new theoretical model that includes the compressibility of the shell and its elastic anisotropy in the radial direction. We thus offer a better description of the spherical oscillations that have been widely studied theoretically and experimentally in the past three decades.
    Finally, we evidence, a non-zero displacement upon a complete cycle of deflation and re-inflation of the microshells, that includes buckling events.
    The proposed propulsion mechanism whose direction is controlled in the shell ref- erence frame can be an answer to the problem of directivity accounted in the acoustic radiation force technique used in ultrasound molecular imaging and drug delivery.


  • Vendredi 6 mai 14:00-16:30 - Artur Ruppel

    PhD defense : Optogenetic interrogation of intercellular propagation of force signals

    Résumé : Optogenetic interrogation of intercellular propagation of force signals
    Cell generated forces play a major role in coordinating large-scale behavior of cells, in particular during development, wound healing and cancer. Mechanical signals based on cellular force generation propagate faster than biochemical signals, but can have similar effects, especially in epithelial tissue with tight cell-cell adhesion. However, a quantitative description of the transmission chain from force generation in a sender cell, force propagation across cell-cell boundaries, and the concomitant response of receiver cells is missing due to the lack of appropriate model systems. Here we show that such a setup can be realized by combining optogenetics and micropatterning. Our minimal system are two epithelial cells on an H-pattern ("cell doublet"). After optogenetically activating RhoA, a major regulator of cell contractility, in the sender cell, we measure the mechanical response of the receiver cell by traction force and monolayer stress microscopies. In contrast to single cells on the same pattern ("cell singlet"), whose force generation after half-activation suffers from internal flows, in the cell doublet the cell boundary suppresses global flows and leads to a stable contractile situation. Force propagation and response of the receiver cell strongly depends on the actin organization in the sender cell, which we control by the aspect ratio of the H-pattern. Thus both cell-cell boundary and organization of the sender cell are essential for stimulation of the receiver cell. We quantify the active response of the receiver cell by comparing it with the passive response calculated with a mathematical model. We find that the response essentially matches the signal strength of the sender cell, and that it is the stronger the more organized the actin cytoskeleton is perpendicular to the direction of the cell-cell boundary, reminiscent of the Poisson effect in passive material. We finally show that the same effects are at work in small tissues. Our work demonstrates that cellular organization and active mechanical response of tissue is key to avoid global actin flows and to generate an elastic response that can lead to long-range mechanical signaling across the tissue.


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