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Séminaires Invités

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Séminaires donnés par des invités extérieurs au LIPhy.

Ce sont des séminaires généraux qui s’adressent à tous les membres du LIPhy. Par conséquent, l’introduction, la plus large possible, y joue un rôle important.

Les séminaires durent environ 1heure dont 15mn accordées aux questions. Ils ont lieu les lundis à 14h, en salle de conférence du laboratoire au deuxième étage. La langue des séminaires est en général l’anglais.

L’accès au laboratoire peut-être obtenu en contactant le secrétariat.

Agenda

  • Lundi 25 septembre 14:00-15:30 - Blaise DELMOTTE - Courant Institute of Mathematical Sciences, New-York, USA

    Hydrodynamic Genesis of Colloidal Creatures

    Résumé : When colloidal particles are rotating adjacent to a nearby floor, strong advective flows are generated around them, even quite far away. When a group of these microrollers is driven, the strong hydrodynamic coupling between particles leads to formation of new structures. Our experimental observation shows that a suspension of microrollers undergoes a cascade of instabilities : an initially uniform front of microrollers evolves first into a shock-like structure, which then quickly becomes unstable, emitting fingers of a well-defined wavelength ; then the fingertips pinch off to form compact motile structures translating at high speed. These colloidal creatures are self-sustained and form a stable state of the system.
    Combining experiments, large scale numerical simulations and continuum models, I will detail the mechanisms involved in each step. I will demonstrate that the whole process is primarily controlled by a geometric parameter : the height of the particles above the floor. I will also explain the predominant role of hydrodynamic collective effects in the development of these colloidal creatures. To conclude, I will show how to use these creatures for particle transport and flow generation in confined environments.



    The talk will be given by video-conference

    contact : Philippe Peyla

    Lieu : LIPhy, conference room - 140 Avenue de la Physique 38402 Saint Martin d’Hères


  • Lundi 2 octobre 14:00-15:30 - James FENG - University of British Columbia (UBC), Vancouver, Canada

    Collective Migration of Neural Crest Cells

    Résumé : During early vertebrate embryogenesis, neural crest cells (NCCs) migrate in clusters from the neural tube to various target locations over long distances. Their collective migration is tightly regulated by environmental signals and intercellular interactions. Curiously, NCC clusters are capable of spontaneously developing a persistent migration down migratory corridors in the absence of chemoattractants. To understand this phenomenon, we built a vertex-dynamics model that predicts the key modes of cell interactions—contact inhibition of locomotion (CIL) and co-attraction (COA)—through the modulation of Rho GTPase biochemistry. Using such a signaling-based model, as opposed to implementing hard-coded simulation rules, we find that CIL and COA conspire to suppress Rac1 activity, leading to the persistence of polarization (POP) of clustering cells and thus the spontaneous directional migration in the absence of chemical gradients.



    contact : Claude Verdier

    Lieu : LIPhy, conference room - 140 Avenue de la Physique 38402 Saint Martin d’Hères


  • Jeudi 5 octobre 11:00-12:30 - Matthieu GUÉDRA - LabTAU, INSERM Lyon, France

    Surface Instabilities and Nonspherical Oscillations of Bubbles in Ultrasonic Fields

    Résumé : Nonspherical bubble oscillations classically arise from the surface instability of an acoustically-driven bubble, through a mechanism similar to the hydrodynamic Faraday waves observed on a vertically-oscillating liquid layer. Although largely observed and reported for many years, the role played by these oscillations in various cavitation phenomena is not yet completely elucidated. To get a deeper insight into these nonspherical oscillations, we developed an experimental setup based on acoustic levitation and high-speed optical recordings of the bubble dynamics. First, I will present a set of experiments conducted using two synchronous high-speed cameras and discuss the axisymmetry properties of the surface modes. Then I will present two methods allowing to induce and control the nonspherical oscillations : (1) amplitude modulation of the ultrasonic field and (2) bubble coalescence. In both cases, the recorded temporal dynamics show evidence of nonlinear nonspherical oscillations which are supported by theoretical results obtained from recent models.



    contact : Philippe Marmottant

    Lieu : LIPhy, conference room - 140 Avenue de la Physique 38402 Saint Martin d’Hères


  • Lundi 9 octobre 14:00-15:30 - Sushil DUBEY - Soft Condensed Matter Raman Research Institute

    Mechanical Responses of Axonal Cytoskeleton

    Résumé : The mechanical properties of the axonal cytoskeleton play an important role in development (growth and retraction). We are studying the mechanical responses of neurons using a home-built Force Apparatus which is an optical fiber based instrument. Mechanical response of neuronal cells subjected to tension using the force apparatus shows non-linear viscoelastic behaviour. We are also studying stress relaxation and creep behaviour of the axon. Axons also show a transition from a viscoelastic elongation to active contraction and we aim to investigate the mechanism responsible for this effect. In short we plan to study (a) the roles played by the different cytoskeletal components, including motor proteins and MAPs in regulating the mechanical properties of axons, and (b) in exploring the feedback mechanism that regulate tension induced growth of axons. Our results show that f-actin plays important role in maintaining axonal tension which could be due to spectrin-actin skeleton arranged in periodic fashion.



    contact : Jocelyn Étienne

    Lieu : LIPhy, conference room - 140 Avenue de la Physique 38402 Saint Martin d’Hères


  • Lundi 16 octobre 14:00-15:30 - Yariv Kafri - Technion, Haifa

    Forces in active matter

    Résumé :



    contact : Eric Bertin

    Lieu : LIPhy, conference room - 140 Avenue de la Physique 38402 Saint Martin d’Hères


  • Lundi 30 octobre 14:00-15:30 - Thomas Ihle - Germany

    LIPHY Seminar

    Résumé :



    contact : Chaouqi Misbah

    Lieu : LIPhy, conference room - 140 Avenue de la Physique 38402 Saint Martin d’Hères


  • Lundi 6 novembre 14:00-15:30 - Laurent Courbin

    LIPHY Seminar

    Résumé :



    contact : Benjamin Dollet

    Lieu : LIPhy, conference room - 140 Avenue de la Physique 38402 Saint Martin d’Hères


  • Lundi 20 novembre 14:00-15:30 - Sebastian Aland - Dresden University

    LIPHY Seminar

    Résumé :



    contact : Gwennou Coupier

    Lieu : LIPhy, conference room - 140 Avenue de la Physique 38402 Saint Martin d’Hères


  • Lundi 27 novembre 14:00-15:30 - Carles Blanch-Mercader

    LIPHY Seminar

    Résumé :



    contact : Pierre Recho

    Lieu : LIPhy, conference room - 140 Avenue de la Physique 38402 Saint Martin d’Hères


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