Supervisory authorities


   

   

our social networks


               

Search




Home > Research > Talks & Conferences > Talks Given at LIPhy

Invited Talks

published on , updated on

These talks are given by invited speakers at LIPhy. The intended audience is the whole LIPhy. A large general introduction intended for non-specialist is usually provided.

Typical talk duration is around one hour and includes about 15 mn of questions. The talks are scheduled usually every Monday at 2PM. The place is at the conference room, second floor.

Access to the lab can be obtained by calling Nadine D’Andréa or Chantal Reignier through the intercom at the main entrance.

Agenda

  • Monday 11 May 2015 14:00-15:00 - Hervé Mohrbach - Equipe BioPhysStat, Université de Lorraine, Metz

    Confotronics Of Bio-filaments

    Résumé : Many biofilaments like those of the cytoskeleton show anomalous behaviors in various experiments. As we will show, this can be explain by the existence of internal degrees of freedom, usually inaccessible by direct observation, but crucial for the understanding of the collective dynamics of the biofilaments. This is the case for coiled helices squeezed flat onto two-dimensional surfaces. Under such 2-d confinement, helices form “squeelices” — peculiar squeezed conformations often resembling looped waves, spirals or circles. The shapes as well as the unusual statistical mechanics of squeelices can be understood in terms of moving and interacting localized conformational quasiparticles called the “twist kinks”. These theoretical results will be interpreted in the light of recent experiments realized on actin and intermediate filaments.
    As a second example we will consider tubular lattices like microtubules. We will see that when prestress is introduced in such structures, localized conformational quasiparticles called “confloplexes” emerge and govern the collective shape dynamics of the lattice via elastically-mediated interactions. This allows to understand the anomalous elastic and dynamic behavior of microtubules. In particular, we will give an explanation for the formation of gliding microtubule arcs and rings in kinesin-driven gliding assays.



    contact: Catherine Quilliet

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


  • Monday 18 May 2015 14:00-15:00 - Marko POPOVIC - Netherlands Institute of Neuroscience

    Voltage Imaging – A Path Towards The Measurement Of The Input-Output Transform Function Of A Neuron

    Résumé : I have advanced the voltage imaging technique and used it in combination with classic electrode-based electrophysiology to study emergence and propagation of electrical events in both input and output structures within single mammalian neurons at unprecedented temporal resolution. I have measured the exact location and size of the action potential initiation site (axon initial segment) where the output is generated. I have observed directly how this structure changes in development and recorded in high spatio-temporal resolution the saltatory nature of action potential propagation in adult mammalian neurons. On the input side of a neuron, I made some of the first direct measurements of the electrical properties of the dendritic spines. A notable finding of these studies is that spine heads are not electrically isolated from the primary dendrites. Spine heads in layer 5 neocortical neurons rather act as a separate biochemical (but not electrical) sub-cellular compartment.



    contact: Marco Canepari

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


  • Monday 1 June 2015 14:00-15:00 - Julie LAFAURIE-JANVORE - LadHyX, Ecole Polytechnique, France

    Cell Mechanotransduction: From Cell Division To Cardiovascular Diseases

    Résumé : In this talk I will present two examples of cellular mechanotransduction, a term referring to the conversion of a mechanical signal into a biochemical signal which allows cells to sense the physical properties of their microenvironment and to adapt their function accordingly. First I will discuss how mitotic daughter cells regulate their final separation by a force-sensing mechanism. During late cytokinesis, the two daughter cells remain connected by a thin intercellular bridge which is severed during a final process called abscission. Counterintuitively, the pulling forces exerted by the daughter cells on the bridge delay the severing, whereas a release of tension induces abscission. This regulation may have a strong impact on tissue organization and morphogenesis. In the second part of the talk, I will present a microfluidic platform developed to study vascular endothelial cell mechanotransduction. Because atherosclerosis develops preferentially at arterial branches where blood flow is highly disturbed, it is fundamental to understand how flow-derived mechanical forces modulate the function of endothelial cells. This platform allows independent control of various parameters, including the amplitude and direction of the flow, cell density, cell shape and cell polarization relative to the flow, combined with high resolution live imaging of cellular responses. We study intracellular calcium mobilization as a read-out of endothelial cell response to flow-derived forces.



    contact: Chaouqi Misbah

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


  • Monday 22 June 2015 14:00-15:00 - Don C. Lamb - LMU Munich, Germany

    How to Juggle Photons. Fluorescence Methods for Investigating the Nanoworld

    Résumé : In my research group, we work on the development and application of advanced fluorescence methods. Ten years ago, we introduced pulsed interleaved excitation (PIE) based on the idea of alternating laser excitation from the group of Shimon Weiss. With PIE, the photons are juggled by alternating the excitation source, which provides new functionalities to many fluorescence methods. I will give a brief introduction into PIE and the advances that can be gained when combining PIE with fluctuation spectroscopies. We have used pulse interleaved excitation fluctuation imaging (PIE-FI) to investigate the first steps of HIV assembly in the cytosol. We could detect the formation of Gag oligomers, which provide a nucleus for viral assembly upon reaching the plasma membrane. Another application of PIE is the quantitative analysis of single-molecule Förster Resonance Energy Transfer (FRET) experiments. I will explain how one can perform quantitative two- and three-color FRET experiments on single molecules and discuss the new information that three-color FRET provides. As a last example of how we juggle photons, I will introduce orbital tracking. With orbital tracking, we can follow single particles in real-time in living organisms. By tracking the motion of individual mitochondria in Zebra fish embryos, we gain insights into how this important organelle is transported in neurons.



    contact: Aurélie Dupont

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


  • Monday 29 June 2015 14:00-15:00 - Philip Kollmannsberger - ETH, Laboratory of Applied Mechanobiology, Zurich, Switzerland

    Cell-Matrix Feedback from the Single Cell to the Tissue Scale

    Résumé : The continuous interaction of cells with each other through the extracellular matrix (ECM) during growth and remodeling defines a feedback loop that is important for controlling tissue self-organization. I will present various techniques to quantify the mechanobiology of cell-matrix interactions from the single cell to the tissue scale. Using ECM-coated magnetic microbeads, the response of the cell-matrix interface to large forces was probed and a universal relationship between the contractility and the nonlinear viscoelasticity of the cell was found. In a multicellular context, the balance of cell contractility and substrate geometry was found to determine both the conformation of the deposited ECM and the proliferation patterns in growing microtissues. This implies that scaffold geometry can be specifically engineered to pattern active stresses in order to direct cell behavior and ECM organization towards a desired functional outcome.
    These studies were complemented by imaging and quantification of cell networks and ECM organization in healthy and diseased ex vivo tissue, and by computational modeling of the complex feedback systems that link cell-level behavior to tissue-level response. Together, these studies result in a more quantitative understanding of cell-matrix mechanobiology and thus help to improve regenerative therapies for contractile force-bearing tissues.



    contact: Cécile Bidan

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


  • Monday 31 August 2015 14:00-15:30 - Matthieu RUPIN - Équipe Ondes en Milieux Complexes, Institut Langevin, Paris

    Passive And Active Metamaterials For Elastic Waves

    Résumé : The physics of waves has regained a lot of interest within the last two decades with the advent of metamaterials. The latter refer to man-made composite media engineered at a microscopic scale with respect to the wavelength. Whatever the type of waves the same approach is conducted: the response of the sub-wavelength elementary units gives rise to macroscopic effective properties for the propagation of waves. In this talk, I will present two different kinds of metamaterials related to very different applications: seismology and bio-physics.
    First, I will show experimental and theoretical results on a metamaterial dedicated to elastic waves with seismic applications as objective. The experiment is conducted on a thin table-size aluminum plate coupled to an ensemble of long aluminum rods acting as sub-wavelength resonators. This system is very instructive because of the presence of different types of waves in both the plate and the rods.
    Second, I will present an example in the audible acoustic range of a metamaterial that exhibits a spatial non-uniformity of its properties which mimics the behavior of a dead cochlea. When active processes are introduced in the resonators some encouraging preliminary results show the possibility to reproduce some known features of the living cochlea.



    contact: Philippe Marmottant

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


  • Monday 28 September 2015 14:00-15:00 - Thomas FRANKE - Biomedical Engineering, University of Glasgow, United Kingdom

    Passive and Active Sorting and Manipulation of Soft Objects in Microflow

    Résumé : The use of acoustics in microfluidics has become very popular for the past few years because it provides a versatile tool to manipulate small amounts of fluid on a chip in a highly controlled manner. Mixing, pumping, focusing, and deflection have been successfully demonstrated and already included in commercially available products. However, in many cases simple passive techniques, that just exploit a particular flow field and its interaction with soft objects, such as red blood cells, are sufficient to achieve controlled sorting.
    In this presentation, we give an overview of existing microfluidics techniques for sorting and manipulation of biological cells and drops used in our lab with special focus on acoustical microfluidics and non-inertial lift force techniques. In particular we show triggered sorting and separation of circulating tumor cells and red blood cells at high speed in microfluidic channels based on laser interrogation similar to FACS (Fluorescence-activated cell sorting).



    contact: Thomas Podgorski

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


  • Monday 12 October 2015 14:00-15:30 - Simon Merminod - Laboratoire MSC, Paris 7

    Order-Disorder Transitions in a Driven Magnetic Granular Monolayer

    Résumé : Soft ferromagnetic particles are placed inside a horizontal, quasi-two-dimensional cell and are vertically vibrated, so that they perform a horizontal Brownian motion. When immersed in an external vertical magnetic field, the particles become magnetized and thus interact according to a dipolar repulsive law. Ordered and disordered phases are observed depending on the particle area fraction and on the ratio of the magnetic energy to the kinetic energy. At low particle area fraction, we show that, prior to the complete solidification of the disordered granular gas into a crystalline state, the typical properties of this dissipative granular gas progressively approach those expected for a usual gas at thermodynamic equilibrium.
    Surprisingly, when the area fraction is higher, the system solidifies into a large-scale disordered labyrinthine phase mostly constituted of randomly orientated short chains of particles in contact. We characterize quantitatively this transition and explain the formation of these chains using a simple model. Moreover, we show that the labyrinthine phase exhibits slow dynamics.



    contact: Eric Bertin

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


  • Monday 19 October 2015 14:00-15:30 - Jean-François RUPPRECHT - Ecole Normale Supérieure, Paris

    Velocity Condensation of Magnetotactic Bacteria

    Résumé : Magnetotactic swimmers tend to align along the magnetic field against stochastic reorientations. We show that the swimming strategy, e.g. active Brownian motion versus run-and-tumble dynamics, strongly affects the orientation statistics with the magnetic field. The latter exhibits a velocity condensation above a critical magnetic field, whereby the alignment probability density diverges. In particular, Lévy walks display a drastic reactivity at the onset of collective interactions. Our results suggest that the run-and-tumble dynamics can outperform active Brownian motion as a survival strategy.



    contact: Philippe Peyla

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


  • 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | ... | 22

  • Wednesday 16 December 2015 10:00-17:00 - plusieurs intervenants

    Journée speckle

    Résumé : *Erik Geissler (DLS et diffusion cohérente des X) ;
    *Romain Pierrat - ESPCI (diffusion optique simple/multiple dans les milieux désordonnés + aspects dynamiques) ;
    *Vincent Favre Niccolin - I.Néel (imagerie par diffraction cohérente des X)

    Lieu : salle de lecture


  • Wednesday 6 July 2016 08:30-18:00 -

    Workshop depinning vs yielding

  • Friday 24 June 2016 14:00-15:30 - Emanuela Del Gado - Georgetown University, Washington DC, USA

    Gelation and Densification of Cement Hydrates: A Soft Matter in Construction

    Résumé : Abstract: 5-8 % of the global human CO2 production comes from the production of cement, concrete main binder. The material strength emerges through the development, once in contact with water, of calcium-silicate-hydrate (C-S-H) gels that literally glue together the final compound. Current industrial research aims at exploring alternative and more environmentally friendly chemical compositions while enhancing rheology and mechanics, to overcome the many technological challenges and guarantee concrete standards. Identifying the fundamental mechanisms that control the gel properties at the early stages of hydration and setting is crucial, although challenging, because of far-from-equilibrium conditions, closely intertwined to the evolution of the chemical environment, that are a hallmark of cement hydration.
    I will discuss a recently developed statistical physics approach, which allows us to investigate the gel formation under the out-of-equilibrium conditions typical of cement hydration and the role of the nano-scale structure in C-S-H mechanics upon hardening. Our approach, combining Monte Carlo and Molecular Dynamics simulations, unveils for the first time how some distinctive features of the kinetics of cement hydration can be related to the nano-scale effective interactions and to the changes in the morphology of the gels. The novel emerging picture is that the changes of the physico-chemical environment, which dictate the evolution of the effective interactions, specifically favor the gel formation and its continuous densification. Our findings provide new handles to design properties of this complex material and an extensive comparison of numerical findings for the hardened paste with experiments ranging from SANS, SEM, adsorption/desorption of N2 and water to nano-indentation provide new, fundamental insights into the microscopic origin of the properties measured.
    K. Ioannidou, R.J.-M. Pellenq and E. Del Gado, Controlling local packing and growth in calcium-silicate-hydrate gels, Soft Matter 10, 1121 (2014)
    E. Del Gado, K. Ioannidou, E. Masoero, A. Baronnet, R. J.-M. Pellenq, F. J. Ulm and S. Yip, A soft matter in construction - Statistical physics approach for formation and mechanics of C—S—H gels in cement, Eur. Phys. J. - ST 223, 2285 (2014).
    K. Ioannidou, K.J. Krakowiak, M. Bauchy, C.G. Hoover, E. Masoero, S. Yip, F.-J. Ulm, P. Levitz, R.J.-M. Pellenq and E. Del Gado, The mesoscale texture of cement hydrates , PNAS 113, 2029 (2016)
    K. Ioannidou, M. Kanduc, L. Li, D. Frenkel, J. Dobnikar and E. Del Gado, The crucial effect of early-stage gelation on the mechanical properties of cement hydrates, Nature Communications (2016), to appear.



    contact: Kirsten Martens

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


  • Wednesday 10 November 14:00-17:30 - Nicolas Cuny

    PhD Nicolas Cuny

    Résumé : Dérivations de modèles constitutifs: de la microstructure à la rhéologie des suspensions denses molles
    Jury:

    • Madame Catherine Barentin, Professeur Université Lyon 1
    • Monsieur Ludovic Berthier, Directeur de Recherche CNRS, Université de Montpellier
    • Monsieur Michel Cloitre, Directeur de Recherche CNRS, ESPCI Paris
    • Monsieur Vincent Démery, Maître de conférence, ESPCI Paris
    • Monsieur Pierre Saramito, Directeur de Recherche CNRS, Université Grenoble-Alpes
    • Monsieur Gilles Tarjus, Directeur de Recherche CNRS, Sorbonne Université

    Lieu : Salle de conférence LIPhy


Ajouter un événement iCal