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

Invited Talks

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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 16 February 2015 14:00-15:00 - Rosario Capozza - International School for Advanced Studies (SISSA), Trieste, Italy

    Electrical charging effects on lubrication properties of a model confined ionic liquid

    Résumé : Electrical charging of parallel plates confining a model ionic liquid down to nanoscale distances yields a variety of charge-induced changes in the structural features of the confined film. By means of molecular dynamics simulations, I explore this variety of phenomena using a simple charged coarse-grained model of ionic liquid. With grand-canonical-like conditions to allow the flow of ions in and out of the interplate gap, I simulate the liquid squeezout and obtain effective enthalpy curves showing the local minima that correspond to layering, and predict the switching between one and another under squeezing and charging.
    In view of a possible electrical control of friction, I also explore the dependence of friction upon successive squeezout and charging of plates.
    The actual frictional behavior obtained does depend upon the assumed features and parameters of the model liquid and its interaction with the plates, yet, the broader scenario obtained for charging effects upon boundary lubrication, appear of general value.
    contact: Cyril Picard

    Lieu : LIPHY-Conference Room


  • Monday 23 February 2015 14:00-15:00 - Xavier Pelorson - GIPSA, UJF, Grenoble

    Physical modelling of voice production with application to voice pathology

    Résumé : Physical modelling of voice production with application to voice pathology
    The production of voiced sounds, vowels for instance, is mainly due to the self-sustained oscillation of the vocal folds. From the point of view of histology, the fine structure of the vocal folds is complex as they are constituted of layers of different nature (squamous epithelium, lamina propria and vocalis muscle). The dimensions of each vocal fold can vary considerably depending on gender, age and subjects. After centuries of controversy, the
    production of voiced sounds, phonation, is now widely accepted as being the result of a non-linear interaction between an airflow coming from the lungs, the elastic vocal folds and some acoustical resonators (the oral or the nasal tract and the subglottal system).
    In this talk I will present a brief overview of the research carried out at Gipsa-lab concerning the physical modelling of this phenomenon. I will successively focus on the fluid mechanical description of the air flow through the larynx, on the acoustics of the vocal tract, on the biomechanics of the vocal folds and on their interactions. The performance of these theoretical models is tested against experiments performed on mechanical replicas of the human phonatory system.
    Besides increasing our knowledge about the complex mechanisms involved during speech, the motivation for such a study concerns speech synthesis using physical models and voice pathology diagnostic or treatment. This later point will be illustrated using some examples of ongoing research.
    Contact: Claude Verdier

    Lieu : LIPhy-Conference room, 2nd floor


  • Monday 2 March 2015 14:00-15:00 - Stefan Klumpp - Max Planck Institute of Colloids and Interfaces, Potsdam, Germany

    Cellular economy of molecular machines

    Résumé : The central dogma of molecular biology states that genetic information flows unidirectionally, from DNA to RNA to protein. The steps in processing the genetic information are carried out by specifically dedicated molecular machines (RNA and DNA polymerases, ribosomes) that themselves are either proteins or (in the case of ribosomes) RNA-protein complexes. Thus, the seemingly unidirectional flow of genetic information involves feedback loops for the required machinery. In the talk, I will explore some interesting consequences of these feedbacks.
    I will address mechanistic aspects as well as aspects of the cellular economy of these machines. Specific topics to be discussed are physical constraints on the maximal rates of RNA synthesis (transcription), the effect of dense RNA polymerase traffic on transcription accuracy, the growth rate dependence of the cellular abundance of these machines and the role of molecular crowding in protein synthesis (translation).
    Contacts: Hans Geiselmann and Hidde de Jong

    Lieu : LIPhy, conference room


  • Monday 9 March 2015 14:00-15:00 - Jean BAUDRY - Laboratoire Colloïdes et Materiaux Divises, Ecole Supérieure de Physique et de Chimie Industrielles, Paris

    Adaptation dynamics in bacteria

    Résumé : Bacteria have developed many strategies to adapt to their environment. We investigate some aspects of this adaptation at the scale of the micro-organism.
    We have developed a technique based on water droplet in oil, where bacteria can grow in the desired environment in each droplet. This technique allows for the statistical investigation of their phenotype (see figure) and quantitative assessment of the dynamics of adaptation to stress.
    I will detail in particular the phenomenon of « bacterial phase variation » which helps bacteria to rapidly adapt to variable environment and I will describe the measured diversification under a nutritional stress in a prolonged stationary phase.



    contact: Bahram Houchmandzadeh

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


  • Monday 16 March 2015 14:00-15:00 - Cécile BIDAN - LIPHY-MOTIV, Université Joseph Fourier Grenoble & CNRS

    Geometric Control of Tissue Growth and Organisation

    Résumé : As in morphogenesis, wound healing and bone remodelling, the various tissues of our body are continuously modelled, remodelled and repaired by the cells. Even if these biological processes are encoded in genetics, the cells also adapt to the physical cues of their surroundings. For example, by determining the boundary conditions for the mechanical environment, geometry has been shown to influence biological mechanisms at the sub-cellular, cellular and multi-cellular levels. Here we aim at understanding how the geometry of a substrate influences the deposition and organisation of tissue.
    Osteoblasts were cultured to grow bone tissue in three-dimensional hydroxyapatite scaffolds in-vitro. In parallel, the hypothesis that geometry locally influences tissue deposition on a surface was implemented into a computational model of curvature-driven growth. A geometrical interpretation based on elongated contractile cells was proposed to link this model to the organization of the cells observed in the tissue. Finally, the structural investigations were extended to the extracellular matrix to further clarify the mechanisms involved in tissue patterning and organization.



    contact: Aurélie Dupont

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


  • Monday 23 March 2015 14:00-15:00 - Ayache BOUAKAZ - Inserm U930, Université François Rabelais, Tours, France

    Precision Drug Delivery With Ultrasound And Microbubbles: Mechanisms, Applications and Progress to Clinics

    Résumé : Targeted drug delivery (delivery of a drug to a spatially localized site in the human body) is one of the most ambitious goals of modern therapy. The strict localization of the pharmacological activity of a drug to the site of pathology would result in a significant reduction in systemic drug toxicity. In recent years, new promising possibilities for targeted drug delivery have been discovered based on the combination of ultrasound (US) and microbubbles. Sonoporation, which consists of the interaction of US waves and gas microbubbles induces a transient permeabilization of the cell membrane allowing for the uptake of drugs or DNA.
    Today, the mechanisms involved in the sonoporation process and the cell membrane permeabilization remain poorly identified. Although no consensus has been reached, several scenarios have been hypothesized, including the formation of pores, further stimulation of endocytotic pathways and occurrence of membrane wounds. Elucidating the mechanisms responsible for delivery of compounds to the cells and the kinetics of permeabilization are essential in order to improve and control this therapeutic strategy. This talk will focus on the current knowledge of the mechanisms of sonoporation and drug delivery using US and microbubbles. We will also discuss the current therapeutic applications of microbubbles and future progress and potential translational use into clinics.



    contact: Philippe Marmottant

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


  • Monday 30 March 2015 14:00-15:00 - Yohan DAVIT - IMFT, Toulouse

    A porous medium approach to transport phenomena in biological systems

    Résumé : Transport phenomena in porous media generally occur over a broad spectrum of time- and length-scales, so that understanding and modeling these phenomena often requires a combination of specific theoretical, computational and experimental tools. This has led to the development of “generic methods” for porous media, including upscaling approaches such as the volume averaging technique or multiscale asymptotics. The goal of these techniques is to answer fundamental questions related to the multiscale nature of the system, such as: When and how can we adopt a macroscopic point of view and describe a system in an average sense? Other examples of generic methods include pore-network models that provide a simplified description of the complex geometry and topology of the porous structure, or imaging techniques such as x-ray computed microtomography. The originality of our group in Toulouse, the “Groupe d’Etude des Milieux Poreux”, is to specialize in both the development of these generic methods and their application to a variety of objects including biological systems (“biological porous media”).
    In this talk, I present an overview of my work on porous media. In the first part, I describe one of the generic methods, the volume averaging technique, and show how it can be applied to scalar transport by advection and diffusion in porous media. Our approach further combines volume averaging with x-ray microtomography and computational fluid dynamics to develop models for problems as different as heat transfer in composite structures and non-newtonian flow in sandstones. In the second part of this talk, I will show how these generic methods developed for “standard” porous media can be applied to biological systems. I will focus on two example problems we are currently working on: (1) x-ray microtomography of biofilms (communities of microorganisms) growing within porous media; and (2) a model for microvascular cerebral flow that combines a pore network description of the flow in large veins/arteries with a homogenized (Darcy-like) continuum model in the capillaries. The latter uses a “well model” concept to couple the pore-network with the continuum that was initially developed in petroleum engineering.



    contact: Philippe Peyla

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


  • Monday 27 April 2015 14:00-15:00 - Anotida MADZVAMUSE - Mathematics, University of Sussex, UK

    Mathematical Modelling and Numerical Simulations of Actin Dynamics in the Eukaryotic Cell

    Résumé : The aim of this talk is to present a study on cell deformation and cell movement by considering both the mechanical and biochemical properties of the cortical network of actin filaments and its concentration. Actin is a polymer that can exist either in filamentous form (F-actin) or in monometric form (G-actin) and the filamentous form is arranged in a paired helix of two protofilaments. By assuming that cell deformations are a result of the cortical actin dynamics in the cell cytoskeleton, we consider a continuum mathematical model that couples the mechanics of the network of actin filaments with its bio-chemical dynamics. Numerical treatment of the model is carried out using the moving grid finite element method. Furthermore, by assuming slow deformations of the cell, we use linear stability theory to validate the numerical simulation results close to bifurcation points. Far from bifurcation points, we show that the mathematical model is able to describe the complex cell deformations typically observed in experimental results. Our numerical results illustrate cell expansion, cell contraction, cell translation and cell relocation as well as cell protrusions. In all these results, the contractile tonicity formed by the association of actin filaments to the myosin II motor proteins is identified as a key bifurcation parameter.



    This work is in collaboration with Dr Uduak Z. George at North Carolina State University, US and Dr Angelique Stephanou from TIMC, Grenoble. France.

    Contact: Jocelyn Etienne

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


  • Monday 4 May 2015 14:00-15:00 - Maude Gerbaix - Centre National d’Etudes Spatiales INSERM U1059 Laboratiore de Biologie du Tissu Osseux, Saint-Étienne

    Effects Of Mechanical Loading And Gravity On Bone Tissue

    Résumé : From the beginning of life on earth, gravity and mechanical loading have shaped skeleton from cellular to biological function and modeling activity. Skeletal elements are made of a mineralized matrix covered by several types of cells which are responsible of its remodeling.
    The skeleton is a tissue which continuously renews itself. The remodeling process follows mechanical stress to prevent accumulation of fatigue damage, to repair micro fractures, and to participate in metabolic functions such as calcium homeostasis. However, the mechanisms of skeleton adaptation to mechanical loading is not fully understood. Among several models of reduced mechanical-loading, spaceflight provided a good instrument to study gravity-related mechanical loading effects on bone. Russian spaceflight onboarding rodent was resumed by the Bion-M1 satellite (April 19-Mai 19 2013) offering a unique opportunity to investigate the effects of gravity on bone tissue in mice. During this presentation, we will first review the actual understanding of the mechanical stress effect on bone. Then, we will expose the first results of Bion M1 mice skeleton study.



    contact: Aurélien Gourrier

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


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  • 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


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