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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 6 June 2016 14:00-15:30 - Raphaël JEANNERET - University of Warwick, UK

    Low Reynolds Number Dynamics of Boundary Driven and “Activated” Microparticles

    Résumé : In this talk, I will present the results of 2 different experimental projects, both dealing with the dynamics of micron-sized particles at low Reynolds number. The first part will be focused on biomixing at the microscale. This thematic tries to rationalize to which extent motile organisms stir their local environment. If it is generally accepted that macroscopic to mesoscopic organisms do have a big influence on the mixing of oceans, estimation of this effect by micron-sized swimmers is still scarce. Trying to bring experimental estimate to this field, we investigated the dynamics of tracers in bath of swimming microorganisms, more particularly the model swimmer Chlamydomonas Reinhardtii, a 10μm-sized fresh-water unicellular alga. By combining 3 different experiments we have shown that the tracers exhibit enhanced diffusion an order of magnitude bigger than previously thought (corresponding, at low swimmer concentration of φ ≈ 0.5%, to ∼ 40 times the thermal diffusion).
    In the second part of the talk, I will focus on a very fundamental aspect of low Reynolds number hydrodynamics: hydrodynamic reversibility. In brief, fluid particle trajectories of viscous flows have the property of being perfectly reversible upon reversal of the strain applied to the boundaries of the system. This property is a trivial consequence of the Stokes equation and has been astonishingly demonstrated experimentally by G.I. Taylor in the 1960s. Here we revisit this property by considering the dynamics of many non-Brownian droplets embedded in a liquid subjected to a periodic driving. We have shown that the dynamics of the particle assembly remains reversible (i.e. all particles do come back to their initial position after one cycle of the periodic driving) only below a certain threshold in the amplitude of driving. This transition appears to be a first order dynamical phase transition accompanied by a structural transition.



    contact: Philippe Peyla

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


  • Monday 13 June 2016 14:00-15:30 - Eduardo JAGLA - Centro Atómico Bariloche, Argentina

    Earthquake Statistics: Lessons from the Study of a Forest-Fire Model

    Résumé : The abundance of earthquakes follows a remarkable regularity: the number of earthquakes of magnitude M, is proportional to 10-bM, with a value of b close to 1. This is known as the Gutenberg-Richter law. The existence of this power-law dependence is obtained in models of rough surfaces in contact, however, the explanation of the origin of the actual value of b has been elusive.
    I will show that a statistical model originally proposed to study the statistics of forest fires can be interpreted also as describing the non-uniform stress state of a tectonic plate. By allowing the possibility of elements that ``retard’’ fire propagation, it is shown that secondary fires, analogous to the aftershocks in the seismic context, are generated. Moreover, this also produces a modification of the event statistics, and the appearance of a realistic value of b close to 1.



    contact: Ezequiel Ferrero and Jean-Louis Barrat

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


  • Monday 27 June 2016 14:00-15:30 - Nicolas BORGHI - Institut Jacques Monod, Paris

    Mechanotransduction from Cell Surface to Nucleus: Roles of E-Cadherin in Catenin Signaling

    Résumé : In multicellular organisms, cells generate and undergo mechanical forces that propagate through tissues. These forces may shape cells, tissues and organs, and also regulate genetic programs. We seek to elucidate the intimate mechanisms of the macromolecular complexes that transmit and transduce these mechanical cues within and between cells, and the cell functions affected by these cues.
    We are currently interested in the intercellular adhesion complex comprising E-cadherins and catenins in epithelial cells. E-cadherins are transmembrane proteins that form intercellular bonds between adjacent cells and recruit cytoskeletal linkers catenins in the cytoplasm. Remarkably, catenins are also regulators of gene transcription when in the nucleus, and this activity may be triggered by biochemical as well as mechanical cues during major morphogenetic processes and disease. The roles of E-cadherins in the mechanical induction of catenin-dependent genes is, however, poorly understood.
    I will present our recent advances in addressing this question, using genetically encoded biosensors and fluorescence microscopy.



    contact: Aurélie Dupont

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


  • Wednesday 29 June 2016 11:00-12:30 - Oskar PARIS - Institute of Physics, Montanuniversitaet Leoben, Austria

    Sorption-Induced Deformation of Nanoporous Materials: From Basic Experiments to Potential Applications

    Résumé : Advanced functional materials for sensing, actuation, catalysis, or energy storage are often based on highly porous solids with large surface area. It is long known that the interaction of a fluid guest phase with meso- and/or micropore walls leads to a fluid pressure dependent, non-monotonous deformation of the solid host material. This enables, in principle, mechanical actuation driven by sorption-induced deformation. The functionality of such actuators will critically depend on the specific fluid/solid interaction, but also on structural details of the material at different length scales. By using tailor-made materials with cylindrical mesopores on a highly ordered hexagonal pore lattice, adsorption-induced deformation can be studied in-situ at the mesopore level via the pore lattice strain obtained from small-angle X-ray scattering. A fundamental understanding of the basic mechanisms of deformation at this level already requires combining principles of fluid thermodynamics with solid mechanics in rather complex geometries. The prediction of the mechanical response of a macroscopic system to fluid sorption is even more challenging. Here we report recent experimental progress in this field for two examples based on mesoporous silica: biotemplated/bioinspired mesoporous bilayer systems, and monolithic samples with hierarchical porosity.



    contact: Benoit Coasne

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


  • Monday 11 July 2016 14:00-15:30 - Patrick Charbonneau - Duke University

    A Soft-Matter Perspective on Protein Crystallization

    Résumé : Crystallizing proteins is the bottleneck to systematically determining their structures. Identifying the solution conditions under which these macromolecules crystallize should be equivalent to determining their phase diagram, yet one typically resorts to combinatorial rather than physics-guided sampling to tackle this difficult problem. Although several soft matter-based ``patchy particle’’ models have been invoked to rationalize protein assembly, the interactions that drive protein crystallization are insufficiently characterized for these models to be of much practical use. As a proof of concept of their relevance we simulate solvated proteins to parameterize patchy models, and find the self-assembly phase diagram to agree with crystallization experiments. By generalizing these models, we explore the range of conditions over which crystal assembly is possible, providing guidelines for crystallizing some of the recalcitrant proteins.



    contact: Jean-Louis Barrat

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


  • Monday 5 September 2016 14:00-15:30 - Ana REWAKOWICZ - LadHyX, École polytechnique, Palaiseau, France

    The Concept of Design-Science in Art/Science Collaboration

    Résumé : My presentation will explore the design-science concept coined by Buckminster Fuller as a vehicle in the journey of art/science collaboration. Using examples of my artwork, I will reflect on the collaborative spirit that has to be nurtured and practiced in various processes of creation.
    As an artist, I worked for over a decade with inflatable objects exploring relations between temporal, portable architecture, the body and the environment. In contrast to the stable mass of monumental sculpture and architecture, my structures were air-filled, mobile and concerned with the places and people that activated them. In the last couple of years, through collaboration with scientists, my work has shifted into new forms of visual expression. Still concerned with issues of sustainability and technology as an opportunity for social transformation, my art engages in growing environmental complexities, with particular attention on water. The Mist Collector project I am developing together with Camille Duprat and Jean-Marc Chomaz focuses on the creation of an aesthetic experience that also intends to propose an innovative solution to world’s water shortage by means of harvesting fog.
    Striving for integrity of processes and ideas, I am equally influenced by the visionary works of Renaissance artists such as Leonardo da Vinci, as well as modern inventors like Buckminster Fuller, who fused an imaginative sensibility with technical invention. I see my art practice as a bridge-building and gap narrowing process between science and art.



    contact: Philippe Marmottant

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


  • Monday 12 September 2016 14:00-15:30 - Claire LYE - Dept. Physiology, Development and Neurosciences, Univ. Cambridge, GB

    Understanding the Role of Tissue-Scale Forces in Driving Shape Changes in Developing Animals: Mechanical Coupling between Endoderm Invagination and Axis Extension in Drosophila

    Résumé : Developing animal tissues achieve their functional shapes through dramatic morphogenetic movements, which are driven by the behaviours of the constituent cells. Morphogenesis has captured the imagination of scientists for decades, with the importance of mechanics for morphogenesis already recognised a century ago. To fully understand how morphogenesis is achieved requires considering both genetic and mechanical aspects and the interaction between them. I use the morphogenesis of fruit-fly (Drosophila) embryos as a model system in which to do this.
    How genetic programs generate cell-intrinsic forces to shape embryos is actively studied, but less so how tissue-scale physical forces impact morphogenesis. I will discuss the role of tissue-scale forces during Drosophila axis extension, also known as germband extension (GBE). Previous work in our lab had shown that cells elongate in the anteroposterior (AP) axis in the extending germband, suggesting that an extrinsic tensile force contributed to body axis extension.
    To identify the morphogenetic movements that could be the source of this extrinsic force, we temporally mapped gastrulation movements using light sheet microscopy to image whole Drosophila embryos. We found that endoderm invagination is synchronous with the onset of GBE. AP cell elongation is abolished in the absence of endoderm invagination. We used laser ablation to confirm that tension is increased in the AP orientation compared to the perpendicular orientation in the posterior germband close to the site of endoderm invagination. We propose that endoderm invagination is the source of the extrinsic tensile force contributing to germband extension. This highlights the importance of physical interactions between tissues during morphogenesis.



    contact: Jocelyn Étienne

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


  • Monday 26 September 2016 14:00-15:30 - Angélique Stéphanou - TIMC, CNRS-UGA, Grenoble

    An Integrated Computational Approach for the Design of a Virtual Tumour

    Résumé : The design of a patient-specific virtual tumour is an important step towards personalized medicine since the virtual tumour can be used to define the most adapted and efficient treatment protocol. However this requires to capture the description of many key events of tumour development, including angiogenesis, matrix remodelling, hypoxia, cell heterogeneity that will all influence the tumour growth kinetics and degree of tumour invasiveness. To that end, an integrated hybrid and multiscale approach has been developed based on data acquired on a preclinical mouse model as a proof of concept. Fluorescence imaging is exploited to build case-specific virtual tumours and to validate their spatiotemporal evolution. The validity of the model will be discussed as well as its potential to identify the best therapeutic strategy for each individual tumour case.



    contact: Jocelyn Etienne

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


  • Monday 3 October 2016 14:00-15:30 - Geoffroy AUBRY - Universität Konstanz, Germany

    Light Transport in Photonic Glasses

    Résumé : In disordered enough media, diffusion of waves can come to a halt: this is the so-called Anderson localization. It has been first observed in electronic systems (metal/insulator transition), then with ultra sound or cold atoms, but never for light in 3D. One reason for that could be that the studied samples were not disordered enough, in other words, did not scatter enough. Monodisperse photonic glasses are one way to achieve more scattering by using the resonant properties of the single scatterers. To better understand light transport in such materials, we present a model that combines the scattering properties of a concentrated interacting Mie-scatterer suspension embedded in a medium having a refractive index calculated by the energy-density coherent-potential approximation. The validity of the model is confirmed by already published and new experimental data in polystyrene and titania photonic glasses, as well as compared with numerical simulations using different ab-initio codes (Meep and MSTM).



    contact: Benjamin Cross

    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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