Conférences et séminaires

SIGMA Séminaire N. HOUMANI

Nesma Houmani — 2013-06-18T08:00:00Z

- 2013 / Conférences et séminaires, auto

Lucas Goehring (Max Planck Institute Goettingen)

Etienne Reyssat, Ramiro Godoy-Diana — 2013-06-21T09:00:00Z

Evolving crack patterns : mud cracks, columnar joints, and polygonal terrain

Contraction cracks can form captivating patterns, such as the artistic craquelure sometimes found in pottery glazes, to the cracks in dried mud, or the polygonal networks covering the polar regions of Earth and Mars. Two types are frequently encountered : those with irregular rectilinear patterns, such as that formed by an homogeneous slurry when dried (or cooled) uniformly, and more regular hexagonal patterns, such as those typified by columnar joints. Once cracks start to form in a thin contracting layer, they will sequentially break the layer into smaller and smaller pieces. A rectilinear crack pattern encodes information about the order of cracks, as later cracks tend to intersect with earlier cracks at right angles. In this manner they relieve the stresses perpendicular to the pre-existing crack. In a hexagonal pattern, in contrast, the angles between all cracks at a vertex are near 120°. In this presentation it will be shown how both types of pattern can arise from identical forces, and that a rectilinear, T-junction dominated pattern will develop into to a hexagonal pattern, with Y-junctions, if allowed to. The ordering of crack patterns are seen in a number of systems : columnar joints in starch and lava ; desiccation cracks in clays that are repeatedly wetted and dried ; cracks in eroding gypsum-cemented sand layers ; and the cracks in permafrost known as polygonal terrain. These patterns will each be briefly explored, in turn, and shown to obey the above principles of crack pattern evolution.

Pr Isabelle Gillaizeau - Université d'Orléans

Stellios Arseniyadis — 2013-06-21T09:00:00Z

Institut de Chimie Organique et Analytique "Enamide : un substrat de choix pour la synthèse d'hétérocycles" - 2013 / Conférences et séminaires, auto

Conférence de Emi Nagoshi

Serge Birman — 2013-06-21T09:00:00Z

Institute of Cell Biology, Université de Berne : "Fer2 loss-of-function as a new model of Parkinson's disease in Drosophila". Invitée par Serge Birman, Laboratoire de Neurobiologie. - 2013 / Conférences et séminaires, auto

Zoya Ignatova (Institute of Biochemistry and Biology, University of Potsdam, Germany)

Mathilde Reyssat — 2013-06-24T09:15:00Z

Non-uniform speed of translation : Stochastic fluctuations or programmed pausing

Translation of the genetic information from a nucleotide sequence into a functional protein is an essential biological process. The translation machinery, the ribosome, is a central player that translates the genetic information stored in the messenger RNA codon by codon. Multiple auxiliary factors with different molecular mass and concentration participate also in this process. They reach the ribosome solely by diffusion, which exerts a powerful selective force on the rate the ribosomes progress along mRNAs and consequently on the translation fidelity. We use cell-wide approaches to quantitatively assess the translation efficiency and ribosome occupancy with nucleotide resolution. Our data reveal that translation processes with non-uniform velocity including also some transient pauses which provide a kinetic window to synchronize translation of the genetic information with other cellular processes, including protein folding. Using predictive mathematical modeling we assess the alterations in translational behavior under stress. Different types of environmental stress have strictly different effect on translation fidelity.

Conférence ESPGG

2013-06-25T13:00:00Z

- 2013 / Conférences et séminaires, auto

Conférence ESPGG

, Fabrice Esnault — 2013-06-25T16:00:00Z

- 2013 / Conférences et séminaires, auto

Séminaire LCO

2013-06-26T16:00:00Z

- 2013 / Conférences et séminaires, auto

Séminaire JLP

Gerard Dreyfus — 2013-06-28T08:00:00Z

- 2013 / Conférences et séminaires, auto

Marc-Etienne Brachet (LPS, ENS)

Etienne Reyssat, Ramiro Godoy-Diana — 2013-06-28T09:00:00Z

Séminaires du laboratoire PMMH : consultez le programme

- 2013 / Conférences et séminaires, auto, PMMH

Raphaël Voituriez (LPTMC)

Mathilde Reyssat — 2013-07-01T09:15:00Z

- 2013 / Conférences et séminaires, auto, Gulliver

Séminaire LCO

2013-07-03T16:00:00Z

- 2013 / Conférences et séminaires, auto

Séminaire JLP

Gerard Dreyfus — 2013-07-05T07:30:00Z

- 2013 / Conférences et séminaires, auto

Stephan Herminghaus (Max Planck Gesellschaft)

Etienne Reyssat, Ramiro Godoy-Diana — 2013-07-05T09:00:00Z

Séminaires du laboratoire PMMH : consultez le programme

- 2013 / Conférences et séminaires, auto, PMMH

Pr Marek Chmielewski - Polish Academy of Sciences

Stellios Arseniyadis — 2013-07-05T09:00:00Z

Institute of Organic Chemistry "Stereoselective synthesis of ?-lactams via Kinugasa reaction and related compounds" - 2013 / Conférences et séminaires, auto

test 2

Emmanuel Dreyfus — 2013-07-08T05:30:00Z

test - 2013 / Conférences et séminaires, auto

test 3

2013-07-08T06:00:00Z

- 2013 / Conférences et séminaires, auto

test 4

Arsène Lupin, Emmanuel Dreyfus — 2013-07-08T06:00:00Z

- 2013 / Conférences et séminaires, auto

Séminaire LCO

2013-07-10T16:00:00Z

- 2013 / Conférences et séminaires, auto

Sergei Obukhov - University of Florida and Institut Charles Sadron, Strasbourg

Antoine Chateauminois — 2013-07-11T12:00:00Z

Nanofluidity of Polymer Melt : Two velocity hydrodynamics. - 2013 / Conférences et séminaires, auto

Roberto Zenit (UNAM, México)

Etienne Reyssat, Ramiro Godoy-Diana — 2013-07-12T09:00:00Z

Locomotion of microorganisms in complex fluids

The fundamental mechanisms of microorganism motility have been extensively studied in the past. Most previous work focused on cell locomotion in simple (Newtonian) fluids. However, in many cases of biological importance (including mammalian reproduction and bacterial infections), the fluids that surround the organisms are strongly non-Newtonian (so-called complex fluids), either because they have shear-dependent viscosities, or because they display an elastic response. These non-Newtonian effects challenge the most fundamental intuition in fluid mechanics, resulting in our incapacity to predict its implications in biological cell locomotion. In this talk, our on-going experimental investigation to quantify the effect of non-Newtonian behavior on the locomotion and fluid transport of microorganisms will be described. Several types of magnetic micro-robots were designed and built. These devices were actuated to swim or move in a variety of fluids : Newtonian, elastic with constant viscosity (Boger fluids) or inelastic with shear-thinning viscosity. We have found that, depending on the details of locomotion, the swimming performance can either be increased, decreased or remain unaffected by the non Newtonian nature of the liquid. Some key elements to understand the general effect of viscoelasticity and shear-thinning viscosity of the motility of microorganisms will be discussed.

Séminaire LCO

2013-07-17T16:00:00Z

- 2013 / Conférences et séminaires, auto