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animation:seminaires:2015:accueil [2015/10/05 13:08] – [...........] cicalugaanimation:seminaires:2015:accueil [2017/03/10 10:01] (Version actuelle) – [What's new under the Sun?] cicaluga
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 ====== Séminaires/Colloquium 2015 ====== ====== Séminaires/Colloquium 2015 ======
 +===== New wine into old wineskins: collisionless shocks in plasmas =====
 +{{:cbp_ens.jpeg?nolink&200 |}}**COLLOQUIUM Centre Blaise Pascal-Centre de Recherche Astrophysique de Lyon** \\
 +11 décembre 2015 de 14h à 15h - Salle de Conférence, 1 place Ecole - Monod, ENS Lyon, France \\
 +
 +**Antoine BRET**, Universidad Castilla La Mancha, ETSI Industriales, Espagne  \\
 +
 +
 +Organisateurs : \\ 
 +
 +  * Rolf Walder  (Centre de Recherche Astrophysique de Lyon, ENS de Lyon) \\
 +  * Cerasela Calugaru (Centre Blaise Pascal, ENS de Lyon, France) \\
 +
 +**(19 participants)**
 +
 +In 1808, Poisson realized that the conservation equations of a fluid through an interface offer 2 solutions: one continuous, when nothing changes, and another one, discontinuous, where there is a jump in density, velocity and pressure. Nearly 70 years later, Mach proved the second option was more than a mathematical curiosity, by providing the first picture of a shock wave moving through a fluid.
 +
 +Of course, the real world does not display any mathematical discontinuity. Since binary collisions are the only microscopic mechanisms capable of altering the fluid properties, the shock transition region in a fluid is a few mean-free-path thick.
 +
 +How is it then that the Earth bow shock in the solar wind has its front about 100 km thick, while the mean-free-path at the same location is about the Sun-Earth distance? It just happens that plasmas, that is, charged fluids, can sustain shock waves through purely collective electromagnetic means, even in the absence of binary collisions. The talk will review our current knowledge of these entities, focusing in particular on the way they can be formed, and their fulfillment of the Rankine-Hugoniot conditions.
 +\\
 +===== Modelling a Multienzymatic Complex : Theoretical Strategies =====
 +{{:cbp_ens.jpeg?nolink&200 |}}**COLLOQUIUM Centre Blaise Pascal-Laboratoires de Chimie** \\
 +30 octobre 2015 de 14h à 15h - Grande salle du CBP (LR6 C 023), ENS Lyon, France \\
 +
 +**Serge ANTONCZAK**, Institut de Chimie de Nice- UMR CNRS, Université de Nice-Sophia Antipolis, Nice, France \\
 +
 +
 +Organisateurs : \\ 
 +
 +  * Elise Dumont, Tangui Le Bahers (Laboratoire de Chimie, ENS de Lyon) \\
 +  * Cerasela Calugaru (Centre Blaise Pascal, ENS de Lyon, France) \\
 +
 +**(28 participants)**
 +
 +In each living system, the concentration of functional biological entities (e.g. proteins,
 +enzymes, peptides…) is incredibly high. Some transient complex-structures may appear and,
 +depending on the affinity the protagonists exhibit for each other, may subsist during
 +sufficiently long timescales that may lead to new functional systems called metabolons.
 +Experiments have demonstrated that some metabolons, lie at the vicinity of the membrane. \\
 +The product of an enzymatic reaction becoming the substrate for the neighbour
 +enzyme, it only has to “jump” from an active site to the next one, diminishing unnecessary
 +diffusion processes and loss of energy during solvation and desolvation processes, yielding to
 +an enhanced catalytic efficiency. Being able to precisely describe the overall architecture of
 +these macromolecular assemblies has then become a key to understand the underlying
 +biological mechanisms and for developing new therapeutic strategies.\\
 +So far, our investigations focused on an assembly composed by three enzymes
 +considered as key steps in the biosynthesis of anthocyanins and condensed tannins, namely
 +F3’H, DFR and LAR, in interaction with a model of membrane. In this presentation, will be
 +discussed the theoretical strategies carried out i) to characterise the enzymatic reaction
 +(QM/MM-MD simulations) ii) to define the way the substrates and the products enter in or are
 +released from the active site (brut force MD, Umbrella Sampling protocols…) iii) to design an
 +enzyme complex in interaction (ATTRACT docking protein/protein protocol) and to decipher
 +the interaction of this assembly with a model of membrane (OPM protocol).\\
 ===== Towards Climate-Dependent Sub-Grid-Scale Parameterizations in Atmospheric Models ===== ===== Towards Climate-Dependent Sub-Grid-Scale Parameterizations in Atmospheric Models =====
 {{:cbp_ens.jpeg?nolink&200 |}}**COLLOQUIUM Centre Blaise Pascal-Laboratoires de Physique** \\ {{:cbp_ens.jpeg?nolink&200 |}}**COLLOQUIUM Centre Blaise Pascal-Laboratoires de Physique** \\
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   * Antoine Venaille (Laboratoire de Physique, ENS de Lyon, France) \\   * Antoine Venaille (Laboratoire de Physique, ENS de Lyon, France) \\
   * Cerasela Calugaru (Centre Blaise Pascal, ENS de Lyon, France) \\   * Cerasela Calugaru (Centre Blaise Pascal, ENS de Lyon, France) \\
 +
 +**(52 participants)**
  
 Climate system models use a multitude of parameterization schemes for small-scale processes. These should respond to externally forced climate variability in an appropriate manner so as to reflect the response of the parameterized process to a changing climate. Indications are that they might not satisfy this condition to full satisfaction. The most attractive route to master the challenge of achieving such a behavior would be provided by theoretical understanding sufficiently deep to enable the à-priori design of climate-sensitive parameterization schemes.  An alternative path might be helpful when the parameter tuning involved in the development of a scheme is objective enough so that these parameters can be described as functions of the statistics of the climate system. Provided that the dynamics of the process yields a sufficiently smooth probability distribution, and that the external forcing is not too strong, the quasi-Gaussian fluctuation-dissipation theorem (qg-FDT, Risken 1984) might be a tool to predict from the statistics of a system (e.g. the atmosphere) how an objectively tuned parameterization should respond to external forcing (e.g. by anomalous sea-surface temperatures). First promising steps in following these strategies will be described in two parts of the talk. (1) The qg-FDT approach has been examined within the framework of a toy atmosphere, to be simulated by a low-order model (i.e. a toy atmosphere model) with realistic internal variability. At sufficiently weak (but yet realistic) forcing strength use of the qg-FDT is found to systematically improve the agreement between the responses of model and atmosphere, respectively (Achatz et al 2013). Encouraging results on the application of this technique to an increasingly complex atmospheric setting will be reported as well. (2) The application of stochastic-mode reduction (Majda et al 2003) to obtain local stochastic SGS schemes could be another interesting route. Starting from a high-resolution finite-difference discretization of the equations of a dynamical system, this approach is based on splitting the model variables into fast, small-scale and slow, large-scale modes by averaging over neighboring grid cells. After that, the fast modes are eliminated by applying a stochastic mode reduction procedure. The new parameterization has so far been applied to a one-dimensional turbulent-flow system (Burgers equation). It is shown to compare favorably to traditional approaches on SGS turbulence parameterizations (Dolaptchiev et al 2013a,b). Climate system models use a multitude of parameterization schemes for small-scale processes. These should respond to externally forced climate variability in an appropriate manner so as to reflect the response of the parameterized process to a changing climate. Indications are that they might not satisfy this condition to full satisfaction. The most attractive route to master the challenge of achieving such a behavior would be provided by theoretical understanding sufficiently deep to enable the à-priori design of climate-sensitive parameterization schemes.  An alternative path might be helpful when the parameter tuning involved in the development of a scheme is objective enough so that these parameters can be described as functions of the statistics of the climate system. Provided that the dynamics of the process yields a sufficiently smooth probability distribution, and that the external forcing is not too strong, the quasi-Gaussian fluctuation-dissipation theorem (qg-FDT, Risken 1984) might be a tool to predict from the statistics of a system (e.g. the atmosphere) how an objectively tuned parameterization should respond to external forcing (e.g. by anomalous sea-surface temperatures). First promising steps in following these strategies will be described in two parts of the talk. (1) The qg-FDT approach has been examined within the framework of a toy atmosphere, to be simulated by a low-order model (i.e. a toy atmosphere model) with realistic internal variability. At sufficiently weak (but yet realistic) forcing strength use of the qg-FDT is found to systematically improve the agreement between the responses of model and atmosphere, respectively (Achatz et al 2013). Encouraging results on the application of this technique to an increasingly complex atmospheric setting will be reported as well. (2) The application of stochastic-mode reduction (Majda et al 2003) to obtain local stochastic SGS schemes could be another interesting route. Starting from a high-resolution finite-difference discretization of the equations of a dynamical system, this approach is based on splitting the model variables into fast, small-scale and slow, large-scale modes by averaging over neighboring grid cells. After that, the fast modes are eliminated by applying a stochastic mode reduction procedure. The new parameterization has so far been applied to a one-dimensional turbulent-flow system (Burgers equation). It is shown to compare favorably to traditional approaches on SGS turbulence parameterizations (Dolaptchiev et al 2013a,b).
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 **Jacky EVEN** (Fonctions Optiques pour les Technologies de l’information & INSA de Rennes) \\   **Jacky EVEN** (Fonctions Optiques pour les Technologies de l’information & INSA de Rennes) \\  
 **Mikaël KEPENEKIAN** (Institut des Sciences Chimiques de Rennes & CNRS) \\  **Mikaël KEPENEKIAN** (Institut des Sciences Chimiques de Rennes & CNRS) \\ 
 +
 +**(27 participants)**
  
 Organisateurs : \\  Organisateurs : \\ 
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   * Julien Vovelle (Institut Camille Jordan, Université Claude Bernard Lyon 1)\\   * Julien Vovelle (Institut Camille Jordan, Université Claude Bernard Lyon 1)\\
   * Cerasela Calugaru (Centre Blaise Pascal, ENS de Lyon) \\   * Cerasela Calugaru (Centre Blaise Pascal, ENS de Lyon) \\
 +
 +**(31 participants)**
  
 On s’intéresse dans ce travail à l'équation des ondes avec potentiel q(x)u, sur un ouvert de R^d. On s’intéresse dans ce travail à l'équation des ondes avec potentiel q(x)u, sur un ouvert de R^d.
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   * Julien Vovelle (Institut Camille Jordan, Université Claude Bernard Lyon 1) \\   * Julien Vovelle (Institut Camille Jordan, Université Claude Bernard Lyon 1) \\
   * Cerasela Calugaru (Centre Blaise Pascal, ENS de Lyon) \\   * Cerasela Calugaru (Centre Blaise Pascal, ENS de Lyon) \\
 +
 +**(31 participants)**
  
 L'objet de la présentation est l'etude de modeles mathematiques et numeriques pour des ecoulements surfaces libres multi-regimes. Le caractere multi-regime (en terme de nombres adimensionnels tels que Froude et Reynolds) provient de la gamme des conditions aux limites basales considérées : de l'adherence au pure glissement en passant par les niveaux de friction intermediaires. Une derivation formelle de modeles "shallow" est menee de maniere standard (developpements asymptotiques) mais dans ce contexte multi-regimes. Les differentes formulations de modeles obtenus sont unifiees au sens ou elles representent a-priori l'ensemble de la gamme des regimes vises. Dans une seconde partie, nous nous interessons aux potentialites d'inversions des proprietes basales (topographie et parametrisation de la friction) au vu des donnees de surface (hauteur et/ou vitesse de la surface libre). Les investigations numeriques sont menees dans le cas fortement visqueux (Stokes surface libre), avec la methode du modele adjoint (a precision ajustable en fonction du niveau de bruit sur les donneees) et d'eventuelles minimisations de fonction cout mesurant l'ecart du modele aux donnees (assimilation variationnelle). Dans le cas 2D vertical, les echelles de variations minimales percues par le modele sont mises en evidence, ainsi que d'eventuels problemes de separation du couple (topographie, friction). Ces travaux sont issus de plusieurs etudes, menees en collaboration avec N. Martin, M. Boutounet et J.-P. Vila. L'objet de la présentation est l'etude de modeles mathematiques et numeriques pour des ecoulements surfaces libres multi-regimes. Le caractere multi-regime (en terme de nombres adimensionnels tels que Froude et Reynolds) provient de la gamme des conditions aux limites basales considérées : de l'adherence au pure glissement en passant par les niveaux de friction intermediaires. Une derivation formelle de modeles "shallow" est menee de maniere standard (developpements asymptotiques) mais dans ce contexte multi-regimes. Les differentes formulations de modeles obtenus sont unifiees au sens ou elles representent a-priori l'ensemble de la gamme des regimes vises. Dans une seconde partie, nous nous interessons aux potentialites d'inversions des proprietes basales (topographie et parametrisation de la friction) au vu des donnees de surface (hauteur et/ou vitesse de la surface libre). Les investigations numeriques sont menees dans le cas fortement visqueux (Stokes surface libre), avec la methode du modele adjoint (a precision ajustable en fonction du niveau de bruit sur les donneees) et d'eventuelles minimisations de fonction cout mesurant l'ecart du modele aux donnees (assimilation variationnelle). Dans le cas 2D vertical, les echelles de variations minimales percues par le modele sont mises en evidence, ainsi que d'eventuels problemes de separation du couple (topographie, friction). Ces travaux sont issus de plusieurs etudes, menees en collaboration avec N. Martin, M. Boutounet et J.-P. Vila.
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   * Annamaria Kiss (Laboratoires Joliot-Curie, ENS de Lyon, France) \\   * Annamaria Kiss (Laboratoires Joliot-Curie, ENS de Lyon, France) \\
   * Cerasela Calugaru (Centre Blaise Pascal, ENS de Lyon) \\   * Cerasela Calugaru (Centre Blaise Pascal, ENS de Lyon) \\
 +
 +**(39 participants)**
  
 Temporal networks are commonly used to represent systems where connections between elements are active only for restricted periods of time, such as telecommunication, neural signal processing, biochemical reaction and human social interaction networks. In this talk we introduce the framework of temporal motifs to study the mesoscale topological–temporal structure of temporal networks in which the events of nodes do not overlap in time. Temporal motifs are classes of similar event sequences, where the similarity refers not only to topology but also to the temporal order of the events. We provide a mapping from event sequences to coloured directed graphs that enables an efficient algorithm for identifying temporal motifs. We discuss some aspects of temporal motifs, including causality and null models, and present basic statistics of temporal motifs in a large mobile call network.\\  Temporal networks are commonly used to represent systems where connections between elements are active only for restricted periods of time, such as telecommunication, neural signal processing, biochemical reaction and human social interaction networks. In this talk we introduce the framework of temporal motifs to study the mesoscale topological–temporal structure of temporal networks in which the events of nodes do not overlap in time. Temporal motifs are classes of similar event sequences, where the similarity refers not only to topology but also to the temporal order of the events. We provide a mapping from event sequences to coloured directed graphs that enables an efficient algorithm for identifying temporal motifs. We discuss some aspects of temporal motifs, including causality and null models, and present basic statistics of temporal motifs in a large mobile call network.\\ 
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   * Stephane Labrosse, Caroline Fitoussi, Benoit Tauzin, Nicolas Coltice (Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement) \\   * Stephane Labrosse, Caroline Fitoussi, Benoit Tauzin, Nicolas Coltice (Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement) \\
   * Cerasela Calugaru (Centre Blaise Pascal, ENS de Lyon) \\   * Cerasela Calugaru (Centre Blaise Pascal, ENS de Lyon) \\
 +
 +**(30 participants)**
  
 La diversité des compositions chimiques des basaltes à la surface de la Terre suggère que les roches du manteau Terrestre sont hétérogènes. Si une partie de ces hétérogénéités peut être attribuée à des processus constants de différenciation et de recyclage, certaines signatures géochimiques indiquent la préservation de matériel primordial sur plusieurs milliards d'années. La diversité des compositions chimiques des basaltes à la surface de la Terre suggère que les roches du manteau Terrestre sont hétérogènes. Si une partie de ces hétérogénéités peut être attribuée à des processus constants de différenciation et de recyclage, certaines signatures géochimiques indiquent la préservation de matériel primordial sur plusieurs milliards d'années.
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   * Christian Perez et Jean-Yves L'Excellent (Laboratoire de l'Informatique du Parallélisme, ENS de Lyon, France) \\   * Christian Perez et Jean-Yves L'Excellent (Laboratoire de l'Informatique du Parallélisme, ENS de Lyon, France) \\
   * Cerasela Calugaru (Centre Blaise Pascal, ENS de Lyon, France) \\   * Cerasela Calugaru (Centre Blaise Pascal, ENS de Lyon, France) \\
 +
 +**(31 participants)**
  
 In order to design and operates the future reactor for nuclear fusion  In order to design and operates the future reactor for nuclear fusion 
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 good performance up to 1,835,008 threads (the complete Juqueen Blue  good performance up to 1,835,008 threads (the complete Juqueen Blue 
 Gene/Q at Jülich). Gene/Q at Jülich).
- 
 ===== What's new under the Sun? ===== ===== What's new under the Sun? =====
 {{:cbp_ens.jpeg?nolink&200 |}}**COLLOQUIUM Centre Blaise Pascal-Laboratoires de Physique** \\ {{:cbp_ens.jpeg?nolink&200 |}}**COLLOQUIUM Centre Blaise Pascal-Laboratoires de Physique** \\
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   * Antoine Venaille (Laboratoire de Physique, ENS de Lyon, France) \\   * Antoine Venaille (Laboratoire de Physique, ENS de Lyon, France) \\
   * Cerasela Calugaru (Centre Blaise Pascal, ENS de Lyon, France) \\   * Cerasela Calugaru (Centre Blaise Pascal, ENS de Lyon, France) \\
 +
 +**(52 participants)**
  
 We will discuss our recent progress to model in 3-D the solar global interior dynamics using the anelastic spherical harmonic (ASH) code. We will show We will discuss our recent progress to model in 3-D the solar global interior dynamics using the anelastic spherical harmonic (ASH) code. We will show
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 When comparing with asymptotic formulations and an adiabatic oscillation code we find a good overall agreement and confirm that  When comparing with asymptotic formulations and an adiabatic oscillation code we find a good overall agreement and confirm that 
 those waves are indeed gravity waves. We then discuss their properties and visibility at the surface and compare with recent observations. \\ those waves are indeed gravity waves. We then discuss their properties and visibility at the surface and compare with recent observations. \\
- 
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