Séminaires


Séminaire MMC : Michel Louge « Statistical mechanics of hysteretic capillary phenomena: predictions of contact angle on rough surfaces and liquid retention in unsaturated porous media »

DATE : le Mardi 27 Juin prochain en salle 120 à 11H bâtiment 11E.

Intervenant : Michel Louge, de l’Université de Cornell,

Résumé :
We describe a statistical mechanics approach to hysteretic capillary phenomena with two examples: the retention of a liquid in an unsaturated porous medium; and the behavior of the triple gas-solid-liquid contact line on a rough surface. In both cases, random geometry of pores or cavities produces a frozen disorder that is subject to the collective release of capillary energy in first-order phase transitions. In unsaturated porous media, this may lead to Haines jumps. For the advancing and receding contact line, the analysis predicts six distinct regimes that include the classical Cassie-Baxter state, metastability, and other behavior observed in experiments

Publié dans Départements, Matière molle, Séminaires Matière Molle et Complexe | Commentaires fermés sur Séminaire MMC : Michel Louge « Statistical mechanics of hysteretic capillary phenomena: predictions of contact angle on rough surfaces and liquid retention in unsaturated porous media »

Séminaire exceptionnel de Meredith KUPINSKI : « Passive Imaging Polarimetry of Outdoor Scenes »

Date : Mercredi 12 juillet, 11h00,
Lieu:  télé-amphithéâtre immersif du PNRB-Beaulieu
Intervenante : Meredith KUPINSKI (Associate Research Professor at College of Optical Sciences, TUCSON, Univ. of Arizona, USA)

Abstract :
Our research vision is to establish quantifiable and reliable knowledge
concerning the utility of imaging polarimetry. This knowledge would have practical
value towards improving image analysis, informing technology investment, and
developing new mathematical models and information metrics. In atmospheric
sciences, polarimetry provides valuable constraints on optical and microphysical
properties of aerosols when a strict accuracy requirement of 0.5% uncertainty in
degree of linear polarization (DOLP) is met. To address this challenge the Jet
Propulsion Laboratory and University of Arizona (UA) developed and built the
Multi-angle Spectro-Polarimetric Imager (MSPI). Ground-MSPI is an 8-band
ultraviolet-visible-near infrared pushbroom camera, measuring polarization at
470, 660, and 865 nm. MSPI advances the state of the art in imaging
polarimeters by measuring intensity and a Stokes parameter simultaneously at a
single pixel. Because of its unprecedented accuracy, MSPI enables new scientific
applications of polarimetric imaging where previously the signal-to-noise or
alignment artifacts of earlier instruments provided poor results. MSPI images
show interesting trends in Angle of Linear Polarization (AoLP) images even when
the DoLP is less than 2%. In this talk GroundMSPI AoLP images are reported
with respect to dependency on surface texture, surface orientation, albedo, and
illumination conditions. Agreement with well-known principles of polarized light
scattering are illustrated, and several special cases are described.

Venez nombreux assister  à ce séminaire en imagerie polarimétrique passive, domaine dans lequel le College of Optical Sciences de Tucson fait figure de référence mondiale.

(Pour info, la salle de téléprésence immersive de l’ENSSAT a été réservée sur ce créneau pour permettre aux collègues Lannionais de suivre facilement le séminaire.)

Vous trouverez via ce lien le pdf de la biographie de Meredith KUPINSKI : View Fullscreen

Publié dans Actualités, Départements, Optique, Séminaires | Commentaires fermés sur Séminaire exceptionnel de Meredith KUPINSKI : « Passive Imaging Polarimetry of Outdoor Scenes »

Séminaire exceptionnel du Dr. Nobuyoshi MIYAMOTO : « Soft inorganic materials: the liquid crystalline colloids of inorganic nanosheets with ultra-high aspect ratio.

DATE : Lundi 26 Juin 2017, 14h00 en salle 120, bât.11E

Intervenant : Dr. Nobuyoshi MIYAMOTO
Associate Professor
Research Director of Materials and Energy Device Research Center of Fukuoka Institute of Technology (FIT-ME), Fujuoka, JAPAN

Abstract: Inorganic nanosheets, which are obtained by exfoliation of layered materials such as graphites, are unordinary colloidal particles as characterized by the ultimately anisotropic shape with uniform 1 nm thickness and lateral size of microns. Due to spontaneous orientation of the anisotropic particles, the colloids of nanosheets form liquid crystal phases, depending on the size and concentration. Combinations of liquid crystalline nanosheets with synthetic polymers, biopolymers, or living bacteria opens lead to variation of composite materials with regulated structures applicable. in many ways such as soft-actuators and sensors. The fundamentals of liquid crystalline nanosheets and our recent application researches will presented in this lecture

Publié dans Actualités, Départements, Matière molle, Séminaires | Commentaires fermés sur Séminaire exceptionnel du Dr. Nobuyoshi MIYAMOTO : « Soft inorganic materials: the liquid crystalline colloids of inorganic nanosheets with ultra-high aspect ratio.

Séminaire MMC : Anne MARTEL « Neutrons for Structural Biology: Emphasis on SANS »

DATE : 16 juin 2017, 14h00, salle 120

Intervenante : Anne MARTEL, Institut Laue Langevin, Grenoble

A range of neutron-using techniques are usefull for structural biology: namely, Small Angle Scattering, Laue Diffractometry, high- and low- resolution diffractometry, Reflectometry and Inelastic Scattering.  Each of them can be used to tacles specific aspect: such as the role of hydrogens in an enzymatic reaction, the relative position of partners in a macromolecular complex or the global dynamic of a system. This presentation will list them, insisting on their common features and their unique contribution to solve biological questions. The Small Angle Neutron Scattering will be further detailed, with several examples illustrating our recent developments in sample environment dedicated to biology.

 

Publié dans Départements, Matière molle, Séminaires Matière Molle et Complexe | Commentaires fermés sur Séminaire MMC : Anne MARTEL « Neutrons for Structural Biology: Emphasis on SANS »

Conférence Chen-li SUN : « On the locomotion of planktonic micro-organisms in a microfluidic environment »

DATE : le jeudi 15 juin de 11h00-11h45 dans la Salle des Thèses, Bât. 2A Université Rennes 1, Campus Beaulieu

Intervenante : Chen-li SUN
professeure au Department of Mechanical Engineering, National Taiwan University

Abstract

Planktonic micro-organisms play an important role in marine ecology, fishery, and the ocean carbon cycle. As the foundation of the oceanic food chain, phytoplankton and zooplankton form a complex food web, and their trophic interaction is vital to the prosperity of other marine life.
In this talk, I will demonstrate how microfluidic devices can be employed to gain a better understanding of marine ecosystem in a single-cell level.

Focusing on studying the locomotion of plankton K. veneficum (CCMP426), we design amicrocavity device to investigate the effects of different microflow conditions: stationary f/2-Si medium, steady flow, and oscillatory flow. After measuring the local flow field, we are able to determine the absolute and relative velocities of individual plankton cells, from which their rheotaxis can be derived. The probability density function, the expected value and the standard deviation are calculated in order to statistically represent the locomotion of the planktonic community. The experimental results show that when the plankton reside in stationary and homogeneous nutrient medium, the swimming velocity and the acceleration are 52.7±43.5 μ m s -1 and 878±820 μ m s -2 , respectively. In addition, K. veneficum is capable of maneuvering in a flow speed up to 150 μ m s -1 . Once the current is too strong, their locomotion is dominated by the flow.

Under the condition of oscillatory flow, K. veneficum exhibits positive rheotaxis. In the strong flow field region, planktonic cells can not directly cross the streamlines. Rather, they tend to cut through streamlines with small angle in order to reach the weak flow field region. The outcome of this study helps us clarify the interaction between the behavior of plankton and the microfluidic environment.

Biography

Chen-li Sun is Professor of Mechanical Engineering at National Taiwan University (NTU). She teaches in the areas of thermodynamics, heat transfer, energy engineering, two-phase flow, and thermal management for electronic devices. She is Visiting Professor at l’École normale supérieure de Rennes (Summer 2017) and l’Université Paris-Sud (Winter 2016). Prior to joining NTU, she was on the faculty of National Taiwan University of Science and Technology from 2003 to 2011. Prof. Sun received her B.S. degree from National Central University, Taiwan in 1994, M.S. from Stanford University in 1996, and Ph.D. from the University of California at Berkeley in 2002, all in Mechanical Engineering. In 2002-03, she was a postdoctoral researcher for Prof. Al P. Pisano in the Berkeley Sensor and Actuator Center (BSAC). Prof. Sun is the 2012 recipient of the Ta-You Wu Memorial Award, which recognizes young Taiwanese PIs dedicated to long-term outstanding research work. She is also the 2014 recipient of the Distinguished Young Scholar Award from the Society of Theoretical and Applied Mechanics. Dr. Sun’s research interest focuses on near-interface microscale transport phenomena and phase-change heat transfer in energy systems. Specifically, she is interested in exploring innovative measurement techniques for studying microscale transport in microfluidics.

Contacts:

martinus.werts@ens-rennes.fr
janine.emile@univ-rennes1.fr

 

 

 

 

 

 

 

 

 

 

Conférence
On the locomotion of planktonic micro-organisms
in a microfluidic environment
par
Chen-li SUN
professeure au
Department of Mechanical Engineering, National Taiwan University
le jeudi 15 juin de 11h00-11h45
dans la Salle des Thèses, Bât. 2A
Université Rennes 1, Campus Beaulieu
Abstract
Planktonic micro-organisms play an important role in marine ecology, fishery, and the ocean
carbon cycle. As the foundation of the oceanic food chain, phytoplankton and zooplankton form
a complex food web, and their trophic interaction is vital to the prosperity of other marine life.
In this talk, I will demonstrate how microfluidic devices can be employed to gain a better
understanding of marine ecosystem in a single-cell level.
Focusing on studying the locomotion of plankton
K. veneficum
(CCMP426), we design a
microcavity device to investigate the effects of different microflow conditions: stationary f/2-Si
medium, steady flow, and oscillatory flow. After measuring the local flow field, we are able to
determine the absolute and relative velocities of individual plankton cells, from which their
rheotaxis can be derived. The probability density function, the expected value and the standard
deviation are calculated in order to statistically represent the locomotion of the planktonic
community. The experimental results show that when the plankton reside in stationary and
homogeneous nutrient medium, the swimming velocity and the acceleration are 52.7±43.5
μ
m s
-1
and 878±820
μ
m s
-2
, respectively. In addition,
K. veneficum
is capable of maneuvering in a flow
speed up to 150
μ
m s
-1
. Once the current is too strong, their locomotion is dominated by the flow.
Under the condition of oscillatory flow,
K. veneficum
exhibits positive rheotaxis. In the strong
flow field region, planktonic cells can not directly cross the streamlines. Rather, they tend to cut
through streamlines with small angle in order to reach the weak flow field region. The outcome
of this study helps us clarify the interaction between the behavior of plankton and the
microfluidic environment.
Biography
Chen-li Sun is Professor of Mechanical Engineering at National Taiwan University (NTU). She
teaches in the areas of thermodynamics, heat transfer, energy engineering, two-phase flow, and
thermal management for electronic devices. She is Visiting Professor at l’École normale
supérieure de Rennes (Summer 2017) and l’Université Paris-Sud (Winter 2016). Prior to joining
NTU, she was on the faculty of National Taiwan University of Science and Technology from
2003 to 2011. Prof. Sun received her B.S. degree from National Central University, Taiwan in
1994, M.S. from Stanford University in 1996, and Ph.D. from the University of California at
Berkeley in 2002, all in Mechanical Engineering. In 2002-03, she was a postdoctoral researcher
for Prof. Al P. Pisano in the Berkeley Sensor and Actuator Center (BSAC). Prof. Sun is the 2012
recipient of the Ta-You Wu Memorial Award, which recognizes young Taiwanese PIs dedicated
to long-term outstanding research work. She is also the 2014 recipient of the Distinguished
Young Scholar Award from the Society of Theoretical and Applied Mechanics. Dr. Sun’s research
interest focuses on near-interface microscale transport phenomena and phase-change heat
transfer in energy systems. Specifically, she is interested in exploring innovative measurement
techniques for studying microscale transport in microfluidics.
Contact:
martinus.werts@ens-rennes.fr
,
janine.emile@univ-rennes1.fr

Publié dans Physique des milieux divisés et verres, Séminaires | Commentaires fermés sur Conférence Chen-li SUN : « On the locomotion of planktonic micro-organisms in a microfluidic environment »

Séminaire A. TURCHI : Density Functional Theory and Thermodynamics Applied to Complex Materials – Is there still a need for Ab Initio-aided alloy theory?

DATE : 19 juin 2017 – 11h00
              Pièce 007 – RdC du Bât 10B ISCR

Intervenant : A. Turchi, turchi1@llnl.gov
Lawrence Livermore National Laboratory, P. O. Box 808, Livermore, CA 94551, USA

 Ab initio methodologies provide, despite limitations that will be briefly commented on, fundamental insight on materials behavior and properties. This will be illustrated with a few ab initio-based predictions on phase stability, ordering trends, and thermodynamic properties. Examples will include the case of FeSi2, and of bcc-based transition metal alloys. In addition, ab initio output plays an important role in supplementing in two ways CALPHAD that is the most versatile and preferred method for assessing the thermodynamics of complex multi-component alloys: either by direct input of ab initio energetics in thermodynamic databases, or, more challenging, by assessing ab initio-based thermodynamics à la CALPHAD. These two applications will be briefly discussed in the context of phase diagram determination for selected transition metal and actinide-based alloys. Finally, a few comments on prospects in the alloy theory field, of critical importance for advancing our fundamental knowledge of materials performance, will conclude this presentation.

Publié dans Départements, Nanosciences, Séminaires Matériaux-Nanosciences | Commentaires fermés sur Séminaire A. TURCHI : Density Functional Theory and Thermodynamics Applied to Complex Materials – Is there still a need for Ab Initio-aided alloy theory?

Séminaire Etienne Mangaud : « Quantum dynamics of electron transfer in strongly coupled environments »

DATE : 13 juin 2017 à 10h00 en salle 120

Etienne MANGAUD,  Laboratoire de Chimie Physique, UMR8000, Université Paris-Sud, ORSAY

Experiments of time-resolved bidimensional spectroscopy carried out in complex
systems, such as photosynthetic systems (FMO)[1] or conjugated polymers[2], showed that quantum coherences amongst electronic excited states can persist for long times, comparable to the electron or excitation energy transfer times.
In order to investigate these phenomena from a theoretical point of view, one needs to
study the quantum motion of the nuclei and its influence onto the transfer. In the systems at stake, photo-induced electron transfer are studied in an oligothiophene-fullerene heterojunction[3] and a chromoprotein cryptochrome[4] as shown on Fig. 1 with a realistic environment.

Figure 1 Photo-induced electron transfer systems under study: On the left (Panel (a)), oligothiophene (OT4) –fullerene (C60) heterojunction. On the right (Panel (b)), chromoprotein cryptochrome with a flavin-adenosin-diphosphate (FAD) chromophore and a chain of three tryptophan molecules (W400, W377 and
W324)
For the heterojunction (Fig. 1 (a)), a reference Hamiltonian[5] describing a
donor-acceptor electronic system coupled to a bath of harmonic oscillators has been used. For the cryptochrome (Fig. 1 (b)), a three electronic states Hamiltonian has been parameterized using QM/MM trajectories based on constrained DFT (cDFT).[6,7]
Based on these parametrized Hamiltonians, time propagations have been carried out
using methods of dissipative quantum dynamics. However, since these systems exhibit a strong system-bath coupling that cannot be handled with traditional perturbation theory, one has to resort to exact computations such as the hierarchical equation of motion method.[8] A special care has also been taken to evaluate the quantum memory effects which prove to be significant in these systems.[9] To catch a glimpse of the physical movement at stake in the transfer, we perform a coordinate transformation used to define an effective mode[10], which is included into
the system, and which itself is coupled to a secondary bath. S H H 4 (a) (b)

As main results, we show and explain the dynamical behavior of various cases leading to an easy delocalization or to a trapping of the charge and assess the time scales of the transfer.
In the cases considered, the proposed methodology is well suited to analyze the subtle interplay between charge transfer and nuclear deformations, a prototype situation for many important processes in chemical and biological systems.
Acknowledgement: We acknowledge I. Burghardt for providing the heterojunction Hamiltonian data and F. Cailliez for fruitful discussions.

References:
[1] G. S. Engel et al, Nature, 2007, 446, 78
[2] E. Collini and G. Scholes, Science, 2009, 323, 369
[3] A. Chenel, E. Mangaud, I. Burghardt, C. Meier, M. Desouter-Lecomte, J. Chem. Phys., 2014, 140, 044104
[4] T. Firmino, E. Mangaud, F. Cailliez, A. Devolder, D. Mendive-Tapia, F. Gatti, C. Meier, M. Desouter-Lecomte, A. de la Lande, Phys. Chem. Chem. Phys., 2016, 18, 21442
[5] H. Tamura, I. Burghardt, and M. Tsukada, J. Phys. Chem. C, 2011, 115, 10205
[6] J. Řezáč, B. Lévy, I. Demachy, A. de la Lande, J. Chem. Theory Comput., 2012, 8,418
[7] Q. Wu, T. Van Voorhis, J. Chem. Theory Comput., 2006, 2,765
[8] Y. Tanimura, R. Kubo, J. Phys. Soc. Jpn., 1989, 58, 101
[9] H.-P. Breuer, E.M. Laine, J. Piilo and B. Vacchini, Rev. Mod. Phys., 2016, 88, 021003
[10] A. Pereverzev, E. R. Bittner, I. Burghardt, J. Chem. Phys., 1999, 131, 034104

Publié dans Physique Moléculaire, Séminaires de Physique Moléculaire | Commentaires fermés sur Séminaire Etienne Mangaud : « Quantum dynamics of electron transfer in strongly coupled environments »

Séminaire Théorie et Simulation : Laurent JOLY « Molecular views on surface-driven flows »

DATE : 23 Mai 2017 à 14h00
Salle 120 – IPR

Intervenant : Laurent JOLY / Institut Lumière Matière – Université Lyon 1

Surface-driven flows (also called osmotic flows) are generated at interfaces by various thermodynamic gradients (e.g. electric potential gradient: electro-osmosis, solute concentration gradient: diffusio-osmosis, temperature gradient: thermos-osmosis). They represent powerful tools to manipulate liquids in micro and nanofluidic systems, and play a key role in living systems, in sustainable energies, or in water treatment and desalination processes. Osmotic flows arise from the coupling between hydrodynamics and liquid-wall interactions in the nanometric vicinity of the interface, and yet standard descriptions are usually based on continuum models and liquid-wall interactions only. During this talk I will illustrate with recent work how molecular dynamics simulations can be used to investigate the mechanisms underlying surface-driven flow, and in particular to explore the role of interfacial hydrodynamics.

[1] L. Joly, F. Detcheverry, A.-L. Biance: “Anomalous zeta potential in foam films”, Phys. Rev. Lett. 113, 088301 (2014) [2] A. Barbosa de Lima, L. Joly, “Electro-osmosis at surfactant-laden liquid-gas interfaces: beyond standard models”, Soft Matter, Advance article (2017) [3] C. Lee, C. Cottin-Bizonne, R. Fulcrand, L. Joly, C. Ybert: “Nanoscale Dynamics versus Surface Interactions: What Dictates Osmotic Transport”, J. Phys. Chem. Lett. 8, 478 (2017) [4] L. Fu, S. Merabia, L. Joly, in preparation

Publié dans Départements, Nanosciences, Séminaires Matériaux-Nanosciences | Commentaires fermés sur Séminaire Théorie et Simulation : Laurent JOLY « Molecular views on surface-driven flows »

Séminaire MMC: Antoine Bérut « Gravisensing in plant cells is controlled by an active granular material »

DATE :  vendredi 12 mai 2017 à 11h salle 120

« Plants are able to sense gravity, so that the roots grow downward and the shoots upward. This gravitropism has been widely studied by biologists, and the commonly accepted hypothesis states that the gravity detection is mediated by the movement of starch-accumulating amyloplasts (statoliths), that sediment toward gravity in gravity sensing cells (statocytes), as show in figure a.
By performing microscopic observations of statocytes in wheat coleoptiles cuts, we have shown that a pile of statoliths flows easily, even in response to small inclination angles, contrary to what is expected for a classical granular material. This flowability ensures a high sensitivy for gravity detection, and might be explained by the agitation that statoliths undergo in plant cells. To identify the origin of the observed agitation, we have used a “biomimetic” microfluidic chambers filled with silica micro-particles of same dimension than statoliths in plant cells, but only submitted to thermal agitation (shown in figure b). The direct comparison of avalanche dynamics in the biological and physical systems suggests that the high flowability of statoliths cannot be explained by thermal motion, but is rather due to biological activity in plant cells such as cytoskeleton activity. This obervation is also supported by the difference between single trajectories of statoliths and silica particles at the top of a pile at rest: the amplitude of statoliths motion in wheat cell exceed by a factor ∼10 those of an inert particle of the same weight. Therefore gravisensing in plant cells relies on an active granular material. »

Publié dans Départements, Matière molle, Séminaires Matière Molle et Complexe | Commentaires fermés sur Séminaire MMC: Antoine Bérut « Gravisensing in plant cells is controlled by an active granular material »

Séminaire MMC : Julien Husson « Single-cell leukocyte mechanics: force generation, viscoelasticity, and rupture mechanics « 

DATE : Vendredi 28 Avril 2017 à 11h00 en salle 120

Julien Husson
Hydrodynamics laboratory (LadHyX), Ecole polytechnique, CNRS UMR 7646, Palaiseau, France
https://cellmechanics.jimdo.com/

Résumé :
Leukocytes are very soft cells that perform many diverse functions: they adhere, crawl, transmigrate, kill, phagocytose or interact with other cells. During their activation, leukocytes both generate mechanical forces and change their viscoelastic properties (i.e. they stiffen/soften, get more or less viscous). We have developed micropipette-based setups to quantify single-leukocyte mechanical properties and monitor them over time while a leukocytes gets activated by a relevant stimulus. We further quantify rupture properties of cell membrane, as these help us better understand cell structure and dynamics.

We use this approach in diverse contexts involving leukocytes: activation of T lymphocytes, phagocytosis of a target by a neutrophil, or transmigration of a lymphoblast across an endothelial monolayer. We perform microrheology experiments with a profile microindentation setup1,2, measure forces generated by T lymphocytes3,4, characterize cell-substrate adhesion5 or establish a rupture criteria for membrane rupture2,6(Figure 1). These mechanical measurements shed a new light on how cell mechanical properties evolve over a short period of time (seconds), how they adapt to the stiffness of their environment, and how intracellular signaling is involved.

 

Publié dans Départements, Matière molle, Séminaires Matière Molle et Complexe | Commentaires fermés sur Séminaire MMC : Julien Husson « Single-cell leukocyte mechanics: force generation, viscoelasticity, and rupture mechanics «